40 CFR Part 1065 

Engine-Testing 

Procedures 

DRAFT Working 

Document

(LD Tier III NPRM changes in red, HD GHG DFR changes in brown, Non-Road HDIUT 

NPRM changes in gray) 

2/15/13 
Part 1065—ENGINE-TESTING PROCEDURES 

Subpart A—Applicability and General Provisions 

1065.1 Applicability. 

1065.2 Submitting information to EPA under this part. 

1065.5 Overview of this part 1065 and its relationship to the standard-setting part. 

1065.10 Other procedures. 

1065.12 Approval of alternate procedures. 

1065.15 Overview of procedures for laboratory and field testing. 

1065.20 Units of measure and overview of calculations. 

1065.25 Recordkeeping. 

Subpart B—Equipment Specifications 

1065.101 Overview. 

1065.110 Work inputs and outputs, accessory work, and operator demand. 

1065.120 Fuel properties and fuel temperature and pressure. 

1065.122 Engine cooling and lubrication. 

1065.125 Engine intake air. 

1065.127 Exhaust gas recirculation. 

1065.130 Engine exhaust. 

1065.140 Dilution for gaseous and PM constituents. 

1065.145 Gaseous and PM probes, transfer lines, and sampling system components. 

1065.150 Continuous sampling. 

1065.170 Batch sampling for gaseous and PM constituents. 

1065.190 PM-stabilization and weighing environments for gravimetric analysis. 

1065.195 PM-stabilization environment for in-situ analyzers. 

Subpart C—Measurement Instruments 

1065.201 Overview and general provisions. 

1065.202 Data updating, recording, and control. 

1065.205 Performance specifications for measurement instruments. 

MEASUREMENT OF ENGINE PARAMETERS AND AMBIENT CONDITIONS 

1065.210 Work input and output sensors. 

1065.215 Pressure transducers, temperature sensors, and dewpoint sensors. 

FLOW-RELATED MEASUREMENTS 

1065.220 Fuel flow meter. 

1065.225 Intake-air flow meter. 

1065.230 Raw exhaust flow meter. 

1065.240 Dilution air and diluted exhaust flow meters. 

1065.245 Sample flow meter for batch sampling. 

1065.248 Gas divider. 

CO AND CO2 MEASUREMENTS 

1065.250 Nondispersive infrared analyzer. 

HYDROCARBON MEASUREMENTS 

1065.260 Flame ionization detector. 

1065.265 Nonmethane cutter. 
1065.267 Gas chromatograph.

1065.269 Photoacoustic analyzer for methanol and ethanol.

NOx AND N2O MEASUREMENTS 

1065.270 Chemiluminescent detector. 

1065.272 Nondispersive ultraviolet analyzer. 

1065.275 N2O measurement devices. 

O2 MEASUREMENTS 

1065.280 Paramagnetic and magnetopneumatic O2 detection analyzers. 

AIR-TO-FUEL RATIO MEASUREMENTS 

1065.284 Zirconia (ZrO2) analyzer. 

PM MEASUREMENTS 

1065.290 PM gravimetric balance. 

1065.295 PM inertial balance for field-testing analysis. 

Subpart D—Calibrations and Verifications 

1065.301 Overview and general provisions. 

1065.303 Summary of required calibration and verifications 

1065.305 Verifications for accuracy, repeatability, and noise. 

1065.307 Linearity verification. 

1065.308 Continuous gas analyzer system-response and updating-recording verification—for gas 

analyzers not continuously compensated for other gas species. 

1065.309 Continuous gas analyzer system-response and updating-recording verification—for gas 

analyzers continuously compensated for other gas species. 

MEASUREMENT OF ENGINE PARAMETERS AND AMBIENT CONDITIONS 

1065.310 Torque calibration. 

1065.315 Pressure, temperature, and dewpoint calibration. 

FLOW-RELATED MEASUREMENTS 

1065.320 Fuel-flow calibration. 

1065.325 Intake-flow calibration. 

1065.330 Exhaust-flow calibration. 

1065.340 Diluted exhaust flow (CVS) calibration. 

1065.341 CVS, PFD, and batch sampler verification (propane check). 

1065.342 Sample dryer verification. 

1065.345 Vacuum-side leak verification. 

CO AND CO2 MEASUREMENTS 

1065.350 H2O interference verification for CO2 NDIR analyzers. 

1065.355 H2O and CO2 interference verification for CO NDIR analyzers. 

HYDROCARBON MEASUREMENTS 

1065.360 FID optimization and verification. 

1065.362 Non-stoichiometric raw exhaust FID O2 interference verification. 

1065.365 Nonmethane cutter penetration fractions.

1065.369 H2O, CO, and CO2 interference verification for photoacoustic alcohol analyzers.

NOx AND N2O MEASUREMENTS 

1065.370 CLD CO2 and H2O quench verification. 

1065.372 NDUV analyzer HC and H2O interference verification. 

1065.375 Interference verification for N2O analyzers. 
1065.376 Chiller NO2 penetration. 

1065.378 NO2-to-NO converter conversion verification. 

PM MEASUREMENTS 

1065.390 PM balance verifications and weighing process verification. 

1065.395 Inertial PM balance verifications. 

Subpart E—Engine Selection, Preparation, and Maintenance 

1065.401 Test engine selection. 

1065.405 Test engine preparation and maintenance. 

1065.410 Maintenance limits for stabilized test engines. 

1065.415 Durability demonstration. 

Subpart F—Performing an Emission Test in the Laboratory 

1065.501 Overview. 

1065.510 Engine mapping. 

1065.512 Duty cycle generation. 

1065.514 Cycle-validation criteria for operation over specific duty cycles.

1065.516 Sample system decontamination and preconditioning.

1065.518 Engine preconditioning.

1065.520 Pre-test verification procedures and pre-test data collection. 

1065.525 Engine starting, restarting, and shutdown. 

1065.526 Repeating of void modes or test intervals. 

1065.530 Emission test sequence. 

1065.545 Verification of proportional flow control for batch sampling. 

1065.546 Verification of minimum dilution ratio for PM batch sampling. 

1065.550 Gas analyzer range verification and drift verification. 

1065.590 PM sampling media (e.g., filters) preconditioning and tare weighing. 

1065.595 PM sample post-conditioning and total weighing. 

Subpart G—Calculations and Data Requirements 

1065.601 Overview. 

1065.602 Statistics. 

1065.610 Duty cycle generation. 

1065.630 1980 international gravity formula. 

1065.640 Flow meter calibration calculations. 

1065.642 SSV, CFV, and PDP molar flow rate calculations. 

1065.644 Vacuum-decay leak rate. 

1065.645 Amount of water in an ideal gas. 

1065.650 Emission calculations. 

1065.655 Chemical balances of fuel, intake air, and exhaust. 

1065.659 Removed water correction. 

1065.660 THC, NMHC, and CH4 determination. 

1065.665 THCE and NMHCE determination. 

1065.667 Dilution air background emission correction. 

1065.670 NOx intake-air humidity and temperature corrections. 

1065.672 Drift correction. 

Deleted: Validation 

Deleted: Validation 

Deleted: validation 

Deleted: validation
1065.675 CLD quench verification calculations. 

1065.690 Buoyancy correction for PM sample media. 

1065.695 Data requirements. 

Subpart H—Engine Fluids, Test Fuels, Analytical Gases and Other Calibration Standards 

1065.701 General requirements for test fuels. 

1065.703 Distillate diesel fuel. 

1065.705 Residual and intermediate residual fuel. 

1065.710 Gasoline. 

1065.715 Natural gas. 

1065.720 Liquefied petroleum gas.

1065.725 High-level ethanol-gasoline blends.

1065.740 Lubricants. 

1065.745 Coolants. 

1065.750 Analytical gases. 

1065.790 Mass standards. 

Subpart I—Testing with Oxygenated Fuels 

1065.801 Applicability. 

1065.805 Sampling system. 

1065.845 Response factor determination. 

1065.850 Calculations. 

Subpart J—Field Testing and Portable Emission Measurement Systems 

1065.901 Applicability. 

1065.905 General provisions. 

1065.910 PEMS auxiliary equipment for field testing. 

1065.915 PEMS instruments. 

1065.920 PEMS calibrations and verifications. 

1065.925 PEMS preparation for field testing. 

1065.930 Engine starting, restarting, and shutdown. 

1065.935 Emission test sequence for field testing. 

1065.940 Emission calculations. 

Subpart K—Definitions and Other Reference Information 

1065.1001 Definitions. 

1065.1005 Symbols, abbreviations, acronyms, and units of measure. 

1065.1010 Reference materials.

Subpart L—Methods for Unregulated and Special Pollutants

1065.1101 Applicability.

1065.1103 General provisions for SVOC measurement.

SEMI-VOLATILE ORGANIC COMPOUNDS

1065.1105 Sampling system design.

1065.1107 Sample media and sample system preparation; sampler assembly.

1065.1109 Post-test sampler disassembly and sample extraction.
1065.1111 Sample analysis.
PART 1065—ENGINE-TESTING PROCEDURES

Subpart A—Applicability and General Provisions 

§1065.1 Applicability. 

(a) This part describes the procedures that apply to testing we require for the following engines 

or for vehicles using the following engines: 

(1) Locomotives we regulate under 40 CFR part 1033. For earlier model years, manufacturers 

may use the test procedures in this part or those specified in 40 CFR part 92 according to 

§1065.10. 

(2) Model year 2010 and later heavy-duty highway engines we regulate under 40 CFR part 86. 

For earlier model years, manufacturers may use the test procedures in this part or those specified 

in 40 CFR part 86, subpart N, according to §1065.10. 

(3) Nonroad diesel engines we regulate under 40 CFR part 1039 and stationary diesel engines 

that are certified to the standards in 40 CFR part 1039 as specified in 40 CFR part 60, subpart 

IIII. For earlier model years, manufacturers may use the test procedures in this part or those 

specified in 40 CFR part 89 according to §1065.10. 

(4) Marine diesel engines we regulate under 40 CFR part 1042. For earlier model years, 

manufacturers may use the test procedures in this part or those specified in 40 CFR part 94 

according to §1065.10. 

(5) Marine spark-ignition engines we regulate under 40 CFR part 1045. For earlier model years, 

manufacturers may use the test procedures in this part or those specified in 40 CFR part 91 

according to §1065.10. 

(6) Large nonroad spark-ignition engines we regulate under 40 CFR part 1048, and stationary 

engines that are certified to the standards in 40 CFR part 1048 or as otherwise specified in 40 

CFR part 60, subpart JJJJ. 

(7) Vehicles we regulate under 40 CFR part 1051 (such as snowmobiles and off-highway 

motorcycles) based on engine testing. See 40 CFR part 1051, subpart F, for standards and 

procedures that are based on vehicle testing. 

(8) Small nonroad spark-ignition engines we regulate under 40 CFR part 1054 and stationary 

engines that are certified to the standards in 40 CFR part 1054 as specified in 40 CFR part 60, 

subpart JJJJ. For earlier model years, manufacturers may use the test procedures in this part or 

those specified in 40 CFR part 90 according to §1065.10. 

(b) The procedures of this part may apply to other types of engines, as described in this part and 

in the standard-setting part. 

(c) The term “you” means anyone performing testing under this part other than EPA. 

(1) This part is addressed primarily to manufacturers of engines, vehicles, equipment, and 

vessels, but it applies equally to anyone who does testing under this part for such manufacturers. 

(2) This part applies to any manufacturer or supplier of test equipment, instruments, supplies, or 

any other goods or services related to the procedures, requirements, recommendations, or options 

in this part. 

(d) Paragraph (a) of this section identifies the parts of the CFR that define emission standards 

and other requirements for particular types of engines. In this part, we refer to each of these 

other parts generically as the ''standard-setting part.'' For example, 40 CFR part 1051 is always 

the standard-setting part for snowmobiles. Note that while 40 CFR part 86 is the standard-setting 
part for heavy-duty highway engines, this refers specifically to 40 CFR part 86, subpart A, and to 

certain portions of 40 CFR part 86, subpart N, as described in 40 CFR 86.1301. 

(e) Unless we specify otherwise, the terms “procedures” and “test procedures” in this part 

include all aspects of engine testing, including the equipment specifications, calibrations, 

calculations, and other protocols and procedural specifications needed to measure emissions. 

(f) For vehicles, equipment, or vessels subject to this part and regulated under vehicle-based, 

equipment-based, or vessel-based standards, use good engineering judgment to interpret the term 

''engine'' in this part to include vehicles, equipment, or vessels, where appropriate. 

(g) For additional information regarding these test procedures, visit our Web site at 

www.epa.gov, and in particular http://www.epa.gov/nvfel/testing/regulations.htm. 

(h) This part describes procedures and specifications for measuring an engine’s exhaust 

emissions. While the measurements are geared toward engine-based measurements (in units of 

g/kW·hr), many of these provisions apply equally to vehicle-based measurements (in units of 

g/mile or g/kilometer). 40 CFR part 1066 describes the analogous procedures for vehicle-based 

emission measurements, and in many cases states that specific provisions of this part 1065 also 

apply for those vehicle-based measurements. Where material from this part 1065 applies for 

vehicle-based measurements under 40 CFR part 1066, it is sometimes necessary to include 

parenthetical statements in this part 1065 to properly cite secondary references that are different 

for vehicle-based testing. See 40 CFR part 1066 and the standard-setting part for additional 

information. 

§1065.2 Submitting information to EPA under this part. 

(a) You are responsible for statements and information in your applications for certification, 

requests for approved procedures, selective enforcement audits, laboratory audits, productionline test reports, field test reports, or any other statements you make to us related to this part 

1065. If you provide statements or information to someone for submission to EPA, you are 

responsible for these statements and information as if you had submitted them to EPA yourself. 

(b) In the standard-setting part and in 40 CFR 1068.101, we describe your obligation to report 

truthful and complete information and the consequences of failing to meet this obligation. See 

also 18 U.S.C. 1001 and 42 U.S.C. 7413(c)(2). This obligation applies whether you submit this 

information directly to EPA or through someone else. 

(c) We may void any certificates or approvals associated with a submission of information if we 

find that you intentionally submitted false, incomplete, or misleading information. For example, 

if we find that you intentionally submitted incomplete information to mislead EPA when 

requesting approval to use alternate test procedures, we may void the certificates for all engines 

families certified based on emission data collected using the alternate procedures. This would 

also apply if you ignore data from incomplete tests or from repeat tests with higher emission 

results. 

(d) We may require an authorized representative of your company to approve and sign the 

submission, and to certify that all of the information submitted is accurate and complete. This 

includes everyone who submits information, including manufacturers and others. 

(e) See 40 CFR 1068.10 for provisions related to confidential information. Note however that 

under 40 CFR 2.301, emission data is generally not eligible for confidential treatment. 

(f) Nothing in this part should be interpreted to limit our ability under Clean Air Act section 208 

(42 U.S.C. 7542) to verify that engines conform to the regulations. 

Deleted: how to measure emissions from vehicles 

that are subject to standards in g/mile or g/kilometer. 

Those vehicle testing provisions extensively 

reference portions of this part 1065. 
§1065.5 Overview of this part 1065 and its relationship to the standard-setting part. 

(a) This part specifies procedures that apply generally to testing various categories of engines. 

See the standard-setting part for directions in applying specific provisions in this part for a 

particular type of engine. Before using this part’s procedures, read the standard-setting part to 

answer at least the following questions: 

(1) What duty cycles must I use for laboratory testing? 

(2) Should I warm up the test engine before measuring emissions, or do I need to measure coldstart emissions during a warm-up segment of the duty cycle? 

(3) Which exhaust constituents do I need to measure? Measure all exhaust constituents that are 

subject to emission standards, any other exhaust constituents needed for calculating emission 

rates, and any additional exhaust constituents as specified in the standard-setting part. 

Alternatively, you may omit the measurement of N2O and CH4 for an engine, provided it is not 

subject to an N2O or CH4 emission standard. If you omit the measurement of N2O and CH4, you 

must provide other information and/or data that will give us a reasonable basis for estimating the 

engine’s emission rates. 

(4) Do any unique specifications apply for test fuels? 

(5) What maintenance steps may I take before or between tests on an emission-data engine? 

(6) Do any unique requirements apply to stabilizing emission levels on a new engine? 

(7) Do any unique requirements apply to test limits, such as ambient temperatures or pressures? 

(8) Is field testing required or allowed, and are there different emission standards or procedures 

that apply to field testing? 

(9) Are there any emission standards specified at particular engine-operating conditions or 

ambient conditions? 

(10) Do any unique requirements apply for durability testing? 

(b) The testing specifications in the standard-setting part may differ from the specifications in 

this part. In cases where it is not possible to comply with both the standard-setting part and this 

part, you must comply with the specifications in the standard-setting part. The standard-setting 

part may also allow you to deviate from the procedures of this part for other reasons. 

(c) The following table shows how this part divides testing specifications into subparts: 

Table 1 of §1065.5—Description of Part 1065 subparts. 

This subpart Describes these specifications or procedures 

Subpart A Applicability and general provisions. 

Subpart B Equipment for testing. 

Subpart C Measurement instruments for testing. 

Subpart D Calibration and performance verifications for measurement systems. 

Subpart E How to prepare engines for testing, including service accumulation. 

Subpart F How to run an emission test over a predetermined duty cycle. 

Subpart G Test procedure calculations. 

Subpart H Fuels, engine fluids, analytical gases, and other calibration standards. 

Subpart I Special procedures related to oxygenated fuels. 

Subpart J How to test with portable emission measurement systems (PEMS). 

§1065.10 Other procedures. 

(a) Your testing. The procedures in this part apply for all testing you do to show compliance 

with emission standards, with certain exceptions listed in this section. In some other sections in 
this part, we allow you to use other procedures (such as less precise or less accurate procedures) 

if they do not affect your ability to show that your engines comply with the applicable emission 

standards. This generally requires emission levels to be far enough below the applicable 

emission standards so that any errors caused by greater imprecision or inaccuracy do not affect 

your ability to state unconditionally that the engines meet all applicable emission standards. 

(b) Our testing. These procedures generally apply for testing that we do to determine if your 

engines comply with applicable emission standards. We may perform other testing as allowed 

by the Act. 

(c) Exceptions. We may allow or require you to use procedures other than those specified in this 

part in the following cases, which may apply to laboratory testing, field testing, or both. We 

intend to publicly announce when we allow or require such exceptions. All of the test 

procedures noted here as exceptions to the specified procedures are considered generically as 

"other procedures." Note that the terms "special procedures" and "alternate procedures" have 

specific meanings; "special procedures" are those allowed by §1065.10(c)(2) and "alternate 

procedures" are those allowed by §1065.10(c)(7). 

(1) The objective of the procedures in this part is to produce emission measurements equivalent 

to those that would result from measuring emissions during in-use operation using the same 

engine configuration as installed in a vehicle, equipment, or vessel. However, in unusual 

circumstances where these procedures may result in measurements that do not represent in-use 

operation, you must notify us if good engineering judgment indicates that the specified 

procedures cause unrepresentative emission measurements for your engines. Note that you need 

not notify us of unrepresentative aspects of the test procedure if measured emissions are 

equivalent to in-use emissions. This provision does not obligate you to pursue new information 

regarding the different ways your engine might operate in use, nor does it obligate you to collect 

any other in-use information to verify whether or not these test procedures are representative of 

your engine’s in-use operation. If you notify us of unrepresentative procedures under this 

paragraph (c)(1), we will cooperate with you to establish whether and how the procedures should 

be appropriately changed to result in more representative measurements. While the provisions of 

this paragraph (c)(1) allow us to be responsive to issues as they arise, we would generally work 

toward making these testing changes generally applicable through rulemaking. We will allow 

reasonable lead time for compliance with any resulting change in procedures. We will consider 

the following factors in determining the importance of pursuing changes to the procedures: 

(i) Whether supplemental emission standards or other requirements in the standard-setting part 

address the type of operation of concern or otherwise prevent inappropriate design strategies. 

(ii) Whether the unrepresentative aspect of the procedures affect your ability to show compliance 

with the applicable emission standards. 

(iii) The extent to which the established procedures require the use of emission-control 

technologies or strategies that are expected to ensure a comparable degree of emission control 

under the in-use operation that differs from the specified procedures. 

(2) You may request to use special procedures if your engine cannot be tested using the specified 

procedures. For example, this may apply if your engine cannot operate on the specified duty 

cycle. In this case, tell us in writing why you cannot satisfactorily test your engine using this 

part’s procedures and ask to use a different approach. We will approve your request if we 

determine that it would produce emission measurements that represent in-use operation and we 

determine that it can be used to show compliance with the requirements of the standard-setting 

part. Where we approve special procedures that differ substantially from the specified 
procedures, we may preclude you from participating in averaging, banking, and trading with the 

affected engine families. 

(3) In a given model year, you may use procedures required for later model year engines without 

request. If you upgrade your testing facility in stages, you may rely on a combination of 

procedures for current and later model year engines as long as you can ensure, using good 

engineering judgment, that the combination you use for testing does not affect your ability to 

show compliance with the applicable emission standards. 

(4) In a given model year, you may ask to use procedures allowed for earlier model year engines. 

We will approve this only if you show us that using the procedures allowed for earlier model 

years does not affect your ability to show compliance with the applicable emission standards. 

(5) You may ask to use emission data collected using other procedures, such as those of the 

California Air Resources Board or the International Organization for Standardization. We will 

approve this only if you show us that using these other procedures does not affect your ability to 

show compliance with the applicable emission standards. 

(6) During the 12 months following the effective date of any change in the provisions of this part 

1065, you may use data collected using procedures specified in the previously applicable version 

of this part 1065. This paragraph (c)(6) does not restrict the use of carryover certification data 

otherwise allowed by the standard-setting part. 

(7) You may request to use alternate procedures that are equivalent to the allowed procedures, or 

procedures that are more accurate or more precise than the allowed procedures. The following 

provisions apply to requests for alternate procedures: 

(i) Applications. Follow the instructions in §1065.12. 

(ii) Submission. Submit requests in writing to the Designated Compliance Officer. 

(iii) Notification. We may approve your request by telling you directly, or we may issue 

guidance announcing our approval of a specific alternate procedure, which would make 

additional requests for approval unnecessary. 

(d) If we require you to request approval to use other procedures under paragraph (c) of this 

section, you may not use them until we approve your request. 

§1065.12 Approval of alternate procedures. 

(a) To get approval for an alternate procedure under §1065.10(c), send the Designated 

Compliance Officer an initial written request describing the alternate procedure and why you 

believe it is equivalent to the specified procedure. Anyone may request alternate procedure 

approval. This means that an individual engine manufacturer may request to use an alternate 

procedure. This also means that an instrument manufacturer may request to have an instrument, 

equipment, or procedure approved as an alternate procedure to those specified in this part. We 

may approve your request based on this information alone, or, as described in this section, we 

may ask you to submit to us in writing supplemental information showing that your alternate 

procedure is consistently and reliably at least as accurate and repeatable as the specified 

procedure. 

(b) We may make our approval under this section conditional upon meeting other requirements 

or specifications. We may limit our approval, for example, to certain time frames, specific duty 

cycles, or specific emission standards. Based upon any supplemental information we receive 

after our initial approval, we may amend a previously approved alternate procedure to extend, 

limit, or discontinue its use. We intend to publicly announce alternate procedures that we 

approve. 
(c) Although we will make every effort to approve only alternate procedures that completely 

meet our requirements, we may revoke our approval of an alternate procedure if new information 

shows that it is significantly not equivalent to the specified procedure. If we do this, we will 

grant time to switch to testing using an allowed procedure, considering the following factors: 

(1) The cost, difficulty, and availability to switch to a procedure that we allow. 

(2) The degree to which the alternate procedure affects your ability to show that your engines 

comply with all applicable emission standards. 

(3) Any relevant factors considered in our initial approval. 

(d) If we do not approve your proposed alternate procedure based on the information in your 

initial request, we may ask you to send the following information to fully evaluate your request: 

(1) Theoretical basis. Give a brief technical description explaining why you believe the 

proposed alternate procedure should result in emission measurements equivalent to those using 

the specified procedure. You may include equations, figures, and references. You should 

consider the full range of parameters that may affect equivalence. For example, for a request to 

use a different NOx measurement procedure, you should theoretically relate the alternate 

detection principle to the specified detection principle over the expected concentration ranges for 

NO, NO2, and interference gases. For a request to use a different PM measurement procedure, 

you should explain the principles by which the alternate procedure quantifies particulate mass 

similarly to the specified procedures. 

(2) Technical description. Describe briefly any hardware or software needed to perform the 

alternate procedure. You may include dimensioned drawings, flowcharts, schematics, and 

component specifications. Explain any necessary calculations or other data manipulation. 

(3) Procedure execution. Describe briefly how to perform the alternate procedure and 

recommend a level of training an operator should have to achieve acceptable results. Summarize 

the installation, calibration, operation, and maintenance procedures in a step-by-step format. 

Describe how any calibration is performed using NIST-traceable standards or other similar 

standards we approve. Calibration must be specified by using known quantities and must not be 

specified as a comparison with other allowed procedures. 

(4) Data-collection techniques. Compare measured emission results using the proposed alternate 

procedure and the specified procedure, as follows: 

(i) Both procedures must be calibrated independently to NIST-traceable standards or to other 

similar standards we approve. 

(ii) Include measured emission results from all applicable duty cycles. Measured emission 

results should show that the test engine meets all applicable emission standards according to 

specified procedures. 

(iii) Use statistical methods to evaluate the emission measurements, such as those described in 

paragraph (e) of this section. 

(e) We may give you specific directions regarding methods for statistical analysis, or we may 

approve other methods that you propose. Absent any other directions from us, use a t-test and an 

F-test calculated according to §1065.602 to evaluate whether your proposed alternate procedure 

is equivalent to the specified procedure. We recommend that you consult a statistician if you are 

unfamiliar with these statistical tests. Perform the tests as follows: 

(1) Repeat measurements for all applicable duty cycles at least seven times for each procedure. 

You may use laboratory duty cycles to evaluate field-testing procedures. Be sure to include all 

available results to evaluate the precision and accuracy of the proposed alternate procedure, as 

described in §1065.2. 
(2) Demonstrate the accuracy of the proposed alternate procedure by showing that it passes a 

two-sided t-test. Use an unpaired t-test, unless you show that a paired t-test is appropriate under 

both of the following provisions: 

(i) For paired data, the population of the paired differences from which you sampled paired 

differences must be independent. That is, the probability of any given value of one paired 

difference is unchanged by knowledge of the value of another paired difference. For example, 

your paired data would violate this requirement if your series of paired differences showed a 

distinct increase or decrease that was dependent on the time at which they were sampled. 

(ii) For paired data, the population of paired differences from which you sampled the paired 

differences must have a normal (i.e., Gaussian) distribution. If the population of paired 

difference is not normally distributed, consult a statistician for a more appropriate statistical test, 

which may include transforming the data with a mathematical function or using some kind of 

non-parametric test. 

(3) Show that t is less than the critical t value, tcrit, tabulated in §1065.602, for the following 

confidence intervals: 

(i) 90 % for a proposed alternate procedure for laboratory testing. 

(ii) 95 % for a proposed alternate procedure for field testing. 

(4) Demonstrate the precision of the proposed alternate procedure by showing that it passes an Ftest. Use a set of at least seven samples from the reference procedure and a set of at least seven 

samples from the alternate procedure to perform an F-test. The sets must meet the following 

requirements: 

(i) Within each set, the values must be independent. That is, the probability of any given value 

in a set must be unchanged by knowledge of another value in that set. For example, your data 

would violate this requirement if a set showed a distinct increase or decrease that was dependent 

upon the time at which they were sampled. 

(ii) For each set, the population of values from which you sampled must have a normal (i.e., 

Gaussian) distribution. If the population of values is not normally distributed, consult a 

statistician for a more appropriate statistical test, which may include transforming the data with a 

mathematical function or using some kind of non-parametric test. 

(iii) The two sets must be independent of each other. That is, the probability of any given value 

in one set must be unchanged by knowledge of another value in the other set. For example, your 

data would violate this requirement if one value in a set showed a distinct increase or decrease 

that was dependent upon a value in the other set. Note that a trend of emission changes from an 

engine would not violate this requirement. 

(iv) If you collect paired data for the paired t-test in paragraph (e)(2) in this section, use caution 

when selecting sets from paired data for the F-test. If you do this, select sets that do not mask 

the precision of the measurement procedure. We recommend selecting such sets only from data 

collected using the same engine, measurement instruments, and test cycle. 

(5) Show that F is less than the critical F value, Fcrit, tabulated in §1065.602. If you have several 

F-test results from several sets of data, show that the mean F-test value is less than the mean 

critical F value for all the sets. Evaluate Fcrit, based on the following confidence intervals: 

(i) 90 % for a proposed alternate procedure for laboratory testing. 

(ii) 95 % for a proposed alternate procedure for field testing. 

§1065.15 Overview of procedures for laboratory and field testing. 

This section outlines the procedures to test engines that are subject to emission standards. 
(a) In the standard-setting part, we set brake-specific emission standards in g/(kW·hr) (or 

g/(hp·hr)), for the following constituents: 

(1) Total oxides of nitrogen, NOx. 

(2) Hydrocarbons (HC), which may be expressed in the following ways: 

(i) Total hydrocarbons, THC. 

(ii) Nonmethane hydrocarbons, NMHC, which results from subtracting methane (CH4) from 

THC. 

(iii) Total hydrocarbon-equivalent, THCE, which results from adjusting THC mathematically to 

be equivalent on a carbon-mass basis. 

(iv) Nonmethane hydrocarbon-equivalent, NMHCE, which results from adjusting NMHC 

mathematically to be equivalent on a carbon-mass basis. 

(3) Particulate mass, PM. 

(4) Carbon monoxide, CO.

(5) Carbon dioxide, CO2.

(6) Methane, CH4.

(7) Nitrous oxide, N2O.

(b) Note that some engines are not subject to standards for all the emission constituents identified 

in paragraph (a) of this section. Note also that the standard-setting part may include standards 

for pollutants not listed in paragraph (a) of this section.

(c) We generally set brake-specific emission standards over test intervals and/or duty cycles, as 

follows: 

(1) Engine operation. Testing may involve measuring emissions and work in a laboratory-type 

environment or in the field, as described in paragraph (f) of this section. For most laboratory 

testing, the engine is operated over one or more duty cycles specified in the standard-setting part. 

However, laboratory testing may also include non-duty cycle testing (such as simulation of field 

testing in a laboratory). For field testing, the engine is operated under normal in-use operation. 

The standard-setting part specifies how test intervals are defined for field testing. Refer to the 

definitions of “duty cycle” and “test interval” in §1065.1001. Note that a single duty cycle may 

have multiple test intervals and require weighting of results from multiple test intervals to 

calculate a composite brake-specific emissions value to compare to the standard. 

(2) Constituent determination. Determine the total mass of each constituent over a test interval 

by selecting from the following methods: 

(i) Continuous sampling. In continuous sampling, measure the constituent’s concentration 

continuously from raw or dilute exhaust. Multiply this concentration by the continuous (raw or 

dilute) flow rate at the emission sampling location to determine the constituent’s flow rate. Sum 

the constituent’s flow rate continuously over the test interval. This sum is the total mass of the 

emitted constituent. 

(ii) Batch sampling. In batch sampling, continuously extract and store a sample of raw or dilute 

exhaust for later measurement. Extract a sample proportional to the raw or dilute exhaust flow 

rate. You may extract and store a proportional sample of exhaust in an appropriate container, 

such as a bag, and then measure HC, CO, and NOx concentrations in the container after the test 

interval. You may deposit PM from proportionally extracted exhaust onto an appropriate 

substrate, such as a filter. In this case, divide the PM by the amount of filtered exhaust to 

calculate the PM concentration. Multiply batch sampled concentrations by the total (raw or 

dilute) flow from which it was extracted during the test interval. This product is the total mass of 

the emitted constituent. 
(iii) Combined sampling. You may use continuous and batch sampling simultaneously during a 

test interval, as follows: 

(A) You may use continuous sampling for some constituents and batch sampling for others. 

(B) You may use continuous and batch sampling for a single constituent, with one being a 

redundant measurement. See §1065.201 for more information on redundant measurements. 

(3) Work determination. Determine work over a test interval by one of the following methods: 

(i) Speed and torque. Synchronously multiply speed and brake torque to calculate instantaneous 

values for engine brake power. Sum engine brake power over a test interval to determine total 

work. 

(ii) Fuel consumed and brake-specific fuel consumption. Directly measure fuel consumed or 

calculate it with chemical balances of the fuel, intake air, and exhaust. To calculate fuel 

consumed by a chemical balance, you must also measure either intake-air flow rate or exhaust 

flow rate. Divide the fuel consumed during a test interval by the brake-specific fuel consumption 

to determine work over the test interval. For laboratory testing, calculate the brake-specific fuel 

consumption using fuel consumed and speed and torque over a test interval. For field testing, 

refer to the standard-setting part and §1065.915 for selecting an appropriate value for brakespecific fuel consumption. 

(d) Refer to §1065.650 for calculations to determine brake-specific emissions. 

(e) The following figure illustrates the allowed measurement configurations described in this part 

1065: 
Figure 1 of §1065.15—Default test procedures and other specified procedures. 

Power

Continuous Fuel

& BSFC 

Torque

& Speed 

Total Emissions

Batch 

Constant

Dilution Ratio

Partial Flow 

Dilute 

Varying

Dilution Ratio

Full Flow 

Brake- specific Emissions for

Transient Duty Cycle Testing

Emissions Rate Total Work

Raw Gaseous 

Default procedures

Other specified procedures

Alternate procedure

approval required

Alternate procedure

approval required for PM

Power

Continuous Fuel

& BSFC 

Torque

& Speed 

Total Emissions

Batch 

Constant

Dilution Ratio

Partial Flow 

Dilute 

Varying

Dilution Ratio

Full Flow 

Brake- specific Emissions for

Transient Duty Cycle Testing

Emissions Rate Total Work

Raw Gaseous 

Default procedures

Other specified procedures

Alternate procedure 

approval required for PM

Power

Continuous Fuel

& BSFC 

Torque

& Speed 

Total Emissions

Batch 

Constant

Dilution Ratio

Partial Flow 

Dilute 

Varying

Dilution Ratio

Full Flow 

Brake- specific Emissions for

Transient Duty Cycle Testing

Emissions Rate Total Work

Raw Gaseous 

Default procedures

Other specified procedures

Alternate procedure

approval required

Alternate procedure

approval required for PM

Power

Continuous Fuel

& BSFC 

Torque

& Speed 

Total Emissions

Batch 

Constant

Dilution Ratio

Partial Flow 

Dilute 

Varying

Dilution Ratio

Full Flow 

Brake- specific Emissions for

Transient Duty Cycle Testing

Emissions Rate Total Work

Raw Gaseous 

Default procedures

Other specified procedures

Alternate procedure 

approval required for PM

Power

Continuous

Raw Gaseous 

Fuel

& BSFC 

Torque

& Speed 

Total Emissions

Batch 

Constant

Dilution Ratio

Partial Flow 

Dilute 

Varying

Dilution Ratio

Full Flow 

Brake-specific Emissions for

Steady-state Duty Cycle Testing

Emissions Rate Total Work

Default procedures

Other specified procedures

Alternate procedure

approval required

Power

Continuous

Raw Gaseous 

Fuel

& BSFC 

Torque

& Speed 

Total Emissions

Batch 

Constant

Dilution Ratio

Partial Flow 

Dilute 

Varying

Dilution Ratio

Full Flow 

Brake-specific Emissions for

Steady-state Duty Cycle Testing

Emissions Rate Total Work

Default procedures

Other specified procedures

Power

Continuous

Raw Gaseous 

Fuel

& BSFC 

Torque

& Speed 

Total Emissions

Batch 

Constant

Dilution Ratio

Partial Flow 

Dilute 

Varying

Dilution Ratio

Full Flow 

Brake-specific Emissions for

Steady-state Duty Cycle Testing

Emissions Rate Total Work

Default procedures

Other specified procedures

Alternate procedure

approval required

Power

Continuous

Raw Gaseous 

Fuel

& BSFC 

Torque

& Speed 

Total Emissions

Batch 

Constant

Dilution Ratio

Partial Flow 

Dilute 

Varying

Dilution Ratio

Full Flow 

Brake-specific Emissions for

Steady-state Duty Cycle Testing

Emissions Rate Total Work

Default procedures

Other specified procedures

Power

Continuous Fuel

& BSFC 

Torque

& Speed 

Total Emissions

Batch 

Constant

Dilution Ratio

Partial Flow 

Dilute 

Varying

Dilution Ratio

Full Flow 

Brake- specific Emissions for

Field Testing

Emissions Rate Total Work

Raw Gaseous 

Default procedures

Other specified procedures

Alternate procedure

approval required

Power

Continuous Fuel

& BSFC 

Torque

& Speed 

Total Emissions

Batch 

Constant

Dilution Ratio

Partial Flow 

Dilute 

Varying

Dilution Ratio

Full Flow 

Brake- specific Emissions for

Field Testing

Emissions Rate Total Work

Raw Gaseous 

Default procedures

Other specified procedures

Power

Continuous Fuel

& BSFC 

Torque

& Speed 

Total Emissions

Batch 

Constant

Dilution Ratio

Partial Flow 

Dilute 

Varying

Dilution Ratio

Full Flow 

Brake- specific Emissions for

Field Testing

Emissions Rate Total Work

Raw Gaseous 

Default procedures

Other specified procedures

Alternate procedure

approval required

Power

Continuous Fuel

& BSFC 

Torque

& Speed 

Total Emissions

Batch 

Constant

Dilution Ratio

Partial Flow 

Dilute 

Varying

Dilution Ratio

Full Flow 

Brake- specific Emissions for

Field Testing

Emissions Rate Total Work

Raw Gaseous 

Default procedures

Other specified procedures
(f) This part 1065 describes how to test engines in a laboratory-type environment or in the field. 

(1) This affects test intervals and duty cycles as follows: 

(i) For laboratory testing, you generally determine brake-specific emissions for duty-cycle testing 

by using an engine dynamometer in a laboratory or other environment. This typically consists of 

one or more test intervals, each defined by a duty cycle, which is a sequence of modes, speeds, 

and/or torques (or powers) that an engine must follow. If the standard-setting part allows it, you 

may also simulate field testing with an engine dynamometer in a laboratory or other 

environment. 

(ii) Field testing consists of normal in-use engine operation while an engine is installed in a 

vehicle, equipment, or vessel rather than following a specific engine duty cycle. The standardsetting part specifies how test intervals are defined for field testing. 

(2) The type of testing may also affect what test equipment may be used. You may use “labgrade” test equipment for any testing. The term “lab-grade” refers to equipment that fully 

conforms to the applicable specifications of this part. For some testing you may alternatively 

used “field-grade” equipment. The term “field-grade” refers to equipment that fully conforms to 

the applicable specifications of subpart J of this part, but does not fully conform to other 

specifications of this part. You may use “field-grade” equipment for field testing. We also 

specify in this part and in the standard-setting parts certain cases in which you may use “fieldgrade” equipment for testing in a laboratory-type environment. (Note: Although “field-grade” 

equipment is generally more portable than “lab-grade” test equipment, portability is not relevant 

to whether equipment is considered to be “field-grade” or “lab-grade”.) 

§1065.20 Units of measure and overview of calculations. 

(a) System of units. The procedures in this part generally follow the International System of 

Units (SI), as detailed in NIST Special Publication 811, which we incorporate by reference in 

§1065.1010. The following exceptions apply: 

(1) We designate angular speed, fn, of an engine’s crankshaft in revolutions per minute (r/min), 

rather than the SI unit of radians per second (rad/s). This is based on the commonplace use of 

r/min in many engine dynamometer laboratories. 

(2) We designate brake-specific emissions in grams per kilowatt-hour (g/(kW·hr)), rather than 

the SI unit of grams per megajoule (g/MJ). In addition, we use the symbol hr to identify hour, 

rather than the SI convention of using h. This is based on the fact that engines are generally 

subject to emission standards expressed in g/kW·hr. If we specify engine standards in grams per 

horsepowerhour (g/(hp·hr)) in the standard-setting part, convert units as specified in paragraph 

(d) of this section. 

(3) We designate temperatures in units of degrees Celsius (°C) unless a calculation requires an 

absolute temperature. In that case, we designate temperatures in units of Kelvin (K). For 

conversion purposes throughout this part, 0 °C equals 273.15 K. Note that calculations that 

multiply or divided by temperature always use absolute temperature.

(b) Concentrations. This part does not rely on amounts expressed in parts per million. Rather, 

we express such amounts in the following SI units: 

(1) For ideal gases, mol/mol, formerly ppm (volume). 

(2) For all substances, cm3

/m3, formerly ppm (volume). 

(3) For all substances, mg/kg, formerly ppm (mass). 

Deleted: or similar units
(c) Absolute pressure. Measure absolute pressure directly or calculate it as the sum of 

atmospheric pressure plus a differential pressure that is referenced to atmospheric pressure. Note 

that calculations that multiply or divided by pressure always use absolute temperature.

(d) Units conversion. Use the following conventions to convert units: 

(1) Testing. You may record values and perform calculations with other units. For testing with 

equipment that involves other units, use the conversion factors from NIST Special Publication 

811, as described in paragraph (a) of this section. 

(2) Humidity. In this part, we identify humidity levels by specifying dewpoint, which is the 

temperature at which pure water begins to condense out of air. Use humidity conversions as 

described in §1065.645. 

(3) Emission standards. If your standard is in g/(hp·hr) units, convert kW to hp before any 

rounding by using the conversion factor of 1 hp (550 ft·lbf/s) = 0.7456999 kW. Round the final 

value for comparison to the applicable standard. 

(e) Rounding. You are required to round certain final values, such as emission values. You may 

round intermediate values when transferring data as long as you maintain at least six significant 

digits (which requires more than six decimal places for values less than 0.1), or all significant 

digits if fewer than six digits are available. Unless the standard-setting part specifies otherwise, 

do not round other intermediate values. Round values to the number of significant digits 

necessary to match the number of decimal places of the applicable standard or specification as 

described in this paragraph (e). Note that specifications expressed as percentages have infinite 

precision (as described in paragraph (e)(7) of this section). Use the following rounding 

convention, which is consistent with ASTM E29 and NIST SP 811: 

(1) If the first (left-most) digit to be removed is less than five, remove all the appropriate digits 

without changing the digits that remain. For example, 3.141593 rounded to the second decimal 

place is 3.14. 

(2) If the first digit to be removed is greater than five, remove all the appropriate digits and 

increase the lowest-value remaining digit by one. For example, 3.141593 rounded to the fourth 

decimal place is 3.1416. 

(3) If the first digit to be removed is five with at least one additional non-zero digit following the 

five, remove all the appropriate digits and increase the lowest-value remaining digit by one. For 

example, 3.141593 rounded to the third decimal place is 3.142. 

(4) If the first digit to be removed is five with no additional non-zero digits following the five, 

remove all the appropriate digits, increase the lowest-value remaining digit by one if it is odd and 

leave it unchanged if it is even. For example, 1.75 and 1.750 rounded to the first decimal place 

are 1.8; while 1.85 and 1.850 rounded to the first decimal place are also 1.8. Note that this 

rounding procedure will always result in an even number for the lowest-value digit. 

(5) This paragraph (e)(5) applies if the regulation specifies rounding to an increment other than 

decimal places or powers of ten (to the nearest 0.01, 0.1, 1, 10, 100, etc.). To round numbers for 

these special cases, divide the quantity by the specified rounding increment. Round the result to 

the nearest whole number as described in paragraphs (e)(1) through (4) of this section. Multiply 

the rounded number by the specified rounding increment. This value is the desired result. For 

example, to round 0.90 to the nearest 0.2, divide 0.90 by 0.2 to get a result of 4.5, which rounds 

to 4. Multiplying 4 by 0.2 gives 0.8, which is the result of rounding 0.90 to the nearest 0.2. 

(6) The following tables further illustrate the rounding procedures specified in this paragraph (e): 
Quantity 

Rounding Increment 

10 1 0.1 0.01 

3.141593 0 3 3.1 3.14 

123,456.789 123,460 123,457 123,456.8 123,456.79 

5.500 10 6 5.5 5.50 

4.500 0 4 4.5 4.50 

Quantity 

Rounding Increment 

25 3 0.5 0.02 

229.267 225 228 229.5 229.26 

62.500 50 63 62.5 62.50 

87.500 100 87 87.5 87.50 

7.500 0 6 7.5 7.50 

(7) This paragraph (e)(7) applies where we specify a limit or tolerance as some percentage of 

another value (such as ±2 % of a maximum concentration). You may show compliance with 

such specifications either by applying the percentage to the total value to calculate an absolute 

limit, or by converting the absolute value to a percentage by dividing it by the total value. 

(i) Do not round either value (the absolute limit or the calculated percentage), except as specified 

in paragraph (e)(7)(ii) of this section. For example, assume we specify that an analyzer must 

have a repeatability of ±1 % of the maximum concentration or better, the maximum 

concentration is 1059 ppm, and you determine repeatability to be ±6.3 ppm. In this example, 

you could calculate an absolute limit of ±10.59 ppm (1059 ppm × 0.01) or calculate that the 6.3 

ppm repeatability is equivalent to a repeatability of 0.5949008498584 %. 

(ii) Prior to July 1, 2013, you may treat tolerances (and equivalent specifications) specified in 

percentages as having fixed rather than infinite precision. For example, 2 % would be equivalent 

to 1.51 % to 2.50 % and 2.0 % would be equivalent to 1.951 % to 2.050 %. Note that this 

allowance applies whether or not the percentage is explicitly specified as a percentage of another 

value. 

(8) You may use measurement devices that incorporate internal rounding, consistent with the 

provisions of this paragraph (e)(8). You may use devices that use any rounding convention if 

they report six or more significant digits. You may use devices that report fewer than six digits, 

consistent with good engineering judgment and the accuracy, repeatability, and noise 

specifications of this part. Note that this provision does not necessarily require you to perform 

engineering analysis or keep records. 

(f) Interpretation of ranges. Interpret a range as a tolerance unless we explicitly identify it as an 

accuracy, repeatability, linearity, or noise specification. See §1065.1001 for the definition of 

tolerance. In this part, we specify two types of ranges: 

(1) Whenever we specify a range by a single value and corresponding limit values above and 

below that value, target any associated control point to that single value. Examples of this type 

of range include “±10 % of maximum pressure”, or “(30 ±10) kPa”. 

(2) Whenever we specify a range by the interval between two values, you may target any 

associated control point to any value within that range. An example of this type of range is “(40 

to 50) kPa”. 
(g) Scaling of specifications with respect to an applicable standard. Because this part 1065 is 

applicable to a wide range of engines and emission standards, some of the specifications in this 

part are scaled with respect to an engine’s applicable standard or maximum power. This ensures 

that the specification will be adequate to determine compliance, but not overly burdensome by 

requiring unnecessarily high-precision equipment. Many of these specifications are given with 

respect to a “flow-weighted mean” that is expected at the standard or during testing. Flowweighted mean is the mean of a quantity after it is weighted proportional to a corresponding flow 

rate. For example, if a gas concentration is measured continuously from the raw exhaust of an 

engine, its flow-weighted mean concentration is the sum of the products of each recorded 

concentration times its respective exhaust flow rate, divided by the sum of the recorded flow 

rates. As another example, the bag concentration from a CVS system is the same as the flowweighted mean concentration, because the CVS system itself flow-weights the bag 

concentration. Refer to §1065.602 for information needed to estimate and calculate flowweighted means. Wherever a specification is scaled to a value based upon an applicable 

standard, interpret the standard to be the family emission limit if the engine is certified under an 

emission credit program in the standard-setting part. 

§1065.25 Recordkeeping. 

The procedures in this part include various requirements to record data or other information. 

Refer to the standard-setting part and §1065.695 regarding recordkeeping requirements. You 

must promptly send us organized, written records in English if we ask for them. We may review 

them at any time.

Formatted: Underline

Deleted: If the standard-setting part does not 

specify recordkeeping requirements, store these 

records in any format and on any mediaand keep 

them readily available for one year after you send an 

associated application for certification, or one year 

after you generate the data if they do not support an 

application for certification. 
Subpart B—Equipment Specifications

§1065.101 Overview. 

(a) This subpart specifies equipment, other than measurement instruments, related to emission 

testing. The provisions of this subpart apply for all engine dynamometer testing where engine 

speeds and loads are controlled to follow a prescribed duty cycle. See subpart J of this part to 

determine which of the provisions of this subpart apply for field testing. This equipment 

includes three broad categories—dynamometers, engine fluid systems (such as fuel and intakeair systems), and emission-sampling hardware. 

(b) Other related subparts in this part identify measurement instruments (subpart C), describe 

how to evaluate the performance of these instruments (subpart D), and specify engine fluids and 

analytical gases (subpart H). 

(c) Subpart J of this part describes additional equipment that is specific to field testing. 

(d) Figures 1 and 2 of this section illustrate some of the possible configurations of laboratory 

equipment. These figures are schematics only; we do not require exact conformance to them. 

Figure 1 of this section illustrates the equipment specified in this subpart and gives some 

references to sections in this subpart. Figure 2 of this section illustrates some of the possible 

configurations of a full-flow dilution, constant-volume sampling (CVS) system. Not all possible 

CVS configurations are shown. 

(e) Dynamometer testing involves engine operation over speeds and loads that are controlled to a 

prescribed duty cycle. Field testing involves measuring emissions over normal in-use operation 

of a vehicle or piece of equipment. Field testing does not involve operating an engine over a 

prescribed duty cycle. 

Figure 1 of §1065.101—Engine dynamometer laboratory equipment. 

§1065.110 (b) Operator Demand

§1065.120 Fuel

§1065.122

Lubrication,

heat rejection,

and engine

accessories

§1065.125 Engine Intake Air §1065.130 Raw Engine Exhaust

§1065.145, §1065.150, §1065.170

Raw Exhaust Sampling

Continuous and Batch

Engine §1065.110 (a)

Work Inputs and Outputs

(e.g. Dynamometer)

§1065.140, §1065.145, 

§1065.150, §1065.170, §1065.195

Partial Flow Dilution Sampling 

Continuous and Batch

§1065.140

Dilution

§1065.140

§1065.145

§1065.170

§1065.195

CVS PM Sampling

§1065.145 

§1065.170

CVS Batch 

Sampling

§1065.190 PM filter

stabilization

and weighing

§1065.145 

§1065.150

CVS Continuous

Sampling

§1065.110 (b) Operator Demand

§1065.120 Fuel

§1065.122

Lubrication,

heat rejection,

and engine

accessories

§1065.125 Engine Intake Air §1065.130 Raw Engine Exhaust

§1065.145, §1065.150, §1065.170

Raw Exhaust Sampling

Continuous and Batch

Engine §1065.110 (a)

Work Inputs and Outputs

(e.g. Dynamometer)

§1065.140, §1065.145, 

§1065.150, §1065.170, §1065.195

Partial Flow Dilution Sampling 

Continuous and Batch

§1065.140

Dilution

§1065.140

§1065.145

§1065.170

§1065.195

CVS PM Sampling

§1065.145 

§1065.170

CVS Batch 

Sampling

§1065.190 PM filter

stabilization

and weighing

§1065.145 

§1065.150

CVS Continuous

Sampling
Figure 2 of §1065.101—Examples of some full-flow dilution sampling configurations. 

§1065.110 Work inputs and outputs, accessory work, and operator demand. 

(a) Work. Use good engineering judgment to simulate all engine work inputs and outputs as they 

typically would operate in use. Account for work inputs and outputs during an emission test by 

measuring them; or, if they are small, you may show by engineering analysis that disregarding 

them does not affect your ability to determine the net work output by more than ±0.5 % of the 

net expected work output over the test interval . Use equipment to simulate the specific types of 

work, as follows: 

(1) Shaft work. Use an engine dynamometer that is able to meet the cycle-validation criteria in 

§1065.514 over each applicable duty cycle. 

(i) You may use eddy-current and water-brake dynamometers for any testing that does not 

involve engine motoring, which is identified by negative torque commands in a reference duty 

cycle. See the standard setting part for reference duty cycles that are applicable to your engine. 

(ii) You may use alternating-current or direct-current motoring dynamometers for any type of 

testing. 

(iii) You may use one or more dynamometers. 

(iv) You may use any device that is already installed on a vehicle, equipment, or vessel to absorb 

work from the engine’s output shaft(s). Examples of these types of devices include a vessel’s 

propeller and a locomotive’s generator. 

(2) Electrical work. Use one or more of the following to simulate electrical work: 

(i) Use storage batteries or capacitors that are of the type and capacity installed in use. 

(ii) Use motors, generators, and alternators that are of the type and capacity installed in use. 
(iii) Use a resistor load bank to simulate electrical loads. 

(3) Pump, compressor, and turbine work. Use pumps, compressors, and turbines that are of the 

type and capacity installed in use. Use working fluids that are of the same type and 

thermodynamic state as normal in-use operation. 

(b) Laboratory work inputs. You may supply any laboratory inputs of work to the engine. For 

example, you may supply electrical work to the engine to operate a fuel system, and as another 

example you may supply compressor work to the engine to actuate pneumatic valves. We may 

ask you to show by engineering analysis your accounting of laboratory work inputs to meet the 

criterion in paragraph (a) of this section. 

(c) Engine accessories. You must either install or account for the work of engine accessories 

required to fuel, lubricate, or heat the engine, circulate coolant to the engine, or to operate 

aftertreatment devices. Operate the engine with these accessories installed or accounted for 

during all testing operations, including mapping. If these accessories are not powered by the 

engine during a test, account for the work required to perform these functions from the total 

work used in brake-specific emission calculations. For air-cooled engines only, subtract 

externally powered fan work from total work. We may ask you to show by engineering analysis 

your accounting of engine accessories to meet the criterion in paragraph (a) of this section. 

(d) Engine starter. You may install a production-type starter. 

(e) Operator demand for shaft work. Operator demand is defined in §1065.1001. Command the 

operator demand and the dynamometer(s) to follow a prescribed duty cycle with set points for 

engine speed and torque as specified in §1065.512. Refer to the standard-setting part to 

determine the specifications for your duty cycle(s). Use a mechanical or electronic input to 

control operator demand such that the engine is able to meet the validation criteria in §1065.514 

over each applicable duty cycle. Record feedback values for engine speed and torque as 

specified in §1065.512. Using good engineering judgment, you may improve control of operator 

demand by altering on-engine speed and torque controls. However, if these changes result in 

unrepresentative testing, you must notify us and recommend other test procedures under 

§1065.10(c)(1). 

(f) Other engine inputs. If your electronic control module requires specific input signals that are 

not available during dynamometer testing, such as vehicle speed or transmission signals, you 

may simulate the signals using good engineering judgment. Keep records that describe what 

signals you simulate and explain why these signals are necessary for representative testing. 

§1065.120 Fuel properties and fuel temperature and pressure. 

(a) Use fuels as specified in the standard-setting part, or as specified in subpart H of this part if 

fuels are not specified in the standard-setting part. 

(b) If the engine manufacturer specifies fuel temperature and pressure tolerances and the location 

where they are to be measured, then measure the fuel temperature and pressure at the specified 

location to show that you are within these tolerances throughout testing. 

(c) If the engine manufacturer does not specify fuel temperature and pressure tolerances, use 

good engineering judgment to set and control fuel temperature and pressure in a way that 

represents typical in-use fuel temperatures and pressures. 

§1065.122 Engine cooling and lubrication. 
(a) Engine cooling. Cool the engine during testing so its intake-air, oil, coolant, block, and head 

temperatures are within their expected ranges for normal operation. You may use auxiliary 

coolers and fans. 

(1) For air-cooled engines only, if you use auxiliary fans you must account for work input to the 

fan(s) according to §1065.110. 

(2) See §1065.125 for more information related to intake-air cooling. 

(3) See §1065.127 for more information related to exhaust gas recirculation cooling. 

(4) Measure temperatures at the manufacturer-specified locations. If the manufacturer does not 

specify temperature measurement locations, then use good engineering judgment to monitor 

intake-air, oil, coolant, block, and head temperatures to ensure that they are in their expected 

ranges for normal operation. 

(b) Forced cooldown. You may install a forced cooldown system for an engine and an exhaust 

aftertreatment device according to §1065.530(a)(1). 

(c) Lubricating oil. Use lubricating oils specified in §1065.740. For two-stroke engines that 

involve a specified mixture of fuel and lubricating oil, mix the lubricating oil with the fuel 

according to the manufacturer’s specifications. 

(d) Coolant. For liquid-cooled engines, use coolant as specified in §1065.745. 

§1065.125 Engine intake air. 

(a) Use the intake-air system installed on the engine or one that represents a typical in-use 

configuration. This includes the charge-air cooling and exhaust gas recirculation systems. 

(b) Measure temperature, humidity, and atmospheric pressure near the entrance of the furthest 

upstream engine or in-use intake system component. This would generally be near the engine’s 

air filter, or near the inlet to the in-use air intake system for engines that have no air filter. For 

engines with multiple intakes, make measurements near the entrance of each intake. 

(1) Pressure. You may use a single shared atmospheric pressure meter as long as your laboratory 

equipment for handling intake air maintains ambient pressure at all intakes within ±1 kPa of the 

shared atmospheric pressure. For engines with multiple intakes with separate atmospheric 

pressure measurements at each intake, use an average value for verifying compliance to 

§1065.520(b)(2). 

(2) Humidity. You may use a single shared humidity measurement for intake air as long as your 

equipment for handling intake air maintains dewpoint at all intakes to within ±0.5 C of the 

shared humidity measurement. For engines with multiple intakes with separate humidity 

measurements at each intake, use a flow-weighted average humidity for NOx corrections. If 

individual flows of each intake are not measured, use good engineering judgment to estimate a 

flow-weighted average humidity. 

(3) Temperature. Good engineering judgment may require that you shield the temperature 

sensors or move them upstream of an elbow in the laboratory intake system to prevent 

measurement errors due to radiant heating from hot engine surfaces or in-use intake system 

components. You must limit the distance between the temperature sensor and the entrance to the 

furthest upstream engine or in-use intake system component to no more than 12 times the outer 

hydraulic diameter of the entrance to the furthest upstream engine or in-use intake system 

component. However, you may exceed this limit if you use good engineering judgment to show 

that the temperature at the furthest upstream engine or in-use intake system component meets the 

specification in paragraph (c) of this section. For engines with multiple intakes, use a flowweighted average value to verify compliance with the specification in paragraph (c) of this 
section. If individual flows of each intake are not measured, you may use good engineering 

judgment to estimate a flow-weighted average temperature. You may also verify that each 

individual intake complies with the specification in paragraph (c) of this section. 

(c) Maintain the temperature of intake air to (25 ± 5) °C, except as follows: 

(1) Follow the standard-setting part if it specifies different temperatures. 

(2) For engines above 560 kW, you may use 35 °C as the upper bound of the tolerance. 

However, your system must be capable of controlling the temperature to the 25 °C setpoint for 

any steady-state operation at > 30% of maximum engine power. 

(3) You may ask us to allow you to apply a different setpoint for intake air temperature if it is 

necessary to remain consistent with the provisions of §1065.10(c)(1) for testing during which 

ambient temperature will be outside this range. 

(d) Use an intake-air restriction that represents production engines. Make sure the intake-air 

restriction is between the manufacturer’s specified maximum for a clean filter and the 

manufacturer’s specified maximum allowed. Measure the static differential pressure of the 

restriction at the location and at the speed and torque set points specified by the manufacturer. If 

the manufacturer does not specify a location, measure this pressure upstream of any turbocharger 

or exhaust gas recirculation system connection to the intake air system. If the manufacturer does 

not specify speed and torque points, measure this pressure while the engine outputs maximum 

power. As the manufacturer, you are liable for emission compliance for all values up to the 

maximum restriction you specify for a particular engine. 

(e) This paragraph (e) includes provisions for simulating charge-air cooling in the laboratory. 

This approach is described in paragraph (e)(1) of this section. Limits on using this approach are 

described in paragraphs (e)(2) and (3) of this section. 

(1) Use a charge-air cooling system with a total intake-air capacity that represents production 

engines’ in-use installation. Design any laboratory charge-air cooling system to minimize 

accumulation of condensate. Drain any accumulated condensate. Before starting a duty cycle 

(or preconditioning for a duty cycle), completely close all drains that would normally be closed 

during in-use operation. Keep those drains closed during the emission test. Maintain coolant 

conditions as follows: 

(i) Maintain a coolant temperature of at least 20 C at the inlet to the charge-air cooler 

throughout testing. We recommend maintaining a coolant temperature of 25 5 oC at the inlet of 

the charge-air cooler. 

(ii) At the engine conditions specified by the manufacturer, set the coolant flow rate to achieve 

an air temperature within ±5 C of the value specified by the manufacturer after the charge-air 

cooler’s outlet. Measure the air-outlet temperature at the location specified by the manufacturer. 

Use this coolant flow rate set point throughout testing. If the engine manufacturer does not 

specify engine conditions or the corresponding charge-air cooler air outlet temperature, set the 

coolant flow rate at maximum engine power to achieve a charge-air cooler air outlet temperature 

that represents in-use operation. 

(iii) If the engine manufacturer specifies pressure-drop limits across the charge-air cooling 

system, ensure that the pressure drop across the charge-air cooling system at engine conditions 

specified by the manufacturer is within the manufacturer’s specified limit(s). Measure the 

pressure drop at the manufacturer’s specified locations. 

(2) Using a constant flow rate as described in paragraph (e)(1) of this section may result in 

unrepresentative overcooling of the intake air. The provisions of this paragraph (e)(2) apply 

instead of the provisions of §1065.10(c)(1) for this simulation. Our allowance to cool intake air 
as specified in this paragraph (e) does not affect your liability for field testing or for laboratory 

testing that is done in a way that better represents in-use operation. Where we determine that this 

allowance adversely affects your ability to demonstrate that your engines would comply with 

emission standards under in-use conditions, we may require you to use more sophisticated 

setpoints and controls of charge-air pressure drop, coolant temperature, and flow rate to achieve 

more representative results. 

(3) This approach does not apply for field testing. You may not correct measured emission 

levels from field testing to account for any differences caused by the simulated cooling in the 

laboratory. 

§1065.127 Exhaust gas recirculation. 

Use the exhaust gas recirculation (EGR) system installed with the engine or one that represents a 

typical in-use configuration. This includes any applicable EGR cooling devices. 

§1065.130 Engine exhaust. 

(a) General. Use the exhaust system installed with the engine or one that represents a typical inuse configuration. This includes any applicable aftertreatment devices. 

(b) Aftertreatment configuration. If you do not use the exhaust system installed with the engine, 

configure any aftertreatment devices as follows: 

(1) Position any aftertreatment device so its distance from the nearest exhaust manifold flange or 

turbocharger outlet is within the range specified by the engine manufacturer in the application for 

certification. If this distance is not specified, position aftertreatment devices to represent typical 

in-use vehicle configurations. 

(2) You may use exhaust tubing that is not from the in-use exhaust system upstream of any 

aftertreatment device that is of diameter(s) typical of in-use configurations. If you use exhaust 

tubing that is not from the in-use exhaust system upstream of any aftertreatment device, position 

each aftertreatment device according to paragraph (b)(1) of this section. 

(c) Sampling system connections. Connect an engine’s exhaust system to any raw sampling 

location or dilution stage, as follows: 

(1) Minimize laboratory exhaust tubing lengths and use a total length of laboratory tubing of no 

more than 10 m or 50 outside diameters, whichever is greater. The start of laboratory exhaust 

tubing should be specified as the exit of the exhaust manifold, turbocharger outlet, last 

aftertreatment device, or the in-use exhaust system, whichever is furthest downstream. The end 

of laboratory exhaust tubing should be specified as the sample point, or first point of dilution. If 

laboratory exhaust tubing consists of several different outside tubing diameters, count the 

number of diameters of length of each individual diameter, then sum all the diameters to 

determine the total length of exhaust tubing in diameters. Use the mean outside diameter of any 

converging or diverging sections of tubing. Use outside hydraulic diameters of any noncircular 

sections. For multiple stack configurations where all the exhaust stacks are combined, the start 

of the laboratory exhaust tubing may be taken at the last joint of where all the stacks are 

combined. 

(2) You may install short sections of flexible laboratory exhaust tubing at any location in the 

engine or laboratory exhaust systems. You may use up to a combined total of 2 m or 10 outside 

diameters of flexible exhaust tubing. 

(3) Insulate any laboratory exhaust tubing downstream of the first 25 outside diameters of length. 
(4) Use laboratory exhaust tubing materials that are smooth-walled, electrically conductive, and 

not reactive with exhaust constituents. Stainless steel is an acceptable material. 

(5) We recommend that you use laboratory exhaust tubing that has either a wall thickness of less 

than 2 mm or is air gap-insulated to minimize temperature differences between the wall and the 

exhaust. 

(6) We recommend that you connect multiple exhaust stacks from a single engine into one stack 

upstream of any emission sampling. To ensure mixing of the multiple exhaust streams before 

emission sampling, you may configure the exhaust system with turbulence generators, such as 

orifice plates or fins, to achieve good mixing. We recommend a minimum Reynolds number, 

Re#, of 4000 for the combined exhaust stream, where Re# is based on the inside diameter of the 

single stack. Re# is defined in §1065.640. 

(d) In-line instruments. You may insert instruments into the laboratory exhaust tubing, such as 

an in-line smoke meter. If you do this, you may leave a length of up to 5 outside diameters of 

laboratory exhaust tubing uninsulated on each side of each instrument, but you must leave a 

length of no more than 25 outside diameters of laboratory exhaust tubing uninsulated in total, 

including any lengths adjacent to in-line instruments. 

(e) Leaks. Minimize leaks sufficiently to ensure your ability to demonstrate compliance with the 

applicable standards. We recommend performing a chemical balance of fuel, intake air, and 

exhaust according to §1065.655 to verify exhaust system integrity. 

(f) Grounding. Electrically ground the entire exhaust system. 

(g) Forced cooldown. You may install a forced cooldown system for an exhaust aftertreatment 

device according to §1065.530(a)(1)(i). 

(h) Exhaust restriction. As the manufacturer, you are liable for emission compliance for all 

values up to the maximum restriction(s) you specify for a particular engine. Measure and set 

exhaust restriction(s) at the location(s) and at the engine speed and torque values specified by the 

manufacturer. Also, for variable-restriction aftertreatment devices, measure and set exhaust 

restriction(s) at the aftertreatment condition (degreening/aging and regeneration/loading level)

specified by the manufacturer. If the manufacturer does not specify a location, measure this 

pressure downstream of any turbocharger. If the manufacturer does not specify speed and torque 

points, measure pressure while the engine produces maximum power. Use an exhaust-restriction 

setpoint that represents a typical in-use value, if available. If a typical in-use value for exhaust 

restriction is not available, set the exhaust restriction at (80 to 100) % of the maximum exhaust 

restriction specified by the manufacturer, or if the maximum is 5 kPa or less, the set point must 

be no less than 1.0 kPa from the maximum. For example, if the maximum back pressure is 4.5 

kPa, do not use an exhaust restriction set point that is less than 3.5 kPa. 

(i) Open crankcase emissions. If the standard-setting part requires measuring open crankcase 

emissions, you may either measure open crankcase emissions separately using a method that we 

approve in advance, or route open crankcase emissions directly into the exhaust system for 

emission measurement. If the engine is not already configured to route open crankcase 

emissions for emission measurement, route open crankcase emissions as follows: 

(1) Use laboratory tubing materials that are smooth-walled, electrically conductive, and not 

reactive with crankcase emissions. Stainless steel is an acceptable material. Minimize tube 

lengths. We also recommend using heated or thin-walled or air gap-insulated tubing to minimize 

temperature differences between the wall and the crankcase emission constituents. 

(2) Minimize the number of bends in the laboratory crankcase tubing and maximize the radius of 

any unavoidable bend. 
(3) Use laboratory crankcase exhaust tubing that meets the engine manufacturer’s specifications 

for crankcase back pressure. 

(4) Connect the crankcase exhaust tubing into the raw exhaust downstream of any aftertreatment 

system, downstream of any installed exhaust restriction, and sufficiently upstream of any sample 

probes to ensure complete mixing with the engine’s exhaust before sampling. Extend the 

crankcase exhaust tube into the free stream of exhaust to avoid boundary-layer effects and to 

promote mixing. You may orient the crankcase exhaust tube’s outlet in any direction relative to 

the raw exhaust flow. 

§1065.140 Dilution for gaseous and PM constituents. 

(a) General. You may dilute exhaust with ambient air, synthetic air, or nitrogen. References in 

this part to “dilution air” may include any of these. For gaseous emission measurement, the 

dilution air must be at least 15 °C. Note that the composition of the dilution air affects some 

gaseous emission measurement instruments’ response to emissions. We recommend diluting 

exhaust at a location as close as possible to the location where ambient air dilution would occur 

in use. Dilution may occur in a single stage or in multiple stages. For dilution in multiple stages, 

the first stage is considered primary dilution and later stages are considered secondary dilution.

(b) Dilution-air conditions and background concentrations. Before dilution air is mixed with 

exhaust, you may precondition it by increasing or decreasing its temperature or humidity. You 

may also remove constituents to reduce their background concentrations. The following 

provisions apply to removing constituents or accounting for background concentrations: 

(1) You may measure constituent concentrations in the dilution air and compensate for 

background effects on test results. See §1065.650 for calculations that compensate for 

background concentrations (40 CFR 1066.620 for vehicle testing). 

(2) Measure these background concentrations the same way you measure diluted exhaust 

constituents, or measure them in a way that does not affect your ability to demonstrate 

compliance with the applicable standards. For example, you may use the following 

simplifications for background sampling: 

(i) You may disregard any proportional sampling requirements. 

(ii) You may use unheated gaseous sampling systems. 

(iii) You may use unheated PM sampling systems. 

(iv) You may use continuous sampling if you use batch sampling for diluted emissions. 

(v) You may use batch sampling if you use continuous sampling for diluted emissions. 

(3) For removing background PM, we recommend that you filter all dilution air, including 

primary full-flow dilution air, with high-efficiency particulate air (HEPA) filters that have an 

initial minimum collection efficiency specification of 99.97 % (see §1065.1001 for procedures 

related to HEPA-filtration efficiencies). Ensure that HEPA filters are installed properly so that 

background PM does not leak past the HEPA filters. If you choose to correct for background 

PM without using HEPA filtration, demonstrate that the background PM in the dilution air 

contributes less than 50 % to the net PM collected on the sample filter. You may correct net PM 

without restriction if you use HEPA filtration. 

(c) Full-flow dilution; constant-volume sampling (CVS). You may dilute the full flow of raw 

exhaust in a dilution tunnel that maintains a nominally constant volume flow rate, molar flow 

rate or mass flow rate of diluted exhaust, as follows: 

(1) Construction. Use a tunnel with inside surfaces of 300 series stainless steel. Electrically 

ground the entire dilution tunnel. We recommend a thin-walled and insulated dilution tunnel to 

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minimize temperature differences between the wall and the exhaust gases. You may not use any 

flexible tubing in the dilution tunnel upstream of where emissions are measured. You may use 

nonconductive flexible tubing downstream of the PM sample probe and upstream of the CVS 

flow meter consistent with good engineering judgment, as long as it does not affect your ability 

to demonstrate compliance with the standard. 

(2) Pressure control. Maintain static pressure at the location where raw exhaust is introduced 

into the tunnel within ±1.2 kPa of atmospheric pressure. You may use a booster blower to 

control this pressure. If you test using more careful pressure control and you show by 

engineering analysis or by test data that you require this level of control to demonstrate 

compliance at the applicable standards, we will maintain the same level of static pressure control 

when we test. 

(3) Mixing. Introduce raw exhaust into the tunnel by directing it downstream along the 

centerline of the tunnel. If you dilute directly from the exhaust stack (i.e., tailpipe), the end of 

the exhaust stack is considered to be the start of the dilution tunnel. You may introduce a 

fraction of dilution air radially from the tunnel’s inner surface to minimize exhaust interaction 

with the tunnel walls. You may configure the system with turbulence generators such as orifice 

plates or fins to achieve good mixing. We recommend a minimum Reynolds number, Re#, of 

4000 for the diluted exhaust stream, where Re# is based on the inside diameter of the dilution 

tunnel. Re# is defined in §1065.640. 

(4) Flow measurement preconditioning. You may condition the diluted exhaust before 

measuring its flow rate, as long as this conditioning takes place downstream of any heated HC or 

PM sample probes, as follows: 

(i) You may use flow straighteners, pulsation dampeners, or both of these. 

(ii) You may use a filter. 

(iii) You may use a heat exchanger to control the temperature upstream of any flow meter, but 

you must take steps to prevent aqueous condensation as described in paragraph (c)(6) of this 

section. 

(5) Flow measurement. Section 1065.240 describes measurement instruments for diluted exhaust 

flow. 

(6) Aqueous condensation. This paragraph (c)(6) describes how you must address aqueous 

condensation in the CVS. As described below, you may meet these requirements by preventing 

or limiting aqueous condensation in the CVS from the exhaust inlet to the last emission sample 

probe. See that paragraph for provisions related to the CVS between the last emission sample 

probe and the CVS flow meter. You may heat and/or insulate the dilution tunnel walls, as well 

as the bulk stream tubing downstream of the tunnel to prevent or limit aqueous condensation. 

Where we allow aqueous condensation to occur, use good engineering judgment to ensure that 

the condensation does not affect your ability to demonstrate that your engines comply with the 

applicable standards (see §1065.10(a)). 

(i) Preventing aqueous condensation. To prevent condensation, you must keep the temperature 

of internal surfaces, excluding any sample probes, above the dew point of the dilute exhaust 

passing through the CVS tunnel. Use good engineering judgment to monitor temperatures in the 

CVS. For the purposes of this paragraph (c)(6), assume that aqueous condensation is pure water 

condensate only, even though the definition of “aqueous condensation” in §1065.1001 includes 

condensation of any constituents that contain water. No specific verification check is required 

under this paragraph (c)(6)(i), but we may ask you to show how you comply with this 

requirement. You may use engineering analysis, CVS tunnel design, alarm systems, 

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measurements of wall temperatures, and calculation of water dew point to demonstrate 

compliance with this requirement. For optional CVS heat exchangers, you may use the lowest 

water temperature at the inlet(s) and outlet(s) to determine the minimum internal surface 

temperature. 

(ii) Limiting aqueous condensation. This paragraph (c)(6)(ii) specifies limits of allowable 

condensation and requires you to verify that the amount of condensation that occurs during each 

test interval does not exceed the specified limits. 

(A) Use chemical balance equations in §1065.655 to calculate the mole fraction of water in the 

dilute exhaust continuously during testing. Alternatively, you may continuously measure the 

mole fraction of water in the dilute exhaust prior to any condensation during testing. Use good 

engineering judgment to select, calibrate and verify water analyzers/detectors. The linearity 

verification requirements of §1065.307 do not apply to water analyzers/detectors used to correct 

for the water content in exhaust samples. 

(B) Use good engineering judgment to select and monitor locations on the CVS tunnel walls 

prior to the last emission sample probe. If you are also verifying limited condensation from the 

last emission sample probe to the CVS flow meter, use good engineering judgment to select and 

monitor locations on the CVS tunnel walls, optional CVS heat exchanger, and CVS flow meter. 

For optional CVS heat exchangers, you may use the lowest water temperature at the inlet(s) and 

outlet(s) to determine the minimum internal surface temperature. Identify the minimum surface 

temperature on a continuous basis. 

(C) Identify the maximum potential mole fraction of dilute exhaust lost on a continuous basis 

during the entire test interval. This value must be less than or equal to 0.02. Calculate on a 

continuous basis the mole fraction of water that would be in equilibrium with liquid water at the 

measured minimum surface temperature. Subtract this mole fraction from the mole fraction of 

water that would be in the exhaust without condensation (either measured or from the chemical 

balance), and set any negative values to zero. This difference is the potential mole fraction of the 

dilute exhaust that would be lost due to water condensation on a continuous basis. 

(D) Integrate the product of the molar flow rate of the dilute exhaust and the potential mole 

fraction of dilute exhaust lost, and divide by the totalized dilute exhaust molar flow over the test 

interval. This is the potential mole fraction of the dilute exhaust that would be lost due to water 

condensation over the entire test interval. Note that this assumes no re-evaporation. This value 

must be less than or equal to 0.005. 

(7) Flow compensation. Maintain nominally constant molar, volumetric or mass flow of diluted 

exhaust. You may maintain nominally constant flow by either maintaining the temperature and 

pressure at the flow meter or by directly controlling the flow of diluted exhaust. You may also 

directly control the flow of proportional samplers to maintain proportional sampling. For an 

individual test, verify proportional sampling as described in §1065.545. 

(d) Partial-flow dilution (PFD). You may dilute a partial flow of raw or previously diluted 

exhaust before measuring emissions. Section 1065.240 describes PFD-related flow measurement 

instruments. PFD may consist of constant or varying dilution ratios as described in paragraphs 

(d)(2) and (3) of this section. An example of a constant dilution ratio PFD is a “secondary 

dilution PM” measurement system. 

(1) Applicability. (i) You may use PFD to extract a proportional raw exhaust sample for any 

batch or continuous PM emission sampling over any transient duty cycle, any steady-state duty 

cycle, or any ramped-modal cycle. 

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(ii) You may use PFD to extract a proportional raw exhaust sample for any batch or continuous 

gaseous emission sampling over any transient duty cycle, any steady-state duty cycle, or any 

ramped-modal cycle. 

(iii) You may use PFD to extract a proportional raw exhaust sample for any batch or continuous 

field-testing. 

(iv)You may use PFD to extract a proportional diluted exhaust sample from a CVS for any batch 

or continuous emission sampling. 

(v) You may use PFD to extract a constant raw or diluted exhaust sample for any continuous 

emission sampling. 

(vi) You may use PFD to extract a constant raw or diluted exhaust sample for any steady-state 

emission sampling. 

(2) Constant dilution-ratio PFD. Do one of the following for constant dilution-ratio PFD: 

(i) Dilute an already proportional flow. For example, you may do this as a way of performing 

secondary dilution from a CVS tunnel to achieve overall dilution ratio for PM sampling. 

(ii) Continuously measure constituent concentrations. For example, you might dilute to 

precondition a sample of raw exhaust to control its temperature, humidity, or constituent 

concentrations upstream of continuous analyzers. In this case, you must take into account the 

dilution ratio before multiplying the continuous concentration by the sampled exhaust flow rate. 

(iii) Extract a proportional sample from a separate constant dilution ratio PFD system. For 

example, you might use a variable-flow pump to proportionally fill a gaseous storage medium 

such as a bag from a PFD system. In this case, the proportional sampling must meet the same 

specifications as varying dilution ratio PFD in paragraph (d)(3) of this section. 

(iv) For each mode of a discrete-mode test (such as a locomotive notch setting or a specific 

setting for speed and torque), use a constant dilution ratio for any PM sampling. You must 

change the overall PM sampling system dilution ratio between modes so that the dilution ratio on 

the mode with the highest exhaust flow rate meets §1065.140(e)(2) and the dilution ratios on all 

other modes is higher than this (minimum) dilution ratio by the ratio of the maximum exhaust 

flow rate to the exhaust flow rate of the corresponding other mode. This is the same dilution 

ratio requirement for RMC or field transient testing. You must account for this change in 

dilution ratio in your emission calculations. 

(3) Varying dilution-ratio PFD. All the following provisions apply for varying dilution-ratio 

PFD: 

(i) Use a control system with sensors and actuators that can maintain proportional sampling over 

intervals as short as 200 ms (i.e., 5 Hz control). 

(ii) For control input, you may use any sensor output from one or more measurements; for 

example, intake-air flow, fuel flow, exhaust flow, engine speed, and intake manifold temperature 

and pressure. 

(iii) Account for any emission transit time in the PFD system, as necessary. 

(iv) You may use preprogrammed data if they have been determined for the specific test site, 

duty cycle, and test engine from which you dilute emissions. 

(v) We recommend that you run practice cycles to meet the verification criteria in §1065.545. 

Note that you must verify every emission test by meeting the verification criteria with the data 

from that specific test. Data from previously verified practice cycles or other tests may not be 

used to verify a different emission test. 

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(vi) You may not use a PFD system that requires preparatory tuning or calibration with a CVS or 

with the emission results from a CVS. Rather, you must be able to independently calibrate the 

PFD. 

(e) Dilution air temperature, dilution ratio, residence time, and temperature control of PM 

samples. Dilute PM samples at least once upstream of transfer lines. You may dilute PM 

samples upstream of a transfer line using full-flow dilution, or partial-flow dilution immediately 

downstream of a PM probe. In the case of partial-flow dilution, you may have up to 26 cm of 

insulated length between the end of the probe and the dilution stage, but we recommend that the 

length be as short as practical. The intent of these specifications is to minimize heat transfer to 

or from the emission sample before the final stage of dilution, other than the heat you may need 

to add to prevent aqueous condensation. This is accomplished by initially cooling the sample 

through dilution. Configure dilution systems as follows: 

(1) Set the dilution air temperature to (25 ±5) °C. Use good engineering judgment to select a 

location to measure this temperature that is as close as practical upstream of the point where 

dilution air mixes with raw exhaust. 

(2) For any PM dilution system (i.e., CVS or PFD), add dilution air to the raw exhaust such that 

the minimum overall ratio of diluted exhaust to raw exhaust is within the range of (5:1 to 7:1) 

and is at least 2:1 for any primary dilution stage. Base this minimum value on the maximum 

engine exhaust flow rate for a given test interval. Either measure the maximum exhaust flow 

during a practice run of the test interval or estimate it based on good engineering judgment (for 

example, you might rely on manufacturer-published literature). 

(3) Configure any PM dilution system to have an overall residence time of (1.0 to 5.0) s, as 

measured from the location of initial dilution air introduction to the location where PM is 

collected on the sample media. Also configure the system to have a residence time of at least 

0.50 s, as measured from the location of final dilution air introduction to the location where PM 

is collected on the sample media. When determining residence times within sampling system 

volumes, use an assumed flow temperature of 25 °C and pressure of 101.325 kPa. 

(4) Control sample temperature to a (47 ±5) °C tolerance, as measured anywhere within 20 cm 

upstream or downstream of the PM storage media (such as a filter). Measure this temperature 

with a bare-wire junction thermocouple with wires that are (0.500 ±0.025) mm diameter, or with 

another suitable instrument that has equivalent performance. 

§1065.145 Gaseous and PM probes, transfer lines, and sampling system components. 

(a) Continuous and batch sampling. Determine the total mass of each constituent with 

continuous or batch sampling. Both types of sampling systems have probes, transfer lines, and 

other sampling system components that are described in this section. 

(b) Options for engines with multiple exhaust stacks. Measure emissions from a test engine as 

described in this paragraph (b) if it has multiple exhaust stacks. You may choose to use different 

measurement procedures for different pollutants under this paragraph (b) for a given test. For 

purposes of this part 1065, the test engine includes all the devices related to converting the 

chemical energy in the fuel to the engine’s mechanical output energy. This may or may not 

involve vehicle- or equipment-based devices. For example, all of an engine’s cylinders are 

considered to be part of the test engine even if the exhaust is divided into separate exhaust stacks. 

As another example, all the cylinders of a diesel-electric locomotive are considered to be part of 

the test engine even if they transmit power through separate output shafts, such as might occur 

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temperature

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with multiple engine-generator sets working in tandem. Use one of the following procedures to 

measure emissions with multiple exhaust stacks: 

(1) Route the exhaust flow from the multiple stacks into a single flow as described in 

§1065.130(c)(6). Sample and measure emissions after the exhaust streams are mixed. Calculate 

the emissions as a single sample from the entire engine. We recommend this as the preferred 

option, since it requires only a single measurement and calculation of the exhaust molar flow for 

the entire engine. 

(2) Sample and measure emissions from each stack and calculate emissions separately for each 

stack. Add the mass (or mass rate) emissions from each stack to calculate the emissions from the 

entire engine. Testing under this paragraph (b)(2) requires measuring or calculating the exhaust 

molar flow for each stack separately. If the exhaust molar flow in each stack cannot be 

calculated from combustion air flow(s), fuel flow(s), and measured gaseous emissions, and it is 

impractical to measure the exhaust molar flows directly, you may alternatively proportion the 

engine’s calculated total exhaust molar flow rate (where the flow is calculated using combustion 

air mass flow(s), fuel mass flow(s), and emissions concentrations) based on exhaust molar flow 

measurements in each stack using a less accurate, non-traceable method. For example, you may 

use a total pressure probe and static pressure measurement in each stack. 

(3) Sample and measure emissions from one stack and repeat the duty cycle as needed to collect 

emissions from each stack separately. Calculate the emissions from each stack and add the 

separate measurements to calculate the mass (or mass rate) emissions from the entire engine. 

Testing under this paragraph (b)(3) requires measuring or calculating the exhaust molar flow for 

each stack separately. You may alternatively proportion the engine’s calculated total exhaust 

molar flow rate based on calculation and measurement limitations as described in paragraph 

(b)(2) of this section. Use the average of the engine’s total power or work values from the 

multiple test runs to calculate brake-specific emissions. Divide the total mass (or mass rate) of 

each emission by the average power (or work). You may alternatively use the engine power or 

work associated with the corresponding stack during each test run if these values can be 

determined for each stack separately. 

(4) Sample and measure emissions from each stack separately and calculate emissions for the 

entire engine based on the stack with the highest concentration. Testing under this paragraph 

(b)(4) requires only a single exhaust flow measurement or calculation for the entire engine. You 

may determine which stack has the highest concentration by performing multiple test runs, 

reviewing the results of earlier tests, or using good engineering judgment. Note that the highest 

concentration of different pollutants may occur in different stacks. Note also that the stack with 

the highest concentration of a pollutant during a test interval for field testing may be a different 

stack than the one you identified based on average concentrations over a duty cycle. 

(5) Sample emissions from each stack separately and combine the wet sample streams from each 

stack proportionally to the exhaust molar flows in each stack. Measure the emission 

concentrations and calculate the emissions for the entire engine based on these weighted 

concentrations. Testing under this paragraph (b)(5) requires measuring or calculating the 

exhaust molar flow for each stack separately during the test run to proportion the sample streams 

from each stack. If it is impractical to measure the exhaust molar flows directly, you may 

alternatively proportion the wet sample streams based on less accurate, non-traceable flow 

methods. For example, you may use a total pressure probe and static pressure measurement in 

each stack. The following restrictions apply for testing under this paragraph (b)(5): 
(i) You must use an accurate, traceable measurement or calculation of the engine’s total exhaust 

molar flow rate for calculating the mass of emissions from the entire engine. 

(ii) You may dry the single, combined, proportional sample stream; you may not dry the sample 

streams from each stack separately. 

(iii) You must measure and proportion the sample flows from each stack with active flow 

controls. For PM sampling, you must measure and proportion the diluted sample flows from 

each stack with active flow controls that use only smooth walls with no sudden change in crosssectional area. For example, you may control the dilute exhaust PM sample flows using 

electrically conductive vinyl tubing and a control device that pinches the tube over a long enough 

transition length so no flow separation occurs. 

(iv) For PM sampling, the transfer lines from each stack must be joined so the angle of the 

joining flows is 12.5o or less. Note that the exhaust manifold must meet the same specifications 

as the transfer line according to paragraph (d) of this section. 

(6) Sample emissions from each stack separately and combine the wet sample streams from each 

stack equally. Measure the emission concentrations and calculate the emissions for the entire 

engine based on these measured concentrations. Testing under this paragraph (b)(6) assumes 

that the raw-exhaust and sample flows are the same for each stack. The following restrictions 

apply for testing under this paragraph (b)(6): 

(i) You must measure and demonstrate that the sample flow from each stack is within 5 % of the 

value from the stack with the highest sample flow. You may alternatively ensure that the stacks 

have equal flow rates without measuring sample flows by designing a passive sampling system 

that meets the following requirements: 

(A) The probes and transfer line branches must be symmetrical, have equal lengths and 

diameters, have the same number of bends, and have no filters. 

(B) If probes are designed such that they are sensitive to stack velocity, the stack velocity must 

be similar at each probe. For example, a static pressure probe used for gaseous sampling is not 

sensitive to stack velocity. 

(C) The stack static pressure must be the same at each probe. You can meet this requirement by 

placing probes at the end of stacks that are vented to atmosphere. 

(D) For PM sampling, the transfer lines from each stack must be joined so the angle of the 

joining flows is 12.5o or less. Note that the exhaust manifold must meet the same specifications 

as the transfer line according to paragraph (d) of this section. 

(ii) You may use the procedure in this paragraph (b)(6) only if you perform an analysis showing 

that the resulting error due to imbalanced stack flows and concentrations is either at or below 2 

%. You may alternatively show that the resulting error does not impact your ability to 

demonstrate compliance with applicable standards. For example, you may use less accurate, 

non-traceable measurements of emission concentrations and molar flow in each stack and 

demonstrate that the imbalances in flows and concentrations cause 2 % or less error. 

(iii) For a two-stack engine, you may use the procedure in this paragraph (b)(6) only if you can 

show that the stack with the higher flow has the lower average concentration for each pollutant 

over the duty cycle. 

(iv) You must use an accurate, traceable measurement or calculation of the engine’s total exhaust 

molar flow rate for calculating the mass of emissions from the entire engine. 

(v) You may dry the single, equally combined, sample stream; you may not dry the sample 

streams from each stack separately. 
(vi) You may determine your exhaust flow rates with a chemical balance of exhaust gas 

concentrations and either intake air flow or fuel flow. 

(c) Gaseous and PM sample probes. A probe is the first fitting in a sampling system. It 

protrudes into a raw or diluted exhaust stream to extract a sample, such that its inside and outside 

surfaces are in contact with the exhaust. A sample is transported out of a probe into a transfer 

line, as described in paragraph (d) of this section. The following provisions apply to sample 

probes: 

(1) Probe design and construction. Use sample probes with inside surfaces of 300 series stainless 

steel or, for raw exhaust sampling, use any nonreactive material capable of withstanding raw 

exhaust temperatures. Locate sample probes where constituents are mixed to their mean sample 

concentration. Take into account the mixing of any crankcase emissions that may be routed into 

the raw exhaust. Locate each probe to minimize interference with the flow to other probes. We 

recommend that all probes remain free from influences of boundary layers, wakes, and eddies—

especially near the outlet of a raw-exhaust stack where unintended dilution might occur. Make 

sure that purging or back-flushing of a probe does not influence another probe during testing. 

You may use a single probe to extract a sample of more than one constituent as long as the probe 

meets all the specifications for each constituent. 

(2) Gaseous sample probes. Use either single-port or multi-port probes for sampling gaseous 

emissions. You may orient these probes in any direction relative to the raw or diluted exhaust 

flow. For some probes, you must control sample temperatures, as follows: 

(i) For probes that extract NOx from diluted exhaust, control the probe’s wall temperature to 

prevent aqueous condensation. 

(ii) For probes that extract hydrocarbons for THC or NMHC analysis from the diluted exhaust of 

compression-ignition engines, two-stroke spark-ignition engines, or four-stroke spark-ignition 

engines at or below 19 kW, we recommend heating the probe to minimize hydrocarbon 

contamination consistent with good engineering judgment. If you routinely fail the 

contamination check in the 1065.520 pretest check, we recommend heating the probe section to 

approximately 190 °C to minimize contamination. 

(3) PM sample probes. Use PM probes with a single opening at the end. Orient PM probes to 

face directly upstream. If you shield a PM probe’s opening with a PM pre-classifier such as a 

hat, you may not use the preclassifier we specify in paragraph (f)(1) of this section. We 

recommend sizing the inside diameter of PM probes to approximate isokinetic sampling at the 

expected mean flow rate. 

(d) Transfer lines. You may use transfer lines to transport an extracted sample from a probe to 

an analyzer, storage medium, or dilution system, noting certain restrictions for PM sampling in 

§1065.140(e). Minimize the length of all transfer lines by locating analyzers, storage media, and 

dilution systems as close to probes as practical. We recommend that you minimize the number 

of bends in transfer lines and that you maximize the radius of any unavoidable bend. Avoid 

using 90elbows, tees, and cross-fittings in transfer lines. Where such connections and fittings 

are necessary, take steps, using good engineering judgment, to ensure that you meet the 

temperature tolerances in this paragraph (d). This may involve measuring temperature at various 

locations within transfer lines and fittings. You may use a single transfer line to transport a 

sample of more than one constituent, as long as the transfer line meets all the specifications for 

each constituent. The following construction and temperature tolerances apply to transfer lines: 

(1) Gaseous samples. Use transfer lines with inside surfaces of 300 series stainless steel, PTFE, 

VitonTM, or any other material that you demonstrate has better properties for emission sampling. 

Deleted: tailpipe

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For raw exhaust sampling, use a non-reactive material capable of withstanding raw exhaust 

temperatures. You may use in-line filters if they do not react with exhaust constituents and if the 

filter and its housing meet the same temperature requirements as the transfer lines, as follows: 

(i) For NOx transfer lines upstream of either an NO2-to-NO converter that meets the 

specifications of §1065.378 or a chiller that meets the specifications of §1065.376, maintain a 

sample temperature that prevents aqueous condensation. 

(ii) For THC transfer lines for testing compression-ignition engines, two-stroke spark-ignition 

engines, or four-stroke spark-ignition engines at or below 19 kW, maintain a wall temperature 

tolerance throughout the entire line of (191 ±11) C. If you sample from raw exhaust, you may 

connect an unheated, insulated transfer line directly to a probe. Design the length and insulation 

of the transfer line to cool the highest expected raw exhaust temperature to no lower than 191 C, 

as measured at the transfer line’s outlet. For dilute sampling, you may use a transition zone 

between the probe and transfer line of up to 92 cm to allow your wall temperature to transition to 

(191 ±11) °C. 

(2) PM samples. We recommend heated transfer lines or a heated enclosure to minimize 

temperature differences between transfer lines and exhaust constituents. Use transfer lines that 

are inert with respect to PM and are electrically conductive on the inside surfaces. We 

recommend using PM transfer lines made of 300 series stainless steel. Electrically ground the 

inside surface of PM transfer lines. 

(e) Optional sample-conditioning components for gaseous sampling. You may use the following 

sample-conditioning components to prepare gaseous samples for analysis, as long as you do not 

install or use them in a way that adversely affects your ability to show that your engines comply 

with all applicable gaseous emission standards. 

(1) NO2-to-NO converter. You may use an NO2-to-NO converter that meets the converter 

conversion verification specified in §1065.378 at any point upstream of a NOx analyzer, sample 

bag, or other storage medium. 

(2) Sample dryer. You may use either type of sample dryer described in this paragraph (e)(2) to 

decrease the effects of water on gaseous emission measurements. You may not use a chemical 

dryer, or use dryers upstream of PM sample filters. 

(i) Osmotic-membrane. You may use an osmotic-membrane dryer upstream of any gaseous 

analyzer or storage medium, as long as it meets the temperature specifications in paragraph 

(d)(1) of this section. Because osmotic-membrane dryers may deteriorate after prolonged 

exposure to certain exhaust constituents, consult with the membrane manufacturer regarding 

your application before incorporating an osmotic-membrane dryer. Monitor the dewpoint, Tdew, 

and absolute pressure, ptotal, downstream of an osmotic-membrane dryer. You may use 

continuously recorded values of Tdew and ptotal in the amount of water calculations specified in 

§1065.645. For our testing we may use average temperature and pressure values over the test 

interval or a nominal pressure value that we estimate as the dryer’s average pressure expected 

during testing as constant values in the amount of water calculations specified in §1065.645. For 

your testing, you may use the maximum temperature or minimum pressure values observed 

during a test interval or duty cycle or the high alarm temperature setpoint or low alarm pressure 

setpoint as constant values in the calculations specified in §1065.645. For your testing, you may 

also use a nominal ptotal, which you may estimate as the dryer’s lowest absolute pressure 

expected during testing. 

(ii) Thermal chiller. You may use a thermal chiller upstream of some gas analyzers and storage 

media. You may not use a thermal chiller upstream of a THC measurement system for 

Deleted: 2

Deleted: 4-
compression-ignition engines, two-stroke spark-ignition engines, or four-stroke spark-ignition 

engines at or below 19 kW. If you use a thermal chiller upstream of an NO2-to-NO converter or 

in a sampling system without an NO2-to-NO converter, the chiller must meet the NO2 lossperformance check specified in §1065.376. Monitor the dewpoint, Tdew, and absolute pressure, 

ptotal, downstream of a thermal chiller. You may use continuously recorded values of Tdew and 

ptotal in the amount of water calculations specified in §1065.645. If it is valid to assume the 

degree of saturation in the thermal chiller, you may calculate Tdew based on the known chiller 

performance and continuous monitoring of chiller temperature, Tchiller. If it is valid to assume a 

constant temperature offset between Tchiller and Tdew, due to a known and fixed amount of sample 

reheat between the chiller outlet and the temperature measurement location, you may factor in 

this assumed temperature offset value into emission calculations. If we ask for it, you must show 

by engineering analysis or by data the validity of any assumptions allowed by this paragraph 

(e)(2)(ii). For our testing we may use average temperature and pressure values over the test 

interval or a nominal pressure value that we estimate as the dryer’s average pressure expected 

during testing as constant values in the calculations specified in §1065.645. For your testing you 

may use the maximum temperature and minimum pressure values observed during a test interval 

or duty cycle or the high alarm temperature setpoint and the low alarm pressure setpoint as 

constant values in the amount of water calculations specified in §1065.645. For your testing you 

may also use a nominal ptotal, which you may estimate as the dryer’s lowest absolute pressure 

expected during testing. 

(3) Sample pumps. You may use sample pumps upstream of an analyzer or storage medium for 

any gas. Use sample pumps with inside surfaces of 300 series stainless steel, PTFE, or any other 

material that you demonstrate has better properties for emission sampling. For some sample 

pumps, you must control temperatures, as follows: 

(i) If you use a NOx sample pump upstream of either an NO2-to-NO converter that meets 

§1065.378 or a chiller that meets §1065.376, it must be heated to prevent aqueous condensation. 

(ii) For testing compression-ignition engines, 2-stroke spark-ignition engines, or four-stroke 

spark-ignition engines at or below 19 kW, if you use a THC sample pump upstream of a THC 

analyzer or storage medium, its inner surfaces must be heated to a tolerance of (191 ±11) C. 

(4) Ammonia Scrubber. You may use ammonia scrubbers for any or all gaseous sampling 

systems to prevent interference with NH3, poisoning of the NO2-to-NO converter, and deposits in 

the sampling system or analyzers. Follow the ammonia scrubber manufacturer’s 

recommendations or use good engineering judgment in applying ammonia scrubbers. 

(f) Optional sample-conditioning components for PM sampling. You may use the following 

sample-conditioning components to prepare PM samples for analysis, as long as you do not 

install or use them in a way that adversely affects your ability to show that your engines comply 

with the applicable PM emission standards. You may condition PM samples to minimize 

positive and negative biases to PM results, as follows: 

(1) PM preclassifier. You may use a PM preclassifier to remove large-diameter particles. The 

PM preclassifier may be either an inertial impactor or a cyclonic separator. It must be 

constructed of 300 series stainless steel. The preclassifier must be rated to remove at least 50 % 

of PM at an aerodynamic diameter of 10 m and no more than 1 % of PM at an aerodynamic 

diameter of 1 m over the range of flow rates for which you use it. Follow the preclassifier 

manufacturer’s instructions for any periodic servicing that may be necessary to prevent a buildup 

of PM. Install the preclassifier in the dilution system downstream of the last dilution stage. 

Configure the preclassifier outlet with a means of bypassing any PM sample media so the 

Deleted: 2

Deleted: 4-

Deleted: 4-
preclassifier flow may be stabilized before starting a test. Locate PM sample media within 75 

cm downstream of the preclassifier’s exit. You may not use this preclassifier if you use a PM 

probe that already has a preclassifier. For example, if you use a hat-shaped preclassifier that is 

located immediately upstream of the probe in such a way that it forces the sample flow to change 

direction before entering the probe, you may not use any other preclassifier in your PM sampling 

system. 

(2) Other components. You may request to use other PM conditioning components upstream of 

a PM preclassifier, such as components that condition humidity or remove gaseous-phase 

hydrocarbons from the diluted exhaust stream. You may use such components only if we 

approve them under §1065.10. 

§1065.150 Continuous sampling. 

You may use continuous sampling techniques for measurements that involve raw or dilute 

sampling. Make sure continuous sampling systems meet the specifications in §1065.145. Make 

sure continuous analyzers meet the specifications in subparts C and D of this part. 

§1065.170 Batch sampling for gaseous and PM constituents. 

Batch sampling involves collecting and storing emissions for later analysis. Examples of batch 

sampling include collecting and storing gaseous emissions in a bag or collecting and storing PM 

on a filter. You may use batch sampling to store emissions that have been diluted at least once in 

some way, such as with CVS, PFD, or BMD. You may use batch-sampling to store undiluted 

emissions. 

(a) Sampling methods. If you extract from a constant-volume flow rate, sample at a constantvolume flow rate as follows: 

(1) Verify proportional sampling after an emission test as described in §1065.545. Use good 

engineering judgment to select storage media that will not significantly change measured 

emission levels (either up or down). For example, do not use sample bags for storing emissions 

if the bags are permeable with respect to emissions or if they off gas emissions to the extent that 

it affects your ability to demonstrate compliance with the applicable gaseous emission standards. 

As another example, do not use PM filters that irreversibly absorb or adsorb gases to the extent 

that it affects your ability to demonstrate compliance with the applicable PM emission standard. 

(2) You must follow the requirements in §1065.140(e)(2) related to PM dilution ratios. For each 

filter, if you expect the net PM mass on the filter to exceed 400 μg, assuming a 38 mm diameter 

filter stain area, you may take the following actions in sequence: 

(i) For discrete-mode testing only, you may reduce sample time as needed to target a filter 

loading of 400 μg, but not below the minimum sample time specified in the standard-setting part. 

(ii) Reduce filter face velocity as needed to target a filter loading of 400 μg, down to 50 cm/s or 

less. 

(iii) Increase overall dilution ratio above the values specified in §1065.140(e)(2) to target a filter 

loading of 400 μg. 

(b) Gaseous sample storage media. Store gas volumes in sufficiently clean containers that 

minimally off-gas or allow permeation of gases. Use good engineering judgment to determine 

acceptable thresholds of storage media cleanliness and permeation. To clean a container, you 

may repeatedly purge and evacuate a container and you may heat it. Use a flexible container 

(such as a bag) within a temperature-controlled environment, or use a temperature controlled 

rigid container that is initially evacuated or has a volume that can be displaced, such as a piston 

Deleted: Validate 
and cylinder arrangement. Use containers meeting the specifications in the Table1 of this section, 

noting that you may request to use other container materials under §1065.10. Sample 

temperatures must stay within the following ranges for each container material: 

(1) Up to 40 °C for TedlarTM and KynarTM.

(2) (191 ±11) °C for TeflonTM and 300 series stainless steel used with measuring THC or NMHC 

from compression-ignition engines, two-stroke spark-ignition engines, and four-stroke sparkignition engines at or below 19 kW. For all other engines and pollutants, these materials are 

good for sample temperatures up to 202 °C.

Table 1 of §1065.170– Container Materials for Gaseous Batch Sampling 

Emissions 

Engine type

Compression-ignition 

Two-stroke spark-ignition 

Four-stroke spark-ignition <19 kW 

All other engines 

CO, CO2, O2, 

CH4, C2H6, C3H8, 

NO, NO2

1

, N2O

TedlarTM2, KynarTM2, TeflonTM3, or 

300 series stainless steel3

TedlarTM2

, KynarTM2, TeflonTM3, 

or 300 series stainless steel3

THC, NMHC TeflonTM4

 or 

300 series stainless steel4

TedlarTM2

, KynarTM2, TeflonTM3, 

or 300 series stainless steel3

(c) PM sample media. Apply the following methods for sampling particulate emissions: 

(1) If you use filter-based sampling media to extract and store PM for measurement, your 

procedure must meet the following specifications: 

(i) If you expect that a filter’s total surface concentration of PM will exceed 400 μg, assuming a 

38 mm diameter filter stain area, for a given test interval, you may use filter media with a 

minimum initial collection efficiency of 98 %; otherwise you must use a filter media with a 

minimum initial collection efficiency of 99.7 %. Collection efficiency must be measured as 

described in ASTM D2986 (incorporated by reference in §1065.1010), though you may rely on 

the sample-media manufacturer’s measurements reflected in their product ratings to show that 

you meet this requirement. 

(ii) The filter must be circular, with an overall diameter of 46.50 ±0.6 mm and an exposed 

diameter of at least 38 mm. See the cassette specifications in paragraph (c)(1)(vii) of this section. 

(iii) We highly recommend that you use a pure PTFE filter material that does not have any flowthrough support bonded to the back and has an overall thickness of 40 ±20 m. An inert 

polymer ring may be bonded to the periphery of the filter material for support and for sealing 

between the filter cassette parts. We consider Polymethylpentene (PMP) and PTFE inert 

materials for a support ring, but other inert materials may be used. See the cassette specifications 

in paragraph (c)(1)(vii) of this section. We allow the use of PTFE-coated glass fiber filter 

material, as long as this filter media selection does not affect your ability to demonstrate 

compliance with the applicable standards, which we base on a pure PTFE filter material. Note 

that we will use pure PTFE filter material for compliance testing, and we may require you to use 

pure PTFE filter material for any compliance testing we require, such as for selective 

enforcement audits. 

(iv) You may request to use other filter materials or sizes under the provisions of §1065.10. 

Deleted: following t

Deleted: :

Deleted: Container Materials

Deleted: s

Deleted: 

Deleted: 4

Deleted: 1As long as you prevent aqueous 

condensation in storage container.¶

2

Up to 40 °C.¶

3

Up to 202 °C.¶

4

At (191 ±11) °C.¶

Deleted: -95a
(v) To minimize turbulent deposition and to deposit PM evenly on a filter, use a filter holder with 

a 12.5° (from center) divergent cone angle to transition from the transfer-line inside diameter to 

the exposed diameter of the filter face. Use 300 series stainless steel for this transition. 

(vi) Maintain a filter face velocity near 100 cm/s with less than 5% of the recorded flow values 

exceeding 100 cm/s, unless you expect the net PM mass on the filter to exceed 400 μg, assuming 

a 38 mm diameter filter stain area. Measure face velocity as the volumetric flow rate of the 

sample at the pressure upstream of the filter and temperature of the filter face as measured in 

§1065.140(e), divided by the filter's exposed area. You may use the exhaust stack or CVS tunnel 

pressure for the upstream pressure if the pressure drop through the PM sampler up to the filter is 

less than 2 kPa. 

(vii) Use a clean cassette designed to the specifications of Figure 1 of §1065.170. In auto 

changer configurations, you may use cassettes of similar design. Cassettes must be made of one 

of the following materials: DelrinTM, 300 series stainless steel, polycarbonate, acrylonitrilebutadiene-styrene (ABS) resin, or conductive polypropylene. We recommend that you keep 

filter cassettes clean by periodically washing or wiping them with a compatible solvent applied 

using a lint-free cloth. Depending upon your cassette material, ethanol (C2H5OH) might be an 

acceptable solvent. Your cleaning frequency will depend on your engine’s PM and HC 

emissions. 

(viii) If you keep the cassette in the filter holder after sampling, prevent flow through the filter 

until either the holder or cassette is removed from the PM sampler. If you remove the cassettes 

from filter holders after sampling, transfer the cassette to an individual container that is covered 

or sealed to prevent communication of semi-volatile matter from one filter to another. If you 

remove the filter holder, cap the inlet and outlet. Keep them covered or sealed until they return 

to the stabilization or weighing environments. 

(ix) The filters should not be handled outside of the PM stabilization and weighing environments 

and should be loaded into cassettes, filter holders, or auto changer apparatus before removal from 

these environments. 

(2) You may use other PM sample media that we approve under §1065.10, including nonfiltering techniques. For example, you might deposit PM on an inert substrate that collects PM 

using electrostatic, thermophoresis, inertia, diffusion, or some other deposition mechanism, as 

approved.
Figure 1 of 1065.170

0.10-0.80 

(TYPICAL)

0.10-0.80 

BETWEEN 

CENTERS 

(TYPICAL) 

IN ADDITION TO TYPICAL RANGES GIVEN FOR PERFORATION  AND PERFORATION PATTERNS, WE RECOMMEND THE FOLLOWING: PERFORATION 0.10-0.20 

PERFORATION SPACING 0.10-0.30 

0.10-0.80 

(TYPICAL)
§1065.190 PM-stabilization and weighing environments for gravimetric analysis. 

(a) This section describes the two environments required to stabilize and weigh PM for 

gravimetric analysis: the PM stabilization environment, where filters are stored before weighing; 

and the weighing environment, where the balance is located. The two environments may share a 

common space. These volumes may be one or more rooms, or they may be much smaller, such 

as a glove box or an automated weighing system consisting of one or more countertop-sized 

environments. 

(b) We recommend that you keep both the stabilization and the weighing environments free of 

ambient contaminants, such as dust, aerosols, or semi-volatile material that could contaminate 

PM samples. We recommend that these environments conform with an “as-built” Class Six clean 

room specification according to ISO 14644-1 (incorporated by reference in §1065.1010); 

however, we also recommend that you deviate from ISO 14644-1 as necessary to minimize air 

motion that might affect weighing. We recommend maximum air-supply and air-return 

velocities of 0.05 m/s in the weighing environment. 

(c) Verify the cleanliness of the PM-stabilization environment using reference filters, as 

described in §1065.390(d). 

(d) Maintain the following ambient conditions within the two environments during all 

stabilization and weighing: 

(1) Ambient temperature and tolerances. Maintain the weighing environment at a tolerance of 

(22 ±1) C. If the two environments share a common space, maintain both environments at a 

tolerance of (22 ±1) C. If they are separate, maintain the stabilization environment at a 

tolerance of (22 ±3) C. 

(2) Dewpoint. Maintain a dewpoint of 9.5 C in both environments. This dewpoint will control 

the amount of water associated with sulfuric acid (H2SO4) PM, such that 1.2216 grams of water 

will be associated with each gram of H2SO4. 

(3) Dewpoint tolerances. If the expected fraction of sulfuric acid in PM is unknown, we 

recommend controlling dewpoint at within ±1 C tolerance. This would limit any dewpointrelated change in PM to less than ±2 %, even for PM that is 50 % sulfuric acid. If you know 

your expected fraction of sulfuric acid in PM, we recommend that you select an appropriate 

dewpoint tolerance for showing compliance with emission standards using the following table as 

a guide: 

Table 1 of §1065.190—Dewpoint tolerance 

as a function of % PM change and % sulfuric acid PM 

Expected sulfuric 

acid fraction of PM 

±0.5 % PM 

mass change

±1 % PM 

mass change

±2 % PM 

mass change

5 % ±3 C ±6 C ±12 C 

50 % ±0.3 C ±0.6 C ±1.2 C 

100 % ±0.15 C ±0.3 C ±0.6 C 

(e) Verify the following ambient conditions using measurement instruments that meet the 

specifications in subpart C of this part: 

(1) Continuously measure dewpoint and ambient temperature. Use these values to determine if 

the stabilization and weighing environments have remained within the tolerances specified in 

paragraph (d) of this section for at least 60 min before weighing sample media (e.g., filters). We 

recommend that you use an interlock that automatically prevents the balance from reporting 
values if either of the environments have not been within the applicable tolerances for the past 60 

min. 

(2) Continuously measure atmospheric pressure within the weighing environment. An 

acceptable alternative is to use a barometer that measures atmospheric pressure outside the 

weighing environment, as long as you can ensure that atmospheric pressure at the balance is 

always within ±100 Pa of that outside environment during weighing operations. Record 

atmospheric pressure as you weigh filters, and use these pressure values to perform the buoyancy 

correction in §1065.690. 

(f) We recommend that you install a balance as follows: 

(1) Install the balance on a vibration-isolation platform to isolate it from external noise and 

vibration. 

(2) Shield the balance from convective airflow with a static-dissipating draft shield that is 

electrically grounded. 

(3) Follow the balance manufacturer’s specifications for all preventive maintenance. 

(4) Operate the balance manually or as part of an automated weighing system. 

(g) Minimize static electric charge in the balance environment, as follows: 

(1) Electrically ground the balance. 

(2) Use 300 series stainless steel tweezers if PM sample media (e.g., filters) must be handled 

manually. 

(3) Ground tweezers with a grounding strap, or provide a grounding strap for the operator such 

that the grounding strap shares a common ground with the balance. Make sure grounding straps 

have an appropriate resistor to protect operators from accidental shock. 

(4) Provide a static-electricity neutralizer that is electrically grounded in common with the 

balance to remove static charge from PM sample media (e.g., filters), as follows: 

(i) You may use radioactive neutralizers such as a Polonium (210Po) source. Replace radioactive 

sources at the intervals recommended by the neutralizer manufacturer. 

(ii) You may use other neutralizers, such as corona-discharge ionizers. If you use a coronadischarge ionizer, we recommend that you monitor it for neutral net charge according to the 

ionizer manufacturer’s recommendations. 

(5) We recommend that you use a device to monitor the static charge of PM sample media (e.g., 

filter) surface. 

(6) We recommend that you neutralize PM sample media (e.g., filters) to within ±2.0 V of 

neutral. Measure static voltages as follows: 

(i) Measure static voltage of PM sample media (e.g., filters) according to the electrostatic 

voltmeter manufacturer’s instructions. 

(ii) Measure static voltage of PM sample media (e.g., filters) while the media is at least 15 cm 

away from any grounded surfaces to avoid mirror image charge interference. 

§1065.195 PM-stabilization environment for in-situ analyzers. 

(a) This section describes the environment required to determine PM in-situ. For in-situ 

analyzers, such as an inertial balance, this is the environment within a PM sampling system that 

surrounds the PM sample media (e.g., filters). This is typically a very small volume. 

(b) Maintain the environment free of ambient contaminants, such as dust, aerosols, or semivolatile material that could contaminate PM samples. Filter all air used for stabilization with 

HEPA filters. Ensure that HEPA filters are installed properly so that background PM does not 

leak past the HEPA filters. 
(c) Maintain the following thermodynamic conditions within the environment before measuring 

PM: 

(1) Ambient temperature. Select a nominal ambient temperature, Tamb, between (42 and 52) C. 

Maintain the ambient temperature within ±1.0 C of the selected nominal value. 

(2) Dewpoint. Select a dewpoint, Tdew, that corresponds to Tamb such that Tdew = (0.95·Tamb - 

11.40) C. The resulting dewpoint will control the amount of water associated with sulfuric acid 

(H2SO4) PM, such that 1.1368 grams of water will be associated with each gram of H2SO4. For 

example, if you select a nominal ambient temperature of 47 C, set a dewpoint of 33.3 C. 

(3) Dewpoint tolerance. If the expected fraction of sulfuric acid in PM is unknown, we 

recommend controlling dewpoint within ±1.0 C. This would limit any dewpoint-related change 

in PM to less than ±2 %, even for PM that is 50 % sulfuric acid. If you know your expected 

fraction of sulfuric acid in PM, we recommend that you select an appropriate dewpoint tolerance 

for showing compliance with emission standards using Table 1 of §1065.190 as a guide: 

(4) Absolute pressure. Use good engineering judgment to maintain a tolerance of absolute 

pressure if your PM measurement instrument requires it. 

(d) Continuously measure dewpoint, temperature, and pressure using measurement instruments 

that meet the PM-stabilization environment specifications in subpart C of this part. Use these 

values to determine if the in-situ stabilization environment is within the tolerances specified in 

paragraph (c) of this section. Do not use any PM quantities that are recorded when any of these 

parameters exceed the applicable tolerances. 

(e) If you use an inertial PM balance, we recommend that you install it as follows: 

(1) Isolate the balance from any external noise and vibration that is within a frequency range that 

could affect the balance. 

(2) Follow the balance manufacturer’s specifications. 

(f) If static electricity affects an inertial balance, you may use a static neutralizer, as follows: 

(1) You may use a radioactive neutralizer such as a Polonium (210Po) source or a Krypton (85Kr) 

source. Replace radioactive sources at the intervals recommended by the neutralizer 

manufacturer. 

(2) You may use other neutralizers, such as a corona-discharge ionizer. If you use a coronadischarge ionizer, we recommend that you monitor it for neutral net charge according to the 

ionizer manufacturer’s recommendations.
Subpart C—Measurement Instruments

§1065.201 Overview and general provisions. 

(a) Scope. This subpart specifies measurement instruments and associated system requirements 

related to emission testing in a laboratory or similar environment and in the field. This includes 

laboratory instruments and portable emission measurement systems (PEMS) for measuring 

engine parameters, ambient conditions, flow-related parameters, and emission concentrations. 

(b) Instrument types. You may use any of the specified instruments as described in this subpart 

to perform emission tests. If you want to use one of these instruments in a way that is not 

specified in this subpart, or if you want to use a different instrument, you must first get us to 

approve your alternate procedure under §1065.10. Where we specify more than one instrument 

for a particular measurement, we may identify which instrument serves as the reference for 

comparing with an alternate procedure. You may generally use instruments with compensation 

algorithms that are functions of other gaseous measurements and the engine’s known or assumed

fuel properties. The target value for any compensation algorithm is 0 % (that is, no bias high and 

no bias low), regardless of the uncompensated signal’s bias.

(c) Measurement systems. Assemble a system of measurement instruments that allows you to 

show that your engines comply with the applicable emission standards, using good engineering 

judgment. When selecting instruments, consider how conditions such as vibration, temperature, 

pressure, humidity, viscosity, specific heat, and exhaust composition (including trace 

concentrations) may affect instrument compatibility and performance. 

(d) Redundant systems. For all measurement instruments described in this subpart, you may use 

data from multiple instruments to calculate test results for a single test. If you use redundant 

systems, use good engineering judgment to use multiple measured values in calculations or to 

disregard individual measurements. Note that you must keep your results from all 

measurements. This requirement applies whether or not you actually use the measurements in 

your calculations. 

(e) Range. You may use an instrument’s response above 100 % of its operating range if this 

does not affect your ability to show that your engines comply with the applicable emission 

standards. Note that we require additional testing and reporting if an analyzer responds above 

100 % of its range. Auto-ranging analyzers do not require additional testing or reporting. 

(f) Related subparts for laboratory testing. Subpart D of this part describes how to evaluate the 

performance of the measurement instruments in this subpart. In general, if an instrument is 

specified in a specific section of this subpart, its calibration and verifications are typically 

specified in a similarly numbered section in subpart D of this part. For example, §1065.290 

gives instrument specifications for PM balances and §1065.390 describes the corresponding 

calibrations and verifications. Note that some instruments also have other requirements in other 

sections of subpart D of this part. Subpart B of this part identifies specifications for other types 

of equipment, and subpart H of this part specifies engine fluids and analytical gases. 

(g) Field testing and testing with PEMS. Subpart J of this part describes how to use these and 

other measurement instruments for field testing and other PEMS testing. 

(h) Recommended practices. This subpart identifies a variety of recommended but not required 

practices for proper measurements. We believe in most cases it is necessary to follow these 

recommended practices for accurate and repeatable measurements. However, we do not 

specifically require you to follow these recommended practices to perform a valid test, as long as 

you meet the required calibrations and verifications of measurement systems specified in subpart 

Deleted: , as described in §1065.25

Deleted: See §1065.550. 
D of this part. Similarly, we are not required to follow all recommended practices, as long as we 

meet the required calibrations and verifications. Our decision to follow or not follow a given 

recommendation when we perform a test does not depend on whether you followed it during 

your testing. 

§1065.202 Data updating, recording, and control. 

Your test system must be able to update data, record data and control systems related to operator 

demand, the dynamometer, sampling equipment, and measurement instruments. Use data 

acquisition and control systems that can record at the specified minimum frequencies, as follows: 

Table 1 of §1065.202–Data recording and control minimum frequencies 

Applicable 

Test 

Protocol 

Section 

Measured Values 

Minimum 

Command 

and Control 

Frequency 

Minimum 

Recording 

Frequency 

§1065.510 Speed and torque during an engine step-map 1 Hz 1 mean value 

per step 

§1065.510 Speed and torque during an engine sweepmap 5 Hz 1 Hz means 

§1065.514 

§1065.530 

Transient duty cycle reference and feedback 

speeds and torques 5 Hz 1 Hz means 

§1065.514 

§1065.530 

Steady-state and ramped-modal duty cycle 

reference and feedback speeds and torques 1 Hz 1 Hz 

§1065.520 

§1065.530 

§1065.550 

Continuous concentrations of raw or dilute 

analyzers N/A 1 Hz 

§1065.520 

§1065.530 

§1065.550 

Batch concentrations of raw or dilute 

analyzers N/A 

1 mean value 

per test 

interval 

§1065.530 

§1065.545 

Diluted exhaust flow rate from a CVS with 

a heat exchanger upstream of the flow 

measurement 

N/A 1 Hz 

§1065.530 

§1065.545 

Diluted exhaust flow rate from a CVS 

without a heat exchanger upstream of the 

flow measurement 

N/A 1 Hz means 

§1065.530 

§1065.545 Intake-air or raw-exhaust flow rate N/A 1 Hz means 

§1065.530 

§1065.545 Dilution air if actively controlled 5 Hz 1 Hz means 

§1065.530 

§1065.545 

Sample flow from a CVS that has a heat 

exchanger 1 Hz 1 Hz 

§1065.530 

§1065.545 

Sample flow from a CVS does not have a 

heat exchanger 5 Hz 1 Hz means

§1065.205 Performance specifications for measurement instruments. 

Deleted: testing your engine is not dependent 

Deleted: or not 

Deleted: 5 Hz
Your test system as a whole must meet all the calibrations, verifications, and test-validation 

criteria specified outside of this section for laboratory testing or field testing, as applicable. We 

recommend that your instruments meet the specifications in Table 1 of this section for all ranges 

you use for testing. We also recommend that you keep any documentation you receive from 

instrument manufacturers showing that your instruments meet the specifications in Table 1 of 

this section. 

Deleted: applicable 

Deleted: specified in subparts D and F of this part 

or subpart J of this part for using PEMS and for 

performing field testing.
Table 1 of §1065.205–Recommended performance specifications for measurement instruments 

Measurement Instrument 

Measured 

quantity 

symbol 

Complete System 

Rise time (t10-90) and 

Fall time (t90-10)

a

Recording 

update frequency Accuracyb Repeatabilityb Noiseb

Engine speed transducer 

fn 1 s 1 Hz means 2 % of pt. or 0.5 % of max. 1 % of pt. or 0.25 % of max. 0.05 % of max 

Engine torque transducer T 1 s 1 Hz means 2 % of pt. or 1 % of max. 1 % of pt. or 0.5 % of max 0.05 % of max. Electrical work (active-power meter) W 1 s 1 Hz means 2 % of pt. or 0.5 % of max. 1 % of pt. or 0.25 % of max. 0.05 % of max General pressure transducer (not a part of another instrument) p 5 s 1 Hz 2 % of pt. or 1 % of max. 1 % of pt. or 0.5 % of max. 0.1 % of max Atmospheric pressure meter used for PM-stabilization and balance environments 

patmos 50 s 5 times per hour 50 Pa 25 Pa 5 Pa 

General purpose atmospheric pressure meter patmos 50 s 5 times per hour 250 Pa 100Pa 50 Pa Temperature sensor for PMstabilization and balance environments 

T 50 s 0.1 Hz 0.25 K 0.1 K 0.1 K 

Other temperature sensor (not a part of another instrument) T 10 s 0.5 Hz 0.4 % of pt. K or 0.2 % of max. K 0.2 % of pt. K or 0.1 % of max. K 0.1 % of max Dewpoint sensor for intake air, PM-stabilization and balance environments 

Tdew 50 s 0.1 Hz 0.25 K 0.1 K 0.02 K 

Other dewpoint sensor Tdew 50 s 0.1 Hz 1 K 0.5 K 0.1 K Fuel flow meterc (Fuel totalizer) 

m 5 s (N/A) 1 Hz (N/A) 2 % of pt. or 1.5 % of max. 1 % of pt. or 0.75 % of max. 0.5 % of max. 

Total diluted exhaust meter (CVS) c (With heat exchanger before meter) n 1 s (5 s) 1 Hz means (1 Hz) 2 % of pt. or 1.5 % of max. 1 % of pt. or 0.75 % of max. 1 % of max. Dilution air, inlet air, exhaust, and sample flow metersc n 1 s 1 Hz means of 5 Hz samples 2.5 % of pt. or 1.5 % of max. 1.25 % of pt. or 0.75 % of max. 1 % of max. Continuous gas analyzer x 5 s 1 Hz 2 % of pt. or 2 % of meas. 1 % of pt. or 1 % of meas. 1 % of max. Batch gas analyzer x N/A N/A 2 % of pt. or 2 % of meas. 1 % of pt. or 1 % of meas. 1 % of max. Gravimetric PM balance 

mPM N/A N/A See §1065.790 0.5 g N/A 

Inertial PM balance 

mPM 5 s 1 Hz 2 % of pt. or 2 % of meas. 1 % of pt. or 1 % of meas. 0.2 % of max. 

a The performance specifications identified in the table apply separately for rise time and fall time. b Accuracy, repeatability, and noise are all determined with the same collected data, as described in §1065.305, and based on absolute values. “pt.” refers to the overall flowweighted mean value expected at the standard; “max.” refers to the peak value expected at the standard over any test interval, not the maximum of the instrument’s range; “meas” 

refers to the actual flow-weighted mean measured over any test interval. 

c The procedure for accuracy, repeatability and noise measurement described in §1065.305 may be modified for flow meters to allow noise to be measured at the lowest calibrated 

value instead of zero flow rate.
MEASUREMENT OF ENGINE PARAMETERS AND AMBIENT CONDITIONS 

§1065.210 Work input and output sensors. 

(a) Application. Use instruments as specified in this section to measure work inputs and outputs 

during engine operation. We recommend that you use sensors, transducers, and meters that meet 

the specifications in Table 1 of §1065.205. Note that your overall systems for measuring work 

inputs and outputs must meet the linearity verifications in §1065.307. We recommend that you 

measure work inputs and outputs where they cross the system boundary as shown in Figure 1 of 

§1065.210. The system boundary is different for air-cooled engines than for liquid-cooled 

engines. If you choose to measure work before or after a work conversion, relative to the system 

boundary, use good engineering judgment to estimate any work-conversion losses in a way that 

avoids overestimation of total work. For example, if it is impractical to instrument the shaft of 

an exhaust turbine generating electrical work, you may decide to measure its converted electrical 

work. As another example, you may decide to measure the tractive (i.e., electrical output) power 

of a locomotive, rather than the brake power of the locomotive engine. In these cases, divide the 

electrical work by accurate values of electrical generator efficiency ( <1), or assume an 

efficiency of 1 ( =1), which would over-estimate brake-specific emissions. For the example of 

using locomotive tractive power with a generator efficiency of 1 ( =1), this means using the 

tractive power as the brake power in emission calculations. Do not underestimate any work 

conversion efficiencies for any components outside the system boundary that do not return work 

into the system boundary. And do not overestimate any work conversion efficiencies for 

components outside the system boundary that do return work into the system boundary. In all 

cases, ensure that you are able to accurately demonstrate compliance with the applicable 

standards. 
Figure 1065.210-1: Work inputs, outputs, and system boundaries 

Fuel

Intake Air Exhaust

+Shaft Work

Liquid

Cooled

Engine

Crankshaft

Liquid Coolant

+Shaft Work

-Electrical Work

+Electrical Work

Thermoelectric

G

M

+Electrical Work

Net (+/-) Electrical Work

M

HX

+ -

Batt.

T

T

C

Net (+/-) Pump/

Compressor Work

Acc.

C T G M

C=Compressor

T=Turbine

G=Generator

M=Motor

C HX=Heat Exchanger

System Boundary

Fuel

Intake Air Exhaust

+Shaft Work

Liquid

Cooled

Engine

Crankshaft

Liquid Coolant

+Shaft Work

-Electrical Work

+Electrical Work

Thermoelectric

G

M

+Electrical Work

Net (+/-) Electrical Work

M

HX

+ -

Batt.

T

T

C

Net (+/-) Pump/

Compressor Work

Acc.

C T G M

C=Compressor

T=Turbine

G=Generator

M=Motor

C HX=Heat Exchanger

System Boundary

Fuel

Intake Air Exhaust

+Shaft Work

Liquid

Cooled

Engine

Crankshaft

Liquid Coolant

+Shaft Work

-Electrical Work

+Electrical Work

Thermoelectric

G

M

+Electrical Work

Net (+/-) Electrical Work

M

HX

+ -

Batt.

T

T

C

Net (+/-) Pump/

Compressor Work

Acc.

C T G M

C=Compressor

T=Turbine

G=Generator

M=Motor

C HX=Heat Exchanger

System Boundary

Fuel

Intake Air Exhaust

+Shaft Work

Air

Cooled

Engine

Crankshaft

+Shaft Work

-Electrical Work

+Electrical Work

Thermoelectric

G

+Electrical Work

+ - Net (+/-) Electrical Work

Batt.

M

HX

T

T

C

Net (+/-) Pump/

Compressor Work

Acc.

C T

G

M

C

C=Compressor

T=Turbine

G=Generator

M=Motor

HX=Heat Exchanger

System Boundary

Fuel

Intake Air Exhaust

+Shaft Work

Air

Cooled

Engine

Crankshaft

+Shaft Work

-Electrical Work

+Electrical Work

Thermoelectric

G

+Electrical Work

+ - Net (+/-) Electrical Work

Batt.

M

HX

T

T

C

Net (+/-) Pump/

Compressor Work

Acc.

C T

G

M

C

C=Compressor

T=Turbine

G=Generator

M=Motor

HX=Heat Exchanger

System Boundary

Fuel

Intake Air Exhaust

+Shaft Work

Air

Cooled

Engine

Crankshaft

+Shaft Work

-Electrical Work

+Electrical Work

Thermoelectric

G

+Electrical Work

+ - Net (+/-) Electrical Work

Batt.

M

HX

T

T

C

Net (+/-) Pump/

Compressor Work

Acc.

C T

G

M

C

C=Compressor

T=Turbine

G=Generator

M=Motor

HX=Heat Exchanger

System Boundary
(b) Shaft work. Use speed and torque transducer outputs to calculate total work according to 

§1065.650. 

(1) Speed. Use a magnetic or optical shaft-position detector with a resolution of at least 60 

counts per revolution, in combination with a frequency counter that rejects common-mode noise. 

(2) Torque. You may use a variety of methods to determine engine torque. As needed, and based 

on good engineering judgment, compensate for torque induced by the inertia of accelerating and 

decelerating components connected to the flywheel, such as the drive shaft and dynamometer 

rotor. Use any of the following methods to determine engine torque: 

(i) Measure torque by mounting a strain gage or similar instrument in-line between the engine 

and dynamometer. 

(ii) Measure torque by mounting a strain gage or similar instrument on a lever arm connected to 

the dynamometer housing. 

(iii) Calculate torque from internal dynamometer signals, such as armature current, as long as 

you calibrate this measurement as described in §1065.310. 

(c) Electrical work. Use a watt-hour meter output to calculate total work according to 

§1065.650. Use a watt-hour meter that outputs active power (kW). Watt-hour meters typically 

combine a Wheatstone bridge voltmeter and a Hall-effect clamp-on ammeter into a single 

microprocessor-based instrument that analyzes and outputs several parameters, such as 

alternating or direct current voltage (V), current (A), power factor (pf), apparent power (VA), 

reactive power (VAR), and active power (W). 

(d) Pump, compressor or turbine work. Use pressure transducer and flow-meter outputs to 

calculate total work according to §1065.650. For flow meters, see §1065.220 through 

§1065.248. 

§1065.215 Pressure transducers, temperature sensors, and dewpoint sensors. 

(a) Application. Use instruments as specified in this section to measure pressure, temperature, 

and dewpoint. 

(b) Component requirements. We recommend that you use pressure transducers, temperature 

sensors, and dewpoint sensors that meet the specifications in Table 1 of §1065.205. Note that 

your overall systems for measuring pressure, temperature, and dewpoint must meet the 

calibration and verifications in §1065.315. 

(c) Temperature. For PM-balance environments or other precision temperature measurements 

over a narrow temperature range, we recommend thermistors. For other applications we 

recommend thermocouples that are not grounded to the thermocouple sheath. You may use 

other temperature sensors, such as resistive temperature detectors (RTDs). 

(d) Pressure. Pressure transducers must be located in a temperature-controlled environment, or 

they must compensate for temperature changes over their expected operating range. Transducer 

materials must be compatible with the fluid being measured. For atmospheric pressure or other 

precision pressure measurements, we recommend either capacitance-type, quartz crystal, or 

laser-interferometer transducers. For other applications, we recommend either strain gage or 

capacitance-type pressure transducers. You may use other pressure-measurement instruments, 

such as manometers, where appropriate. 

(e) Dewpoint. For PM-stabilization environments, we recommend chilled-surface hygrometers, 

which include chilled mirror detectors and chilled surface acoustic wave (SAW) detectors. For 
other applications, we recommend thin-film capacitance sensors. You may use other dewpoint 

sensors, such as a wet-bulb/dry-bulb psychrometer, where appropriate. 

FLOW-RELATED MEASUREMENTS 

§1065.220 Fuel flow meter. 

(a) Application. You may use fuel flow in combination with a chemical balance of fuel, inlet air, 

and raw exhaust to calculate raw exhaust flow as described in §1065.655(e), as follows: 

(1) Use the actual value of calculated raw exhaust flow rate in the following cases: 

(i) For multiplying raw exhaust flow rate with continuously sampled concentrations. 

(ii) For multiplying total raw exhaust flow with batch-sampled concentrations. 

(iii) For calculating the dilution air flow for background correction as described in §1065.667. 

(2) In the following cases, you may use a fuel flow meter signal that does not give the actual 

value of raw exhaust, as long as it is linearly proportional to the exhaust molar flow rate’s actual 

calculated value: 

(i) For feedback control of a proportional sampling system, such as a partial-flow dilution 

system. 

(ii) For multiplying with continuously sampled gas concentrations, if the same signal is used in a 

chemical-balance calculation to determine work from brake-specific fuel consumption and fuel 

consumed. 

(b) Component requirements. We recommend that you use a fuel flow meter that meets the 

specifications in Table 1 of §1065.205. We recommend a fuel flow meter that measures mass 

directly, such as one that relies on gravimetric or inertial measurement principles. This may 

involve using a meter with one or more scales for weighing fuel or using a Coriolis meter. Note 

that your overall system for measuring fuel flow must meet the linearity verification in 

§1065.307 and the calibration and verifications in §1065.320. 

(c) Recirculating fuel. In any fuel-flow measurement, account for any fuel that bypasses the 

engine or returns from the engine to the fuel storage tank. 

(d) Flow conditioning. For any type of fuel flow meter, condition the flow as needed to prevent 

wakes, eddies, circulating flows, or flow pulsations from affecting the accuracy or repeatability 

of the meter. You may accomplish this by using a sufficient length of straight tubing (such as a 

length equal to at least 10 pipe diameters) or by using specially designed tubing bends, 

straightening fins, or pneumatic pulsation dampeners to establish a steady and predictable 

velocity profile upstream of the meter. Condition the flow as needed to prevent any gas bubbles 

in the fuel from affecting the fuel meter. 

§1065.225 Intake-air flow meter. 

(a) Application. You may use an intake-air flow meter in combination with a chemical balance 

of fuel, inlet air, and exhaust to calculate raw exhaust flow as described in §1065.655(e) and (f), 

as follows: 

(1) Use the actual value of calculated raw exhaust in the following cases: 

(i) For multiplying raw exhaust flow rate with continuously sampled concentrations. 

(ii) For multiplying total raw exhaust flow with batch-sampled concentrations.

(iii) For validating minimum dilution ratio for PM batch sampling as described in §1065.546.

Deleted: raw 

Deleted: 650
(iv) For calculating the dilution air flow for background correction as described in §1065.667.

(2) In the following cases, you may use an intake-air flow meter signal that does not give the 

actual value of raw exhaust, as long as it is linearly proportional to the exhaust flow rate’s actual 

calculated value: 

(i) For feedback control of a proportional sampling system, such as a partial-flow dilution 

system. 

(ii) For multiplying with continuously sampled gas concentrations, if the same signal is used in a 

chemical-balance calculation to determine work from brake-specific fuel consumption and fuel 

consumed. 

(b) Component requirements. We recommend that you use an intake-air flow meter that meets 

the specifications in Table 1 of §1065.205. This may include a laminar flow element, an 

ultrasonic flow meter, a subsonic venturi, a thermal-mass meter, an averaging Pitot tube, or a 

hot-wire anemometer. Note that your overall system for measuring intake-air flow must meet 

the linearity verification in §1065.307 and the calibration in §1065.325. 

(c) Flow conditioning. For any type of intake-air flow meter, condition the flow as needed to 

prevent wakes, eddies, circulating flows, or flow pulsations from affecting the accuracy or 

repeatability of the meter. You may accomplish this by using a sufficient length of straight 

tubing (such as a length equal to at least 10 pipe diameters) or by using specially designed tubing 

bends, orifice plates or straightening fins to establish a predictable velocity profile upstream of 

the meter. 

§1065.230 Raw exhaust flow meter. 

(a) Application. You may use measured raw exhaust flow, as follows: 

(1) Use the actual value of calculated raw exhaust in the following cases: 

(i) Multiply raw exhaust flow rate with continuously sampled concentrations. 

(ii) Multiply total raw exhaust with batch sampled concentrations. 

(2) In the following cases, you may use a raw exhaust flow meter signal that does not give the 

actual value of raw exhaust, as long as it is linearly proportional to the exhaust flow rate’s actual 

calculated value: 

(i) For feedback control of a proportional sampling system, such as a partial-flow dilution 

system. 

(ii) For multiplying with continuously sampled gas concentrations, if the same signal is used in a 

chemical-balance calculation to determine work from brake-specific fuel consumption and fuel 

consumed. 

(b) Component requirements. We recommend that you use a raw-exhaust flow meter that meets 

the specifications in Table 1 of §1065.205. This may involve using an ultrasonic flow meter, a 

subsonic venturi, an averaging Pitot tube, a hot-wire anemometer, or other measurement 

principle. This would generally not involve a laminar flow element or a thermal-mass meter. 

Note that your overall system for measuring raw exhaust flow must meet the linearity 

verification in §1065.307 and the calibration and verifications in §1065.330. Any raw-exhaust 

meter must be designed to appropriately compensate for changes in the raw exhaust’s 

thermodynamic, fluid, and compositional states. 

(c) Flow conditioning. For any type of raw exhaust flow meter, condition the flow as needed to 

prevent wakes, eddies, circulating flows, or flow pulsations from affecting the accuracy or 

Deleted: (iii) For validating minimum dilution 

ratio for PM batch sampling as described in 

§1065.546.¶

(iv) For calculating the dilution air flow for 

background correction as described in §1065.667.¶
repeatability of the meter. You may accomplish this by using a sufficient length of straight 

tubing (such as a length equal to at least 10 pipe diameters) or by using specially designed tubing 

bends, orifice plates or straightening fins to establish a predictable velocity profile upstream of 

the meter. 

(d) Exhaust cooling. You may cool raw exhaust upstream of a raw-exhaust flow meter, as long 

as you observe all the following provisions: 

(1) Do not sample PM downstream of the cooling. 

(2) If cooling causes exhaust temperatures above 202 °C to decrease to below 180 °C, do not 

sample NMHC downstream of the cooling for compression-ignition engines, two-stroke sparkignition engines, or four-stroke spark-ignition engines at or below 19 kW. 

(3) The cooling must not cause aqueous condensation. 

§1065.240 Dilution air and diluted exhaust flow meters. 

(a) Application. Use a diluted exhaust flow meter to determine instantaneous diluted exhaust 

flow rates or total diluted exhaust flow over a test interval. You may use the difference between 

a diluted exhaust flow meter and a dilution air meter to calculate raw exhaust flow rates or total 

raw exhaust flow over a test interval. 

(b) Component requirements. We recommend that you use a diluted exhaust flow meter that 

meets the specifications in Table 1 of §1065.205. Note that your overall system for measuring 

diluted exhaust flow must meet the linearity verification in §1065.307 and the calibration and 

verifications in §1065.340 and §1065.341. You may use the following meters: 

(1) For constant-volume sampling (CVS) of the total flow of diluted exhaust, you may use a 

critical-flow venturi (CFV) or multiple critical-flow venturis arranged in parallel, a positivedisplacement pump (PDP), a subsonic venturi (SSV), or an ultrasonic flow meter (UFM). 

Combined with an upstream heat exchanger, either a CFV or a PDP will also function as a 

passive flow controller in a CVS system. However, you may also combine any flow meter with 

any active flow control system to maintain proportional sampling of exhaust constituents. You 

may control the total flow of diluted exhaust, or one or more sample flows, or a combination of 

these flow controls to maintain proportional sampling. 

(2) For any other dilution system, you may use a laminar flow element, an ultrasonic flow meter, 

a subsonic venturi, a critical-flow venturi or multiple critical-flow venturis arranged in parallel, a 

positive-displacement meter, a thermal-mass meter, an averaging Pitot tube, or a hot-wire 

anemometer. 

(c) Flow conditioning. For any type of diluted exhaust flow meter, condition the flow as needed 

to prevent wakes, eddies, circulating flows, or flow pulsations from affecting the accuracy or 

repeatability of the meter. For some meters, you may accomplish this by using a sufficient 

length of straight tubing (such as a length equal to at least 10 pipe diameters) or by using 

specially designed tubing bends, orifice plates or straightening fins to establish a predictable 

velocity profile upstream of the meter. 

(d) Exhaust cooling. You may cool diluted exhaust upstream of a dilute-exhaust flow meter, as 

long as you observe all the following provisions: 

(1) Do not sample PM downstream of the cooling. 

Deleted: 2

Deleted: and 

Deleted: 4

Deleted: spark 

Deleted: If 

Deleted: causes 

Deleted: , do not sample NOx downstream of the 

cooling unless the cooler meets the performance 

verification in §1065.376

Deleted: ¶

(4) If cooling causes aqueous condensation before 

the flow reaches a flow meter, measure dewpoint, 

Tdew and pressure, ptotal at the flow meter inlet. Use 

these values in emission calculations according to 

§1065.650.
(2) If cooling causes exhaust temperatures above 202 °C to decrease to below 180 °C, do not 

sample NMHC downstream of the cooling for compression-ignition engines, two-stroke sparkignition engines, or four-stroke spark-ignition engines at or below 19 kW. 

(3) The cooling must not cause aqueous condensation as described in §1065.140(c)(6). 

§1065.245 Sample flow meter for batch sampling. 

(a) Application. Use a sample flow meter to determine sample flow rates or total flow sampled 

into a batch sampling system over a test interval. You may use the difference between a diluted 

exhaust sample flow meter and a dilution air meter to calculate raw exhaust flow rates or total 

raw exhaust flow over a test interval. 

(b) Component requirements. We recommend that you use a sample flow meter that meets the 

specifications in Table 1 of §1065.205. This may involve a laminar flow element, an ultrasonic 

flow meter, a subsonic venturi, a critical-flow venturi or multiple critical-flow venturis arranged 

in parallel, a positive-displacement meter, a thermal-mass meter, an averaging Pitot tube, or a 

hot-wire anemometer. Note that your overall system for measuring sample flow must meet the 

linearity verification in §1065.307. For the special case where CFVs are used for both the 

diluted exhaust and sample-flow measurements and their upstream pressures and temperatures 

remain similar during testing, you do not have to quantify the flow rate of the sample-flow CFV. 

In this special case, the sample-flow CFV inherently flow-weights the batch sample relative to 

the diluted exhaust CFV. 

(c) Flow conditioning. For any type of sample flow meter, condition the flow as needed to 

prevent wakes, eddies, circulating flows, or flow pulsations from affecting the accuracy or 

repeatability of the meter. For some meters, you may accomplish this by using a sufficient 

length of straight tubing (such as a length equal to at least 10 pipe diameters) or by using 

specially designed tubing bends, orifice plates or straightening fins to establish a predictable 

velocity profile upstream of the meter. 

§1065.248 Gas divider. 

(a) Application. You may use a gas divider to blend calibration gases. 

(b) Component requirements. Use a gas divider that blends gases to the specifications of 

§1065.750 and to the flow-weighted concentrations expected during testing. You may use 

critical-flow gas dividers, capillary-tube gas dividers, or thermal-mass-meter gas dividers. Note 

that your overall gas-divider system must meet the linearity verification in §1065.307. 

CO AND CO2 MEASUREMENTS 

§1065.250 Nondispersive infrared analyzer. 

(a) Application. Use a nondispersive infrared (NDIR) analyzer to measure CO and CO2

concentrations in raw or diluted exhaust for either batch or continuous sampling. 

(b) Component requirements. We recommend that you use an NDIR analyzer that meets the 

specifications in Table 1 of §1065.205. Note that your NDIR-based system must meet the 

calibration and verifications in §§1065.350 and 1065.355 and it must also meet the linearity 

verification in §1065.307. 

Deleted: 2

Deleted: and 4-

Deleted: spark 

Deleted: If 

Deleted: causes 

Deleted: , do not sample NOx downstream of the 

cooling unless the cooler meets the performance 

verification in §1065.376 

Deleted: ¶

(4) If cooling causes aqueous condensation before 

the flow reaches a flow meter, measure dewpoint, 

Tdew and pressure, ptotal at the flow meter inlet. Use 

these values in emission calculations according to 

§1065.650.

Deleted: You may use an NDIR analyzer that has 

compensation algorithms that are functions of other 

gaseous measurements and the engine’s known or 

assumed fuel properties. The target value for any 

compensation algorithm is 0 % (that is, no bias high 

and no bias low), regardless of the uncompensated 

signal’s bias.
HYDROCARBON MEASUREMENTS 

§1065.260 Flame-ionization detector. 

(a) Application. Use a flame-ionization detector (FID) analyzer to measure hydrocarbon 

concentrations in raw or diluted exhaust for either batch or continuous sampling. Determine 

hydrocarbon concentrations on a carbon number basis of one, C1. For measuring THC or THCE 

you must use a FID analyzer. For measuring CH4 you must meet the requirements of paragraph 

(f) of this section. See subpart I of this part for special provisions that apply to measuring 

hydrocarbons when testing with oxygenated fuels. 

(b) Component requirements. We recommend that you use a FID analyzer that meets the 

specifications in Table 1 of §1065.205. Note that your FID-based system for measuring THC, 

THCE, or CH4 must meet all the verifications for hydrocarbon measurement in subpart D of this 

part, and it must also meet the linearity verification in §1065.307. 

(c) Heated FID analyzers. For measuring THC or THCE from compression-ignition engines, 

two-stroke spark-ignition engines, and four-stroke spark-ignition engines at or below 19 kW, you 

must use heated FID analyzers that maintain all surfaces that are exposed to emissions at a 

temperature of (191 ±11) °C. 

(d) FID fuel and burner air. Use FID fuel and burner air that meet the specifications of 

§1065.750. Do not allow the FID fuel and burner air to mix before entering the FID analyzer to 

ensure that the FID analyzer operates with a diffusion flame and not a premixed flame. 

(e) NMHC and NMOG. For demonstrating compliance with NMHC standards, you may either 

measure THC and CH4 and determine NMHC as described in §1065.660(b)(2) or (3), or you 

may measure THC and determine NMHC mass as described in §1065.660(b)(1). See 40 CFR 

1066.665 for methods to demonstrate compliance with NMOG standards for vehicle testing.

(f) CH4. For reporting CH4 or for demonstrating compliance with CH4 standards, you may use a 

FID analyzer with a nonmethane cutter as described in §1065.265 or you may use a GC-FID as 

described in §1065.267. Determine CH4 as described in §1065.660(c). 

§1065.265 Nonmethane cutter. 

(a) Application. You may use a nonmethane cutter to measure CH4 with a FID analyzer. A 

nonmethane cutter oxidizes all nonmethane hydrocarbons to CO2 and H2O. You may use a 

nonmethane cutter for raw or diluted exhaust for batch or continuous sampling. 

(b) System performance. Determine nonmethane-cutter performance as described in §1065.365 

and use the results to calculate CH4 or NMHC emissions in §1065.660. 

(c) Configuration. Configure the nonmethane cutter with a bypass line if it is needed for the 

verification described in §1065.365. 

(d) Optimization. You may optimize a nonmethane cutter to maximize the penetration of CH4

and the oxidation of all other hydrocarbons. You may humidify a sample and you may dilute a 

sample with purified air or oxygen (O2) upstream of the nonmethane cutter to optimize its 

performance. You must account for any sample humidification and dilution in emission 

calculations. 

§1065.267 Gas chromatograph with a flame ionization detector. 

Deleted: You may use a FID analyzer that has 

compensation algorithms that are functions of other 

gaseous measurements and the engine’s known or 

assumed fuel properties. The target value for any 

compensation algorithm is 0 % (that is, no bias high 

and no bias low), regardless of the uncompensated 

signal’s bias.
(a) Application. You may use a gas chromatograph with a flame ionization detector (GC-FID) to 

measure CH4 concentrations of diluted exhaust for batch sampling. While you may also use a 

nonmethane cutter to measure CH4, as described in §1065.265, use a reference procedure based 

on a gas chromatograph for comparison with any proposed alternate measurement procedure 

under §1065.10. 

(b) Component requirements. We recommend that you use a GC-FID that meets the 

specifications in Table 1 of §1065.205 and that the measurement be done according to SAE 

J1151 (incorporated by reference in §1065.1010). The GC-FID must meet the linearity 

verification in §1065.307.

§1065.269 Photoacoustic analyzer for methanol and ethanol.

(a) Application. You may use a photoacoustic analyzer to measure ethanol and/or methanol 

concentrations in diluted exhaust for batch sampling.

(b) Component requirements. We recommend that you use a photoacoustic analyzer that meets 

the specifications in Table 1 of §1065.205. Note that your photoacoustic system must meet the 

calibration and verifications in §1065.369 and it must also meet the linearity verification in 

§1065.307. Use an optical wheel configuration that gives analytical priority to measurement of 

the least stable components in the sample. Select a sample integration time of at least 5 seconds. 

Take into account sample chamber and sample line volumes when determining flush times for 

your instrument.

NOx AND N2O MEASUREMENTS 

§1065.270 Chemiluminescent detector. 

(a) Application. You may use a chemiluminescent detector (CLD) to measure NOx

concentration in raw or diluted exhaust for batch or continuous sampling. We generally accept a 

CLD for NOx measurement, even though it measures only NO and NO2, when coupled with an 

NO2-to-NO converter, since conventional engines and aftertreatment systems do not emit 

significant amounts of NOx species other than NO and NO2. Measure other NOx species if 

required by the standard-setting part. While you may also use other instruments to measure NOx, 

as described in §1065.272, use a reference procedure based on a chemiluminescent detector for 

comparison with any proposed alternate measurement procedure under §1065.10. 

(b) Component requirements. We recommend that you use a CLD that meets the specifications 

in Table 1 of §1065.205. Note that your CLD-based system must meet the quench verification in 

§1065.370 and it must also meet the linearity verification in §1065.307. You may use a heated 

or unheated CLD, and you may use a CLD that operates at atmospheric pressure or under a 

vacuum. 

(c) NO2-to-NO converter. Place upstream of the CLD an internal or external NO2-to-NO 

converter that meets the verification in §1065.378. Configure the converter with a bypass line if 

it is needed to facilitate this verification. 

(d) Humidity effects. You must maintain all CLD temperatures to prevent aqueous 

condensation. If you remove humidity from a sample upstream of a CLD, use one of the 

following configurations: 

Deleted: ,

Deleted: it 

Deleted: also 

Deleted: You may use a CLD that has 

compensation algorithms that are functions of other 

gaseous measurements and the engine’s known or 

assumed fuel properties. The target value for any 

compensation algorithm is 0 % (that is, no bias high 

and no bias low), regardless of the uncompensated 

signal’s bias.
(1) Connect a CLD downstream of any dryer or chiller that is downstream of an NO2-to-NO 

converter that meets the verification in §1065.378. 

(2) Connect a CLD downstream of any dryer or thermal chiller that meets the verification in 

§1065.376. 

(e) Response time. You may use a heated CLD to improve CLD response time. 

§1065.272 Nondispersive ultraviolet analyzer. 

(a) Application. You may use a nondispersive ultraviolet (NDUV) analyzer to measure NOx

concentration in raw or diluted exhaust for batch or continuous sampling. We generally accept 

an NDUV for NOx measurement, even though it measures only NO and NO2, since conventional 

engines and aftertreatment systems do not emit significant amounts of other NOx species. 

Measure other NOx species if required by the standard-setting part. Note that good engineering 

judgment may preclude you from using an NDUV analyzer if sampled exhaust from test engines 

contains oil (or other contaminants) in sufficiently high concentrations to interfere with proper 

operation. 

(b) Component requirements. We recommend that you use an NDUV analyzer that meets the 

specifications in Table 1 of §1065.205. Note that your NDUV-based system must meet the 

verifications in §1065.372 and it must also meet the linearity verification in §1065.307. 

(c) NO2-to-NO converter. If your NDUV analyzer measures only NO, place upstream of the 

NDUV analyzer an internal or external NO2-to-NO converter that meets the verification in 

§1065.378. Configure the converter with a bypass to facilitate this verification. 

(d) Humidity effects. You must maintain NDUV temperature to prevent aqueous condensation, 

unless you use one of the following configurations: 

(1) Connect an NDUV downstream of any dryer or chiller that is downstream of an NO2-to-NO 

converter that meets the verification in §1065.378. 

(2) Connect an NDUV downstream of any dryer or thermal chiller that meets the verification in 

§1065.376. 

§1065.275 N2O measurement devices. 

(a) General component requirements. We recommend that you use an analyzer that meets the 

specifications in Table 1 of §1065.205. Note that your system must meet the linearity verification 

in §1065.307. 

(b) Instrument types. You may use any of the following analyzers to measure N2O: 

(1) Nondispersive infrared (NDIR) analyzer. 

(2) Fourier transform infrared (FTIR) analyzer. Use appropriate analytical procedures for 

interpretation of infrared spectra. For example, EPA Test Method 320 is considered a valid 

method for spectral interpretation (see http://www.epa.gov/ttn/emc/methods/method320.html). 

(3) Laser infrared analyzer. Examples of laser infrared analyzers are pulsed-mode highresolution narrow band mid-infrared analyzers, and modulated continuous wave high-resolution 

narrow band mid-infrared analyzers. 

(4) Photoacoustic analyzer. Use an optical wheel configuration that gives analytical priority to 

measurement of the least stable components in the sample. Select a sample integration time of at 

least 5 seconds. Take into account sample chamber and sample line volumes when determining 

flush times for your instrument. 

Formatted: French (France)

Deleted: You may use a NDUV analyzer that has 

compensation algorithms that are functions of other 

gaseous measurements and the engine’s known or 

assumed fuel properties. The target value for any 

compensation algorithm is 0 % (that is, no bias high 

and no bias low), regardless of the uncompensated 

signal’s bias.

Deleted: You may use an NDIR analyzer that has 

compensation algorithms that are functions of other 

gaseous measurements and the engine’s known or 

assumed fuel properties. The target value for any 

compensation algorithm is 0 % (that is, no bias high 

and no bias low), regardless of the uncompensated 

signal’s bias.

Deleted: You may use an FTIR analyzer that has 

compensation algorithms that are functions of other 

gaseous measurements and the engine’s known or 

assumed fuel properties. The target value for any 

compensation algorithm is 0 % (that is, no bias high 

and no bias low), regardless of the uncompensated 

signal’s bias.

Deleted: You may use a laser infrared analyzer 

that has compensation algorithms that are functions 

of other gaseous measurements and the engine’s 

known or assumed fuel properties. The target value 

for any compensation algorithm is 0 % (that is, no 

bias high and no bias low), regardless of the 

uncompensated signal’s bias.

Deleted: You may use a photoacoustic analyzer 

that has compensation algorithms that are functions 

of other gaseous measurements. The target value for 

any compensation algorithm is 0 % (that is, no bias 

high and no bias low), regardless of the 

uncompensated signal’s bias.
(5) Gas chromatograph analyzer. You may use a gas chromatograph with an electron-capture 

detector (GC-ECD) to measure N2O concentrations of diluted exhaust for batch sampling. 

(i)You may use a packed or porous layer open tubular (PLOT) column phase of suitable polarity 

and length to achieve adequate resolution of the N2O peak for analysis. Examples of acceptable 

columns are a PLOT column consisting of bonded polystyrene-divinylbenzene or a Porapack Q 

packed column. Take the column temperature profile and carrier gas selection into consideration 

when setting up your method to achieve adequate N2O peak resolution. 

(ii) Use good engineering judgment to zero your instrument and correct for drift. You do not 

need to follow the specific procedures in §§1065.530 and 1065.550(b) that would otherwise 

apply. For example, you may perform a span gas measurement before and after sample analysis 

without zeroing and use the average area counts of the pre-span and post-span measurements to 

generate a response factor (area counts/span gas concentration), which you then multiply by the 

area counts from your sample to generate the sample concentration. 

(c) Interference verification. Perform interference verification for NDIR, FTIR, laser infrared 

analyzers, and photoacoustic analyzers using the procedures of §1065.375. Interference 

verification is not required for GC-ECD. Certain interference gases can positively interfere with 

NDIR, FTIR, and photoacoustic analyzers by causing a response similar to N2O. When running 

the interference verification for these analyzers, use interference gases as follows: 

(1) The interference gases for NDIR analyzers are CO, CO2, H2O, CH4, and SO2. Note that 

interference species, with the exception of H2O, are dependent on the N2O infrared absorption 

band chosen by the instrument manufacturer. For each analyzer determine the N2O infrared 

absorption band. For each N2O infrared absorption band, use good engineering judgment to 

determine which interference gases to use in the verification. 

(2) Use good engineering judgment to determine interference gases for FTIR, and laser infrared 

analyzers. Note that interference species, with the exception of H2O, are dependent on the N2O 

infrared absorption band chosen by the instrument manufacturer. For each analyzer determine 

the N2O infrared absorption band. For each N2O infrared absorption band, use good engineering 

judgment to determine interference gases to use in the verification. 

(3) The interference gases for photoacoustic analyzers are CO, CO2, and H2O. 

O2 MEASUREMENTS 

§1065.280 Paramagnetic and magnetopneumatic O2 detection analyzers. 

(a) Application. You may use a paramagnetic detection (PMD) or magnetopneumatic detection 

(MPD) analyzer to measure O2 concentration in raw or diluted exhaust for batch or continuous 

sampling. You may use O2 measurements with intake air or fuel flow measurements to calculate 

exhaust flow rate according to §1065.650. 

(b) Component requirements. We recommend that you use a PMD or MPD analyzer that meets 

the specifications in Table 1 of §1065.205. Note that it must meet the linearity verification in 

§1065.307. 

AIR-TO-FUEL RATIO MEASUREMENTS 

§1065.284 Zirconia (ZrO2) analyzer. 

Deleted: You may use a PMD or MPD that has 

compensation algorithms that are functions of other 

gaseous measurements and the engine’s known or 

assumed fuel properties. The target value for any 

compensation algorithm is 0 % (that is, no bias high 

and no bias low), regardless of the uncompensated 

signal’s bias.
(a) Application. You may use a zirconia (ZrO2) analyzer to measure air-to-fuel ratio in raw 

exhaust for continuous sampling. You may use O2 measurements with intake air or fuel flow 

measurements to calculate exhaust flow rate according to §1065.650. 

(b) Component requirements. We recommend that you use a ZrO2 analyzer that meets the 

specifications in Table 1 of §1065.205. Note that your ZrO2-based system must meet the 

linearity verification in §1065.307. 

PM MEASUREMENTS 

§1065.290 PM gravimetric balance. 

(a) Application. Use a balance to weigh net PM on a sample medium for laboratory testing. 

(b) Component requirements. We recommend that you use a balance that meets the 

specifications in Table 1 of §1065.205. Note that your balance-based system must meet the 

linearity verification in §1065.307. If the balance uses internal calibration weights for routine 

spanning and the weights do not meet the specifications in §1065.790, the weights must be 

verified independently with external calibration weights meeting the requirements of §1065.790. 

While you may also use an inertial balance to measure PM, as described in §1065.295, use a 

reference procedure based on a gravimetric balance for comparison with any proposed alternate 

measurement procedure under §1065.10.

(c) Pan design. We recommend that you use a balance pan designed to minimize corner loading 

of the balance, as follows: 

(1) Use a pan that centers the PM sample media (such as a filter) on the weighing pan. For 

example, use a pan in the shape of a cross that has upswept tips that center the PM sample media 

on the pan. 

(2) Use a pan that positions the PM sample as low as possible. 

(d) Balance configuration. Configure the balance for optimum settling time and stability at your 

location. 

§1065.295 PM inertial balance for field-testing analysis. 

(a) Application. You may use an inertial balance to quantify net PM on a sample medium for 

field testing. 

(b) Component requirements. We recommend that you use a balance that meets the 

specifications in Table 1 of §1065.205. Note that your balance-based system must meet the 

linearity verification in §1065.307. If the balance uses an internal calibration process for routine 

spanning and linearity verifications, the process must be NIST-traceable. 

(c) Loss correction. You may use PM loss corrections to account for PM loss in the inertial 

balance, including the sample handling system. 

(d) Deposition. You may use electrostatic deposition to collect PM, as long as its collection 

efficiency is at least 95%.

Deleted: You may use a Zirconia analyzer that 

has compensation algorithms that are functions of 

other gaseous measurements and the engine’s known 

or assumed fuel properties. The target value for any 

compensation algorithm is 0 % (that is, no bias high 

and no bias low), regardless of the uncompensated 

signal’s bias.

Deleted: You may use an inertial PM balance that 

has compensation algorithms that are functions of 

other gaseous measurements and the engine’s known 

or assumed fuel properties. The target value for any 

compensation algorithm is 0 % (that is, no bias high 

and no bias low), regardless of the uncompensated 

signal’s bias.
Subpart D—Calibrations and Verifications

§1065.301 Overview and general provisions. 

(a) This subpart describes required and recommended calibrations and verifications of 

measurement systems. See subpart C of this part for specifications that apply to individual 

instruments. 

(b) You must generally use complete measurement systems when performing calibrations or 

verifications in this subpart. For example, this would generally involve evaluating instruments 

based on values recorded with the complete system you use for recording test data, including 

analog-to-digital converters. For some calibrations and verifications, we may specify that you 

disconnect part of the measurement system to introduce a simulated signal. 

(c) If we do not specify a calibration or verification for a portion of a measurement system, 

calibrate that portion of your system and verify its performance at a frequency consistent with 

any recommendations from the measurement-system manufacturer, consistent with good 

engineering judgment. 

(d) Use NIST-traceable standards to the tolerances we specify for calibrations and verifications. 

Where we specify the need to use NIST-traceable standards, you may alternatively ask for our 

approval to use international standards that are not NIST-traceable. 

§1065.303 Summary of required calibration and verifications. 

The following table summarizes the required and recommended calibrations and verifications 

described in this subpart and indicates when these have to be performed: 
Table 1 of §1065.303–Summary of required calibration and verifications. 

Type of calibration or verification Minimum frequency1

§1065.305: Accuracy, repeatability and noise 

Accuracy: Not required, but recommended for initial installation. 

Repeatability: Not required, but recommended for initial installation. 

Noise: Not required, but recommended for initial installation. 

§1065.307: Linearity verification 

Speed: Upon initial installation, within 370 days before testing and 

after major maintenance. 

Torque: Upon initial installation, within 370 days before testing and 

after major maintenance. 

Electrical power, current, and voltage: Upon initial installation, 

within 370 days before testing and after major maintenance.2

Fuel flow rate: Upon initial installation, within 370 days before 

testing, and after major maintenance. 

Intake-air, dilution air, diluted exhaust, and batch sampler flow rates: 

Upon initial installation, within 370 days before testing and after 

major maintenance, unless flow is verified by propane check or by 

carbon or oxygen balance. 

Raw exhaust flow rate: Upon initial installation, within 185 days 

before testing and after major maintenance, unless flow is verified by 

propane check or by carbon or oxygen balance. 

Gas dividers: Upon initial installation, within 370 days before testing, 

and after major maintenance. 

Gas analyzers (unless otherwise noted): Upon initial installation, 

within 35 days before testing and after major maintenance. 

FTIR and photoacoustic analyzers: Upon initial installation, within 

370 days before testing and after major maintenance. 

GC-ECD: Upon initial installation and after major maintenance. 

PM balance: Upon initial installation, within 370 days before testing 

and after major maintenance. 

Pressure, temperature, and dewpoint: Upon initial installation, within 

370 days before testing and after major maintenance. 

§1065.308: Continuous gas analyzer system response 

and updating-recording verification—for gas analyzers 

not continuously compensated for other gas species 

Upon initial installation or after system modification that would affect 

response. 

§1065.309: Continuous gas analyzer system-response 

and updating-recording verification—for gas analyzers 

continuously compensated for other gas species 

Upon initial installation or after system modification that would affect 

response. 

§1065.310: Torque Upon initial installation and after major maintenance. 

§1065.315: Pressure, temperature, dewpoint Upon initial installation and after major maintenance. 

§1065.320: Fuel flow Upon initial installation and after major maintenance. 

§1065.325: Intake flow Upon initial installation and after major maintenance. 

§1065.330: Exhaust flow Upon initial installation and after major maintenance. 

§1065.340: Diluted exhaust flow (CVS) Upon initial installation and after major maintenance. 

§1065.341: CVS and batch sampler verification3 Upon initial installation, within 35 days before testing, and after 

major maintenance. 

§1065.342 Sample dryer verification 

For thermal chillers: upon installation and after major maintenance. 

For osmotic membranes; upon installation, within 35 days of testing, 

and after major maintenance. 

§1065.345: Vacuum leak 

For laboratory testing: upon initial installation of the sampling 

system, within 8 hours before the start of the first test interval of each 

duty-cycle sequence, and after maintenance such as pre-filter 

changes. 

For field testing: after each installation of the sampling system on the 

vehicle, prior to the start of the field test, and after maintenance such 

as pre-filter changes. 

§1065.350: CO2 NDIR H2O interference Upon initial installation and after major maintenance. 

§1065.355: CO NDIR CO2 and H2O interference Upon initial installation and after major maintenance. 

Deleted: frequencya

Deleted: verificationb
§1065.360: FID calibration 

THC FID optimization, and THC FID verification 

Calibrate all FID analyzers: upon initial installation and after major 

maintenance. 

Optimize and determine CH4 response for THC FID analyzers: 

upon initial installation and after major maintenance. 

Verify CH4 response for THC FID analyzers: upon initial installation, 

within 185 days before testing, and after major maintenance. 

§1065.362: Raw exhaust FID O2 interference 

For all FID analyzers: upon initial installation, and after major 

maintenance. 

For THC FID analyzers: upon initial installation, after major 

maintenance, and after FID optimization according to §1065.360. 

§1065.365: Nonmethane cutter penetration Upon initial installation, within 185 days before testing, and after 

major maintenance. 

§1065.369: H2O, CO, and CO2 interference verification 

for ethanol photoacoustic analyzers Upon initial installation and after major maintenance.

§1065.370: CLD CO2 and H2O quench Upon initial installation and after major maintenance. 

§1065.372: NDUV HC and H2O interference Upon initial installation and after major maintenance. 

§1065.375: N2O analyzer interference Upon initial installation and after major maintenance. 

§1065.376: Chiller NO2 penetration Upon initial installation and after major maintenance. 

§1065.378: NO2-to-NO converter conversion Upon initial installation, within 35 days before testing, and after 

major maintenance. 

§1065.390: PM balance and weighing 

Independent verification: upon initial installation, within 370 days 

before testing, and after major maintenance. 

Zero, span, and reference sample verifications: within 12 hours of 

weighing, and after major maintenance. 

§1065.395: Inertial PM balance and weighing 

Independent verification: upon initial installation, within 370 days 

before testing, and after major maintenance. 

Other verifications: upon initial installation and after major 

maintenance. 1

Perform calibrations and verifications more frequently than we specify, according to measurement system manufacturer 

instructions and good engineering judgment. 

2

Perform either electrical power linearity verification or current and voltage.

3

The CVS verification described in §1065.341 is not required for systems that agree within ±2 % based on a chemical balance of 

carbon or oxygen of the intake air, fuel, and diluted exhaust. 

§1065.305 Verifications for accuracy, repeatability, and noise. 

(a) This section describes how to determine the accuracy, repeatability, and noise of an 

instrument. Table 1 of §1065.205 specifies recommended values for individual instruments. 

(b) We do not require you to verify instrument accuracy, repeatability, or noise. However, it 

may be useful to consider these verifications to define a specification for a new instrument, to 

verify the performance of a new instrument upon delivery, or to troubleshoot an existing 

instrument. 

(c) In this section we use the letter “y” to denote a generic measured quantity, the superscript 

over-bar to denote an arithmetic mean (such as y ), and the subscript “ref” to denote the reference 

quantity being measured. 

(d) Conduct these verifications as follows: 

(1) Prepare an instrument so it operates at its specified temperatures, pressures, and flows. 

Perform any instrument linearization or calibration procedures prescribed by the instrument 

manufacturer. 

(2) Zero the instrument as you would before an emission test by introducing a zero signal. 

Depending on the instrument, this may be a zero-concentration gas, a reference signal, a set of 

reference thermodynamic conditions, or some combination of these. For gas analyzers, use a 

zero gas that meets the specifications of §1065.750. 

Deleted: aPerform 

Deleted: b
(3) Span the instrument as you would before an emission test by introducing a span signal. 

Depending on the instrument, this may be a span-concentration gas, a reference signal, a set of 

reference thermodynamic conditions, or some combination of these. For gas analyzers, use a 

span gas that meets the specifications of §1065.750. 

(4) Use the instrument to quantify a NIST-traceable reference quantity, yref. For gas analyzers 

the reference gas must meet the specifications of §1065.750. Select a reference quantity near the 

mean value expected during testing. For all gas analyzers, use a quantity near the flow-weighted 

mean concentration expected at the standard or expected during testing, whichever is greater. 

For noise verification, use the same zero gas from paragraph (d)(2) of this section as the 

reference quantity. In all cases, allow time for the instrument to stabilize while it measures the 

reference quantity. Stabilization time may include time to purge an instrument and time to 

account for its response. 

(5) Sample and record values for 30 seconds (you may select a longer sampling period if the 

recording update frequency is less than 0.5 Hz), record the arithmetic mean, i y and record the 

standard deviation,  i of the recorded values. Refer to §1065.602 for an example of calculating 

arithmetic mean and standard deviation. 

(6) Also, if the reference quantity is not absolutely constant, which might be the case with a 

reference flow, sample and record values of yrefi for 30 seconds and record the arithmetic mean of 

the values, ref y . Refer to §1065.602 for an example of calculating arithmetic mean. 

(7) Subtract the reference value, yref (or refi y ), from the arithmetic mean, i y . Record this value as 

the error, i. 

(8) Repeat the steps specified in paragraphs (d)(2) through (7) of this section until you have ten 

arithmetic means ( 1y , 2 y , i y ,... 10 y ), ten standard deviations, (1, 2, i,...10), and ten errors (1, 

2 , i ,...10). 

(9) Use the following values to quantify your measurements: 

(i) Accuracy. Instrument accuracy is the absolute difference between the reference quantity, yref

(or ref y ), and the arithmetic mean of the ten i y values, y . Refer to the example of an accuracy 

calculation in §1065.602. We recommend that instrument accuracy be within the specifications 

in Table 1 of §1065.205. 

(ii) Repeatability. Repeatability is two times the standard deviation of the ten errors (that is, 

repeatability = 2). Refer to the example of a standard-deviation calculation in §1065.602. We 

recommend that instrument repeatability be within the specifications in Table 1 of §1065.205. 

(iii) Noise. Noise is two times the root-mean-square of the ten standard deviations (that is, noise 

= 2·rms) when the reference signal is a zero-quantity signal. Refer to the example of a rootmean-square calculation in §1065.602. We recommend that instrument noise be within the 

specifications in Table 1 of §1065.205. 

(10) You may use a measurement instrument that does not meet the accuracy, repeatability, or 

noise specifications in Table 1 of §1065.205, as long as you meet the following criteria: 

(i) Your measurement systems meet all the other required calibration, verification, and validation 

specifications that apply as specified in the regulations. Deleted: in subparts D, F, and J of this part
(ii) The measurement deficiency does not adversely affect your ability to demonstrate 

compliance with the applicable standards. 

§1065.307 Linearity verification. 

(a) Scope and frequency. Perform linearity verification on each measurement system listed in 

Table 1 of this section at least as frequently as indicated in Table 1 of §1065.303, consistent with 

measurement system manufacturer’s recommendations and good engineering judgment. The 

intent of linearity verification is to determine that a measurement system responds accurately and 

proportionally over the measurement range of interest. Linearity verification generally consists 

of introducing a series of at least 10 reference values to a measurement system. The 

measurement system quantifies each reference value. The measured values are then collectively 

compared to the reference values by using a least-squares linear regression and the linearity 

criteria specified in Table 1 of this section. 

(b) Performance requirements. If a measurement system does not meet the applicable linearity 

criteria referenced in Table 1 of this section, correct the deficiency by re-calibrating, servicing, 

or replacing components as needed. Repeat the linearity verification after correcting the 

deficiency to ensure that the measurement system meets the linearity criteria. Before you may 

use a measurement system that does not meet linearity criteria, you must demonstrate to us that 

the deficiency does not adversely affect your ability to demonstrate compliance with the 

applicable standards. 

(c) Procedure. Use the following linearity verification protocol, or use good engineering 

judgment to develop a different protocol that satisfies the intent of this section, as described in 

paragraph (a) of this section: 

(1) In this paragraph (c), the letter “y” denotes a generic measured quantity, the superscript overbar denotes an arithmetic mean (such as y ), and the subscript “ref” denotes the known or 

reference quantity being measured. 

(2) Use good engineering judgment to operate a measurement system at normal operating 

conditions. This may include any specified adjustment or periodic calibration of the 

measurement system. 

(3) If applicable, zero the instrument as you would before an emission test by introducing a zero 

signal. Depending on the instrument, this may be a zero-concentration gas, a reference signal, a 

set of reference thermodynamic conditions, or some combination of these. For gas analyzers, 

use a zero gas that meets the specifications of §1065.750 and introduce it directly at the analyzer 

port. 

(4) If applicable, span the instrument as you would before an emission test by introducing a span 

signal. Depending on the instrument, this may be a span-concentration gas, a reference signal, a 

set of reference thermodynamic conditions, or some combination of these. For gas analyzers, 

use a span gas that meets the specifications of §1065.750 and introduce it directly at the analyzer 

port. 

(5) If applicable, after spanning the instrument, check zero with the same signal you used in 

paragraph (c)(3) of this section. Based on the zero reading, use good engineering judgment to 

determine whether or not to rezero and or re-span the instrument before continuing. 

(6) For all measured quantities, use the instrument manufacturer’s recommendations and good 

engineering judgment to select reference values, yrefi, that cover a range of values that you expect 

Deleted: a 

Deleted: Note that this linearity verification may 

replace requirements we previously referred to as 

“calibrations”. 

Deleted: a 

Deleted: A l

Deleted: 

Deleted: we use 

Deleted: to 

Deleted: to 

Deleted: to 

Deleted: Operate 

Deleted: its specified

Deleted: temperatures, pressures, and flows

Deleted: Z

Deleted: S

Deleted: A

Deleted: proceeding to the next step
would prevent extrapolation beyond these values during emission testing. We recommend 

selecting a zero reference signal as one of the reference values for the linearity verification. For 

pressure, temperature, dewpoint, power, current, voltage, photoacoustic analyzers, and GC-ECD 

linearity verifications, we recommend at least three reference values. For all other linearity 

verifications select at least ten reference values. 

(7) Use the instrument manufacturer’s recommendations and good engineering judgment to 

select the order in which you will introduce the series of reference values. For example, you 

may select the reference values randomly to avoid correlation with previous measurements and 

to avoid hysteresis; you may select reference values in ascending or descending order to avoid 

long settling times of reference signals; or you may select values to ascend and then descend to 

incorporate the effects of any instrument hysteresis into the linearity verification. 

(8) Generate reference quantities as described in paragraph (d) of this section. For gas analyzers, 

use gas concentrations known to be within the specifications of §1065.750 and introduce them 

directly at the analyzer port. 

(9) Introduce a reference signal to the measurement instrument. 

(10) Allow time for the instrument to stabilize while it measures the value at the reference 

condition. Stabilization time may include time to purge an instrument and time to account for its 

response. 

(11) At a recording frequency of at least f Hz, specified in Table 1 of §1065.205, measure the 

value at the reference condition for 30 seconds (you may select a longer sampling period if the 

recording update frequency is less than 0.5 Hz) and record the arithmetic mean of the recorded 

values, i y . Refer to §1065.602 for an example of calculating an arithmetic mean. 

(12) Repeat the steps in paragraphs (c)(9) though (11) of this section until measurements are 

complete at each of the reference conditions. 

(13) Use the arithmetic means, i y , and reference values, yrefi , to calculate least-squares linear 

regression parameters and statistical values to compare to the minimum performance criteria 

specified in Table 1 of this section. Use the calculations described in §1065.602. Using good 

engineering judgment, you may weight the results of individual data pairs (i.e.(yrefi, i y )), in the 

linear regression calculations. 

(d) Reference signals. This paragraph (d) describes recommended methods for generating 

reference values for the linearity-verification protocol in paragraph (c) of this section. Use 

reference values that simulate actual values, or introduce an actual value and measure it with a 

reference-measurement system. In the latter case, the reference value is the value reported by the 

reference-measurement system. Reference values and reference-measurement systems must be 

NIST-traceable. We recommend using calibration reference quantities that are NIST-traceable 

within 0.5 % uncertainty, if not specified elsewhere in this part 1065. Use the following 

recommended methods to generate reference values or use good engineering judgment to select a 

different reference: 

(1) Speed. Run the engine or dynamometer at a series of steady-state speeds and use a strobe, 

photo tachometer, or laser tachometer to record reference speeds. 

(2) Torque. Use a series of calibration weights and a calibration lever arm to simulate engine 

torque. You may instead use the engine or dynamometer itself to generate a nominal torque that 

is measured by a reference load cell or proving ring in series with the torque-measurement 

Deleted: of 

Deleted: ,

Deleted: ,

Deleted: as another example 

Deleted: which might 

Deleted: reference 

Deleted: reference 

Deleted: all 

Deleted: quantities are measured

Deleted: otherwise in other sections of 

Deleted: a

Deleted: a
system. In this case, use the reference load cell measurement as the reference value. Refer to 

§1065.310 for a torque-calibration procedure similar to the linearity verification in this section. 

(3) Electrical power, current, and voltage. Perform linearity verifications using a reference meter 

and controlled sources of current and voltage. We recommend using a complete calibration 

system that is suitable for the electrical power distribution industry.

(4) Fuel rate. Operate the engine at a series of constant fuel-flow rates or re-circulate fuel back 

to a tank through the fuel flow meter at different flow rates. Use a gravimetric reference 

measurement (such as a scale, balance, or mass comparator) at the inlet to the fuel-measurement 

system. Use a stopwatch or timer to measure the time intervals over which reference masses of 

fuel are introduced to the fuel measurement system. The reference fuel mass divided by the time 

interval is the reference fuel flow rate. 

(5) Flow rates—inlet air, dilution air, diluted exhaust, raw exhaust, or sample flow. Use a 

reference flow meter with a blower or pump to simulate flow rates. Use a restrictor, diverter 

valve, a variable-speed blower or a variable-speed pump to control the range of flow rates. Use 

the reference meter’s response as the reference values. 

(i) Reference flow meters. Because the flow range requirements for these various flows are 

large, we allow a variety of reference meters. For example, for diluted exhaust flow for a fullflow dilution system, we recommend a reference subsonic venturi flow meter with a restrictor 

valve and a blower to simulate flow rates. For inlet air, dilution air, diluted exhaust for partialflow dilution, raw exhaust, or sample flow, we allow reference meters such as critical flow 

orifices, critical flow venturis, laminar flow elements, master mass flow standards, or Roots 

meters. Make sure the reference meter is calibrated by the flow-meter manufacturer and its 

calibration is NIST-traceable. If you use the difference of two flow measurements to determine a 

net flow rate, you may use one of the measurements as a reference for the other. 

(ii) Reference flow values. Because the reference flow is not absolutely constant, sample and 

record values of refi n for 30 seconds and use the arithmetic mean of the values, ref n , as the 

reference value. Refer to §1065.602 for an example of calculating arithmetic mean. 

(6) Gas division. Use one of the two reference signals: 

(i) At the outlet of the gas-division system, connect a gas analyzer that meets the linearity 

verification described in this section and has not been linearized with the gas divider being 

verified. For example, verify the linearity of an analyzer using a series of reference analytical 

gases directly from compressed gas cylinders that meet the specifications of §1065.750. We 

recommend using a FID analyzer or a PMD or MPD O2 analyzer because of their inherent 

linearity. Operate this analyzer consistent with how you would operate it during an emission 

test. Connect a span gas to the gas-divider inlet. Use the gas-division system to divide the span 

gas with purified air or nitrogen. Select gas divisions that you typically use. Use a selected gas 

division as the measured value. Use the analyzer response divided by the span gas concentration 

as the reference gas-division value. Because the instrument response is not absolutely constant, 

sample and record values of xrefi for 30 seconds and use the arithmetic mean of the values, ref x , 

as the reference value. Refer to §1065.602 for an example of calculating arithmetic mean. 

(ii) Using good engineering judgment and the gas divider manufacturer’s recommendations, use 

one or more reference flow meters to measure the flow rates of the gas divider and verify the 

gas-division value. 

Deleted: Use a controlled source of current and a 

watt-hour standard reference meter. Complete 

calibration systems that contain a current source and 

a reference watt-hour meter are commonly used in 

the electrical power distribution industry and are 

therefore commercially available.
(7) Continuous constituent concentration. For reference values, use a series of gas cylinders of 

known gas concentration or use a gas-division system that is known to be linear with a span gas. 

Gas cylinders, gas-division systems, and span gases that you use for reference values must meet 

the specifications of §1065.750. 

(8) Temperature. You may perform the linearity verification for temperature measurement 

systems with thermocouples, RTDs, and thermistors by removing the sensor from the system and 

using a simulator in its place. Use a NIST-traceable simulator that is independently calibrated 

and, as appropriate, cold-junction-compensated. The simulator uncertainty scaled to absolute 

temperature must be less than 0.5 % of Tmax. If you use this option, you must use sensors that the 

supplier states are accurate to better than 0.5 % of Tmax compared with their standard calibration 

curve. 

(9) Mass. For linearity verification for gravimetric PM balances, use external calibration weights 

that that meet the requirements in §1065.790. 

(e) Measurement systems that require linearity verification. Table 1 of this section indicates 

measurement systems that require linearity verification, subject to the following provisions: 

(1) Perform linearity verification more frequently based on the instrument manufacturer’s 

recommendation or good engineering judgment. 

(2) The expression “xmin” refers to the reference value used during linearity verification that is 

closest to zero. This is the value used to calculate the first tolerance in Table 1 of this section 

using the intercept, a0. Note that this value may be zero, positive, or negative depending on the 

reference values. For example, if the reference values chosen to validate a pressure transducer 

vary from -10 to -1 kPa, xmin is -1 kPa. If the reference values used to validate a temperature 

device vary from 290 to 390 K, xmin is 290 K. 

(3) The expression “max” generally refers to the absolute value of the reference value used 

during linearity verification that is furthest from zero. This is the value used to scale the first and 

third tolerances in Table 1 of this section using a0 and SEE. For example, if the reference values 

chosen to validate a pressure transducer vary from -10 to -1 kPa, then pmax is +10 kPa. If the 

reference values used to validate a temperature device vary from 290 to 390 K, then Tmax is 390 

K. For gas dividers where “max” is expressed as, xmax/xspan; xmax is the maximum gas 

concentration used during the verification, xspan is the undivided, undiluted, span gas 

concentration, and the resulting ratio is the maximum divider point reference value used during 

the verification (typically 1). The following are special cases where “max” refers to a different 

value: 

(i) For linearity verification with a PM balance, mmax refers to the typical mass of a PM filter. 

(ii) For linearity verification of torque on the engine’s primary output shaft, Tmax refers to the 

manufacturer’s specified engine torque peak value of the lowest torque engine to be tested. 

(4) The specified ranges are inclusive. For example, a specified range of 0.98-1.02 for a1 means 

0.98a11.02. 

(5) Linearity verification is optional for systems that pass the flow-rate verification for diluted 

exhaust as described in §1065.341 (the propane check) or for systems that agree within ±2 % 

based on a chemical balance of carbon or oxygen of the intake air, fuel, and exhaust. 

(6) You must meet the a1 criteria for these quantities only if the absolute value of the quantity is 

required, as opposed to a signal that is only linearly proportional to the actual value. 

(7) Linearity verification is required for the following temperature measurements: 

Deleted: 

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Deleted: a 

Deleted: the 

Deleted: the 

Deleted: These l

Deleted: s are 

Deleted: checks are 
(i) The following temperature measurements always require linearity verification: 

(A) Air intake. 

(B) Aftertreatment bed(s), for engines tested with aftertreatment devices subject to cold-start 

testing. 

(C) Dilution air for PM sampling, including CVS, double-dilution, and partial-flow systems. 

(D) PM sample. 

(E) Chiller sample, for gaseous sampling systems that use thermal chillers to dry samples and use 

chiller temperature to calculate the dewpoint at the outlet of the chiller. For your testing, if you 

choose to use a high alarm temperature setpoint for the chiller temperature as a constant value in 

determining the amount of water removed from the emission sample, you may use good 

engineering judgment to verify the accuracy of the high alarm temperature setpoint instead of 

linearity verification on the chiller temperature. To verify that the alarm trip point value is no 

less than 2.0 °C below the reference value at the trip point, we recommend that you input a 

reference simulated temperature signal below the alarm trip point and increase this signal until 

the high alarm trips.

(ii) Linearity verification is required for the following temperature measurements if these 

temperature measurements are specified by the engine manufacturer: 

(A) Fuel inlet. 

(B) Air outlet to the test cell’s charge air cooler air outlet, for engines tested with a laboratory 

heat exchanger that simulates an installed charge air cooler. 

(C) Coolant inlet to the test cell’s charge air cooler, for engines tested with a laboratory heat 

exchanger that simulates an installed charge air cooler. 

(D) Oil in the sump/pan. 

(E) Coolant before the thermostat, for liquid-cooled engines. 

(8) Linearity verification is required for the following pressure measurements: 

(i) The following pressure measurements always require linearity verification: 

(A) Air intake restriction. 

(B) Exhaust back pressure. 

(C) Barometer. 

(D) CVS inlet gage pressure. 

(E) Sample dryer, for gaseous sampling systems that use either osmotic-membrane or thermal 

chillers to dry samples. For your testing, if you choose to use a low alarm pressure setpoint for 

the sample dryer pressure as a constant value in determining the amount of water removed from 

the emission sample, you may use good engineering judgment to verify the accuracy of the low 

alarm pressure setpoint instead of linearity verification on the sample dryer pressure. To verify 

that the trip point value is no more than 4.0 kPa above the reference value at the trip point, we 

recommend that you input a reference pressure signal above the alarm trip point and decrease 

this signal until the low alarm trips. 

(ii) Linearity verification is required for the following pressure measurements if these pressure 

measurements are specified by the engine manufacturer: 

(A) The test cell’s charge air cooler and interconnecting pipe pressure drop, for turbo-charged 

engines tested with a laboratory heat exchanger that simulates an installed charge air cooler. 

(B) Fuel outlet.

Deleted: checks

Deleted: , if applicable

Deleted: calculations in §1065.645, 

Deleted: in lieu 

Deleted: the 

Deleted: W

Deleted: ,

Deleted: , and verify that the alarm trip point value 

is no less than 2.0 °C below the reference value at 

the trip point.

Deleted: checks are 

Deleted: checks are 

Deleted: checks

Deleted: calculations in §1065.645, 

Deleted: in lieu 

Deleted: the 

Deleted: We 

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Deleted: , and verify that the trip point value is no 

more than 4.0 kPa above the reference value at the 

trip point

Deleted: checks are 
Table 1 of §1065.307–Measurement systems that require linearity verification. 

Measurement system Quantity Linearity criteria 

| xmin(a1-1)+a0 | a1 SEE r

2

Speed fn ≤ 0.05 % · nmax f 0.98-1.02 ≤ 2 % · nmax f ≥ 0.990 

Torque T ≤ 1 % · Tmax 0.98-1.02 ≤ 2 % · Tmax ≥ 0.990 

Electrical power P ≤ 1 % · Pmax 0.98-1.02 ≤ 2 % · Pmax ≥ 0.990 

Current I ≤ 1 % · max I 0.98-1.02 ≤ 2 % · max I ≥ 0.990

Voltage U ≤ 1 % · Umax 0.98-1.02 ≤ 2 % · Umax ≥ 0.990

Fuel flow rate m ≤ 1 % · mmax  0.98-1.02 ≤ 2 % · mmax  ≥ 0.990 

Intake-air 

flow rate1 n ≤ 1 % · max n 0.98-1.02 ≤ 2 % · max n ≥ 0.990 

Dilution air 

flow rate1 n ≤ 1 % · max n 0.98-1.02 ≤ 2 % · max n ≥ 0.990 

Diluted exhaust 

flow rate1 n ≤ 1 % · max n 0.98-1.02 ≤ 2 % · max n ≥ 0.990 

Raw exhaust 

flow rate1 n ≤ 1 % · max n 0.98-1.02 ≤ 2 % · max n ≥ 0.990 

Batch sampler 

flow rates1 n ≤ 1 % · max n 0.98-1.02 ≤ 2 % · max n ≥ 0.990 

Gas dividers x/xspan ≤ 0.5 % · xmax/xspan 0.98-1.02 ≤ 2 % · xmax/xspan ≥ 0.990 

Gas analyzers for 

laboratory testing x ≤ 0.5 % · max x 0.99-1.01 ≤ 1 % · max x ≥ 0.998 

Gas analyzers for 

field testing x ≤ 1 % · max x 0.99-1.01 ≤ 1 % · max x ≥ 0.998 

PM balance m ≤ 1 % · mmax 0.99-1.01 ≤ 1 % · mmax ≥ 0.998 

Pressures p ≤ 1 % · max p 0.99-1.01 ≤ 1 % · max p ≥ 0.998 

Dewpoint for intake 

air, PM-stabilization 

and balance 

environments 

Tdew ≤ 0.5 % · Tdewmax 0.99-1.01 ≤ 0.5 % · Tdewmax ≥ 0.998 

Other dewpoint 

measurements Tdew ≤ 1 % · Tdewmax 0.99-1.01 ≤ 1 % · Tdewmax ≥ 0.998 

Analog-to-digital 

conversion of 

temperature signals 

T ≤ 1 % · Tmax 0.99-1.01 ≤ 1 % · Tmax ≥ 0.998 

1

For flow meters that determine volumetric flow rate, Vstd  , you may substitute Vstd  for n as the quantity and substitute 

Vstdmax  for max n .

§1065.308 Continuous gas analyzer system-response and updating-recording verification—

for gas analyzers not continuously compensated for other gas species. 

(a) Scope and frequency. This section describes a verification procedure for system response 

and updating-recording frequency for continuous gas analyzers that output a gas species mole 

fraction (i.e., concentration) using a single gas detector, i.e., gas analyzers not continuously 

compensated for other gas species measured with multiple gas detectors. See §1065.309 for 

verification procedures that apply to continuous gas analyzers that are continuously compensated 

for other gas species measured with multiple gas detectors. Perform this verification to 

Deleted: s
determine the system response of the continuous gas analyzer and its sampling system. This 

verification is required for continuous gas analyzers used for transient or ramped-modal testing. 

You need not perform this verification for batch gas analyzer systems or for continuous gas 

analyzer systems that are used only for discrete-mode testing. Perform this verification after 

initial installation (i.e., test cell commissioning) and after any modifications to the system that 

would change system response. For example, perform this verification if you add a significant 

volume to the transfer lines by increasing their length or adding a filter; or if you reduce the 

frequency at which the gas analyzer updates its output or the frequency at which you sample and 

record gas-analyzer concentrations. 

(b) Measurement principles. This test verifies that the updating and recording frequencies match 

the overall system response to a rapid change in the value of concentrations at the sample probe. 

Gas analyzers and their sampling systems must be optimized such that their overall response to a 

rapid change in concentration is updated and recorded at an appropriate frequency to prevent loss 

of information. This test also verifies that the measurement system meets a minimum response 

time. You may use the results of this test to determine transformation time, t50, for the purposes 

of time alignment of continuous data in accordance with §1065.650(c)(2)(i). You may also use 

an alternate procedure to determine t50 in accordance with good engineering judgment. Note that 

any such procedure for determining t50 must account for both transport delay and analyzer 

response time. 

(c) System requirements. Demonstrate that each continuous analyzer has adequate update and 

recording frequencies and has a minimum rise time and a minimum fall time during a rapid 

change in gas concentration. You must meet one of the following criteria: 

(1) The product of the mean rise time, t10-90, and the frequency at which the system records an 

updated concentration must be at least 5, and the product of the mean fall time, t90-10, and the 

frequency at which the system records an updated concentration must be at least 5. If the 

recording frequency is different than the analyzer’s output update frequency, you must use the 

lower of these two frequencies for this verification, which is referred to as the updatingrecording frequency. This verification applies to the nominal updating and recording 

frequencies. This criterion makes no assumption regarding the frequency content of changes in 

emission concentrations during emission testing; therefore, it is valid for any testing. Also, the 

mean rise time must be at or below 10 seconds and the mean fall time must be at or below 10 

seconds. 

(2) The frequency at which the system records an updated concentration must be at least 5 Hz. 

This criterion assumes that the frequency content of significant changes in emission 

concentrations during emission testing do not exceed 1 Hz. Also, the mean rise time must be at 

or below 10 seconds and the mean fall time must be at or below 10 seconds. 

(3) You may use other criteria if we approve the criteria in advance. 

(4) You may meet the overall PEMS verification in §1065.920 instead of the verification in this 

section for field testing with PEMS. 

(d) Procedure. Use the following procedure to verify the response of each continuous gas 

analyzer: 

(1) Instrument setup. Follow the analyzer manufacturer’s start-up and operating instructions. 

Adjust the measurement system as needed to optimize performance. Run this verification with 

the analyzer operating in the same manner you will use for emission testing. If the analyzer 
shares its sampling system with other analyzers, and if gas flow to the other analyzers will affect 

the system response time, then start up and operate the other analyzers while running this 

verification test. You may run this verification test on multiple analyzers sharing the same 

sampling system at the same time. If you use any analog or real-time digital filters during 

emission testing, you must operate those filters in the same manner during this verification. 

(2) Equipment setup. We recommend using minimal lengths of gas transfer lines between all 

connections and fast-acting three-way valves (2 inlets, 1 outlet) to control the flow of zero and 

blended span gases to the sample system’s probe inlet or a tee near the outlet of the probe. If you 

inject the gas at a tee near the outlet of the probe, you may correct the transformation time, t50, 

for an estimate of the transport time from the probe inlet to the tee. Normally the gas flow rate is 

higher than the sample flow rate and the excess is overflowed out the inlet of the probe. If the 

gas flow rate is lower than the sample flow rate, the gas concentrations must be adjusted to 

account for the dilution from ambient air drawn into the probe. We recommend you use the 

final, stabilized analyzer reading as the final gas concentration. Select span gases for the species 

being measured. You may use binary or multi-gas span gases. You may use a gas blending or 

mixing device to blend span gases. A gas blending or mixing device is recommended when 

blending span gases diluted in N2 with span gases diluted in air. You may use a multi-gas span 

gas, such as NO-CO-CO2-C3H8-CH4, to verify multiple analyzers at the same time. If you use 

standard binary span gases, you must run separate response tests for each analyzer. In designing 

your experimental setup, avoid pressure pulsations due to stopping the flow through the gasblending device. The change in gas concentration must be at least 20 % of the analyzer's range.

(3) Data collection. (i) Start the flow of zero gas. 

(ii) Allow for stabilization, accounting for transport delays and the slowest analyzer’s full 

response. 

(iii) Start recording data. For this verification you must record data at a frequency greater than or 

equal to that of the updating-recording frequency used during emission testing. You may not use 

interpolation or filtering to alter the recorded values. 

(iv) Switch the flow to allow the blended span gases to flow to the analyzer. If you intend to use 

the data from this test to determine t50 for time alignment, record this time as t0. 

(v) Allow for transport delays and the slowest analyzer’s full response. 

(vi) Switch the flow to allow zero gas to flow to the analyzer. If you intend to use the data from 

this test to determine t50 for time alignment, record this time as t100. 

(vii) Allow for transport delays and the slowest analyzer’s full response. 

(viii) Repeat the steps in paragraphs (d)(3)(iv) through (vii) of this section to record seven full 

cycles, ending with zero gas flowing to the analyzers. 

(ix) Stop recording. 

(e) Performance evaluation. (1) If you choose to demonstrate compliance with paragraph (c)(1) 

of this section, use the data from paragraph (d)(3) of this section to calculate the mean rise time, 

t10-90, and mean fall time, t90-10, for each of the analyzers being verified. You may use 

interpolation between recorded values to determine rise and fall times. If the recording 

frequency used during emission testing is different from the analyzer’s output update frequency, 

you must use the lower of these two frequencies for this verification. Multiply these times (in 

seconds) by their respective updating-recording frequencies in Hertz (1/second). The resulting 

product must be at least 5 for both rise time and fall time. If either value is less than 5, increase 

Deleted: probe 

Deleted: probe 
the updating-recording frequency, or adjust the flows or design of the sampling system to 

increase the rise time and fall time as needed. You may also configure analog or digital filters 

before recording to increase rise and fall times. In no case may the mean rise time or mean fall 

time be greater than 10 seconds. 

(2) If a measurement system fails the criterion in paragraph (e)(1) of this section, ensure that 

signals from the system are updated and recorded at a frequency of at least 5 Hz. In no case may 

the mean rise time or mean fall time be greater than 10 seconds. 

(3) If a measurement system fails the criteria in paragraphs (e)(1) and (2) of this section, you 

may use the measurement system only if the deficiency does not adversely affect your ability to 

show compliance with the applicable standards. 

(f) Transformation time, t50, determination. If you choose to determine t50 for purposes of time 

alignment using data generated in paragraph (d)(3) of this section, calculate the mean t0-50 and 

the mean t100-50 from the recorded data. Average these two values to determine the final t50 for 

the purposes of time alignment in accordance with §1065.650(c)(2)(i).

(g) Optional procedure. Instead of using a three-way valve to switch between zero and span 

gases, you may use a fast-acting two-way valve to switch sampling between ambient air and span 

gas at the probe inlet. For this alternate procedure, the following provisions apply:

(1) If your probe is sampling from a continuously flowing gas stream (such as a CVS tunnel), 

you may adjust the span gas flow rate to be different than the sample flow rate.

(2) If your probe is sampling from a gas stream that is not continuously flowing (such as a raw 

exhaust stack), you must adjust the span gas flow rate to be less than the sample flow rate so 

ambient air is always drawn into the probe inlet. This avoids errors associated with overflowing 

span gas out of the probe inlet and drawing the span gas back in when sampling ambient air.

(3) When sampling ambient air with or without span gas, all the analyzer readings used to 

determine the final, stabilized gas concentration must be within ±0.5 % of the final gas 

concentration. If any analyzer reading is outside the specified range, you must resolve the 

problem and verify that all the analyzer readings meet this specification.

(4) For oxygen analyzers, you may use purified N2 as the zero gas and ambient air (plus purified

N2 if needed) as the reference gas. Perform the verification with seven repeat measurements that 

each consist of stabilizing with purified N2, switching to ambient air and observing the 

analyzer’s response rise and stabilized reading, followed by switching back to purified N2 and

observing the analyzer’s response fall and stabilized reading.

§1065.309 Continuous gas analyzer system-response and updating-recording verification—

for gas analyzers continuously compensated for other gas species. 

(a) Scope and frequency. This section describes a verification procedure for system response 

and updating-recording frequency for continuous gas analyzers that output a single gas species 

mole fraction (i.e., concentration) based on a continuous combination of multiple gas species 

measured with multiple detectors (i.e., gas analyzers continuously compensated for other gas 

species). See §1065.308 for verification procedures that apply to continuous gas analyzers that 

are not continuously compensated for other gas species or that use only one detector for gaseous 

species. Perform this verification to determine the system response of the continuous gas 

analyzer and its sampling system. This verification is required for continuous gas analyzers used 

for transient or ramped-modal testing. You need not perform this verification for batch gas 
analyzers or for continuous gas analyzers that are used only for discrete-mode testing. For this 

check we consider water vapor a gaseous constituent. This verification does not apply to any 

processing of individual analyzer signals that are time-aligned to their t50 times and were verified 

according to §1065.308. For example, this verification does not apply to correction for water 

removed from the sample done in post-processing according to §1065.659 (40 CFR 1066.640 for 

vehicle testing) and it does not apply to NMHC determination from THC and CH4 according to 

§1065.660. Perform this verification after initial installation (i.e., test cell commissioning) and 

after any modifications to the system that would change the system response. 

(b) Measurement principles. This procedure verifies that the updating and recording frequencies 

match the overall system response to a rapid change in the value of concentrations at the sample 

probe. It indirectly verifies the time-alignment and uniform response of all the continuous gas 

detectors used to generate a continuously combined/compensated concentration measurement 

signal. Gas analyzer systems must be optimized such that their overall response to rapid change 

in concentration is updated and recorded at an appropriate frequency to prevent loss of 

information. This test also verifies that the measurement system meets a minimum response 

time. For this procedure, ensure that all compensation algorithms and humidity corrections are 

turned on. You may use the results of this test to determine transformation time, t50, for the 

purposes of time alignment of continuous data in accordance with §1065.650(c)(2)(i). You may 

also use an alternate procedure to determine t50 consistent with good engineering judgment. 

Note that any such procedure for determining t50 must account for both transport delay and 

analyzer response time. 

(c) System requirements. Demonstrate that each continuously combined/compensated 

concentration measurement has adequate updating and recording frequencies and has a minimum 

rise time and a minimum fall time during a system response to a rapid change in multiple gas 

concentrations, including H2O concentration if H2O compensation is applied. You must meet 

one of the following criteria: 

(1) The product of the mean rise time, t10-90, and the frequency at which the system records an 

updated concentration must be at least 5, and the product of the mean fall time, t90-10, and the 

frequency at which the system records an updated concentration must be at least 5. If the 

recording frequency is different than the update frequency of the continuously 

combined/compensated signal, you must use the lower of these two frequencies for this 

verification. This criterion makes no assumption regarding the frequency content of changes in 

emission concentrations during emission testing; therefore, it is valid for any testing. Also, the 

mean rise time must be at or below 10 seconds and the mean fall time must be at or below 10 

seconds. 

(2) The frequency at which the system records an updated concentration must be at least 5 Hz. 

This criterion assumes that the frequency content of significant changes in emission 

concentrations during emission testing do not exceed 1 Hz. Also, the mean rise time must be at 

or below 10 seconds and the mean fall time must be at or below 10 seconds. 

(3) You may use other criteria if we approve them in advance. 

(4) You may meet the overall PEMS verification in §1065.920 instead of the verification in this 

section for field testing with PEMS. 

Deleted: time 

Deleted: 
(d) Procedure. Use the following procedure to verify the response of each continuously 

compensated analyzer (verify the combined signal, not each individual continuously combined 

concentration signal): 

(1) Instrument setup. Follow the analyzer manufacturer’s start-up and operating instructions. 

Adjust the measurement system as needed to optimize performance. Run this verification with 

the analyzer operating in the same manner you will use for emission testing. If the analyzer 

shares its sampling system with other analyzers, and if gas flow to the other analyzers will affect 

the system response time, then start up and operate the other analyzers while running this 

verification test. You may run this verification test on multiple analyzers sharing the same 

sampling system at the same time. If you use any analog or real-time digital filters during 

emission testing, you must operate those filters in the same manner during this verification. 

(2) Equipment setup. We recommend using minimal lengths of gas transfer lines between all 

connections and fast-acting three-way valves (2 inlets, 1 outlet) to control the flow of zero and 

blended span gases to the sample system’s probe inlet or a tee near the outlet of the probe. If you 

inject the gas at a tee near the outlet of the probe, you may correct the transformation time, t50, 

for an estimate of the transport time from the probe inlet to the tee. Normally the gas flow rate is 

higher than the sample flow rate and the excess is overflowed out the inlet of the probe. If the 

gas flow rate is lower than the sample flow rate, the gas concentrations must be adjusted to 

account for the dilution from ambient air drawn into the probe. We recommend you use the 

final, stabilized analyzer reading as the final gas concentration. Select span gases for the species 

being continuously combined, other than H2O. Select concentrations of compensating species 

that will yield concentrations of these species at the analyzer inlet that covers the range of 

concentrations expected during testing. You may use binary or multi-gas span gases. You may 

use a gas blending or mixing device to blend span gases. A gas blending or mixing device is 

recommended when blending span gases diluted in N2 with span gases diluted in air. You may 

use a multi-gas span gas, such as NO-CO-CO2-C3H8-CH4, to verify multiple analyzers at the 

same time. In designing your experimental setup, avoid pressure pulsations due to stopping the 

flow through the gas blending device. The change in gas concentration must be at least 20 % of 

the analyzer's range. If H2O correction is applicable, then span gases must be humidified before 

entering the analyzer; however, you may not humidify NO2 span gas by passing it through a 

sealed humidification vessel that contains water. You must humidify NO2 span gas with another 

moist gas stream. We recommend humidifying your NO-CO-CO2-C3H8-CH4, balance N2

blended gas by flowing the gas mixture through a sealed vessel that humidifies the gas by 

bubbling it through distilled water and then mixing the gas with dry NO2 gas, balance purified 

synthetic air. If your system does not use a sample dryer to remove water from the sample gas, 

you must humidify your span gas to the highest sample H2O content that you estimate during 

emission sampling. If your system uses a sample dryer during testing, it must pass the sample 

dryer verification check in §1065.342, and you must humidify your span gas to an H2O content

greater than or equal to the level determined in §1065.145(e)(2). If you are humidifying span 

gases without NO2, use good engineering judgment to ensure that the wall temperatures in the 

transfer lines, fittings, and valves from the humidifying system to the probe are above the 

dewpoint required for the target H2O content. If you are humidifying span gases with NO2, use 

good engineering judgment to ensure that there is no condensation in the transfer lines, fittings, 

or valves from the point where humidified gas is mixed with NO2 span gas to the probe. We 

Deleted: probe 

Deleted: probe 
recommend that you design your setup so that the wall temperatures in the transfer lines, fittings, 

and valves from the humidifying system to the probe are at least 5 oC above the local sample gas 

dewpoint. Operate the measurement and sample handling system as you do for emission testing. 

Make no modifications to the sample handling system to reduce the risk of condensation. Flow 

humidified gas through the sampling system before this check to allow stabilization of the 

measurement system’s sampling handling system to occur, as it would for an emission test. 

(3) Data collection. (i) Start the flow of zero gas. 

(ii) Allow for stabilization, accounting for transport delays and the slowest analyzer’s full 

response. 

(iii) Start recording data. For this verification you must record data at a frequency greater than or 

equal to that of the updating-recording frequency used during emission testing. You may not use 

interpolation or filtering to alter the recorded values. 

(iv) Switch the flow to allow the blended span gases to flow to the analyzer. If you intend to use 

the data from this test to determine t50 for time alignment, record this time as t0. 

(v) Allow for transport delays and the slowest analyzer’s full response. 

(vi) Switch the flow to allow zero gas to flow to the analyzer. If you intend to use the data from 

this test to determine t50 for time alignment, record this time as t100. 

(vii) Allow for transport delays and the slowest analyzer’s full response. 

(viii) Repeat the steps in paragraphs (d)(3)(iv) through (vii) of this section to record seven full 

cycles, ending with zero gas flowing to the analyzers. 

(ix) Stop recording. 

(e) Performance evaluations. (1) If you choose to demonstrate compliance with paragraph (c)(1) 

of this section, use the data from paragraph (d)(3) of this section to calculate the mean rise time, 

t10-90, and mean fall time, t90-10, for the continuously combined signal from each analyzer being 

verified. You may use interpolation between recorded values to determine rise and fall times. If 

the recording frequency used during emission testing is different from the analyzer’s output 

update frequency, you must use the lower of these two frequencies for this verification. Multiply 

these times (in seconds) by their respective updating-recording frequencies in Hz (1/second). The 

resulting product must be at least 5 for both rise time and fall time. If either value is less than 5, 

increase the updating-recording frequency or adjust the flows or design of the sampling system 

to increase the rise time and fall time as needed. You may also configure analog or digital filters 

before recording to increase rise and fall times. In no case may the mean rise time or mean fall 

time be greater than 10 seconds. 

(2) If a measurement system fails the criterion in paragraph (e)(1) of this section, ensure that 

signals from the system are updated and recorded at a frequency of at least 5 Hz. In no case may 

the mean rise time or mean fall time be greater than 10 seconds. 

(3) If a measurement system fails the criteria in paragraphs (e)(1) and (2) of this section, you 

may use the measurement system only if the deficiency does not adversely affect your ability to 

show compliance with the applicable standards. 

(f) Transformation time, t50, determination. If you choose to determine t50 for purposes of time 

alignment using data generated in paragraph (d)(3) of this section, calculate the mean t0-50 and 

the mean t100-50 from the recorded data. Average these two values to determine the final t50 for 

the purposes of time alignment in accordance with §1065.650(c)(2)(i).
(g) Optional procedure. Instead of using a three-way valve to switch between zero and span 

gases, you may use a fast acting two-way valve to switch sampling between ambient air at the 

inlet of the probe and span gas. For this alternate procedure, the following provisions apply:

(1) If your probe is sampling from a gas stream that is continuously flowing (e.g. a CVS tunnel), 

you may adjust the span gas flow rate to be different than the sample flow rate.

(2) If your probe is sampling from a gas stream that is not continuously flowing (e.g. a raw 

exhaust stack), you must adjust the span gas flow rate to be less than the sample flow rate so 

ambient air is always being drawn into the probe inlet. This avoids errors associated with 

overflowing span gas out the inlet of the probe and drawing it back in when sampling ambient 

air. 

(3) When sampling ambient air or ambient air mixed with span gas, all of the analyzer readings 

used to determine the final, stabilized gas concentration must be within ±0.5 % of the final gas 

concentration. If any analyzer reading is outside the specified range, you must resolve the 

problem and verify that all the analyzer readings meet this specification.

(4) For oxygen analyzers, you may use purified N2 as the zero gas and ambient air plus other 

compensating gases as the reference gas. Perform the verification with seven repeat 

measurements that each consist of stabilizing with purified N2, switching to ambient air plus 

other compensating gases and observing the analyzer rise and stabilized reading, followed by 

switching back to purified N2 and observing the analyzer’s fall and stabilized reading with 

purified N2.

(h) Analyzers with H2O compensation sampling downstream of a sample dryer. You may omit 

humidifying the span gas as described in this paragraph (h). If an analyzer compensates only for 

H2O, you may apply the requirements of §1065.308 instead of the requirements of this section.

You may omit humidifying the span gas if you meet the following conditions:

(1) The analyzer is located downstream of a sample dryer.

(2) The maximum value for continuous H2O mole fraction downstream of the dryer is never 

more than 0.010 greater than the minimum value. Verify this after each sample dryer

verification according to §1065.342.

MEASUREMENT OF ENGINE PARAMETERS AND AMBIENT CONDITIONS 

§1065.310 Torque calibration. 

(a) Scope and frequency. Calibrate all torque-measurement systems including dynamometer 

torque measurement transducers and systems upon initial installation and after major 

maintenance. Use good engineering judgment to repeat the calibration. Follow the torque 

transducer manufacturer’s instructions for linearizing your torque sensor’s output. We 

recommend that you calibrate the torque-measurement system with a reference force and a lever 

arm. 

(b) Recommended procedure. (1) Reference force quantification. Use either a set of deadweights or a reference meter such as strain gage or a proving ring to quantify the reference force, 

NIST-traceable within 0.5 % uncertainty. 

(2) Lever-arm length quantification. Quantify the lever arm length, NIST-traceable within 0.5 

% uncertainty. The lever arm’s length must be measured from the centerline of the 

dynamometer to the point at which the reference force is measured. The lever arm must be 
perpendicular to gravity (i.e., horizontal), and it must be perpendicular to the dynamometer’s 

rotational axis. Balance the lever arm’s torque or quantify its net hanging torque, NIST-traceable 

within 1 % uncertainty, and account for it as part of the reference torque. 

(c) Dead-weight calibration. This technique applies a known force by hanging known weights at 

a known distance along a lever arm. Make sure the weights’ lever arm is perpendicular to 

gravity (i.e., horizontal) and perpendicular to the dynamometer’s rotational axis. Apply at least 

six calibration-weight combinations for each applicable torque-measuring range, spacing the 

weight quantities about equally over the range. Oscillate or rotate the dynamometer during 

calibration to reduce frictional static hysteresis. Determine each weight’s force by multiplying its 

NIST-traceable mass by the local acceleration of Earth’s gravity (using this equation: force = 

mass · acceleration). The local acceleration of gravity, ag, at your latitude, longitude, and 

elevation may be determined by entering position and elevation data into the U.S. National 

Oceanographic and Atmospheric Administration’s surface gravity prediction website at 

http://www.ngs.noaa.gov/cgi-bin/grav_pdx.prl. If this website is unavailable, you may use the 

equation in §1065.630, which returns the local acceleration of gravity based on a given latitude. 

In this case, calculate the reference torque as the weights’ reference force multiplied by the lever 

arm reference length (using this equation: torque = force · lever arm length). 

(d) Strain gage, load transducer, or proving ring calibration. This technique applies force either 

by hanging weights on a lever arm (these weights and their lever arm length are not used as part 

of the reference torque determination) or by operating the dynamometer at different torques. 

Apply at least six force combinations for each applicable torque-measuring range, spacing the 

force quantities about equally over the range. Oscillate or rotate the dynamometer during 

calibration to reduce frictional static hysteresis. In this case, the reference torque is determined 

by multiplying the force output from the reference meter (such as a strain gage, load transducer,

or proving ring) by its effective lever-arm length, which you measure from the point where the 

force measurement is made to the dynamometer’s rotational axis. Make sure you measure this 

length perpendicular to the reference meter’s measurement axis and perpendicular to the 

dynamometer’s rotational axis. 

§1065.315 Pressure, temperature, and dewpoint calibration. 

(a) Calibrate instruments for measuring pressure, temperature, and dewpoint upon initial 

installation. Follow the instrument manufacturer’s instructions and use good engineering 

judgment to repeat the calibration, as follows: 

(1) Pressure. We recommend temperature-compensated, digital-pneumatic, or deadweight 

pressure calibrators, with data-logging capabilities to minimize transcription errors. We 

recommend using calibration reference quantities that are NIST-traceable within 0.5 % 

uncertainty. 

(2) Temperature. We recommend digital dry-block or stirred-liquid temperature calibrators, with 

data logging capabilities to minimize transcription errors. We recommend using calibration 

reference quantities that are NIST-traceable within 0.5 % uncertainty. You may perform 

linearity verification for temperature measurement systems with thermocouples, RTDs, and 

thermistors by removing the sensor from the system and using a simulator in its place. Use a 

NIST-traceable simulator that is independently calibrated and, as appropriate, cold-junction 

compensated. The simulator uncertainty scaled to absolute temperature must be less than 0.5 % 

Deleted: the 
of Tmax. If you use this option, you must use sensors that the supplier states are accurate to better 

than 0.5 % of Tmax compared with their standard calibration curve. 

(3) Dewpoint. We recommend a minimum of three different temperature-equilibrated and 

temperature-monitored calibration salt solutions in containers that seal completely around the 

dewpoint sensor. We recommend using calibration reference quantities that are NIST-traceable 

within 0.5 % uncertainty. 

(b) You may remove system components for off-site calibration. We recommend specifying 

calibration reference quantities that are NIST-traceable within 0.5 % uncertainty. 

FLOW-RELATED MEASUREMENTS 

§1065.320 Fuel-flow calibration. 

(a) Calibrate fuel-flow meters upon initial installation. Follow the instrument manufacturer’s 

instructions and use good engineering judgment to repeat the calibration. 

(b) You may also develop a procedure based on a chemical balance of carbon or oxygen in 

engine exhaust. 

(c) You may remove system components for off-site calibration. When installing a flow meter 

with an off-site calibration, we recommend that you consider the effects of the tubing 

configuration upstream and downstream of the flow meter. We recommend specifying 

calibration reference quantities that are NIST-traceable within 0.5 % uncertainty. 

§1065.325 Intake-flow calibration. 

(a) Calibrate intake-air flow meters upon initial installation. Follow the instrument 

manufacturer’s instructions and use good engineering judgment to repeat the calibration. We 

recommend using a calibration subsonic venturi, ultrasonic flow meter or laminar flow element. 

We recommend using calibration reference quantities that are NIST-traceable within 0.5 % 

uncertainty. 

(b) You may remove system components for off-site calibration. When installing a flow meter 

with an off-site calibration, we recommend that you consider the effects of the tubing 

configuration upstream and downstream of the flow meter. We recommend specifying 

calibration reference quantities that are NIST-traceable within 0.5 % uncertainty. 

(c) If you use a subsonic venturi or ultrasonic flow meter for intake flow measurement, we 

recommend that you calibrate it as described in §1065.340. 

§1065.330 Exhaust-flow calibration. 

(a) Calibrate exhaust-flow meters upon initial installation. Follow the instrument manufacturer’s 

instructions and use good engineering judgment to repeat the calibration. We recommend that 

you use a calibration subsonic venturi or ultrasonic flow meter and simulate exhaust 

temperatures by incorporating a heat exchanger between the calibration meter and the exhaustflow meter. If you can demonstrate that the flow meter to be calibrated is insensitive to exhaust 

temperatures, you may use other reference meters such as laminar flow elements, which are not 

commonly designed to withstand typical raw exhaust temperatures. We recommend using 

calibration reference quantities that are NIST-traceable within 0.5 % uncertainty. 
(b) You may remove system components for off-site calibration. When installing a flow meter 

with an off-site calibration, we recommend that you consider the effects of the tubing 

configuration upstream and downstream of the flow meter. We recommend specifying 

calibration reference quantities that are NIST-traceable within 0.5 % uncertainty. 

(c) If you use a subsonic venturi or ultrasonic flow meter for raw exhaust flow measurement, we 

recommend that you calibrate it as described in §1065.340. 

§1065.340 Diluted exhaust flow (CVS) calibration. 

(a) Overview. This section describes how to calibrate flow meters for diluted exhaust constantvolume sampling (CVS) systems.

(b) Scope and frequency. Perform this calibration while the flow meter is installed in its 

permanent position, except as allowed in paragraph (c) of this section. Perform this calibration 

after you change any part of the flow configuration upstream or downstream of the flow meter 

that may affect the flow-meter calibration. Perform this calibration upon initial CVS installation 

and whenever corrective action does not resolve a failure to meet the diluted exhaust flow 

verification (i.e., propane check) in §1065.341. 

(c) Ex-situ CFV and SSV calibration. You may remove a CFV or SSV from its permanent 

position for calibration as long as it meets the following requirements when installed in the CVS: 

(1) Upon installation of the CFV or SSV into the CVS, use good engineering judgment to verify 

that you have not introduced any leaks between the CVS inlet and the venturi. 

(2) After ex-situ venturi calibration, you must verify all venturi flow combinations for CFVs or 

at minimum of 10 flow points for an SSV using the propane check as described in §1065.341. 

Your propane check result for each venturi flow point may not exceed the tolerance in 

§1065.341(f)(5). 

(3) To verify your ex-situ calibration for a CVS with more than a single CFV, perform the 

following check to verify that there are no flow meter entrance effects that can prevent you from 

passing this verification. 

(i) Use a constant flow device like a CFO kit to deliver a constant flow of propane to the dilution 

tunnel. 

(ii) Measure hydrocarbon concentrations at a minimum of 10 separate flow rates for an SSV flow 

meter, or at all possible flow combinations for a CFV flow meter, while keeping the flow of 

propane constant. We recommend selecting CVS flow rates in a random order. 

(iii) Measure the concentration of hydrocarbon background in the dilution air at the beginning 

and end of this test. Subtract the average background concentration from each measurement at 

each flow point before performing the regression analysis in paragraph (c)(3)(iv) of this section. 

(iv) Perform a power regression using all the paired values of flow rate and corrected 

concentration to obtain a relationship in the form of y = a · x

b

. Use concentration as the 

independent variable and flow rate as the dependent variable. For each data point, calculate the 

difference between the measured flow rate and the value represented by the curve fit. The 

difference at each point must be less than ±1 % of the appropriate regression value. The value of 

b must be between –1.005 and –0.995. If your results do not meet these limits, take corrective 

action consistent with §1065.341(a). 

(v) If your results do not meet the limits set in paragraph (iv) of this section, determine the 

source of error, which are described in §1065.341(a), and take corrective action as necessary. 
(d) Reference flow meter. Calibrate a CVS flow meter using a reference flow meter such as a 

subsonic venturi flow meter, a long-radius ASME/NIST flow nozzle, a smooth approach orifice, 

a laminar flow element, a set of critical flow venturis, or an ultrasonic flow meter. Use a 

reference flow meter that reports quantities that are NIST-traceable within ±1 % uncertainty. 

Use this reference flow meter’s response to flow as the reference value for CVS flow-meter 

calibration. 

(e) Configuration. Do not use an upstream screen or other restriction that could affect the flow 

ahead of the reference flow meter, unless the flow meter has been calibrated with such a 

restriction. 

(f) PDP calibration. Calibrate a positive-displacement pump (PDP) to determine a flow-versusPDP speed equation that accounts for flow leakage across sealing surfaces in the PDP as a 

function of PDP inlet pressure. Determine unique equation coefficients for each speed at which 

you operate the PDP. Calibrate a PDP flow meter as follows: 

(1) Connect the system as shown in Figure 1 of this section. 

(2) Leaks between the calibration flow meter and the PDP must be less than 0.3 % of the total 

flow at the lowest calibrated flow point; for example, at the highest restriction and lowest PDPspeed point. 

(3) While the PDP operates, maintain a constant temperature at the PDP inlet within ±2 % of the 

mean absolute inlet temperature, Tin . 

(4) Set the PDP speed to the first speed point at which you intend to calibrate. 

(5) Set the variable restrictor to its wide-open position. 

(6) Operate the PDP for at least 3 min to stabilize the system. Continue operating the PDP and 

record the mean values of at least 30 seconds of sampled data of each of the following quantities: 

(i) The mean flow rate of the reference flow meter, ref n . This may include several measurements 

of different quantities, such as reference meter pressures and temperatures, for calculating ref n . 

(ii) The mean temperature at the PDP inlet, Tin . 

(iii) The mean static absolute pressure at the PDP inlet, in p . 

(iv) The mean static absolute pressure at the PDP outlet, out p . 

(v) The mean PDP speed, nPDP f . 

(7) Incrementally close the restrictor valve to decrease the absolute pressure at the inlet to the 

PDP, in p . 

(8) Repeat the steps in paragraphs (e)(6) and (7) of this section to record data at a minimum of 

six restrictor positions ranging from the wide open restrictor position to the minimum expected 

pressure at the PDP inlet. 

(9) Calibrate the PDP by using the collected data and the equations in §1065.640. 

(10) Repeat the steps in paragraphs (e)(6) through (9) of this section for each speed at which you 

operate the PDP. 

(11) Use the equations in §1065.642 to determine the PDP flow equation for emission testing. 

(12) Verify the calibration by performing a CVS verification (i.e., propane check) as described in 

§1065.341. 

(13) Do not use the PDP below the lowest inlet pressure tested during calibration. 
(g) CFV calibration. Calibrate a critical-flow venturi (CFV) to verify its discharge coefficient, 

Cd, at the lowest expected static differential pressure between the CFV inlet and outlet. Calibrate 

a CFV flow meter as follows: 

(1) Connect the system as shown in Figure 1 of this section. 

(2) Verify that any leaks between the calibration flow meter and the CFV are less than 0.3 % of 

the total flow at the highest restriction. 

(3) Start the blower downstream of the CFV. 

(4) While the CFV operates, maintain a constant temperature at the CFV inlet within ±2 % of the 

mean absolute inlet temperature, Tin . 

(5) Set the variable restrictor to its wide-open position. Instead of a variable restrictor, you may 

alternately vary the pressure downstream of the CFV by varying blower speed or by introducing 

a controlled leak. Note that some blowers have limitations on nonloaded conditions. 

(6) Operate the CFV for at least 3 min to stabilize the system. Continue operating the CFV and 

record the mean values of at least 30 seconds of sampled data of each of the following quantities: 

(i) The mean flow rate of the reference flow meter, ref n . This may include several measurements 

of different quantities, such as reference meter pressures and temperatures, for calculating ref n . 

(ii) The mean dewpoint of the calibration air, Tdew . See §1065.640 for permissible assumptions 

during emission measurements. 

(iii) The mean temperature at the venturi inlet, Tin . 

(iv) The mean static absolute pressure at the venturi inlet, in p .

(v) The mean static differential pressure between the CFV inlet and the CFV outlet, CFV p . 

(7) Incrementally close the restrictor valve or decrease the downstream pressure to decrease the 

differential pressure across the CFV, CFV p . 

(8) Repeat the steps in paragraphs (f)(6) and (7) of this section to record mean data at a minimum 

of ten restrictor positions, such that you test the fullest practical range of CFV p expected during 

testing. We do not require that you remove calibration components or CVS components to 

calibrate at the lowest possible restrictions. 

(9) Determine Cd and the lowest allowable pressure ratio, r, according to §1065.640. 

(10) Use Cd to determine CFV flow during an emission test. Do not use the CFV below the 

lowest allowed r, as determined in §1065.640. 

(11) Verify the calibration by performing a CVS verification (i.e., propane check) as described in 

§1065.341. 

(12) If your CVS is configured to operate more than one CFV at a time in parallel, calibrate your 

CVS by one of the following: 

(i) Calibrate every combination of CFVs according to this section and §1065.640. Refer to 

§1065.642 for instructions on calculating flow rates for this option. 

(ii) Calibrate each CFV according to this section and §1065.640. Refer to §1065.642 for 

instructions on calculating flow rates for this option. 

(h) SSV calibration. Calibrate a subsonic venturi (SSV) to determine its calibration coefficient,

Cd, for the expected range of inlet pressures. Calibrate an SSV flow meter as follows: 

(1) Connect the system as shown in Figure 1 of this section. 
(2) Verify that any leaks between the calibration flow meter and the SSV are less than 0.3 % of 

the total flow at the highest restriction. 

(3) Start the blower downstream of the SSV. 

(4) While the SSV operates, maintain a constant temperature at the SSV inlet within ±2 % of the 

mean absolute inlet temperature, Tin . 

(5) Set the variable restrictor or variable-speed blower to a flow rate greater than the greatest 

flow rate expected during testing. You may not extrapolate flow rates beyond calibrated values, 

so we recommend that you make sure the Reynolds number, Re#

, at the SSV throat at the greatest 

calibrated flow rate is greater than the maximum Re#

 expected during testing. 

(6) Operate the SSV for at least 3 min to stabilize the system. Continue operating the SSV and 

record the mean of at least 30 seconds of sampled data of each of the following quantities: 

(i) The mean flow rate of the reference flow meter ref n . This may include several measurements 

of different quantities, such as reference meter pressures and temperatures, for calculating ref n . 

(ii) Optionally, the mean dewpoint of the calibration air, Tdew . See §1065.640 for permissible 

assumptions. 

(iii) The mean temperature at the venturi inlet, Tin . 

(iv) The mean static absolute pressure at the venturi inlet, in p . 

(v) Static differential pressure between the static pressure at the venturi inlet and the static 

pressure at the venturi throat, SSV p . 

(7) Incrementally close the restrictor valve or decrease the blower speed to decrease the flow 

rate. 

(8) Repeat the steps in paragraphs (g)(6) and (7) of this section to record data at a minimum of 

ten flow rates. 

(9) Determine a functional form of Cd versus Re# by using the collected data and the equations in 

§1065.640. 

(10) Verify the calibration by performing a CVS verification (i.e., propane check) as described in 

§1065.341 using the new Cd versus Re# equation. 

(11) Use the SSV only between the minimum and maximum calibrated flow rates. 

(12) Use the equations in §1065.642 to determine SSV flow during a test. 

(i) Ultrasonic flow meter calibration. [Reserved] 
Figure 1 of 1065.340—CVS calibration configurations. 

reference

flow meter PDP

variable

restrictor

12

6

ref n

atmos p

in p out p Tin

PDP f

t

reference

flow meter PDP

variable

restrictor

12

6

ref n

atmos p

in p out p Tin

PDP f

t

reference

flow meter PDP

variable

restrictor

12

6

ref n

atmos p

in p out p Tin

PDP f

t

reference CFV

flow meter

variable

restrictor

ref n in p Tin

atmos p Tdew

blower

downstream

pressure

control

reference CFV

flow meter

variable

restrictor

ref n in p Tin

atmos p Tdew

blower

downstream

pressure

control

reference SSV

flow meter

ref n

atmos p

in p Tin

Tdew

p

variable speed

blower

reference SSV

flow meter

ref n

atmos p

in p Tin

Tdew

p

variable speed

blower
§1065.341 CVS, PFD, and batch sampler verification (propane check). 

(a) A propane check serves as a CVS verification to determine if there is a discrepancy in 

measured values of diluted exhaust flow. You may use the same procedure to verify PFDs and 

batch samplers. For purposes of PFD and batch sampler verification, read the term CVS to mean 

PFD or batch sampler as appropriate. A propane check also serves as a batch-sampler 

verification to determine if there is a discrepancy in a batch sampling system that extracts a 

sample from a CVS, as described in paragraph (g) of this section. Using good engineering 

judgment and safe practices, this check may be performed using a gas other than propane, such 

as CO2 or CO. A failed propane check might indicate one or more problems that may require 

corrective action, as follows: 

(1) Incorrect analyzer calibration. Re-calibrate, repair, or replace the FID analyzer. 

(2) Leaks. Inspect CVS tunnel, connections, fasteners, and HC sampling system, and repair or 

replace components. 

(3) Poor mixing. Perform the verification as described in this section while traversing a 

sampling probe across the tunnel’s diameter, vertically and horizontally. If the analyzer response 

indicates any deviation exceeding 2 % of the mean measured concentration, consider operating 

the CVS at a higher flow rate or installing a mixing plate or orifice to improve mixing. 

(4) Hydrocarbon contamination in the sample system. Perform the hydrocarbon-contamination 

verification as described in §1065.520. 

(5) Change in CVS calibration. Perform a calibration of the CVS flow meter as described in 

§1065.340. 

(6) Flow meter entrance effects. Inspect the CVS tunnel to determine whether the entrance 

effects from the piping configuration upstream of the flow meter adversely affect the flow 

measurement. 

(7) Other problems with the CVS or sampling verification hardware or software. Inspect the 

CVS system, CVS verification hardware, and software for discrepancies. 

(b) A propane check uses either a reference mass or a reference flow rate of C3H8 as a tracer gas 

in a CVS. Note that if you use a reference flow rate, account for any non-ideal gas behavior of 

C3H8 in the reference flow meter. Refer to §1065.640 and §1065.642, which describe how to 

calibrate and use certain flow meters. Do not use any ideal gas assumptions in §1065.640 and 

§1065.642. The propane check compares the calculated mass of injected C3H8 using HC 

measurements and CVS flow rate measurements with the reference value. 

(c) Prepare for the propane check as follows: 

(1) If you use a reference mass of C3H8 instead of a reference flow rate, obtain a cylinder 

charged with C3H8. Determine the reference cylinder’s mass of C3H8 within 0.5 % of the 

amount of C3H8 that you expect to use. 

(2) Select appropriate flow rates for the CVS and C3H8. 

(3) Select a C3H8 injection port in the CVS. Select the port location to be as close as practical to 

the location where you introduce engine exhaust into the CVS. Connect the C3H8 cylinder to the 

injection system. 

(4) Operate and stabilize the CVS. 

(5) Preheat or pre-cool any heat exchangers in the sampling system. 

(6) Allow heated and cooled components such as sample lines, filters, chillers, and pumps to 

stabilize at operating temperature. 
(7) You may purge the HC sampling system during stabilization. 

(8) If applicable, perform a vacuum side leak verification of the HC sampling system as 

described in §1065.345. 

(9) You may also conduct any other calibrations or verifications on equipment or analyzers. 

(d) If you performed the vacuum-side leak verification of the HC sampling system as described 

in paragraph (c)(8) of this section, you may use the HC contamination procedure in §1065.520(f) 

to verify HC contamination. Otherwise, zero, span, and verify contamination of the HC sampling 

system, as follows: 

(1) Select the lowest HC analyzer range that can measure the C3H8 concentration expected for 

the CVS and C3H8 flow rates. 

(2) Zero the HC analyzer using zero air introduced at the analyzer port. 

(3) Span the HC analyzer using C3H8 span gas introduced at the analyzer port. 

(4) Overflow zero air at the HC probe inlet or into a tee near the outlet of the probe. 

(5) Measure the stable HC concentration of the HC sampling system as overflow zero air flows. 

For batch HC measurement, fill the batch container (such as a bag) and measure the HC 

overflow concentration. 

(6) If the overflow HC concentration exceeds 2 mol/mol, do not proceed until contamination is 

eliminated. Determine the source of the contamination and take corrective action, such as 

cleaning the system or replacing contaminated portions. 

(7) When the overflow HC concentration does not exceed 2 mol/mol, record this value as 

xTHCinit and use it to correct for HC contamination as described in §1065.660. 

(e) Perform the propane check as follows: 

(1) For batch HC sampling, connect clean storage media, such as evacuated bags. 

(2) Operate HC measurement instruments according to the instrument manufacturer’s 

instructions. 

(3) If you will correct for dilution air background concentrations of HC, measure and record 

background HC in the dilution air. 

(4) Zero any integrating devices. 

(5) Begin sampling, and start any flow integrators. 

(6) Release the contents of the C3H8 reference cylinder at the rate you selected. If you use a 

reference flow rate of C3H8, start integrating this flow rate. 

(7) Continue to release the cylinder’s contents until at least enough C3H8 has been released to 

ensure accurate quantification of the reference C3H8 and the measured C3H8. 

(8) Shut off the C3H8 reference cylinder and continue sampling until you have accounted for time 

delays due to sample transport and analyzer response. 

(9) Stop sampling and stop any integrators. 

(f) Perform post-test procedure as follows: 

(1) If you used batch sampling, analyze batch samples as soon as practical. 

(2) After analyzing HC, correct for contamination and background. 

(3) Calculate total C3H8 mass based on your CVS and HC data as described in §1065.650 (40 

CFR 1066.610 for vehicle testing) and §1065.660, using the molar mass of C3H8, MC3H8, instead 

the effective molar mass of HC, MHC. 

Deleted: g
(4) If you use a reference mass, determine the cylinder’s propane mass within 0.5 % and 

determine the C3H8 reference mass by subtracting the empty cylinder propane mass from the full 

cylinder propane mass. 

(5) Subtract the reference C3H8 mass from the calculated mass. If this difference is within 2 % 

of the reference mass, the CVS passes this verification. If not, take corrective action as 

described in paragraph (a) of this section. 

(g) You may repeat the propane check to verify a batch sampler, such as a PM secondary dilution 

system. 

(1) Configure the HC sampling system to extract a sample near the location of the batch 

sampler’s storage media (such as a PM filter). If the absolute pressure at this location is too low 

to extract an HC sample, you may sample HC from the batch sampler pump’s exhaust. Use 

caution when sampling from pump exhaust because an otherwise acceptable pump leak 

downstream of a batch sampler flow meter will cause a false failure of the propane check. 

(2) Repeat the propane check described in this section, but sample HC from the batch sampler. 

(3) Calculate C3H8 mass, taking into account any secondary dilution from the batch sampler. 

(4) Subtract the reference C3H8 mass from the calculated mass. If this difference is within 5 % 

of the reference mass, the batch sampler passes this verification. If not, take corrective action as 

described in paragraph (a) of this section. 

§1065.342 Sample dryer verification.

(a) Scope and frequency. If you use a sample dryer as allowed in §1065.145(e)(2) to remove 

water from the sample gas, verify the performance upon installation, after major maintenance, 

for thermal chiller. For osmotic membrane dryers, verify the performance upon installation, after 

major maintenance, and within 35 days of testing. 

(b) Measurement principles. Water can inhibit an analyzer’s ability to properly measure the 

exhaust component of interest and thus is sometimes removed before the sample gas reaches the 

analyzer. For example water can negatively interfere with a CLD’s NOx response through 

collisional quenching and can positively interfere with an NDIR analyzer by causing a response 

similar to CO. 

(c) System requirements. The sample dryer must meet the specifications as determined in 

§1065.145(e)(2) for dewpoint, Tdew, and absolute pressure, ptotal, downstream of the osmoticmembrane dryer or thermal chiller. 

(d) Sample dryer verification procedure. Use the following method to determine sample dryer 

performance. Run this verification with the dryer and associated sampling system operating in 

the same manner you will use for emission testing (including operation of sample pumps). You 

may run this verification test on multiple sample dryers sharing the same sampling system at the 

same time. You may run this verification on the sample dryer alone, but you must use the 

maximum gas flow rate expected during testing. You may use good engineering judgment to 

develop a different protocol. 

(1) Use PTFE or stainless steel tubing to make necessary connections. 

(2) Humidify room air, N2, or purified air by bubbling it through distilled water in a sealed vessel 

that humidifies the gas to the highest sample water content that you estimate during emission 

sampling. 
(3) Introduce the humidified gas upstream of the sample dryer. You may disconnect the transfer 

line from the probe and introduce the humidified gas at the inlet of the transfer line of the sample 

system used during testing. You may use the sample pumps in the sample system to draw gas 

through the vessel. 

(4) Maintain the sample lines, fittings, and valves from the location where the humidified gas 

water content is measured to the inlet of the sampling system at a temperature at least 5 oC above 

the local humidified gas dewpoint. For dryers used in NOx sample systems, verify the sample 

system components used in this verification prevent aqueous condensation as required in 

§1065.145(d)(1)(i). We recommend that the sample system components be maintained at least 5 

oC above the local humidified gas dewpoint to prevent aqueous condensation. 

(5) Measure the humidified gas dewpoint, Tdew, and absolute pressure, ptotal, as close as possible 

to the inlet of the sample dryer or inlet of the sample system to verify the water content is at least 

as high as the highest value that you estimated during emission sampling. You may verify the 

water content based on any humidity parameter (e.g. mole fraction water, local dewpoint, or 

absolute humidity). 

(6) Measure the humidified gas dewpoint, Tdew, and absolute pressure, ptotal, as close as possible 

to the outlet of the sample dryer. Note that the dewpoint changes with absolute pressure. If the 

dewpoint at the sample dryer outlet is measured at a different pressure, then this reading must be 

corrected to the dewpoint at the sample dryer absolute pressure, ptotal. 

(7) The sample dryer meets the verification if the dewpoint at the sample dryer pressure as 

measured in paragraph (d)(6) of this section is less than the dewpoint corresponding to the 

sample dryer specifications as determined in §1065.145(e)(2) plus 2 °C or if the mole fraction of 

water as measured in (d)(6) is less than the corresponding sample dryer specifications plus 0.002 

mol/mol. 

(e) Alternate sample dryer verification procedure. The following method may be used in place 

of the sample dryer verification procedure in (d) of this section. If you use a humidity sensor for 

continuous monitoring of dewpoint at the sample dryer outlet you may skip the performance 

check in §1065.342(d), but you must make sure that the dryer outlet humidity is at or below the 

minimum value used for quench, interference, and compensation checks. 

§1065.345 Vacuum-side leak verification. 

(a) Scope and frequency. Verify that there are no significant vacuum-side leaks using one of the 

leak tests described in this section. For laboratory testing, perform the vacuum-side leak 

verification upon initial sampling system installation, within 8 hours before the start of the first 

test interval of each duty-cycle sequence, and after maintenance such as pre-filter changes. For 

field testing, perform the vacuum-side leak verification after each installation of the sampling 

system on the vehicle, prior to the start of the field test, and after maintenance such as pre-filter 

changes. This verification does not apply to any full-flow portion of a CVS dilution system. 

(b) Measurement principles. A leak may be detected either by measuring a small amount of flow 

when there should be zero flow, or by detecting the dilution of a known concentration of span 

gas when it flows through the vacuum side of a sampling system. 

(c) Low-flow leak test. Test a sampling system for low-flow leaks as follows: 

(1) Seal the probe end of the system by taking one of the following steps: 

(i) Cap or plug the end of the sample probe. 
(ii) Disconnect the transfer line at the probe and cap or plug the transfer line. 

(iii) Close a leak-tight valve located in the sample transfer line within 92 cm of the probe. 

(2) Operate all vacuum pumps. After stabilizing, verify that the flow through the vacuum-side of 

the sampling system is less than 0.5 % of the system’s normal in-use flow rate. You may 

estimate typical analyzer and bypass flows as an approximation of the system’s normal in-use 

flow rate. 

(d) Dilution-of-span-gas leak test. You may use any gas analyzer for this test. If you use a FID 

for this test, correct for any HC contamination in the sampling system according to §1065.660. 

To avoid misleading results from this test, we recommend using only analyzers that have a 

repeatability of 0.5% or better at the span gas concentration used for this test. Perform a 

vacuum-side leak test as follows: 

(1) Prepare a gas analyzer as you would for emission testing. 

(2) Supply span gas to the analyzer port and verify that it measures the span gas concentration 

within its expected measurement accuracy and repeatability. 

(3) Route overflow span gas to the inlet of the sample probe or at a tee fitting in the transfer line 

near the exit of the probe. You may use a valve upstream of the overflow fitting to prevent 

overflow of span gas out of the inlet of the probe, but you must then provide an overflow vent in 

the overflow supply line. 

(4) Verify that the measured overflow span gas concentration is within ±0.5% of the span gas 

concentration. A measured value lower than expected indicates a leak, but a value higher than 

expected may indicate a problem with the span gas or the analyzer itself. A measured value 

higher than expected does not indicate a leak. 

(e) Vacuum-decay leak test. To perform this test you must apply a vacuum to the vacuum-side 

volume of your sampling system and then observe the leak rate of your system as a decay in the 

applied vacuum. To perform this test you must know the vacuum-side volume of your sampling 

system to within ±10% of its true volume. For this test you must also use measurement 

instruments that meet the specifications of subpart C of this part and of this subpart D. Perform a 

vacuum-decay leak test as follows: 

(1) Seal the probe end of the system as close to the probe opening as possible by taking one of 

the following steps: 

(i) Cap or plug the end of the sample probe. 

(ii) Disconnect the transfer line at the probe and cap or plug the transfer line. 

(iii) Close a leak-tight valve located in the sample transfer line within 92 cm of the probe. 

(2) Operate all vacuum pumps. Draw a vacuum that is representative of normal operating 

conditions. In the case of sample bags, we recommend that you repeat your normal sample bag 

pump-down procedure twice to minimize any trapped volumes. 

(3) Turn off the sample pumps and seal the system. Measure and record the absolute pressure of 

the trapped gas and optionally the system absolute temperature. Wait long enough for any 

transients to settle and long enough for a leak at 0.5% to have caused a pressure change of at 

least 10 times the resolution of the pressure transducer, then again record the pressure and 

optionally temperature. 

(4) Calculate the leak flow rate based on an assumed value of zero for pumped-down bag 

volumes and based on known values for the sample system volume, the initial and final 

pressures, optional temperatures, and elapsed time. Using the calculations specified in 1065.644, 
verify that the vacuum-decay leak flow rate is less than 0.5 % of the system’s normal in-use flow 

rate. 

CO AND CO2 MEASUREMENTS 

§1065.350 H2O interference verification for CO2 NDIR analyzers. 

(a) Scope and frequency. If you measure CO2 using an NDIR analyzer, verify the amount of 

H2O interference after initial analyzer installation and after major maintenance. 

(b) Measurement principles. H2O can interfere with an NDIR analyzer’s response to CO2. If the 

NDIR analyzer uses compensation algorithms that utilize measurements of other gases to meet 

this interference verification, simultaneously conduct these other measurements to test the 

compensation algorithms during the analyzer interference verification. 

(c) System requirements. A CO2 NDIR analyzer must have an H2O interference that is within 

(0.0 ±0.4) mmol/mol, though we strongly recommend a lower interference that is within (0.0 

±0.2) mmol/mol. 

(d) Procedure. Perform the interference verification as follows: 

(1) Start, operate, zero, and span the CO2 NDIR analyzer as you would before an emission test. 

If the sample is passed through a dryer during emission testing, you may run this verification test 

with the dryer if it meets the requirements of §1065.342. Operate the dryer at the same 

conditions as you will for an emission test. You may also run this verification test without the 

sample dryer. 

(2) Create a humidified test gas by bubbling zero gas that meets the specifications in §1065.750 

through distilled H2O in a sealed vessel. If the sample is not passed through a dryer during 

emission testing, control the vessel temperature to generate an H2O level at least as high as the 

maximum expected during emission testing. If the sample is passed through a dryer during 

emission testing, control the vessel temperature to generate an H2O level at least as high as the 

level determined in §1065.145(e)(2) for that dryer. 

(3) Introduce the humidified test gas into the sample system. You may introduce it downstream 

of any sample dryer, if one is used during testing. 

(4) If the sample is not passed through a dryer during this verification test, measure the H2O

mole fraction, xH2O, of the humidified test gas, as close as possible to the inlet of the analyzer. 

For example, measure dewpoint, Tdew, and absolute pressure, ptotal, to calculate xH2O. Verify that 

the H2O content meets the requirement in paragraph (d)(2) of this section. If the sample is 

passed through a dryer during this verification test, you must verify that the H2O content of the 

humidified test gas downstream of the vessel meets the requirement in paragraph (d)(2) of this 

section based on either direct measurement of the H2O content (e.g., dewpoint and pressure) or 

an estimate based on the vessel pressure and temperature. Use good engineering judgment to 

estimate the H2O content. For example, you may use previous direct measurements of H2O

content to verify the vessel’s level of saturation. 

(5) If a sample dryer is not used in this verification test, use good engineering judgment to 

prevent condensation in the transfer lines, fittings, or valves from the point where xH2O is 

measured to the analyzer. We recommend that you design your system so the wall temperatures 

in the transfer lines, fittings, and valves from the point where xH2O is measured to the analyzer 

are at least 5 oC above the local sample gas dewpoint. 

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(6) Allow time for the analyzer response to stabilize. Stabilization time may include time to 

purge the transfer line and to account for analyzer response. 

(7) While the analyzer measures the sample’s concentration, record 30 seconds of sampled data. 

Calculate the arithmetic mean of this data. The analyzer meets the interference verification if 

this value is within (0.0 ±0.4) mmol/mol. 

(e) Exceptions. The following exceptions apply: 

(1) You may omit this verification if you can show by engineering analysis that for your CO2

sampling system and your emission-calculation procedures, the H2O interference for your CO2

NDIR analyzer always affects your brake-specific emission results within 0.5 % of each of the 

applicable standards. This specification also applies for vehicle testing, except that it relates to 

emission results in g/mile or g/kilometer.

(2) You may use a CO2 NDIR analyzer that you determine does not meet this verification, as 

long as you try to correct the problem and the measurement deficiency does not adversely affect 

your ability to show that engines comply with all applicable emission standards. 

§1065.355 H2O and CO2 interference verification for CO NDIR analyzers. 

(a) Scope and frequency. If you measure CO using an NDIR analyzer, verify the amount of H2O 

and CO2 interference after initial analyzer installation and after major maintenance. 

(b) Measurement principles. H2O and CO2 can positively interfere with an NDIR analyzer by 

causing a response similar to CO. If the NDIR analyzer uses compensation algorithms that 

utilize measurements of other gases to meet this interference verification, simultaneously 

conduct these other measurements to test the compensation algorithms during the analyzer 

interference verification. 

(c) System requirements. A CO NDIR analyzer must have combined H2O and CO2 interference 

that is within 2 % of the flow-weighted mean concentration of CO expected at the standard, 

though we strongly recommend a lower interference that is within 1 %. 

(d) Procedure. Perform the interference verification as follows: 

(1) Start, operate, zero, and span the CO NDIR analyzer as you would before an emission test. If 

the sample is passed through a dryer during emission testing, you may run this verification test 

with the dryer if it meets the requirements of §1065.342. Operate the dryer at the same 

conditions as you will for an emission test. You may also run this verification test without the 

sample dryer. 

(2) Create a humidified CO2 test gas by bubbling a CO2 span gas that meets the specifications in 

§1065.750 through distilled H2O in a sealed vessel. If the sample is not passed through a dryer 

during emission testing, control the vessel temperature to generate an H2O level at least as high 

as the maximum expected during emission testing. If the sample is passed through a dryer 

during emission testing, control the vessel temperature to generate an H2O level at least as high 

as the level determined in §1065.145(e)(2) for that dryer. Use a CO2 span gas concentration at 

least as high as the maximum expected during testing. 

(3) Introduce the humidified CO2 test gas into the sample system. You may introduce it 

downstream of any sample dryer, if one is used during testing. 

(4) If the sample is not passed through a dryer during this verification test, measure the H2O

mole fraction, xH2O, of the humidified CO2 test gas as close as possible to the inlet of the 

analyzer. For example, measure dewpoint, Tdew, and absolute pressure, ptotal, to calculate xH2O. 

Deleted: water 

Deleted: water 
Verify that the H2O content meets the requirement in paragraph (d)(2) of this section. If the 

sample is passed through a dryer during this verification test, you must verify that the H2O

content of the humidified test gas downstream of the vessel meets the requirement in paragraph 

(d)(2) of this section based on either direct measurement of the H2O content (e.g., dewpoint and 

pressure) or an estimate based on the vessel pressure and temperature. Use good engineering 

judgment to estimate the H2O content. For example, you may use previous direct measurements 

of H2O content to verify the vessel’s level of saturation. 

(5) If a sample dryer is not used in this verification test, use good engineering judgment to 

prevent condensation in the transfer lines, fittings, or valves from the point where xH2O is 

measured to the analyzer. We recommend that you design your system so that the wall 

temperatures in the transfer lines, fittings, and valves from the point where xH2O is measured to 

the analyzer are at least 5 oC above the local sample gas dewpoint. 

(6) Allow time for the analyzer response to stabilize. Stabilization time may include time to 

purge the transfer line and to account for analyzer response. 

(7) While the analyzer measures the sample’s concentration, record its output for 30 seconds. 

Calculate the arithmetic mean of this data. 

(8) The analyzer meets the interference verification if the result of paragraph (d)(7) of this 

section meets the tolerance in paragraph (c) of this section. 

(9) You may also run interference procedures for CO2 and H2O separately. If the CO2 and H2O 

levels used are higher than the maximum levels expected during testing, you may scale down 

each observed interference value by multiplying the observed interference by the ratio of the 

maximum expected concentration value to the actual value used during this procedure. You may 

run separate interference concentrations of H2O (down to 0.025 mol/mol H2O content) that are 

lower than the maximum levels expected during testing, but you must scale up the observed H2O 

interference by multiplying the observed interference by the ratio of the maximum expected H2O 

concentration value to the actual value used during this procedure. The sum of the two scaled 

interference values must meet the tolerance in paragraph (c) of this section. 

(e) Exceptions. The following exceptions apply: 

(1) You may omit this verification if you can show by engineering analysis that for your CO 

sampling system and your emission-calculation procedures, the combined CO2 and H2O 

interference for your CO NDIR analyzer always affects your brake-specific CO emission results 

within 0.5 % of the applicable CO standard. 

(2)You may use a CO NDIR analyzer that you determine does not meet this verification, as long 

as you try to correct the problem and the measurement deficiency does not adversely affect your 

ability to show that engines comply with all applicable emission standards. 

HYDROCARBON MEASUREMENTS 

§1065.360 FID optimization and verification. 

(a) Scope and frequency. For all FID analyzers, calibrate the FID upon initial installation. 

Repeat the calibration as needed using good engineering judgment. For a FID that measures 

THC, perform the following steps: 

(1) Optimize the response to various hydrocarbons after initial analyzer installation and after 

major maintenance as described in paragraph (c) of this section. 

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(2) Determine the methane (CH4) response factor after initial analyzer installation and after 

major maintenance as described in paragraph (d) of this section. 

(3) Verify the CH4 response within 185 days before testing as described in paragraph (e) of this 

section. 

(b) Calibration. Use good engineering judgment to develop a calibration procedure, such as one 

based on the FID-analyzer manufacturer’s instructions and recommended frequency for 

calibrating the FID. Alternately, you may remove system components for off-site calibration. 

For a FID that measures THC, calibrate using C3H8 calibration gases that meet the specifications 

of §1065.750. For a FID that measures CH4, calibrate using CH4 calibration gases that meet the 

specifications of §1065.750. We recommend FID analyzer zero and span gases that contain 

approximately the flow-weighted mean concentration of O2 expected during testing. If you use a 

FID to measure CH4 downstream of a nonmethane cutter, you may calibrate that FID using CH4

calibration gases with the cutter. Regardless of the calibration gas composition, calibrate on a 

carbon number basis of one (C1). For example, if you use a C3H8 span gas of concentration 200 

mol/mol, span the FID to respond with a value of 600 mol/mol. As another example, if you 

use a CH4 span gas with a concentration of 200 mol/mol, span the FID to respond with a value 

of 200 mol/mol. 

(c) THC FID response optimization. This procedure is only for FID analyzers that measure 

THC. Use good engineering judgment for initial instrument start-up and basic operating 

adjustment using FID fuel and zero air. Heated FIDs must be within their required operating 

temperature ranges. Optimize FID response at the most common analyzer range expected during 

emission testing. Optimization involves adjusting flows and pressures of FID fuel, burner air, 

and sample to minimize response variations to various hydrocarbon species in the exhaust. Use 

good engineering judgment to trade off peak FID response to propane calibration gases to 

achieve minimal response variations to different hydrocarbon species. For an example of trading 

off response to propane for relative responses to other hydrocarbon species, see SAE 770141 

(incorporated by reference in §1065.1010). Determine the optimum flow rates and/or pressures 

for FID fuel, burner air, and sample and record them for future reference. 

(d) THC FID CH4 response factor determination. This procedure is only for FID analyzers that 

measure THC. Since FID analyzers generally have a different response to CH4 versus C3H8, 

determine each THC-FID analyzer’s CH4 response factor, RFCH4[THC-FID], after FID optimization. 

Use the most recent RFCH4[THC-FID] measured according to this section in the calculations for HC 

determination described in §1065.660 to compensate for CH4 response. Determine RFCH4[THCFID] as follows, noting that you do not determine RFCH4[THC-FID] for FIDs that are calibrated and 

spanned using CH4 with a nonmethane cutter: 

(1) Select a C3H8 span gas concentration that you use to span your analyzers before emission 

testing. Use only span gases that meet the specifications of §1065.750. Record the C3H8

concentration of the gas. 

(2) Select a CH4 span gas concentration that you use to span your analyzers before emission 

testing. Use only span gases that meet the specifications of §1065.750. Record the CH4

concentration of the gas. 

(3) Start and operate the FID analyzer according to the manufacturer’s instructions. 

Deleted: methane (

Deleted: )

Deleted: methane (

Deleted: )

Deleted: THC 
(4) Confirm that the FID analyzer has been calibrated using C3H8. Calibrate on a carbon number 

basis of one (C1). For example, if you use a C3H8 span gas of concentration 200 mol/mol, span 

the FID to respond with a value of 600 mol/mol. 

(5) Zero the FID with a zero gas that you use for emission testing. 

(6) Span the FID with the C3H8 span gas that you selected under paragraph (d)(1) of this section. 

(7) Introduce at the sample port of the FID analyzer, the CH4 span gas that you selected under 

paragraph (d)(2) of this section. 

(8) Allow time for the analyzer response to stabilize. Stabilization time may include time to 

purge the analyzer and to account for its response. 

(9) While the analyzer measures the CH4 concentration, record 30 seconds of sampled data. 

Calculate the arithmetic mean of these values. (10) For analyzers with multiple ranges, you need 

to perform the procedure in this paragraph (d) only on a single range. 

(11) Divide the mean measured concentration by the recorded span concentration of the CH4

calibration gas. The result is the FID analyzer’s response factor for CH4, RFCH4[THC-FID]. 

(e) THC FID CH4 response verification. This procedure is only for FID analyzers that measure 

THC. If the value of RFCH4[THC-FID] from paragraph (d) of this section is within 5 % of its most 

recent previously determined value, the THC FID passes the CH4 response verification. For 

example, if the most recent previous value for RFCH4[THC-FID] was 1.05 and it changed by 0.05 to 

become 1.10 or it changed by -0.05 to become 1.00, either case would be acceptable because 

4.8 % is less than 5 %. Verify RFCH4[THC-FID] as follows: 

(1) First verify that the flow rates and/or pressures of FID fuel, burner air, and sample are each 

within 0.5 % of their most recent previously recorded values, as described in paragraph (c) of 

this section. You may adjust these flow rates as necessary. Then determine the RFCH4[THC-FID] as 

described in paragraph (d) of this section and verify that it is within the tolerance specified in this 

paragraph (e). 

(2) If RFCH4[THC-FID] is not within the tolerance specified in this paragraph (e), re-optimize the 

FID response as described in paragraph (c) of this section. 

(3) Determine a new RFCH4[THC-FID] as described in paragraph (d) of this section. Use this new 

value of RFCH4[THC-FID] in the calculations for HC determination, as described in §1065.660. 

§1065.362 Non-stoichiometric raw exhaust FID O2 interference verification. 

(a) Scope and frequency. If you use FID analyzers for raw exhaust measurements from engines 

that operate in a non-stoichiometric mode of combustion (e.g., compression-ignition, lean-burn), 

verify the amount of FID O2 interference upon initial installation and after major maintenance. 

(b) Measurement principles. Changes in O2 concentration in raw exhaust can affect FID 

response by changing FID flame temperature. Optimize FID fuel, burner air, and sample flow to 

meet this verification. Verify FID performance with the compensation algorithms for FID O2

interference that you have active during an emission test. 

(c) System requirements. Any FID analyzer used during testing must meet the FID O2

interference verification according to the procedure in this section. 

(d) Procedure. Determine FID O2 interference as follows, noting that you may use one or more 

gas dividers to create the reference gas concentrations that are required to perform this 

verification: 

Deleted: 10

Deleted: methane (

Deleted: )

Deleted: methane 
(1) Select three span reference gases that contain a C3H8 concentration that you use to span your 

analyzers before emission testing. Use only span gases that meet the specifications of 

§1065.750. You may use CH4 span reference gases for FIDs calibrated on CH4 with a 

nonmethane cutter. Select the three balance gas concentrations such that the concentrations of 

O2 and N2 represent the minimum, maximum, and average O2 concentrations expected during 

testing. The requirement for using the average O2 concentration can be removed if you choose to 

calibrate the FID with span gas balanced with the average expected oxygen concentration. 

(2) Confirm that the FID analyzer meets all the specifications of §1065.360. 

(3) Start and operate the FID analyzer as you would before an emission test. Regardless of the 

FID burner’s air source during testing, use zero air as the FID burner’s air source for this 

verification. 

(4) Zero the FID analyzer using the zero gas used during emission testing. 

(5) Span the FID analyzer using a span gas that you use during emission testing. 

(6) Check the zero response of the FID analyzer using the zero gas used during emission testing. 

If the mean zero response of 30 seconds of sampled data is within 0.5 % of the span reference 

value used in paragraph (d)(5) of this section, then proceed to the next step; otherwise restart the 

procedure at paragraph (d)(4) of this section. 

(7) Check the analyzer response using the span gas that has the minimum concentration of O2

expected during testing. Record the mean response of 30 seconds of stabilized sample data as 

xO2minHC. 

(8) Check the zero response of the FID analyzer using the zero gas used during emission testing. 

If the mean zero response of 30 seconds of stabilized sample data is within 0.5 % of the span 

reference value used in paragraph (d)(5) of this section, then proceed to the next step; otherwise 

restart the procedure at paragraph (d)(4) of this section. 

(9) Check the analyzer response using the span gas that has the average concentration of O2

expected during testing. Record the mean response of 30 seconds of stabilized sample data as 

xO2avgHC. 

(10) Check the zero response of the FID analyzer using the zero gas used during emission 

testing. If the mean zero response of 30 seconds of stabilized sample data is within ±0.5 % of the 

span reference value used in paragraph (d)(5) of this section, proceed to the next step; otherwise 

restart the procedure at paragraph (d)(4) of this section. 

(11) Check the analyzer response using the span gas that has the maximum concentration of O2

expected during testing. Record the mean response of 30 seconds of stabilized sample data as 

xO2maxHC. 

(12) Check the zero response of the FID analyzer using the zero gas used during emission 

testing. If the mean zero response of 30 seconds of stabilized sample data is within 0.5 % of 

the span reference value used in paragraph (d)(5) of this section, then proceed to the next step; 

otherwise restart the procedure at paragraph (d)(4) of this section. 

(13) Calculate the percent difference between xO2maxHC and its reference gas concentration. 

Calculate the percent difference between xO2avgHC and its reference gas concentration. Calculate 

the percent difference between xO2minHC and its reference gas concentration. Determine the 

maximum percent difference of the three. This is the O2 interference. 

(14) If the O2 interference is within 2 %, the FID passes the O2 interference verification; 

otherwise perform one or more of the following to address the deficiency: 
(i) Repeat the verification to determine if a mistake was made during the procedure. 

(ii) Select zero and span gases for emission testing that contain higher or lower O2 concentrations 

and repeat the verification. 

(iii) Adjust FID burner air, fuel, and sample flow rates. Note that if you adjust these flow rates 

on a THC FID to meet the O2 interference verification, you have reset RFCH4 for the next RFCH4

verification according to §1065.360. Repeat the O2 interference verification after adjustment and 

determine RFCH4. 

(iv) Repair or replace the FID and repeat the O2 interference verification. 

(v) Demonstrate that the deficiency does not adversely affect your ability to demonstrate 

compliance with the applicable emission standards. (15) For analyzers with multiple ranges, you 

need to perform the procedure in this paragraph (d) only on a single range. 

§1065.365 Nonmethane cutter penetration fractions. 

(a) Scope and frequency. If you use a FID analyzer and a nonmethane cutter (NMC) to measure 

methane (CH4), determine the nonmethane cutter’s penetration fractions of CH4, PFCH4, and 

ethane, PFC2H6. As detailed in this section, these penetration fractions may be determined as a 

combination of NMC penetration fractions and FID analyzer response factors, depending on 

your particular NMC and FID analyzer configuration. Perform this verification after installing 

the nonmethane cutter. Repeat this verification within 185 days of testing to verify that the 

catalytic activity of the cutter has not deteriorated. Note that because nonmethane cutters can 

deteriorate rapidly and without warning if they are operated outside of certain ranges of gas 

concentrations and outside of certain temperature ranges, good engineering judgment may dictate 

that you determine a nonmethane cutter’s penetration fractions more frequently. 

(b) Measurement principles. A nonmethane cutter is a heated catalyst that removes nonmethane 

hydrocarbons from an exhaust sample stream before the FID analyzer measures the remaining 

hydrocarbon concentration. An ideal nonmethane cutter would have a CH4 penetration fraction, 

PFCH4, of 1.000, and the penetration fraction for all other nonmethane hydrocarbons would be 

0.000, as represented by PFC2H6. The emission calculations in §1065.660 use the measured 

values from this verification to account for less than ideal NMC performance. 

(c) System requirements. We do not limit NMC penetration fractions to a certain range. 

However, we recommend that you optimize a nonmethane cutter by adjusting its temperature to 

achieve a PFCH4 >0.85 and a PFC2H6 <0.02, as determined by paragraphs (d), (e), or (f) of this 

section, as applicable. If we use a nonmethane cutter for testing, it will meet this 

recommendation. If adjusting NMC temperature does not result in achieving both of these 

specifications simultaneously, we recommend that you replace the catalyst material. Use the 

most recently determined penetration values from this section to calculate HC emissions 

according to §1065.660 and §1065.665 as applicable. 

(d) Procedure for a FID calibrated with the NMC. The method described in this paragraph (d) is 

recommended over the procedures specified in paragraphs (e) and (f) of this section. If your FID 

arrangement is such that a FID is always calibrated to measure CH4 with the NMC, then span 

that FID with the NMC using a CH4 span gas, set the product of that FID’s CH4 response factor 

and CH4 penetration fraction, RFPFCH4[NMC-FID], equal to 1.0 for all emission calculations, and 

determine its combined ethane (C2H6) response factor and penetration fraction, RFPFC2H6[NMCFID] as follows: 

Deleted: methane

Deleted: methane 
(1) Select CH4 and C2H6 analytical gas mixtures and ensure that both mixtures meet the 

specifications of §1065.750. Select a CH4 concentration that you would use for spanning the 

FID during emission testing and select a C2H6 concentration that is typical of the peak NMHC 

concentration expected at the hydrocarbon standard or equal to the THC analyzer’s span value. 

For CH4 analyzers with multiple ranges, perform this procedure on the highest range used for 

emission testing.

(2) Start, operate, and optimize the nonmethane cutter according to the manufacturer’s 

instructions, including any temperature optimization. 

(3) Confirm that the FID analyzer meets all the specifications of §1065.360. 

(4) Start and operate the FID analyzer according to the manufacturer’s instructions. 

(5) Zero and span the FID with the nonmethane cutter as you would during emission testing. 

Span the FID through the cutter by using CH4 span gas. 

(6) Introduce the C2H6 analytical gas mixture upstream of the nonmethane cutter. Use good 

engineering judgment to address the effect of hydrocarbon contamination if your point of 

introduction is vastly different from the point of zero/span gas introduction. 

(7) Allow time for the analyzer response to stabilize. Stabilization time may include time to 

purge the nonmethane cutter and to account for the analyzer’s response. 

(8) While the analyzer measures a stable concentration, record 30 seconds of sampled data. 

Calculate the arithmetic mean of these data points. 

(9) Divide the mean C2H6 concentration by the reference concentration of C2H6, converted to a 

C1 basis. The result is the C2H6 combined response factor and penetration fraction, 

RFPFC2H6[NMC-FID]. Use this combined response factor and penetration fraction and the product 

of the CH4 response factor and CH4 penetration fraction, RFPFCH4[NMC-FID], set to 1.0 in emission 

calculations according to §1065.660(b)(2)(i), §1065.660(c)(1)(i), or §1065.665, as applicable. 

(e) Procedure for a FID calibrated with propane, bypassing the NMC. If you use a single FID for 

THC and CH4 determination with an NMC that is calibrated with propane, C3H8, by bypassing 

the NMC, determine its penetration fractions, PFC2H6[NMC-FID] and PFCH4[NMC-FID], as follows: 

(1) Select CH4 and C2H6 analytical gas mixtures and ensure that both mixtures meet the 

specifications of §1065.750. Select a CH4 concentration that you would use for spanning the 

FID during emission testing and select a C2H6 concentration that is typical of the peak NMHC 

concentration expected at the hydrocarbon standard and the C2H6 concentration typical of the 

peak total hydrocarbon (THC) concentration expected at the hydrocarbon standard or equal to 

the THC analyzer’s span value. For CH4 analyzers with multiple ranges, perform this procedure 

on the highest range used for emission testing.

(2) Start and operate the nonmethane cutter according to the manufacturer’s instructions, 

including any temperature optimization. 

(3) Confirm that the FID analyzer meets all the specifications of §1065.360. 

(4) Start and operate the FID analyzer according to the manufacturer’s instructions. 

(5) Zero and span the FID as you would during emission testing. Span the FID by bypassing the 

cutter and by using C3H8 span gas. Note that you must span the FID on a C1 basis. For example, 

if your span gas has a propane reference value of 100 mol/mol, the correct FID response to that 

span gas is 300 mol/mol because there are three carbon atoms per C3H8 molecule. 
(6) Introduce the C2H6 analytical gas mixture upstream of the nonmethane cutter. Use good 

engineering judgment to address the effect of hydrocarbon contamination if your point of 

introduction is vastly different from the point of zero/span gas introduction. 

(7) Allow time for the analyzer response to stabilize. Stabilization time may include time to 

purge the nonmethane cutter and to account for the analyzer’s response. 

(8) While the analyzer measures a stable concentration, record 30 seconds of sampled data. 

Calculate the arithmetic mean of these data points. 

(9) Reroute the flow path to bypass the nonmethane cutter, introduce the C2H6 analytical gas 

mixture, and repeat the steps in paragraphs (e)(7) through (8) of this section. 

(10) Divide the mean C2H6 concentration measured through the nonmethane cutter by the mean 

C2H6 concentration measured after bypassing the nonmethane cutter. The result is the C2H6

penetration fraction, PFC2H6[NMC-FID]. Use this penetration fraction according to 

§1065.660(b)(2)(ii), §1065.660(c)(1)(ii), or §1065.665, as applicable. 

(11) Repeat the steps in paragraphs (e)(6) through (10) of this section, but with the CH4

analytical gas mixture instead of C2H6. The result will be the CH4 penetration fraction, 

PFCH4[NMC-FID]. Use this penetration fraction according to §1065.660(b)(2)(ii) or §1065.665, as 

applicable. 

(f) Procedure for a FID calibrated with CH4, bypassing the NMC. If you use a FID with an 

NMC that is calibrated with CH4, by bypassing the NMC, determine its combined ethane (C2H6) 

response factor and penetration fraction, RFPFC2H6[NMC-FID] , as well as its CH4 penetration 

fraction, PFCH4[NMC-FID], as follows: 

(1) Select CH4 and C2H6 analytical gas mixtures and ensure that both mixtures meet the 

specifications of §1065.750. Select a CH4 concentration that you would use for spanning the 

FID during emission testing and select a C2H6 concentration that is typical of the peak NMHC 

concentration expected at the hydrocarbon standard or equal to the THC analyzer’s span value. 

For CH4 analyzers with multiple ranges, perform this procedure on the highest range used for 

emission testing.

(2) Start and operate the nonmethane cutter according to the manufacturer’s instructions, 

including any temperature optimization. 

(3) Confirm that the FID analyzer meets all the specifications of §1065.360. 

(4) Start and operate the FID analyzer according to the manufacturer’s instructions. 

(5) Zero and span the FID as you would during emission testing. Span the FID by bypassing the 

cutter and by using CH4 span gas. 

(6) Introduce the C2H6 analytical gas mixture upstream of the nonmethane cutter. Use good 

engineering judgment to address the effect of hydrocarbon contamination if your point of 

introduction is vastly different from the point of zero/span gas introduction. 

(7) Allow time for the analyzer response to stabilize. Stabilization time may include time to 

purge the nonmethane cutter and to account for the analyzer’s response. 

(8) While the analyzer measures a stable concentration, record 30 seconds of sampled data. 

Calculate the arithmetic mean of these data points. 

(9) Divide the mean C2H6 concentration by the reference concentration of C2H6, converted to a 

C1 basis. The result is the C2H6 combined response factor and penetration fraction, 

RFPFC2H6[NMC-FID]. Use this combined response factor and penetration fraction according to 

§1065.660(b)(2)(iii), §1065.660(c)(1)(iii), or §1065.665, as applicable. 

Deleted: methane

Deleted: methane, 
(10) Introduce the CH4 analytical gas mixture upstream of the nonmethane cutter. Use good 

engineering judgment to address the effect of hydrocarbon contamination if your point of 

introduction is vastly different from the point of zero/span gas introduction. 

(11) Allow time for the analyzer response to stabilize. Stabilization time may include time to 

purge the nonmethane cutter and to account for the analyzer’s response. 

(12) While the analyzer measures a stable concentration, record 30 seconds of sampled data. 

Calculate the arithmetic mean of these data points. 

(13) Reroute the flow path to bypass the nonmethane cutter, introduce the CH4 analytical gas 

mixture, and repeat the steps in paragraphs (e)(11) and (12) of this section. 

(14) Divide the mean CH4 concentration measured through the nonmethane cutter by the mean 

CH4 concentration measured after bypassing the nonmethane cutter. The result is the CH4

penetration fraction, PFCH4[NMC-FID]. Use this penetration fraction according to 

§1065.660(b)(2)(iii), §1065.660(c)(1)(iii), or §1065.665, as applicable.

§1065.369 H2O, CO, and CO2 interference verification for photoacoustic alcohol analyzers.

(a) Scope and frequency. If you measure ethanol or methanol using a photoacoustic analyzer, 

verify the amount of H2O, CO, and CO2 interference after initial analyzer installation and after 

major maintenance.

(b) Measurement principles. H2O, CO, and CO2 can positively interfere with a photoacoustic

analyzer by causing a response similar to ethanol or methanol. If the photoacoustic analyzer uses 

compensation algorithms that utilize measurements of other gases to meet this interference 

verification, simultaneously conduct these other measurements to test the compensation 

algorithms during the analyzer interference verification.

(c) System requirements. Photoacoustic analyzers must have combined interference that is 

within (0.0 ± 0.5) μmol/mol. We strongly recommend a lower interference that is within (0.0 ± 

0.25) μmol/mol.

(d) Procedure. Perform the interference verification by following the procedure in §1065.375(d), 

comparing the results to paragraph (c) of this section.

NOx AND N2O MEASUREMENTS 

§1065.370 CLD CO2 and H2O quench verification. 

(a) Scope and frequency. If you use a CLD analyzer to measure NOx, verify the amount of H2O 

and CO2 quench after installing the CLD analyzer and after major maintenance. 

(b) Measurement principles. H2O and CO2 can negatively interfere with a CLD’s NOx response 

by collisional quenching, which inhibits the chemiluminescent reaction that a CLD utilizes to 

detect NOx. This procedure and the calculations in §1065.675 determine quench and scale the 

quench results to the maximum mole fraction of H2O and the maximum CO2 concentration 

expected during emission testing. If the CLD analyzer uses quench compensation algorithms 

that utilize H2O and/or CO2 measurement instruments, evaluate quench with these instruments 

active and evaluate quench with the compensation algorithms applied. 

(c) System requirements. A CLD analyzer must have a combined H2O and CO2 quench of 2 % 

or less, though we strongly recommend a quench of 1 % or less. Combined quench is the sum 
of the CO2 quench determined as described in paragraph (d) of this section, plus the H2O quench 

determined in paragraph (e) of this section. 

(d) CO2 quench verification procedure. Use the following method to determine CO2 quench by 

using a gas divider that blends binary span gases with zero gas as the diluent and meets the 

specifications in §1065.248, or use good engineering judgment to develop a different protocol: 

(1) Use PTFE or stainless steel tubing to make necessary connections. 

(2) Configure the gas divider such that nearly equal amounts of the span and diluent gases are 

blended with each other. 

(3) If the CLD analyzer has an operating mode in which it detects NO-only, as opposed to total 

NOx, operate the CLD analyzer in the NO-only operating mode. 

(4) Use a CO2 span gas that meets the specifications of §1065.750 and a concentration that is 

approximately twice the maximum CO2 concentration expected during emission testing. 

(5) Use an NO span gas that meets the specifications of §1065.750 and a concentration that is 

approximately twice the maximum NO concentration expected during emission testing. 

(6) Zero and span the CLD analyzer. Span the CLD analyzer with the NO span gas from 

paragraph (d)(5) of this section through the gas divider. Connect the NO span gas to the span 

port of the gas divider; connect a zero gas to the diluent port of the gas divider; use the same 

nominal blend ratio selected in paragraph (d)(2) of this section; and use the gas divider’s output 

concentration of NO to span the CLD analyzer. Apply gas property corrections as necessary to 

ensure accurate gas division. 

(7) Connect the CO2 span gas to the span port of the gas divider. 

(8) Connect the NO span gas to the diluent port of the gas divider. 

(9) While flowing NO and CO2 through the gas divider, stabilize the output of the gas divider. 

Determine the CO2 concentration from the gas divider output, applying gas property correction 

as necessary to ensure accurate gas division. Record this concentration, xCO2act, and use it in the 

quench verification calculations in §1065.675. Alternatively, you may use a simple gas blending 

device and use an NDIR to determine this CO2 concentration. If you use an NDIR, it must meet 

the requirements of this part for laboratory testing and you must span it with the CO2 span gas 

from paragraph (d)(4) of this section. 

(10) Measure the NO concentration downstream of the gas divider with the CLD analyzer. 

Allow time for the analyzer response to stabilize. Stabilization time may include time to purge 

the transfer line and to account for analyzer response. While the analyzer measures the sample’s 

concentration, record the analyzer’s output for 30 seconds. Calculate the arithmetic mean 

concentration from these data, xNOmeas. Record xNOmeas, and use it in the quench verification 

calculations in §1065.675. 

(11) Calculate the actual NO concentration at the gas divider’s outlet, xNOact, based on the span 

gas concentrations and xCO2act according to Equation 1065.675-2. Use the calculated value in the 

quench verification calculations in Equation 1065.675-1. 

(12) Use the values recorded according to this paragraph (d) and paragraph (e) of this section to 

calculate quench as described in §1065.675. 

(e) H2O quench verification procedure. Use the following method to determine H2O quench, or 

use good engineering judgment to develop a different protocol: 

(1) Use PTFE or stainless steel tubing to make necessary connections. 
(2) If the CLD analyzer has an operating mode in which it detects NO-only, as opposed to total 

NOx, operate the CLD analyzer in the NO-only operating mode. 

(3) Use an NO span gas that meets the specifications of §1065.750 and a concentration that is 

near the maximum concentration expected during emission testing. 

(4) Zero and span the CLD analyzer. Span the CLD analyzer with the NO span gas from 

paragraph (e)(3) of this section, record the span gas concentration as xNOdry, and use it in the 

quench verification calculations in §1065.675. 

(5) Humidify the NO span gas by bubbling it through distilled H2O in a sealed vessel. If the 

humidified NO span gas sample does not pass through a sample dryer for this verification test, 

control the vessel temperature to generate an H2O level approximately equal to the maximum 

mole fraction of H2O expected during emission testing. If the humidified NO span gas sample 

does not pass through a sample dryer, the quench verification calculations in §1065.675 scale the 

measured H2O quench to the highest mole fraction of H2O expected during emission testing. If 

the humidified NO span gas sample passes through a dryer for this verification test, control the 

vessel temperature to generate an H2O level at least as high as the level determined in 

§1065.145(e)(2). For this case, the quench verification calculations in §1065.675 do not scale 

the measured H2O quench. 

(6) Introduce the humidified NO test gas into the sample system. You may introduce it upstream 

or downstream of any sample dryer that is used during emission testing. Note that the sample 

dryer must meet the sample dryer verification check in §1065.342.

(7) Measure the mole fraction of H2O in the humidified NO span gas downstream of the sample 

dryer, xH2Omeas. We recommend that you measure xH2Omeas as close as possible to the CLD 

analyzer inlet. You may calculate xH2Omeas from measurements of dewpoint, Tdew, and absolute 

pressure, ptotal. 

(8) Use good engineering judgment to prevent condensation in the transfer lines, fittings, or 

valves from the point where xH2Omeas is measured to the analyzer. We recommend that you 

design your system so the wall temperatures in the transfer lines, fittings, and valves from the 

point where xH2Omeas is measured to the analyzer are at least 5 oC above the local sample gas 

dewpoint. 

(9) Measure the humidified NO span gas concentration with the CLD analyzer. Allow time for 

the analyzer response to stabilize. Stabilization time may include time to purge the transfer line 

and to account for analyzer response. While the analyzer measures the sample’s concentration, 

record the analyzer’s output for 30 seconds. Calculate the arithmetic mean of these data, xNOwet. 

Record xNOwet and use it in the quench verification calculations in §1065.675. 

(f) Corrective action. If the sum of the H2O quench plus the CO2 quench is less than -2 % or 

greater than +2 %, take corrective action by repairing or replacing the analyzer. Before running 

emission tests, verify that the corrective action successfully restored the analyzer to proper 

functioning. 

(g) Exceptions. The following exceptions apply: 

(1) You may omit this verification if you can show by engineering analysis that for your NOx

sampling system and your emission calculation procedures, the combined CO2 and H2O 

interference for your NOx CLD analyzer always affects your brake-specific NOx emission results 

within no more than 1 % of the applicable NOx standard. If you certify to a combined emission 

standard (such as a NOx + NMHC standard), scale your NOx results to the combined standard 

Deleted: water
based on the measured results (after incorporating deterioration factors, if applicable). For 

example, if your final NOx + NMHC value is half of the emission standard, double the NOx

result to estimate the level of NOx emissions corresponding to the applicable standard. 

(2)You may use a NOx CLD analyzer that you determine does not meet this verification, as long 

as you try to correct the problem and the measurement deficiency does not adversely affect your 

ability to show that engines comply with all applicable emission standards. 

§1065.372 NDUV analyzer HC and H2O interference verification. 

(a) Scope and frequency. If you measure NOx using an NDUV analyzer, verify the amount of 

H2O and hydrocarbon interference after initial analyzer installation and after major maintenance. 

(b) Measurement principles. Hydrocarbons and H2O can positively interfere with an NDUV 

analyzer by causing a response similar to NOx. If the NDUV analyzer uses compensation 

algorithms that utilize measurements of other gases to meet this interference verification, 

simultaneously conduct such measurements to test the algorithms during the analyzer 

interference verification. 

(c) System requirements. A NOx NDUV analyzer must have combined H2O and HC interference 

within 2 % of the flow-weighted mean concentration of NOx expected at the standard, though 

we strongly recommend keeping interference within 1 %. 

(d) Procedure. Perform the interference verification as follows: 

(1) Start, operate, zero, and span the NOx NDUV analyzer according to the instrument 

manufacturer’s instructions. 

(2) We recommend that you extract engine exhaust to perform this verification. Use a CLD that 

meets the specifications of subpart C of this part to quantify NOx in the exhaust. Use the CLD 

response as the reference value. Also measure HC in the exhaust with a FID analyzer that meets 

the specifications of subpart C of this part. Use the FID response as the reference hydrocarbon 

value. 

(3) Upstream of any sample dryer, if one is used during testing, introduce the engine exhaust to 

the NDUV analyzer. 

(4) Allow time for the analyzer response to stabilize. Stabilization time may include time to 

purge the transfer line and to account for analyzer response. 

(5) While all analyzers measure the sample’s concentration, record 30 seconds of sampled data, 

and calculate the arithmetic means for the three analyzers. 

(6) Subtract the CLD mean from the NDUV mean. 

(7) Multiply this difference by the ratio of the flow-weighted mean HC concentration expected at 

the standard to the HC concentration measured during the verification. The analyzer meets the 

interference verification of this section if this result is within 2 % of the NOx concentration 

expected at the standard. 

(e) Exceptions. The following exceptions apply: 

(1) You may omit this verification if you can show by engineering analysis that for your NOx

sampling system and your emission calculation procedures, the combined HC and H2O 

interference for your NOx NDUV analyzer always affects your brake-specific NOx emission 

results by less than 0.5 % of the applicable NOx standard. 
(2)You may use a NOx NDUV analyzer that you determine does not meet this verification, as 

long as you try to correct the problem and the measurement deficiency does not adversely affect 

your ability to show that engines comply with all applicable emission standards. 

§1065.375 Interference verification for N2O analyzers. 

(a) Scope and frequency. See §1065.275 to determine whether you need to verify the amount of 

interference after initial analyzer installation and after major maintenance. 

(b) Measurement principles. Interference gasses can positively interfere with certain analyzers 

by causing a response similar to N2O. If the analyzer uses compensation algorithms that utilize 

measurements of other gases to meet this interference verification, simultaneously conduct these 

other measurements to test the compensation algorithms during the analyzer interference 

verification. 

(c) System requirements. Analyzers must have combined interference that is within (0.0 ± 1.0) 

μmol/mol. We strongly recommend a lower interference that is within (0.0 ± 0.5) μmol/mol. 

(d) Procedure. Perform the interference verification as follows: 

(1) Start, operate, zero, and span the N2O analyzer as you would before an emission test. If the 

sample is passed through a dryer during emission testing, you may run this verification test with 

the dryer if it meets the requirements of §1065.342. Operate the dryer at the same conditions as 

you will for an emission test. You may also run this verification test without the sample dryer. 

(2) Create a humidified test gas by bubbling a multi component span gas that incorporates the 

target interference species and meets the specifications in §1065.750 through distilled H2O in a 

sealed vessel. If the sample is not passed through a dryer during emission testing, control the 

vessel temperature to generate an H2O level at least as high as the maximum expected during 

emission testing. If the sample is passed through a dryer during emission testing, control the 

vessel temperature to generate an H2O level at least as high as the level determined in 

§1065.145(e)(2) for that dryer. Use interference span gas concentrations that are at least as high 

as the maximum expected during testing. 

(3) Introduce the humidified interference test gas into the sample system. You may introduce it 

downstream of any sample dryer, if one is used during testing. 

(4) If the sample is not passed through a dryer during this verification test, measure the H2O

mole fraction, xH2O, of the humidified interference test gas as close as possible to the inlet of the 

analyzer. For example, measure dewpoint, Tdew, and absolute pressure, ptotal, to calculate xH2O. 

Verify that the H2O content meets the requirement in paragraph (d)(2) of this section. If the 

sample is passed through a dryer during this verification test, you must verify that the H2O

content of the humidified test gas downstream of the vessel meets the requirement in paragraph 

(d)(2) of this section based on either direct measurement of the H2O content (e.g., dewpoint and 

pressure) or an estimate based on the vessel pressure and temperature. Use good engineering 

judgment to estimate the H2O content. For example, you may use previous direct measurements 

of H2O content to verify the vessel’s level of saturation. 

(5) If a sample dryer is not used in this verification test, use good engineering judgment to 

prevent condensation in the transfer lines, fittings, or valves from the point where xH2O is 

measured to the analyzer. We recommend that you design your system so that the wall 

temperatures in the transfer lines, fittings, and valves from the point where xH2O is measured to 

the analyzer are at least 5 oC above the local sample gas dewpoint. 

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(6) Allow time for the analyzer response to stabilize. Stabilization time may include time to 

purge the transfer line and to account for analyzer response. 

(7) While the analyzer measures the sample’s concentration, record its output for 30 seconds. 

Calculate the arithmetic mean of this data. When performed with all the gases simultaneously, 

this is the combined interference.

(8) The analyzer meets the interference verification if the result of paragraph (d)(7) of this 

section meets the tolerance in paragraph (c) of this section. 

(9) You may also run interference procedures separately for individual interference gases. If the 

interference gas levels used are higher than the maximum levels expected during testing, you 

may scale down each observed interference value (the arithmetic mean of 30 second data 

described in paragraph (d)(7) of this section) by multiplying the observed interference by the 

ratio of the maximum expected concentration value to the actual value used during this 

procedure. You may run separate interference concentrations of H2O (down to 0.025 mol/mol 

H2O content) that are lower than the maximum levels expected during testing, but you must scale 

up the observed H2O interference by multiplying the observed interference by the ratio of the 

maximum expected H2O concentration value to the actual value used during this procedure. The 

sum of the scaled interference values must meet the tolerance for combined interference as

specified in paragraph (c) of this section. 

§1065.376 Chiller NO2 penetration. 

(a) Scope and frequency. If you use a chiller to dry a sample upstream of a NOx measurement 

instrument, but you don’t use an NO2-to-NO converter upstream of the chiller, you must perform 

this verification for chiller NO2 penetration. Perform this verification after initial installation and 

after major maintenance. 

(b) Measurement principles. A chiller removes H2O, which can otherwise interfere with a NOx

measurement. However, liquid H2O remaining in an improperly designed chiller can remove 

NO2 from the sample. If a chiller is used without an NO2-to-NO converter upstream, it could 

remove NO2 from the sample prior NOx measurement. 

(c) System requirements. A chiller must allow for measuring at least 95 % of the total NO2 at the 

maximum expected concentration of NO2. 

(d) Procedure. Use the following procedure to verify chiller performance: 

(1) Instrument setup. Follow the analyzer and chiller manufacturers’ start-up and operating 

instructions. Adjust the analyzer and chiller as needed to optimize performance. 

(2) Equipment setup and data collection. (i) Zero and span the total NOx gas analyzer(s) as you 

would before emission testing. 

(ii) Select an NO2 calibration gas, balance gas of dry air, that has an NO2 concentration within ±5 

% of the maximum NO2 concentration expected during testing. 

(iii) Overflow this calibration gas at the gas sampling system’s probe or overflow fitting. Allow 

for stabilization of the total NOx response, accounting only for transport delays and instrument 

response. 

(iv) Calculate the mean of 30 seconds of recorded total NOx data and record this value as xNOxref. 

(v) Stop flowing the NO2 calibration gas. 

(vi) Next saturate the sampling system by overflowing a dewpoint generator’s output, set at a 

dewpoint of 50 C, to the gas sampling system’s probe or overflow fitting. Sample the dewpoint 

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generator’s output through the sampling system and chiller for at least 10 minutes until the 

chiller is expected to be removing a constant rate of H2O. 

(vii) Immediately switch back to overflowing the NO2 calibration gas used to establish xNOxref. 

Allow for stabilization of the total NOx response, accounting only for transport delays and 

instrument response. Calculate the mean of 30 seconds of recorded total NOx data and record 

this value as xNOxmeas. 

(viii) Correct xNOxmeas to xNOxdry based upon the residual H2O vapor that passed through the 

chiller at the chiller’s outlet temperature and pressure. 

(3) Performance evaluation. If xNOxdry is less than 95 % of xNOxref, repair or replace the chiller. 

(e) Exceptions. The following exceptions apply: 

(1) You may omit this verification if you can show by engineering analysis that for your NOx

sampling system and your emission calculations procedures, the chiller always affects your 

brake-specific NOx emission results by less than 0.5 % of the applicable NOx standard. 

(2)You may use a chiller that you determine does not meet this verification, as long as you try to 

correct the problem and the measurement deficiency does not adversely affect your ability to 

show that engines comply with all applicable emission standards. 

§1065.378 NO2-to-NO converter conversion verification. 

(a) Scope and frequency. If you use an analyzer that measures only NO to determine NOx, you 

must use an NO2-to-NO converter upstream of the analyzer. Perform this verification after 

installing the converter, after major maintenance and within 35 days before an emission test. This 

verification must be repeated at this frequency to verify that the catalytic activity of the NO2-toNO converter has not deteriorated. 

(b) Measurement principles. An NO2-to-NO converter allows an analyzer that measures only 

NO to determine total NOx by converting the NO2 in exhaust to NO. 

(c) System requirements. An NO2-to-NO converter must allow for measuring at least 95 % of 

the total NO2 at the maximum expected concentration of NO2. 

(d) Procedure. Use the following procedure to verify the performance of a NO2-to-NO 

converter: 

(1) Instrument setup. Follow the analyzer and NO2-to-NO converter manufacturers’ start-up and 

operating instructions. Adjust the analyzer and converter as needed to optimize performance. 

(2) Equipment setup. Connect an ozonator’s inlet to a zero-air or oxygen source and connect its 

outlet to one port of a three-way tee fitting. Connect an NO span gas to another port, and 

connect the NO2-to-NO converter inlet to the last port. 

(3) Adjustments and data collection. Perform this check as follows: 

(i) Set ozonator air off, turn ozonator power off, and set the analyzer to NO mode. Allow for 

stabilization, accounting only for transport delays and instrument response. 

(ii) Use an NO concentration that is representative of the peak total NOx concentration expected 

during testing. The NO2 content of the gas mixture shall be less than 5 % of the NO 

concentration. Record the concentration of NO by calculating the mean of 30 seconds of sampled 

data from the analyzer and record this value as xNOref. 

(iii) Turn on the ozonator O2 supply and adjust the O2 flow rate so the NO indicated by the 

analyzer is about 10 percent less than xNOref. Record the concentration of NO by calculating the 

mean of 30 seconds of sampled data from the analyzer and record this value as xNO+O2mix. 

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(iv) Switch the ozonator on and adjust the ozone generation rate so the NO measured by the 

analyzer is 20 percent of xNOref or a value which would simulate the maximum concentration of 

NO2 expected during testing, while maintaining at least 10 percent unreacted NO. This ensures 

that the ozonator is generating NO2 at the maximum concentration expected during testing. 

Record the concentration of NO by calculating the mean of 30 seconds of sampled data from the 

analyzer and record this value as xNOmeas.

(v) Switch the NOx analyzer to NOx mode and measure total NOx. Record the concentration of 

NOx by calculating the mean of 30 seconds of sampled data from the analyzer and record this 

value as xNOxmeas. 

(vi) Switch off the ozonator but maintain gas flow through the system. The NOx analyzer will 

indicate the NOx in the NO + O2 mixture. Record the concentration of NOx by calculating the 

mean of 30 seconds of sampled data from the analyzer and record this value as xNOx+O2mix. 

(vii) Turn off the ozonator O2 supply. The NOx analyzer will indicate the NOx in the original 

NO-in-N2 mixture. Record the concentration of NOx by calculating the mean of 30 seconds of 

sampled data from the analyzer and record this value as xNOxref. This value should be no more 

than 5 percent above the xNOref value. 

(4) Performance evaluation. Calculate the efficiency of the NOx converter by substituting the 

concentrations obtained into the following equation: 

NOxmeas NOx+O2mix

NO+O2mix NOmeas

1 100 % x x efficiency x x

         

(5) If the result is less than 95 %, repair or replace the NO2-to-NO converter. 

(e) Exceptions. The following exceptions apply: 

(1) You may omit this verification if you can show by engineering analysis that for your NOx

sampling system and your emission calculations procedures, the converter always affects your 

brake-specific NOx emission results by less than 0.5 % of the applicable NOx standard. 

(2)You may use a converter that you determine does not meet this verification, as long as you try 

to correct the problem and the measurement deficiency does not adversely affect your ability to 

show that engines comply with all applicable emission standards. 

PM MEASUREMENTS 

§1065.390 PM balance verifications and weighing process verification. 

(a) Scope and frequency. This section describes three verifications. 

(1) Independent verification of PM balance performance within 370 days before weighing any 

filter. 

(2) Zero and span the balance within 12 h before weighing any filter. 

(3) Verify that the mass determination of reference filters before and after a filter weighing 

session are less than a specified tolerance. 

(b) Independent verification. Have the balance manufacturer (or a representative approved by the 

balance manufacturer) verify the balance performance within 370 days of testing. 

(c) Zeroing and spanning. You must verify balance performance by zeroing and spanning it with 

at least one calibration weight, and any weights you use must that meet the specifications in 

§1065.790 to perform this verification. 
(1) Use a manual procedure in which you zero the balance and span the balance with at least one 

calibration weight. If you normally use mean values by repeating the weighing process to 

improve the accuracy and precision of PM measurements, use the same process to verify balance 

performance. 

(2) You may use an automated procedure to verify balance performance. For example many 

balances have internal calibration weights that are used automatically to verify balance 

performance. 

(d) Reference sample weighing. Verify all mass readings during a weighing session by weighing 

reference PM sample media (e.g. filters) before and after a weighing session. A weighing session 

may be as short as desired, but no longer than 80 hours, and may include both pre-test and posttest mass readings. We recommend that weighing sessions be eight hours or less. Successive 

mass determinations of each reference PM sample media (e.g., filter) must return the same value 

within 10 g or 10 % of the net PM mass expected at the standard (if known), whichever is 

higher. If successive reference PM sample media (e.g. filter) weighing events fail this criterion, 

invalidate all individual test media (e.g., filter) mass readings occurring between the successive 

reference media (e.g., filter) mass determinations. You may reweigh these media (e.g. filter) in 

another weighing session. If you invalidate a pre-test media (e.g. filter) mass determination, that 

test interval is void. Perform this verification as follows: 

(1) Keep at least two samples of unused PM sample media (e.g., filters) in the PM-stabilization 

environment. Use these as references. If you collect PM with filters, select unused filters of the 

same material and size for use as references. You may periodically replace references, using 

good engineering judgment. 

(2) Stabilize references in the PM stabilization environment. Consider references stabilized if 

they have been in the PM-stabilization environment for a minimum of 30 min, and the PMstabilization environment has been within the specifications of §1065.190(d) for at least the 

preceding 60 min. 

(3) Exercise the balance several times with a reference sample. We recommend weighing ten 

samples without recording the values. 

(4) Zero and span the balance. Using good engineering judgment, place a test mass such as a 

calibration weight on the balance, then remove it. After spanning, confirm that the balance 

returns to a zero reading within the normal stabilization time. 

(5) Weigh each of the reference media (e.g. filters) and record their masses. We recommend 

using substitution weighing as described in §1065.590(j). If you normally use mean values by 

repeating the weighing process to improve the accuracy and precision of the reference media 

(e.g. filter) mass, you must use mean values of sample media (e.g. filter) masses. 

(6) Record the balance environment dewpoint, ambient temperature, and atmospheric pressure. 

(7) Use the recorded ambient conditions to correct results for buoyancy as described in 

§1065.690. Record the buoyancy-corrected mass of each of the references. 

(8) Subtract each reference media’s (e.g. filter’s) buoyancy-corrected reference mass from its 

previously measured and recorded buoyancy-corrected mass. 

(9) If any of the reference filters’ observed mass changes by more than that allowed under this 

paragraph, you must invalidate all PM mass determinations made since the last successful 

reference media (e.g. filter) mass validation. You may discard reference PM media (e.g. filters) 

if only one of the filter’s mass changes by more than the allowable amount and you can 
positively identify a special cause for that filter’s mass change that would not have affected other 

in-process filters. Thus, the validation can be considered a success. In this case, you do not have 

to include the contaminated reference media when determining compliance with paragraph 

(d)(10) of this section, but the affected reference filter must be immediately discarded and 

replaced prior to the next weighing session. 

(10) If any of the reference masses change by more than that allowed under this paragraph (d), 

invalidate all PM results that were determined between the two times that the reference masses 

were determined. If you discarded reference PM sample media according to paragraph (d)(9) of 

this section, you must still have at least one reference mass difference that meets the criteria in 

this paragraph (d). Otherwise, you must invalidate all PM results that were determined between 

the two times that the reference media (e.g. filters) masses were determined. 

§1065.395 Inertial PM balance verifications. 

This section describes how to verify the performance of an inertial PM balance. 

(a) Independent verification. Have the balance manufacturer (or a representative approved by 

the balance manufacturer) verify the inertial balance performance within 370 days before testing. 

(b) Other verifications. Perform other verifications using good engineering judgment and 

instrument manufacturer recommendations.
Subpart E—Engine Selection, Preparation, and Maintenance

§1065.401 Test engine selection. 

While all engine configurations within a certified engine family must comply with the applicable 

standards in the standard-setting part, you need not test each configuration for certification. 

(a) Select an engine configuration within the engine family for testing, as follows: 

(1) Test the engine that we specify, whether we issue general guidance or give you specific 

instructions. 

(2) If we do not tell you which engine to test, follow any instructions in the standard-setting part. 

(3) If we do not tell you which engine to test and the standard-setting part does not include 

specifications for selecting test engines, use good engineering judgment to select the engine 

configuration within the engine family that is most likely to exceed an emission standard. 

(b) In the absence of other information, the following characteristics are appropriate to consider 

when selecting the engine to test: 

(1) Maximum fueling rates. 

(2) Maximum loads. 

(3) Maximum in-use speeds. 

(4) Highest sales volume. 

(c) For our testing, we may select any engine configuration within the engine family. 

§1065.405 Test engine preparation and maintenance. 

This part 1065 describes how to test engines for a variety of purposes, including certification 

testing, production-line testing, and in-use testing. Depending on which type of testing is being 

conducted, different preparation and maintenance requirements apply for the test engine. 

(a) If you are testing an emission-data engine for certification, make sure it is built to represent 

production engines, consistent with paragraph (f) of this section. This includes governors that 

you normally install on production engines. Production engines should also be tested with their 

installed governors. If you do not install governors on production engines, simulate a governor 

that is representative of a governor that others will install on your production engines. In certain 

circumstances, you may incorporate test cell components to simulate an in-use configuration, 

consistent with good engineering judgment. For example, §§1065.122 and 1065.125 allow the 

use of test cell components to represent engine cooling and intake air systems.

(b) Testing generally occurs only after the test engine has undergone a stabilization step (or inuse operation). If the engine has not already been stabilized, run the test engine, with all 

emission control systems operating, long enough to stabilize emission levels. Note that you must 

generally use the same stabilization procedures for emission-data engines for which you apply 

the same deterioration factors so low-hour emission-data engines are consistent with the lowhour engine used to develop the deterioration factor. 

(1) Unless otherwise specified in the standard-setting part, you may consider emission levels 

stable without measurement after 50 h of operation. If the engine needs less operation to 

stabilize emission levels, record your reasons and the methods for doing this, and give us these 

records if we ask for them. If the engine will be tested for certification as a low-hour engine, see 

the standard-setting part for limits on testing engines to establish low-hour emission levels. (2) 

You may stabilize emissions from a catalytic exhaust aftertreatment device by operating it on a 
different engine, consistent with good engineering judgment. Note that good engineering 

judgment requires that you consider both the purpose of the test and how your stabilization 

method will affect the development and application of deterioration factors. For example, this 

method of stabilization is generally not appropriate for production engines. We may also allow 

you to stabilize emissions from a catalytic exhaust aftertreatment device by operating it on an 

engine-exhaust simulator. (c) Record any maintenance, modifications, parts changes, diagnostic 

or emissions testing and document the need for each event. You must provide this information if 

we request it. 

(d) For accumulating operating hours on your test engines, select engine operation that represents 

normal in-use operation for the engine family. 

(e) If your engine will be used in a vehicle equipped with a canister for storing evaporative 

hydrocarbons for eventual combustion in the engine and the test sequence involves a cold-start or 

hot-start duty cycle, attach a canister to the engine before running an emission test. You may 

omit using an evaporative canister for any hot-stabilized duty cycles. You may request to omit 

using an evaporative canister during testing if you can show that it would not affect your ability 

to show compliance with the applicable emission standards. You may operate the engine 

without an installed canister for service accumulation. Prior to an emission test, use the 

following steps to attach a canister to your engine: 

(1) Use a canister and plumbing arrangement that represents the in-use configuration of the 

largest capacity canister in all expected applications. 

(2) Use a canister that is fully loaded with fuel vapors. 

(3) Connect the canister's purge port to the engine. 

(4) Plug the canister port that is normally connected to the fuel tank. 

(f) This paragraph (f) defines the components that are considered to be part of the engine for 

laboratory testing. (Note: see §1065.110 for provisions related to system boundaries with respect 

to work inputs and outputs.) 

(1) This paragraph (f)(1) describes certain criteria for considering a component to be part of the 

test engine. The criteria are intended to apply broadly, such that a component would generally 

be considered part of the engine in cases of uncertainty. An engine-related component meeting 

all the following criteria is considered to be part of the test engine for purposes of testing and for 

stabilizing emission levels, preconditioning, and measuring emission levels:

(i) The component directly affects the functioning of the engine, is related to the control of 

emissions, or transmits engine power. This would include engine cooling systems, engine 

controls, and transmissions.

(ii) The component is covered by the applicable certificate of conformity. For example, this 

criterion would typically exclude radiators not described in an application for certification.

(iii) The component is not part of the laboratory setup or used for other engines. 

(2) Although components meeting the criteria specified in paragraphs (f)(1)(i) or (ii) of this 

section, but not the criterion specified in paragraph (f)(1)(iii) of this section, are not considered 

to be part of the test engine, you must precondition these components along with the test engine.

§1065.410 Maintenance limits for stabilized test engines. 
(a) After you stabilize the test engine's emission levels, you may do maintenance as allowed by 

the standard-setting part. However, you may not do any maintenance based on emission 

measurements from the test engine (i.e., unscheduled maintenance). 

(b) For any critical emission-related maintenance–other than what we specifically allow in the 

standard-setting part–you must completely test an engine for emissions before and after doing 

any maintenance that might affect emissions, unless we waive this requirement. 

(c) Keep a record of the inspection and update your application to document any changes as a 

result of the inspection. You may use equipment, instruments, or engineering grade tools to 

identify bad engine components. Any equipment, instruments, or tools used for scheduled 

maintenance on emission data engines must be representative of what is planned to be available 

to dealerships and other service outlets. 

(d) If we determine that a part failure, system malfunction, or associated repairs have made the 

engine’s emission controls unrepresentative of production engines, you may no longer use it as 

an emission-data engine. Also, if your test engine has a major mechanical failure that requires 

you to take it apart, you may no longer use it as an emission-data engine. 

§1065.415 Durability demonstration. 

If the standard-setting part requires durability testing, you must accumulate service in a way that 

represents how you expect the engine to operate in use. You may accumulate service hours 

using an accelerated schedule, such as through continuous operation or by using duty cycles that 

are more aggressive than in-use operation, subject to any pre-approval requirements established 

in the applicable standard-setting part. 

(a) Maintenance. The following limits apply to the maintenance that we allow you to do on an 

emission-data engine: 

(1) You may perform scheduled maintenance that you recommend to operators, but only if it is 

consistent with the standard-setting part's restrictions. 

(2) You may perform additional maintenance only as specified in §1065.410 or allowed by the 

standard-setting part. 

(b) Emission measurements. Perform emission tests following the provisions of the standard 

setting part and this part, as applicable. Perform emission tests to determine deterioration factors 

consistent with good engineering judgment. Evenly space any tests between the first and last test 

points throughout the durability period, unless we approve otherwise.
Subpart F—Performing an Emission Test Over Specified Duty Cycles 

§1065.501 Overview. 

(a) Use the procedures detailed in this subpart to measure engine emissions over a specified duty 

cycle. Refer to subpart J of this part for field test procedures that describe how to measure 

emissions during in-use engine operation. This section describes how to: 

(1) Map your engine, if applicable, by recording specified speed and torque data, as measured 

from the engine’s primary output shaft. 

(2) Transform normalized duty cycles into reference duty cycles for your engine by using an 

engine map. 

(3) Prepare your engine, equipment, and measurement instruments for an emission test. 

(4) Perform pre-test procedures to verify proper operation of certain equipment and analyzers. 

(5) Record pre-test data. 

(6) Start or restart the engine and sampling systems. 

(7) Sample emissions throughout the duty cycle. 

(8) Record post-test data. 

(9) Perform post-test procedures to verify proper operation of certain equipment and analyzers. 

(10) Weigh PM samples.

(b) Unless we specify otherwise, you may control the regeneration timing of infrequently 

regenerated aftertreatment devices such as diesel particulate filters using good engineering 

judgment. You may control the regeneration timing using a sequence of engine operating 

conditions or you may initiate regeneration with an external regeneration switch or other

command. This provision would also allow you to ensure that a regeneration event does not 

occur during an emission test.

(c) An emission test generally consists of measuring emissions and other parameters while an 

engine follows one or more duty cycles that are specified in the standard-setting part. There are 

two general types of duty cycles: 

(1) Transient cycles. Transient duty cycles are typically specified in the standard-setting part as 

a second-by-second sequence of speed commands and normalized torque (or power) commands. 

Operate an engine over a transient cycle such that the speed and torque of the engine’s primary 

output shaft follows the target values. Proportionally sample emissions and other parameters and 

use the calculations in subpart G of this part to calculate emissions. Start a transient test 

according to the standard-setting part, as follows: 

(i) A cold-start transient cycle where you start to measure emissions just before starting an 

engine that has not been warmed up. 

(ii) A hot-start transient cycle where you start to measure emissions just before starting a 

warmed-up engine. 

(iii) A hot running transient cycle where you start to measure emissions after an engine is started, 

warmed up, and running. 

(2) Steady-state cycles. Steady-state duty cycles are typically specified in the standard-setting 

part as a list of discrete operating points (modes or notches), where each operating point has one 

value of a normalized speed command and one value of a normalized torque (or power) 

command. Ramped-modal cycles for steady-state testing also list test times for each mode and 

transition times between modes where speed and torque are linearly ramped between modes, 

Deleted: b
even for cycles with % power. Start a steady-state cycle as a hot running test, where you start to 

measure emissions after an engine is started, warmed up and running. Run a steady-state duty 

cycle as a discrete-mode cycle or a ramped-modal cycle, as follows: 

(i) Discrete-mode cycles. Before emission sampling, stabilize an engine at the first discrete 

mode. Sample emissions and other parameters for that mode in the same manner as a transient 

cycle, with the exception that reference speed and torque values are constant. Record mean 

values for that mode, and then stabilize the engine at the next mode. Continue to sample each 

mode discretely as separate test intervals and calculate weighted emission results according to 

the standard-setting part. 

(ii) Ramped-modal cycles. Perform ramped-modal cycles similar to the way you would perform 

transient cycles, except that ramped-modal cycles involve mostly steady-state engine operation. 

Generate a ramped-modal duty cycle as a sequence of second-by-second (1 Hz) reference speed 

and torque points. Run the ramped-modal duty cycle in the same manner as a transient cycle and 

use the 1 Hz reference speed and torque values to validate the cycle, even for cycles with % 

power. Proportionally sample emissions and other parameters during the cycle and use the 

calculations in subpart G of this part to calculate emissions. 

(d) Other subparts in this part identify how to select and prepare an engine for testing (subpart 

E), how to perform the required engine service accumulation (subpart E), and how to calculate 

emission results (subpart G). 

(e) Subpart J of this part describes how to perform field testing. 

§1065.510 Engine mapping. 

(a) Applicability, scope, and frequency. An engine map is a data set that consists of a series of 

paired data points that represent the maximum brake torque versus engine speed, measured at the 

engine’s primary output shaft. Map your engine if the standard-setting part requires engine 

mapping to generate a duty cycle for your engine configuration. Map your engine while it is 

connected to a dynamometer or other device that can absorb work output from the engine’s 

primary output shaft according to §1065.110. To establish speed and torque values for mapping, 

we generally recommend that you stabilize an engine for at least 15 seconds at each setpoint and 

record the mean feedback speed and torque of the last (4 to 6) seconds. Configure any auxiliary 

work inputs and outputs such as hybrid, turbo-compounding, or thermoelectric systems to 

represent their in-use configurations, and use the same configuration for emission testing. See 

Figure 1 of §1065.210. This may involve configuring initial states of charge and rates and times 

of auxiliary-work inputs and outputs. We recommend that you contact the Designated 

Compliance Officer before testing to determine how you should configure any auxiliary-work 

inputs and outputs. Use the most recent engine map to transform a normalized duty cycle from 

the standard-setting part to a reference duty cycle specific to your engine. Normalized duty 

cycles are specified in the standard-setting part. You may update an engine map at any time by 

repeating the engine-mapping procedure. You must map or re-map an engine before a test if any 

of the following apply: 

(1) If you have not performed an initial engine map. 

(2) If the atmospheric pressure near the engine’s air inlet is not within ±5 kPa of the atmospheric 

pressure recorded at the time of the last engine map. 

Deleted: You may r

Deleted: c

Deleted: d
(3) If the engine or emission-control system has undergone changes that might affect maximum 

torque performance. This includes changing the configuration of auxiliary work inputs and 

outputs. 

(4) If you capture an incomplete map on your first attempt or you do not complete a map within 

the specified time tolerance. You may repeat mapping as often as necessary to capture a 

complete map within the specified time. 

(b) Mapping variable-speed engines. Map variable-speed engines as follows: 

(1) Record the atmospheric pressure. 

(2) Warm up the engine by operating it. We recommend operating the engine at any speed and 

at approximately 75 % of its expected maximum power. Continue the warm-up until the engine 

coolant, block, or head absolute temperature is within ±2 % of its mean value for at least 2 min 

or until the engine thermostat controls engine temperature. 

(3) Operate the engine at its warm idle speed as follows: 

(i) For engines with a low-speed governor, set the operator demand to minimum, use the 

dynamometer or other loading device to target a torque of zero on the engine’s primary output 

shaft, and allow the engine to govern the speed. Measure this warm idle speed; we recommend 

recording at least 30 values of speed and using the mean of those values. 

(ii) For engines without a low-speed governor, operate the engine at warm idle speed and zero 

torque on the engine’s primary output shaft. You may use the dynamometer to target a torque of 

zero on the engine’s primary output shaft, and manipulate the operator demand to control the 

speed to target the manufacturer-declared value for the lowest engine speed possible with 

minimum load (also known as manufacturer-declared warm idle speed). You may alternatively 

use the dynamometer to target the manufacturer-declared warm idle speed and manipulate the 

operator demand to control the torque on the engine’s primary output shaft to zero. 

(iii) For variable-speed engines with or without a low-speed governor, if a nonzero idle torque is 

representative of in-use operation, you may use the dynamometer or operator demand to target 

the manufacturer-declared idle torque instead of targeting zero torque as specified in paragraphs 

(b)(3)(i) and (ii) of this section. Control speed as specified in paragraph (b)(3)(i) or (ii) of this 

section, as applicable. If you use this option for engines with a low-speed governor to measure 

the warm idle speed with the manufacturer-declared torque at this step, you may use this as the 

warm-idle speed for cycle generation as specified in paragraph (b)(6) of this section. However, 

if you identify multiple warm idle torques under paragraph (f)(4)(i) of this section, measure the 

warm idle speed at only one torque level for this paragraph (b)(3). 

(4) Set operator demand to maximum and control engine speed at (95 ±1) % of its warm idle 

speed determined above for at least 15 seconds. For engines with reference duty cycles whose 

lowest speed is greater than warm idle speed, you may start the map at (95 ±1) % of the lowest 

reference speed. 

(5) Perform one of the following: 

(i) For any engine subject only to steady-state duty cycles, you may perform an engine map by 

using discrete speeds. Select at least 20 evenly spaced setpoints from 95% of warm idle speed to 

the highest speed above maximum power at which 50 % of maximum power occurs. We refer to 

this 50 % speed as the check point speed as described in paragraph (b)(5)(iii) of this section. At 

each setpoint, stabilize speed and allow torque to stabilize. Record the mean speed and torque at 

each setpoint. Use linear interpolation to determine intermediate speeds and torques. Use this 
series of speeds and torques to generate the power map as described in paragraph (e) of this 

section. 

(ii) For any variable-speed engine, you may perform an engine map by using a continuous sweep 

of speed by continuing to record the mean feedback speed and torque at 1 Hz or more frequently 

and increasing speed at a constant rate such that it takes (4 to 6) min to sweep from 95 % of 

warm idle speed to the check point speed as described in paragraph (b)(5)(iii) of this section. 

Use good engineering judgment to determine when to stop recording data to ensure that the 

sweep is complete. In most cases, this means that you can stop the sweep at any point after the 

power falls to 50 % of the maximum value. From the series of mean speed and maximum torque 

values, use linear interpolation to determine intermediate values. Use this series of speeds and 

torques to generate the power map as described in paragraph (e) of this section. 

(iii) The check point speed of the map is the highest speed above maximum power at which 50 % 

of maximum power occurs. If this speed is unsafe or unachievable (e.g., for ungoverned engines 

or engines that do not operate at that point), use good engineering judgment to map up to the 

maximum safe speed or maximum achievable speed. For discrete mapping, if the engine cannot 

be mapped to the check point speed, make sure the map includes at least 20 points from 95% of 

warm idle to the maximum mapped speed. For continuous mapping, if the engine cannot be 

mapped to the check point speed, verify that the sweep time from 95 % of warm idle to the 

maximum mapped speed is (4 to 6) min 

(iv) Note that under §1065.10(c)(1) we may allow you to disregard portions of the map when 

selecting maximum test speed if the specified procedure would result in a duty cycle that does 

not represent in-use operation. 

(6) Use one of the following methods to determine warm high-idle speed for engines with a highspeed governor if they are subject to transient testing with a duty cycle that includes reference 

speed values above 100 %: 

(i) You may use a manufacturer-declared warm high-idle speed if the engine is electronically 

governed. For engines with a high-speed governor that shuts off torque output at a 

manufacturer-specified speed and reactivates at a lower manufacturer-specified speed (such as 

engines that use ignition cut-off for governing), declare the middle of the specified speed range 

as the warm high-idle speed. 

(ii) Measure the warm high-idle speed using the following procedure: 

(A) Set operator demand to maximum and use the dynamometer to target zero torque on the 

engine’s primary output shaft. If the mean feedback torque is within ±1 % of Tmax mapped, you 

may use the observed mean feedback speed at that point as the measured warm high-idle speed. 

(B) If the engine is unstable as a result of in-use production components (such as engines that use 

ignition cut-off for governing, as opposed to unstable dynamometer operation), you must use the 

mean feedback speed from paragraph (b)(6)(ii)(A) of this section as the measured warm highidle speed. The engine is considered unstable if any of the 1 Hz speed feedback values are not 

within ±2 % of the calculated mean feedback speed. We recommend that you determine the 

mean as the value representing the midpoint between the observed maximum and minimum 

recorded feedback speed. 

(C) If your dynamometer is not capable of achieving a mean feedback torque within ±1 % of 

Tmax mapped, operate the engine at a second point with operator demand set to maximum with the 

dynamometer set to target a torque equal to the recorded mean feedback torque on the previous 
point plus 20 % of Tmax mapped. Use this data point and the data point from paragraph (b)(6)(ii)(A) 

of this section to extrapolate the engine speed where torque is equal to zero. 

(D) You may use a manufacturer-declared Tmax instead of the measured Tmax mapped. If you do 

this, or if you are able to determine mean feedback speed as described in paragraphs (b)(6)(ii)(A) 

and (B) of this section, you may measure the warm high-idle speed before running the speed 

sweep specified in paragraph (b)(5) of this section. 

(7) For engines with a low-speed governor, if a nonzero idle torque is representative of in-use 

operation, operate the engine at warm idle with the manufacturer-declared idle torque. Set the 

operator demand to minimum, use the dynamometer to target the declared idle torque, and allow 

the engine to govern the speed. Measure this speed and use it as the warm idle speed for cycle 

generation in §1065.512. We recommend recording at least 30 values of speed and using the 

mean of those values. If you identify multiple warm idle torques under paragraph (f)(4)(i) of this 

section, measure the warm idle speed at each torque. You may map the idle governor at multiple 

load levels and use this map to determine the measured warm idle speed at the declared idle 

torque(s). 

(c) Negative torque mapping. If your engine is subject to a reference duty cycle that specifies 

negative torque values (i.e., engine motoring), generate a motoring map by any of the following 

procedures: 

(1) Multiply the positive torques from your map by –40 %. Use linear interpolation to determine 

intermediate values. 

(2) Map the amount of negative torque required to motor the engine by repeating paragraph (b) 

of this section with minimum operator demand. You may start the negative torque map at either 

the minimum or maximum speed from paragraph (b) of this section. 

(3) Determine the amount of negative torque required to motor the engine at the following two 

points near the ends of the engine’s speed range. Operate the engine at these two points at 

minimum operator demand. Use linear interpolation to determine intermediate values. 

(i) Low speed point. For engines without a low-speed governor, determine the amount of 

negative torque at warm idle speed. For engines with a low-speed governor, motor the engine 

above warm idle speed so the governor is inactive and determine the amount of negative torque 

at that speed. 

(ii) High speed point. For engines without a high-speed governor, determine the amount of 

negative torque at the maximum safe speed or the maximum representative speed. For engines 

with a high-speed governor, determine the amount of negative torque at a speed at or above nhi

per §1065.610(c)(2). 

(d) Mapping constant-speed engines. For constant-speed engines, generate a map as follows: 

(1) Record the atmospheric pressure. 

(2) Warm up the engine by operating it. We recommend operating the engine at approximately 

75 % of the engine’s expected maximum power. Continue the warm-up until the engine coolant, 

block, or head absolute temperature is within ±2 % of its mean value for at least 2 min or until 

the engine thermostat controls engine temperature. 

(3) You may operate the engine with a production constant-speed governor or simulate a 

constant-speed governor by controlling engine speed with an operator demand control system 

described in §1065.110. Use either isochronous or speed-droop governor operation, as 

appropriate. 
(4) With the governor or simulated governor controlling speed using operator demand, operate 

the engine at no-load governed speed (at high speed, not low idle) for at least 15 seconds. 

(5) Perform one of the following: 

(i) For constant-speed engines subject only to steady-state testing, you may perform an engine 

map by using a series of discrete torques. Select at least five evenly spaced torque setpoints from 

no-load to 80 % of the manufacturer-declared test torque or to a torque derived from your 

published maximum power level if the declared test torque is unavailable. Starting at the 80 % 

torque point, select setpoints in 2.5 % intervals, stopping at the endpoint torque. The endpoint 

torque is defined as the first discrete mapped torque value greater than the torque at maximum 

observed power where the engine outputs 90 % of the maximum observed power; or the torque 

when engine stall has been determined using good engineering judgment (i.e. sudden 

deceleration of engine speed while adding torque). You may continue mapping at higher torque 

setpoints. At each setpoint, allow torque and speed to stabilize. Record the mean feedback 

speed and torque at each setpoint. From this series of mean feedback speed and torque values, 

use linear interpolation to determine intermediate values. Use this series of mean feedback 

speeds and torques to generate the power map as described in paragraph (e) of this section. 

(ii) For any constant-speed engine, you may perform an engine map with a continuous torque 

sweep by continuing to record the mean feedback speed and torque at 1 Hz or more frequently. 

Use the dynamometer to increase torque. Increase the reference torque at a constant rate from 

no-load to the endpoint torque as defined in paragraph (d)(5)(i) of this section. You may continue 

mapping at higher torque setpoints. Unless the standard-setting part specifies otherwise, target a 

torque sweep rate equal to the manufacturer-declared test torque (or a torque derived from your 

published power level if the declared test torque is not known) divided by 180 s. Stop recording 

after you complete the sweep. Verify that the average torque sweep rate over the entire map is 

within ±7 % of the target torque sweep rate. Use linear interpolation to determine intermediate 

values from this series of mean feedback speed and torque values. Use this series of mean 

feedback speeds and torques to generate the power map as described in paragraph (e) of this 

section. 

(iii) For electric power generation applications in which normal engine operation is limited to a 

specific speed range, map the engine with two points as described in this paragraph (d)(5)(iii). 

After stabilizing at the no-load governed speed in paragraph (d)(4) of this section, record the 

mean feedback speed and torque. Continue to operate the engine with the governor or simulated 

governor controlling engine speed using operator demand, and control the dynamometer to target 

a speed of 97.5 % of the recorded mean no-load governed speed. If the in-use performance class 

of the electric power generation application is known, you may use those values in place of 97.5 

% (e.g., for ISO 8528-5 G3 Performance Class, the steady-state frequency band is less than or 

equal to 0.5 %, so use 99.75 % instead of 97.5 %). Allow speed and torque to stabilize. Record 

the mean feedback speed and torque. Record the target speed. The absolute value of the speed 

error (the mean feedback speed minus the target speed) must be no greater than 20 % of the 

difference between the recorded mean no-load governed speed and the target speed. From this 

series of two mean feedback speed and torque values, use linear interpolation to determine 

intermediate values. Use this series of two mean feedback speeds and torques to generate a 

power map as described in paragraph (e) of this section. Note that the measured maximum test 
torque determined in paragraph (b)(1) of this section will be the mean feedback torque recorded 

on the second point. 

(e) Power mapping. For all engines, create a power-versus-speed map by transforming torque 

and speed values to corresponding power values. Use the mean values from the recorded map 

data. Do not use any interpolated values. Multiply each torque by its corresponding speed and 

apply the appropriate conversion factors to arrive at units of power (kW). Interpolate 

intermediate power values between these power values, which were calculated from the recorded 

map data. 

(f) Measured and declared test speeds and torques. You must select test speeds and torques for 

cycle generation as required in this paragraph (f). “Measured” values are either directly 

measured during the engine mapping process or they are determined from the engine map. 

“Declared” values are specified by the manufacturer. When both measured and declared values 

are available, you may use declared test speeds and torques instead of measured speeds and 

torques if they meet the criteria in this paragraph (f). Otherwise, you must use measured speeds 

and torques derived from the engine map. 

(1) Measured speeds and torques. Determine the applicable speeds and torques for the duty 

cycles you will run: 

(i) Measured maximum test speed for variable-speed engines according to §1065.610. 

(ii) Measured maximum test torque for constant-speed engines according to §1065.610. 

(iii) Measured “A”, “B”, and “C” speeds for variable-speed engines according to §1065.610. 

(iv) Measured intermediate speed for variable-speed engines according to §1065.610. 

(v) For variable-speed engines with a low-speed governor, measure warm idle speed according to 

§1065.510(b) and use this speed for cycle generation in §1065.512. For engines with no lowspeed governor, instead use the manufacturer-declared warm idle speed. 

(2) Required declared speeds. You must declare the lowest engine speed possible with minimum 

load (i.e., manufacturer-declared warm idle speed). This is applicable only to variable-speed 

engines with no low-speed governor. For engines with no low-speed governor, the declared 

warm idle speed is used for cycle generation in §1065.512. Declare this speed in a way that is 

representative of in-use operation. For example, if your engine is typically connected to an 

automatic transmission or a hydrostatic transmission, declare this speed at the idle speed at 

which your engine operates when the transmission is engaged. 

(3) Optional declared speeds. You may use declared speeds instead of measured speeds as 

follows: 

(i) You may use a declared value for maximum test speed for variable-speed engines if it is 

within (97.5 to 102.5) % of the corresponding measured value. You may use a higher declared 

speed if the length of the “vector” at the declared speed is within 2 % of the length of the 

“vector” at the measured value. The term vector refers to the square root of the sum of 

normalized engine speed squared and the normalized full-load power (at that speed) squared, 

consistent with the calculations in §1065.610. 

(ii) You may use a declared value for intermediate, “A”, “B”, or “C” speeds for steady-state tests 

if the declared value is within (97.5 to 102.5) % of the corresponding measured value. 

(iii) For electronically governed engines, you may use a declared warm high-idle speed for 

calculating the alternate maximum test speed as specified in §1065.610. 
(4) Required declared torques. If a nonzero idle or minimum torque is representative of in-use 

operation, you must declare the appropriate torque as follows: 

(i) For variable-speed engines, declare a warm idle torque that is representative of in-use 

operation. For example, if your engine is typically connected to an automatic transmission or a 

hydrostatic transmission, declare the torque that occurs at the idle speed at which your engine 

operates when the transmission is engaged. Use this value for cycle generation. You may use 

multiple warm idle torques and associated idle speeds in cycle generation for representative 

testing. For example, for cycles that start the engine and begin with idle, you may start a cycle in 

idle with the transmission in neutral with zero torque and later switch to a different idle with the 

transmission in drive with the Curb-Idle Transmission Torque (CITT). For variable-speed 

engines intended primarily for propulsion of a vehicle with an automatic transmission where that 

engine is subject to a transient duty cycle with idle operation, you must declare a CITT. You 

must specify a CITT based on typical applications at the mean of the range of idle speeds you 

specify at stabilized temperature conditions. 

(ii) For constant-speed engines, declare a warm minimum torque that is representative of in-use 

operation. For example, if your engine is typically connected to a machine that does not operate 

below a certain minimum torque, declare this torque and use it for cycle generation. 

(5) Optional declared torques. 

(i) For variable-speed engines you may declare a maximum torque over the engine operating 

range. You may use the declared value for measuring warm high-idle speed as specified in this 

section. 

(ii) For constant-speed engines you may declare a maximum test torque. You may use the 

declared value for cycle generation if it is within (95 to 100) % of the measured value. 

(g) Mapping variable-speed engines with an electric hybrid system. Map variable-speed engines 

that include electric hybrid systems as described in this paragraph (g). You may ask to apply 

these provisions to other types of hybrid engines, consistent with good engineering judgment. 

However, do not use this procedure for engines used in hybrid vehicles where the hybrid system 

is certified as part of the vehicle rather than the engine. Follow the steps for mapping a variablespeed engine as given in paragraph (b)(5) of this section except as noted in this paragraph (g). 

You must generate one engine map with the hybrid system inactive as described in paragraph 

(g)(1) of this section, and a separate map with the hybrid system active as described in paragraph 

(g)(2) of this section. See the standard-setting part to determine how to use these maps. The 

map with the system inactive is typically used to generate steady-state duty cycles, but may also 

be used to generate transient cycles, such as those that do not involve engine motoring. This 

hybrid-inactive map is also used for generating the hybrid-active map. The hybrid-active map is 

typically used to generate transient duty cycles that involve engine motoring. 

(1) Prepare the engine for mapping by either deactivating the hybrid system or by operating the 

engine as specified in paragraph (b)(4) of this section and remaining at this condition until the 

rechargeable energy storage system (RESS) is depleted. Once the hybrid has been disabled or 

the RESS is depleted, perform an engine map as specified in paragraph (b)(5) of this section. If 

the RESS was depleted instead of deactivated, ensure that instantaneous power from the RESS 

remains less than 2 % of the instantaneous measured power from the engine (or engine-hybrid 

system) at all engine speeds. 
(2) The purpose of the mapping procedure in this paragraph (g) is to determine the maximum 

torque available at each speed, such as what might occur during transient operation with a fully 

charged RESS. Use one of the following methods to generate a hybrid-active map: 

(i) Perform an engine map by using a series of continuous sweeps to cover the engine’s full 

range of operating speeds. Prepare the engine for hybrid-active mapping by ensuring that the 

RESS state of charge is representative of normal operation. Perform the sweep as specified in 

paragraph (b)(5)(ii) of this section, but stop the sweep to charge the RESS when the power 

measured from the RESS drops below the expected maximum power from the RESS by more 

than 2 % of total system power (including engine and RESS power). Unless good engineering 

judgment indicates otherwise, assume that the expected maximum power from the RESS is equal 

to the measured RESS power at the start of the sweep segment. For example, if the 3-second 

rolling average of total engine-RESS power is 200 kW and the power from the RESS at the 

beginning of the sweep segment is 50 kW, once the power from the RESS reaches 46 kW, stop 

the sweep to charge the RESS. Note that this assumption is not valid where the hybrid motor is 

torque-limited. Calculate total system power as a 3-second rolling average of instantaneous total 

system power. After each charging event, stabilize the engine for 15 seconds at the speed at 

which you ended the previous segment with operator demand set to maximum before continuing 

the sweep from that speed. Repeat the cycle of charging, mapping, and recharging until you 

have completed the engine map. You may shut down the system or include other operation 

between segments to be consistent with the intent of this paragraph (g)(2)(i). For example, for 

systems in which continuous charging and discharging can overheat batteries to an extent that 

affects performance, you may operate the engine at zero power from the RESS for enough time 

after the system is recharged to allow the batteries to cool. Use good engineering judgment to 

smooth the torque curve to eliminate discontinuities between map intervals. 

(ii) Perform an engine map by using discrete speeds. Select map setpoints at intervals defined by 

the ranges of engine speed being mapped. From 95 % of warm idle speed to 90 % of the 

expected maximum test speed, select setpoints that result in a minimum of 13 equally spaced 

speed setpoints. From 90 % to 110 % of expected maximum test speed, select setpoints in 

equally spaced intervals that are nominally 2 % of expected maximum test speed. Above 110 % 

of expected maximum test speed, select setpoints based on the same speed intervals used for 

mapping from 95 % warm idle speed to 90 % maximum test speed. You may stop mapping at 

the highest speed above maximum power at which 50 % of maximum power occurs. We refer to 

the speed at 50 % power as the check point speed as described in paragraph (b)(5)(iii) of this 

section. Stabilize engine speed at each setpoint, targeting a torque value at 70 % of peak torque 

at that speed without hybrid-assist. Make sure the engine is fully warmed up and the RESS state 

of charge is within the normal operating range. Snap the operator demand to maximum, operate 

the engine there for at least 10 seconds, and record the 3-second rolling average feedback speed 

and torque at 1 Hz or higher. Record the peak 3-second average torque and 3-second average 

speed at that point. Use linear interpolation to determine intermediate speeds and torques. 

Follow §1065.610(a) to calculate the maximum test speed. Verify that the measured maximum 

test speed falls in the range from 92 to 108 % of the estimated maximum test speed. If the 

measured maximum test speed does not fall in this range, rerun the map using the measured 

value of maximum test speed. 
(h) Other mapping procedures. You may use other mapping procedures if you believe the 

procedures specified in this section are unsafe or unrepresentative for your engine. Any alternate 

techniques you use must satisfy the intent of the specified mapping procedures, which is to 

determine the maximum available torque at all engine speeds that occur during a duty cycle. 

Identify any deviations from this section’s mapping procedures when you submit data to us. 

§1065.512 Duty cycle generation. 

(a) Generate duty cycles according to this section if the standard-setting part requires engine 

mapping to generate a duty cycle for your engine configuration. The standard-setting part 

generally defines applicable duty cycles in a normalized format. A normalized duty cycle 

generally consists of a sequence of paired values for speed and torque or for speed and power. 

(b) Transform normalized values of speed, torque, and power using the following conventions: 

(1) Engine speed for variable-speed engines. For variable-speed engines, normalized speed may 

be expressed as a percentage between warm idle speed, fnidle, and maximum test speed, fntest, or 

speed may be expressed by referring to a defined speed by name, such as “warm idle,” 

“intermediate speed,” or “A,” “B,” or “C” speed. Section 1065.610 describes how to transform 

these normalized values into a sequence of reference speeds, fnref. Running duty cycles with 

negative or small normalized speed values near warm idle speed may cause low-speed idle 

governors to activate and the engine torque to exceed the reference torque even though the 

operator demand is at a minimum. In such cases, we recommend controlling the dynamometer 

so it gives priority to follow the reference torque instead of the reference speed and let the engine 

govern the speed. Note that the cycle-validation criteria in §1065.514 allow an engine to govern 

itself. This allowance permits you to test engines with enhanced-idle devices and to simulate the 

effects of transmissions such as automatic transmissions. For example, an enhanced-idle device 

might be an idle speed value that is normally commanded only under cold-start conditions to 

quickly warm up the engine and aftertreatment devices. In this case, negative and very low 

normalized speeds will generate reference speeds below this higher enhanced idle speed and we 

recommend controlling the dynamometer so it gives priority to follow the reference torque, 

controlling the operator demand so it gives priority to follow reference speed and let the engine 

govern the speed when the operator demand is at minimum. 

(2) Engine torque for variable-speed engines. For variable-speed engines, normalized torque is 

expressed as a percentage of the mapped torque at the corresponding reference speed. Section 

1065.610 describes how to transform normalized torques into a sequence of reference torques, 

Tref. Section 1065.610 also describes special requirements for modifying transient duty cycles 

for variable-speed engines intended primarily for propulsion of a vehicle with an automatic 

transmission. Section 1065.610 also describes under what conditions you may command Tref

greater than the reference torque you calculated from a normalized duty cycle. This provision 

permits you to command Tref values that are limited by a declared minimum torque. For any 

negative torque commands, command minimum operator demand and use the dynamometer to 

control engine speed to the reference speed, but if reference speed is so low that the idle 

governor activates, we recommend using the dynamometer to control torque to zero, CITT, or a 

declared minimum torque as appropriate. Note that you may omit power and torque points 

during motoring from the cycle-validation criteria in §1065.514. Also, use the maximum mapped 
torque at the minimum mapped speed as the maximum torque for any reference speed at or 

below the minimum mapped speed. 

(3) Engine torque for constant-speed engines. For constant-speed engines, normalized torque is 

expressed as a percentage of maximum test torque, Ttest. Section 1065.610 describes how to 

transform normalized torques into a sequence of reference torques, Tref. Section 1065.610 also 

describes under what conditions you may command Tref greater than the reference torque you 

calculated from the normalized duty cycle. This provision permits you to command Tref values 

that are limited by a declared minimum torque. 

(4) Engine power. For all engines, normalized power is expressed as a percentage of mapped 

power at maximum test speed, fntest, unless otherwise specified by the standard-setting part. 

Section 1065.610 describes how to transform these normalized values into a sequence of 

reference powers, Pref. Convert these reference powers to corresponding torques for operator 

demand and dynamometer control. Use the reference speed associated with each reference 

power point for this conversion. As with cycles specified with % torque, issue torque commands 

more frequently and linearly interpolate between these reference torque values generated from 

cycles with % power. 

(5) Ramped-modal cycles. For ramped modal cycles, generate reference speed and torque values 

at 1 Hz and use this sequence of points to run the cycle and validate it in the same manner as 

with a transient cycle. During the transition between modes, linearly ramp the denormalized 

reference speed and torque values between modes to generate reference points at 1 Hz. Do not 

linearly ramp the normalized reference torque values between modes and then denormalize them. 

Do not linearly ramp normalized or denormalized reference power points. These cases will 

produce nonlinear torque ramps in the denormalized reference torques. If the speed and torque 

ramp runs through a point above the engine’s torque curve, continue to command the reference 

torques and allow the operator demand to go to maximum. Note that you may omit power and 

either torque or speed points from the cycle-validation criteria under these conditions as 

specified in §1065.514. 

(c) For variable-speed engines, command reference speeds and torques sequentially to perform a 

duty cycle. Issue speed and torque commands at a frequency of at least 5 Hz for transient cycles 

and at least 1 Hz for steady-state cycles (i.e., discrete-mode and ramped-modal). Linearly 

interpolate between the 1 Hz reference values specified in the standard-setting part to determine 

more frequently issued reference speeds and torques. During an emission test, record the 

feedback speeds and torques at a frequency of at least 5 Hz for transient cycles and at least 1 Hz 

for steady-state cycles. For transient cycles, you may record the feedback speeds and torques at 

lower frequencies (as low as 1 Hz) if you record the average value over the time interval between 

recorded values. Calculate the average values based on feedback values updated at a frequency 

of at least 5 Hz. Use these recorded values to calculate cycle-validation statistics and total work. 

(d) For constant-speed engines, operate the engine with the same production governor you used 

to map the engine in §1065.510 or simulate the in-use operation of a governor the same way you 

simulated it to map the engine in §1065.510. Command reference torque values sequentially to 

perform a duty cycle. Issue torque commands at a frequency of at least 5 Hz for transient cycles 

and at least 1 Hz for steady-state cycles (i.e., discrete-mode, ramped-modal). Linearly 

interpolate between the 1 Hz reference values specified in the standard-setting part to determine 

more frequently issued reference torque values. During an emission test, record the feedback 
speeds and torques at a frequency of at least 5 Hz for transient cycles and at least 1 Hz for 

steady-state cycles. For transient cycles, you may record the feedback speeds and torques at 

lower frequencies (as low as 1 Hz) if you record the average value over the time interval between 

recorded values. Calculate the average values based on feedback values updated at a frequency 

of at least 5 Hz. Use these recorded values to calculate cycle-validation statistics and total work. 

(e) You may perform practice duty cycles with the test engine to optimize operator demand and 

dynamometer controls to meet the cycle-validation criteria specified in §1065.514. 

§1065.514 Cycle-validation criteria for operation over specified duty cycles. 

Validate the execution of your duty cycle according to this section unless the standard-setting 

part specifies otherwise. This section describes how to determine if the engine’s operation 

during the test adequately matched the reference duty cycle. This section applies only to speed, 

torque, and power from the engine’s primary output shaft. Other work inputs and outputs are not 

subject to cycle-validation criteria. You must compare the original reference duty cycle points 

generated as described in §1065.512 to the corresponding feedback values recorded during the 

test. You may compare reference duty cycle points recorded during the test to the corresponding 

feedback values recorded during the test as long as the recorded reference values match the 

original points generated in §1065.512. The number of points in the validation regression are 

based on the number of points in the original reference duty cycle generated in §1065.512. For 

example if the original cycle has 1199 reference points at 1 Hz, then the regression will have up 

to 1199 pairs of reference and feedback values at the corresponding moments in the test. The 

feedback speed and torque signals may be filtered – either in real-time while the test is run or 

afterward in the analysis program. Any filtering that is used on the feedback signals used for 

cycle validation must also be used for calculating work. Feedback signals for control loops may 

use different filtering. 

(a) Testing performed by EPA. Our tests must meet the specifications of paragraph (f) of this 

section, unless we determine that failing to meet the specifications is related to engine 

performance rather than to shortcomings of the dynamometer or other laboratory equipment. 

(b) Testing performed by manufacturers. Emission tests that meet the specifications of 

paragraph (f) of this section satisfy the standard-setting part’s requirements for duty cycles. You 

may ask to use a dynamometer or other laboratory equipment that cannot meet those 

specifications. We will approve your request as long as using the alternate equipment does not 

adversely affect your ability to show compliance with the applicable emission standards. 

(c) Time-alignment. Because time lag between feedback values and the reference values may 

bias cycle-validation results, you may advance or delay the entire sequence of feedback engine 

speed and torque pairs to synchronize them with the reference sequence. If you advance or delay 

feedback signals for cycle validation, you must make the same adjustment for calculating work. 

You may use linear interpolation between successive recorded feedback signals to time shift an 

amount that is a fraction of the recording period. 

(d) Omitting additional points. Besides engine cranking, you may omit additional points from 

cycle-validation statistics as described in the following table: 

Table 1 of §1065.514— 

Permissible criteria for omitting points from duty-cycle regression statistics 
For reference duty cycles that are specified in terms of speed and torque (fnref, Tref) 

When operator 

demand is at its... 

you may omit... if... 

minimum power and torque Tref < 0 % (motoring) 

minimum power and speed fnref = 0 % (idle speed) and Tref = 0 % (idle torque) and

Tref – (2 % · Tmax mapped) < T < Tref + (2 %  Tmax mapped) 

minimum power and either 

torque or speed 

fn > fnref or T > Tref but not if fn > (fnref  102%) and T 

> Tref + (2 % Tmax mapped)

maximum power and either 

torque or speed 

fn < fnref or T < Tref but not if fn < (fnref  98 %) and T

< Tref – (2 % Tmax mapped)

For reference duty cycles that are specified in terms of speed and power (fnref, Pref) 

When operator 

demand is at its... you may omit... if... 

minimum power and torque Pref < 0 % (motoring) 

minimum power and speed fnref = 0 % (idle speed) and Pref = 0 % (idle power) and

Pref – (2 %  Pmax mapped) < P < Pref + (2 %  Pmax mapped) 

minimum power and either 

torque or speed 

fn > fnref or P > Pref but not if fn > (fnref  102 %) and P 

> Pref + (2 %  Pmax mapped) 

maximum power and either 

torque or speed 

fn < fnref or P < Pref but not if fn < (fnref  98 %) and P < 

Pref – (2 %  Pmax mapped)

(e) Statistical parameters. Use the remaining points to calculate regression statistics described in 

§1065.602. Round calculated regression statistics to the same number of significant digits as the 

criteria to which they are compared. Refer to Table 2 of §1065.514 for the default criteria and 

refer to the standard-setting part to determine if there are other criteria for your engine. 

Calculate the following regression statistics: 

(1) Slopes for feedback speed, a1fn, feedback torque, a1T, and feedback power a1P. 

(2) Intercepts for feedback speed, a0fn, feedback torque, a0T, and feedback power a0P. 

(3) Standard estimates of error for feedback speed, SEEfn, feedback torque, SEET, and feedback 

power SEEP. 

(4) Coefficients of determination for feedback speed, r

2

fn, feedback torque, r

2

T, and feedback 

power r

2

P. 

(f) Cycle-validation criteria. Unless the standard-setting part specifies otherwise, use the 

following criteria to validate a duty cycle: 

(1) For variable-speed engines, apply all the statistical criteria in Table 2 of this section. 

(2) For constant-speed engines, apply only the statistical criteria for torque in Table 2 of this 

section. 

(3) For discrete-mode steady-state testing, apply cycle-validation criteria by treating the 

sampling periods from the series of test modes as a continuous sampling period, analogous to 

ramped-modal testing and apply statistical criteria as described in paragraph (f)(1) or (f)(2) of 

this section. Note that if the gaseous and particulate test intervals are different periods of time, 

separate validations are required for the gaseous and particulate test intervals. Table 2 follows: 
Table 2 of §1065.514—Default statistical criteria for validating duty cycles 

Parameter Speed Torque Power 

Slope, a1 0.950 ≤ a1 ≤ 1.030 0.830 ≤ a1 ≤ 1.030 0.830 ≤ a1 ≤ 1.030 

Absolute value of 

intercept, |a0| ≤ 10 % of warm idle ≤ 2 % of maximum 

mapped torque 

≤ 2 % of maximum 

mapped power 

Standard error of 

estimate, SEE

≤ 5 % of maximum 

test speed 

≤ 10 % of maximum 

mapped torque 

≤ 10 % of maximum 

mapped power 

Coefficient of 

determination, r

2 ≥ 0.970 ≥ 0.850 ≥ 0.910 

§1065.516 Sample system decontamination and preconditioning.

This section describes how to manage the impact of sampling system contamination on emission 

measurements. Contamination occurs when a regulated pollutant accumulates in the sample 

system in a high enough concentration to cause release during emission tests. Hydrocarbons and 

PM are generally the only regulated pollutants that contaminate sample systems. A sampling 

system is considered decontaminated if the contaminants are in equilibrium with measured 

exhaust emissions. Note that although this section focuses on avoiding excessive contamination 

of sample systems, you must also use good engineering judgment to avoid loss of sample to a 

sample system that is too clean. The goal of decontamination is not to perfectly clean the sample 

system, but rather to achieve approximate equilibrium between the sample system and the 

exhaust so that emission components are neither lost to nor entrained from the sample system.

(a) Perform contamination checks as follows to determine if decontamination is needed:

(1) For dilute exhaust sampling systems, measure hydrocarbon and PM emissions by sampling 

with the CVS dilution air turned on, without an engine connected to it.

(2) For raw analyzers and systems that collect PM samples from raw exhaust, measure 

hydrocarbon and PM emissions by sampling zero air or nitrogen.

(3) When calculating zero emission levels, apply all applicable corrections, including initial THC 

contamination and diluted (CVS) exhaust background corrections.

(4) Sampling systems are considered contaminated if either of the following conditions applies:

(i) The hydrocarbon emission level exceeds 2 % of the flow-weighted mean wet, net 

concentration expected at the HC standard.

(ii) The PM emission level exceeds 5 % of the level expected at the standard and exceeds 20 μg 

on a 47 mm PTFE membrane filter.

(b) To precondition/decontaminate sampling systems use the following recommended procedure 

or use good engineering judgment to select a different procedure:

(1) Start the engine and use good engineering judgment to operate it at a condition that generates 

high exhaust temperatures at the sample probe inlet.

(2) Operate any dilution systems at their expected flow rates. Prevent aqueous condensation in 

the dilution systems.

(3) Operate any PM sampling systems at their expected flow rates.

(4) Sample PM for at least 10 min using any sample media. You may change sample media at 

any time during this process and you may discard them without weighing them.

(5) You may purge any gaseous sampling systems that do not require decontamination during 

this procedure.
(6) You may conduct calibrations or verifications on any idle equipment or analyzers during this 

procedure.

(c) If your sampling system is still contaminated following the procedures specified in paragraph 

(b) of this section, you may use more aggressive procedures to decontaminate the sampling 

system, as long as the decontamination does not cause the sampling system to be cleaner than an 

equilibrium condition such that artificially low emission measurements may result.

§1065.518 Engine preconditioning.

(a) This section applies for engines where measured emissions are affected by prior operation, 

such as with a diesel engine that relies on urea-based selective catalytic reduction. Note that 

§1065.520(e) allows you to run practice duty cycles before the emission test; this section 

recommends how to do this for the purpose of preconditioning the engine. We may test your 

engine after completing the minimum amount of preconditioning recommended in this section. 

For subsequent testing, such as steady-state testing following transient testing, we may consider

the previous test cycle as preconditioning. Follow the standard-setting part if it specifies a 

different engine preconditioning procedure.

(b) The intent of engine preconditioning is to manage the representativeness of the emissions 

over the duty cycle, as described in §1065.10(c)(1), by conditioning the engine to a state where it

will emit representative emissions.

(c) The following are the recommended engine preconditioning procedures for different types of 

duty cycles. You may measure emissions during preconditioning cycles, as long as you perform

a predefined number of preconditioning cycles. You must identify before each duty cycle 

whether it is a preconditioning cycle or an emission test. You may not abort an emission test 

based on emissions measured during preconditioning.

(1) Transient cycles. (i) Cold-start transient cycle. Precondition the engine by running at least 

one cold-start or hot-start transient cycle. Immediately after completing the last preconditioning 

cycle, shut down the engine and begin the cold soak as described in §1065.530(a)(1).

(ii) Hot-start transient cycle. Precondition the engine by running at least one hot-start transient 

cycle. Shut down the engine after completing the last preconditioning cycle and start the hotstart transient test as soon as practical.

(iii) Hot-running transient cycle. Precondition the engine by running at least one hot-running 

transient cycle. Start the official hot-running transient cycle as soon as practical after completing 

the last preconditioning cycle.

(2) Steady-state cycles. (i) Discrete-mode cycle. Precondition the engine at the same operating 

condition as the subsequent discrete-mode, unless the standard-setting part specifies sampling 

time limits.

(ii) Ramped-modal cycle. If you run the ramped-modal cycle after a transient test, additional 

preconditioning is allowed, but not required. If you perform additional preconditioning, we 

recommend running the first non-idle mode of the ramped-modal cycle or a mode approximating 

50 % power.

(d) You may conduct calibrations or verifications on any idle equipment or analyzers during 

engine preconditioning.

§1065.520 Pre-test verification procedures and pre-test data collection. 
(a) For tests in which you measure PM emissions, follow the procedures for PM sample 

preconditioning and tare weighing according to §1065.590. 

(b) Unless the standard-setting part specifies different tolerances, verify at some point before the 

test that ambient conditions are within the tolerances specified in this paragraph (b). For 

purposes of this paragraph (b), “before the test” means any time from a point just prior to engine 

starting (excluding engine restarts) to the point at which emission sampling begins. 

(1) Ambient temperature of (20 to 30) °C. See §1065.530(j) for circumstances under which 

ambient temperatures must remain within this range during the test. 

(2) Atmospheric pressure of (80.000 to 103.325) kPa and within ±5 kPa of the value recorded at 

the time of the last engine map. You are not required to verify atmospheric pressure prior to a 

hot start test interval for testing that also includes a cold start. 

(3) Dilution air conditions as specified in §1065.140, except in cases where you preheat your 

CVS before a cold start test. We recommend verifying dilution air conditions just prior to the 

start of each test interval. 

(c) You may test engines at any intake-air humidity, and we may test engines at any intake-air 

humidity. 

(d) Verify that auxiliary-work inputs and outputs are configured as they were during engine 

mapping, as described in§1065.510(a). 

(e) You may perform a final calibration of the speed, torque, and proportional-flow control 

systems, which may include performing practice duty cycles (or portions of duty cycles). This 

may be done in conjunction with the preconditioning in §1065.518.

(f) Verify the amount of nonmethane hydrocarbon contamination in the exhaust and background 

HC sampling systems within 8 hours before the start of the first test interval of each duty-cycle 

sequence for laboratory tests. You may verify the contamination of a background HC sampling 

system by reading the last bag fill and purge using zero gas. For any NMHC measurement 

system that involves separately measuring CH4 and subtracting it from a THC measurement or 

for any CH4 measurement system that uses an NMC, verify the amount of THC contamination 

using only the THC analyzer response. There is no need to operate any separate CH4 analyzer 

for this verification; however, you may measure and correct for THC contamination in the CH4

sample train for the cases where NMHC is determined by subtracting CH4 from THC or, where 

CH4 is determined, using an NMC as configured in §1065.365(d), (e), and (f); and using the 

calculations in §1065.660(b)(2). Perform this verification as follows: 

(1) Select the HC analyzer range for measuring the flow-weighted mean concentration expected 

at the HC standard. 

(2) Zero the HC analyzer at the analyzer zero or sample port. Note that FID zero and span 

balance gases may be any combination of purified air or purified nitrogen that meets the 

specifications of §1065.750. We recommend FID analyzer zero and span gases that contain 

approximately the flow-weighted mean concentration of O2 expected during testing. 

(3) Span the HC analyzer using span gas introduced at the analyzer span or sample port. Span on 

a carbon number basis of one (C1). For example, if you use a C3H8 span gas of concentration 

200 mol/mol, span the FID to respond with a value of 600 mol/mol. 

(4) Overflow zero gas at the HC probe inlet or into a tee near the probe outlet. 

(5) Measure the THC concentration in the sampling and background systems as follows: 

(i) For continuous sampling, record the mean THC concentration as overflow zero gas flows. 

Deleted: If your engine must comply with a PM 

standard

Deleted: (f) You may perform the following 

recommended procedure to precondition sampling 

systems:¶

(1) Start the engine and use good engineering 

judgment to bring it to one of the following:¶

(i) 100 % torque at any speed above its peak-torque 

speed.¶

(ii) 100% operator demand.¶

(2) Operate any dilution systems at their expected 

flow rates. Prevent aqueous condensation in the 

dilution systems. ¶

(3) Operate any PM sampling systems at their 

expected flow rates.¶

(4) Sample PM for at least 10 min using any sample 

media. You may change sample media during 

preconditioning. You may discard preconditioning 

samples without weighing them.¶

(5) You may purge any gaseous sampling systems 

during preconditioning.¶

(6) You may conduct calibrations or verifications on 

any idle equipment or analyzers during 

preconditioning.¶

(7) Proceed with the test sequence described in 

§1065.530(a)(1).¶

Deleted: g

Deleted: methane 

Deleted: methane 
(ii) For batch sampling, fill the sample medium (e.g., bag) and record its mean THC 

concentration. 

(iii) For the background system, record the mean THC concentration of the last fill and purge. 

(6) Record this value as the initial THC concentration, xTHC[THC-FID]init, and use it to correct 

measured values as described in §1065.660. 

(7) You may correct the measured initial THC concentration for drift as follows: 

(i) For batch and continuous HC analyzers, after determining the initial THC concentration, flow 

zero gas to the analyzer zero or sample port. When the analyzer reading is stable, record the 

mean analyzer value. 

(ii) Flow span gas to the analyzer span or sample port. When the analyzer reading is stable, 

record the mean analyzer value. 

(iii) Use mean analyzer values from paragraphs (f)(2), (3), (7)(i), and (7)(ii) of this section to 

correct the initial THC concentration recorded in paragraph (f)(6) of this section for drift, as 

described in §1065.550. 

(8) If any of the xTHC[THC-FID]init values exceed the greatest of the following values, determine the 

source of the contamination and take corrective action, such as purging the system during an 

additional preconditioning cycle or replacing contaminated portions: 

(i) 2 % of the flow-weighted mean wet, net concentration expected at the HC (THC or NMHC) 

standard. 

(ii) 2 % of the flow-weighted mean wet, net concentration of HC (THC or NMHC) measured 

during testing. 

(iii) 2 mol/mol. 

(9) If corrective action does not resolve the deficiency, you may request to use the contaminated 

system as an alternate procedure under §1065.10. 

§1065.525 Engine starting, restarting, and shutdown. 

(a) For test intervals that require emission sampling during engine starting, start the engine using 

one of the following methods: 

(1) Start the engine as recommended in the owners manual using a production starter motor or 

air-start system and either an adequately charged battery, a suitable power supply, or a suitable 

compressed air source. 

(2) Use the dynamometer to start the engine. To do this, motor the engine within ±25 % of its 

typical in-use cranking speed. Stop cranking within 1 second of starting the engine. 

(3) In the case of hybrid engines, activate the system such that the engine will start when its 

control algorithms determine that the engine should provide power instead of or in addition to 

power from the RESS. Unless we specify otherwise, engine starting throughout this part 

generally refers to this step of activating the system on hybrid engines, whether or not that causes 

the engine to start running. 

(b) If the engine does not start after 15 seconds of cranking, stop cranking and determine why the 

engine failed to start, unless the owners manual or the service-repair manual describes the longer 

cranking time as normal. 

(c) Respond to engine stalling with the following steps: 

(1) If the engine stalls during warm-up before emission sampling begins, restart the engine and 

continue warm-up. 

Deleted: g

Deleted: g
(2) If the engine stalls during preconditioning before emission sampling begins, restart the engine 

and restart the preconditioning sequence. 

(3) Void the entire test if the engine stalls at any time after emission sampling begins, except as 

described in §1065.526. If you do not void the entire test, you must void the individual test 

mode or test interval in which the engine stalls. 

(d) Shut down the engine according to the manufacturer’s specifications. 

§1065.526 Repeating of void modes or test intervals. 

(a) Test modes and test intervals can be voided because of instrument malfunctions, engine 

stalling, or emissions exceeding instrument ranges. This section specifies circumstances for 

which a test mode or test interval can be repeated without repeating the entire test. 

(b) This section is intended to result in replicate test modes and test intervals that are identical to 

what would have occurred if the cause of the voiding had not occurred. It does not allow you to 

repeat test modes or test intervals in any circumstances that would be inconsistent with good 

engineering judgment. For example, the procedures specified here for repeating a mode or 

interval may not apply for certain engines that include hybrid energy storage features or emission 

controls that involve physical or chemical storage of pollutants. This section applies for 

circumstances in which emission concentrations exceed the analyzer range only if it is due to 

operator error or analyzer malfunction. It does not apply for circumstances in which the 

emission concentrations exceed the range because they were higher than expected. 

(c) If one of the modes of a discrete-mode test is voided as provided in this section, you may 

void the results for that individual mode and continue the test as follows: 

(1) If the engine has stalled or been shut down, restart the engine. 

(2) Use good engineering judgment to restart the test sequence using the appropriate steps in 

§1065.530(b). 

(3) Precondition the engine by operating it at the mode at which the test was interrupted and 

continue with the duty cycle as specified in the standard-setting part. 

(d) If a transient or ramped-modal cycle test interval is voided as provided in this section, you 

may repeat the test interval as follows: 

(1) Use good engineering judgment to restart (as applicable) and precondition the engine to the 

same condition as would apply for normal testing. This may require you to complete the voided 

test interval. For example, you may generally repeat a hot-start test of a heavy-duty highway 

engine after completing the voided hot-start test and allowing the engine to soak for 20 minutes. 

(2) Complete the remainder of the test according to the provisions in this subpart. 

(e) Keep records from the voided test mode or test interval in the same manner as required for 

unvoided tests. 

§1065.530 Emission test sequence. 

(a) Time the start of testing as follows: 

(1) Perform one of the following if you precondition the engine as described in §1065.518: 

(i) For cold-start duty cycles, shut down the engine. Unless the standard-setting part specifies 

that you may only perform a natural engine cooldown, you may perform a forced engine 

cooldown. Use good engineering judgment to set up systems to send cooling air across the 

engine, to send cool oil through the engine lubrication system, to remove heat from coolant 

Deleted: previous mode for approximately the 

same amount of time it operated at that mode for the 

previous emission measurement.¶

(4) Advance to the 

Deleted: and emission sampling system 

Deleted: sampling systems

Deleted: 20(f)
through the engine cooling system, and to remove heat from any exhaust aftertreatment systems. 

In the case of a forced aftertreatment cooldown, good engineering judgment would indicate that 

you not start flowing cooling air until the aftertreatment system has cooled below its catalytic 

activation temperature. For platinum-group metal catalysts, this temperature is about 200 °C. 

Once the aftertreatment system has naturally cooled below its catalytic activation temperature, 

good engineering judgment would indicate that you use clean air with a temperature of at least 

15 °C, and direct the air through the aftertreatment system in the normal direction of exhaust 

flow. Do not use any cooling procedure that results in unrepresentative emissions (see 

§1065.10(c)(1)). You may start a cold-start duty cycle when the temperatures of an engine's 

lubricant, coolant, and aftertreatment systems are all between (20 and 30) °C. 

(ii) For hot-start emission measurements, immediately after completing the last preconditioning 

cycle, shut down the engine and as soon as practical start the official hot-start transient cycle. 

We will start the official hot-start transient cycle within 1 minute of the conclusion of the 

preconditioning cycle where applicable. Start the hot-start duty cycle as specified in the 

standard-setting part if it is different from this procedure. 

(iii) For testing that involves hot-stabilized emission measurements, such as any steady-state 

testing, as soon as practical after completing the discrete-mode preconditioning time or the last 

preconditioning cycle, without shutting down the engine, start the official hot-stabilized cycle. 

We will start the official hot-stabilized cycle within 1 minute of the conclusion of the 

preconditioning cycle where applicable. If the last preconditioning cycle ends with a different 

operating condition as the beginning of the hot-stabilized cycle, add a linear transition period of 

20 s between cycles where you linearly ramp the (denormalized) reference speed and torque 

values over the transition period.

(2) If you do not precondition the engine as described in §1065.518, perform one of the 

following: 

(i) For cold-start duty cycles, prepare the engine according to paragraph (a)(1)(i) of this section. 

(ii) For hot-start emission measurements, first operate the engine at any speed above peak-torque 

speed and at (65 to 85) % of maximum mapped power until either the engine coolant, block, or 

head absolute temperature is within ±2 % of its mean value for at least 2 min or until the engine 

thermostat controls engine temperature. Shut down the engine. Start the duty cycle within 20 

min of engine shutdown. 

(iii) For testing that involves hot-stabilized emission measurements, bring the engine either to 

warm idle or the first operating point of the duty cycle. Start the test within 10 min of achieving 

temperature stability. Determine temperature stability either as the point at which the engine 

coolant, block, or head absolute temperature is within ±2 % of its mean value for at least 2 min, 

or as the point at which the engine thermostat controls engine temperature. 

(b) Take the following steps before emission sampling begins: 

(1) For batch sampling, connect clean storage media, such as evacuated bags or tare-weighed 

filters. 

(2) Start all measurement instruments according to the instrument manufacturer’s instructions 

and using good engineering judgment. 

(3) Start dilution systems, sample pumps, cooling fans, and the data-collection system. 

(4) Pre-heat or pre-cool heat exchangers in the sampling system to within their operating 

temperature tolerances for a test. 

Deleted: you may continue to operate the engine at 

maximum test speed and 100 % torque if that is the 

first operating point. Otherwise, operate the engine 

at warm idle or the first operating point of the duty 

cycle. In any case, start the emission test within 10 

min after you complete the preconditioning 

procedure.

Deleted: sampling systems
(5) Allow heated or cooled components such as sample lines, filters, chillers, and pumps to 

stabilize at their operating temperatures. 

(6) Verify that there are no significant vacuum-side leaks according to §1065.345. 

(7) Adjust the sample flow rates to desired levels, using bypass flow, if desired. 

(8) Zero or re-zero any electronic integrating devices, before the start of any test interval. 

(9) Select gas analyzer ranges. You may automatically or manually switch gas analyzer ranges 

during a test only if switching is performed by changing the span over which the digital 

resolution of the instrument is applied. During a test you may not switch the gains of an 

analyzer’s analog operational amplifier(s). 

(10) Zero and span all continuous analyzers using NIST-traceable gases that meet the 

specifications of §1065.750. Span FID analyzers on a carbon number basis of one (1), C1. For 

example, if you use a C3H8 span gas of concentration 200 mol/mol, span the FID to respond 

with a value of 600 mol/mol. Span FID analyzers consistent with the determination of their 

respective response factors, RF, and penetration fractions, PF, according to §1065.365. 

(11) We recommend that you verify gas analyzer responses after zeroing and spanning by 

sampling a calibration gas that has a concentration near one-half of the span gas concentration. 

Based on the results and good engineering judgment, you may decide whether or not to re-zero, 

re-span, or re-calibrate a gas analyzer before starting a test. 

(12) Drain any accumulated condensate from the intake air system before starting a duty cycle, 

as described in §1065.125(e)(1). If engine and aftertreatment preconditioning cycles are run 

before the duty cycle, treat the preconditioning cycles and any associated soak period as part of 

the duty cycle for the purpose of opening drains and draining condensate. Note that you must 

close any intake air condensate drains that are not representative of those normally open during 

in-use operation. 

(c) Start testing as follows: 

(1) If engine starting is not part of the duty cycle, perform the following for the various duty 

cycles: 

(i) Transient and steady-state ramped-modal cycles. Simultaneously start recording continuous 

data, any electronic integrating devices, batch sampling, and execution of the duty cycle. 

(ii) Steady-state discrete-mode cycles. Control the engine operation to match the first mode in 

the test cycle. This will require controlling engine speed and load, engine load, or other operator 

demand settings, as specified in the standard-setting part. Follow the instructions in the 

standard-setting part to determine how long to stabilize engine operation at each mode, how long 

to sample emissions at each mode, and how to transition between modes. For each mode, 

simultaneously start recording continuous data, any electronic integrating devices, and batch 

sampling.

(2) If engine starting is part of the duty cycle, simultaneously start recording continuous data, 

any electronic integrating devices, and batch sampling before attempting to start the engine. 

Initiate the duty cycle when the engine starts.

(3) For batch sampling systems you may use good engineering judgment to advance or delay the 

start and stop of sampling with respect to the beginning and end of the test interval to improve 

the accuracy of the batch sample.

(d) At the end of each test interval, continue to operate all sampling and dilution systems to allow 

the sampling system’s response time to elapse. Then stop all sampling and recording, including 

Deleted: (12) If you correct for dilution air 

background concentrations of engine exhaust 

constituents, startmeasuring and recording 

background concentrations.¶

Deleted: 3

Deleted: an 

Deleted: is already running and warmed up, and 

Deleted: running 

Deleted: , sampling exhaust gases, recording data, 

and integrating measured values

Deleted: initiate data logging, sampling of exhaust 

gases, and integrating measured values
the recording of background samples. Finally, stop any integrating devices and indicate the end 

of the duty cycle in the recorded data. 

(e) Shut down the engine if you have completed testing or if it is part of the duty cycle. 

(f) If testing involves another duty cycle after a soak period with the engine off, start a timer 

when the engine shuts down, and repeat the steps in paragraphs (b) through (e) of this section as 

needed. 

(g) Take the following steps after emission sampling is complete: 

(1) For any proportional batch sample, such as a bag sample or PM sample, verify that 

proportional sampling was maintained according to §1065.545. Void any samples that did not 

maintain proportional sampling according to §1065.545. 

(2) Place any used PM samples into covered or sealed containers and return them to the PMstabilization environment. Follow the PM sample post-conditioning and total weighing 

procedures in §1065.595. 

(3) As soon as practical after the duty cycle is complete, or during the soak period if practical, 

perform the following: 

(i) Zero and span all batch gas analyzers no later than 30 minutes after the duty cycle is 

complete, or during the soak period if practical. 

(ii) Analyze any conventional gaseous batch samples no later than 30 minutes after the duty 

cycle is complete, or during the soak period if practical. 

(iii) Analyze background samples no later than 60 minutes after the duty cycle is complete. 

(iv) Analyze non-conventional gaseous batch samples, such as ethanol (NMHCE) as soon as 

practical using good engineering judgment. 

(4) After quantifying exhaust gases, verify drift as follows: 

(i) For batch and continuous gas analyzers, record the mean analyzer value after stabilizing a 

zero gas to the analyzer. Stabilization may include time to purge the analyzer of any sample gas, 

plus any additional time to account for analyzer response. 

(ii) Record the mean analyzer value after stabilizing the span gas to the analyzer. Stabilization 

may include time to purge the analyzer of any sample gas, plus any additional time to account for 

analyzer response. 

(iii) Use these data to validate and correct for drift as described in §1065.550. 

(h) Unless the standard-setting part specifies otherwise, determine whether or not the test meets 

the cycle-validation criteria in §1065.514. 

(1) If the criteria void the test, you may retest using the same denormalized duty cycle, or you 

may re-map the engine, denormalize the reference duty cycle based on the new map and retest 

the engine using the new denormalized duty cycle. 

(2) If the criteria void the test for a constant-speed engine only during commands of maximum 

test torque, you may do the following: 

(i) Determine the first and last feedback speeds at which maximum test torque was commanded. 

(ii) If the last speed is greater than or equal to 90 % of the first speed, the test is void. You may 

retest using the same denormalized duty cycle, or you may re-map the engine, denormalize the 

reference duty cycle based on the new map and retest the engine using the new denormalized 

duty cycle. 

(iii) If the last speed is less than 90 % of the first speed, reduce maximum test torque by 5 %, and 

proceed as follows: 
(A) Denormalize the entire duty cycle based on the reduced maximum test torque according to 

§1065.512. 

(B) Retest the engine using the denormalized test cycle that is based on the reduced maximum 

test torque. 

(C) If your engine still fails the cycle criteria, reduce the maximum test torque by another 5 % of 

the original maximum test torque. 

(D) If your engine fails after repeating this procedure four times, such that your engine still fails 

after you have reduced the maximum test torque by 20 % of the original maximum test torque, 

notify us and we will consider specifying a more appropriate duty cycle for your engine under 

the provisions of §1065.10(c). 

(i) [Reserved] 

(j) Measure and record ambient temperature, pressure, and humidity, as appropriate. For testing 

the following engines, you must record ambient temperature continuously to verify that it 

remains within the pre-test temperature range as specified in §1065.520(b): 

(1) Air-cooled engines. 

(2) Engines equipped with auxiliary emission control devices that sense and respond to ambient 

temperature. 

(3) Any other engine for which good engineering judgment indicates this is necessary to remain 

consistent with §1065.10(c)(1). 

§1065.545 Verification of proportional flow control for batch sampling. 

For any proportional batch sample such as a bag or PM filter, demonstrate that proportional 

sampling was maintained using one of the following, noting that you may omit up to 5 % of the 

total number of data points as outliers: 

(a) For any pair of flow rates, use recorded sample and total flow rates, where total flow rate 

means the raw exhaust flow rate for raw exhaust sampling and the dilute exhaust flow rate for 

CVS sampling, or their 1 Hz means with the statistical calculations in §1065.602. Determine the 

standard error of the estimate, SEE, of the sample flow rate versus the total flow rate. For each 

test interval, demonstrate that SEE was less than or equal to 3.5 % of the mean sample flow rate. 

(b) For any pair of flow rates, use recorded sample and total flow rates, where total flow rate 

means the raw exhaust flow rate for raw exhaust sampling and the dilute exhaust flow rate for 

CVS sampling, or their 1 Hz means to demonstrate that each flow rate was constant within ±2.5 

% of its respective mean or target flow rate. You may use the following options instead of 

recording the respective flow rate of each type of meter: 

(1) Critical-flow venturi option. For critical-flow venturis, you may use recorded venturi-inlet 

conditions or their 1 Hz means. Demonstrate that the flow density at the venturi inlet was 

constant within ±2.5 % of the mean or target density over each test interval. For a CVS criticalflow venturi, you may demonstrate this by showing that the absolute temperature at the venturi 

inlet was constant within ±4 % of the mean or target absolute temperature over each test interval. 

(2) Positive-displacement pump option. You may use recorded pump-inlet conditions or their 1 

Hz means. Demonstrate that the flow density at the pump inlet was constant within ±2.5 % of 

the mean or target density over each test interval. For a CVS pump, you may demonstrate this 

by showing that the absolute temperature at the pump inlet was constant within ±2 % of the 

mean or target absolute temperature over each test interval. 

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(c) Using good engineering judgment, demonstrate with an engineering analysis that the 

proportional-flow control system inherently ensures proportional sampling under all 

circumstances expected during testing. For example, you might use CFVs for both sample flow 

and total dilute exhaust (CVS) flow and demonstrate that they always have the same inlet 

pressures and temperatures and that they always operate under critical-flow conditions. 

§1065.546 Verification of minimum dilution ratio for PM batch sampling. 

Use continuous flows and/or tracer gas concentrations for transient and ramped modal cycles to 

verify the minimum dilution ratios for PM batch sampling as specified in §1065.140(e)(2) over 

the test interval. You may use mode-average values instead of continuous measurements for 

discrete mode steady-state duty cycles. Determine the minimum primary and minimum overall 

dilution ratios using one of the following methods (you may use a different method for each 

stage of dilution): 

(a) Determine minimum dilution ratio based on molar flow data. This involves determination of 

at least two of the following three quantities: raw exhaust flow (or previously diluted flow), 

dilution air flow, and dilute exhaust flow. You may determine the raw exhaust flow rate based 

on the measured intake air or fuel flow rate and the raw exhaust chemical balance terms as given 

in §1065.655(e). You may determine the raw exhaust flow rate based on the measured intake air 

and dilute exhaust molar flow rates and the dilute exhaust chemical balance terms as given in 

§1065.655(f). You may alternatively estimate the molar raw exhaust flow rate based on intake 

air, fuel rate measurements, and fuel properties, consistent with good engineering judgment. 

(b) Determine minimum dilution ratio based on tracer gas (e.g., CO2) concentrations in the raw 

(or previously diluted) and dilute exhaust corrected for any removed water. 

(c) Use good engineering judgment to develop your own method of determining dilution ratios. 

§1065.550 Gas analyzer range verification and drift verification. 

(a) Range verification. If an analyzer operated above 100 % of its range at any time during the 

test, perform the following steps: 

(1) For batch sampling, re-analyze the sample using the lowest analyzer range that results in a 

maximum instrument response below 100 %. Report the result from the lowest range from 

which the analyzer operates below 100 % of its range. 

(2) For continuous sampling, repeat the entire test using the next higher analyzer range. If the 

analyzer again operates above 100 % of its range, repeat the test using the next higher range. 

Continue to repeat the test until the analyzer always operates at less than 100 % of its range. 

(b) Drift verification. Gas analyzer drift verification is required for all gaseous exhaust 

constituents for which an emission standard applies. It is also required for CO2 even if there is 

no CO2 emission standard. It is not required for other gaseous exhaust constituents for which 

only a reporting requirement applies (such as CH4 and N2O). 

(1) Verify drift using one of the following methods: 

(i) For regulated exhaust constituents determined from the mass of a single component, perform 

drift verification based on the regulated constituent. For example, when NOx mass is determined 

with a dry sample measured with a CLD and the removed water is corrected based on measured 

CO2, CO, THC, and NOx concentrations, you must verify the calculated NOx value. 

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(ii) For regulated exhaust constituents determined from the masses of multiple subcomponents, 

perform the drift verification based on either the regulated constituent or all the mass 

subcomponents. For example, when NOx is measured with separate NO and NO2 analyzers, you 

must verify either the NOx value or both the NO and NO2 values. 

(iii) For regulated exhaust constituents determined from the concentrations of multiple gaseous 

emission subcomponents prior to performing mass calculations, perform drift verification on the 

regulated constituent. You may not verify the concentration subcomponents (e.g., THC and CH4

for NMHC) separately. For example, for NMHC measurements, perform drift verification on 

NMHC; do not verify THC and CH4 separately. 

(2) Drift verification requires two sets of emission calculations. For each set of calculations, 

include all the constituents in the drift verification. Calculate one set using the data before drift 

correction and calculate the other set after correcting all the data for drift according to 

§1065.672. Note that for purposes of drift verification, you must leave unaltered any negative 

emission results over a given test interval (i.e., do not set them to zero). These unaltered results 

are used when verifying either test interval results or composite brake-specific emissions over 

the entire duty cycle for drift. For each constituent to be verified, both sets of calculations must 

include the following: 

(i) Calculated mass (or mass rate) emission values over each test interval. 

(ii) If you are verifying each test interval based on brake-specific values, calculate brake-specific 

emission values over each test interval. 

(iii) If you are verifying over the entire duty cycle, calculate composite brake-specific emission 

values. 

(3) The duty cycle is verified for drift if you satisfy the following criteria: 

(i) For each regulated gaseous exhaust constituent, you must satisfy one of the following:

(A) For each test interval of the duty cycle, the difference between the uncorrected and the 

corrected brake-specific emission values of the regulated constituent must be within ±4 % of the 

uncorrected value or the applicable emissions standard, whichever is greater. Alternatively, the 

difference between the uncorrected and the corrected emission mass (or mass rate) values of the 

regulated constituent must be within 4 % of the uncorrected value or the composite work (or 

power) multiplied by the applicable emissions standard, whichever is greater. For purposes of 

verifying each test interval, you may use either the reference or actual composite work (or 

power). 

(B) For each test interval of the duty cycle and for each mass subcomponent of the regulated 

constituent, the difference between the uncorrected and the corrected brake-specific emission 

values must be within ±4 % of the uncorrected value. Alternatively, the difference between the 

uncorrected and the corrected emissions mass (or mass rate) values must be within ±4 % of the 

uncorrected value. 

(C) For the entire duty cycle, the difference between the uncorrected and the corrected composite 

brake-specific emission values of the regulated constituent must be within ±4 % of the 

uncorrected value or applicable emission standard, whichever is greater. 

(D) For the entire duty cycle and for each subcomponent of the regulated constituent, the 

difference between the uncorrected and the corrected composite brake-specific emission values 

must be within ±4 % of the uncorrected value. 

(ii) Where no emission standard applies for CO2, you must satisfy one of the following: 

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(A) For each test interval of the duty cycle, the difference between the uncorrected and the 

corrected brake-specific CO2 values must be within ±4 % of the uncorrected value; or the 

difference between the uncorrected and the corrected CO2 mass (or mass rate) values must be 

within ±4 % of the uncorrected value. 

(B) For the entire duty cycle, the difference between the uncorrected and the corrected composite 

brake-specific CO2 values must be within ±4 % of the uncorrected value. 

(4) If the test is not verified for drift as described in paragraph (b)(1) of this section, you may 

consider the test results for the duty cycle to be valid only if, using good engineering judgment, 

the observed drift does not affect your ability to demonstrate compliance with the applicable 

emission standards. For example, if the drift-corrected value is less than the standard by at least 

two times the absolute difference between the uncorrected and corrected values, you may 

consider the data to be verified for demonstrating compliance with the applicable standard.

§1065.590 PM sampling media (e.g., filters) preconditioning and tare weighing. 

Before an emission test, take the following steps to prepare PM sampling media (e.g., filters) and 

equipment for PM measurements: 

(a) Make sure the balance and PM-stabilization environments meet the periodic verifications in 

§1065.390. 

(b) Visually inspect unused sample media (e.g., filters) for defects and discard defective media. 

(c) To handle PM sampling media (e.g., filters), use electrically grounded tweezers or a 

grounding strap, as described in §1065.190. 

(d) Place unused sample media (e.g., filters) in one or more containers that are open to the PMstabilization environment. If you are using filters, you may place them in the bottom half of a 

filter cassette. 

(e) Stabilize sample media (e.g., filters) in the PM-stabilization environment. Consider an 

unused sample medium stabilized as long as it has been in the PM-stabilization environment for 

a minimum of 30 min, during which the PM-stabilization environment has been within the 

specifications of §1065.190. 

(f) Weigh the sample media (e.g., filters) automatically or manually, as follows: 

(1) For automatic weighing, follow the automation system manufacturer’s instructions to prepare 

samples for weighing. This may include placing the samples in a special container. 

(2) For manual weighing, use good engineering judgment to determine if substitution weighing is 

necessary to show that an engine meets the applicable standard. You may follow the substitution 

weighing procedure in paragraph (j) of this section, or you may develop your own procedure. 

(g) Correct the measured mass of each sample medium (e.g., filter) for buoyancy as described in 

§1065.690. These buoyancy-corrected values are subsequently subtracted from the post-test 

mass of the corresponding sample media (e.g., filters) and collected PM to determine the mass of 

PM emitted during the test. 

(h) You may repeat measurements to determine the mean mass of each sample medium (e.g., 

filter). Use good engineering judgment to exclude outliers from the calculation of mean mass 

values. 

(i) If you use filters as sample media, load unused filters that have been tare-weighed into clean 

filter cassettes and place the loaded cassettes in a clean, covered or sealed container before 

removing them from the stabilization environment for transport to the test site for sampling. We 

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Deleted: valid 
recommend that you keep filter cassettes clean by periodically washing or wiping them with a 

compatible solvent applied using a lint-free cloth. Depending upon your cassette material, 

ethanol (C2H5OH) might be an acceptable solvent. Your cleaning frequency will depend on your 

engine’s level of PM and HC emissions. 

(j) Substitution weighing involves measurement of a reference weight before and after each 

weighing of PM sampling media (e.g., filters). While substitution weighing requires more 

measurements, it corrects for a balance’s zero-drift and it relies on balance linearity only over a 

small range. This is most advantageous when quantifying net PM masses that are less than 0.1 

% of the sample medium’s mass. However, it may not be advantageous when net PM masses 

exceed 1 % of the sample medium’s mass. If you utilize substitution weighing, it must be used 

for both pre-test and post-test weighing. The same substitution weight must be used for both 

pre-test and post-test weighing. Correct the mass of the substitution weight for buoyancy if the 

density of the substitution weight is less than 2.0 g/cm3

. The following steps are an example of 

substitution weighing:

(1) Use electrically grounded tweezers or a grounding strap, as described in §1065.190. 

(2) Use a static neutralizer as described in §1065.190 to minimize static electric charge on any 

object before it is placed on the balance pan. 

(3) Select a substitution weight that meets the requirements for calibration weights found in 

§1065.790. The substitution weight must also have the same density as the weight you use to 

span the microbalance, and be similar in mass to an unused sample medium (e.g., filter). A 47 

mm PTFE membrane filter will typically have a mass in the range of 80 to 100 mg. 

(4) Record the stable balance reading, then remove the calibration weight. 

(5) Weigh an unused sample medium (e.g., a new filter), record the stable balance reading and 

record the balance environment's dewpoint, ambient temperature, and atmospheric pressure. 

(6) Reweigh the calibration weight and record the stable balance reading. 

(7) Calculate the arithmetic mean of the two calibration-weight readings that you recorded 

immediately before and after weighing the unused sample. Subtract that mean value from the 

unused sample reading, then add the true mass of the calibration weight as stated on the 

calibration-weight certificate. Record this result. This is the unused sample’s tare weight 

without correcting for buoyancy. 

(8) Repeat these substitution-weighing steps for the remainder of your unused sample media. 

(9) Once weighing is completed, follow the instructions given in paragraphs (g) through (i) of 

this section. 

§1065.595 PM sample post-conditioning and total weighing. 

After testing is complete, return the sample media (e.g., filters) to the weighing and PMstabilization environments. 

(a) Make sure the weighing and PM-stabilization environments meet the ambient condition 

specifications in §1065.190(e)(1). If those specifications are not met, leave the test sample 

media (e.g., filters) covered until proper conditions have been met. 

(b) In the PM-stabilization environment, remove PM samples from sealed containers. If you use 

filters, you may remove them from their cassettes before or after stabilization. We recommend 

always removing the top portion of the cassette before stabilization. When you remove a filter 
from a cassette, separate the top half of the cassette from the bottom half using a cassette 

separator designed for this purpose. 

(c) To handle PM samples, use electrically grounded tweezers or a grounding strap, as described 

in §1065.190. 

(d) Visually inspect the sampling media (e.g., filters) and collected particulate. If either the 

sample media (e.g. filters) or particulate sample appear to have been compromised, or the 

particulate matter contacts any surface other than the filter, the sample may not be used to 

determine particulate emissions. In the case of contact with another surface, clean the affected 

surface before continuing. 

(e) To stabilize PM samples, place them in one or more containers that are open to the PMstabilization environment, as described in §1065.190. If you expect that a sample medium’s 

(e.g., filter’s) total surface concentration of PM will be less than 400 μg, assuming a 38 mm 

diameter filter stain area, expose the filter to a PM-stabilization environment meeting the 

specifications of §1065.190 for at least 30 minutes before weighing. If you expect a higher PM 

concentration or do not know what PM concentration to expect, expose the filter to the 

stabilization environment for at least 60 minutes before weighing. Note that 400 μg on sample 

media (e.g., filters) is an approximate net mass of 0.07 g/kW·hr for a hot-start test with 

compression-ignition engines tested according to 40 CFR part 86, subpart N, or 50 mg/mile for 

light-duty vehicles tested according to 40 CFR part 86, subpart B. 

(f) Repeat the procedures in §1065.590(f) through (i) to determine post-test mass of the sample 

media (e.g., filters). 

(g) Subtract each buoyancy-corrected tare mass of the sample medium (e.g., filter) from its 

respective buoyancy-corrected mass. The result is the net PM mass, mPM. Use mPM in emission 

calculations in §1065.650. 
Subpart G—Calculations and Data Requirements 

§1065.601 Overview. 

(a) This subpart describes how to– 

(1) Use the signals recorded before, during, and after an emission test to calculate brake-specific 

emissions of each regulated pollutant. 

(2) Perform calculations for calibrations and performance checks. 

(3) Determine statistical values. 

(b) You may use data from multiple systems to calculate test results for a single emission test, 

consistent with good engineering judgment. You may also make multiple measurements from a 

single batch sample, such as multiple weighings of a PM filter or multiple readings from a bag 

sample. You may not use test results from multiple emission tests to report emissions. We allow 

weighted means where appropriate. You may discard statistical outliers, but you must report all 

results. 

(c) You may use any of the following calculations instead of the calculations specified in this 

subpart G: 

(1) Mass-based emission calculations prescribed by the International Organization for 

Standardization (ISO), according to ISO 8178, except the following: 

(i) ISO 8178-1 Section 14.4, NOx Correction for Humidity and Temperature. See §1065.670 for 

approved methods for humidity corrections. 

(ii) ISO 8178-1 Section 15.1, Particulate Correction Factor for Humidity. 

(2) Other calculations that you show are equivalent to within ±0.1 % of the brake-specific 

emission results determined using the calculations specified in this subpart G. 

§1065.602 Statistics. 

(a) Overview. This section contains equations and example calculations for statistics that are 

specified in this part. In this section we use the letter "y" to denote a generic measured quantity, 

the superscript over-bar “– ” to denote an arithmetic mean, and the subscript "ref" to denote the 

reference quantity being measured. 

(b) Arithmetic mean. Calculate an arithmetic mean, , as follows: 

i

i 1

N

y

y N

 



Eq. 1065.602-1 

Example:

N = 3 

y1 = 10.60 

y2 = 11.91 

yN = y3 = 11.09 

10.60 11.91 11.09

3 y

  

y
y = 11.20 

(c) Standard deviation. Calculate the standard deviation for a non-biased (e.g., N-1) sample, , 

as follows: 

 

 

2

i

i 1

y 1

N

y y

N  



 



Eq. 1065.602-2 

Example:

N = 3 

y1 = 10.60 

y2 = 11.91 

yN = y3 = 11.09 

y = 11.20 

    22 2

y

10.60 11.2 11.91 11.2 11.09 11.2

2   

y= 0.6619 

(d) Root mean square. Calculate a root mean square, rmsy, as follows: 

2

y i

i 1

1 N

rms y N  

Eq. 1065.602-3 

Example:

N = 3 

y1 = 10.60 

y2 = 11.91 

yN = y3 = 11.09 

22 2

y

10.60 11.91 11.09

3 rms   

rmsy= 11.21 

(e) Accuracy. Determine accuracy as described in this paragraph (e).. Make multiple 

measurements of a standard quantity to create a set of observed values, yi, and compare each 

observed value to the known value of the standard quantity. The standard quantity may have a 

single known value, such as a gas standard, or a set of known values of negligible range, such as 

a known applied pressure produced by a calibration device during repeated applications. The 

known value of the standard quantity is represented by i ref y . If you use a standard quantity with a 

single value, i ref y would be constant. Calculate an accuracy value as follows: 

 i i ref

i 1

1 N

accuracy y y N   


Eq. 1065.602-4 

Example:

yref = 1800.0 

N = 3 

1 y = 1806.4 

2 y = 1803.1 

3 y = 1798.9 

( ) ( )( )( ) 1 1806.4 1800.0 1803.1 1800.0 1798.9 1800.0

3 accuracy = -+-+-

( ) ( )( )( ) 1 6.4 3.1 1.1

3 accuracy = + +-

accuracy = 2.8 

(f) t-test. Determine if your data passes a t-test by using the following equations and tables: 

(1) For an unpaired t-test, calculate the t statistic and its number of degrees of freedom, , 

as follows: 

2 2

ref y

ref

ref

N N

y y t   



Eq. 1065.602-5 

 

   

2 2

ref y

ref

2 2 2 2

ref ref y

ref

2

1 1

N N

N N

N N

v

 

 

 







Eq. 1065.602-6 

Example:

ref y = 1205.3 

y = 1123.8 

ref = 9.399 

y = 10.583 

Nref = 11 

N = 7 

2 2 9.399 10.583

11 7

1205.3 1123.8

t   

t = 16.63 

ref = 9.399 


y = 10.583 

Nref = 11 

N = 7 

 

   

2 2

2 2 2 2

2 9.399 10.583

11 7

9.399 11 10.583 7

11 1 7 1

v

 

 



 

v = 11.76 

(2) For a paired t-test, calculate the t statistic and its number of degrees of freedom, , as 

follows, noting that the i  are the errors (e.g., differences) between each pair of and : 

ε

N

t





 

Eq. 1065.602-7 

Example:

 = –0.12580 

N = 16

 ε = 0.04837 

0.12580 16

0.04837

t   

t = 10.403 

v = N – 1 

Example:

N = 16 

v = 16 – 1 

v = 15 

(3) Use Table 1 of this section to compare t to the tcrit values tabulated versus the number of 

degrees of freedom. If t is less than tcrit, then t passes the t-test. The Microsoft Excel software 

has a TINV function that returns results equivalent results and may be used in place of Table 1, 

which follows: 



refi y i y
Table 1 of §1065.602– 

Critical t values versus number of degrees of freedom, 

1

 Confidence 

90% 95% 

1 6.314 12.706 

2 2.920 4.303 

3 2.353 3.182 

4 2.132 2.776 

5 2.015 2.571 

6 1.943 2.447 

7 1.895 2.365 

8 1.860 2.306 

9 1.833 2.262 

10 1.812 2.228 

11 1.796 2.201 

12 1.782 2.179 

13 1.771 2.160 

14 1.761 2.145 

15 1.753 2.131 

16 1.746 2.120 

18 1.734 2.101 

20 1.725 2.086 

22 1.717 2.074 

24 1.711 2.064 

26 1.706 2.056 

28 1.701 2.048 

30 1.697 2.042 

35 1.690 2.030 

40 1.684 2.021 

50 1.676 2.009 

70 1.667 1.994 

100 1.660 1.984 

1000+ 1.645 1.960 

1

 Use linear interpolation to 

establish values not shown here. 

(g) F-test. Calculate the F statistic as follows: 

2

y

y 2

ref

F 

 

Eq. 1065.602-8 
Example:

 

 

2

i

i 1

y 10.583

1

N

y y

N  



  



 

 

ref 2

refi ref

i 1

ref

ref

9.399

1

N

y y

N  



  



2

2

10.583

9.399

F 

F = 1.268 

(1) For a 90 % confidence F-test, use Table 2 of this section to compare F to the Fcrit90 values 

tabulated versus (N-1) and (Nref -1). If F is less than Fcrit90, then F passes the F-test at 90 % 

confidence. 

(2) For a 95 % confidence F-test, use Table 3 of this section to compare F to the Fcrit95 values 

tabulated versus (N-1) and (Nref -1). If F is less than Fcrit95, then F passes the F-test at 95 % 

confidence.

Table 2 of §1065.602–Critical F values, Fcrit90, versus N-1 and Nref -1 at 90 % confidence 

N-1 1 2 3 4 5 6 7 8 9 10 12 15 20 24 30 40 60 120 1000+ 

Nref-1 

1 39.86 49.50 53.59 55.83 57.24 58.20 58.90 59.43 59.85 60.19 60.70 61.22 61.74 62.00 62.26 62.52 62.79 63.06 63.32 2 8.526 9.000 9.162 9.243 9.293 9.326 9.349 9.367 9.381 9.392 9.408 9.425 9.441 9.450 9.458 9.466 9.475 9.483 9.491 3 5.538 5.462 5.391 5.343 5.309 5.285 5.266 5.252 5.240 5.230 5.216 5.200 5.184 5.176 5.168 5.160 5.151 5.143 5.134 4 4.545 4.325 4.191 4.107 4.051 4.010 3.979 3.955 3.936 3.920 3.896 3.870 3.844 3.831 3.817 3.804 3.790 3.775 3.761 5 4.060 3.780 3.619 3.520 3.453 3.405 3.368 3.339 3.316 3.297 3.268 3.238 3.207 3.191 3.174 3.157 3.140 3.123 3.105 6 3.776 3.463 3.289 3.181 3.108 3.055 3.014 2.983 2.958 2.937 2.905 2.871 2.836 2.818 2.800 2.781 2.762 2.742 2.722 7 3.589 3.257 3.074 2.961 2.883 2.827 2.785 2.752 2.725 2.703 2.668 2.632 2.595 2.575 2.555 2.535 2.514 2.493 2.471 8 3.458 3.113 2.924 2.806 2.726 2.668 2.624 2.589 2.561 2.538 2.502 2.464 2.425 2.404 2.383 2.361 2.339 2.316 2.293 9 3.360 3.006 2.813 2.693 2.611 2.551 2.505 2.469 2.440 2.416 2.379 2.340 2.298 2.277 2.255 2.232 2.208 2.184 2.159 

10 3.285 2.924 2.728 2.605 2.522 2.461 2.414 2.377 2.347 2.323 2.284 2.244 2.201 2.178 2.155 2.132 2.107 2.082 2.055 11 3.225 2.860 2.660 2.536 2.451 2.389 2.342 2.304 2.274 2.248 2.209 2.167 2.123 2.100 2.076 2.052 2.026 2.000 1.972 12 3.177 2.807 2.606 2.480 2.394 2.331 2.283 2.245 2.214 2.188 2.147 2.105 2.060 2.036 2.011 1.986 1.960 1.932 1.904 13 3.136 2.763 2.560 2.434 2.347 2.283 2.234 2.195 2.164 2.138 2.097 2.053 2.007 1.983 1.958 1.931 1.904 1.876 1.846 14 3.102 2.726 2.522 2.395 2.307 2.243 2.193 2.154 2.122 2.095 2.054 2.010 1.962 1.938 1.912 1.885 1.857 1.828 1.797 15 3.073 2.695 2.490 2.361 2.273 2.208 2.158 2.119 2.086 2.059 2.017 1.972 1.924 1.899 1.873 1.845 1.817 1.787 1.755 16 3.048 2.668 2.462 2.333 2.244 2.178 2.128 2.088 2.055 2.028 1.985 1.940 1.891 1.866 1.839 1.811 1.782 1.751 1.718 17 3.026 2.645 2.437 2.308 2.218 2.152 2.102 2.061 2.028 2.001 1.958 1.912 1.862 1.836 1.809 1.781 1.751 1.719 1.686 18 3.007 2.624 2.416 2.286 2.196 2.130 2.079 2.038 2.005 1.977 1.933 1.887 1.837 1.810 1.783 1.754 1.723 1.691 1.657 19 2.990 2.606 2.397 2.266 2.176 2.109 2.058 2.017 1.984 1.956 1.912 1.865 1.814 1.787 1.759 1.730 1.699 1.666 1.631 20 2.975 2.589 2.380 2.249 2.158 2.091 2.040 1.999 1.965 1.937 1.892 1.845 1.794 1.767 1.738 1.708 1.677 1.643 1.607 21 2.961 2.575 2.365 2.233 2.142 2.075 2.023 1.982 1.948 1.920 1.875 1.827 1.776 1.748 1.719 1.689 1.657 1.623 1.586 20 2.949 2.561 2.351 2.219 2.128 2.061 2.008 1.967 1.933 1.904 1.859 1.811 1.759 1.731 1.702 1.671 1.639 1.604 1.567 23 2.937 2.549 2.339 2.207 2.115 2.047 1.995 1.953 1.919 1.890 1.845 1.796 1.744 1.716 1.686 1.655 1.622 1.587 1.549 24 2.927 2.538 2.327 2.195 2.103 2.035 1.983 1.941 1.906 1.877 1.832 1.783 1.730 1.702 1.672 1.641 1.607 1.571 1.533 25 2.918 2.528 2.317 2.184 2.092 2.024 1.971 1.929 1.895 1.866 1.820 1.771 1.718 1.689 1.659 1.627 1.593 1.557 1.518 26 2.909 2.519 2.307 2.174 2.082 2.014 1.961 1.919 1.884 1.855 1.809 1.760 1.706 1.677 1.647 1.615 1.581 1.544 1.504 27 2.901 2.511 2.299 2.165 2.073 2.005 1.952 1.909 1.874 1.845 1.799 1.749 1.695 1.666 1.636 1.603 1.569 1.531 1.491 28 2.894 2.503 2.291 2.157 2.064 1.996 1.943 1.900 1.865 1.836 1.790 1.740 1.685 1.656 1.625 1.593 1.558 1.520 1.478 29 2.887 2.495 2.283 2.149 2.057 1.988 1.935 1.892 1.857 1.827 1.781 1.731 1.676 1.647 1.616 1.583 1.547 1.509 1.467 30 2.881 2.489 2.276 2.142 2.049 1.980 1.927 1.884 1.849 1.819 1.773 1.722 1.667 1.638 1.606 1.573 1.538 1.499 1.456 40 2.835 2.440 2.226 2.091 1.997 1.927 1.873 1.829 1.793 1.763 1.715 1.662 1.605 1.574 1.541 1.506 1.467 1.425 1.377 60 2.791 2.393 2.177 2.041 1.946 1.875 1.819 1.775 1.738 1.707 1.657 1.603 1.543 1.511 1.476 1.437 1.395 1.348 1.291 

120 2.748 2.347 2.130 1.992 1.896 1.824 1.767 1.722 1.684 1.652 1.601 1.545 1.482 1.447 1.409 1.368 1.320 1.265 1.193 

1000+ 2.706 2.303 2.084 1.945 1.847 1.774 1.717 1.670 1.632 1.599 1.546 1.487 1.421 1.383 1.342 1.295 1.240 1.169 1.000 
Table 3 of §1065.602–Critical F values, Fcrit95, versus N-1 and Nref-1 at 95 % confidence 

N-1 1 2 3 4 5 6 7 8 9 10 12 15 20 24 30 40 60 120 1000+ 

Nref-1 

1 161.4 199.5 215.7 224.5 230.1 233.9 236.7 238.8 240.5 241.8 243.9 245.9 248.0 249.0 250.1 251.1 252.2 253.2 254.3 2 18.51 19.00 19.16 19.24 19.29 19.33 19.35 19.37 19.38 19.39 19.41 19.42 19.44 19.45 19.46 19.47 19.47 19.48 19.49 3 10.12 9.552 9.277 9.117 9.014 8.941 8.887 8.845 8.812 8.786 8.745 8.703 8.660 8.639 8.617 8.594 8.572 8.549 8.526 4 7.709 6.944 6.591 6.388 6.256 6.163 6.094 6.041 5.999 5.964 5.912 5.858 5.803 5.774 5.746 5.717 5.688 5.658 5.628 5 6.608 5.786 5.410 5.192 5.050 4.950 4.876 4.818 4.773 4.735 4.678 4.619 4.558 4.527 4.496 4.464 4.431 4.399 4.365 6 5.987 5.143 4.757 4.534 4.387 4.284 4.207 4.147 4.099 4.060 4.000 3.938 3.874 3.842 3.808 3.774 3.740 3.705 3.669 7 5.591 4.737 4.347 4.120 3.972 3.866 3.787 3.726 3.677 3.637 3.575 3.511 3.445 3.411 3.376 3.340 3.304 3.267 3.230 8 5.318 4.459 4.066 3.838 3.688 3.581 3.501 3.438 3.388 3.347 3.284 3.218 3.150 3.115 3.079 3.043 3.005 2.967 2.928 9 5.117 4.257 3.863 3.633 3.482 3.374 3.293 3.230 3.179 3.137 3.073 3.006 2.937 2.901 2.864 2.826 2.787 2.748 2.707 

10 4.965 4.103 3.708 3.478 3.326 3.217 3.136 3.072 3.020 2.978 2.913 2.845 2.774 2.737 2.700 2.661 2.621 2.580 2.538 11 4.844 3.982 3.587 3.357 3.204 3.095 3.012 2.948 2.896 2.854 2.788 2.719 2.646 2.609 2.571 2.531 2.490 2.448 2.405 12 4.747 3.885 3.490 3.259 3.106 2.996 2.913 2.849 2.796 2.753 2.687 2.617 2.544 2.506 2.466 2.426 2.384 2.341 2.296 13 4.667 3.806 3.411 3.179 3.025 2.915 2.832 2.767 2.714 2.671 2.604 2.533 2.459 2.420 2.380 2.339 2.297 2.252 2.206 14 4.600 3.739 3.344 3.112 2.958 2.848 2.764 2.699 2.646 2.602 2.534 2.463 2.388 2.349 2.308 2.266 2.223 2.178 2.131 15 4.543 3.682 3.287 3.056 2.901 2.791 2.707 2.641 2.588 2.544 2.475 2.403 2.328 2.288 2.247 2.204 2.160 2.114 2.066 16 4.494 3.634 3.239 3.007 2.852 2.741 2.657 2.591 2.538 2.494 2.425 2.352 2.276 2.235 2.194 2.151 2.106 2.059 2.010 17 4.451 3.592 3.197 2.965 2.810 2.699 2.614 2.548 2.494 2.450 2.381 2.308 2.230 2.190 2.148 2.104 2.058 2.011 1.960 18 4.414 3.555 3.160 2.928 2.773 2.661 2.577 2.510 2.456 2.412 2.342 2.269 2.191 2.150 2.107 2.063 2.017 1.968 1.917 19 4.381 3.522 3.127 2.895 2.740 2.628 2.544 2.477 2.423 2.378 2.308 2.234 2.156 2.114 2.071 2.026 1.980 1.930 1.878 20 4.351 3.493 3.098 2.866 2.711 2.599 2.514 2.447 2.393 2.348 2.278 2.203 2.124 2.083 2.039 1.994 1.946 1.896 1.843 21 4.325 3.467 3.073 2.840 2.685 2.573 2.488 2.421 2.366 2.321 2.250 2.176 2.096 2.054 2.010 1.965 1.917 1.866 1.812 22 4.301 3.443 3.049 2.817 2.661 2.549 2.464 2.397 2.342 2.297 2.226 2.151 2.071 2.028 1.984 1.938 1.889 1.838 1.783 23 4.279 3.422 3.028 2.796 2.640 2.528 2.442 2.375 2.320 2.275 2.204 2.128 2.048 2.005 1.961 1.914 1.865 1.813 1.757 24 4.260 3.403 3.009 2.776 2.621 2.508 2.423 2.355 2.300 2.255 2.183 2.108 2.027 1.984 1.939 1.892 1.842 1.790 1.733 25 4.242 3.385 2.991 2.759 2.603 2.490 2.405 2.337 2.282 2.237 2.165 2.089 2.008 1.964 1.919 1.872 1.822 1.768 1.711 26 4.225 3.369 2.975 2.743 2.587 2.474 2.388 2.321 2.266 2.220 2.148 2.072 1.990 1.946 1.901 1.853 1.803 1.749 1.691 27 4.210 3.354 2.960 2.728 2.572 2.459 2.373 2.305 2.250 2.204 2.132 2.056 1.974 1.930 1.884 1.836 1.785 1.731 1.672 28 4.196 3.340 2.947 2.714 2.558 2.445 2.359 2.291 2.236 2.190 2.118 2.041 1.959 1.915 1.869 1.820 1.769 1.714 1.654 29 4.183 3.328 2.934 2.701 2.545 2.432 2.346 2.278 2.223 2.177 2.105 2.028 1.945 1.901 1.854 1.806 1.754 1.698 1.638 30 4.171 3.316 2.922 2.690 2.534 2.421 2.334 2.266 2.211 2.165 2.092 2.015 1.932 1.887 1.841 1.792 1.740 1.684 1.622 40 4.085 3.232 2.839 2.606 2.450 2.336 2.249 2.180 2.124 2.077 2.004 1.925 1.839 1.793 1.744 1.693 1.637 1.577 1.509 60 4.001 3.150 2.758 2.525 2.368 2.254 2.167 2.097 2.040 1.993 1.917 1.836 1.748 1.700 1.649 1.594 1.534 1.467 1.389 

120 3.920 3.072 2.680 2.447 2.290 2.175 2.087 2.016 1.959 1.911 1.834 1.751 1.659 1.608 1.554 1.495 1.429 1.352 1.254 

1000+ 3.842 2.996 2.605 2.372 2.214 2.099 2.010 1.938 1.880 1.831 1.752 1.666 1.571 1.517 1.459 1.394 1.318 1.221 1.000 
(h) Slope. Calculate a least-squares regression slope, a1y, as follows: 
  i refi ref

i 1

1y

2

refi ref

i 1

( )

( )

N

N

yy y y

a

y y





 









Eq. 1065.602-9 

Example:

N = 6000 

y1 = 2045.8 

y = 1050.1 

yref 1 = 2045.0 

ref y = 1055.3 

       

  

6000 ref6000

1y 2 2

ref6000

2045.8 1050.1 2045.0 1055.3 ... 1050.1 1055.3

2045.0 1055.3 ... 1055.3

y y a y          

a1y = 1.0110 

(i) Intercept. Calculate a least-squares regression intercept, a0y, as follows: 

a yay 0y 1y ref    

Eq. 1065.602-10 

Example:

y = 1050.1

a1y = 1.0110 

ref y = 1055.3 

a0y = 1050.1 – (1.0110 · 1055.3) 

a0y = –16.8083 

(j) Standard estimate of error. Calculate a standard estimate of error, SEE, as follows: 

2

i 0y 1y refi

i 1

y

( )

2

N

ya ay

SEE

N



       

 

Eq. 1065.602-11 

Example:

N = 6000 

y1 = 2045.8 

a0y = –16.8083 

a1y = 1.0110 

yref1= 2045.0 

 2 2

6000 ref 6000

y

2045.8 ( 16.8083) (1.0110 2045.0) ... ( 16.8083) (1.0110 )

6000 2

y y SEE

            
SEEy = 5.348 

(k) Coefficient of determination. Calculate a coefficient of determination, , as follows: 

 

2

i 0y 1y refi

2 i 1

y 2

i

i 1

( )

1

N

N

ya ay

r

y y





       







Eq. 1065.602-12 

Example:

N = 6000 

y1 = 2045.8 

a0y = –16.8083 

a1y = 1.0110 

yref1 = 2045.0 

y = 1480.5 

 

 

2 2

2 6000 ref6000

y 2 2

6000

2045.8 ( 16.8083) (1.0110 2045.0) ... ( 16.8083) (1.0110 ) 1

2045.8 1480.5 ... 1480.5

y y r

y

            

     

2

yr = 0.9859 

(l) Flow-weighted mean concentration. In some sections of this part, you may need to calculate a 

flow-weighted mean concentration to determine the applicability of certain provisions. A flowweighted mean is the mean of a quantity after it is weighted proportional to a corresponding flow 

rate. For example, if a gas concentration is measured continuously from the raw exhaust of an 

engine, its flow-weighted mean concentration is the sum of the products of each recorded 

concentration times its respective exhaust molar flow rate, divided by the sum of the recorded 

flow rate values. As another example, the bag concentration from a CVS system is the same as 

the flow-weighted mean concentration because the CVS system itself flow-weights the bag 

concentration. You might already expect a certain flow-weighted mean concentration of an 

emission at its standard based on previous testing with similar engines or testing with similar 

equipment and instruments. If you need to estimate your expected flow-weighted mean 

concentration of an emission at its standard, we recommend using the following examples as a 

guide for how to estimate the flow-weighted mean concentration expected at the standard. Note 

that these examples are not exact and that they contain assumptions that are not always valid. 

Use good engineering judgment to determine if you can use similar assumptions. 

(1) To estimate the flow-weighted mean raw exhaust NOx concentration from a turbocharged 

heavy-duty compression-ignition engine at a NOx standard of 2.5 g/(kW·hr), you may do the 

following: 

(i) Based on your engine design, approximate a map of maximum torque versus speed and use it 

with the applicable normalized duty cycle in the standard-setting part to generate a reference 

duty cycle as described in §1065.610. Calculate the total reference work, Wref, as described in 

§1065.650. Divide the reference work by the duty cycle’s time interval, tdutycycle, to determine 

mean reference power, Pref . 

(ii) Based on your engine design, estimate maximum power, Pmax, the design speed at maximum 

power, fnmax, the design maximum intake manifold boost pressure, pinmax, and temperature, Tinmax. 

2 r
Also, estimate a mean fraction of power that is lost due to friction and pumping, Pfrict . Use this 

information along with the engine displacement volume, Vdisp, an approximate volumetric 

efficiency, V, and the number of engine strokes per power stroke (2-stroke or four-stroke), 

Nstroke, to estimate the maximum raw exhaust molar flow rate, exhmax n . 

(iii) Use your estimated values as described in the following example calculation: 

  std ref

exp

ref frict max

exhmax duty cycle

max

e W x P PP

Mn t

P

     

   

 



Eq. 1065.602-13 

max disp nmax V

stroke

exhmax

max

2 pV f N n R T

  

  

Eq. 1065.602-14 

Example:

eNOx = 2.5 g/(kW·hr) 

Wref = 11.883 kW·hr 

MNOx = 46.0055 g/mol = 46.0055·10-6 g/mol 

tdutycycle = 20 min = 1200 s 

Pref = 35.65 kW 

Pfrict = 15 % 

Pmax = 125 kW 

pmax = 300 kPa = 300000 Pa 

Vdisp = 3.0 l = 0.0030 m3/r 

fnmax = 2800 r/min = 46.67 r/s 

Nstroke = 4 

V= 0.9 

R = 8.314472 J/(mol·K) 

Tmax = 348.15 K 

exhmax

2 300000 0.0030 46.67 0.9

4

8.314472 348.15 n

  

  

exhmax n = 6.53 mol/s 

  exp

6

2.5 11.883

35.65 0.15 125

46.0055 10 6.53 1200

125

x



          

Deleted: 4-
exp x = 189.4 μmol/mol 

(2) To estimate the flow-weighted mean NMHC concentration in a CVS from a naturally 

aspirated nonroad spark-ignition engine at an NMHC standard of 0.5 g/(kW·hr), you may do the 

following: 

(i) Based on your engine design, approximate a map of maximum torque versus speed and use it 

with the applicable normalized duty cycle in the standard-setting part to generate a reference 

duty cycle as described in §1065.610. Calculate the total reference work, Wref, as described in 

§1065.650. 

(ii) Multiply your CVS total molar flow rate by the time interval of the duty cycle, tdutycycle. The 

result is the total diluted exhaust flow of the ndexh. 

(iii) Use your estimated values as described in the following example calculation: 

std ref

NMHC

dexh duty cycle

e W x Mn t

    

Eq. 1065.602-15 

Example:

eNMHC = 1.5 g/(kW·hr) 

Wref = 5.389 kW·hr 

MNMHC = 13.875389 g/mol = 13.875389·10-6 g/mol 

dexh n = 6.021 mol/s 

tdutycycle= 30 min = 1800 s 

NMHC -6

1.5 5.389

13.875389 10 6.021 1800 x    

NMHC x = 53.8 μmol/mol 

§1065.610 Duty cycle generation. 

This section describes how to generate duty cycles that are specific to your engine, based on the 

normalized duty cycles in the standard-setting part. During an emission test, use a duty cycle 

that is specific to your engine to command engine speed, torque, and power, as applicable, using 

an engine dynamometer and an engine operator demand. Paragraph (a) of this section describes 

how to “normalize” your engine’s map to determine the maximum test speed and torque for your 

engine. The rest of this section describes how to use these values to “denormalize” the duty 

cycles in the standard-setting parts, which are all published on a normalized basis. Thus, the 

term "normalized" in paragraph (a) of this section refers to different values than it does in the rest 

of the section. 

(a) Maximum test speed, fntest. This section generally applies to duty cycles for variable-speed 

engines. For constant-speed engines subject to duty cycles that specify normalized speed 

commands, use the no-load governed speed as the measured fntest. This is the highest engine 

speed where an engine outputs zero torque. For variable-speed engines, determine the measured 

fntest from the power-versus-speed map, generated according to §1065.510, as follows: 

(1) Based on the map, determine maximum power, Pmax, and the speed at which maximum 

power occurred, fnPmax. If maximum power occurs at multiple speeds, take fnPmax as the lowest of 

these speeds. Divide every recorded power by Pmax and divide every recorded speed by fnPmax. 
The result is a normalized power-versus-speed map. Your measured fntest is the speed at which 

the sum of the squares of normalized speed and power is maximum. Note that if multiple 

maximum values are found, fntest should be taken as the lowest speed of all points with the same 

maximum sum of squares. Determine fntest as follows: 

  2 2

ntest ni nnormi normi ff f P   at the maximum of 

Eq. 1065.610-1 

Where: 

fntest = maximum test speed. 

i = an indexing variable that represents one recorded value of an engine map. 

fnnormi = an engine speed normalized by dividing it by fnPmax. 

Pnormi = an engine power normalized by dividing it by Pmax. 

Example:

(fnnorm1 = 1.002, Pnorm1 = 0.978, fn1 = 2359.71) 

(fnnorm2 = 1.004, Pnorm2 = 0.977, fn2 = 2364.42) 

(fnnorm3 = 1.006, Pnorm3 = 0.974, fn3 = 2369.13) 

(fnnorm12

 + Pnorm12) = (1.0022 + 0.9782) = 1.960 

(fnnorm22

 + Pnorm22) = (1.0042 + 0.9772) = 1.963 

(fnnorm32

 + Pnorm32) = (1.0062 + 0.9742) = 1.961 

maximum = 1.963 at i = 2 

fntest = 2364.42 r/min 

(2) For engines with a high-speed governor that will be subject to a reference duty cycle that 

specifies normalized speeds greater than 100 %, calculate an alternate maximum test speed, 

fntest,alt, as specified in this paragraph (a)(2). If fntest,alt is less than the measured maximum test 

speed, fntest, determined in paragraph (a)(1) of this section, replace fntest with fntest,alt. In this case, 

fntest,alt becomes the “maximum test speed” for that engine. Note that §1065.510 allows you to 

apply an optional declared maximum test speed to the final measured maximum test speed 

determined as an outcome of the comparison between fntest, and fntest,alt in this paragraph (a)(2). 

Determine fntest,alt as follows: 

fntest,alt = (fnhi,idle – fnidle)/% speedmax + fnidle

Eq. 1065.610-2 

Where: 

fntest,alt = alternate maximum test speed 

fnhi,idle = warm high-idle speed 

fnidle = warm idle speed 

% speedmax = maximum normalized speed from duty cycle 

Example: 

fnhi,idle = 2200 r/min 

fnidle = 800 r/min 

% speedmax = 105 % (Nonroad CI Transient Cycle) 

fntest,alt = (2200 – 800)/105 % + 800 

fntest,alt = 2133 r/min 
(3) For variable-speed engines, transform normalized speeds to reference speeds according to 

paragraph (c) of this section by using the measured maximum test speed determined according to 

paragraphs (a)(1) and (2) of this section—or use your declared maximum test speed, as allowed 

in §1065.510. 

(4) For constant-speed engines, transform normalized speeds to reference speeds according to 

paragraph (c) of this section by using the measured no-load governed speed—or use your 

declared maximum test speed, as allowed in §1065.510 

(b) Maximum test torque, Ttest. For constant-speed engines, determine the measured Ttest from 

the power-versus-speed map, generated according to §1065.510, as follows: 

(1) Based on the map, determine maximum power, Pmax, and the speed at which maximum 

power occurs, fnPmax. If maximum power occurs at multiple speeds, take fnPmax as the lowest of 

these speeds. Divide every recorded power by Pmax and divide every recorded speed by fnPmax. 

The result is a normalized power-versus-speed map. Your measured Ttest is the torque at which 

the sum of the squares of normalized speed and power is maximum. Note that that if multiple 

maximum values are found, Ttest should be taken as the highest torque of all points with the same 

maximum sum of squares. Determine Ttest as follows: 

  2 2

test i nnormi normi TT f P   at the maximum of 

Eq. 1065.610-3 

Where: 

Ttest = maximum test torque. 

Example:

(fnnorm1 = 1.002, Pnorm1 = 0.978, T1 = 722.62 N·m)

(fnnorm2 = 1.004, Pnorm2 = 0.977, T2 = 720.44 N·m)

(fnnorm3 = 1.006, Pnorm3 = 0.974, T3 = 716.80 N·m)

(fnnorm12

 + Pnorm12) = (1.0022 + 0.9782) = 1.960 

(fnnorm12

 + Pnorm12) = (1.0042 + 0.9772) = 1.963 

(fnnorm12

 + Pnorm12) = (1.0062 + 0.9742) = 1.961 

maximum = 1.963 at i = 2 

Ttest = 720.44 N·m 

(2) Transform normalized torques to reference torques according to paragraph (d) of this section 

by using the measured maximum test torque determined according to paragraph (b)(1) of this 

section—or use your declared maximum test torque, as allowed in §1065.510. 

(c) Generating reference speed values from normalized duty cycle speeds. Transform 

normalized speed values to reference values as follows: 

(1) % speed. If your normalized duty cycle specifies % speed values, use your warm idle speed 

and your maximum test speed to transform the duty cycle, as follows: 

fnref = % speed · (fntest – fnidle) + fnidle

Eq. 1065.610-4 

Example:

% speed = 85 % 

fntest = 2364 r/min 

fnidle = 650 r/min 
fnref = 85 % · (2364 – 650 ) + 650 

fnref = 2107 r/min 

(2) A, B, and C speeds. If your normalized duty cycle specifies speeds as A, B, or C values, use 

your power-versus-speed curve to determine the lowest speed below maximum power at which 

50 % of maximum power occurs. Denote this value as nlo. Take nlo to be warm idle speed if all 

power points at speeds below the maximum power speed are higher than 50 % of maximum 

power. Also determine the highest speed above maximum power at which 70 % of maximum 

power occurs. Denote this value as nhi. If all power points at speeds above the maximum power 

speed are higher than 70% of maximum power, take nhi to be the declared maximum safe engine 

speed or the declared maximum representative engine speed, whichever is lower. Use nhi and nlo

to calculate reference values for A, B, or C speeds as follows: 

fnrefA = 0.25 · (nhi – nlo) + nlo

Eq. 1065.610-5 

fnrefB = 0.50 · (nhi – nlo) + nlo

Eq. 1065.610-6 

fnrefC = 0.75 · (nhi – nlo) + nlo

Eq. 1065.610-7 

Example:

nlo = 1005 r/min 

nhi = 2385 r/min 

fnrefA = 0.25 · (2385 – 1005) + 1005 

fnrefB = 0.50 · (2385 – 1005) + 1005 

fnrefC = 0.75 · (2385 – 1005) + 1005 

fnrefA = 1350 r/min 

fnrefB = 1695 r/min 

fnrefC = 2040 r/min 

(3) Intermediate speed. If your normalized duty cycle specifies a speed as “intermediate speed,” 

use your torque-versus-speed curve to determine the speed at which maximum torque occurs. 

This is peak torque speed. If maximum torque occurs in a flat region of the torque-versus-speed 

curve, your peak torque speed is the midpoint between the lowest and highest speeds at which 

the trace reaches the flat region. For purposes of this paragraph (c)(3), a flat region is one in 

which measured torque values are within 2 % of the maximum recorded value. Identify your 

reference intermediate speed as one of the following values: 

(i) Peak torque speed if it is between (60 and 75) % of maximum test speed.

(ii) 60 % of maximum test speed if peak torque speed is less than 60 % of maximum test speed.

(iii) 75 % of maximum test speed if peak torque speed is greater than 75 % of maximum test 

speed.

(d) Generating reference torques from normalized duty-cycle torques. Transform normalized 

torques to reference torques using your map of maximum torque versus speed. 

(1) Reference torque for variable-speed engines. For a given speed point, multiply the 

corresponding % torque by the maximum torque at that speed, according to your map. If your 

engine is subject to a reference duty cycle that specifies negative torque values (i.e., engine 

motoring), use negative torque for those motoring points (i.e., the motoring torque). If you map 

negative torque as allowed under §1065.510(c)(2) and the low-speed governor activates, 

resulting in positive torques, you may replace those positive motoring mapped torques with 

negative values between zero and the largest negative motoring torque. For both maximum and 
motoring torque maps, linearly interpolate mapped torque values to determine torque between 

mapped speeds. If the reference speed is below the minimum mapped speed (i.e., 95% of idle 

speed or 95% of lowest required speed, whichever is higher), use the mapped torque at the 

minimum mapped speed as the reference torque. The result is the reference torque for each 

speed point. 

(2) Reference torque for constant-speed engines. Multiply a % torque value by your maximum 

test torque. The result is the reference torque for each point. 

(3) Required deviations. We require the following deviations for variable-speed engines 

intended primarily for propulsion of a vehicle with an automatic transmission where that engine 

is subject to a transient duty cycle with idle operation. These deviations are intended to produce 

a more representative transient duty cycle for these applications. For steady-state duty cycles or 

transient duty cycles with no idle operation, these requirements do not apply. Idle points for 

steady state duty cycles of such engines are to be run at conditions simulating neutral or park on 

the transmission. 

(i) Zero-percent speed is the warm idle speed measured according to §1065.510(b)(6) with CITT 

applied, i.e., measured warm idle speed in drive. 

(ii) If the cycle begins with a set of contiguous idle points (zero-percent speed, and zero-percent 

torque), leave the reference torques set to zero for this initial contiguous idle segment. This is to 

represent free idle operation with the transmission in neutral or park at the start of the transient 

duty cycle, after the engine is started. If the initial idle segment is longer than 24 s, change the 

reference torques for the remaining idle points in the initial contiguous idle segment to CITT 

(i.e., change idle points corresponding to 25 s to the end of the initial idle segment to CITT). 

This is to represent shifting the transmission to drive. 

(iii) For all other idle points, change the reference torque to CITT. This is to represent the 

transmission operating in drive. 

(iv) If the engine is intended primarily for automatic transmissions with a Neutral-WhenStationary feature that automatically shifts the transmission to neutral after the vehicle is stopped 

for a designated time and automatically shifts back to drive when the operator increases demand 

(i.e., pushes the accelerator pedal), change the reference torque back to zero for idle points in 

drive after the designated time. 

(v) For all points with normalized speed at or below zero percent and reference torque from zero 

to CITT, set the reference torque to CITT. This is to provide smoother torque references below 

idle speed. 

(vi) For motoring points, make no changes. 

(vii) For consecutive points with reference torques from zero to CITT that immediately follow 

idle points, change their reference torques to CITT. This is to provide smooth torque transition 

out of idle operation. This does not apply if the Neutral-When-Stationary feature is used and the 

transmission has shifted to neutral. 

(viii) For consecutive points with reference torque from zero to CITT that immediately precede 

idle points, change their reference torques to CITT. This is to provide smooth torque transition 

into idle operation. 

(4) Permissible deviations for any engine. If your engine does not operate below a certain 

minimum torque under normal in-use conditions, you may use a declared minimum torque as the 

reference value instead of any value denormalized to be less than the declared value. For 

example, if your engine is connected to a hydrostatic transmission and it has a minimum torque 

even when all the driven hydraulic actuators and motors are stationary and the engine is at idle, 
then you may use this declared minimum torque as a reference torque value instead of any 

reference torque value generated under paragraph (d)(1) or (2) of this section that is between 

zero and this declared minimum torque. 

(e) Generating reference power values from normalized duty cycle powers. Transform 

normalized power values to reference speed and power values using your map of maximum 

power versus speed. 

(1) First transform normalized speed values into reference speed values. For a given speed point, 

multiply the corresponding % power by the mapped power at maximum test speed, fntest, unless 

specified otherwise by the standard-setting part. The result is the reference power for each speed 

point, Pref. Convert these reference powers to corresponding torques for operator demand and 

dynamometer control and for duty cycle validation per 1065.514. Use the reference speed 

associated with each reference power point for this conversion. As with cycles specified with % 

torque, linearly interpolate between these reference torque values generated from cycles with % 

power. 

(2) Permissible deviations for any engine. If your engine does not operate below a certain power 

under normal in-use conditions, you may use a declared minimum power as the reference value 

instead of any value denormalized to be less than the declared value. For example, if your 

engine is directly connected to a propeller, it may have a minimum power called idle power. In 

this case, you may use this declared minimum power as a reference power value instead of any 

reference power value generated per paragraph (e)(1) of this section that is from zero to this 

declared minimum power. 

§1065.630 1980 international gravity formula. 

The acceleration of Earth's gravity, ag, varies depending on your location. Calculate ag at your 

latitude, as follows: 

ag = 9.7803267715 · [1 + 5.2790414 · 10-3·sin2 () + 2.32718 · 10-5·sin4 () 

+ 1.262 · 10-7·sin6

 () + 7 · 10-10·sin8 ()] 

Eq. 1065.630-1 

Where: 

 = Degrees north or south latitude. 

Example:

 = 45 ° 

ag = 9.7803267715 · (1 + 5.2790414 · 10-3·sin2 (45) + 2.32718 · 10-5·sin4 (45) 

+ 1.262 · 10-7·sin6

 (45) + 7 · 10-10·sin8 (45) 

ag = 9.8061992026 m/s2

§1065.640 Flow meter calibration calculations. 

This section describes the calculations for calibrating various flow meters. After you calibrate a 

flow meter using these calculations, use the calculations described in §1065.642 to calculate flow 

during an emission test. Paragraph (a) of this section first describes how to convert reference 

flow meter outputs for use in the calibration equations, which are presented on a molar basis. The 

remaining paragraphs describe the calibration calculations that are specific to certain types of 

flow meters. 

(a) Reference meter conversions. The calibration equations in this section use molar flow rate, 

ref n , as a reference quantity. If your reference meter outputs a flow rate in a different quantity, 

such as standard volume rate, Vstdref

 , actual volume rate, Vactref , or mass rate,mref  , convert your 

Deleted: 9.8178291229

Comment [CAL2]: Convert all Pa to kPa in 640, 

642, 644, etc. for FRM. Also look at converting kg 

to g. 
reference meter output to a molar flow rate using the following equations, noting that while 

values for volume rate, mass rate, pressure, temperature, and molar mass may change during an 

emission test, you should ensure that they are as constant as practical for each individual set 

point during a flow meter calibration: 

stdref std actref act ref

ref

std act mix

V pV p m n TR TR M    

   

Eq. 1065.640-1 

Where: 

ref n = reference molar flow rate. 

 Vstdref = reference volume flow rate, corrected to a standard pressure and a standard temperature. 

 Vactref = reference volume flow rate at the actual pressure and temperature of the flow rate. 

mref  = reference mass flow. 

pstd = standard pressure. 

pact = actual pressure of the flow rate. 

Tstd = standard temperature. 

Tact = actual temperature of the flow rate. 

R = molar gas constant. 

Mmix = molar mass of the flow rate. 

Example 1:

Vstdref

 = 1000.00 ft3

/min = 0.471948 m3/s 

pstd = 29.9213 in Hg @ 32 °F = 101325 Pa 

Tstd = 68.0 °F = 293.15 K 

R = 8.314472 J/(mol·K) 

ref

0.471948 101325

293.15 8.314472 n    

ref n = 19.619 mol/s 

Example 2: 

mref  = 17.2683 kg/min = 287.805 g/s 

Mmix = 28.7805 g/mol 

ref

287.805

28.7805 n 

ref n = 10.0000 mol/s

(b) PDP calibration calculations. For each restrictor position, calculate the following values from 

Comment [CAL3]: Corrected typo in equation. 

Deleted: Pstd

Deleted: Pact

Deleted: P
the mean values determined in §1065.340, as follows: 

(1) PDP volume pumped per revolution, Vrev (m3

/r): 

ref in

rev

in nPDP

n RT V

p f

   



Eq. 1065.640-2 

Example:

ref n = 25.096 mol/s 

R = 8.314472 J/(mol·K) 

Tin = 299.5 K 

in p = 98290 Pa 

nPDP f = 1205.1 r/min = 20.085 r/s 

25.096 8.314472 299.5

98290 20.085

Vrev

   

Vrev = 0.03166 m3/r 

(2) PDP slip correction factor, Ks (s/r): 

out in

s

nPDP out

1 p p K

f p

  

Eq. 1065.640-3 

Example:

nPDP f = 1205.1 r/min = 20.085 r/s 

out p = 100.103 kPa 

in p = 98.290 kPa 

s

1 100.103 98.290

20.085 100.103

K   

Ks = 0.006700 s/r 

(3) Perform a least-squares regression of PDP volume pumped per revolution, Vrev, versus PDP 

slip correction factor, Ks, by calculating slope, a1, and intercept, a0, as described in §1065.602. 

(4) Repeat the procedure in paragraphs (b)(1) through (3) of this section for every speed that you 

run your PDP. 

(5) The following example illustrates these calculations: 

Table 1 of §1065.640– 

Example of PDP calibration data 

nPDP f

(r/min) 

a1 

(m3

/min)

a0 

(m3

/r)

Comment [CAL4]: Corrected typo in equation. 

Comment [CAL5]: Corrected typo. 

Comment [CAL6]: Corrected typo. 

Comment [CAL7]: Corrected typo. 
755.0 50.43 0.056 

987.6 49.86 -0.013 

1254.5 48.54 0.028 

1401.3 47.30 -0.061 

(6) For each speed at which you operate the PDP, use the corresponding slope, a1, and intercept, 

a0, to calculate flow rate during emission testing as described in §1065.642. 

(c) Venturi governing equations and permissible assumptions. This section describes the 

governing equations and permissible assumptions for calibrating a venturi and calculating flow 

using a venturi. Because a subsonic venturi (SSV) and a critical-flow venturi (CFV) both 

operate similarly, their governing equations are nearly the same, except for the equation 

describing their pressure ratio, r (i.e., rSSV versus rCFV). These governing equations assume onedimensional isentropic inviscid compressible flow of an ideal gas. In paragraph (c)(4) of this 

section, we describe other assumptions that you may make, depending upon how you conduct 

your emission tests. If we do not allow you to assume that the measured flow is an ideal gas, the 

governing equations include a first-order correction for the behavior of a real gas; namely, the 

compressibility factor, Z. If good engineering judgment dictates using a value other than Z=1, 

you may either use an appropriate equation of state to determine values of Z as a function of 

measured pressures and temperatures, or you may develop your own calibration equations based 

on good engineering judgment. Note that the equation for the flow coefficient, Cf, is based on 

the ideal gas assumption that the isentropic exponent, , is equal to the ratio of specific heats, 

Cp/Cv. If good engineering judgment dictates using a real gas isentropic exponent, you may 

either use an appropriate equation of state to determine values of  as a function of measured 

pressures and temperatures, or you may develop your own calibration equations based on good 

engineering judgment. Calculate molar flow rate, , as follows: 

t in

d f

mix in

A p n CC

Z M RT

     

Eq. 1065.640-4 

Where: 

Cd = Discharge coefficient, as determined in paragraph (c)(1) of this section. 

Cf = Flow coefficient, as determined in paragraph (c)(2) of this section. 

At = Venturi throat cross-sectional area. 

pin = Venturi inlet absolute static pressure. 

Z = Compressibility factor. 

Mmix = Molar mass of gas mixture. 

R = Molar gas constant. 

Tin = Venturi inlet absolute temperature.

(1) Using the data collected in §1065.340, calculate Cd using the following equation: 

mix in

d ref

f t in

Z M RT

C n

C Ap

      

n
Eq. 1065.640-5 

Where: 

ref n = A reference molar flow rate. 

(2) Determine Cf using one of the following methods: 

(i) For CFV flow meters only, determine CfCFV from the following table based on your values for 

 and , using linear interpolation to find intermediate values: 

Table 2 of §1065.640– 

CfCFV versus  and  for CFV flow meters 

CfCFV

 exh = 

1.385 

dexh =

air= 

1.399 

0.000 0.6822 0.6846 

0.400 0.6857 0.6881 

0.500 0.6910 0.6934 

0.550 0.6953 0.6977 

0.600 0.7011 0.7036 

0.625 0.7047 0.7072 

0.650 0.7089 0.7114 

0.675 0.7137 0.7163 

0.700 0.7193 0.7219 

0.720 0.7245 0.7271 

0.740 0.7303 0.7329 

0.760 0.7368 0.7395 

0.770 0.7404 0.7431 

0.780 0.7442 0.7470 

0.790 0.7483 0.7511 

0.800 0.7527 0.7555 

0.810 0.7573 0.7602 

0.820 0.7624 0.7652 

0.830 0.7677 0.7707 

0.840 0.7735 0.7765 

0.850 0.7798 0.7828 

(ii) For any CFV or SSV flow meter, you may use the following equation to calculate Cf : 

 

   

1

2

1

2

f 4

2 1

1

r

C

r









 





      

   

Eq. 1065.640-6 
Where: 

 = isentropic exponent. For an ideal gas, this is the ratio of specific heats of the gas mixture, 

Cp/Cv. 

r = Pressure ratio, as determined in paragraph (c)(3) of this section. 

 = Ratio of venturi throat to inlet diameters. 

(3) Calculate r as follows: 

(i) For SSV systems only, calculate rSSV using the following equation: 

SSV

SSV

in

1 p r p

  

Eq. 1065.640-7 

Where: 

pSSV = Differential static pressure; venturi inlet minus venturi throat. 

(ii) For CFV systems only, calculate rCFV iteratively using the following equation: 

1 2 4

CFV CFV

1 1

2 2 r r 

         

      

Eq. 1065.640-8 

(4)You may make any of the following simplifying assumptions of the governing equations, or 

you may use good engineering judgment to develop more appropriate values for your testing: 

(i) For emission testing over the full ranges of raw exhaust, diluted exhaust and dilution air, you 

may assume that the gas mixture behaves as an ideal gas: Z=1. 

(ii) For the full range of raw exhaust you may assume a constant ratio of specific heats of 

=1.385. 

(iii) For the full range of diluted exhaust and air (e.g., calibration air or dilution air), you may 

assume a constant ratio of specific heats of =1.399. 

(iv) For the full range of diluted exhaust and air, you may assume the molar mass of the mixture 

is a function only of the amount of water in the dilution air or calibration air, xH2O, determined as 

described in §1065.645, as follows: 

Mmix = Mair · (1 – xH2O) + MH2O · xH2O

Eq. 1065.640-9 

Example:

Mair = 28.96559 g/mol 

xH2O = 0.0169 mol/mol 

MH2O = 18.01528 g/mol 

Mmix = 28.96559 · (1– 0.0169) + 18.01528 · 0.0169 

Mmix = 28.7805 g/mol 

(v) For the full range of diluted exhaust and air, you may assume a constant molar mass of the 

mixture, Mmix, for all calibration and all testing as long as your assumed molar mass differs no 

more than ±1 % from the estimated minimum and maximum molar mass during calibration and 

testing. You may assume this, using good engineering judgment, if you sufficiently control the 

amount of water in calibration air and in dilution air or if you remove sufficient water from both 

calibration air and dilution air. The following table gives examples of permissible ranges of 

dilution air dewpoint versus calibration air dewpoint: 
Table 3 of §1065.640– 

Examples of dilution air and calibration air 

dewpoints at which you may assume a constant Mmix. 

If calibration 

Tdew (C) is... 

assume the following 

constant Mmix (g/mol)... 

for the following ranges of Tdew

(C) during emission testsa

dry 28.96559 dry to 18 

0 28.89263 dry to 21 

5 28.86148 dry to 22 

10 28.81911 dry to 24 

15 28.76224 dry to 26 

20 28.68685 -8 to 28 

25 28.58806 12 to 31 

30 28.46005 23 to 34 

a

Range valid for all calibration and emission testing over the atmospheric 

pressure range (80.000 to 103.325) kPa. 

(5) The following example illustrates the use of the governing equations to calculate the 

discharge coefficient, Cd of an SSV flow meter at one reference flow meter value. Note that 

calculating Cd for a CFV flow meter would be similar, except that Cf would be determined from 

Table 2 of this section or calculated iteratively using values of  and  as described in paragraph 

(c)(2) of this section. 

Example:

ref n = 57.625 mol/s 

Z = 1 

Mmix = 28.7805 g/mol = 0.0287805 kg/mol 

R = 8.314472 J/(mol·K) 

Tin = 298.15 K 

At = 0.01824 m2

pin = 99132.0 Pa 

 = 1.399 

 = 0.8 

p = 2.312 kPa 

SSV

2.312 1 0.977

99.132 r  

 

   

1.399 1

1.399

2

1.399

1

2

f 4

2 1.399 0.977 1

1.399 1 0.8 0.977

C





          

Cf = 0.274 

d

1 0.0287805 8.314472 298.15 57.625

0.274 0.01824 99132.0

C      
Cd = 0.982 

(d) SSV calibration. Perform the following steps to calibrate an SSV flow meter: 

(1) Calculate the Reynolds number, Re#

, for each reference molar flow rate, using the throat 

diameter of the venturi, dt. Because the dynamic viscosity, , is needed to compute Re#

, you 

may use your own fluid viscosity model to determine for your calibration gas (usually air), 

using good engineering judgment. Alternatively, you may use the Sutherland three-coefficient 

viscosity model to approximate , as shown in the following sample calculation for Re#

: 

# mix ref

t

4 M n Re =  d  

 



Eq. 1065.640-10 

Where, using the Sutherland three-coefficient viscosity model: 

3

2 in 0

0

0 in

T TS

T TS  

              

Eq. 1065.640-11 

Where: 

 = Dynamic viscosity of calibration gas. 

0 = Sutherland reference viscosity. 

T0 = Sutherland reference temperature. 

S = Sutherland constant. 

Table 4 of §1065.640– 

Sutherland three-coefficient viscosity model parameters 

Gasa 0 T0 S

Temp range 

within ±2 % 

error 

Pressure 

limit 

kg /(m·s) K K K kPa 

Air 1.716·10-5 273 111 170 to 1900 ≤ 1800 

CO2 1.370·10-5 273 222 190 to 1700 ≤ 3600 

H2O 1.12·10-5 350 1064 360 to 1500 ≤ 10000 

O2 1.919·10-5 273 139 190 to 2000 ≤ 2500 

N2 1.663·10-5 273 107 100 to 1500 ≤ 1600 

a

Use tabulated parameters only for the pure gases, as listed. Do not combine 

parameters in calculations to calculate viscosities of gas mixtures. 

Example:

0 = 1.716·10-5 kg/(m·s) 

T0 = 273.11 K 

S = 110.56 K 
3

2 5 298.15 273.11 110.56 1.716 10

273.11 298.15 110.56                

 = 1.837·10-5 kg/(m·s) 

Mmix = 28.7805 g/mol 

ref n = 57.625 mol/s 

dt = 152.4 mm 

Tin = 298.15 K 

#

5

4 28.7805 57.625

3.14159 152.4 1.837 10

Re = 

 



Re# = 7.541·105

 

(2) Create an equation for Cd versus Re#

, using paired values of (Re#, Cd). For the equation, you 

may use any mathematical expression, including a polynomial or a power series. The following 

equation is an example of a commonly used mathematical expression for relating Cd and Re#

: 

6

d 01 #

10 C aa

Re  

Eq. 1065.640-12

(3) Perform a least-squares regression analysis to determine the best-fit coefficients to the 

equation and calculate the equation’s regression statistics, SEE and r

2

, according to §1065.602. 

(4) If the equation meets the criteria of SEE ≤ 0.5 % · refmax n and r

2 ≥ 0.995, you may use the 

equation to determine Cd for emission tests, as described in §1065.642. 

(5) If the SEE and r

2

 criteria are not met, you may use good engineering judgment to omit 

calibration data points to meet the regression statistics. You must use at least seven calibration 

data points to meet the criteria. 

(6)If omitting points does not resolve outliers, take corrective action. For example, select 

another mathematical expression for the Cd versus Re#

 equation, check for leaks, or repeat the 

calibration process. If you must repeat the process, we recommend applying tighter tolerances to 

measurements and allowing more time for flows to stabilize. 

(7) Once you have an equation that meets the regression criteria, you may use the equation only 

to determine flow rates that are within the range of the reference flow rates used to meet the Cd

versus Re#

 equation’s regression criteria. 

(e) CFV calibration. Some CFV flow meters consist of a single venturi and some consist of 

multiple venturis, where different combinations of venturis are used to meter different flow rates. 

For CFV flow meters that consist of multiple venturis, either calibrate each venturi 

independently to determine a separate discharge coefficient, Cd, for each venturi, or calibrate 

each combination of venturis as one venturi. In the case where you calibrate a combination of 

venturis, use the sum of the active venturi throat areas as At, the square root of the sum of the 

squares of the active venturi throat diameters as dt, and the ratio of the venturi throat to inlet 

diameters as the ratio of the square root of the sum of the active venturi throat diameters (dt) to 

the diameter of the common entrance to all of the venturis (D). To determine the Cd for a single 

venturi or a single combination of venturis, perform the following steps: 
(1) Use the data collected at each calibration set point to calculate an individual Cd for each point 

using Eq. 1065.640-4. 

(2) Calculate the mean and standard deviation of all the Cd values according to Eqs. 1065.602-1 

and 1065.602-2. 

(3) If the standard deviation of all the Cd values is less than or equal to 0.3 % of the mean Cd, use 

the mean Cd in Eq. 1065.642-4, and use the CFV only up to the highest r measured during 

calibration using the following equation: 

CFV

in

1 p r p

  

Eq. 1065.640-13 

Where: 

pCFV = Differential static pressure; venturi inlet minus venturi outlet. 

(4) If the standard deviation of all the Cd values exceeds 0.3 % of the mean Cd, omit the Cd value 

corresponding to the data point collected at the highest r measured during calibration. 

(5) If the number of remaining data points is less than seven, take corrective action by checking 

your calibration data or repeating the calibration process. If you repeat the calibration process, 

we recommend checking for leaks, applying tighter tolerances to measurements and allowing 

more time for flows to stabilize. 

(6) If the number of remaining Cd values is seven or greater, recalculate the mean and standard 

deviation of the remaining Cd values. 

(7) If the standard deviation of the remaining Cd values is less than or equal to 0.3 % of the 

mean of the remaining Cd, use that mean Cd in Eq. 1065.642-4, and use the CFV values only up 

to the highest r associated with the remaining Cd. 

(8) If the standard deviation of the remaining Cd still exceeds 0.3 % of the mean of the remaining 

Cd values, repeat the steps in paragraph (e)(4) through (8) of this section. 

§1065.642 SSV, CFV, and PDP molar flow rate calculations. 

This section describes the equations for calculating molar flow rates from various flow meters. 

After you calibrate a flow meter according to §1065.640, use the calculations described in this 

section to calculate flow during an emission test. 

(a) PDP molar flow rate. Based upon the speed at which you operate the PDP for a test interval, 

select the corresponding slope, a1, and intercept, a0, as calculated in §1065.640, to calculate 

molar flow rate, n as follows: 

nPDP

in rev

in

p V n f R T    

Eq. 1065.642-1 

Where: 

nPDP

1 out in

rev 0

out

a p p V a

f p

  

Eq. 1065.642-2 

Deleted: 6

Deleted: s

Deleted: 6

Comment [CAL8]: Corrected typo. 
Example: 

a1 = 50.43 (m3

/min) = 0.8405 (m3/s) 

fnPDP = 755.0 r/min = 12.58 r/s 

pout = 99950 Pa 

pin = 98575 Pa 

a0 = 0.056 (m3/r) 

R = 8.314472 J/(mol·K) 

Tin = 323.5 K 

Cp = 1000 (J/m3)/kPa 

Ct = 60 s/min 

rev

0.8405 99950 98575 0.056

12.58 99950

V   

Vrev = 0.06383 m3/r 

98575 0.06383 12.58

8.314472 323.5 n     

n = 29.428 mol/s 

(b) SSV molar flow rate. Based on the Cd versus Re#

 equation you determined according to 

§1065.640, calculate SSV molar flow rate, n during an emission test as follows: 

t in

d f

mix in

A p n CC

Z M RT

     

Eq. 1065.642-3 

Example: 

At = 0.01824 m2

pin = 99132 Pa 

Z = 1 

Mmix = 28.7805 g/mol = 0.0287805 kg/mol 

R = 8.314472 J/(mol·K) 

Tin = 298.15 K 

Re# = 7.232·105

 = 1.399 

 = 0.8 

p = 2.312 kPa 

Using Eq. 1065.640-7, 

rssv = 0.997 

Using Eq. 1065.640-6, 

Cf = 0.274 

Using Eq. 1065.640-5, 

Cd = 0.990 

Deleted: nPDP f
0.01824 99132 0.990 0.274

1 0.0287805 8.314472 298.15 n     

n = 58.173 mol/s 

(c) CFV molar flow rate. Some CFV flow meters consist of a single venturi and some consist of 

multiple venturis, where different combinations of venturis are used to meter different flow rates. 

If you use multiple venturis and you calibrated each venturi independently to determine a 

separate discharge (or calibration) coefficient, Cd (Kv), for each venturi, calculate the individual 

molar flow rates through each venturi and sum all their flow rates to determine n . If you use 

multiple venturis and you calibrated each combination of venturis, calculate n using the sum of 

the active venturi throat areas as At, the square root of the sum of the squares of the active venturi 

throat diameters as dt, and the ratio of the venturi throat to inlet diameters as the ratio of the 

square root of the sum of the active venturi throat diameters (dt) to the diameter of the common 

entrance to all of the venturis (D).

(1) To calculate the molar flow rate through one venturi or one combination of venturis, use its 

respective mean Cd and other constants you determined according to §1065.640 and calculate its 

molar flow rate n during an emission test, as follows: 

t in

d f

mix in

A p n CC

Z M RT

     

Eq. 1065.642-4 

Example: 

Cd = 0.985 

Cf = 0.7219 

At = 0.00456 m2

pin = 98836 Pa 

Z = 1 

Mmix = 28.7805 g/mol = 0.0287805 kg/mol 

R = 8.314472 J/(mol·K) 

Tin = 378.15 K 

0.00456 98836 0.985 0.7219

1 0.0287805 8.314472 378.15 n      

n = 33.690 mol/s

(2) To calculate the molar flow rate through one venturi or one combination of venturis, you may 

use its respective mean Kv and other constants you determined according to §1065.640 and 

calculate its molar flow rate n during an emission test. Note that if you choose to follow the 

permissible ranges of dilution air dewpoint versus calibration air dewpoint in Table 3 of 

§1065.640, you may set Mmix-cal and Mmix equal to 1. Calculate n as follows:

mix-cal in std

in mix std

Kp p v M n T M T R

    

Eq. 1065.642-5

Where:
stdref in-cal

in-cal

v

V T

K

p

 

Eq. 1065.642-6

Vstdref = volumetric flow of the standard at reference conditions of 293.15 K and 101.325 kPa.

Tin-cal = Venturi inlet temperature during calibration.

Pin-cal = Venturi inlet pressure during calibration.

Mmix-cal = Molar mass of gas mixture used during calibration.

Mmix = Molar mass of gas mixture during the emission test calculated using Equation 1065.640-

9.

Example: 

Vstdref = 0.4895 m3

Tin-cal = 302.52 K

Pin-cal = 99654 Pa

pin = 98836 Pa

pstd = 101325 Pa

Mmix-cal = 28.9656 g/mol = 0.0289656 kg/mol

Mmix = 28.7805 g/mol = 0.0287805 kg/mol

Tin = 353.15 K

Tstd = 293.15 K

R = 8.314472 J/(mol·K)

0.4895 302.52 4 0.5 0.000074954 m s K kg 99654

Kv

   

0.000074954 98936 101325 0.0289656

353.15 0.0287805 293.15 8.314472 n     

n = 16.457 mol/s

§1065.644 Vacuum-decay leak rate. 

This section describes how to calculate the leak rate of a vacuum-decay leak verification, which 

is described in §1065.345(e). Use Eq. 1065.644-1 to calculate the leak rate, leak n , and compare it 

to the criterion specified in §1065.345(e). 

 

2 1

vac 2 1

leak

2 1

p p

V T T n R t t

    

     

Eq. 1065.644-1 

Where: 

Vvac = geometric volume of the vacuum-side of the sampling system. 

R = molar gas constant. 

p2 = Vacuum-side absolute pressure at time t2. 

T2 = Vacuum-side absolute temperature at time t2. 
p1 = Vacuum-side absolute pressure at time t1. 

T1 = Vacuum-side absolute temperature at time t1. 

t2 = time at completion of vacuum-decay leak verification test. 

t1 = time at start of vacuum-decay leak verification test. 

Example:

Vvac = 2.0000 L = 0.00200 m3

R = 8.314472 J/(mol·K) 

p2 = 50.600 kPa = 50600 Pa 

T2 = 293.15 K 

p1 = 25.300 kPa = 25300 Pa 

T1 = 293.15 K 

t2 = 10:57:35 AM 

t1 = 10:56:25 AM 

  leak

50600 25300

0.0002 293.15 293.15

8.314472 10 : 57 : 35 10 : 56 : 25 n

          

leak

0.00200 86.304

8.314472 70 n  

leak n  0.00030 mol/s

§1065.645 Amount of water in an ideal gas. 

This section describes how to determine the amount of water in an ideal gas, which you need for 

various performance verifications and emission calculations. Use the equation for the vapor 

pressure of water in paragraph (a) of this section or another appropriate equation and, depending 

on whether you measure dewpoint or relative humidity, perform one of the calculations in 

paragraph (b) or (c) of this section. Paragraph (d) of this section provides an equation for 

determining dewpoint from relative humidity and dry bulb temperature measurements. The 

equations for the vapor pressure of water as presented in this section are derived from equations 

in “Saturation Pressure of Water on the New Kelvin Temperature Scale” (Goff, J.A., 

Transactions American Society of Heating and Air-Conditioning Engineers, Vol. 63, No. 1607, 

pages 347 – 354). Note that the equations were originally published to derive vapor pressure in 

units of atmospheres and have been modified to derive results in units of kPa by converting the 

last term in each equation. 

(a) Vapor pressure of water. Calculate the vapor pressure of water for a given saturation 

temperature condition, Tsat, as follows, or use good engineering judgment to use a different 

relationship of the vapor pressure of water to a given saturation temperature condition: 

(1) For humidity measurements made at ambient temperatures from (0 to 100) °C, or for 

humidity measurements made over super-cooled water at ambient temperatures from (–50 to 0) 

°C, use the following equation: 
sat

sat

8.2969 1 sat 4 273.16

10 H2O 10

sat

273.16 4.76955 1 3

273.16 log ( ) 10.79574 1 5.02800 log 1.50475 10 1 10 273.16

0.42873 10 10 1 0.2138602

T

T

T

p T

        

 

      

                           

 

     

 

Eq. 1065.645-1 

Where: 

pH20 = vapor pressure of water at saturation temperature condition, kPa. 

Tsat = saturation temperature of water at measured conditions, K. 

Example:

Tsat = 9.5 °C = 282.65 K 282.65 8.2969 1 4 273.16

10 H2O 10

273.16 4.76955 1 3 282.65

273.16 282.65 log ( ) 10.79574 1 5.02800 log 1.50475 10 1 10 282.65 273.16

0.42873 10 10 1 0.2138602

p

        

 

      

                     

 

     

 

log10(pH20) = 0.074297 

pH20 = 100.074297 = 1.186581 kPa 

(2) For humidity measurements over ice at ambient temperatures from (–100 to 0) °C, use the 

following equation: 

10 H2O 10

sat sat

sat

273.16 273.16 log ( ) 9.096853 1 3.566506 log

0.876812 1 0.2138602

273.16

p T T

T

             

        

Eq. 1065.645-2 

Example:

Tice = –15.4 °C = 257.75 K

10 H2O 10

273.16 273.16 log ( ) 9.096853 1 3.566506 log 257.75 257.75

257.75 0.876812 1 0.2138602

273.16

p

             

        

log10(pH20) = –0.798207 

pH20 = 10–0.79821 = 0.159145 kPa 

(b) Dewpoint. If you measure humidity as a dewpoint, determine the amount of water in an ideal 

gas, xH20, as follows: 

Deleted: Tsat = 9.5 + 273.15 = 282.65 K¶

Deleted: Tice = –15.4 + 273.15 = 257.75 K¶
H2O

H2O

abs

p x p 

Eq. 1065.645-3 

Where: 

xH20 = amount of water in an ideal gas. 

pH20 = water vapor pressure at the measured dewpoint, Tsat = Tdew. 

pabs = wet static absolute pressure at the location of your dewpoint measurement. 

Example:

pabs = 99.980 kPa 

Tsat = Tdew = 9.5 °C 

Using Eq. 1065.645-1, 

pH20 = 1.186581 kPa 

xH2O = 1.186581 / 99.980 

xH2O = 0.011868 mol/mol 

(c) Relative humidity. If you measure humidity as a relative humidity, RH %, determine the 

amount of water in an ideal gas, xH2O, as follows: 

H2O

H2O

abs

RH p % x p 

Eq. 1065.645-4 

Where: 

xH20 = amount of water in an ideal gas. 

RH % = relative humidity. 

pH20 = water vapor pressure at 100 % relative humidity at the location of your relative humidity 

measurement, Tsat = Tamb. 

pabs = wet static absolute pressure at the location of your relative humidity measurement. 

Example:

RH % = 50.77 % 

pabs = 99.980 kPa 

Tsat = Tamb = 20 °C 

Using Eq. 1065.645-1, 

pH20 = 2.3371 kPa 

xH2O = (50.77 % 2.3371) / 99.980

xH2O = 0.011868 mol/mol 

(d) Dewpoint determination from relative humidity and dry bulb temperature. This paragraph (d) 

describes how to calculate dewpoint temperature from relative humidity, RH %. This is based on 

“ITS-90 Formulations for Vapor Pressure, Frostpoint Temperature, Dewpoint Temperature, and 

Enhancement Factors in the Range –100 to +100 °C” (Hardy, B., The Proceedings of the Third 

International Symposium on Humidity & Moisture, Teddington, London, England, April 1998). 

Calculate pH20sat as described in paragraph (a) of this section based on setting Tsat equal to Tamb. 

Calculate pH20scaled by multiplying pH20sat by RH %. Calculate the dewpoint, Tdew, from pH20 using 
the following equation:

  

  

2 3 21 1 6

H2O H2O H2O

dew 2 3 13 5

H2O H2O H2O

2.0798233 10 2.0156028 10 ln 4.6778925 10 ln 9.2288067 10 ln

1 1.3319669 10 ln 5.6577518 10 ln 7.5172865 10 ln

pp p T

pp p

 

 

               

 Eq. 1065.645-5

Where: 

ln(pH20) = the natural log of pH2Oscaled, which is the water vapor pressure scaled to the relative 

humidity at the location of the relative humidity measurement, Tsat = Tamb.

Example:

RH % = 39.61 %

Tsat = Tamb = 20.00 °C = 293.15K

Using Eq. 1065.645-1,

pH20sat = 2.3371 kPa

pH2Oscaled = (39.61 %) = 0.925717 kPa = 925.717 Pa

  

  

21 1 6 2 3

dew 13 5 2 3

2.0798233 10 2.0156028 10 ln 925.717 4.6778925 10 ln 925.717 9.2288067 10 ln 925.717

1 1.3319669 10 ln 925.717 5.6577518 10 ln 925.717 7.5172865 10 ln 925.717

T

 

 

                   

Tdew = 279.00 K = 5.85 °C

§1065.650 Emission calculations. 

(a) General. Calculate brake-specific emissions over each applicable duty cycle or test interval. 

For test intervals with zero work (or power), calculate the emission mass (or mass rate), but do 

not calculate brake-specific emissions. For duty cycles with multiple test intervals, refer to the 

standard-setting part for calculations you need to determine a composite result, such as a 

calculation that weights and sums the results of individual test intervals in a duty cycle. If the 

standard-setting part does not include those calculations, use the equations in paragraph (g) of 

this section. This section is written based on rectangular integration, where each indexed value 

(i.e., “i”) represents (or approximates) the mean value of the parameter for its respective time 

interval, delta-t. You may also integrate continuous signals using trapezoidal integration 

consistent with good engineering judgment. 

(b) Brake-specific emissions over a test interval. We specify three alternative ways to calculate 

brake-specific emissions over a test interval, as follows: 

(1) For any testing, you may calculate the total mass of emissions, as described in paragraph (c) 

of this section, and divide it by the total work generated over the test interval, as described in 

paragraph (d) of this section, using the following equation: 

m e W=

Eq. 1065.650-1 

Example:

mNOx = 64.975 g 

W = 25.783 kW·hr 

eNOx = 64.975/25.783 

eNOx = 2.520 g/(kW·hr) 
(2) For discrete-mode steady-state testing, you may calculate the brake-specific emissions over a 

test interval using the ratio of emission mass rate to power, as described in paragraph (e) of this 

section, using the following equation: 

m e P = 

Eq. 1065.650-2 

(3) For field testing, you may calculate the ratio of total mass to total work, where these 

individual values are determined as described in paragraph (f) of this section. You may also use 

this approach for laboratory testing, consistent with good engineering judgment. Good 

engineering judgment dictates that this method not be used if there are any work flow paths 

described in §1065.210 that cross the system boundary, other than the primary output shaft 

(crankshaft). This is a special case in which you use a signal linearly proportional to raw exhaust 

molar flow rate to determine a value proportional to total emissions. You then use the same 

linearly proportional signal to determine total work using a chemical balance of fuel, intake air, 

and exhaust as described in §1065.655, plus information about your engine’s brake-specific fuel 

consumption. Under this method, flow meters need not meet accuracy specifications, but they 

must meet the applicable linearity and repeatability specifications in subpart D or subpart J of 

this part. The result is a brake-specific emission value calculated as follows: 

m e W= 



Eq. 1065.650-3 

Example:

m = 805.5 g 

W = 52.102 kW·hr 

eCO = 805.5/52.102 

eCO = 2.520 g/(kW·hr) 

(c) Total mass of emissions over a test interval. To calculate the total mass of an emission, 

multiply a concentration by its respective flow. For all systems, make preliminary calculations 

as described in paragraph (c)(1) of this section to correct concentrations. Next, use the method in 

paragraphs (c)(2) through (4) of this section that is appropriate for your system. Finally, if 

necessary, calculate the mass of NMHC as described in paragraph (c)(5) of this section for all 

systems. Calculate the total mass of emissions as follows: 

(1) Concentration corrections. Perform the following sequence of preliminary calculations on 

recorded concentrations: 

(i) Correct all gaseous emission analyzer concentration readings, including continuous readings, 

sample bag readings, and dilution air background readings, for drift as described in §1065.672. 

Note that you must omit this step where brake-specific emissions are calculated without the drift 

correction for performing the drift validation according to §1065.550(b). When applying the 

initial THC and CH4 contamination readings according to §1065.520(f), use the same values for 

both sets of calculations. You may also use as-measured values in the initial set of calculations 

and corrected values in the drift-corrected set of calculations as described in §1065.520(g)(7). 

(ii) Correct all THC and CH4 concentrations for initial contamination as described in 

§1065.660(a), including continuous readings, sample bags readings, and dilution air background 

readings. 

Deleted: g

Deleted: , for initial contamination, as described in 

§1065.660(a)
(iii) Correct all concentrations measured on a “dry” basis to a “wet” basis, including dilution air 

background concentrations, as described in §1065.659. 

(iv) Calculate all NMHC and CH4 concentrations, including dilution air background 

concentrations, as described in §1065.660. 

(v) For emission testing with an oxygenated fuel, calculate any HC concentrations, including 

dilution air background concentrations, as described in §1065.665. See subpart I of this part for 

testing with oxygenated fuels. 

(vi) Correct all the NOx concentrations, including dilution air background concentrations, for 

intake-air humidity as described in §1065.670. 

(2) Continuous sampling. For continuous sampling, you must frequently record a continuously 

updated concentration signal. You may measure this concentration from a changing flow rate or 

a constant flow rate (including discrete-mode steady-state testing), as follows: 

(i) Varying flow rate. If you continuously sample from a changing exhaust flow rate, time align 

and then multiply concentration measurements by the flow rate from which you extracted it. Use 

good engineering judgment to time-align flow and concentration data to match transformation 

time, t50, to within ±1 s. We consider the following to be examples of changing flows that 

require a continuous multiplication of concentration times molar flow rate: raw exhaust, exhaust 

diluted with a constant flow rate of dilution air, and CVS dilution with a CVS flow meter that 

does not have an upstream heat exchanger or electronic flow control. This multiplication results 

in the flow rate of the emission itself. Integrate the emission flow rate over a test interval to 

determine the total emission. If the total emission is a molar quantity, convert this quantity to a 

mass by multiplying it by its molar mass, M. The result is the mass of the emission, m. 

Calculate m for continuous sampling with variable flow using the following equations: 

i i

i 1

N

m M xn t      

 Eq. 1065.650-4 

Where: 

∆t = 1/frecord Eq. 1065.650-5 

Example:

MNMHC = 13.875389 g/mol 

N = 1200 

xNMHC1 = 84.5 μmol/mol = 84.5·0-6 mol/mol 

xNMHC2 = 86.0 μmol/mol = 86.0·10-6 mol/mol 

exh1 n = 2.876 mol/s 

exh2 n = 2.224 mol/s 

frecord = 1 Hz 

Using Eq. 1065.650-5, 

t = 1/1 = 1 s 6 6

NMHC NMHC1200 13.875389 (84.5 10 2.876 86.0 10 2.224 ... ) 1 m xnexh

            

mNMHC = 25.23 g 
(ii) Constant flow rate. If you continuously sample from a constant exhaust flow rate, use the 

same emission calculations described in paragraph (c)(2)(i) of this section or calculate the mean 

or flow-weighted concentration recorded over the test interval and treat the mean as a batch 

sample, as described in paragraph (c)(3)(ii) of this section. We consider the following to be 

examples of constant exhaust flows: CVS diluted exhaust with a CVS flow meter that has either 

an upstream heat exchanger, electronic flow control, or both. 

(3) Batch sampling. For batch sampling, the concentration is a single value from a proportionally 

extracted batch sample (such as a bag, filter, impinger, or cartridge). In this case, multiply the 

mean concentration of the batch sample by the total flow from which the sample was extracted. 

You may calculate total flow by integrating a changing flow rate or by determining the mean of a 

constant flow rate, as follows: 

(i) Varying flow rate. If you collect a batch sample from a changing exhaust flow rate, extract a 

sample proportional to the changing exhaust flow rate. We consider the following to be 

examples of changing flows that require proportional sampling: raw exhaust, exhaust diluted 

with a constant flow rate of dilution air, and CVS dilution with a CVS flow meter that does not 

have an upstream heat exchanger or electronic flow control. Integrate the flow rate over a test 

interval to determine the total flow from which you extracted the proportional sample. Multiply 

the mean concentration of the batch sample by the total flow from which the sample was 

extracted. If the total emission is a molar quantity, convert this quantity to a mass by multiplying 

it by its molar mass, M. The result is the mass of the emission, m. In the case of PM emissions, 

where the mean PM concentration is already in units of mass per mole of sample, MPM , simply 

multiply it by the total flow. The result is the total mass of PM, mPM. Calculate m for batch 

sampling with variable flow using the following equation: 

i

i 1

N

m Mx n t      

Eq. 1065.650-6 

Example:

MNOx = 46.0055 g/mol 

N = 9000 

NOx x = 85.6 μmol/mol = 85.610-6 mol/mol 

dexh1 n = 25.534 mol/s 

dexh2 n = 26.950 mol/s 

frecord = 5 Hz 

Using Eq. 1065.650-5, 

t = 1/5 = 0.2 6

NOx exh9000 m n 46.0055 85.6 10 (25.534 26.950 ... ) 0.2         

mNOx = 4.201 g 

(ii) Constant flow rate. If you batch sample from a constant exhaust flow rate, extract a sample at 

a proportional or constant flow rate. We consider the following to be examples of constant 

exhaust flows: CVS diluted exhaust with a CVS flow meter that has either an upstream heat 

exchanger, electronic flow control, or both. Determine the mean molar flow rate from which you 
extracted the constant flow rate sample. Multiply the mean concentration of the batch sample by 

the mean molar flow rate of the exhaust from which the sample was extracted, and multiply the 

result by the time of the test interval. If the total emission is a molar quantity, convert this 

quantity to a mass by multiplying it by its molar mass, M. The result is the mass of the emission, 

m. In the case of PM emissions, where the mean PM concentration is already in units of mass 

per mole of sample, MPM , simply multiply it by the total flow, and the result is the total mass of 

PM, mPM, Calculate m for sampling with constant flow using the following equations: 

m Mxn t     

Eq. 1065.650-7 

and for PM or any other analysis of a batch sample that yields a mass per mole of sample, 

M   M x

Eq. 1065.650-8 

Example:

MPM = 144.0 g/mol = 144.0·10-6 g/mol

dexh n = 57.692 mol/s 

t = 1200 s 

mPM = 144.010-657.6921200

mPM = 9.9692 g 

(4) Additional provisions for diluted exhaust sampling; continuous or batch. The following 

additional provisions apply for sampling emissions from diluted exhaust: 

(i) For sampling with a constant dilution ratio, DR, of diluted exhaust versus exhaust flow (e.g., 

secondary dilution for PM sampling), calculate m using the following equation: 

mPM = mPMdil · DR

Eq. 1065.650-9 

Example:

mPMdil = 6.853 g 

DR = 6:1 

mPM = 6.853 · 6 

mPM = 41.118 g 

(ii) For continuous or batch sampling, you may measure background emissions in the dilution 

air. You may then subtract the measured background emissions, as described in §1065.667. 

(5) Mass of NMHC. Compare the corrected mass of NMHC to corrected mass of THC. If the 

corrected mass of NMHC is greater than 0.98 times the corrected mass of THC, take the 

corrected mass of NMHC to be 0.98 times the corrected mass of THC. If you omit the NMHC 

calculations as described in §1065.660(b)(1), take the corrected mass of NMHC to be 0.98 times 

the corrected mass of THC. 

(d) Total work over a test interval. To calculate the total work from the engine over a test 

interval, add the total work from all the work paths described in §1065.210 that cross the system 

boundary including electrical energy/work, mechanical shaft work, and fluid pumping work. For 

all work paths, except the engine’s primary output shaft (crankshaft), the total work for the path 

over the test interval is the integration of the net work flow rate (power) out of the system 

boundary. When energy/work flows into the system boundary, this work flow rate signal 

becomes negative; in this case, include these negative work rate values in the integration to 

calculate total work from that work path. Some work paths may result in a negative total work. 
Include negative total work values from any work path in the calculated total work from the 

engine rather than setting the values to zero. The rest of this paragraph (d) describes how to 

calculate total work from the engine’s primary output shaft over a test interval. Before 

integrating power on the engine’s primary output shaft, adjust the speed and torque data for the 

time alignment used in §1065.514(c). Any advance or delay used on the feedback signals for 

cycle validation must also be used for calculating work. Account for work of accessories 

according to §1065.110. Exclude any work during cranking and starting. Exclude work during 

actual motoring operation (negative feedback torques), unless the engine was connected to one or 

more energy storage devices. Examples of such energy storage devices include hybrid 

powertrain batteries and hydraulic accumulators, like the ones illustrated in Figure 1 of 

§1065.210. Exclude any work during reference zero-load idle periods (0 % speed or idle speed 

with 0 N·m reference torque). Note, that there must be two consecutive reference zero load idle 

points to establish a period where this applies. Include work during idle points with simulated 

minimum torque such as Curb Idle Transmissions Torque (CITT) for automatic transmissions in 

“drive”. The work calculation method described in paragraphs (b)(1) though (7) of this section 

meets these requirements using rectangular integration. You may use other logic that gives 

equivalent results. For example, you may use a trapezoidal integration method as described in 

paragraph (b)(8) of this section. 

(1) Time align the recorded feedback speed and torque values by the amount used in 

§1065.514(c). 

(2) Calculate shaft power at each point during the test interval by multiplying all the recorded 

feedback engine speeds by their respective feedback torques. 

(3) Adjust (reduce) the shaft power values for accessories according to §1065.110. 

(4) Set all power values during any cranking or starting period to zero. See §1065.525 for more 

information about engine cranking. 

(5) Set all negative power values to zero, unless the engine was connected to one or more energy 

storage devices. If the engine was tested with an energy storage device, leave negative power 

values unaltered. 

(6) Set all power values to zero during idle periods with a corresponding reference torque of 0 

N·m. 

(7) Integrate the resulting values for power over the test interval. Calculate total work as 

follows: 

i

i 1

N

W Pt   

Eq. 1065.650-10 

Where: 

W = total work from the primary output shaft 

Pi = instantaneous power from the primary output shaft over an interval i. 

Pi = fni · Ti

Eq. 1065.650-11 

Example:

N = 9000 

fn1 = 1800.2 r/min 

fn2 = 1805.8 r/min 
T1 = 177.23 N·m 

T2 = 175.00 N·m 

Crev = 2· rad/r 

Ct1 = 60 s/min 

Cp = 1000 (N·m·rad/s)/kW

frecord = 5 Hz 

Ct2 = 3600 s/hr 

1

1800.2 177.23 2 3.14159

60 1000

P    

P1 = 33.41 kW 

P2 = 33.09 kW 

Using Eq. 1065.650-5, 

t = 1/5 = 0.2 s 

9000 (33.41 33.09 ... ) 0.2

3600

P W    

W = 16.875 kW·hr 

(8) You may use a trapezoidal integration method instead of the rectangular integration described 

in this paragraph (d). To do this, you must integrate the fraction of work between points where 

the torque is positive. You may assume that speed and torque are linear between data points. 

You may not set negative values to zero before running the integration. 

(e) Steady-state mass rate divided by power. To determine steady-state brake-specific emissions 

for a test interval as described in paragraph (b)(2) of this section, calculate the mean steady-state 

mass rate of the emission, , and the mean steady-state power, , as follows: 

(1) To calculate , multiply its mean concentration, x , by its corresponding mean molar flow 

rate, n . If the result is a molar flow rate, convert this quantity to a mass rate by multiplying it by 

its molar mass, M. The result is the mean mass rate of the emission, m . In the case of PM 

emissions, where the mean PM concentration is already in units of mass per mole of sample, 

MPM , simply multiply it by the mean molar flow rate, n . The result is the mass rate of PM, 

mPM  . Calculate m using the following equation: 

m Mxn    

Eq. 1065.650-12 

(2) To calculate an engine’s mean steady-state total power, P , add the mean steady-state power 

from all the work paths described in §1065.210 that cross the system boundary including 

electrical power, mechanical shaft power, and fluid pumping power. For all work paths, except 

the engine’s primary output shaft (crankshaft), the mean steady-state power over the test interval 

is the integration of the net work flow rate (power) out of the system boundary divided by the 

period of the test interval. When power flows into the system boundary, the power/work flow 

rate signal becomes negative; in this case, include these negative power/work rate values in the 

integration to calculate the mean power from that work path. Some work paths may result in a 

negative mean power. Include negative mean power values from any work path in the mean 

m P

m
total power from the engine rather than setting these values to zero. The rest of this paragraph 

(e)(2) describes how to calculate the mean power from the engine’s primary output shaft. 

Calculate P using Equation 1065.650-13, noting that P , nf and T refer to mean power, mean 

rotational shaft frequency, and mean torque from the primary output shaft. Account for the 

power of simulated accessories according to §1065.110 (reducing the mean primary output shaft 

power or torque by the accessory power or torque). Set the power to zero during actual motoring 

operation (negative feedback torques), unless the engine was connected to one or more energy 

storage devices. Examples of such energy storage devices include hybrid powertrain batteries 

and hydraulic accumulators, like the ones illustrated in Figure 1 of §1065.210. Set the power to 

zero for modes with a zero reference load (0 N·m reference torque or 0 kW reference power). 

Include power during idle modes with simulated minimum torque or power.

P fT   n

Eq. 1065.650-13 

(3) Divide emission mass rate by power to calculate a brake-specific emission result as described 

in paragraph (b)(2) of this section. 

(4) The following example shows how to calculate mass of emissions using mean mass rate and 

mean power:

MCO = 28.0101 g/mol 

CO x = 12.00 mmol/mol = 0.01200 mol/mol 

n = 1.530 mol/s 

nf = 3584.5 r/min = 375.37 rad/s 

T = 121.50 N·m 

m  28.0101 0.01200 1.530

m = 0.514 g/s = 1850.4 g/hr 

P   121.5 375.37

P = 45607 W 

P = 45.607 kW 

eCO = 1850.4/45.61 

eCO = 40.57 g/(kW·hr) 

(f) Ratio of total mass of emissions to total work. To determine brake-specific emissions for a 

test interval as described in paragraph (b)(3) of this section, calculate a value proportional to the 

total mass of each emission. Divide each proportional value by a value that is similarly 

proportional to total work. 

(1) Total mass. To determine a value proportional to the total mass of an emission, determine 

total mass as described in paragraph (c) of this section, except substitute for the molar flow rate, 

n , or the total flow, n, with a signal that is linearly proportional to molar flow rate, n

 , or linearly 

proportional to total flow, n , as follows: 

C i Ccombdryi

fueli

fuel H2Oexhdryi

1

1

M nx m w x    

 

Eq. 1065.650-14 

(2) Total work. To calculate a value proportional to total work over a test interval, integrate a 
value that is proportional to power. Use information about the brake-specific fuel consumption 

of your engine, efuel, to convert a signal proportional to fuel flow rate to a signal proportional to 

power. To determine a signal proportional to fuel flow rate, divide a signal that is proportional to 

the mass rate of carbon products by the fraction of carbon in your fuel, wc.. You may use a 

measured wc or you may use default values for a given fuel as described in §1065.655(d). 

Calculate the mass rate of carbon from the amount of carbon and water in the exhaust, which you 

determine with a chemical balance of fuel, intake air, and exhaust as described in §1065.655. In 

the chemical balance, you must use concentrations from the flow that generated the signal 

proportional to molar flow rate, n

 , in paragraph (e)(1) of this section. Calculate a value 

proportional to total work as follows: 

1

N

i

i

W Pt    

Eq. 1065.650-15 

Where: 

Eq. 1065.650-16 

(3) Brake-specific emissions. Divide the value proportional to total mass by the value 

proportional to total work to determine brake-specific emissions, as described in paragraph (b)(3) 

of this section. 

(4) Example. The following example shows how to calculate mass of emissions using 

proportional values: 

N = 3000 

frecord = 5 Hz 

efuel = 285 g/(kW·hr) 

wfuel = 0.869 g/g 

Mc = 12.0107 g/mol 

1 n

 = 3.922 mol/s = 14119.2 mol/hr 

xCcombdry1 = 91.634 mmol/mol = 0.091634 mol/mol 

xH2Oexh1 = 27.21 mmol/mol = 0.02721 mol/mol 

Using Eq. 1065.650-5, 

t = 0.2 s 

2 Ccombdry2 3000 Ccombdry3000

H2Oexh2 H2Oexh3000

3.922 0.091634 12.0107 ... 0.2

1 0.02721 1 1

285 0.869

nx n x

x x W

               

   



W = 5.09 (kW·hr) 

(g) Brake-specific emissions over a duty cycle with multiple test intervals. The standard-setting 

part may specify a duty cycle with multiple test intervals, such as with discrete-mode steadystate testing. Unless we specify otherwise, calculate composite brake-specific emissions over the 

duty cycle as described in this paragraph (g). If a measured mass (or mass rate) is negative, set it 

to zero for calculating composite brake-specific emissions, but leave it unchanged for drift 

fueli

i

fuel

m P e   
validation. In the case of calculating composite brake-specific emissions relative to a combined 

emission standard (such as a NOx + NMHC standard), change any negative mass (or mass rate) 

values to zero for a particular pollutant before combining the values for the different pollutants. 

(1) Use the following equation to calculate composite brake-specific emissions for duty cycles 

with multiple test intervals all with prescribed durations, such as cold-start and hot-start transient 

cycles: 

1

composite

1

N

i i

i

N

i i

i

WF m

e

WF W















Eq. 1065.650-17 

Where 

i = test interval number. 

N = number of test intervals. 

WF = weighting factor for the test interval as defined in the standard-setting part. 

m = mass of emissions over the test interval as determined in paragraph (c) of this section. 

W = total work from the engine over the test interval as determined in paragraph (d) of this 

section. 

Example:

N = 2 

WF1 = 0.1428 

WF2 = 0.8572 

m1 = 70.125 g 

m2 = 64.975 g 

W1 = 25.783 kW·hr 

W2 = 25.783 kW·hr 

 

  NO composite

(0.1428 70.125) 0.8572 64.975

(0.1428 25.783) 0.8572 25.783 x e   

eNOxcomposite = 2.548 g/kW·hr 

(2) Calculate composite brake-specific emissions for duty cycles with multiple test intervals that 

allow use of varying duration, such as discrete-mode steady-state duty cycles, as follows: 

(i) Use the following equation if you calculate brake-specific emissions over test intervals based 

on total mass and total work as described in paragraph (b)(1) of this section: 

1

composite

1

N

i

i

i i

N

i

i

i i

m WF

t e W WF

t















Eq. 1065.650-18 

Where 

i = test interval number. 

N = number of test intervals. 
WF = weighting factor for the test interval as defined in the standard-setting part. 

m = mass of emissions over the test interval as determined in paragraph (c) of this section. 

W = total work from the engine over the test interval as determined in paragraph (d) of this 

section. 

t = duration of the test interval. 

Example:

N = 2 

WF1 = 0.85 

WF2 = 0.15 

m1 = 1.3753 g 

m2 = 0.4135 g 

t1 = 120 s 

t2 = 200 s 

W1 = 2.8375 kW·hr 

W2 = 0.0 kW·hr 

NO composite

1.3753 0.4135 0.85 0.15

120 200

2.8375 0.0 0.85 0.15

120 200

x e

                      

eNOxcomposite = 0.5001 g/kW·hr 

(ii) Use the following equation if you calculate brake-specific emissions over test intervals based 

on the ratio of mass rate to power as described in paragraph (b)(2) of this section: 

1

composite

1

N

i i

i

N

i i

i

WF m

e

WF P

















Eq. 1065.650-19 

Where 

i = test interval number. 

N = number of test intervals. 

WF = weighting factor for the test interval as defined in the standard-setting part. 

m = mean steady-state mass rate of emissions over the test interval as determined in paragraph 

(e) of this section. 

P is the mean steady-state power over the test interval as described in paragraph (e) of this 

section. 

Example:

N = 2 

WF1 = 0.85 

WF2 = 0.15 

m1  = 2.25842 g/hr 

m2  = 0.063443 g/hr 
P1 = 4.5383 kW 

P2 = 0.0 kW 

 

  NO composite

(0.85 2.25842) 0.15 0.063443

(0.85 4.5383) 0.15 0.0 x e     

eNOxcomposite = 0.5001 g/kW·hr 

(h) Rounding. Round the final brake-specific emission values to be compared to the applicable 

standard only after all calculations are complete (including any drift correction, applicable 

deterioration factors, adjustment factors, and allowances) and the result is in g/(kW·hr) or units 

equivalent to the units of the standard, such as g/(hp·hr). See the definition of “Round” in 

§1065.1001. 

§1065.655 Chemical balances of fuel, intake air, and exhaust. 

(a) General. Chemical balances of fuel, intake air, and exhaust may be used to calculate flows, 

the amount of water in their flows, and the wet concentration of constituents in their flows. With 

one flow rate of either fuel, intake air, or exhaust, you may use chemical balances to determine 

the flows of the other two. For example, you may use chemical balances along with either intake 

air or fuel flow to determine raw exhaust flow. 

(b) Procedures that require chemical balances. We require chemical balances when you 

determine the following: 

(1) A value proportional to total work, W when you choose to determine brake-specific 

emissions as described in §1065.650(f). 

(2) The amount of water in a raw or diluted exhaust flow, xH2Oexh, when you do not measure the 

amount of water to correct for the amount of water removed by a sampling system. Correct for 

removed water according to §1065.659. 

(3) The calculated total dilution air flow when you do not measure dilution air flow to correct for 

background emissions as described in §1065.667(c) and (d). 

(c) Chemical balance procedure. The calculations for a chemical balance involve a system of 

equations that require iteration. We recommend using a computer to solve this system of 

equations. You must guess the initial values of up to three quantities: the amount of water in the 

measured flow, xH2Oexh, fraction of dilution air in diluted exhaust, xdil/exh, and the amount of 

products on a C1 basis per dry mole of dry measured flow, xCcombdry. You may use time-weighted 

mean values of combustion air humidity and dilution air humidity in the chemical balance; as 

long as your combustion air and dilution air humidities remain within tolerances of ±0.0025 

mol/mol of their respective mean values over the test interval. For each emission concentration, 

x, and amount of water, xH2Oexh, you must determine their completely dry concentrations, xdry and 

xH2Oexhdry. You must also use your fuel’s atomic hydrogen-to-carbon ratio, , oxygen-to-carbon 

ratio, sulfur-to-carbon ratio, , and nitrogen-to-carbon ratio, . You may calculate , , , and 

 based on measured fuel composition as described in paragraphs (d)(1) and (2) of this section, 

or you may use default values for a given fuel as described in §1065.655(d)(3). Use the 

following steps to complete a chemical balance: 

(1) Convert your measured concentrations such as, xCO2meas, xNOmeas, and xH2Oint, to dry 

concentrations by dividing them by one minus the amount of water present during their 

respective measurements; for example: xH2OxCO2meas, xH2OxNOmeas, and xH2Oint. If the amount of 

water present during a “wet” measurement is the same as the unknown amount of water in the 

exhaust flow, xH2Oexh, iteratively solve for that value in the system of equations. If you measure 

Deleted: measure 
only total NOx and not NO and NO2 separately, use good engineering judgment to estimate a 

split in your total NOx concentration between NO and NO2 for the chemical balances. For 

example, if you measure emissions from a stoichiometric spark-ignition engine, you may assume 

all NOx is NO. For a compression-ignition engine, you may assume that your molar 

concentration of NOx, xNOx, is 75 % NO and 25 % NO2. For NO2 storage aftertreatment systems, 

you may assume xNOx is 25 % NO and 75 % NO2. Note that for calculating the mass of NOx

emissions, you must use the molar mass of NO2 for the effective molar mass of all NOx species, 

regardless of the actual NO2 fraction of NOx. 

(2) Enter the equations in paragraph (c)(4) of this section into a computer program to iteratively 

solve for xH2Oexh, xCcombdry, and xdil/exh. Use good engineering judgment to guess initial values for 

xH2Oexh, xCcombdry, and xdil/exh. We recommend guessing an initial amount of water that is about 

twice the amount of water in your intake or dilution air. We recommend guessing an initial 

value of xCcombdry as the sum of your measured CO2, CO, and THC values. We also recommend 

guessing an initial xdil/exh between 0.75 and 0.95, such as 0.8. Iterate values in the system of 

equations until the most recently updated guesses are all within ±1 % of their respective most 

recently calculated values. 

(3) Use the following symbols and subscripts in the equations for this paragraph (c): 

xdil/exh = amount of dilution gas or excess air per mole of exhaust. 

xH2Oexh = amount of H2O in exhaust per mole of exhaust. 

xCcombdry = amount of carbon from fuel in the exhaust per mole of dry exhaust. 

xH2dry = amount of H2 in exhaust per amount of dry exhaust. 

KH2Ogas = water-gas reaction equilibrium coefficient. You may use 3.5 or calculate your own 

value using good engineering judgment. 

xH2Oexhdry = amount of H2O in exhaust per dry mole of dry exhaust. 

xprod/intdry = amount of dry stoichiometric products per dry mole of intake air. 

xdil/exhdry = amount of dilution gas and/or excess air per mole of dry exhaust. 

xint/exhdry = amount of intake air required to produce actual combustion products per mole of dry 

(raw or diluted) exhaust.

xraw/exhdry = amount of undiluted exhaust, without excess air, per mole of dry (raw or diluted) 

exhaust. 

xO2int = amount of intake air O2 per mole of intake air. 

xCO2intdry = amount of intake air CO2 per mole of dry intake air. You may use xCO2intdry = 375 

μmol/mol, but we recommend measuring the actual concentration in the intake air. 

xH2Ointdry = amount of intake air H2O per mole of dry intake air. 

xCO2int = amount of intake air CO2 per mole of intake air. 

xCO2dil = amount of dilution gas CO2 per mole of dilution gas. 

xCO2dildry = amount of dilution gas CO2 per mole of dry dilution gas. If you use air as diluent, you 

may use xCO2dildry = 375 μmol/mol, but we recommend measuring the actual concentration in the 

intake air. 

xH2Odildry = amount of dilution gas H2O per mole of dry dilution gas. 

xH2Odil = amount of dilution gas H2O per mole of dilution gas. 

x[emission]meas = amount of measured emission in the sample at the respective gas analyzer. 

x[emission]dry = amount of emission per dry mole of dry sample. 

xH2O[emission]meas = amount of H2O in sample at emission-detection location. Measure or estimate 

these values according to §1065.145(e)(2). 

xH2Oint = amount of H2O in the intake air, based on a humidity measurement of intake air. 

Deleted: water 

Deleted: water 

Deleted: water 

Deleted: water 
 = atomic hydrogen-to-carbon ratio of the mixture of fuel(s) being combusted, weighted by 

molar consumption. 

 = atomic oxygen-to-carbon ratio of the mixture of fuel(s) being combusted, weighted by molar 

consumption. 

 = atomic sulfur-to-carbon ratio of the mixture of fuel(s) being combusted, weighted by molar 

consumption. 

 = atomic nitrogen-to-carbon ratio of the mixture of fuel(s) being combusted, weighted by 

molar consumption. 

(4) Use the following equations to iteratively solve for xdil/exh, xH2Oexh, and xCcombdry: 

raw/exhdry

dil/exh

H2Oexhdry

1

1

x x x = - +

Eq. 1065.655-1 

H2Oexhdry

H2Oexh

H2Oexhdry 1+

x x x =

Eq. 1065.655-2 

Ccombdry CO2dry COdry THCdry CO2dil dil/exhdry CO2int int/exhdry x x x x xx xx    

Eq. 1065.655-3 

 

 

COdry H2Oexhdry H2Odil dil/exhdry

H2dry

H2O-gas CO2dry CO2dil dil/exhdry

x x xx x K x xx

    

Eq. 1065.655-4 

H2Oexhdry Ccombdry THCdry H2Odil dil/exhdry H2Oint int/exhdry H2dry   2 x x x xx xx x 

    

Eq. 1065.655-5 

dil/exh

dil/exhdry

H2Oexh 1

x x x = -

Eq. 1065.655-6 

int/exhdry Ccombdry THCdry COdry NOdry NO2dry H2dry    O2int

1 22 2

2 2 x x x xx x x x

                       

Eq. 1065.655-7 

raw/exhdry Ccombdry THCdry THCdry COdry NO2dry H2dry int/exhdry    1 2

2 2 x x x x xx x x                       

Eq. 1065.655-8 

CO2intdry

O2int

H2Ointdry

0.209820

1

x x x

- = +

Eq. 1065.655-9 

CO2intdry

CO2int

H2Ointdry

 1

x x x = +

Eq. 1065.655-10 
H2Oint

H2Ointdry

H2Oint 1

x x x = -

Eq. 1065.655-11 

CO2dildry

CO2dil

H2Odildry 1

x x x = +

Eq. 1065.655-12 

H2Odil

H2Odildry

H2Odil

 1

x x x = -

Eq. 1065.655-13 

COmeas

COdry

H2OCOmeas

=

1

x x - x

Eq. 1065.655-14 

CO2meas

CO2dry

H2OCO2meas

=

1

x x - x

Eq. 1065.655-15 

NOmeas

NOdry

H2ONOmeas

=

1

x x - x

Eq. 1065.655-16 

NO2meas

NO2dry

H2ONO2meas

=

1

x x - x

Eq. 1065.655-17 

THCmeas

THCdry

H2OTHCmeas

=

1

x x - x

Eq. 1065.655-18 

(5) The following example is a solution for xdil/exh, xH2Oexh, and xCcombdry using the equations in 

paragraph (c)(4) of this section: 

dil/exh

0.184 1 0.822 35.37 1

1000

x =- = mol mol

+

H2Oexh

35.37 34.16 35.37 1+

1000

x = = mmol mol
Ccombdry

29.3 47.6 0.371 0.369 0.0252 0.851 0.172 0.0249

1000000 1000000 1000 1000 x        mol mol

 

H2dry

29.3 0.034 0.012 0.851

8.5

25.2 0.371 3.5 0.851

1000 1000

x mol mol      

     

H2Oexhdry

1.8 47.6 8.5 0.0249 0.012 0.851 0.017 0.172 0.0353

2 1000000 1000000 x mol mol          

dil/exhdry

0.822 0.851

1-0.034 x = = mol mol

int/exhdry

1.8 47.6 0.050 2 2 0.0003 0.0249

1 2 1000000

0.172

2 0.206 29.3 50.4 12.1 8.5 2

1000000 1000000 1000000 1000000

x mol mol

                          

   

raw/exhdry

1.8 47.6 0.050 0.0001 0.0249

1 2 1000000

0.172 0.184

2 47.6 29.3 12.1 8.5 2

1000000 1000000 1000000 1000000

x mol mol

                      

   

O2int

0.209820 0.000375 0.206 17.22 1

1000

x mol mol - = =

+

CO2int

0.000375 1000 0.369 17.22 1

1000

x mmol mol   



H2Ointdry

16.93 17.22 16.93 1

1000

x = = mmol mol

-

CO2dil

0.375 0.371 12.01 1

1000

x = = mmol mol

+

H2Odildry

11.87 =12.01 11.87 1

1000

x = mmol mol

-

COdry

29.0 = 29.3 8.601 1

1000

x = mmol mol

-
CO2dry

24.98 = 25.2 8.601 1

1000

x = mmol mol

-

NOdry

50.0 = 50.4 8.601 1

1000

x = mmol mol

-

NO2dry

12.0 = 12.1 8.601 1

1000

x = mmol mol

-

THCdry

46 = 47.6 34.16 1

1000

x = mmol mol

-

 = 1.8 

 = 0.05 

 = 0.0003

= 0.0001 

(d) Carbon mass fraction and fuel composition. Determine carbon mass fraction of fuel, wc, and 

fuel composition of α, β, γ, and δ using one of the following methods: 

(1) You may calculate wc as described in this paragraph (d)(1) based on measured fuel 

properties. To do so, you must determine values for  and  in all cases, but you may set  and 

to zero if the default value listed in Table 1 of this section is zero. Calculate wc using the 

following equation: 

C

c

C H OS N

1

1

M w M   M MMM       

Eq. 1065.655-19 

Where: 

wc = carbon mass fraction of fuel.

MC = molar mass of carbon. 

 = atomic hydrogen-to-carbon ratio of the mixture of fuel(s) being combusted, weighted by 

molar consumption. 

MH = molar mass of hydrogen. 

 = atomic oxygen-to-carbon ratio of the mixture of fuel(s) being combusted, weighted by molar 

consumption. 

MO = molar mass of oxygen. 

 = atomic sulfur-to-carbon ratio of the mixture of fuel(s) being combusted, weighted by molar 

consumption. 
MS = molar mass of sulfur. 

 = atomic nitrogen-to-carbon ratio of the mixture of fuel(s) being combusted, weighted by 

molar consumption. 

MN = molar mass of nitrogen. 

Example:

 = 1.8 

 = 0.05 

 = 0.0003

= 0.0001 

MC = 12.0107 
MH = 1.00794

MO = 15.9994 

MS = 32.065 

MN = 14.0067 

c

1 12.0107

1 12.0107 1.8 1.00794 0.05 15.9994 0.0003 32.065 0.0001 14.0067 w          

wc = 0.8206

(2) Determine a fuel’s elemental mass fractions and values for α, β, γ, and δ as follows: 

(i) For gaseous fuels, use good engineering judgment to determine the fuel carbon, hydrogen, 

oxygen, nitrogen, and sulfur mass fractions. 

(ii) Determine mass fractions for liquid fuels as follows:

(A) You may determine the fuel carbon and hydrogen mass fractions according to ASTM D5291

(incorporated by reference in §1065.1010). When using ASTM D5291 to determine carbon and 

hydrogen mass fractions from gasoline (with or without blended ethanol), use good engineering 

judgment to adapt the method as appropriate.

(B) Determine oxygen mass fraction for gasoline (with or without blended ethanol) according to

ASTM D5599 (incorporated by reference in §1065.1010). For all other liquid fuels, determine 

the oxygen mass fraction using good engineering judgment.

(C) Determine the nitrogen mass fraction according to ASTM D4629 or ASTM D5762

(incorporated by reference in §1065.1010) for all liquid fuels. Select the correct method based

on the expected nitrogen content.

(D) Determine the sulfur mass fraction according to subpart H of this part.

(iii) For all fuels, use the default values for α, β, γ, and δ in Table 1 of this section in combination 

with measured values, or calculate them using the following equations:

H C

C H

w M

w M

    

 Eq. 1065.655-20

O C

C O

w M

w M    

 Eq. 1065.655-21

S C

C S

w M

w M    

 Eq. 1065.655-22

N C

C N

w M

w M

   

 Eq. 1065.655-23

Where:

wC = carbon mass fraction of fuel.

wH = hydrogen mass fraction of fuel.

wO = oxygen mass fraction of fuel.

wS = sulfur mass fraction of fuel.

wN = nitrogen mass fraction of fuel.

Deleted: 01

Comment [CAL9]: Example updated. 

Deleted: 8205
Example:

wC = 0.8206

wH = 0.1239

wO = 0.0547

wS = 0.00066() You may use the default values in the following table to determine α, β, γ, δ, and

wc for a given fuel: 

Table 1 of §1065.655–Default values of , , , , and wc, for various fuels 

Fuel 

Atomic hydrogen, 

oxygen, sulfur, and 

nitrogen-to-carbon ratios 

CHαOβSN

Carbon mass 

fraction, wc

g/g 

Gasoline CH1.85O0S0N0 0.866 

E10 Gasoline CH1.92O0.03S0N0 0.833 

E15 Gasoline CH1.95O0.05S0N0 0.817 

E85 Gasoline CH2.73O0.38S0N0 0.576 

#1 Diesel CH1.93O0S0N0 0.861 

#2 Diesel CH1.80O0S0N0 0.869 

Liquefied petroleum gas CH2.64O0S0N0 0.819 

Natural gas CH3.78 O0.016S0N0 0.747 

E100 Ethanol CH3O0.5S0N0 0.521 

M100 Methanol CH4O1S0N0 0.375 

Residual fuel blends Must be determined by measured fuel properties as 

described in paragraph (d)(1) of this section. 

(e) Calculated raw exhaust molar flow rate from measured intake air molar flow rate or fuel mass 

flow rate. You may calculate the raw exhaust molar flow rate from which you sampled 

emissions, exh n , based on the measured intake air molar flow rate, int n , or the measured fuel mass 

flow rate, mfuel  , and the values calculated using the chemical balance in paragraph (c) of this 

section. The chemical balance must be based on raw exhaust gas concentrations. Solve for the 

chemical balance in paragraph (c) of this section at the same frequency that you update and 

record int n or mfuel  . For laboratory tests, calculating raw exhaust molar flow rate using measured 

fuel mass flow rate is valid only for steady-state testing. See §1065.915(d)(5)(iv) for application 

to field testing.

(1) Crankcase flow rate. If engines are not subject to crankcase controls under the standardsetting part, you may calculate raw exhaust flow based on int n or mfuel  using one of the following: 

(i) You may measure flow rate through the crankcase vent and subtract it from the calculated 

exhaust flow. 

(ii) You may estimate flow rate through the crankcase vent by engineering analysis as long as the 

uncertainty in your calculation does not adversely affect your ability to show that your engines 

comply with applicable emission standards. 

(iii) You may assume your crankcase vent flow rate is zero. 

Deleted: 2

Deleted: 

Deleted: P

Deleted: G

Deleted: Note that t
(2) Intake air molar flow rate calculation. Based on int n , calculate exh n as follows: 

 

 

int

exh

int/exhdry raw/exhdry

H2Oexhdry

1

1

n n x x

x

      

  

 

Eq. 1065.655-24

Where: 

exh n = raw exhaust molar flow rate from which you measured emissions. 

int n = intake air molar flow rate including humidity in intake air. 

Example:

int n = 3.780 mol/s 

xint/exhdry = 0.69021 mol/mol 

xraw/exhdry = 1.10764 mol/mol 

xH20exhdry = 107.64 mmol/mol = 0.10764 mol/mol 

 

 

exh

3.780

0.69021 1.10764

1

1 0.10764

n       

  



exh n = 6.066 mol/s 

(3) Fuel mass flow rate calculation. This calculation may only be used for steady-state 

laboratory testing. See §1065.915(d)(5)(iv) for application to field testing. Based on mfuel  , 

calculate exh n as follows: 

fuel c H2Oexhdry   exh

c Ccombdry

mw x 1 n M x

   

 

Eq. 1065.655-25

Where: 

exh n = raw exhaust molar flow rate from which you measured emissions. 

mfuel  = fuel flow rate including humidity in intake air. 

Example:

mfuel  = 7.559 g/s 

wc = 0.869 g/g 

MC = 12.0107 g/mol 

xCcombdry = 99.87 mmol/mol = 0.09987 mol/mol 

xH20exhdry = 107.64 mmol/mol = 0.10764 mol/mol 

  exh

7.559 0.869 1 0.10764

12.0107 0.09987 n     

exh n = 6.066 mol/s 

Deleted: 20

Deleted: 21
(f) Calculated raw exhaust molar flow rate from measured intake air molar flow rate, dilute 

exhaust molar flow rate, and dilute chemical balance. You may calculate the raw exhaust molar 

flow rate, nexh  , based on the measured intake air molar flow rate, nint  , the measured dilute 

exhaust molar flow rate, dexh n , and the values calculated using the chemical balance in paragraph 

(c) of this section. Note that the chemical balance must be based on dilute exhaust gas 

concentrations. For continuous-flow calculations, solve for the chemical balance in paragraph 

(c) of this section at the same frequency that you update and record int n and dexh n . This 

calculated dexh n may be used for the PM dilution ratio verification in §1065.546; the calculation 

of dilution air molar flow rate in the background correction in §1065.667; and the calculation of 

mass of emissions in §1065.650(c) for species that are measured in the raw exhaust. 

(1) Crankcase flow rate. If engines are not subject to crankcase controls under the standardsetting part, calculate raw exhaust flow as described in paragraph (e)(1) of this section. 

(2) Dilute exhaust and intake air molar flow rate calculation. Calculate exh n as follows: 

n x x x nn   exh raw/exhdry int/exhdry H2Oexh dexh int        1 

Eq. 1065.655-26

Example:

int n  7.930 mol/s

raw/exhdry x  0.1544 mol/mol

0.1451mol/mol xint/exhdry 

H2Oexh x   32.46 mmol/mol 0.03246 mol/mol

dexh n  49.02 mol/s

nexh         0.1544 0.1451 1 0.03246 49.02 7.930 0.4411 7.930 8.371 mol/s   

(g) Calculated brake torque from fuel mass rate determined by a chemical balance of exhaust, 

measured engine speed, and brake-specific fuel consumption. If the standard-setting part allows 

it, you may calculate brake torque from fuel mass flow rate, as determined by a chemical balance 

of exhaust and measured exhaust flow rate, along with measured engine speed, and a brakespecific fuel consumption, as follows:

(1) Use the following equation to calculate brake torque, T:

fuel

n fuel

m T

f e  



Eq. 1065.655-27

Where:

mfuel  = mass rate of fuel

fn = engine speed

efuel = brake-specific fuel consumption

Example:

mfuel  = 3.32 g/s

fn = 3600 r/min

efuel = 253.61 g/(kW·hr)

Deleted: 22

Comment [CAL10]: How is this determined? 
Cp = 1000 (N·m·rad/s)/kW

Ct1 = 60 s/min

Ct2 = 3600 s/hr

Crev = 2·π rad/r

3.320 1000 60 3600

3600 253.61 2 3.14159

125.0 N m

T

T

    

 

(2) Use the following equation to calculate mass rate of fuel, mfuel  , from a chemical balance of 

exhaust and measured exhaust flow rate:

 

C Ccombdry exh

fuel

C H20exhdry 1

M x n m w x    

 

Eq. 1065.655-28

Example:

Mc = 12.0107 g/mol

xCcombdry = 99.87 mmol/mol = 0.09987 mol/mol

exh n = 2.665 mol/s

wc = 0.869 g/g

xH20exhdry = 107.64 mmol/mol = 0.10764 mol/mol

  fuel

12.0107 0.09987 2.665

0.869 1 0.10764 m      

fuel m  3.32 g/s

§1065.659 Removed water correction. 

(a) If you remove water upstream of a concentration measurement, x, correct for the removed 

water. Perform this correction based on the amount of water at the concentration measurement, 

xH2O[emission]meas, and at the flow meter, xH2Oexh, whose flow is used to determine the mass 

emission rate or total mass over a test interval. For continuous analyzers downstream of a 

sample dryer for transient and ramped-modal cycles, you must apply this correction on a 

continuous basis over the test interval, even if you use one of the options in §1065.145(e)(2) that 

results in a constant value for xH2O[emission]meas because xH2Oexh varies over the test interval. For 

batch analyzers, determine the flow-weighted average based on the continuous xH2Oexh values 

determined as described in paragraph (c) of this section. For batch analyzers, you may determine 

the flow-weighted average xH2Oexh based on a single value of xH2Oexh determined as described in 

paragraphs (c)(2) and (3) of this section, using flow-weighted average or batch concentration 

inputs. 

(b) Determine the amount of water remaining downstream of a sample dryer and at the 

concentration measurement using one of the methods described in §1065.145(e)(2). If you use a 

sample dryer upstream of an analyzer and if the calculated amount of water remaining 

downstream of the sample dryer and at the concentration measurement, xH2O[emission]meas, is higher 

than the amount of water at the flow meter, xH2Oexh, set xH2O[emission]meas equal to xH2Oexh. If you 

use a sample dryer upstream of storage media, you must be able to demonstrate that the sample 

Deleted: or upstream of a flow measurement, n, 
dryer is removing water continuously (i.e., xH2Oexh is higher than xH2O[emission]meas throughout the 

test interval). 

(c) For a concentration measurement where you did not remove water, you may set 

xH2O[emission]meas equal to xH2Oexh. You may determine the amount of water at the flow meter, 

xH2Oexh, using any of the following methods: 

(1) Measure the dewpoint and absolute pressure and calculate the amount of water as described 

in §1065.645. 

(2) If the measurement comes from raw exhaust, you may determine the amount of water based 

on intake-air humidity, plus a chemical balance of fuel, intake air, and exhaust as described in 

§1065.655. 

(3) If the measurement comes from diluted exhaust, you may determine the amount of water 

based on intake-air humidity, dilution air humidity, and a chemical balance of fuel, intake air, 

and exhaust as described in §1065.655. 

(d) Perform a removed water correction to the concentration measurement using the following 

equation: 

H2Oexh

[emission]meas

H2O[emission]meas

1

1

x x x x

        

Eq. 1065.659-1 

Example:

xCOmeas = 29.0 μmol/mol 

xH2OCOmeas = 8.601 mmol/mol = 0.008601 mol/mol 

xH2Oexh = 34.04 mmol/mol = 0.03404 mol/mol 

CO

1 0.03404 29.0

1 0.008601 x         

xCO = 28.3 μmol/mol 

§1065.660 THC, NMHC, and CH4 determination. 

(a) THC determination and initial THC/CH4 contamination corrections. (1) If we require you to 

determine THC emissions, calculate xTHC[THC-FID]cor using the initial THC contamination 

concentration xTHC[THC-FID]init from §1065.520 as follows: 

xTHC[THC-FID]cor = xTHC[THC-FID]uncor – xTHC[THC-FID]init

Eq. 1065.660-1 

Example:

xTHCuncor = 150.3 μmol/mol 

xTHCinit = 1.1 μmol/mol 

xTHCcor = 150.3 – 1.1 

xTHCcor = 149.2 μmol/mol 

(2) For the NMHC determination described in paragraph (b) of this section, correct xTHC[THC-FID]

for initial THC contamination using Equation 1065.660-1. You may correct xTHC[NMC-FID] for 

initial contamination of the CH4 sample train using Equation. 1065.660-1, substituting in CH4

concentrations for THC. 

(3) For the CH4 determination described in paragraph (c) of this section, you may correct

xTHC[NMC-FID] for initial THC contamination of the CH4 sample train using Equation 1065.660-1, 
substituting in CH4 concentrations for THC. 

(b) NMHC determination. Use one of the following to determine NMHC concentration, xNMHC: 

(1) If you do not measure CH4, you may omit the calculation of NMHC concentrations and 

calculate the mass of NMHC as described in §1065.650(c)(5). 

(2) For nonmethane cutters, calculate xNMHC using the nonmethane cutter’s penetration fraction 

(PF) of CH4 and the response factor penetration fraction (RFPF) of C2H6 from §1065.365, the 

response factor (RF) of the THC FID to CH4 from §1065.360, the initial THC contamination and 

dry-to-wet corrected THC concentration xTHC[THC-FID]cor as determined in paragraph (a) of this 

section, and the dry-to-wet corrected CH4 concentration xTHC[NMC-FID]cor optionally corrected for 

initial THC contamination as determined in paragraph (a) of this section. 

(i) Use the following equation for penetration fractions determined using an NMC configuration 

as outlined in §1065.365(d): 

THC[THC-FID]cor THC[NMC-FID]cor CH4[THC-FID]

NMHC

C2H6[NMC-FID] CH4[THC-FID] 1

x x RF x RFPF RF    

Eq. 1065.660-2 

Where: 

xNMHC = concentration of NMHC. 

xTHC[THC-FID]cor = concentration of THC, initial THC contamination and dry-to-wet corrected, as 

measured by the THC FID during sampling while bypassing the NMC. 

xTHC[NMC-FID]cor = concentration of THC, initial THC contamination (optional) and dry-to-wet 

corrected, as measured by the NMC FID during sampling through the NMC. 

RFCH4[THC-FID] = response factor of THC FID to CH4, according to §1065.360(d). 

RFPFC2H6[NMC-FID] = nonmethane cutter combined ethane response factor and penetration 

fraction, according to §1065.365(d). 

Example:

xTHC[THC-FID]cor = 150.3 μmol/mol 

xTHC[NMC-FID]cor = 20.5 μmol/mol 

RFPFC2H6[NMC-FID] = 0.019 

RFCH4[THC-FID] = 1.05 

NMHC

150.3 20.5 1.05

1 0.019 1.05 x     

xNMHC = 131.4 μmol/mol 

(ii) For penetration fractions determined using an NMC configuration as outlined in section 

§1065.365(e), use the following equation: 

THC[THC-FID]cor CH4[NMC-FID] THC[NMC-FID]cor

NMHC

CH4[NMC-FID] C2H6[NMC-FID]

x PF x x PF PF   

Eq. 1065.660-3 

Where: 

xNMHC = concentration of NMHC. 

xTHC[THC-FID]cor = concentration of THC, initial THC contamination and dry-to-wet corrected, as 

measured by the THC FID during sampling while bypassing the NMC. 

PFCH4[NMC-FID] = nonmethane cutter CH4 penetration fraction, according to §1065.365(e). 
xTHC[NMC-FID]cor = concentration of THC, initial THC contamination (optional) and dry-to-wet 

corrected, as measured by the THC FID during sampling through the NMC. 

PFC2H6[NMC-FID] = nonmethane cutter ethane penetration fraction, according to §1065.365(e). 

Example: 

xTHC[THC-FID]cor = 150.3 μmol/mol 

PFCH4[NMC-FID] = 0.990 

xTHC[NMC-FID]cor = 20.5 μmol/mol 

PFC2H6[NMC-FID] = 0.020 

NMHC

150.3 0.990 20.5

0.990 0.020 x    

xNMHC = 132.3 μmol/mol 

(iii) For penetration fractions determined using an NMC configuration as outlined in section 

§1065.365(f), use the following equation: 

THC[THC-FID]cor CH4[NMC-FID] THC[NMC-FID]cor CH4[THC-FID]

NMHC

CH4[NMC-FID] C2H6[NMC-FID] CH4[THC-FID]

x PF x RF x PF RFPF RF    

Eq. 1065.660-4 

Where: 

xNMHC = concentration of NMHC. 

xTHC[THC-FID]cor = concentration of THC, initial THC contamination and dry-to-wet corrected, as 

measured by the THC FID during sampling while bypassing the NMC. 

PFCH4[NMC-FID] = nonmethane cutter CH4 penetration fraction, according to §1065.365(f). 

xTHC[NMC-FID]cor = concentration of THC, initial THC contamination (optional) and dry-to-wet 

corrected, as measured by the THC FID during sampling through the NMC. 

RFPFC2H6[NMC-FID] = nonmethane cutter CH4 combined ethane response factor and penetration 

fraction, according to §1065.365(f). 

RFCH4[THC-FID] = response factor of THC FID to CH4, according to §1065.360(d). 

Example: 

xTHC[THC-FID]cor = 150.3 μmol/mol 

PFCH4[NMC-FID] = 0.990 

xTHC[NMC-FID]cor = 20.5 μmol/mol 

RFPFC2H6[NMC-FID] = 0.019 

RFCH4[THC-FID] = 0.980 

NMHC

150.3 0.990 20.5 0.980

0.990 0.019 0.980 x     

xNMHC = 132.5 μmol/mol 

(3) For a GC-FID, calculate xNMHC using the THC analyzer’s response factor (RF) for CH4, from 

§1065.360, and the initial THC contamination and dry-to-wet corrected THC concentration 

xTHC[THC-FID]cor as determined in paragraph (a) of this section as follows: 

NMHC THC[THC-FID]cor CH4[THC-FID] CH4 x   x RF x

Eq. 1065.660-5 

Where: 

xNMHC = concentration of NMHC. 
xTHC[THC-FID]cor = concentration of THC, initial THC contamination and dry-to-wet corrected, as 

measured by the THC FID. 

xCH4= concentration of CH4, dry-to-wet corrected, as measured by the GC-FID. 

RFCH4[THC-FID] = response factor of THC-FID to CH4. 

Example:

xTHC[THC-FID[cor = 145.6 μmol/mol 

RFCH4[THC-FID] = 0.970 

xCH4 = 18.9 μmol/mol 

xNMHC = 145.6 – 0.970 · 18.9 

xNMHC = 127.3 μmol/mol 

(c) CH4 determination. Use one of the following methods to determine CH4 concentration, xCH4: 

(1) For nonmethane cutters, calculate xCH4 using the nonmethane cutter’s penetration fraction 

(PF) of CH4 and the response factor penetration fraction (RFPF) of C2H6 from §1065.365, the 

response factor (RF) of the THC FID to CH4 from §1065.360, the initial THC contamination and 

dry-to-wet corrected THC concentration xTHC[THC-FID]cor as determined in paragraph (a) of this 

section, and the dry-to-wet corrected CH4 concentration xTHC[NMC-FID]cor optionally corrected for 

initial THC contamination as determined in paragraph (a) of this section. 

(i) Use the following equation for penetration fractions determined using an NMC configuration 

as outlined in §1065.365(d): 

THC[NMC-FID]cor THC[THC-FID]cor C2H6[NMC-FID]

CH4

C2H6[NMC-FID] CH4[THC-FID] 1

x x RFPF x RFPF RF    

Eq. 1065.660-6 

Where: 

xCH4 = concentration of CH4. 

xTHC[NMC-FID]cor = concentration of THC, initial THC contamination (optional) and dry-to-wet 

corrected, as measured by the NMC FID during sampling through the NMC. 

xTHC[THC-FID]cor = concentration of THC, initial THC contamination and dry-to-wet corrected, as 

measured by the THC FID during sampling while bypassing the NMC. 

RFPFC2H6[NMC-FID] = the combined ethane response factor and penetration fraction of the 

nonmethane cutter, according to §1065.365(d). 

RFCH4[THC-FID] = response factor of THC FID to CH4, according to §1065.360(d). 

Example:

xTHC[NMC-FID]cor = 10.4 μmol/mol 

xTHC[THC-FID]cor = 150.3 μmol/mol 

RFPFC2H6[NMC-FID] = 0.019 

RFCH4[THC-FID] = 1.05 

CH4

10.4 150.3 0.019

1 0.019 1.05 x     

xCH4 = 7.69 μmol/mol 
(ii) For penetration fractions determined using an NMC configuration as outlined in 

§1065.365(e), use the following equation: 

 

THC[NMC-FID]cor THC[THC-FID]cor C2H6[NMC-FID]

CH4

CH4[THC-FID] CH4[NMC-FID] C2H6[NMC-FID]

x x PF x RF PF PF    

Eq. 1065.660-7 

Where: 

xCH4 = concentration of CH4. 

xTHC[NMC-FID]cor = concentration of THC, initial THC contamination (optional) and dry-to-wet 

corrected, as measured by the NMC FID during sampling through the NMC. 

xTHC[THC-FID]cor = concentration of THC, initial THC contamination and dry-to-wet corrected, as 

measured by the THC FID during sampling while bypassing the NMC. 

PFC2H6[NMC-FID] = nonmethane cutter ethane penetration fraction, according to §1065.365(e). 

RFCH4[THC-FID] = response factor of THC FID to CH4, according to §1065.360(d). 

PFCH4[NMC-FID] = nonmethane cutter CH4 penetration fraction, according to §1065.365(e). 

Example: 

xTHC[NMC-FID]cor = 10.4 μmol/mol 

xTHC[THC-FID]cor = 150.3 μmol/mol 

PFC2H6[NMC-FID] = 0.020 

RFCH4[THC-FID] = 1.05 

PFCH4[NMC-FID] = 0.990 

  CH4

10.4 150.3 0.020

1.05 0.990 0.020 x     

xCH4 = 7.25 μmol/mol 

(iii) For penetration fractions determined using an NMC configuration as outlined in 

§1065.365(f), use the following equation: 

THC[NMC-FID]cor THC[THC-FID]cor C2H6[NMC-FID]

CH4

CH4[NMC-FID] C2H6[NMC-FID] CH4[THC-FID]

x x RFPF x PF RFPF RF    

Eq. 1065.660-8 

Where: 

xCH4 = concentration of CH4. 

xTHC[NMC-FID]cor = concentration of THC, initial THC contamination (optional) and dry-to-wet 

corrected, as measured by the NMC FID during sampling through the NMC. 

xTHC[THC-FID]cor = concentration of THC, initial THC contamination and dry-to-wet corrected, as 

measured by the THC FID during sampling while bypassing the NMC. 

RFPFC2H6[NMC-FID] = the combined ethane response factor and penetration fraction of the 

nonmethane cutter, according to §1065.365(f). 

PFCH4[NMC-FID] = nonmethane cutter CH4 penetration fraction, according to §1065.365(f). 

RFCH4[THC-FID] = response factor of THC FID to CH4, according to §1065.360(d). 

Example: 

xTHC[NMC-FID]cor = 10.4 μmol/mol 

xTHC[THC-FID]cor = 150.3 μmol/mol 

RFPFC2H6[NMC-FID] = 0.019 
PFCH4[NMC-FID] = 0.990 

RFCH4[THC-FID] = 1.05 

CH4

10.4 150.3 0.019

0.990 0.019 1.05 x     

xCH4 = 7.78 μmol/mol 

(2) For a GC-FID, xCH4 is the actual dry-to-wet corrected CH4 concentration as measured by the 

analyzer. 

§1065.665 THCE and NMHCE determination. 

(a) If you measured an oxygenated hydrocarbon's mass concentration, first calculate its molar 

concentration in the exhaust sample stream from which the sample was taken (raw or diluted 

exhaust), and convert this into a C1-equivalent molar concentration. Add these C1-equivalent 

molar concentrations to the molar concentration of nonoxygenated total hydrocarbon (NOTHC). 

The result is the molar concentration of total hydrocarbon equivalent (THCE). Calculate THCE 

concentration using the following equations, noting that Eq. 1065.665-3 is required only if you 

need to convert your oxygenated hydrocarbon (OHC) concentration from mass to moles: 

  THCE NOTHC OHCi OHCi-init

1

N

i

x x xx   

Eq. 1065.665-1 

NOTHC THC[THC-FID]cor OHCi OHCi-init OHCi[THC-FID]     1

N

i

x x x x RF    

Eq. 1065.665-2 

dexhOHCi

OHCi dexhOHCi

OHCi

dexh dexh

dexh

m

M n x m n

M

 

Eq. 1065.665-3 

Where: 

xTHCE = The sum of the C1-equivalent concentrations of non-oxygenated hydrocarbons, alcohols, 

and aldehydes. 

xNOTHC = The C1-equivalent sum of the concentration of NOTHC. 

xOHCi = The C1-equivalent concentration of oxygenated species i in diluted exhaust, not corrected 

for initial contamination. 

xOHCi-init = The C1-equivalent concentration of the initial system contamination (optional) of 

oxygenated species i, dry-to-wet corrected. 

xTHC[THC-FID]cor = The C1-equivalent response to NOTHC and all OHC in diluted exhaust, HC 

contamination and dry-to-wet corrected, as measured by the THC-FID. 

RFOHCi[THC-FID] = The response factor of the FID to species i relative to propane on a C1-

equivalent basis. 

C# = the mean number of carbon atoms in the particular compound. 

Mdexh = The molar mass of diluted exhaust as determine in §1065.340. 

mdexhOHCi = The mass of oxygenated species i in dilute exhaust. 

Deleted: equation 

Deleted: only 

Comment [CAL11]: Equation updated. 

Deleted: C1-equivalent 

Deleted: of carbon mass contributions 

Deleted: nonoxygenated 
MOHCi = The C1-equivalent molecular weight of oxygenated species i. 

mdexh = The mass of diluted exhaust 

ndexhOHCi = The number of moles of oxygenated species i in total diluted exhaust flow. 

ndexh = The total diluted exhaust flow. 

(b) If we require you to determine nonmethane hydrocarbon equivalent (NMHCE), use the 

following equation: 

xNMHCE = xTHCE – RFCH4[THC-FID]  xCH4

Eq. 1065.665-4 

Where: 

xNMHCE = The sum of the C1-equivalent concentrations of nonoxygenated nonmethane 

hydrocarbon (NONMHC), alcohols, and aldehydes. 

RFCH4[THC-FID] = response factor of THC-FID to CH4. 

xCH4 = concentration of CH4, HC contamination (optional) and dry-to-wet corrected, as measured 

by the gas chromatograph FID. 

(c) The following example shows how to determine NMHCE emissions based on ethanol 

(C2H5OH), methanol (CH3OH), acetaldehyde (C2H4O), and formaldehyde (HCHO) as C1-

equivalent molar concentrations: 

xTHC[THC-FID]cor = 145.6 μmol/mol 

xCH4 = 18.9 μmol/mol 

xC2H5OH = 100.8 μmol/mol 

xCH3OH = 1.1 μmol/mol 

xC2H4O = 19.1 μmol/mol 

xHCHO = 1.3 μmol/mol 

RFCH4[THC-FID] = 1.07 

RFC2H5OH[THC-FID] = 0.76 

RFCH3OH[THC-FID] = 0.74 

RFH2H4O[THC-FID] = 0.50 

RFHCHO[THC-FID] = 0.0 

xNMHCE = xTHC[THC-FID]cor – (xC2H5OH  RFC2H5OH[THC-FID] + xCH3OH  RFCH3OH[THC-FID] + xC2H4O 

RFC2H4O[THC-FID] + xHCHO  RFHCHO[THC-FID] + xC2H5OH + xCH3OH + xC2H4O + xHCHO – (RFCH4[THCFID]  xCH4) 

xNMHCE = 145.6 – (100.8 0.76 + 1.1  0.74 + 19.1  0.50 + 1.3  0+ 100.8 + 1.1 + 19.1 + 1.3 – 

(1.07  18.9) 

xNMHCE = 160.71 μmol/mol 

§1065.667 Dilution air background emission correction. 

(a) To determine the mass of background emissions to subtract from a diluted exhaust sample, 

first determine the total flow of dilution air, ndil, over the test interval. This may be a measured 

quantity or a calculated quantity. Multiply the total flow of dilution air by the mean mole 

fraction (i.e., concentration) of a background emission. This may be a time-weighted mean or a 

flow-weighted mean (e.g., a proportionally sampled background). Finally, multiply by the molar 

mass, M, of the associated gaseous emission constituent. The product of ndil and the mean molar 

concentration of a background emission and its molar mass, M, is the total background emission 

mass, m. In the case of PM, where the mean PM concentration is already in units of mass per 

Deleted: sum of the 

Deleted: of carbon mass contributions 

Deleted: -
mole of sample, MPM , multiply it by the total amount of dilution air flow, and the result is the 

total background mass of PM, mPM. Subtract total background mass from total mass to correct 

for background emissions. 

(b) You may determine the total flow of dilution air by a direct flow measurement. 

(c) You may determine the total flow of dilution air by subtracting the calculated raw exhaust 

molar flow as described in §1065.655(f) from the measured dilute exhaust flow. This may be 

done by totaling continuous calculations or by using batch results. 

(d) You may determine the total flow of dilution air from the measured dilute exhaust flow and a 

chemical balance of the fuel, intake air, and dilute exhaust as described in §1065.655. For this 

option, the molar flow of dilution air is calculated by multiplying the dilute exhaust flow by the 

mole fraction of dilution gas to dilute exhaust, dil/exh x , from the dilute chemical balance. This may 

be done by totaling continuous calculations or by using batch results. For example, to use batch 

results, the total flow of dilution air is calculated by multiplying the total flow of diluted exhaust, 

ndexh, by the flow-weighted mean mole fraction of dilution air in diluted exhaust, dil/exh x . 

Calculate dil/exh x using flow-weighted mean concentrations of emissions in the chemical balance, 

as described in §1065.655. The chemical balance in §1065.655 assumes that your engine 

operates stoichiometrically, even if it is a lean-burn engine, such as a compression-ignition 

engine. Note that for lean-burn engines this assumption could result in an error in emission 

calculations. This error could occur because the chemical balance in §1065.655 treats excess air 

passing through a lean-burn engine as if it was dilution air. If an emission concentration expected 

at the standard is about 100 times its dilution air background concentration, this error is 

negligible. However, if an emission concentration expected at the standard is similar to its 

background concentration, this error could be significant. If this error might affect your ability 

to show that your engines comply with applicable standards, we recommend that you either 

determine the total flow of dilution air using one of the more accurate methods in paragraph (b) 

or (c) of this section, or remove background emissions from dilution air by HEPA filtration, 

chemical adsorption, or catalytic scrubbing. You might also consider using a partial-flow 

dilution technique such as a bag mini-diluter, which uses purified air as the dilution air. 

(e) The following is an example of using the flow-weighted mean fraction of dilution air in 

diluted exhaust, dil/exh x , and the total mass of background emissions calculated using the total 

flow of diluted exhaust, ndexh, as described in §1065.650(c): 

m xm bkgnd dil/exh bkgnddexh  

Eq. 1065.667-1 

m Mx n bkgnddexh bkgnd dexh  

Eq. 1065.667-2 

Example:

MNOx = 46.0055 g/mol 

bkgnd x = 0.05 μmol/mol = 0.0510-6 mol/mol

ndexh = 23280.5 mol 

dil/exh x = 0.843 mol/mol 
6

bkgndNOxdexh m 46.0055 0.05 10 23280.5   

mbkgndNOxdexh = 0.0536 g 

mbkgndNOx = 0.843 · 0.0536 

mbkgndNOx = 0.0452 g 

(f) The following is an example of using the fraction of dilution air in diluted exhaust, xdil/exh, and 

the mass rate of background emissions calculated using the flow rate of diluted exhaust, dexh n , as 

described in §1065.650(c) : 

m xm   bkgnd dil/exh bkgnddexh  

Eq. 1065.667-3 

m Mx n   bkgnddexh bkgnd dexh  

Eq. 1065.667-4 

Example:

MNOx = 46.0055 g/mol 

xbkgnd = 0.05 μmol/mol = 0.0510-6 mol/mol 

dexh n = 23280.5 mol/s 

xdil/exh = 0.843 mol/mol 

6

bkgndNOxdexh m 46.0055 0.05 10 23280.5    

mbkgndNOxdexh  = 0.0536 g/hr 

mbkgndNOx  = 0.843 · 0.0536 

mbkgndNOx  = 0.0452 g/hr 

§1065.670 NOx intake-air humidity and temperature corrections. 

See the standard-setting part to determine if you may correct NOx emissions for the effects of 

intake-air humidity or temperature. Use the NOx intake-air humidity and temperature corrections 

specified in the standard-setting part instead of the NOx intake-air humidity correction specified 

in this part 1065. If the standard-setting part does not prohibit correcting NOx emissions for 

intake-air humidity according to this part 1065, correct NOx concentrations for intake-air 

humidity as described in this section. See §1065.650(c)(1) for the proper sequence for applying 

the NOx intake-air humidity and temperature corrections. You may use a time-weighted mean 

combustion air humidity to calculate this correction if your combustion air humidity remains 

within a tolerance of ±0.0025 mol/mol of the mean value over the test interval. For intake-air 

humidity correction, use one of the following approaches: 

(a) For compression-ignition engines, correct for intake-air humidity using the following 

equation: 

xNOxcor = xNOxuncor · (9.953 · xH2O + 0.832) 

Eq. 1065.670-1 

Example:

xNOxuncor = 700.5 μmol/mol 

xH2O = 0.022 mol/mol 

xNOxcor = 700.5 · (9.953 · 0.022 + 0.832) 
xNOxcor = 736.2 μmol/mol 

(b) For spark-ignition engines, correct for intake-air humidity using the following equation: 

xNOxcor = xNOxuncor · (18.840 · xH2O + 0.68094) 

Eq. 1065.670-2 

Example:

xNOxuncor = 154.7 μmol/mol 

xH2O = 0.022 mol/mol 

xNOxcor = 154.7 · (18.840 · 0.022 + 0.68094) 

xNOxcor = 169.5 μmol/mol 

(c) Develop your own correction, based on good engineering judgment. 

§1065.672 Drift correction. 

(a) Scope and frequency. Perform the calculations in this section to determine if gas analyzer 

drift invalidates the results of a test interval. If drift does not invalidate the results of a test 

interval, correct that test interval’s gas analyzer responses for drift according to this section. Use 

the drift-corrected gas analyzer responses in all subsequent emission calculations. Note that the 

acceptable threshold for gas analyzer drift over a test interval is specified in §1065.550 for both 

laboratory testing and field testing. 

(b) Correction principles. The calculations in this section utilize a gas analyzer’s responses to 

reference zero and span concentrations of analytical gases, as determined sometime before and 

after a test interval. The calculations correct the gas analyzer’s responses that were recorded 

during a test interval. The correction is based on an analyzer’s mean responses to reference zero 

and span gases, and it is based on the reference concentrations of the zero and span gases 

themselves. Validate and correct for drift as follows: 

(c) Drift validation. After applying all the other corrections–except drift correction–to all the gas 

analyzer signals, calculate brake-specific emissions according to §1065.650. Then correct all gas 

analyzer signals for drift according to this section. Recalculate brake-specific emissions using all 

of the drift-corrected gas analyzer signals. Validate and report the brake-specific emission 

results before and after drift correction according to §1065.550. 

(d) Drift correction. Correct all gas analyzer signals as follows: 

(1) Correct each recorded concentration, xi, for continuous sampling or for batch sampling, x . 

(2) Correct for drift using the following equation: 

   

  

i prezero postzero

idriftcorrected refzero refspan refzero

prespan postspan prezero postzero

2xx x x x xx xx xx

 

  

 

Eq. 1065.672-1 

Where: 

xidriftcorrected = concentration corrected for drift. 

xrefzero = reference concentration of the zero gas, which is usually zero unless known to be 

otherwise. 

xrefspan = reference concentration of the span gas. 

xprespan = pre-test interval gas analyzer response to the span gas concentration. 

xpostspan = post-test interval gas analyzer response to the span gas concentration. 

xi or x = concentration recorded during test, before drift correction. 
xprezero = pre-test interval gas analyzer response to the zero gas concentration. 

xpostzero = post-test interval gas analyzer response to the zero gas concentration. 

Example:

xrefzero = 0 μmol/mol 

xrefspan = 1800.0 μmol/mol 

xprespan = 1800.5 μmol/mol 

xpostspan = 1695.8 μmol/mol 

xi or x = 435.5 μmol/mol 

xprezero = 0.6 μmol/mol 

xpostzero = –5.2 μmol/mol 

    

     idriftcorrected

2 435.5 0.6 5.2

0 1800.0 0

1800.5 1695.8 0.6 5.2 x   

  

  

xidriftcorrected = 450.2 μmol/mol 

(3) For any pre-test interval concentrations, use concentrations determined most recently before 

the test interval. For some test intervals, the most recent pre-zero or pre-span might have 

occurred before one or more previous test intervals. 

(4) For any post-test interval concentrations, use concentrations determined most recently after 

the test interval. For some test intervals, the most recent post-zero or post-span might have 

occurred after one or more subsequent test intervals. 

(5) If you do not record any pre-test interval analyzer response to the span gas concentration, 

xprespan, set xprespan equal to the reference concentration of the span gas: xprespan = xrefspan. 

(6) If you do not record any pre-test interval analyzer response to the zero gas concentration, 

xprezero, set xprezero equal to the reference concentration of the zero gas: xprezero = xrefzero. 

(7) Usually the reference concentration of the zero gas, xrefzero, is zero: xrefzero = 0 μmol/mol. 

However, in some cases you might know that xrefzero has a non-zero concentration. For example, 

if you zero a CO2 analyzer using ambient air, you may use the default ambient air concentration 

of CO2, which is 375 μmol/mol. In this case, xrefzero = 375 μmol/mol. Note that when you zero 

an analyzer using a non-zero xrefzero, you must set the analyzer to output the actual xrefzero

concentration. For example, if xrefzero = 375 μmol/mol, set the analyzer to output a value of 375 

μmol/mol when the zero gas is flowing to the analyzer. 

§1065.675 CLD quench verification calculations. 

Perform CLD quench-check calculations as follows: 

(a) Perform a CLD analyzer quench verification test as described in §1065.370. 

(b) Estimate the maximum expected mole fraction of water during emission testing, xH2Oexp. 

Make this estimate where the humidified NO span gas was introduced in §1065.370(e)(6). When 

estimating the maximum expected mole fraction of water, consider the maximum expected water 

content in combustion air, fuel combustion products, and dilution air (if applicable). If you 

introduced the humidified NO span gas into the sample system upstream of a sample dryer 

during the verification test, you need not estimate the maximum expected mole fraction of water 

and you must set xH2Oexp equal to xH2Omeas. 

(c) Estimate the maximum expected CO2 concentration during emission testing, xCO2exp. Make 

this estimate at the sample system location where the blended NO and CO2 span gases are 

introduced according to §1065.370(d)(10). When estimating the maximum expected CO2
concentration, consider the maximum expected CO2 content in fuel combustion products and 

dilution air. 

(d) Calculate quench as follows: 

NOwet

H2Omeas H2Oexp CO2exp NOmeas

NOdry H2Omeas NOact CO2act

1 1 1 100 %

x

x x x x quench x xx x

          

            

   

Eq. 1065.675-1 

Where: 

quench = amount of CLD quench. 

xNOdry = concentration of NO upstream of a bubbler, according to §1065.370(e)(4). 

xNOwet = measured concentration of NO downstream of a bubbler, according to §1065.370(e)(9). 

xH2Oexp = maximum expected mole fraction of water during emission testing, according to 

paragraph (b) of this section. 

xH2Omeas = measured mole fraction of water during the quench verification, according to 

§1065.370(e)(7). 

xNOmeas = measured concentration of NO when NO span gas is blended with CO2 span gas, 

according to §1065.370(d)(10). 

xNOact = actual concentration of NO when NO span gas is blended with CO2 span gas, according 

to §1065.370(d)(11) and calculated according to Equation 1065.675-2. 

xCO2exp = maximum expected concentration of CO2 during emission testing, according to 

paragraph (c) of this section. 

xCO2act = actual concentration of CO2 when NO span gas is blended with CO2 span gas, according 

to §1065.370(d)(9). 

CO2act

NOact NOspan

CO2span

1 x x x x

 

   

 

Eq. 1065.675-2 

Where: 

xNOspan = the NO span gas concentration input to the gas divider, according to §1065.370(d)(5). 

xCO2span = the CO2 span gas concentration input to the gas divider, according to §1065.370(d)(4). 

Example:

xNOdry = 1800.0 μmol/mol 

xNOwet = 1739.6 μmol/mol 

xH2Oexp = 0.030 mol/mol 

xH2Omeas = 0.030 mol/mol 

xNOmeas = 1515.2 μmol/mol 

xNOspan = 3001.6 μmol/mol 

xCO2exp = 3.2 % 

xCO2span = 6.1 % 

xCO2act = 2.98 % 
NOact

2.98 1 3001.6 1535.24459 μmol/mol

6.1 x         

1739.6

1 0.030 0.030 1515.2 3.2 1 1 100 %

1800.0 0.030 1535.24459 2.98 quench

                       

   

quench = (–0.0036655 – 0.014020171)100 % = –1.7685671 % 

§1065.690 Buoyancy correction for PM sample media. 

(a) General. Correct PM sample media for their buoyancy in air if you weigh them on a balance. 

The buoyancy correction depends on the sample media density, the density of air, and the density 

of the calibration weight used to calibrate the balance. The buoyancy correction does not 

account for the buoyancy of the PM itself, because the mass of PM typically accounts for only 

(0.01 to 0.10) % of the total weight. A correction to this small fraction of mass would be at the 

most 0.010 %. 

(b) PM sample media density. Different PM sample media have different densities. Use the 

known density of your sample media, or use one of the densities for some common sampling 

media, as follows: 

(1) For PTFE-coated borosilicate glass, use a sample media density of 2300 kg/m3

. 

(2) For PTFE membrane (film) media with an integral support ring of polymethylpentene that 

accounts for 95 % of the media mass, use a sample media density of 920 kg/m3

. 

(3) For PTFE membrane (film) media with an integral support ring of PTFE, use a sample media 

density of 2144 kg/m3

. 

(c) Air density. Because a PM balance environment must be tightly controlled to an ambient 

temperature of (22 ±1) °C and humidity has an insignificant effect on buoyancy correction, air 

density is primarily a function of atmospheric pressure. Therefore you may use nominal constant 

values for temperature and humidity in the buoyancy correction equation in Eq. 1065.690-2. 

(d) Calibration weight density. Use the stated density of the material of your metal calibration 

weight. The example calculation in this section uses a density of 8000 kg/m3

, but you should 

know the density of your weight from the calibration weight supplier or the balance 

manufacturer if it is an internal weight. 

(e) Correction calculation. Correct the PM sample media for buoyancy using the following 

equations: 

air

weight

cor uncor

air

media

1

1

m m









    

  

      

Eq. 1065.690-1 

Where: 

mcor = PM mass corrected for buoyancy. 

muncor = PM mass uncorrected for buoyancy. 

air = density of air in balance environment. 

weight = density of calibration weight used to span balance. 
media = density of PM sample media, such as a filter. 

abs mix

air

amb

p M

R T    

Eq. 1065.690-2 

Where: 

pabs = absolute pressure in balance environment. 

Mmix = molar mass of air in balance environment. 

R = molar gas constant. 

Tamb = absolute ambient temperature of balance environment. 

Example:

pabs = 99.980 kPa 

Tsat = Tdew = 9.5 °C 

Using Eq. 1065.645-1, 

pH20 = 1.1866 kPa 

Using Eq. 1065.645-3, 

xH2O = 0.011868 mol/mol 

Using Eq. 1065.640-9, 

Mmix = 28.83563 g/mol 

R = 8.314472 J/(mol·K) 

Tamb = 20 °C 

air

99.980 28.83563

8.314472 293.15    

air = 1.18282 kg/m3

muncorr = 100.0000 mg 

weight = 8000 kg/m3

media = 920 kg/m3

cor

1.18282 1

8000 100.0000 1.18282 1

920

m

       

    

mcor = 100.1139 mg 

§1065.695 Data requirements. 

(a) To determine the information we require from engine tests, refer to the standard-setting part 

and request from your Designated Compliance Officer the format used to apply for certification 

or demonstrate compliance. We may require different information for different purposes, such 

as for certification applications, approval requests for alternate procedures, selective enforcement 

audits, laboratory audits, production-line test reports, and field-test reports. 

(b) See the standard-setting part and §1065.25 regarding recordkeeping. 

(c) We may ask you the following about your testing, and we may ask you for other information 

as allowed under the Act: 

(1) What approved alternate procedures did you use? For example: 
(i) Partial-flow dilution for proportional PM. 

(ii) CARB test procedures. 

(iii) ISO test procedures. 

(2) What laboratory equipment did you use? For example, the make, model, and description of 

the following: 

(i) Engine dynamometer and operator demand. 

(ii) Probes, dilution, transfer lines, and sample preconditioning components. 

(iii) Batch storage media (such as the bag material or PM filter material). 

(3) What measurement instruments did you use? For example, the make, model, and description 

of the following: 

(i) Speed and torque instruments. 

(ii) Flow meters. 

(iii) Gas analyzers. 

(iv) PM balance. 

(4) When did you conduct calibrations and performance checks and what were the results? For 

example, the dates and results of the following: 

(i) Linearity verification. 

(ii) Interference checks. 

(iii) Response checks. 

(iv) Leak checks. 

(v) Flow meter checks. 

(5) What engine did you test? For example, the following: 

(i) Manufacturer. 

(ii) Family name on engine label. 

(iii) Model. 

(iv) Model year. 

(v) Identification number. 

(6) How did you prepare and configure your engine for testing? Consider the following 

examples: 

(i) Dates, hours, duty cycle and fuel used for service accumulation. 

(ii) Dates and description of scheduled and unscheduled maintenance. 

(iii) Allowable pressure range of intake restriction. 

(iv) Allowable pressure range of exhaust restriction. 

(v) Charge air cooler volume. 

(vi) Charge air cooler outlet temperature, specified engine conditions and location of temperature 

measurement. 

(vii) Fuel temperature and location of measurement. 

(viii) Any aftertreatment system configuration and description. 

(ix) Any crankcase ventilation configuration and description (e.g., open, closed, PCV, crankcase 

scavenged).

(x) Number and type of preconditioning cycles.

(7) How did you test your engine? For example: 

(i) Constant speed or variable speed. 

(ii) Mapping procedure (step or sweep). 

(iii) Continuous or batch sampling for each emission. 

(iv) Raw or dilute sampling; any dilution-air background sampling. 

Deleted: checks
(v) Duty cycle and test intervals. 

(vi) Cold-start, hot-start, warmed-up running. 

(vii) Absolute pressure, temperature, and dewpoint of intake and dilution air. 

(viii) Simulated engine loads, curb idle transmission torque value. 

(ix) Warm-idle speed value. 

(x) Simulated vehicle signals applied during testing. 

(xi) Bypassed governor controls during testing. 

(xii) Date, time, and location of test (e.g., dynamometer laboratory identification). 

(xiii) Cooling medium for engine and charge air. 

(xiv) Operating temperatures of coolant, head, and block. 

(xv) Natural or forced cool-down and cool-down time. 

(xvi) Canister loading. 

(8) How did you validate your testing? For example, results from the following: 

(i) Duty cycle regression statistics for each test interval. 

(ii) Proportional sampling. 

(iii) Drift. 

(iv) Reference PM sample media in PM-stabilization environment. 

(9) How did you calculate results? For example, results from the following: 

(i) Drift correction. 

(ii) Noise correction. 

(iii) “Dry-to-wet” correction. 

(iv) NMHC, CH4, and contamination correction. 

(v) NOx humidity correction. 

(vi) Brake-specific emission formulation—total mass divided by total work, mass rate divided by 

power, or ratio of mass to work. 

(vii) Rounding emission results. 

(10) What were the results of your testing? For example: 

(i) Maximum mapped power and speed at maximum power. 

(ii) Maximum mapped torque and speed at maximum torque. 

(iii) For constant-speed engines: no-load governed speed. 

(iv) For constant-speed engines: test torque. 

(v) For variable-speed engines: maximum test speed. 

(vi) Speed versus torque map. 

(vii) Speed versus power map. 

(viii) Brake-specific emissions over the duty cycle and each test interval. 

(ix) Brake-specific fuel consumption. 

(11) What fuel did you use? For example: 

(i) Fuel that met specifications of subpart H of this part. 

(ii) Alternate fuel. 

(iii) Oxygenated fuel. 

(12) How did you field test your engine? For example: 

(i) Data from paragraphs (c)(1), (3), (4), (5), and (9) of this section. 

(ii) Probes, dilution, transfer lines, and sample preconditioning components. 

(iii) Batch storage media (such as the bag material or PM filter material). 

(iv) Continuous or batch sampling for each emission. 

(v) Raw or dilute sampling; any dilution air background sampling. 
(vi) Cold-start, hot-start, warmed-up running. 

(vii) Intake and dilution air absolute pressure, temperature, dewpoint. 

(viii) Curb idle transmission torque value. 

(ix) Warm idle speed value, any enhanced idle speed value. 

(x) Date, time, and location of test (e.g., identify the testing laboratory). 

(xi) Proportional sampling validation. 

(xii) Drift validation. 

(xiii) Operating temperatures of coolant, head, and block. 

(xiv) Vehicle make, model, model year, identification number. 
Subpart H—Engine Fluids, Test Fuels, Analytical Gases and Other Calibration Standards 

§1065.701 General requirements for test fuels. 

(a) General. For all emission measurements, use test fuels that meet the specifications in this 

subpart, unless the standard-setting part directs otherwise. Section 1065.10(c)(1) does not apply 

with respect to test fuels. Note that the standard-setting parts generally require that you design 

your emission controls to function properly when using commercially available fuels, even if 

they differ from the test fuel. Where we specify multiple grades of a certain fuel type (such as 

diesel fuel with different sulfur concentrations), see the standard-setting part to determine which 

grade to use.

(b) Fuels meeting alternate specifications. We may allow you to use a different test fuel (such as 

California Phase 2 gasoline) if it does not affect your ability to show that your engines would 

comply with all applicable emission standards using the fuel specified in this subpart. 

(c) Fuels not specified in this subpart. If you produce engines that run on a type of fuel (or 

mixture of fuels) that we do not specify in this subpart, you must get our written approval to 

establish the appropriate test fuel. See the standard-setting part for provisions related to fuels and 

fuel mixtures not specified in this subpart. 

(1) For engines designed to operate on a single fuel, we will generally allow you to use the fuel if 

you show us all the following things are true: 

(i) Show that your engines will use only the designated fuel in service. 

(ii) Show that this type of fuel is commercially available. 

(iii) Show that operating the engines on the fuel we specify would be inappropriate, as in the 

following examples: 

(A) The engine will not run on the specified fuel. 

(B) The engine or emission controls will not be durable or work properly when operating with 

the specified fuel. 

(C) The measured emission results would otherwise be substantially unrepresentative of in-use 

emissions. 

(2) For engines that are designed to operate on different fuel types, the provisions of paragraphs 

(c)(1)(ii) and (iii) of this section apply with respect to each fuel type. 

(3) For engines that are designed to operate on different fuel types as well as continuous mixtures 

of those fuels, we may require you to test with either the worst-case fuel mixture or the most 

representative fuel mixture, unless the standard-setting part specifies otherwise. 

(d) Fuel specifications. Specifications in this section apply as follows:

(1) Measure and calculate values as described in the appropriate reference procedure. Record 

and report final values expressed to at least the same number of decimal places as the applicable 

limit value. The right-most digit for each limit value is significant unless specified otherwise. 

For example, for a specified distillation temperature of 60 °C, determine the test fuel’s value to 

the nearest whole number. 

(2) The fuel parameters specified in this subpart depend on measurement procedures that are 

incorporated by reference. For any of these procedures, you may instead rely upon the 

procedures identified in 40 CFR part 80 for measuring the same parameter. For example, we 

may identify different reference procedures for measuring gasoline parameters in 40 CFR 80.46. 

(e) Two-stroke fuel/oil mixing. For two-stroke engines, use a fuel/oil mixture meeting the 

manufacturer’s specifications. 
(f) Service accumulation and field testing fuels. If we do not specify a service-accumulation or 

field-testing fuel in the standard-setting part, use an appropriate commercially available fuel such 

as those meeting minimum specifications from the following table: 

Table 1 of §1065.701–Examples of service-accumulation and field-testing fuels. 

Fuel category Subcategory Reference procedure1

Diesel 

Light distillate and light blends with 

residual ASTM D975 

Middle distillate ASTM D6985 

Biodiesel (B100) ASTM D6751 

Intermediate and residual fuel All See §1065.705 

Gasoline 

Motor vehicle gasoline ASTM D4814 

Motor gasoline with ethanol 

concentrations up to 10 volume %. ASTM D4814 

Alcohol Ethanol (E51-83) ASTM D5798 

Methanol (M70-M85) ASTM D5797 

Aviation fuel 

Aviation gasoline ASTM D910 

Gas turbine ASTM D1655 

Jet B wide cut ASTM D6615 

Gas turbine fuel General ASTM D2880 

1

ASTM specifications are incorporated by reference in §1065.1010.

§1065.703 Distillate diesel fuel. 

(a) Distillate diesel fuels for testing must be clean and bright, with pour and cloud points 

adequate for proper engine operation. 

(b) There are three grades of #2 diesel fuel specified for use as a test fuel. See the standardsetting part to determine which grade to use. If the standard-setting part does not specify which 

grade to use, use good engineering judgment to select the grade that represents the fuel on which 

the engines will operate in use. The three grades are specified in Table 1 of this section. 

(c) You may use the following nonmetallic additives with distillate diesel fuels: 

(1) Cetane improver. 

(2) Metal deactivator. 

(3) Antioxidant, dehazer. 

(4) Rust inhibitor. 

(5) Pour depressant. 

(6) Dye. 

(7) Dispersant. 

(8) Biocide. 

Deleted: -07b

Deleted: -04a

Deleted: -07b

Deleted: -07a

Deleted: Minor oxygenated gasoline blends

Deleted: -07a

Deleted: d75-85

Deleted: -07

Deleted: -07

Deleted: -07

Deleted: -07e01

Deleted: -06

Deleted: -03
Table 1 of §1065.703–Test fuel specifications for distillate diesel fuel 

Property Unit Ultra Low 

Sulfur 

Low 

Sulfur 

High 

Sulfur 

Reference 

Procedure1

Cetane Number — 40 - 50 40 - 50 40 - 50 ASTM D613 

Distillation range: 

Initial boiling point 

10 pct. point 

50 pct. point 

90 pct. point 

Endpoint 

°C 

171 - 204 

204 - 238 

243 - 282 

293 - 332 

321 - 366 

171 - 204 

204 - 238 

243 - 282 

293 - 332 

321 - 366 

171 - 204 

204 - 238 

243 - 282 

293 - 332 

321 - 366 

ASTM D86 

Gravity °API 32 - 37 32 - 37 32 - 37 ASTM D4052 

Total sulfur, ultra low sulfur mg/kg 7 – 15 See 40 CFR 80.580 

Total sulfur, low and high sulfur mg/kg 300 - 500 800 - 2500 ASTM D2622or 

alternates as allowed 

under 40 CFR 80.580 

Aromatics, min. (Remainder shall be 

paraffins, naphthenes, and olefins) 

g/kg 100 100 100 ASTM D5186 

Flashpoint, min. °C 54 54 54 ASTM D93 

Kinematic Viscosity cSt 2.0 - 3.2 2.0 - 3.2 2.0 - 3.2 ASTM D445 1

ASTM procedures are incorporated by reference in §1065.1010. See §1065.701(d) for other allowed procedures. 

§1065.705 Residual and intermediate residual fuel.

This section describes the specifications for fuels meeting the definition of residual fuel in 40 

CFR 80.2, including fuels marketed as intermediate fuel. Residual fuels for service 

accumulation and any testing must meet the following specifications: 

(a) The fuel must be a commercially available fuel that is representative of the fuel that will be 

used by the engine in actual use. 

(b) The fuel must meet the specifications for one of the categories in the following table:

Deleted: Item

Deleted: s

Deleted: -05

Deleted: -07a

Deleted: -96e01

Deleted: -07 

Deleted: al

Deleted: -03

Deleted: -09

Deleted: -09
Table 1 of §1065.705–Service accumulation and test fuel specifications for residual fuel. 

Property Unit 

Category ISO-FReference Procedure 1 RMA 

30 

RMB 

30 

RMD 

80 

RME 

180 

RMF 

180 

RMG 

380 

RMH 

380 

RMK 

380 

RMH 

700 

RMK 

700 

Density at 15 °C, max. kg/m3 960.0 975.0 980.0 991.0 991.0 1010.0 991.0 1010.0 

ISO 3675 or ISO 12185: 1996/Cor 1:2001 (see also ISO 8217:2005(E) 7.1) 

Kinematic viscosity at 50 °C, max. cSt 30.0 80.0 180.0 380.0 700.0 ISO 3104:1994/Cor 1:1997 Flash point, min. °C 60 60 60 60 60 ISO 2719 (see also ISO 8217:2005(E) 7.2) Pour point (upper) Winter quality, max. Summer quality, max. 

°C 0 

6 

24 24 

30 30 

30 30 

30 30 

30 30 

ISO 3016 ISO 3016 

Carbon residue, max. (kg/kg) % 10 14 15 20 18 22 22 ISO 10370:1993/Cor 1:1996 Ash, max. (kg/kg) % 0.10 0.10 0.10 0.15 0.15 0.15 ISO 6245 Water, max. (m3/m3) % 0.5 0.5 0.5 0.5 0.5 ISO 3733 Sulfur, max. (kg/kg) % 3.50 4.00 4.50 4.50 4.50 

ISO 8754 or ISO 14596: 1998/Cor 1:1999 (see also ISO 8217:2005(E) 7.3) 

Vanadium, max. mg/kg 150 350 200 500 300 600 600 

ISO 14597 or IP 501 or IP 47(see also ISO 8217:2005(E) 7.8) 

Total sediment potential, max. (kg/kg) % 0.10 0.10 0.10 0.10 0.10 ISO 10307-2 (see also ISO 8217:2005(E) 7.6) Aluminium plus silicon, max. mg/kg 80 80 80 80 80 

ISO 10478 or IP 501 or IP 47(see also ISO 8217:2005(E) 7.9) 

Used lubricating oil (ULO), max. Zinc Phosphorus Calcium 

mg/kg 

Fuel shall be free of ULO. We consider a fuel to be free of ULO if one or more of the elements zinc, phosphorus, or calcium is at or 

below the specified limits. We consider a fuel to contain ULO if all three elements exceed the specified limits. 

15 15 30 

IP 501 or IP 470 (see ISO 8217:2005(E) 7.7) IP 501 or IP 500 (see ISO 8217:2005(E) 7.7) IP 501 or IP 470 (see ISO 8217:2005(E) 7.7) 1ISO procedures are incorporated by reference in §1065.1010. See §1065.701(d) for other allowed procedures. 
§1065.710 Gasoline. 

(a) This section specifies test fuel properties for gasoline with ethanol (low-level blend only) and 

for gasoline without ethanol. Note that the “fuel type” for the fuels specified in paragraphs (b) 

and (c) of this section is considered to be gasoline. In contrast, fuels with higher ethanol 

concentrations, such as fuel containing 82 percent ethanol, are considered to be ethanol fuels 

rather than gasoline. We specify some test fuel parameters that apply uniquely for lowtemperature testing and for testing at altitudes above 1,219 m. For all other testing,, use the test 

fuel parameters specified for general testing. Unless the standard-setting part specifies 

otherwise, use the fuel specified in paragraph (c) of this section for general testing. 

(b) The following specifications apply for a blended gasoline test fuel that has nominally 15 % 

ethanol (commonly called E15 test fuel):

(1) Prepare the blended test fuel from typical refinery gasoline blending components. You may 

not use pure compounds, except as follows:

(i) You may use neat ethanol as a blendstock.

(ii) You may adjust the test fuel’s vapor pressure by adding butane.

(iii) You may adjust the test fuel’s benzene content by adding benzene.

(iv) You may adjust the test fuel’s sulfur content by adding sulfur compounds that are 

representative of those found with in-use fuels.

(2) Table 1 of this section identifies limit values consistent with the units in the reference 

procedure for each fuel property. These values are generally specified in international units. 

Values presented in parentheses are for information only. Table 1 follows:

Comment [CAL12]: AS: We might need to 

define the limit of what constitutes gasoline as a fuel 

type (if we haven’t already). 

Deleted: Gasoline for testing must have octane 

values that represent commercially available fuels 

for the appropriate application.¶

(b) There are two grades of gasoline specified for use 

as a test fuel. If the standard-setting part requires 

testing with fuel appropriate for low temperatures, 

use the test fuel specified for low-temperature 

testing. Otherwise

Deleted: The two grades are specified in Table 1 

of this section.
Table 1 of §1065.710–Test fuel specifications for a low-level ethanol-gasoline blend

Property Unit

SPECIFICATION

Reference 

Procedure1

General 

Testing

LowTemperature 

Testing

High Altitude 

Testing

Antiknock Index 

(R+M)/2 - 87.0 - 88.42 87.0 Minimum

ASTM D2699and 

D2700

Sensitivity (R-M) - 7.5 Minimum ASTM D2699 and 

D2700

Dry Vapor Pressure 

Equivalent (DVPE)

3 kPa (psi) 60.0-63.4 

(8.7-9.2)

77.2-81.4

(11.2-11.8)

52.4-55.2 

(7.6-8.0) ASTM D5191

Distillation

10% evaporated °C (°F) 49-60 (120-140)

43-54 

(110-130)

49-60

 (120-140)

ASTM D86

50% evaporated °C (°F) 77-88 (170-190)

90% evaporated °C (°F) 154-166 (310-330)

Evaporated final 

boiling point °C (°F) 193-216 (380-420)

Residue milliliter 2.0 Maximum

Total Aromatic 

Hydrocarbons volume % 19.5-24.5

ASTM D5769

C6 Aromatics 

(benzene) volume % 0.6-0.8

C7 Aromatics 

(toluene) volume % 4.4-5.5

C8 Aromatics volume % 5.5-6.9

C9 Aromatics volume % 5.0-6.2

C10+ Aromatics volume % 4.0-5.0

Olefins4 mass % 4.5-11.5 ASTM D6550

Ethanol blended5 volume % 14.6-15.0 Paragraph (b)(3) of 

this section.

Ethanol

confirmatory6,7 volume % 14.3-15.3 ASTM D5599

Total Content of 

Oxygenates Other 

than Ethanol7

volume % 0.1 Maximum ASTM D5599

Sulfur mg/kg 8.0-11.0 ASTM D2622, 

D5453 or D7039

Lead g/liter 0.0026 Maximum ASTM D3237

Phosphorus g/liter 0.0013 Maximum ASTM D3231

Copper Corrosion - No. 1 Maximum ASTM D130

Solvent-Washed Gum 

Content

mg/100 

milliliter 3.0 Maximum ASTM D381

Oxidation Stability minute 1000 Minimum ASTM D525

1

ASTM procedures are incorporated by reference in §1065.1010. See §1065.701(d) for other allowed 

procedures.

2

 Octane specifications apply only for testing related to exhaust emissions. For engines or vehicles that require 

the use of premium fuel, as described in paragraph (d) of this section, the adjusted specification for antiknock 

index is a minimum value of 91.0; no maximum value applies. All other specifications apply for this highoctane fuel.

3

 Calculate dry vapor pressure equivalent, DVPE, based on the measured total vapor pressure, pT, in kPa using 

the following equation: DVPE = 0.956·pT - 2.39. DVPE is intended to be equivalent to Reid Vapor Pressure 

Comment [CAL13]: Alan, please review. 
using a different test method.

4

 The specified olefin concentration range equates to approximately 4 – 10 volume % when measured according 

to ASTM D1319.

5

The ethanol blended specification is based on the volume % ethanol content of the fuel as determined during 

blending by the fuel supplier and supplied by the supplier at the time of fuel delivery.

6

The ethanol confirmatory specification is based on the volume % ethanol as measured according to ASTM 

D5599.

7

 The reference procedure prescribes measurement of ethanol concentration in mass %. Convert results to 

volume % as specified in ASTM D4815.

(3) Use good engineering judgment to determine the volume % of ethanol based on the volume 

of each blendstock. We recommend using a temperature compensated NIST traceable flow 

measurement device that has an accuracy and repeatability of ± 0.1%. Alternatively you may 

use a gravimetric method to calculate blendstock volumes, provided that you have equivalent 

accuracy and repeatability.

(c) The specifications of this paragraph (c) apply for testing with neat gasoline. This is 

sometimes called indolene or E0 test fuel. Gasoline for testing must have octane values that 

represent commercially available fuels for the appropriate application. Test fuel specifications 

apply as follows:

Table 2 of §1065.710–Test fuel specifications for neat (E0) gasoline 

Property Unit 

SPECIFICATION Reference 

Procedure1 General Testing Low-Temperature 

Testing 

Distillation Range: 

Evaporated initial boiling 

point 

10% evaporated

50% evaporated

90% evaporated

Evaporated final boiling 

point 

°C 

24 - 35 2 

49 - 57 

93 - 110 

149 - 163 

Maximum, 213 

24 - 36 

37 - 48 

82 - 101 

158 - 174 

Maximum, 212 

ASTM D86 

Hydrocarbon composition: 

Olefins 

Aromatics 

Saturates 

volume % Maximum, 0.10 

Maximum, 0.35 

Remainder 

Maximum, 0.175 

Maximum, 0.304 

Remainder 

ASTM D1319 

Lead g/liter Maximum, 0.013 Maximum, 0.013 ASTM D3237 

Phosphorous g/liter Maximum, 0.0013 Maximum, 0.005 ASTM D3231 

Total sulfur mg/kg Maximum, 80 Maximum, 80 ASTM D2622 

Dry vapor pressure 

equivalent kPa 60.0 - 63.42,3 77.2 - 81.4 ASTM D5191 

1

ASTM procedures are incorporated by reference in §1065.1010. See §1065.701(d) for other allowed procedures. 

2

For testing at altitudes above 1 219 m, the specified volatility range is (52.0 to 55.2) kPa and the specified initial boiling 

point range is (23.9 to 40.6) °C. 

3

For testing unrelated to evaporative emissions, the specified range is (55.2 to 63.4) kPa. 

(d) Use the high-octane gasoline specified in paragraph (b) of this section only for engines or 

vehicles for which the manufacturer conditions the warranty on the use of premium gasoline.

§1065.715 Natural gas. 

(a) Except as specified in paragraph (b) of this section, natural gas for testing must meet the 

specifications in the following table: 

Comment [CAL14]: Alan, please review. 

Comment [CAL15]: Alan, please review. 

Deleted: 1 

Deleted: Item

Deleted: s

Deleted: I

Deleted: point

Deleted: point

Deleted: point

Deleted: End 

Deleted: -07a

Deleted: m3/m3

Deleted: -03

Deleted: (organic)

Deleted: -06e01

Deleted: -07

Deleted: -07

Comment [CAL16]: Alan: Need footnote? 

Calculate dry vapor pressure equivalent, DVPE, 

based on the measured total vapor pressure, pT, in 

kPa using the following equation: DVPE = 0.956·pT - 

2.39. DVPE is intended to be equivalent to Reid 

Vapor Pressure using a different test method. 

Deleted: Volatility (Reid Vapor Pressure)

Deleted: -07
Table 1 of §1065.715–Test fuel specifications for natural gas 

Property Value1

Methane, CH4 Minimum, 0.87 mol/mol 

Ethane, C2H6 Maximum, 0.055 mol/mol 

Propane, C3H8 Maximum, 0.012 mol/mol 

Butane, C4H10 Maximum, 0.0035 mol/mol 

Pentane, C5H12 Maximum, 0.0013 mol/mol 

C6 and higher Maximum, 0.001 mol/mol 

Oxygen Maximum, 0.001 mol/mol 

Inert gases (sum of CO2 and N2) Maximum, 0.051 mol/mol 1

 Demonstrate compliance with fuel specifications based on the reference procedures in 

ASTM D1945 (incorporated by reference in §1065.1010), or on other measurement 

procedures using good engineering judgment. See §1065.701(d) for other allowed 

procedures. 

(b) In certain cases you may use test fuel not meeting the specifications in paragraph (a) of this 

section, as follows: 

(1) You may use fuel that your in-use engines normally use, such as pipeline natural gas. 

(2) You may use fuel meeting alternate specifications if the standard-setting part allows it. 

(3) You may ask for approval to use fuel that does not meet the specifications in paragraph (a) of 

this section, but only if using the fuel would not adversely affect your ability to demonstrate 

compliance with the applicable standards. 

(c) When we conduct testing using natural gas, we will use fuel that meets the specifications in 

paragraph (a) of this section. 

(d) At ambient conditions, natural gas must have a distinctive odor detectable down to a 

concentration in air not more than one-fifth the lower flammable limit. 

§1065.720 Liquefied petroleum gas. 

(a) Except as specified in paragraph (b) of this section, liquefied petroleum gas for testing must 

meet the specifications in the following table: 

Table 1 of §1065.720–Test fuel specifications for liquefied petroleum gas 

Property Value Reference Procedure1

Propane, C3H8 Minimum, 0.85 m3/m3 ASTM D2163 

Vapor pressure at 38 °C Maximum, 1400 kPa ASTM D1267or 25982

Volatility residue (evaporated temperature, 35 °C) Maximum, -38 °C ASTM D1837 

Butanes Maximum, 0.05 m3/m3 ASTM D2163 

Butenes Maximum, 0.02 m3/m3 ASTM D2163 

Pentenes and heavier Maximum, 0.005 m3/m3 ASTM D2163 

Propene Maximum, 0.1 m3/m3 ASTM D2163 

Residual matter (residue on evap. of 100) ml oil stain observ.) Maximum, 0.05 ml pass3 ASTM D2158 

Corrosion, copper strip Maximum, No. 1 ASTM D1838 

Sulfur Maximum, 80 mg/kg ASTM D2784 

Moisture content pass ASTM D2713 

1

ASTM procedures are incorporated by reference in §1065.1010. See §1065.701(d) for other allowed procedures. 

2

If these two test methods yield different results, use the results from ASTM D1267. 3

The test fuel must not yield a persistent oil ring when you add 0.3 ml of solvent residue mixture to a filter paper in 0.1 ml 

increments and examine it in daylight after two minutes. 

(b) In certain cases you may use test fuel not meeting the specifications in paragraph (a) of this 

section, as follows: 

Deleted: Item

Deleted: All parameters are 

Deleted: -03

Deleted: Item

Deleted: -05

Deleted: -02¶

Deleted: -02

Deleted: -02a

Deleted: -05

Deleted: -05

Deleted: -05

Deleted: -05

Deleted: -05

Deleted: -07

Deleted: -06

Deleted: -91

Deleted: -02
(1) You may use fuel that your in-use engines normally use, such as commercial-quality 

liquefied petroleum gas. 

(2) You may use fuel meeting alternate specifications if the standard-setting part allows it. 

(3) You may ask for approval to use fuel that does not meet the specifications in paragraph (a) of 

this section, but only if using the fuel would not adversely affect your ability to demonstrate 

compliance with the applicable standards. 

(c) When we conduct testing using liquefied petroleum gas, we will use fuel that meets the 

specifications in paragraph (a) of this section. 

(d) At ambient conditions, liquefied petroleum gas must have a distinctive odor detectable down 

to a concentration in air not more than one-fifth the lower flammable limit. 

§1065.725 High-level ethanol-gasoline blends.

For testing ethanol-fueled vehicles create a high-level ethanol-gasoline blend test fuel as follows:

(a) Add ethanol to an E15 fuel meeting the specifications described in §1065.710 until the 

ethanol content of the blended fuel is between 80 and 83 % by volume. 

(b) You may alternatively add ethanol to a gasoline base fuel with no ethanol if you can 

demonstrate that such a base fuel blended with the proper amount of ethanol would meet all the 

specifications for E15 test fuel described in §1065.710, other than the ethanol content.

(c) The ethanol used for blending must be either denatured ethanol meeting the specifications in 

40 CFR 80.1510, or fuel-grade ethanol with no denaturant. Be sure to account for the volume of 

any denaturant when calculating volumetric percentages.

(d) The blended test fuel must have a dry vapor pressure equivalent between 6.0 and 6.5 when 

measured using the applicable procedure specified in §1065.710. You may add commercial 

grade butane as needed to meet this specification.

§1065.740 Lubricants. 

(a) Use commercially available lubricating oil that represents the oil that will be used in your 

engine in use. 

(b) You may use lubrication additives, up to the levels that the additive manufacturer 

recommends. 

§1065.745 Coolants. 

(a) You may use commercially available antifreeze mixtures or other coolants that will be used 

in your engine in use. 

(b) For laboratory testing of liquid-cooled engines, you may use water with or without rust 

inhibitors. 

(c) For coolants allowed in paragraphs (a) and (b) of this section, you may use rust inhibitors and 

additives required for lubricity, up to the levels that the additive manufacturer recommends. 

§1065.750 Analytical Gases. 

Analytical gases must meet the accuracy and purity specifications of this section, unless you can 

show that other specifications would not affect your ability to show that you comply with all 

applicable emission standards. 

(a) Subparts C, D, F, and J of this part refer to the following gas specifications: 

Deleted: r engines
(1) Use purified gases to zero measurement instruments and to blend with calibration gases. Use 

gases with contamination no higher than the highest of the following values in the gas cylinder or 

at the outlet of a zero-gas generator: 

(i) 2 % contamination, measured relative to the flow-weighted mean concentration expected at 

the standard. For example, if you would expect a flow-weighted CO concentration of 100.0 

mol/mol, then you would be allowed to use a zero gas with CO contamination less than or 

equal to 2.000 mol/mol. 

(ii) Contamination as specified in the following table: 

Table 1 of §1065.750–General specifications for purified gases1

Constituent Purified Synthetic Air Purified N2

THC (C1 equivalent) ≤ 0.05 mol/mol ≤ 0.05 mol/mol 

CO ≤ 1 mol/mol ≤ 1 mol/mol 

CO2 ≤ 10 mol/mol ≤ 10 mol/mol 

O2 0.205 to 0.215 mol/mol ≤ 2 mol/mol 

NOx ≤ 0.02 mol/mol ≤ 0.02 mol/mol

N2O2 ≤ 0.02 mol/mol ≤ 0.02 mol/mol 1

We do not require these levels of purity to be NIST-traceable. 

2

The N2O limit applies only if the standard-setting part requires you to

report N2O or certify to an N2O standard. 

(2) Use the following gases with a FID analyzer: 

(i) FID fuel. Use FID fuel with a stated H2 concentration of (0.39 to 0.41) mol/mol, balance He

or N2, and a stated total hydrocarbon concentration of 0.05 mol/mol or less. For GC-FIDs that 

measure methane (CH4) using a FID fuel that is balance N2, perform the CH4 measurement as 

described in SAE J1151 (incorporated by reference in §1065.1010).

(ii) FID burner air. Use FID burner air that meets the specifications of purified air in paragraph 

(a)(1) of this section. For field testing, you may use ambient air. 

(iii) FID zero gas. Zero flame-ionization detectors with purified gas that meets the specifications 

in paragraph (a)(1) of this section, except that the purified gas O2 concentration may be any 

value. Note that FID zero balance gases may be any combination of purified air and purified 

nitrogen. We recommend FID analyzer zero gases that contain approximately the expected flowweighted mean concentration of O2 in the exhaust sample during testing. 

(iv) FID propane span gas. Span and calibrate THC FID with span concentrations of propane, 

C3H8. Calibrate on a carbon number basis of one (C1). For example, if you use a C3H8 span gas 

of concentration 200 mol/mol, span a FID to respond with a value of 600 mol/mol. Note that 

FID span balance gases may be any combination of purified air and purified nitrogen. We 

recommend FID analyzer span gases that contain approximately the flow-weighted mean 

concentration of O2 expected during testing. If the expected O2 concentration in the exhaust 

sample is zero, we recommend using a balance gas of purified nitrogen. 

(v) FID CH4 span gas. If you always span and calibrate a CH4 FID with a nonmethane cutter, 

then span and calibrate the FID with span concentrations of CH4. Calibrate on a carbon number 

basis of one (C1). For example, if you use a CH4 span gas of concentration 200 mol/mol, span 

a FID to respond with a value of 200 mol/mol. Note that FID span balance gases may be any 

combination of purified air and purified nitrogen. We recommend FID analyzer span gases that 

Deleted: 1

Deleted: 1

Deleted: 05 

Deleted: 05 

Deleted: methane

Deleted: methane, 
contain approximately the expected flow-weighted mean concentration of O2 in the exhaust 

sample during testing. If the expected O2 concentration in the exhaust sample is zero, we 

recommend using a balance gas of purified nitrogen. 

(3) Use the following gas mixtures, with gases traceable within ±1 % of the NIST-accepted value 

or other gas standards we approve: 

(i) CH4, balance purified synthetic air and/or N2 (as applicable). 

(ii) C2H6, balance purified synthetic air and/or N2 (as applicable). 

(iii) C3H8, balance purified synthetic air and/or N2 (as applicable). 

(iv) CO, balance purified N2. 

(v) CO2, balance purified N2. 

(vi) NO, balance purified N2. 

(vii)) NO2, balance purified synthetic air. 

(viii) O2, balance purified N2. 

(ix) C3H8, CO, CO2, NO, balance purified N2. 

(x) C3H8, CH4, CO, CO2, NO, balance purified N2. 

(xi) N2O, balance purified synthetic air and/or N2 (as applicable). 

(4) You may use gases for species other than those listed in paragraph (a)(3) of this section (such 

as methanol in air, which you may use to determine response factors), as long as they are 

traceable to within ±3 % of the NIST-accepted value or other similar standards we approve, and 

meet the stability requirements of paragraph (b) of this section. 

(5) You may generate your own calibration gases using a precision blending device, such as a 

gas divider, to dilute gases with purified N2 or purified synthetic air. If your gas divider meets

the specifications in §1065.248, and the gases being blended meet the requirements of 

paragraphs (a)(1) and (3) of this section, the resulting blends are considered to meet the 

requirements of this paragraph (a). 

(b) Record the concentration of any calibration gas standard and its expiration date specified by 

the gas supplier. 

(1) Do not use any calibration gas standard after its expiration date, except as allowed by 

paragraph (b)(2) of this section. 

(2) Calibration gases may be relabeled and used after their expiration date as follows: 

(i) Alcohol/carbonyl calibration gases used to determine response factors according to subpart I 

of this part may be relabeled as specified in subpart I of this part. 

(ii) Other gases may be relabeled and used after the expiration date only if we approve it in 

advance. 

(c) Transfer gases from their source to analyzers using components that are dedicated to 

controlling and transferring only those gases. For example, do not use a regulator, valve, or 

transfer line for zero gas if those components were previously used to transfer a different gas 

mixture. We recommend that you label regulators, valves, and transfer lines to prevent 

contamination. Note that even small traces of a gas mixture in the dead volume of a regulator, 

valve, or transfer line can diffuse upstream into a high-pressure volume of gas, which would 

contaminate the entire high-pressure gas source, such as a compressed-gas cylinder. 

(d) To maintain stability and purity of gas standards, use good engineering judgment and follow 

the gas standard supplier's recommendations for storing and handling zero, span, and calibration 

gases. For example, it may be necessary to store bottles of condensable gases in a heated 

environment. 

Deleted: s
§1065.790 Mass standards. 

(a) PM balance calibration weights. Use PM balance calibration weights that are certified as 

NIST-traceable within 0.1 % uncertainty. Calibration weights may be certified by any 

calibration lab that maintains NIST-traceability. Make sure your highest calibration weight has 

no greater than ten times the mass of an unused PM-sample medium. 

(b) Dynamometer calibration weights. [Reserved] 
Subpart I—Testing with Oxygenated Fuels 

§1065.801 Applicability. 

(a) This subpart applies for testing with oxygenated fuels. Unless the standard-setting part 

specifies otherwise, the requirements of this subpart do not apply for fuels that contain less than 

25 % oxygenated compounds by volume. For example, you generally do not need to follow the 

requirements of this subpart for tests performed using a fuel containing 10 % ethanol and 90 % 

gasoline, but you must follow these requirements for tests performed using a fuel containing 85 

% ethanol and 15 % gasoline. 

(b) Section 1065.805 applies for all other testing that requires measurement of any alcohols or 

carbonyls. 

(c) This subpart specifies sampling procedures and calculations that are different than those used 

for non-oxygenated fuels. All other test procedures of this part 1065 apply for testing with 

oxygenated fuels. 

§1065.805 Sampling system. 

(a) Dilute engine exhaust, and use batch sampling to collect proportional flow-weighted dilute 

samples of the applicable alcohols and carbonyls. You may not use raw sampling for alcohols 

and carbonyls. 

(b) You may collect background samples for correcting dilution air for background 

concentrations of alcohols and carbonyls. 

(c) Maintain sample temperatures within the dilution tunnel, probes, and sample lines high 

enough to prevent aqueous condensation up to the point where a sample is collected to prevent 

loss of the alcohols and carbonyls by dissolution in condensed water. Use good engineering 

judgment to ensure that surface reactions of alcohols and carbonyls do not occur, as surface 

decomposition of methanol has been shown to occur at temperatures greater than 120 °C in 

exhaust from methanol-fueled engines. 

(d) You may bubble a sample of the exhaust through water to collect alcohols for later analysis. 

You may also use a photo-acoustic analyzer to quantify ethanol and methanol in an exhaust 

sample as described in §1065.269. 

(e) Sample the exhaust through cartridges impregnated with 2,4-dinitrophenylhydrazine to 

collect carbonyls for later analysis. If the standard-setting part specifies a duty cycle that has 

multiple test intervals (such as multiple engine starts or an engine-off soak phase), you may 

proportionally collect a single carbonyl sample for the entire duty cycle. For example, if the 

standard-setting part specifies a six-to-one weighting of hot-start to cold-start emissions, you 

may collect a single carbonyl sample for the entire duty cycle by using a hot-start sample flow 

rate that is six times the cold-start sample flow rate. 

(f) You may sample alcohols or carbonyls using "California Non-Methane Organic Gas Test 

Procedures" (incorporated by reference in §1065.1010). If you use this method, follow its 

calculations to determine the mass of the alcohol/carbonyl in the exhaust sample, but follow 

subpart G of this part for all other calculations (40 CFR part 1066, subpart G, for vehicle testing).

(g) Use good engineering judgment to sample other oxygenated hydrocarbon compounds in the 

exhaust. 

§1065.845 Response factor determination. 
Since FID analyzers generally have an incomplete response to alcohols and carbonyls, determine 

each FID analyzer’s alcohol/carbonyl response factor (such as RFMeOH) after FID optimization to 

subtract those responses from the FID reading. Use the most recently determined

alcohol/carbonyl response factors to compensate for alcohol/carbonyl response. You are not 

required to determine the response factor for a compound unless you will subtract its response to 

compensate for a response. 

(a) You may generate response factors as described in paragraph (b) of this section, or you may 

use the following default response factors, consistent with good engineering judgment:

Table 1 of §1065.665–Default values for THC FID 

response factor relative to propane on a C1-equivalent basis

Compound Response factor (RF)

acetaldehyde 0.50

ethanol 0.75

formaldehyde 0.00

methanol 0.63

propanol 0.85

(a) Determine the alcohol/carbonyl response factors as follows: 

(1) Select a C3H8 span gas that meets the specifications of §1065.750. Note that FID zero and 

span balance gases may be any combination of purified air or purified nitrogen that meets the 

specifications of §1065.750. We recommend FID analyzer zero and span gases that contain 

approximately the flow-weighted mean concentration of O2 expected during testing. Record the 

C3H8 concentration of the gas. 

(2) Select or prepare an alcohol/carbonyl calibration gas that meets the specifications of 

§1065.750 and has a concentration typical of the peak concentration expected at the hydrocarbon 

standard. Record the calibration concentration of the gas. 

(3) Start and operate the FID analyzer according to the manufacturer’s instructions. 

(4) Confirm that the FID analyzer has been calibrated using C3H8. Calibrate on a carbon number 

basis of one (C1). For example, if you use a C3H8 span gas of concentration 200 mol/mol, span 

the FID to respond with a value of 600 mol/mol. 

(5) Zero the FID. Note that FID zero and span balance gases may be any combination of 

purified air or purified nitrogen that meets the specifications of §1065.750. We recommend FID 

analyzer zero and span gases that contain approximately the flow-weighted mean concentration 

of O2 expected during testing. 

(6) Span the FID with the C3H8 span gas that you selected under paragraph (a)(1) of this section. 

(7) Introduce at the inlet of the FID analyzer the alcohol/carbonyl calibration gas that you 

selected under paragraph (a)(2) of this section. 

(8) Allow time for the analyzer response to stabilize. Stabilization time may include time to 

purge the analyzer and to account for its response. 

(9) While the analyzer measures the alcohol/carbonyl concentration, record 30 seconds of 

sampled data. Calculate the arithmetic mean of these values. 

(10) Divide the mean measured concentration by the recorded span concentration of the 

alcohol/carbonyl calibration gas. The result is the FID analyzer’s response factor for 

alcohol/carbonyl, RFMeOH. 

Deleted: Formaldehyde response is assumed to 

be zero and does not need to be determined. Use the 

most recent alcohol/carbonyl response factors to 

compensate for alcohol/carbonyl response.

Deleted: a
(c) Alcohol/carbonyl calibration gases must remain within ±2 % of the labeled concentration. 

You must demonstrate the stability based on a quarterly measurement procedure with a precision 

of ±2 % percent or another method that we approve. Your measurement procedure may 

incorporate multiple measurements. If the true concentration of the gas changes deviates by more 

than ±2 %, but less than ±10 %, the gas may be relabeled with the new concentration. 

§1065.850 Calculations. 

Use the calculations specified in §1065.665 to determine THCE or NMHCE and the calculations

specified in 40 CFR 1066.665 to determine NMOG.

Deleted: b
Subpart J—Field Testing and Portable Emission Measurement Systems

§1065.901 Applicability. 

(a) Field testing. This subpart specifies procedures for field-testing engines to determine brakespecific emissions using portable emission measurement systems (PEMS). These procedures are 

designed primarily for in-field measurements of engines that remain installed in vehicles or 

equipment the field. Field-test procedures apply to your engines only as specified in the 

standard-setting part. 

(b) Laboratory testing. You may use PEMS for any testing in a laboratory or similar environment 

without restriction or prior approval if the PEMS meets all applicable specifications for 

laboratory testing. You may also use PEMS for any testing in a laboratory or similar 

environment if we approve it in advance, subject to the following provisions: 

(1) Follow the laboratory test procedures specified in this part 1065, according to §1065.905(e). 

(2) Do not apply any PEMS-related field-testing adjustments or measurement allowances to 

laboratory emission results or standards. 

(3) Do not use PEMS for laboratory measurements if it prevents you from demonstrating 

compliance with the applicable standards. Some of the PEMS requirements in this part 1065 are 

less stringent than the corresponding laboratory requirements. Depending on actual PEMS 

performance, you might therefore need to account for some additional measurement uncertainty 

when using PEMS for laboratory testing. If we ask, you must show us by engineering analysis 

that any additional measurement uncertainty due to your use of PEMS for laboratory testing is 

offset by the extent to which your engine’s emissions are below the applicable standards. For 

example, you might show that PEMS versus laboratory uncertainty represents 5 % of the 

standard, but your engine’s deteriorated emissions are at least 20 % below the standard for each 

pollutant. 

§1065.905 General provisions. 

(a) General. Unless the standard-setting part specifies deviations from the provisions of this 

subpart, field testing and laboratory testing with PEMS must conform to the provisions of this 

subpart. 

(b) Field-testing scope. Field testing conducted under this subpart may include any normal in-use 

operation of an engine. 

(c) Field testing and the standard-setting part. This subpart J specifies procedures for fieldtesting various categories of engines. See the standard-setting part for specific provisions for a 

particular type of engine. Before using this subpart's procedures for field testing, read the 

standard-setting part to answer at least the following questions: 

(1) How many engines must I test in the field? 

(2) How many times must I repeat a field test on an individual engine? 

(3) How do I select vehicles for field testing? 

(4) What maintenance steps may I take before or between tests? 

(5) What data are needed for a single field test on an individual engine? 

(6) What are the limits on ambient conditions for field testing? Note that the ambient condition 

limits in §1065.520 do not apply for field testing. Field testing may occur at any ambient 

temperature, pressure, and humidity unless otherwise specified in the standard-setting part. 

(7) Which exhaust constituents do I need to measure? 

(8) How do I account for crankcase emissions? 
(9) Which engine and ambient parameters do I need to measure? 

(10) How do I process the data recorded during field testing to determine if my engine meets 

field-testing standards? How do I determine individual test intervals? Note that “test interval” is 

defined in subpart K of this part 1065. 

(11) Should I warm up the test engine before measuring emissions, or do I need to measure coldstart emissions during a warm-up segment of in-use operation? 

(12) Do any unique specifications apply for test fuels? 

(13) Do any special conditions invalidate parts of a field test or all of a field test? 

(14) Does any special measurement allowance apply to field-test emission results or standards, 

based on using PEMS for field-testing versus using laboratory equipment and instruments for 

laboratory testing? 

(15) Do results of initial field testing trigger any requirement for additional field testing or 

laboratory testing? 

(16) How do I report field-testing results? 

(d) Field testing and this part 1065. Use the following specifications for field testing: 

(1) Use the applicability and general provisions of subpart A of this part. 

(2) Use equipment specifications in §1065.101 and in the sections from §1065.140 to the end of 

subpart B of this part, with the exception of §1065.140(e)(1) and (4), §1065.170(c)(1)(vi), and 

§1065.195(c). Section 1065.910 identifies additional equipment that is specific to field testing. 

(i) For PM samples, configure dilution systems as follows: 

(A) Use good engineering judgment to control dilution air temperature. If you choose to directly 

and actively control dilution air temperature, set the temperature to 25 °C. 

(B) Control sample temperature to a (32 to 62) °C tolerance, as measured anywhere within 20 cm 

upstream or downstream of the PM storage media (such as a filter or oscillating crystal), where 

the tolerance applies only during sampling. 

(C) Maintain filter face velocity to a (5 to 100) cm/s tolerance for flow-through media. 

Compliance with this provision can be verified by engineering analysis. This provision does not 

apply for non-flow-through media. 

(ii) For inertial PM balances, there is no requirement to control the stabilization environment 

temperature or dewpoint. 

(3) Use measurement instruments in subpart C of this part, except as specified in §1065.915. 

(4) Use calibrations and verifications in subpart D of this part, except as specified in §1065.920. 

Section 1065.920 also specifies additional calibrations and verifications for field testing. 

(5) Use the provisions of the standard-setting part for selecting and maintaining engines in the 

field instead of the specifications in subpart E of this part. 

(6) Use the procedures in §§1065.930 and 1065.935 to start and run a field test. If you use a 

gravimetric balance for PM, weigh PM samples according to §§1065.590 and 1065.595. 

(7) Use the calculations in subpart G of this part to calculate emissions over each test interval. 

Note that “test interval” is defined in subpart K of this part 1065, and that the standard setting 

part indicates how to determine test intervals for your engine. Section 1065.940 specifies 

additional calculations for field testing. Use any calculations specified in the standard-setting 

part to determine if your engines meet the field-testing standards. The standard-setting part may 

also contain additional calculations that determine when further field testing is required. 

(8) Use a typical in-use fuel meeting the specifications of §1065.701(d). 

(9) Use the lubricant and coolant specifications in §1065.740 and §1065.745. 

(10) Use the analytical gases and other calibration standards in §1065.750 and §1065.790. 

Deleted: diluent (i.e., 

Deleted: )

Deleted: diluent
(11) If you are testing with oxygenated fuels, use the procedures specified for testing with 

oxygenated fuels in subpart I of this part. 

(12) Apply the definitions and reference materials in subpart K of this part. 

(e) Laboratory testing using PEMS. You may use PEMS for testing in a laboratory as described 

in §1065.901(b). Use the following procedures and specifications when using PEMS for 

laboratory testing: 

(1) Use the applicability and general provisions of subpart A of this part. 

(2) Use equipment specifications in subpart B of this part. Section 1065.910 specifies additional 

equipment specific to testing with PEMS. 

(3) Use measurement instruments in subpart C of this part, except as specified in §1065.915. 

(4) Use calibrations and verifications in subpart D of this part, except as specified in §1065.920. 

Section 1065.920 also specifies additional calibration and verifications for PEMS. 

(5) Use the provisions of §1065.401 for selecting engines for testing. Use the provisions of 

subpart E of this part for maintaining engines, except as specified in the standard-setting part. 

(6) Use the procedures in subpart F of this part and in the standard-setting part to start and run a 

laboratory test. 

(7) Use the calculations in subpart G of this part to calculate emissions over the applicable duty 

cycle. Section 1065.940 specifies additional calculations for testing with PEMS. 

(8) Use a fuel meeting the specifications of subpart H of this part, as specified in the standardsetting part. 

(9) Use the lubricant and coolant specifications in §1065.740 and §1065.745. 

(10) Use the analytical gases and other calibration standards in §1065.750 and §1065.790. 

(11) If you are testing with oxygenated fuels, use the procedures specified for testing with 

oxygenated fuels in subpart I of this part. 

(12) Apply the definitions and reference materials in subpart K of this part. 

(f) Summary. The following table summarizes the requirements of paragraphs (d) and (e) of this 

section:
Table 1 of §1065.905–Summary of testing requirements that are specified outside of this subpart J 

Subpart Applicability for field testing1

Applicability for laboratory or 

similar testing with PEMS 

without restriction1

Applicability for laboratory or 

similar testing with PEMS with 

restrictions1

A: Applicability and general provisions Use all. Use all. Use all. B: Equipment for testing 

Use §1065.101 and §1065.140 through the end of subpart B, except 

§1065.140(e)(1) and (4), §1065.170(c)(1)(vi), and §1065.195(c). 

§1065.910 specifies equipment specific to field testing. 

Use all. 

Use all. 

§1065.910 specifies equipment 

specific to laboratory testing 

with PEMS. 

C: Measurement instruments Use all. §1065.915 allows deviations. Use all except §1065.295(c). Use all except §1065.295(c). §1065.915 allows deviations. D: Calibrations and verifications 

Use all except §1065.308 and §1065.309. 

§1065.920 allows deviations, but also has additional specifications. 

Use all. 

Use all. 

§1065.920 allows deviations, but 

also has additional 

specifications. 

E: Test engine selection, maintenance, and durability 

Do not use. 

Use standard-setting part. Use all. Use all. 

F: Running an emission test in the laboratory 

Use §§1065.590 and 1065.595 for PM 

§1065.930 and §1065.935 to start and run a field test. Use all. Use all. 

G: Calculations and data requirements 

Use all. 

§1065.940 has additional calculation instructions Use all. 

Use all. 

§1065.940 has additional 

calculation instructions 

H: Fuels, engine fluids, analytical gases, and other calibration materials 

Use all. Use all. Use all. 

I: Testing with oxygenated fuels Use all. Use all. Use all. K: Definitions and reference materials Use all. Use all. Use all. 1Refer to paragraphs (d) and (e) of this section for complete specifications. 
§1065.910 PEMS auxiliary equipment for field testing. 

For field testing you may use various types of auxiliary equipment to attach PEMS to a vehicle 

or engine and to power PEMS. 

(a) When you use PEMS, you may route engine intake air or exhaust through a flow meter. 

Route the engine intake air or exhaust as follows: 

(1) Flexible connections. Use short flexible connectors where necessary. 

(i) You may use flexible connectors to enlarge or reduce the pipe diameters to match that of your 

test equipment. 

(ii) We recommend that you use flexible connectors that do not exceed a length of three times 

their largest inside diameter. 

(iii) We recommend that you use four-ply silicone-fiberglass fabric with a temperature rating of 

at least 315 °C for flexible connectors. You may use connectors with a spring-steel wire helix 

for support and you may use NomexTM coverings or linings for durability. You may also use any 

other nonreactive material with equivalent permeation-resistance and durability, as long as it 

seals tightly. 

(iv) Use stainless-steel hose clamps to seal flexible connectors, or use clamps that seal 

equivalently. 

(v) You may use additional flexible connectors to connect to flow meters. 

(2) Tubing. Use rigid 300 series stainless steel tubing to connect between flexible connectors. 

Tubing may be straight or bent to accommodate vehicle geometry. You may use “T” or “Y” 

fittings made of 300 series stainless steel tubing to join multiple connections, or you may cap or 

plug redundant flow paths if the engine manufacturer recommends it. 

(3) Flow restriction. Use flow meters, connectors, and tubing that do not increase flow 

restriction so much that it exceeds the manufacturer’s maximum specified value. You may 

verify this at the maximum exhaust flow rate by measuring pressure at the manufacturerspecified location with your system connected. You may also perform an engineering analysis to 

verify an acceptable configuration, taking into account the maximum exhaust flow rate expected, 

the field test system’s flexible connectors, and the tubing’s characteristics for pressure drops 

versus flow. 

(b) For vehicles or other motive equipment, we recommend installing PEMS in the same location 

where a passenger might sit. Follow PEMS manufacturer instructions for installing PEMS in 

cargo spaces, engine spaces, or externally such that PEMS is directly exposed to the outside 

environment. We recommend locating PEMS where it will be subject to minimal sources of the 

following parameters: 

(1) Ambient temperature changes. 

(2) Ambient pressure changes. 

(3) Electromagnetic radiation. 

(4) Mechanical shock and vibration. 

(5) Ambient hydrocarbons–if using a FID analyzer that uses ambient air as FID burner air. 

(c) Use mounting hardware as required for securing flexible connectors, ambient sensors, and 

other equipment. Use structurally sound mounting points such as vehicle frames, trailer hitch 

receivers, walk spaces, and payload tie-down fittings. We recommend mounting hardware such 

as clamps, suction cups, and magnets that are specifically designed for your application. We also 

recommend considering mounting hardware such as commercially available bicycle racks, trailer 

hitches, and luggage racks where applicable. 
(d) Field testing may require portable electrical power to run your test equipment. Power your 

equipment, as follows: 

(1) You may use electrical power from the vehicle, equipment, or vessel, up to the highest power 

level, such that all the following are true: 

(i) The power system is capable of safely supplying power, such that the power demand for 

testing does not overload the power system. 

(ii) The engine emissions do not change significantly as a result the power demand for testing. 

(iii) The power demand for testing does not increase output from the engine by more than 1 % of 

its maximum power. 

(2) You may install your own portable power supply. For example, you may use batteries, fuel 

cells, a portable generator, or any other power supply to supplement or replace your use of 

vehicle power. You may connect an external power source directly to the vehicle's, vessel’s, or 

equipment’s power system; however, during a test interval (such as an NTE event) you must not 

supply power to the vehicle's power system in excess of 1 % of the engine's maximum power. 

§1065.915 PEMS instruments. 

(a) Instrument specifications. We recommend that you use PEMS that meet the specifications of 

subpart C of this part. For unrestricted use of PEMS in a laboratory or similar environment, use 

a PEMS that meets the same specifications as each lab instrument it replaces. For field testing or 

for testing with PEMS in a laboratory or similar environment, under the provisions of 

§1065.905(b), the specifications in the following table apply instead of the specifications in 

Table 1 of §1065.205.
Table 1 of §1065.915–Recommended minimum PEMS measurement instrument performance 

Measurement Measured quantity symbol Rise time, t10-90, and Fall time, t90-10 Recording update frequency Accuracy1 Repeatability1 Noise1

Engine speed transducer 

fn 1 s 1 Hz means 5 % of pt. or 1 % of max. 2 % of pt. or 1 % of max. 0.5 % of max 

Engine torque estimator, BSFC 

(This is a signal from an engine’s ECM) T or BSFC 1 s 1 Hz means 8 % of pt. or 5 % of max. 2 % of pt. or 1 % of max. 1 % of max. 

General pressure transducer 

(not a part of another instrument) p 5 s 1 Hz 5 % of pt. or 5 % of max. 2 % of pt. or 0.5 % of max. 1 % of max 

Atmospheric pressure meter patmos 50 s 0.1 Hz 250 Pa 200 Pa 100 Pa 

General temperature sensor 

(not a part of another instrument) T 5 s 1 Hz 1 % of pt. K or 5 K 0.5 % of pt. K or 2 K 0.5 % of max 0.5 K 

General dewpoint sensor Tdew 50 s 0.1 Hz 3 K 1 K 1 K 

Exhaust flow meter n 1 s 1 Hz means 5 % of pt. or 3 % of max. 2 % of pt. 2 % of max. 

Dilution air, inlet air, exhaust, and sample 

flow meters n 1 s 1 Hz means 2.5 % of pt. or 1.5 % of max. 1.25 % of pt. or 0.75 % of max. 1 % of max. 

Continuous gas analyzer x 5 s 1 Hz 4 % of pt. or 4 % of meas. 2 % of pt. or 2 % of meas. 1 % of max. Gravimetric PM balance 

mPM N/A N/A See §1065.790 0.5 g N/A 

Inertial PM balance 

mPM N/A N/A 4 % of pt. or 4 % of meas. 2 % of pt. or 2 % of meas. 1 % of max 

1Accuracy, repeatability, and noise are all determined with the same collected data, as described in §1065.305, and based on absolute values. “pt.” refers to the overall 

flow-weighted mean value expected at the standard; “max.” refers to the peak value expected at the standard over any test interval, not the maximum of the instrument’s range; “meas” refers to the actual flow-weighted mean measured over any test interval. 
(b) Redundant measurements. For all PEMS described in this subpart, you may use data from 

multiple instruments to calculate test results for a single test. If you use redundant systems, use 

good engineering judgment to use multiple measured values in calculations or to disregard 

individual measurements. Note that you must keep your results from all measurements, as 

described in §1065.25. This requirement applies whether or not you actually use the 

measurements in your calculations. 

(c) Field-testing ambient effects on PEMS. We recommend that you use PEMS that are only 

minimally affected by ambient conditions such as temperature, pressure, humidity, physical 

orientation, mechanical shock and vibration, electromagnetic radiation, and ambient 

hydrocarbons. Follow the PEMS manufacturer’s instructions for proper installation to isolate 

PEMS from ambient conditions that affect their performance. If a PEMS is inherently affected 

by ambient conditions that you cannot control, you may monitor those conditions and adjust the 

PEMS signals to compensate for the ambient effect. The standard-setting part may also specify 

the use of one or more field-testing adjustments or measurement allowances that you apply to 

results or standards to account for ambient effects on PEMS. 

(d) ECM signals. You may use signals from the engine’s electronic control module (ECM) in 

place of values measured by individual instruments within a PEMS, subject to the following 

provisions: 

(1) Recording ECM signals. If your ECM updates a broadcast signal more or less frequently than 

1 Hz, process data as follows: 

(i) If your ECM updates a broadcast signal more frequently than 1 Hz, use PEMS to sample and 

record the signal’s value more frequently. Calculate and record the 1 Hz mean of the more 

frequently updated data. 

(ii) If your ECM updates a broadcast signal less frequently than 1 Hz, use PEMS to sample and 

record the signal’s value at the most frequent rate. Linearly interpolate between recorded values 

and record the interpolated values at 1 Hz. 

(iii) Optionally, you may use PEMS to electronically filter the ECM signals to meet the rise time 

and fall time specifications in Table 1 of this section. Record the filtered signal at 1 Hz. 

(2) Omitting ECM signals. Replace any discontinuous or irrational ECM data with linearly 

interpolated values from adjacent data. 

(3) Aligning ECM signals with other data. You must perform time-alignment and dispersion of 

ECM signals, according to PEMS manufacturer instructions and using good engineering 

judgment. 

(4) ECM signals for determining test intervals. You may use any combination of ECM signals, 

with or without other measurements, to determine the start-time and end-time of a test interval. 

(5) ECM signals for determining brake-specific emissions. You may use any combination of 

ECM signals, with or without other measurements, to estimate engine speed, torque, brakespecific fuel consumption (BSFC, in units of mass of fuel per kW-hr), and fuel rate for use in 

brake-specific emission calculations. We recommend that the overall performance of any speed, 

torque, or BSFC estimator should meet the performance specifications in Table 1 of this section. 

We recommend using one of the following methods: 

(i) Speed. Use the engine speed signal directly from the ECM. This signal is generally accurate 

and precise. You may develop your own speed algorithm based on other ECM signals. 

(ii) Torque. Use one of the following: 
(A) ECM torque. Use the engine-torque signal directly from the ECM, if broadcast. Determine if 

this signal is proportional to indicated torque or brake torque. If it is proportional to indicated 

torque, subtract friction torque from indicated torque and record the result as brake torque. 

Friction torque may be a separate signal broadcast from the ECM or you may have to determine 

it from laboratory data as a function of engine speed. 

(B) ECM %-load. Use the %-load signal directly from the ECM, if broadcast. Determine if this 

signal is proportional to indicated torque or brake torque. If it is proportional to indicated torque, 

subtract the minimum %-load value from the %-load signal. Multiply this result by the 

maximum brake torque at the corresponding engine speed. Maximum brake torque versus speed 

information is commonly published by the engine manufacturer. 

(C) Your algorithms. You may develop and use your own combination of ECM signals to 

determine torque. 

(iii) BSFC. Use one of the following: 

(A) Use ECM engine speed and ECM fuel flow signals to interpolate brake-specific fuel 

consumption data, which might be available from an engine laboratory as a function of ECM 

engine speed and ECM fuel signals. 

(B) Use a single BSFC value that approximates the BSFC value over a test interval (as defined in 

subpart K of this part). This value may be a nominal BSFC value for all engine operation 

determined over one or more laboratory duty cycles, or it may be any other BSFC that you 

determine. If you use a nominal BSFC, we recommend that you select a value based on the 

BSFC measured over laboratory duty cycles that best represent the range of engine operation that 

defines a test interval for field-testing. You may use the methods of this paragraph (d)(5)(iii)(B) 

only if it does not adversely affect your ability to demonstrate compliance with applicable 

standards. 

(C) You may develop and use your own combination of ECM signals to determine BSFC. 

(iv) ECM fuel rate. Use the fuel rate signal directly from the ECM and chemical balance to 

determine the molar flow rate of exhaust. Use §1065.655(d) to determine the carbon mass 

fraction of fuel. Note that if the fuel rate drops below 10 % of the manufacturer-declared 

maximum fuel rate, the ratio of the emission concentrations to fuel rate will be held constant at 

that value; this ratio will apply until the fuel rate increases above 10 % of the manufacturerdeclared maximum fuel rate. You may alternatively develop and use your own combination of 

ECM signals to determine fuel mass flow rate. 

(v) Other ECM signals. You may ask to use other ECM signals for determining brake-specific 

emissions, such as ECM air flow. We must approve the use of such signals in advance. 

(6) Permissible deviations. ECM signals may deviate from the specifications of this part 1065, 

but the expected deviation must not prevent you from demonstrating that you meet the applicable 

standards. For example, your emission results may be sufficiently below an applicable standard, 

such that the deviation would not significantly change the result. As another example, a very 

low engine-coolant temperature may define a logical statement that determines when a test 

interval may start. In this case, even if the ECM’s sensor for detecting coolant temperature was 

not very accurate or repeatable, its output would never deviate so far as to significantly affect 

when a test interval may start. 

(e) Engine speed transducers. You may use an externally mounted engine speed transducer to 

measure engine speed. Select an engine speed transducer that generates a signal in linear 

proportion to engine speed. We recommend that you use an engine speed transducer that meets
the specifications in Table 1 of §1065.915. Record engine speed transducer output according to 

this subpart J. Calibrate and verify engine transducer performance according to §1065.920(c). 

You may use any type of engine speed transducer that meets the calibration and verification 

requirements in §1065.920(c) , including the following specific types:

(1) A magnetic flux sensor speed transducer mounted on the housing of an engine-driven 

alternator.

(2) A ferromagnetic material sensor speed transducer (e.g. a “mag pickup”) that detects when a 

ferromagnetic rotating engine part periodically comes into close proximity to the sensor.

(3) A ripple voltage sensor speed transducer connected across the positive and negative terminals 

of an engine’s electrical system, where the electrical system is supplied by an engine-driven 

alternator. In some cases this sensor may be simply plugged into an electric accessory receptacle 

such as for cigarette lighters.

(4) An optical sensor speed transducer that detects when a light-reflective rotating engine part 

periodically comes into close proximity to the sensor. Reflective tape or other reflective material 

may be added to the rotating engine part for clearer detection.

§1065.920 PEMS Calibrations and verifications. 

(a) Subsystem calibrations and verifications. Use all the applicable calibrations and verifications 

in subpart D of this part, including the linearity verifications in §1065.307, to calibrate and verify 

PEMS. Note that a PEMS does not have to meet the system-response and updating-recording 

verifications of §1065.308 and §1065.309 if it meets the overall verification described in 

paragraph (b) of this section. This section does not apply to ECM signals. 

(b) Overall verification. We require only that you maintain a record showing that the particular 

make, model, and configuration of your PEMS meets this verification. We recommend that you 

generate your own record to show that your specific PEMS meets this verification, but you may 

also rely on data and other information from the PEMS manufacturer. If you upgrade or change 

the configuration of your PEMS, your record must show that your new configuration meets this 

verification. The verification consists of operating an engine over a duty cycle in the laboratory 

and statistically comparing data generated and recorded by the PEMS with data simultaneously 

generated and recorded by laboratory equipment as follows: 

(1) Mount an engine on a dynamometer for laboratory testing. Prepare the laboratory and PEMS 

for emission testing, as described in this part, to get simultaneous measurements. We 

recommend selecting an engine with emission levels close to the applicable duty-cycle standards, 

if possible. 

(2) Select or create a duty cycle that has all the following characteristics: 

(i) Engine operation that represents normal in-use speeds, loads, and degree of transient activity. 

Consider using data from previous field tests to generate a cycle. 

(ii) A duration of (20 to 40) min. 

(iii) At least 50 % of engine operating time must include at least 10 valid test intervals for 

calculating emission levels for field testing. For example, for highway compression-ignition 

engines, select a duty cycle in which at least 50 % of the engine operating time can be used to 

calculate valid NTE events. 

(3) Starting with a warmed-up engine, run a valid emission test with the duty cycle from 

paragraph (b)(2) of this section. The laboratory and PEMS must both meet applicable validation 
requirements, such as drift validation, hydrocarbon contamination validation, and proportional 

validation. 

(4) Determine the brake-specific emissions for each test interval for both laboratory and the 

PEMS measurements, as follows: 

(i) For both laboratory and PEMS measurements, use identical values to determine the beginning 

and end of each test interval. 

(ii) For both laboratory and PEMS measurements, use identical values to determine total work 

over each test interval. 

(iii) If the standard-setting part specifies the use of a measurement allowance for field testing, 

also apply the measurement allowance during calibration using good engineering judgment. If 

the measurement allowance is normally added to the standard, this means you must subtract the 

measurement allowance from the measured PEMS brake-specific emission result. 

(iv) Round results to the same number of significant digits as the standard. 

(5) Repeat the engine duty cycle and calculations until you have at least 100 valid test intervals. 

(6) For each test interval and emission, subtract the lab result from the PEMS result. 

(7) The PEMS passes this verification if any one of the following are true for each constituent: 

(i) 91 % or more of the differences are zero or greater than zero. 

(ii) The entire set of test-interval results passes the 95 % confidence alternate-procedure statistics 

for field testing (t-test and F-test) specified in §1065.12. 

(c) Calibration and verification of engine speed transducers. Calibrate and verify the 

performance of externally mounted engine speed transducers in-situ as follows:

(1) Scope and frequency. Calibrate and verify the transducer after you have mounted it to the 

equipment and connected it to the PEMS. Calibrate and verify the transducer using a reference 

tachometer.

(2) Measurement principles. The transducer must be calibrated in-situ because its output signal 

(voltage, current, or frequency) may depend on an input signal from a component whose 

rotational speed differs from the engine’s rotational speed.

(3) System requirements. Calibrate the speed transducer and verify the calculated conversion to 

engine speeds before starting each field test. The PEMS meets verification requirements if it 

records engine speed to within ±2.5 % of the appropriate reference speed at idle speed, at a

midpoint engine speed, and at high engine speed.

(4) Speed transducer calibration procedure. Calibrate the speed transducer as follows:

(i) Select a reference tachometer that is NIST-traceable within ±0.1 % uncertainty over the 

engine’s speed range. Pair the reference tachometer with an engine component that has the same 

rotational speed as the crankshaft. You may accomplish this either by mechanically coupling the 

reference tachometer to the engine component or by using an optical reference tachometer that 

measures light reflected from the engine component. We recommend you use a reference 

tachometer that records average engine speed over at least a 30-second interval.

(ii) Set up the reference tachometer according to the tachometer manufacturer’s instructions. 

Mount and connect the engine speed transducer and the PEMS as they will be installed during 

the field test according to transducer and PEMS manufacturers’ instructions.

(iii) Start the engine and operate it at idle speed. Allow time for the engine speed to stabilize. 

This may include time for the engine to reach a stable operating temperature.

(iv) While the PEMS receives the engine speed transducer signal and the reference tachometer 

measures engine speed, record at least 30 seconds of this speed data with both the PEMS and the 

Deleted: less 

Deleted: subpart A of this part

Comment [CAL17]: This begs the question – if 

the part rotates 1:1 with engine rpm, why is ex-situ 

not ok? 
reference tachometer. Calculate the arithmetic means for the PEMS and the reference tachometer 

data.

(v) Increase operator demand with no engine loading to achieve an engine speed at the highest 

speed expected during testing. Allow time for the engine speed to stabilize. This may include 

time for the engine to reach a stable operating temperature at the higher speed. Repeat the 

measurement and calculation described in paragraph (c)(4)(iv) of this section.

(vi) Calculate the slope, a1y, and intercept, a0y, of the arithmetic means, using the reference 

tachometer’s means as the yi and the PEMS’s means as yrefi. See §1065.602(h) and (i). Use these 

slope and intercept values to convert the engine speed transducer signals to engine speed. Do 

this by multiplying each value from the engine speed transducer by a1y and then adding a0y. We 

recommend programming this conversion into the PEMS such that it converts the speed 

transducer data directly to engine speed; you may instead do this conversion with a separate 

post-processor.

(5) Speed conversion verification procedure. Verify the conversion of engine speed transducer 

data to engine speed as follows:

(i) Start and operate it at idle speed. Allow time for the engine speed to stabilize. This may 

include time for the engine to reach a stable operating temperature. Perform the measurement 

and calculation described in paragraph (c)(4)(iv) of this section.

(ii) Increase operator demand with no engine loading to achieve an engine speed near the 

midpoint between idle speed and the high engine speed used for calibration. Allow time for the

engine speed to stabilize. This may include time for the engine to reach a stable operating 

temperature at the higher speed. Repeat the measurement and calculation described in paragraph 

(c)(4)(iv) of this section.

(iii) Increase operator demand with no engine loading to achieve an engine speed at the highest 

speed expected during testing. Allow time for the engine speed to stabilize. This may include 

time for the engine to reach a stable operating temperature at the higher speed. Repeat the 

measurement and calculation described in paragraph (c)(4)(iv) of this section.

(iv) Convert all engine speed transducer signals to engine speed as described in paragraph 

(c)(4)(vi) of this section.

(v) Verify that the all the converted engine speed values for all three engine speeds are within the 

performance specifications in paragraph (c)(3) of this section.

(6) Remedial action. If any speed point falls outside the performance specification in paragraph 

(c)(3) of this section, we recommend taking the following remedial action and then repeating the 

calibration and verification procedure:

(i) Verify that the speed transducer is mounted securely and that the reference tachometer is 

functioning properly.

(ii) Verify that the rotating engine component sensed by the transducer is not subject to problems 

such a s a slipping belt that might prevent the component from rotating at the same speed as the 

engine’s crankshaft.

(iii) Verify the linearity of the speed transducer in a laboratory as described in §1065.307.

(7) Exception. You may perform an emission test after failing to meet the performance 

specification in paragraph (c)(3) of this section if you show that such a failure does not adversely 

affect your ability to demonstrate compliance with applicable emission standards.

§1065.925 PEMS preparation for field testing. 

Comment [CAL18]: The engine is already 

stabilized at idle, so this sentence is only meaningful 

if we say that they need to re-stabilize for high 

speed, or? On the other hand, if the engine runs on a 

thermostat, I'm not sure that this applies. 

Comment [CAL19]: (vi) Establishes that the 

measured speeds belong to the PEMS (based on 

speed transducer inputs). I might rather describe 

these as "speed transducer measurements", but if we 

go with these as PEMS measurements, let's use that 

consistently. 
Take the following steps to prepare PEMS for field testing: 

(a) Verify that ambient conditions at the start of the test are within the limits specified in the 

standard-setting part. Continue to monitor these values to determine if ambient conditions 

exceed the limits during the test. 

(b) Install a PEMS and any accessories needed to conduct a field test. 

(c) Power the PEMS and allow pressures, temperatures, and flows to stabilize to their operating 

set points. 

(d) Bypass or purge any gaseous sampling PEMS instruments with ambient air until sampling 

begins to prevent system contamination from excessive cold-start emissions. 

(e) Conduct calibrations and verifications. 

(f) Operate any PEMS dilution systems at their expected flow rates using a bypass. 

(g) If you use a gravimetric balance to determine whether an engine meets an applicable PM 

standard, follow the procedures for PM sample preconditioning and tare weighing as described in 

§1065.590. Operate the PM-sampling system at its expected flow rates using a bypass. 

(h) Verify the amount of contamination in the PEMS HC sampling system before the start of the 

field test as follows: 

(1) Select the HC analyzer range for measuring the maximum concentration expected at the HC 

standard. 

(2) Zero the HC analyzer using a zero gas or ambient air introduced at the analyzer port. When 

zeroing a FID, use the FID’s burner air that would be used for in-use measurements (generally 

either ambient air or a portable source of burner air). 

(3) Span the HC analyzer using span gas introduced at the analyzer port. 

(4) Overflow zero or ambient air at the HC probe inlet or into a tee near the probe outlet. 

(5) Measure the HC concentration in the sampling system: 

(i) For continuous sampling, record the mean HC concentration as overflow zero air flows. 

(ii) For batch sampling, fill the sample medium and record its mean concentration. 

(6) Record this value as the initial HC concentration, xTHCinit, and use it to correct measured 

values as described in §1065.660. 

(7) If the initial HC concentration exceeds the greater of the following values, determine the 

source of the contamination and take corrective action, such as purging the system or replacing 

contaminated portions: 

(i) 2 % of the flow-weighted mean concentration expected at the standard or measured during 

testing. 

(ii) 2 mol/mol. 

(8) If corrective action does not resolve the deficiency, you may use a contaminated HC system 

if it does not prevent you from demonstrating compliance with the applicable emission standards. 

§1065.930 Engine starting, restarting, and shutdown. 

Unless the standard-setting part specifies otherwise, start, restart, and shut down the test engine 

for field testing as follows: 

(a) Start or restart the engine as described in the owners manual. 

(b) If the engine does not start after 15 seconds of cranking, stop cranking and determine the 

reason it failed to start. However, you may crank the engine longer than 15 seconds, as long as 

the owners manual or the service-repair manual describes the longer cranking time as normal. 

(c) Respond to engine stalling with the following steps: 
(1) If the engine stalls during a required warm-up before emission sampling begins, restart the 

engine and continue warm-up. 

(2) If the engine stalls at any other time after emission sampling begins, restart the engine and 

continue testing. 

(d) Shut down and restart the engine according to the manufacturer’s specifications, as needed 

during normal operation in-use, but continue emission sampling until the field test is complete. 

§1065.935 Emission test sequence for field testing. 

(a) Time the start of field testing as follows: 

(1) If the standard-setting part requires only hot-stabilized emission measurements, operate the 

engine in-use until the engine coolant, block, or head absolute temperature is within ±10 % of its 

mean value for the previous 2 min or until an engine thermostat controls engine temperature with 

coolant or air flow. 

(2) If the standard-setting part requires hot-start emission measurements, shut down the engine 

after at least 2 min at the temperature tolerance specified in paragraph (a)(1) of this section. Start 

the field test within 20 min of engine shutdown. 

(3) If the standard-setting part requires cold-start emission measurements, proceed to the steps 

specified in paragraph (b) of this section. 

(b) Take the following steps before emission sampling begins: 

(1) For batch sampling, connect clean storage media, such as evacuated bags or tare-weighed PM 

sample media. 

(2) Operate the PEMS according to the instrument manufacturer’s instructions and using good 

engineering judgment. 

(3) Operate PEMS heaters, dilution systems, sample pumps, cooling fans, and the data-collection 

system. 

(4) Pre-heat or pre-cool PEMS heat exchangers in the sampling system to within their tolerances 

for operating temperatures. 

(5) Allow all other PEMS components such as sample lines, filters, and pumps to stabilize at 

operating temperature. 

(6) Verify that no significant vacuum-side leak exists in the PEMS, as described in §1065.345. 

(7) Adjust PEMS flow rates to desired levels, using bypass flow if applicable. 

(8) Zero and span all PEMS gas analyzers using NIST-traceable gases that meet the 

specifications of §1065.750. 

(c) Start testing as follows: 

(1) Before the start of the first test interval, zero or re-zero any PEMS electronic integrating 

devices, as needed. 

(2) If the engine is already running and warmed up and starting is not part of field testing, start 

the field test by simultaneously starting to sample exhaust, record engine and ambient data, and 

integrate measured values using a PEMS. 

(3) If engine starting is part of field testing, start field testing by simultaneously starting to 

sample from the exhaust system, record engine and ambient data, and integrate measured values 

using a PEMS. Then start the engine. 

(d) Continue the test as follows: 

(1) Continue to sample exhaust, record data and integrate measured values throughout normal inuse operation of the engine. 
(2) Between each test interval, zero or re-zero any electronic integrating devices, and reset batch 

storage media, as needed. 

(3) The engine may be stopped and started, but continue to sample emissions throughout the 

entire field test. 

(4) Conduct periodic verifications such as zero and span verifications on PEMS gas analyzers, as 

recommended by the PEMS manufacturer or as indicated by good engineering judgment. 

Results from these verifications will be used to calculate and correct for drift according to 

paragraph (g) of this section. Do not include data recorded during verifications in emission 

calculations. 

(5) You may periodically condition and analyze batch samples in-situ, including PM samples; for 

example you may condition an inertial PM balance substrate if you use an inertial balance to 

measure PM. 

(6) You may have personnel monitoring and adjusting the PEMS during a test, or you may 

operate the PEMS unattended. 

(e) Stop testing as follows: 

(1) Continue sampling as needed to get an appropriate amount of emission measurement, 

according to the standard setting part. If the standard-setting part does not describe when to stop 

sampling, develop a written protocol before you start testing to establish how you will stop 

sampling. You may not determine when to stop testing based on emission results. 

(2) At the end of the field test, allow the sampling systems’ response times to elapse and then 

stop sampling. Stop any integrators and indicate the end of the test cycle on the data-collection 

medium. 

(3) You may shut down the engine before or after you stop sampling. 

(f) For any proportional batch sample, such as a bag sample or PM sample, verify for each test 

interval whether or not proportional sampling was maintained according to §1065.545. Void the 

sample for any test interval that did not maintain proportional sampling according to §1065.545. 

(g) Take the following steps after emission sampling is complete: 

(1) As soon as practical after the emission sampling, analyze any gaseous batch samples. 

(2) If you used dilution air, either analyze background samples or assume that background 

emissions were zero. Refer to §1065.140 for dilution-air specifications. 

(3) After quantifying all exhaust gases, record mean analyzer values after stabilizing a zero gas 

to each analyzer, then record mean analyzer values after stabilizing the span gas to the analyzer. 

Stabilization may include time to purge an analyzer of any sample gas, plus any additional time 

to account for analyzer response. Use these recorded values to correct for drift as described in 

§1065.550. 

(4) Invalidate any test intervals that do not meet the range criteria in §1065.550. Note that it is 

acceptable that analyzers exceed 100 % of their ranges when measuring emissions between test 

intervals, but not during test intervals. You do not have to retest an engine in the field if the 

range criteria are not met. 

(5) Invalidate any test intervals that do not meet the drift criterion in §1065.550. For NMHC, 

invalidate any test intervals if the difference between the uncorrected and the corrected brakespecific NMHC emission values are within ±10 % of the uncorrected results or the applicable 

standard, whichever is greater. For test intervals that do meet the drift criterion, correct those 

test intervals for drift according to §1065.672 and use the drift corrected results in emissions 

calculations. 
(6) Unless you weighed PM in-situ, such as by using an inertial PM balance, place any used PM 

samples into covered or sealed containers and return them to the PM-stabilization environment 

and weigh them as described in §1065.595. 

§1065.940 Emission calculations. 

(a) Perform emission calculations as described in §1065.650 to calculate brake-specific 

emissions for each test interval using any applicable information and instructions in the standardsetting part. You must report emission results using the same calculation method

(§1065.650(a)(1), §1065.650(a)(3), or §1065.915(d)(5)(iv)) for all regulated pollutants for a 

given shift-day.

(b) You may use a fixed molar mass for the diluted exhaust mixture for field testing. Determine 

this fixed value by engineering analysis.
Subpart K—Definitions and Other Reference Information

§1065.1001 Definitions. 

The definitions in this section apply to this part. The definitions apply to all subparts unless we 

note otherwise. All undefined terms have the meaning the Act gives them. The definitions 

follow:

 300 series stainless steel means any stainless steel alloy with a Unified Numbering 

System for Metals and Alloys number designated from S30100 to S39000. For all instances in 

this part where we specify 300 series stainless steel, such parts must also have a smooth innerwall construction. We recommend an average roughness, Ra, no greater than 4 m. 

 Accuracy means the absolute difference between a reference quantity and the arithmetic 

mean of ten mean measurements of that quantity. Determine instrument accuracy, repeatability, 

and noise from the same data set. We specify a procedure for determining accuracy in 

§1065.305. 

 Act means the Clean Air Act, as amended, 42 U.S.C. 7401 - 7671q. 

 Adjustable parameter means any device, system, or element of design that someone can 

adjust (including those which are difficult to access) and that, if adjusted, may affect emissions 

or engine performance during emission testing or normal in-use operation. This includes, but is 

not limited to, parameters related to injection timing and fueling rate. In some cases, this may 

exclude a parameter that is difficult to access if it cannot be adjusted to affect emissions without 

significantly degrading engine performance, or if it will not be adjusted in a way that affects 

emissions during in-use operation. 

 Aerodynamic diameter means the diameter of a spherical water droplet that settles at the 

same constant velocity as the particle being sampled. 

 Aftertreatment means relating to a catalytic converter, particulate filter, or any other 

system, component, or technology mounted downstream of the exhaust valve (or exhaust port) 

whose design function is to decrease emissions in the engine exhaust before it is exhausted to the 

environment. Exhaust-gas recirculation (EGR) and turbochargers are not aftertreatment. 

 Allowed procedures means procedures that we either specify in this part 1065 or in the 

standard-setting part or approve under §1065.10. 

 Alternate procedures means procedures allowed under §1065.10(c)(7). 

 Applicable standard means an emission standard to which an engine is subject; or a 

family emission limit to which an engine is certified under an emission credit program in the 

standard-setting part. 

 Aqueous condensation means the precipitation of water-containing constituents from a 

gas phase to a liquid phase. Aqueous condensation is a function of humidity, pressure, 

temperature, and concentrations of other constituents such as sulfuric acid. These parameters 

vary as a function of engine intake-air humidity, dilution-air humidity, engine air-to-fuel ratio, 

and fuel composition—including the amount of hydrogen and sulfur in the fuel. 

 Atmospheric pressure means the wet, absolute, atmospheric static pressure. Note that if 

you measure atmospheric pressure in a duct, you must ensure that there are negligible pressure 

losses between the atmosphere and your measurement location, and you must account for 

changes in the duct’s static pressure resulting from the flow. 

 Auto-ranging means a gas analyzer function that automatically changes the analyzer 

digital resolution to a larger range of concentrations as the concentration approaches 100 % of 
the analyzer’s current range. Auto-ranging does not mean changing an analog amplifier gain 

within an analyzer. 

 Auxiliary emission-control device means any element of design that senses temperature, 

motive speed, engine RPM, transmission gear, or any other parameter for the purpose of 

activating, modulating, delaying, or deactivating the operation of any part of the emissioncontrol system. 

 Brake power has the meaning given in the standard-setting part. If it is not defined in the 

standard-setting part, brake power means the usable power output of the engine, not including 

power required to fuel, lubricate, or heat the engine, circulate coolant to the engine, or to operate 

aftertreatment devices. If the engine does not power these accessories during a test, subtract the 

work required to perform these functions from the total work used in brake-specific emission 

calculations. Subtract engine fan work from total work only for air-cooled engines. 

 C1 equivalent (or basis) means a convention of expressing HC concentrations based on 

the total number of carbon atoms present, such that the C1 equivalent of a molar HC 

concentration equals the molar concentration multiplied by the mean number of carbon atoms in 

each HC molecule. For example, the C1 equivalent of 10 mol/mol of propane (C3H8) is 30 

mol/mol. C1 equivalent molar values may be denoted as “ppmC” in the standard-setting part. 

Molar mass may also be expressed on a C1 basis. Note that calculating HC masses from molar 

concentrations and molar masses is only valid where they are each expressed on the same carbon 

basis.

 Calibration means the process of setting a measurement system’s response so that its 

output agrees with a range of reference signals. Contrast with “verification”.

Calibration gas means a purified gas mixture used to calibrate gas analyzers. Calibration 

gases must meet the specifications of §1065.750. Note that calibration gases and span gases are 

qualitatively the same, but differ in terms of their primary function. Various performance 

verification checks for gas analyzers and sample handling components might refer to either 

calibration gases or span gases. 

 Certification means relating to the process of obtaining a certificate of conformity for an 

engine family that complies with the emission standards and requirements in the standard-setting 

part. 

 Compression-ignition means relating to a type of reciprocating, internal-combustion 

engine that is not a spark-ignition engine. 

 Confidence interval means the range associated with a probability that a quantity will be 

considered statistically equivalent to a reference quantity. 

 Constant-speed engine means an engine whose certification is limited to constant-speed 

operation. Engines whose constant-speed governor function is removed or disabled are no 

longer constant-speed engines. 

 Constant-speed operation means engine operation with a governor that automatically 

controls the operator demand to maintain engine speed, even under changing load. Governors do 

not always maintain speed exactly constant. Typically speed can decrease (0.1 to 10) % below 

the speed at zero load, such that the minimum speed occurs near the engine’s point of maximum 

power. 

 Coriolis meter means a flow-measurement instrument that determines the mass flow of a 

fluid by sensing the vibration and twist of specially designed flow tubes as the flow passes 

through them. The twisting characteristic is called the Coriolis effect. According to Newton's 
Second Law of Motion, the amount of sensor tube twist is directly proportional to the mass flow 

rate of the fluid flowing through the tube. See §1065.220. 

 Designated Compliance Officer means the Director, Compliance and Innovative 

Strategies Division (6405-J), U.S. Environmental Protection Agency, 1200 Pennsylvania Ave., 

NW., Washington, DC 20460. 

 Dewpoint means a measure of humidity stated as the equilibrium temperature at which 

water condenses under a given pressure from moist air with a given absolute humidity. 

Dewpoint is specified as a temperature in °C or K, and is valid only for the pressure at which it is 

measured. See §1065.645 to determine water vapor mole fractions from dewpoints using the 

pressure at which the dewpoint is measured. 

 Discrete-mode means relating to a discrete-mode type of steady-state test, as described in 

the standard-setting part. 

 Dispersion means either: 

(1) The broadening and lowering of a signal due to any fluid capacitance, fluid mixing, or 

electronic filtering in a sampling system. (Note: To adjust a signal so its dispersion matches that 

of another signal, you may adjust the system’s fluid capacitance, fluid mixing, or electronic 

filtering.) 

(2) The mixing of a fluid, especially as a result of fluid mechanical forces or chemical diffusion. 

 Dilution ratio (DR) means the amount of diluted exhaust per amount of undiluted 

exhaust. 

Drift means the difference between a zero or calibration signal and the respective value 

reported by a measurement instrument immediately after it was used in an emission test, as long 

as you zeroed and spanned the instrument just before the test. 

 Duty cycle means one of the following: 

(1) A series of speed and torque values (or power values) that an engine must follow during a 

laboratory test. Duty cycles are specified in the standard-setting part. A single duty cycle may 

consist of one or more test intervals. A series of speed and torque values meeting the definition 

of this paragraph (1) may also be considered a test cycle. For example, a duty cycle may be a 

ramped-modal cycle, which has one test interval; a cold-start plus hot-start transient cycle, which 

has two test intervals; or a discrete-mode cycle, which has one test interval for each mode. 

(2) A set of weighting factors and the corresponding speed and torque values, where the 

weighting factors are used to combine the results of multiple test intervals into a composite 

result. 

 Electric power generation application means an application whose purpose is to generate 

a precise frequency of electricity, which is characterized by an engine that controls engine speed 

very precisely. This would generally not apply to welders or portable home generators. 

Electronic control module means an engine’s electronic device that uses data from engine 

sensors to control engine parameters. 

 Emission-control system means any device, system, or element of design that controls or 

reduces the emissions of regulated pollutants from an engine. 

 Emission-data engine means an engine that is tested for certification. This includes 

engines tested to establish deterioration factors. 

 Emission-related maintenance means maintenance that substantially affects emissions or 

is likely to substantially affect emission deterioration. Deleted: ¶

Engine means an engine to which this part applies.
 Engine family means a group of engines with similar emission characteristics throughout 

the useful life, as specified in the standard-setting part. 

 Engine governed speed means the engine operating speed when it is controlled by the 

installed governor. 

 Exhaust-gas recirculation means a technology that reduces emissions by routing exhaust 

gases that had been exhausted from the combustion chamber(s) back into the engine to be mixed 

with incoming air before or during combustion. The use of valve timing to increase the amount 

of residual exhaust gas in the combustion chamber(s) that is mixed with incoming air before or 

during combustion is not considered exhaust-gas recirculation for the purposes of this part. 

 Fall time, t90-10, means the time interval of a measurement instrument's response after any 

step decrease to the input between the following points: 

(1) The point at which the response has fallen 10% of the total amount it will fall in response to 

the step change. 

(2) The point at which the response has fallen 90% of the total amount it will fall in response to 

the step change. 

 Flow-weighted mean means the mean of a quantity after it is weighted proportional to a 

corresponding flow rate. For example, if a gas concentration is measured continuously from the 

raw exhaust of an engine, its flow-weighted mean concentration is the sum of the products of 

each recorded concentration times its respective exhaust flow rate, divided by the sum of the 

recorded flow rates. As another example, the bag concentration from a CVS system is the same 

as the flow-weighted mean concentration, because the CVS system itself flow-weights the bag 

concentration. 

 Fuel type means a general category of fuels such as gasoline or LPG. There can be 

multiple grades within a single type of fuel, such as all-season and winter-grade gasoline. 

 Good engineering judgment means judgments made consistent with generally accepted 

scientific and engineering principles and all available relevant information. See 40 CFR 1068.5 

for the administrative process we use to evaluate good engineering judgment. 

 HEPA filter means high-efficiency particulate air filters that are rated to achieve a 

minimum initial particle-removal efficiency of 99.97 % using ASTM F1471 (incorporated by 

reference in §1065.1010). 

 High-idle speed means the engine speed at which an engine governor function controls 

engine speed with operator demand at maximum and with zero load applied. “Warm high-idle 

speed” is the high-idle speed of a warmed-up engine. 

High-speed governor means any device, system, or element of design that modulates the 

engine output torque for the purpose of limiting the maximum engine speed. 

 Hydraulic diameter means the diameter of a circle whose area is equal to the area of a 

noncircular cross section of tubing, including its wall thickness. The wall thickness is included 

only for the purpose of facilitating a simplified and nonintrusive measurement. 

 Hydrocarbon (HC) means THC, THCE, NMHC, or NMHCE, as applicable. 

Hydrocarbon generally means the hydrocarbon group on which the emission standards are based 

for each type of fuel and engine. 

 Identification number means a unique specification (for example, a model number/serial 

number combination) that allows someone to distinguish a particular engine from other similar 

engines. 

Deleted: -93
 Idle speed means the engine speed at which an engine governor function controls engine 

speed with operator demand at minimum and with minimum load applied (greater than or equal 

to zero). For engines without a governor function that controls idle speed, idle speed means the 

manufacturer-declared value for lowest engine speed possible with minimum load. This 

definition does not apply for operation designated as “high-idle speed.” “Warm idle speed” is 

the idle speed of a warmed-up engine. 

 Intermediate test speed has the meaning given in §1065.610. 

 Linearity means the degree to which measured values agree with respective reference 

values. Linearity is quantified using a linear regression of pairs of measured values and 

reference values over a range of values expected or observed during testing. Perfect linearity 

would result in an intercept, a0, equal to zero, a slope, a1, of one, a coefficient of determination, 

r

2

, of one, and a standard error of the estimate, SEE, of zero. The term "linearity" is not used in 

this part to refer to the shape of a measurement instrument’s unprocessed response curve, such as 

a curve relating emission concentration to voltage output. A properly performing instrument 

with a nonlinear response curve will meet linearity specifications. 

 Manufacturer has the meaning given in section 216(1) of the Act. In general, this term 

includes any person who manufactures an engine or vehicle for sale in the United States or 

otherwise introduces a new nonroad engine into commerce in the United States. This includes 

importers who import engines or vehicles for resale. 

 Maximum test speed has the meaning given in §1065.610. 

 Maximum test torque has the meaning given in §1065.610. 

 Measurement allowance means a specified adjustment in the applicable emission 

standard or a measured emission value to reflect the relative quality of the measurement. See the 

standard-setting part to determine whether any measurement allowances apply for your testing. 

Measurement allowances generally apply only for field testing and are intended to account for 

reduced accuracy or precision that result from using field-grade measurement systems. 

 Mode means one of the following: 

(1) A distinct combination of engine speed and load for steady-state testing. 

(2) A continuous combination of speeds and loads specifying a transition during a ramped-modal 

test. 

(3) A distinct operator demand setting, such as would occur when testing locomotives or 

constant-speed engines. 

 NIST-accepted means relating to a value that has been assigned or named by NIST.

 NIST-traceable means relating to a standard value that can be related to NIST-stated 

references through an unbroken chain of comparisons, all having stated uncertainties, as 

specified in NIST Technical Note 1297 (incorporated by reference in §1065.1010). Allowable 

uncertainty limits specified for NIST-traceability refer to the propagated uncertainty specified by 

NIST. You may ask to use other internationally recognized standards that are equivalent to 

NIST standards. 

 Noise means the precision of 30 seconds of updated recorded values from a measurement 

instrument as it quantifies a zero or reference value. Determine instrument noise, repeatability, 

and accuracy from the same data set. We specify a procedure for determining noise in 

§1065.305. 

 Nonmethane hydrocarbons (NMHC) means the sum of all hydrocarbon species except 

methane. Refer to §1065.660 for NMHC determination. 
 Nonmethane hydrocarbon equivalent (NMHCE) means the sum of the carbon mass 

contributions of non-oxygenated nonmethane hydrocarbons, alcohols and aldehydes, or other 

organic compounds that are measured separately as contained in a gas sample, expressed as 

exhaust nonmethane hydrocarbon from petroleum-fueled engines. The hydrogen-to-carbon ratio 

of the equivalent hydrocarbon is 1.85:1. 

 Nonroad means relating to nonroad engines. 

 Nonroad engine has the meaning we give in 40 CFR 1068.30. In general this means all 

internal-combustion engines except motor vehicle engines, stationary engines, engines used 

solely for competition, or engines used in aircraft. 

 Open crankcase emissions means any flow from an engine’s crankcase that is emitted 

directly into the environment. Crankcase emissions are not “open crankcase emissions” if the 

engine is designed to always route all crankcase emissions back into the engine (for example, 

through the intake system or an aftertreatment system) such that all the crankcase emissions, or 

their products, are emitted into the environment only through the engine exhaust system. 

 Operator demand means an engine operator's input to control engine output. The 

“operator” may be a person (i.e., manual), or a governor (i.e., automatic) that mechanically or 

electronically signals an input that demands engine output. Input may be from an accelerator 

pedal or signal, a throttle-control lever or signal, a fuel lever or signal, a speed lever or signal, or 

a governor setpoint or signal. Output means engine power, P, which is the product of engine 

speed, fn, and engine torque, T. 

 Oxides of nitrogen means NO and NO2 as measured by the procedures specified in 

§1065.270. Oxides of nitrogen are expressed quantitatively as if the NO is in the form of NO2, 

such that you use an effective molar mass for all oxides of nitrogen equivalent to that of NO2. 

 Oxygenated fuels means fuels composed of at least 25 % oxygen-containing compounds, 

such as ethanol or methanol. Testing engines that use oxygenated fuels generally requires the 

use of the sampling methods in subpart I of this part. However, you should read the standardsetting part and subpart I of this part to determine appropriate sampling methods. 

 Partial pressure means the pressure, p, attributable to a single gas in a gas mixture. For 

an ideal gas, the partial pressure divided by the total pressure is equal to the constituent’s molar 

concentration, x. 

 Percent (%) means a representation of exactly 0.01. Numbers expressed as percentages 

in this part (such as a tolerance of ±2 %) have infinite precision, so 2 % and 2.000000000 % 

have the same meaning. This means that where we specify some percentage of a total value, the 

calculated value has the same number of significant digits as the total value. For example, 2 % 

of a span value where the span value is 101.3302 is 2.026604. 

 Portable emission measurement system (PEMS) means a measurement system consisting 

of portable equipment that can be used to generate brake-specific emission measurements during 

field testing or laboratory testing. 

 Precision means two times the standard deviation of a set of measured values of a single 

zero or reference quantity. See also the related definitions of noise and repeatability in this 

section.

 Procedures means all aspects of engine testing, including the equipment specifications, 

calibrations, calculations and other protocols and specifications needed to measure emissions, 

unless we specify otherwise. 
 Proving ring is a device used to measure static force based on the linear relationship 

between stress and strain in an elastic material. It is typically a steel alloy ring, and you measure 

the deflection (strain) of its diameter when a static force (stress) is applied across its diameter. 

 PTFE means polytetrafluoroethylene, commonly known as TeflonTM. 

 Ramped-modal means relating to a ramped-modal type of steady-state test, as described 

in the standard-setting part. 

 Recommend has the meaning given in §1065.201. 

 Regression statistics means any of the regression statistics specified in §1065.602. 

 Regulated pollutant means an exhaust constituent for which an emission standard or a 

reporting requirement applies. 

Repeatability means the precision of ten mean measurements of a reference quantity. 

Determine instrument repeatability, accuracy, and noise from the same data set. We specify a 

procedure for determining repeatability in §1065.305. 

 Revoke has the meaning given in 40 CFR 1068.30. 

 Rise time, t10-90, means the time interval of a measurement instrument's response after any 

step increase to the input between the following points: 

(1) The point at which the response has risen 10% of the total amount it will rise in response to 

the step change. 

(2) The point at which the response has risen 90% of the total amount it will rise in response to 

the step change. 

 Roughness (or average roughness, Ra) means the size of finely distributed vertical surface 

deviations from a smooth surface, as determined when traversing a surface. It is an integral of 

the absolute value of the roughness profile measured over an evaluation length. 

 Round means to apply the rounding convention specified in §1065.20(e), unless 

otherwise specified. 

 Scheduled maintenance means adjusting, repairing, removing, disassembling, cleaning, 

or replacing components or systems periodically to keep a part or system from failing, 

malfunctioning, or wearing prematurely. It also may mean actions you expect are necessary to 

correct an overt indication of failure or malfunction for which periodic maintenance is not 

appropriate. 

 Shared atmospheric pressure meter means an atmospheric pressure meter whose output is 

used as the atmospheric pressure for an entire test facility that has more than one dynamometer 

test cell. 

 Shared humidity measurement means a humidity measurement that is used as the 

humidity for an entire test facility that has more than one dynamometer test cell. 

 Span means to adjust an instrument so that it gives a proper response to a calibration 

standard that represents between 75 % and 100 % of the maximum value in the instrument range 

or expected range of use. 

Span gas means a purified gas mixture used to span gas analyzers. Span gases must meet 

the specifications of §1065.750. Note that calibration gases and span gases are qualitatively the 

same, but differ in terms of their primary function. Various performance verification checks for 

gas analyzers and sample handling components might refer to either calibration gases or span 

gases. 

 Spark-ignition means relating to a gasoline-fueled engine or any other type of engine 

with a spark plug (or other sparking device) and with operating characteristics significantly 
similar to the theoretical Otto combustion cycle. Spark-ignition engines usually use a throttle to 

regulate intake air flow to control power during normal operation. 

 Special procedures means procedures allowed under §1065.10(c)(2). 

 Specified procedures means procedures we specify in this part 1065 or the standardsetting part. Other procedures allowed or required by §1065.10(c) are not specified procedures. 

 Standard deviation has the meaning given in §1065.602. Note this is the standard 

deviation for a non-biased sample. 

 Standard-setting part means the part in the Code of Federal Regulations that defines 

emission standards for a particular engine. See §1065.1(a). 

 Steady-state means relating to emission tests in which engine speed and load are held at a 

finite set of nominally constant values. Steady-state tests are either discrete-mode tests or 

ramped-modal tests. 

 Stoichiometric means relating to the particular ratio of air and fuel such that if the fuel 

were fully oxidized, there would be no remaining fuel or oxygen. For example, stoichiometric 

combustion in a gasoline-fueled engine typically occurs at an air-to-fuel mass ratio of about 

14.7:1. 

 Storage medium means a particulate filter, sample bag, or any other storage device used 

for batch sampling. 

 Test engine means an engine in a test sample. 

 Test interval means a duration of time over which you determine brake-specific 

emissions. For example, the standard-setting part may specify a complete laboratory duty cycle 

as a cold-start test interval, plus a hot-start test interval. As another example, a standard-setting 

part may specify a field-test interval, such as a “not-to-exceed” (NTE) event, as a duration of 

time over which an engine operates within a certain range of speed and torque. In cases where 

multiple test intervals occur over a duty cycle, the standard-setting part may specify additional 

calculations that weight and combine results to arrive at composite values for comparison against 

the applicable standards. 

 Test sample means the collection of engines selected from the population of an engine 

family for emission testing. 

 Tolerance means the interval in which at least 95 % of a set of recorded values of a 

certain quantity must lie. Use the specified recording frequencies and time intervals to determine 

if a quantity is within the applicable tolerance. The concept of tolerance is intended to address 

random variability. You may not take advantage of the tolerance specification to incorporate a 

bias into a measurement. 

 Total hydrocarbon (THC) means the combined mass of organic compounds measured by 

the specified procedure for measuring total hydrocarbon, expressed as a hydrocarbon with a 

hydrogen-to-carbon mass ratio of 1.85:1. 

 Total hydrocarbon equivalent (THCE) means the sum of the carbon mass contributions of 

non-oxygenated hydrocarbons, alcohols and aldehydes, or other organic compounds that are 

measured separately as contained in a gas sample, expressed as exhaust hydrocarbon from 

petroleum-fueled engines. The hydrogen-to-carbon ratio of the equivalent hydrocarbon is 1.85:1. 

Transformation time, t50, means the overall system response time to any step change in 

input, generally the average of the time to reach 50% response to a step increase, t0-50, or to a step 

decrease, t100-50. 
t0-50 means the time interval of a measurement system’s response after any step increase 

to the input between the following points: 

(1) The point at which the step change is initiated at the sample probe. 

(2) The point at which the response has risen 50% of the total amount it will rise in response to 

the step change. 

 t100-50 means the time interval of a measurement system’s response after any step decrease 

to the input between the following points: 

(1) The point at which the step change is initiated at the sample probe. 

(2) The point at which the response has fallen 50% of the total amount it will fall in response to 

the step change. 

 Uncertainty means uncertainty with respect to NIST-traceability. See the definition of 

NIST-traceable in this section. 

 United States means the States, the District of Columbia, the Commonwealth of Puerto 

Rico, the Commonwealth of the Northern Mariana Islands, Guam, American Samoa, and the 

U.S. Virgin Islands. 

 Useful life means the period during which a new engine is required to comply with all 

applicable emission standards. The standard-setting part defines the specific useful-life periods 

for individual engines. 

 Variable-speed engine means an engine that is not a constant-speed engine. 

 Vehicle means any vehicle, vessel, or type of equipment using engines to which this part 

applies. For purposes of this part, the term “vehicle” may include nonmotive machines or 

equipment such as a pump or generator. 

 Verification means to evaluate whether or not a measurement system’s outputs agree with 

a range of applied reference signals to within one or more predetermined thresholds for 

acceptance. Contrast with “calibration”. 

 We (us, our) means the Administrator of the Environmental Protection Agency and any 

authorized representatives. 

 Work has the meaning given in §1065.110. 

 Zero means to adjust an instrument so it gives a zero response to a zero calibration 

standard, such as purified nitrogen or purified air for measuring concentrations of emission 

constituents. 

 Zero gas means a gas that yields a zero response in an analyzer. This may either be 

purified nitrogen, purified air, a combination of purified air and purified nitrogen. For field 

testing, zero gas may include ambient air. 

§1065.1005 Symbols, abbreviations, acronyms, and units of measure. 

The procedures in this part generally follow the International System of Units (SI), as detailed in 

NIST Special Publication 811, which we incorporate by reference in §1065.1010. See §1065.20 

for specific provisions related to these conventions. This section summarizes the way we use 

symbols, units of measure, and other abbreviations. 

(a) Symbols for quantities. This part uses the following symbols and units of measure for 

various quantities: 

Symbol Quantity Unit Unit symbol Units in terms of SI 

base units 

 atomic hydrogen to carbon ratio mole per mole mol/mol 1 

A area square meter m2 m2
A0 intercept of least squares regression 

A1 slope of least squares regression 

 ratio of diameters meter per meter m/m 1 

 atomic oxygen to carbon ratio mole per mole mol/mol 1 

C# number of carbon atoms in a molecule 

d Diameter meter m m 

DR dilution ratio mole per mol mol/mol 1 

 error between a quantity and its 

reference 

e brake-specific emission or fuel 

consumption gram per kilowatt hour g/(kW·hr) g·3.6-1·106

·m-2·kg·s2

F F-test statistic 

f frequency hertz Hz s-1

fn angular speed (shaft) revolutions per minute r/min 2·π·60-1·m·m-1·s-1

 ratio of specific heats 

(joule per kilogram 

kelvin) per (joule per 

kilogram kelvin) 

(J/(kg·K))/(J/(kg·K)) 1 

K correction factor 1 

Kv calibration coefficient m4·s·K0.5/kg m4·s·K0.5·kg-1

l length meter m m 

 viscosity, dynamic pascal second Pa·s m-1·kg·s-1

M molar mass1 gram per mole g/mol 10-3·kg·mol-1

m mass kilogram kg kg 

m mass rate kilogram per second kg/s kg·s-1

 viscosity, kinematic meter squared per 

second m2

/s m2·s-1

N total number in series 

n amount of substance mole mol mol 

n amount of substance rate mole per second mol/s mol·s-1

P power kilowatt kW 103·m2·kg·s-3

PF penetration fraction 

p pressure pascal Pa m-1·kg·s-2

 mass density kilogram per cubic 

meter kg/m3

 kg·m-3

r ratio of pressures pascal per pascal Pa/Pa 1 

R2 coefficient of determination 

Ra average surface roughness micrometer m 10-6 m 

Re# Reynolds number 

RF response factor 

RH relative humidity 

 non-biased standard deviation 

S Sutherland constant kelvin K K 

SEE standard estimate of error 

T absolute temperature kelvin K K 

T Celsius temperature degree Celsius °C K-273.15 

T torque (moment of force) newton meter N·m m2·kg·s-2

t time second s s 

Comment [CAL20]: Updated. 
t time interval, period, 1/frequency second s s 

V volume cubic meter m3 m3

V volume rate cubic meter per second m3

/s m3·s-1

W work kilowatt hour kW·hr 3.6·10-6·m2·kg·s-2

wc carbon mass fraction gram per gram g/g 1 

x amount of substance mole fraction 2 mole per mole mol/mol 1 

x flow-weighted mean concentration mole per mole mol/mol 1 

y generic variable 

1

 See paragraph (f)(2) of this section for the values to use for molar masses. Note that in the cases of NOx and HC, the 

regulations specify effective molar masses based on assumed speciation rather than actual speciation. 2 Note that mole fractions for THC, THCE, NMHC, NMHCE, and NOTHC are expressed on a C1 equivalent basis. 

(b) Symbols for chemical species. This part uses the following symbols for chemical species and 

exhaust constituents: 

Symbol Species 

Ar argon 

C carbon 

CH4 methane 

C2H6 ethane 

C3H8 propane 

C4H10 butane 

C5H12 pentane 

CO carbon monoxide 

CO2 carbon dioxide 

H atomic hydrogen 

H2 molecular hydrogen 

H2O water 

He helium 

85Kr krypton 85 

N2 molecular nitrogen 

NMHC nonmethane hydrocarbon 

NMHCE nonmethane hydrocarbon equivalent 

NO nitric oxide 

NO2 nitrogen dioxide 

NOx oxides of nitrogen 

N2O nitrous oxide 

NMOG nonmethane organic gases

NONMHC nonoxygenated nonmethane hydrocarbon

NOTHC nonoxygenated total hydrocarbon 

O2 molecular oxygen 

OHC oxygenated hydrocarbon 

210Po polonium 210 

PM particulate matter

S sulfur 

SVOC semi-volatile organic compound

THC total hydrocarbon 

Deleted: mass
THCE total hydrocarbon equivalent

ZrO2 zirconium dioxide 

(c) Prefixes. This part uses the following prefixes to define a quantity: 

Symbol Quantity Value 

 micro 10-6

m milli 10-3

c centi 10-2

k kilo 103

M mega 106

(d) Superscripts. This part uses the following superscripts to define a quantity: 

Superscript Quantity 

overbar (such as y ) arithmetic mean

overdot (such as y ) quantity per unit time 

(e) Subscripts. This part uses the following subscripts to define a quantity: 

Subscript Quantity 

abs absolute quantity 

act actual condition 

air air, dry 

atmos atmospheric 

cal calibration quantity 

CFV critical flow venturi 

cor corrected quantity 

dil dilution air 

dexh diluted exhaust 

exh raw exhaust 

exp expected quantity 

hi,idle condition at high-idle 

i an individual of a series 

idle condition at idle 

in quantity in 

init initial quantity, typically before an emission test 

j an individual of a series 

max the maximum (i.e., peak) value expected at the standard over a 

test interval; not the maximum of an instrument range 

meas measured quantity 

out quantity out 

part partial quantity 

PDP positive-displacement pump 

ref reference quantity 

rev revolution 

sat saturated condition 

slip PDP slip 

span span quantity 
SSV subsonic venturi 

std standard condition 

test test quantity 

test,alt alternate test quantity 

uncor uncorrected quantity 

zero zero quantity 

(f) Constants. (1) This part uses the following constants for the composition of dry air: 

Symbol Quantity mol/mol 

xArair amount of argon in dry air 0.00934 

xCO2air amount of carbon dioxide in dry air 0.000375 

xN2air amount of nitrogen in dry air 0.78084 

xO2air amount of oxygen in dry air 0.209445 

(2) This part uses the following molar masses or effective molar masses of chemical species:

Symbol Quantity g/mol 

(10-3·kg·mol-1) 

Mair molar mass of dry air1 28.96559 

MAr molar mass of argon 39.948 

MC molar mass of carbon 12.0107 

MCH3OH molar mass of methanol 32.04186

MC2H5OH molar mass of ethanol 46.06844

MC2H4O molar mass of acetaldehyde 44.05256

MC3H8 molar mass of propane 44.09562 

MC3H7OH molar mass of propanol 60.09502

MCO molar mass of carbon monoxide 28.0101 

MCH4 molar mass of methane 16.0425 

MCO2 molar mass of carbon dioxide 44.0095 

MH molar mass of atomic hydrogen 1.00794 

MH2 molar mass of molecular hydrogen 2.01588 

MH2O molar mass of water 18.01528 

MHCHO molar mass of formaldehyde 30.02598

MHe molar mass of helium 4.002602 

MN molar mass of atomic nitrogen 14.0067 

MN2 molar mass of molecular nitrogen 28.0134 

MNH3 molar mass of ammonia 17.03052

MNMHC effective C1 molar mass of nonmethane hydrocarbon2 13.875389 

MNMHCE

effective C1 molar mass of nonmethane hydrocarbon

equivalent2 13.875389 

MNOx effective molar mass of oxides of nitrogen3 46.0055 

MN2O molar mass of nitrous oxide 44.0128 

MO molar mass of atomic oxygen 15.9994 

MO2 molar mass of molecular oxygen 31.9988 

MS molar mass of sulfur 32.065 

MTHC effective C1 molar mass of total hydrocarbon2 13.875389 

MTHCE effective C1 molar mass of total hydrocarbon equivalent2 13.875389 1

See paragraph (f)(1) of this section for the composition of dry air. 

Deleted: equivalent 
2

The effective molar masses of THC, THCE, NMHC, and NMHCE are defined on a C1 basis and 

are based on an atomic hydrogen-to-carbon ratio, , of 1.85 (with β, γ, and δ equal to zero). 3

The effective molar mass of NOx is defined by the molar mass of nitrogen dioxide, NO2. 

(3) This part uses the following molar gas constant for ideal gases: 

Symbol Quantity J/(mol·K) 

(m2

·kg·s-2·mol-1·K-1) 

R molar gas constant 8.314472 

(4) This part uses the following ratios of specific heats for dilution air and diluted exhaust: 

Symbol Quantity [J/(kg·K)]/[J/(kg·K)] 

air ratio of specific heats for intake air 

or dilution air 

1.399 

dil ratio of specific heats for diluted 

exhaust 

1.399 

exh ratio of specific heats for raw 

exhaust 

1.385 

(g) Other acronyms and abbreviations. This part uses the following additional abbreviations and 

acronyms: 

ASTM American Society for Testing and Materials 

BMD bag mini-diluter 

BSFC brake-specific fuel consumption 

CARB California Air Resources Board 

CFR Code of Federal Regulations 

CFV critical-flow venturi 

CI compression-ignition 

CITT Curb Idle Transmission Torque 

CLD chemiluminescent detector 

CVS constant-volume sampler 

DF deterioration factor 

ECM electronic control module 

EFC electronic flow control 

EGR exhaust gas recirculation 

EPA Environmental Protection Agency 

FEL Family Emission Limit 

FID flame-ionization detector 

GC gas chromatograph 

GC-ECD gas chromatograph with an electron-capture detector 

GC-FID gas chromatograph with a flame ionization detector 

IBP initial boiling point 

ISO International Organization for Standardization 

LPG liquefied petroleum gas 

NDIR nondispersive infrared 

NDUV nondispersive ultraviolet 

NIST National Institute for Standards and Technology 

NMC nonmethane cutter 

PDP positive-displacement pump 

Deleted: by
PEMS portable emission measurement system 

PFD partial-flow dilution 

PMP Polymethylpentene 

pt. a single point at the mean value expected at the standard. 

PTFE polytetrafluoroethylene (commonly known as TeflonTM) 

RE rounding error 

RESS rechargeable energy storage system 

RMC ramped-modal cycle 

RMS root-mean square 

RTD resistive temperature detector 

SSV subsonic venturi 

SI spark-ignition 

THC-FID total hydrocarbon-flame ionization detector

UCL upper confidence limit 

UFM ultrasonic flow meter 

U.S.C. United States Code 

§1065.1010 Reference materials. 

The materials listed in this section are incorporated by reference into this part with the approval 

of the Director of the Federal Register under 5 U.S.C. 552(a) and 1 CFR part 51. To enforce any 

edition other than that specified in this section, a document must be published in the Federal 

Register and the material must be available to the public. All approved materials are available 

for inspection at the Air and Radiation Docket and Information Center (Air Docket) in the EPA 

Docket Center (EPA/ DC) at Rm. 3334, EPA West Bldg., 1301 Constitution Ave. NW., 

Washington, DC. The EPA/DC Public Reading Room hours of operation are 8:30 a.m. to 4:30 

p.m., Monday through Friday, excluding legal holidays. The telephone number of the EPA/DC 

Public Reading Room is (202) 566–1744, and the telephone number for the Air Docket is (202) 

566–1742. These approved materials are also available for inspection at the National Archives 

and Records Administration (NARA). For information on the availability of this material at 

NARA, call (202) 741–6030 or go to http:// www.archives.gov/federal_register/ 

code_of_federal_regulations/ ibr_locations.html. In addition, these materials are available from 

the sources listed below. 

(a) ASTM materials. Copies of these materials may be obtained from ASTM International, 100 

Barr Harbor Dr., P.O. Box C700, West Conshohocken, PA 19428–2959, or by calling (877) 

909–ASTM, or at http://www.astm.org. 

(1) ASTM D86–11b, Standard Test Method for Distillation of Petroleum Products at 

Atmospheric Pressure, IBR approved for §§1065.703, 1065.710. 

(2) ASTM D93–12, Standard Test Methods for Flash Point by Pensky- Martens Closed Cup 

Tester, IBR approved for §1065.703. 

(3) ASTM D445–12, Standard Test Method for Kinematic Viscosity of Transparent and Opaque 

Liquids (and Calculation of Dynamic Viscosity), IBR approved for §1065.703. 

(4) ASTM D613–10a, Standard Test Method for Cetane Number of Diesel Fuel Oil, IBR 

approved for §1065.703. 

(5) ASTM D910–11, Standard Specification for Aviation Gasolines, IBR approved for 

§1065.701. 

(6) ASTM D975–12a, Standard Specification for Diesel Fuel Oils, IBR approved for §1065.701. 

Comment [CAL21]: Review before FRM to 

make sure all methods are the latest published 

version. 

Deleted: 07a

Deleted: 09 (Approved December 15, 2009)

Deleted: 09 (Approved July 1, 2009)

Deleted: 05

Deleted: 07

Deleted: 07b
(7) ASTM D1267–02 (Reapproved 2007), Standard Test Method for Gage Vapor Pressure of 

Liquefied Petroleum (LP) Gases (LP-Gas Method), IBR approved for §1065.720. 

(8) ASTM D1319–10, Standard Test Method for Hydrocarbon Types in Liquid Petroleum 

Products by Fluorescent Indicator Adsorption, IBR approved for §1065.710. 

(9) ASTM D1655–12, Standard Specification for Aviation Turbine Fuels, IBR approved for 

§1065.701. 

(10) ASTM D1837–11, Standard Test Method for Volatility of Liquefied Petroleum (LP) Gases, 

IBR approved for §1065.720. 

(11) ASTM D1838–12, Standard Test Method for Copper Strip Corrosion by Liquefied 

Petroleum (LP) Gases, IBR approved for §1065.720. 

(12) ASTM D1945–03 (Reapproved 2010), Standard Test Method for Analysis of Natural Gas 

by Gas Chromatography, IBR approved for §1065.715. 

(13) ASTM D2158–11, Standard Test Method for Residues in Liquefied Petroleum (LP) Gases, 

IBR approved for §1065.720. 

(14) ASTM D2163–07, Standard Test Method for Analysis of Liquefied Petroleum (LP) Gases 

and Propene Concentrates by Gas Chromatography, IBR approved for §1065.720. 

(15) ASTM D2598–02 (Reapproved 2007), Standard Practice for Calculation of Certain Physical 

Properties of Liquefied Petroleum (LP) Gases from Compositional Analysis, IBR approved for 

§1065.720. 

(16) ASTM D2622–10, Standard Test Method for Sulfur in Petroleum Products by Wavelength 

Dispersive X-ray Fluorescence Spectrometry, IBR approved for §§1065.703, 1065.710. 

(17) ASTM D2713–12, Standard Test Method for Dryness of Propane (Valve Freeze Method), 

IBR approved for §1065.720. 

(18) ASTM D2784–11, Standard Test Method for Sulfur in Liquefied Petroleum Gases (OxyHydrogen Burner or Lamp), IBR approved for §1065.720. 

(19) ASTM D2880–03 (Reapproved 2010), Standard Specification for Gas Turbine Fuel Oils, 

IBR approved for §1065.701. 

(20) ASTM D2986–95a (Reapproved 1999), Standard Practice for Evaluation of Air Assay 

Media by the Monodisperse DOP (Dioctyl Phthalate) Smoke Test, IBR approved for §1065.170. 

(21) ASTM D3231–11, Standard Test Method for Phosphorus in Gasoline, IBR approved for 

§1065.710. 

(22) ASTM D3237–12, Standard Test Method for Lead in Gasoline By Atomic Absorption 

Spectroscopy, IBR approved for §1065.710. 

(23) ASTM D4052–11, Standard Test Method for Density and Relative Density of Liquids by 

Digital Density Meter, IBR approved for§1065.703. 

(24) ASTM D4629-12, Standard Test Method for Trace Nitrogen in Liquid Petroleum 

Hydrocarbons by Syringe/Inlet Oxidative Combustion and Chemiluminescence Detection, IBR 

approved for §1065.655.

(25) ASTM D4814–11b, Standard Specification for Automotive Spark-Ignition Engine Fuel, 

IBR approved for §1065.701.

(26) ASTM D4815-09, Standard Test Method for Determination of MTBE, ETBE, TAME, 

DIPE, tertiary-Amyl Alcohol and C1 to C4 Alcohols in Gasoline by Gas Chromatography, IBR 

approved for §1065.710.

Deleted: 03

Deleted: 07e01

Deleted: 02a (Reapproved 2007)

Deleted: 07

Deleted: 05

Deleted: 05

Deleted: 07

Deleted: 91 (Reapproved 2001)

Deleted: 06

Comment [CAL22]: Method has been withdrawn 

by ASTM. 

Deleted: 07

Deleted: 06e01

Deleted: 96e01 (Reapproved 2002)

Deleted: 07a
(27) ASTM D5186–03 (Reapproved 2009), Standard Test Method for Determination of the 

Aromatic Content and Polynuclear Aromatic Content of Diesel Fuels and Aviation Turbine Fuels 

By Supercritical Fluid Chromatography, IBR approved for §1065.703. 

(28) ASTM D5191–12, Standard Test Method for Vapor Pressure of Petroleum Products (Mini 

Method), IBR approved for §1065.710. 

(29) ASTM D5291–10, Standard Test Method for Instrumental Determination of Carbon, 

Hydrogen, and Nitrogen in Petroleum Products and Lubricants, IBR approved for §1065.655.

(30) ASTM D5599–00 (Reapproved 2010), Standard Test Method for Determination of 

Oxygenates in Gasoline by Gas Chromatography and Oxygen Selective Flame Ionization 

Detection, IBR approved for §1065.655.

(31) ASTM D5762-12 Standard Test Method for Nitrogen in Petroleum and Petroleum Products 

by Boat-Inlet Chemiluminescence, IBR approved for §1065.655.

(32) ASTM D5797–07, Standard Specification for Fuel Methanol (M70– M85) for Automotive 

Spark-Ignition Engines, IBR approved for §1065.701. 

(33) ASTM D5798–11, Standard Specification for Fuel Ethanol (Ed75– Ed85) for Automotive 

Spark-Ignition Engines, IBR approved for §1065.701. 

(34) ASTM D6615–11a, Standard Specification for Jet B Wide-Cut Aviation Turbine Fuel, IBR 

approved for §1065.701. 

(35) ASTM D6751–12, Standard Specification for Biodiesel Fuel Blend Stock (B100) for 

Middle Distillate Fuels, IBR approved for §1065.701. 

(36) ASTM D6985–04a, Standard Specification for Middle Distillate Fuel Oil—Military Marine 

Applications, IBR approved for §1065.701. 

(37) ASTM F1471–09, Standard Test Method for Air Cleaning Performance of a HighEfficiency Particulate Air Filter System, IBR approved for §1065.1001. 

(b) California Air Resources Board material. Copies of these materials may be obtained from 

the California Air Resources Board, Haagen-Smit Laboratory, 9528 Telstar Ave., El Monte, CA 

91731–2908, or by calling (800) 242–4450, or at http://www.arb.ca.gov. 

(1) California Non-Methane Organic Gas Test Procedures, Amended July 30, 2002, Mobile 

Source Division, California Air Resources Board, IBR approved for §1065.805. 

(2) [Reserved] 

(c) Institute of Petroleum material. Copies of these materials may be obtained from the Energy 

Institute, 61 New Cavendish St., London, W1G 7AR, UK, or by calling +44–(0)20–7467–7100, 

or at http://www.energyinst.org. 

(1) IP–470, 2005, Determination of aluminum, silicon, vanadium, nickel, iron, calcium, zinc, and 

sodium in residual fuels by atomic absorption spectrometry, IBR approved for §1065.705. 

(2) IP–500, 2003, Determination of the phosphorus content of residual fuels by ultra-violet 

spectrometry, IBR approved for §1065.705. 

(3) IP–501, 2005, Determination of aluminum, silicon, vanadium, nickel, iron, sodium, calcium, 

zinc and phosphorus in residual fuel oil by ashing, fusion and inductively coupled plasma 

emission spectrometry, IBR approved for §1065.705. 

(d) ISO material. Copies of these materials may be obtained from the 

International Organization for Standardization, 1, ch. de la Voie-Creuse, CP 56, CH–1211 

Geneva 20, Switzerland, or by calling +41–22–749–01–11, or at http://www.iso.org. 

(1) ISO 2719:2002, Determination of flash point—Pensky-Martens closed cup method, IBR 

approved for §1065.705. 

Deleted: 25

Deleted: 26

Deleted: 07

Deleted: 27

Deleted: 2

Deleted: 8

Deleted: 07

Deleted: 29

Deleted: 06

Deleted: 0

Deleted: 07b

Deleted: 1

Comment [CAL23]: Method has been withdrawn 

by ASTM. 

Deleted: 2

Deleted: 93 (Reapproved 2001)
(2) ISO 3016:1994, Petroleum products—Determination of pour point, IBR approved for 

§1065.705. 

(3) ISO 3104:1994/Cor 1:1997, Petroleum products—Transparent and opaque liquids—

Determination of kinematic viscosity and calculation of dynamic viscosity, IBR approved for 

§1065.705. 

(4) ISO 3675:1998, Crude petroleum and liquid petroleum products— Laboratory determination 

of density— Hydrometer method, IBR approved for §1065.705. 

(5) ISO 3733:1999, Petroleum products and bituminous materials— Determination of water—

Distillation method, IBR approved for §1065.705. 

(6) ISO 6245:2001, Petroleum products—Determination of ash, IBR approved for §1065.705. 

(7) ISO 8217:2005, Petroleum products—Fuels (class F)—Specifications of marine fuels, IBR 

approved for §1065.705. 

(8) ISO 8754:2003, Petroleum products—Determination of sulfur content—Energy-dispersive 

X-ray Fluorescence spectrometry, IBR approved for §1065.705. 

(9) ISO 10307–2:1993, Petroleum products—Total sediment in residual fuel oils—Part 2: 

Determination using standard procedures for ageing, IBR approved for §1065.705. 

(10) ISO 10370:1993/Cor 1:1996, Petroleum products—Determination of carbon residue—

Micro method, IBR approved for §1065.705. 

(11) ISO 10478:1994, Petroleum products—Determination of aluminium and silicon in fuel 

oils—Inductively coupled plasma emission and atomic absorption spectroscopy methods, IBR 

approved for §1065.705. 

(12) ISO 12185:1996/Cor 1:2001, Crude petroleum and petroleum products—Determination of 

density—Oscillating U-tube method, IBR approved for §1065.705. 

(13) ISO 14596:2007, Petroleum products—Determination of sulfur content—Wavelengthdispersive X-ray fluorescence spectrometry, IBR approved for §1065.705. 

(14) ISO 14597:1997, Petroleum products—Determination of vanadium and nickel content—

Wavelength dispersive X-ray fluorescence spectrometry, IBR approved for §1065.705. 

(15) ISO 14644–1:1999, Cleanrooms and associated controlled environments, IBR approved for 

§1065.190. 

(e) NIST material. Copies of these materials may be obtained from the National Institute of 

Standards and Technology (NIST) by calling (800) 553–6847 or from the U.S. Government 

Printing Office (GPO). To purchase a NIST publication you must have the order number. Order 

numbers are available from the Public Inquiries Unit at (301) 975–NIST. Mailing address: 

Public Inquiries Unit, NIST, 100 Bureau Dr., Stop 1070, Gaithersburg, MD 20899–1070. If you 

have a GPO stock number, you can purchase printed copies of NIST publications from GPO. 

GPO orders may be: Mailed to the U.S. Government Printing Office, P.O. Box 979050, St. 

Louis, MO 63197–9000, placed by telephone at (866) 512–1800 (DC Area only: (202) 512–

1800), or faxed to (202) 512–2104. More information can also be found at http://www.nist.gov. 

(1) NIST Special Publication 811, 1995 Edition, Guide for the Use of the International System of 

Units (SI), Barry N. Taylor, Physics Laboratory, IBR approved for §§1065.20, 1065.1001, 

1065.1005. 

(2) NIST Technical Note 1297, 1994 Edition, Guidelines for Evaluating and Expressing the 

Uncertainty of NIST Measurement Results, Barry N. Taylor and Chris E. Kuyatt, IBR approved 

for §1065.1001. 
(f) SAE material. Copies of these materials may be obtained from the Society of Automotive 

Engineers International, 400 Commonwealth Dr., Warrendale, PA 15096–0001, or by calling 

(724) 776–4841, or at http://www.sae.org. 

(1) SAE 770141, 1977, Optimization of Flame Ionization Detector for Determination of 

Hydrocarbon in Diluted Automotive Exhausts, Glenn D. Reschke, IBR approved for §1065.360. 

(2) SAE J1151, Methane Measurement Using Gas Chromatography, Revised September 2011, 

IBR approved for §§1065.267 and 1065.750.

Deleted: 2001

Deleted: [Reserved]
Subpart L—Methods for Unregulated and Special Pollutants

§1065.1101 Applicability.

This subpart specifies procedures that may be used to measure emission constituents that are not 

measured (or not separately measured) by the test procedures in the other subparts of this part. 

These procedures are included to facilitate consistent measurement of unregulated pollutants 

primarily for purposes other than compliance with emission standards. Unless otherwise 

specified in the standard-setting part, use of these procedures is optional and does not replace any 

requirements in the rest of this part. 

SEMI-VOLATILE ORGANIC COUMPOUNDS

§1065.1103 General provisions for SVOC measurement.

The provisions of §§1065.1103 through 1065.1111 specify procedures for the measurement of 

semi-volatile organic compounds (SVOC) along with PM. The provisions of these sections 

specify how to collect a sample of the SVOCs during exhaust testing procedures, as well as how 

to use wet chemistry techniques to extract SVOCs from the sample media for analysis. Note that 

the precise method you use will depend on the category of SVOCs being measured. For 

example, the method used to measure polynuclear aromatic hydrocarbons (PAHs) will differ 

slightly from the method used to measure dioxins.

(a) Laboratory cleanliness is especially important throughout the course of SVOC testing. 

Thoroughly clean all sample train components and glassware before testing to avoid sample 

contamination.

(b) Throughout the course of your testing we recommend that media blanks be analyzed for each 

batch of media (sorbent, filters, etc.) that is prepared for testing. Blank sorbent modules with 

inlet and outlet covered (i.e., field blanks) should periodically accompany the test sample train 

throughout the course of a test, including the sample train and sorbent module disassembly, 

sample packaging, and storage. Use good engineering judgment to determine the frequency of 

field blanks. During testing, the field blank sample train should reside in close proximity to the 

sampler.

(c) We recommend the use of isotope dilution techniques, including the use of isotopically 

labeled surrogate, internal, alternate, and injection standards.

(d) If your target analytes degrade when exposed to ultraviolet radiation (such as nPAH), 

perform these procedures in the dark or with ultraviolet filters installed over the lights.

(e) Follow standard analytic chemistry methods for aspects of the analysis not specified.

(f) The following definitions and abbreviations apply for SVOC measurements:

(1) Soxhlet extraction means the extraction method invented by Franz von Soxhlet, in which the 

sample is placed in a thimble and rinsed repeatedly with a recycle of the extraction solvent.

(2) XAD-2 means a hydrophobic cross linked polystyrene copolymer resin adsorbent known 

commercially as Amberlite® XAD®-2, or an equivalent adsorbent.

(3) Semi-volatile organic compound (SVOC) means an organic compound that is sufficiently 

volatile to exist in vapor form in engine exhaust, but that readily condenses to liquid or solid 

form under atmospheric conditions. Most SVOCs have at least 14 carbon atoms per molecule 

and have a boiling point between 240°C and 400°C. SVOCs include dioxin, quinone, and nitroPAH compounds. They may be a natural byproduct of combustion or created post combustion. 
Note that SVOCs may be detected as hydrocarbons and/or PM using the measurement 

procedures specified in this part; in other words, some fraction of measured mass of 

hydrocarbons and/or PM may be SVOCs.

(4) Kuderna-Danish concentrator means laboratory glassware known by this name that consists 

of an air-cooled condenser on top of an extraction bulb.

(5) Dean-Stark trap means laboratory glassware known by this name that uses a reflux condenser 

to collect water from samples extracted under reflux.

(6) PUF means polyurethane foam.

(7) Isotopically labeled means relating to a compound in which either all of the hydrogen atoms 

are replaced with the atomic isotope hydrogen-2 (deuterium) or one of the carbon atoms at a 

defined position in the molecule is replaced with the atomic isotope carbon-13.

§1065.1105 Sampling system design.

(a) General. We recommend that you design your SVOC batch sampler to extract sample from 

undiluted emissions to minimize the amount of SVOCs lost to the system. To the extent 

practical, adjust sampling times based on the rate of emission of target analytes from the engine 

to obtain analyte concentrations above the limit of detection. In some instances you may need to 

run repeat test cycles without replacing the sample media or disassembly of the batch sampler.

(b) Sample probe, transfer lines, and sample media holder design and construction. The 

sampling system should consist of a sample probe, transfer line, PM filter holder, cooling coil, 

sorbent module, and condensate trap. Construct sample probes, transfer lines, and sample media 

holders that have inside surfaces of Nickel, Titanium or another nonreactive material capable of 

withstanding raw exhaust gas temperatures. All joints in the hot zone of the system should be 

sealed with gaskets made of nonreactive material similar to that of the sample train components. 

Teflon gaskets may be used in the cold zone. We recommend keeping the sampling system 

length as short as possible by locating all components as close to probes as practical to minimize 

the surface exposed to the exhaust.

(c) Sample system configuration. This paragraph (c) specifies the components necessary to 

collect SVOC samples, along with our recommended design parameters. Where you do not 

follow our recommendations, use good engineering judgment to design your sampling system so 

that it does not result in loss of SVOC during sampling. The sampling system should contain the 

following components in series in the order listed:

(1) Sample probe. Use a sample probe similar to the PM sample probe specified in subpart B of 

this part. We recommend that you heat the sample probe with a set point no higher the 200 °C. 

Note that heat from the engine exhaust may cause the probe temperature to exceed 200°C at 

some points during the test.

(2) Filter holder. Use a PM filter holder similar to type of holder specified in subpart B of this 

part, although you will likely need to use a larger size to accommodate the high sample flow 

rates. We recommend the use of 110 mm filter for the testing of engines that utilize exhaust after 

treatment for removal of PM and 293 mm filters for engines that do not. You may heat the filter 

holder, but we recommend that your set point does not exceed 200°C. Note that this differs from 

normal PM sampling procedures which maintain the filter at a much lower temperature to 

capture a significant fraction of exhaust SVOCs on the filter. In this method SVOCs that pass 

through the filter will be collected on the downstream sorbent module. 
(3) Cooling coil. Use good engineering judgment to design a cooling coil (to be used with the 

water bath described in paragraph (e) of this section) that will drop the sample temperature to 

approximately 5°C. Note that downstream of the cooling coil, the sample will be a mixture of a 

vapor phase hydrocarbons in CO2 and air and a primarily aqueous liquid phase. 

(4) Sorbent and sorbent module. Use a hydrophobic sorbent in a sealed sorbent module. Note 

that this sorbent module is intended to be the final stage for collecting the SVOC sample and 

should be sized accordingly. We recommend sizing the module to hold 40 g of XAD-2 along 

with polyurethane (PUF) plugs at either end of the module.

(5) Condensate trap/drain. Include a condensate trap to separate the aqueous liquid phase from 

the gas stream. We recommend using a peristaltic pump to remove water from the condensate 

trap over the course of the test to prevent build up of the condensate. Note that for some tests it 

may be appropriate to collect this water for analysis.

(d) Sampler flow control. For testing using the recommended filter and sorbent module sizes, we 

recommended targeting an average sample flow rate of 70 l/min to maximize SVOC collection. 

The sampler must be designed to maintain proportional sampling throughout the test. Verify

proportional sampling after an emission test as described in §1065.545.

(e) Water bath. Design the sample system with a water bath in which the cooling coil, sorbent 

module, and condensate trap will be submerged. Use a heat exchanger or ice to maintain the 

bath temperature at (3 to 7) °C.

§1065.1107 Sample media and sample system preparation; sampler assembly.

This section describes the types of sample media to be used as well as the cleaning procedure 

required to prepare the media and wetted sample surfaces for sampling.

(a) Sample media. The sampling system uses two types of sample media in series: the first to 

simultaneously capture the PM and some of the SVOCs, and a second to capture SVOCs that 

remain in the gas phase. Use the following sample media for capture of PM and gas phase 

SVOCs:

(1) For capture of PM, use pure quartz filters that do not contain any binder. Size the filter 

diameter to account for the expected PM emission rate, sample flow rate, and number of repeat 

tests to minimize filter change intervals. Note that when repeating test cycles to increase sample 

mass, you may replace the filter without replacing the sorbent or otherwise disassembling the

batch sampler. In those cases include all filters in the extraction.

(2) For capture of gaseous SVOCs, utilize XAD-2 resin contained between two PUF plugs.

(b) Sample media and sampler preparation. Prepare pre-cleaned PM filters and pre-cleaned 

PUF/XAD-2 as needed. If the media is not to be used immediately after cleaning, store it in 

containers protected from light and ambient air.

(1) Pre-clean the filters via Soxhlet extraction with methylene chloride for 24 hours and dry over 

dry nitrogen in a low temperature vacuum oven.

(2) Pre-clean PUF and XAD-2 via a series of Soxhlet extractions: 8 h with water, 22 h with 

methanol, 22 h with methylene chloride, and 22 hours with toluene followed by drying with 

nitrogen.

(3) Clean sampler components including the probe, filter holder, condenser, sorbent module, and 

condensate collection vessel by rinsing three times with methylene chloride followed by three 

rinses with toluene. Prepare pre-cleaned aluminum foil for capping the probe inlet of the 

sampler after the sample train has been assembled.
(c) Sorbent spiking. Use good engineering judgment to verify the extent to which your 

extraction methods recover SVOCs absorbed to the sample media. We recommend spiking the 

XAD-2 resin with a surrogate standard prior to testing with a carbon-13 or hydrogen-2 

isotopically labeled standard for each of the class of analytes targeted for analysis. Perform this 

spiking as follows: 

(1) Insert the lower PUF plug into the bottom of the sorbent module.

(2) Add half of one portion of XAD-2 resin to the module and spike the XAD-2 in the module 

with the standard.

(3) Wait 1 hour for the solvent from the standard(s) to evaporate and then add the remaining 20 g 

of the XAD-2 resin to the module followed by the top PUF plug.

(4) Cover the inlet and outlet of the sorbent module with pre-cleaned aluminum foil.

(d) Sample train assembly. Upon completion of the sample media and sampler preparation, 

assemble the condensate trap, cooling coil, filter holder with filter, and sample probe to the 

sorbent module and lower assembly into the reservoir. Cover the probe inlet with pre-cleaned 

aluminum foil.

§1065.1109 Post-test sampler disassembly and sample extraction.

This section describes the process for sample train disassembly, sample train rinsing, sample 

extraction, and sample clean-up.

(a) Sample train disassembly. Disassemble the sample train in a clean environment upon 

completion of testing. Prepare to extract the SVOCs as follows:

(1) Remove the PM filter, PUF, and all of the XAD-2 from the sample train and place them into 

a Soxhlet extraction thimble. If the sample media are to be stored, store them at ≤ 37 °C.

(2) Rinse sample train wetted surfaces upstream of the condensate trap with acetone followed by 

toluene (or a comparable solvent system), ensuring that all of the solvent that remains in liquid 

phase is collected (note that a fraction of the acetone and toluene will likely be lost via 

evaporation during mixing.) Rinse with solvent volumes that are sufficient to cover the all of the 

surfaces exposed to sample during testing. We recommend three fresh solvent rinses with 

acetone and two with toluene. We recommend rinse volumes of 60 mL per rinse for all sample 

train components except the condenser coil, of which you should use 200 mL per rinse. Keep 

the acetone rinsate separate from the toluene rinsate to the extent practicable. Rinsate fractions 

should be stored separately in glass bottles that have been pre-rinsed with acetone, hexane, and 

toluene (or bottles purchased pre-cleaned). 

(3) Use good engineering judgment to determine if you should analyze the aqueous condensate 

phase for SVOCs. If you determine that analysis is necessary, use toluene to perform a liquidliquid extraction of the SVOCs from the collected aqueous condensate using a sepratory funnel 

or equivalent. Add the toluene from this aqueous extraction to the toluene rinsate fraction 

mentioned in paragraph (a)(2) of this section.

(4) Reduce rinsate solvent volumes as needed using a Kuderna-Danish concentrator or rotary 

evaporator and retain these rinse solvents for reuse during sample media extraction for the same 

test. Care should be taken when concentrating via rotary evaporation to avoid loss of low 

molecular weight analytes.

(b) Sample extraction. Extract the SVOCs from the sorbent using Soxhlet extraction extraction 

as described in this paragraph (b). To accommodate the Soxhlet extractions of all SVOCs from a 

single sample, two 16 hour extractions are required. This will reduce the possibility of loss of 
low molecular weight SVOCs and promote water removal. We recommend performing the first 

extraction with acetone/hexane and the second using toluene (or an equivalent solvent system).

(1) We recommend equipping the Soxhlet extractor with a Dean-Stark trap to facilitate the 

removal of residual water from the sample train rinse. The Soxhlet apparatus must be large 

enough to allow extraction of the PUF, XAD-2, and filter in a single batch. Include in the 

extractor setup a glass thimble with a coarse or extra coarse sintered glass bottom. Pre-clean the 

extractor using proper glass cleaning procedures. We recommend that the Soxhlet apparatus be 

cleaned with a 4 to 8 hr Soxhlet extraction with methylene chloride at a cycling rate of 3 cycles 

per hour. Discard the solvent used for pre-cleaning (no analysis is necessary).

(2) Load the extractor thimble before placing it in the extractor by first rolling the PM filter 

around the inner circumference of the thimble with the sampled side facing in. Push one PUF 

plug down into the bottom of the thimble then add approximately half of the XAD-2. The Then 

spike the XAD-2 in the thimble with the isotopically labeled extraction standards of known 

mass. Target the center of the XAD-2 bed for extraction standard delivery. We recommend 

using multiple isotopically labeled extraction standards that cover the range of target analytes. 

Generally this means that you should use isotopically labeled standards at least for the lowest 

and highest molecular weight analytes for each category of compounds (such as PAHs and 

dioxins). These extraction standards monitor the efficiency of the extraction and are also used to 

determine analyte concentrations after analysis. Upon completion of spiking, add the remaining 

XAD-2 to the thimble followed by the remaining PUF plug. Then place the thimble into the 

extractor.

(3) For the initial extraction, combine the concentrated acetone rinses (from the sample train in 

paragraph (a) of this section) with enough hexane to bring the solvent volume up to the target 

level of 700 mL. Assemble the extractor and turn on the heating controls and cooling water. 

Allow the sample to reflux for 16 hours with the rheostat adjusted so that the extraction cycles at 

a rate of 3.0±0.5 cycles per hour. Drain the water from the Dean-Stark trap as it accrues by 

opening the stopcock on the trap. Discard this water unless it is to be analyzed. In most cases, 

any water present will be removed within approximately 2 hours of the start of the extraction.

(4) Upon completion of the initial extraction, remove the solvent and concentrate it to 4.0 ±0.5 

mL using a Kuderna-Danish concentrator that includes a condenser such as a three-ball Snyder 

column with venting dimples and graduated collection tube. The use of this concentrator will 

minimize evaporative loss of lower molecular weight analytes.

(i) Rinse the round bottom flask of the extractor with 60 to 100 mL of hexane and add the rinsate

to this concentrated extract.

(ii) Concentrate the mixture to 4 ±0.5 mL using a Kuderna-Danish concentrator or similar 

concentration apparatus.

(iii) Repeat paragraphs (i) and (ii) of this section 3 times or as necessary, to remove all of the 

residual solvent from the extractor round bottom flask, concentrating the final rinse to 4 ±0.5 

mL.

(5) For the second extraction, combine the toluene rinses (from the sample train in paragraph (a) 

of this section) with any additional toluene needed to bring the solvent volume up to the target 

level of 700 mL. As noted in this paragraph (a) of this section, you may need to concentrate the 

rinse prior to addition to the extraction apparatus if the rinse solvent volume is too large. Allow 

the sample to reflux for 16 hours with the rheostat adjusted so that the extraction cycles at a rate 
of 3.0 ±0.5 cycles per hour. Although little or no water should be present during this stage, 

check the Dean-Stark trap during the first 2 hours of the extraction.

(6) Upon completion of the second extraction, remove the solvent and concentrate it to 4 ±0.5 

mL as described in paragraph (4) of this section. Using hexane from paragraph (4) of this 

section as the rinse solvent, effectively performs a solvent exchange of toluene with hexane.

(7) Combine the concentrated extract from paragraph (b)(4) of this section with the concentrated 

extract from paragraph (6) of this section. Divide the extract into a number of fractions based on 

the number of analyses to be performed. Perform the separate sample clean up described in 

paragraph (c) of this section as needed for each fraction.

(c) Sample clean up. This paragraph (c) describes how to perform sample cleaning to remove

unwanted SVOCs (that is, those SVOCs which you are not analyzing for) and solids from the 

sample extract before analysis. This process, which is known as “sample clean up, reduces the 

potential for interference or co-elution of peaks during analytical analysis. Before proceeding 

with the sample clean up, spike the extract with an alternate standard that contains a known mass 

of isotopically labeled compounds that are identical (with the exception of the labeling) to the 

target analytes. The number of compounds that make up the standard will be determined by the 

category of the target analyte compounds (such as PAHs or dioxin). For example, PAHs require 

the use of 4 compounds in the alternate standard to cover the 4 basic ring structures of PAHs (2-

ring, 3-ring, 4-ring, and 5-ring structures). These alternate standards are used to monitor the 

efficiency of the clean up procedure. Before sample clean up, concentrate the fractionated

sample to about 2 mL with a Kuderna-Danish concentrator or rotary evaporator, and then 

transfer the extract to an 8-mL test tube with hexane rinse. Concentrate to a volume of about 1 

mL using a Kuderna-Danish concentrator. Since there are several column chromatographic 

cleanup options available, use good engineering judgment to select one appropriate for your 

target analytes. Note that these clean-up techniques generally remove compounds based on their 

polarity. The clean up procedures given in paragraphs (c)(1) and (2) below are examples of 

clean-up techniques for PAHs and nitropolynuclear aromatic hydrocarbons (nPAHs).

(1) PAH clean up. The following method is appropriate for cleaning up extracts intended for 

analysis of PAHs:

(i) Pack a glass gravity column (250 mm x 10 mm recommended) by inserting a clean glass wool 

plug into the bottom of the column followed by the addition of 10 grams of activated silica gel in

methylene chloride. Tap the column to settle the silica gel, and then add a 1 cm layer of 

anhydrous sodium sulfate. Since variations among batches of silica gel may affect the elution 

volume of the various PAH, the volume of solvent required to completely elute all of the PAH 

must be verified by the analyst. The weight of the silica gel can then be adjusted accordingly.

(ii) Elute the column with 40 mL of hexane. The rate for all elutions should be about 2 mL/min

and you may use dry air or N2 to maintain the headspace slightly above atmospheric pressure to 

increase the elution rate. Discard the eluate just prior to exposure of the sodium sulfate layer to 

the air or N2, transfer the 1 mL sample extract onto the column using two additional 2 mL rinses 

of hexane to complete the transfer. Just prior to exposure of the sodium sulfate layer to the air or 

N2, begin elution of the column with 25 mL of hexane followed by 25 mL of 40 volume % 

methylene chloride in hexane. Collect the entire eluate and concentrate it to about 5 mL using 

the Kuderna-Danish concentrator or a rotary evaporator. Make sure that you do not evaporate all 

of the solvent from the extract during the concentration process. Transfer to a small sample vial 

using a hexane rinse and concentrate to 100 μL using a stream of nitrogen, gentle enough to not 
violently disturb the solvent. Store the extracts in a refrigerator at 4 °C or lower away from light 

until analysis.

(2) nPAH clean up. The following procedure, that was adapted from “Determination and 

Comparison of Nitrated-Polycyclic Aromatic Hydrocarbons Measured in Air and Diesel 

Particulate Reference Materials” (Bamford, H.A., et al, Chemosphere, Vol. 50, Issue 5, pages 

575 – 587), is an appropriate method to clean up extracts intended for analysis of nPAHs:

(i) Condition an aminopropyl solid phase extraction (SPE) cartridge by eluting it with 20 mL of 

20 volume % methylene chloride in hexane before use. Transfer the extract quantitatively to the 

SPE cartridge with at least two methylene chloride rinsings. Elute the extract through the SPE

cartridge by using 40 ml of 20 volume % methylene chloride in hexane to minimize potential 

interference of polar constituents. Then reduce the extract to 0.5 ml in hexane and subject the 

extract to normal-phase liquid chromatography using pre-prepared a 9.6 mm X 25 cm semipreparative Chromegabond® amino/cyano column, 5 μm particle size to isolate the nPAH 

fraction. The mobile phase is 20 volume % methylene chloride in hexane at a constant flow rate 

of 5 ml/min. Prior to each injection, the column should be back flashed with 60 ml of methylene 

chloride and then conditioned with 200 ml of 20 volume % methylene chloride in hexane. 

Collect the effluent and concentrate to about 2 mL using the Kuderna-Danish concentrator or a 

rotary evaporator. Transfer to a minivial using a hexane rinse and concentrate to 100 μL using a 

gentle stream of nitrogen. Store the extracts at 4°C or lower away from light until analysis.

§1065.1111 Sample analysis.

This subpart does not specify chromatographic or analytical methods to analyze extracts, because 

the selection of such methods is highly dependent on the nature of the target analytes. However, 

we recommend that prior to whichever sample analysis you choose, you spike the extract with an 

injection standard that contains a known mass of an isotopically labeled compound that is 

identical (with the exception of the labeling) to one of the target analytes. This injection

standard is used to monitor the efficiency of the analytical process by verifying the volume of 

sample injected for analysis.