40 CFR Part 1066 

Vehicle-Testing 

Procedures 

DRAFT Working 

Document

(LD Tier III NPRM changes in red, LD Tier III FRM changes in blue) 

11/12/13 
1. Part 1066 is revised to read as follows:

Part 1066—Vehicle-Testing Procedures 

Subpart A—Applicability and General Provisions 

1066.1 Applicability. 

1066.2 Submitting information to EPA under this part. 

1066.5 Overview of this part 1066 and its relationship to the standard-setting part. 

1066.10 Other procedures. 

1066.15 Overview of test procedures. 

1066.20 Units of measure and overview of calculations. 

1066.25 Recordkeeping. 

Subpart B—Equipment, Measurement Instruments, Fuel, and Analytical Gas 

Specifications 

1066.101 Overview. 

1066.105 Ambient controls and vehicle cooling fans.

1066.110 Equipment specifications for emission sampling systems.

1066.120 Measurement instruments.

1065.122 Data updating, recording, and control for measurement instruments.

1066.130 Measurement instrument calibrations and verifications.

1066.137 Linearity verification.

1066.140 Diluted exhaust flow calibration.

1066.145 Engine fluids, test fuels, analytical gases, and other calibration standards.

1066.150 Analyzer interference and quench verification limit.

 

Subpart C—Dynamometer Specifications 

1066.201 Dynamometer overview. 

1066.210 Dynamometers. 

1066.215 Summary of verification and calibration procedures for chassis dynamometers. 

1066.220 Linearity verification for chassis dynamometer systems. 

1066.225 Roll runout and diameter verification procedure. 

1066.230 Time verification procedure. 

1066.235 Speed verification procedure. 

1066.240 Torque transducer calibration. 

1066.245 Response time verification. 

1066.250 Base inertia verification. 

1066.255 Parasitic loss verification. 

1066.260 Parasitic friction compensation evaluation. 

1066.265 Acceleration and deceleration verification. 

Deleted: verification and 
1066.270 Unloaded coastdown verification. 

1066.280 Daily dynamometer readiness verification. 

1066.290 Driver’s aid.

 Subpart D—Coastdown 

1066.301 Overview of coastdown procedures. 

1066.305 Coastdown procedures for motor vehicles at or below 14,000 pounds GVWR.

1066.310 Coastdown procedures for vehicles above 14,000 pounds GVWR. 

1066.320 Dynamometer road-load setting.

 Subpart E—Preparing Vehicles and Running an Exhaust Emission Test 

1066.401 Overview. 

1066.407 Vehicle preparation and preconditioning. 

1066.410 Dynamometer test procedure. 

1066.420 Vehicle operation. 

1066.425 Test preparation. 

1066.430 Performing emission tests.

Subpart F—Hybrids and Electric Vehicles

1066.501 Overview. 

 Subpart G—Calculations 

1066.601 Overview. 

1066.610 Mass-based and molar-based exhaust emission calculations. 

1066.620 Dilution air background correction.

1066.630 NOx intake-air humidity correction.

1066.640 Removed water correction.

1066.650 Flow meter calibration calculations.

1066.652 PDP, SSV, and CFV flow rate calculations.

1066.665 NMOG determination.

1066.695 Data requirements.

Subpart H—Cold-Temperature Test Procedures

1066.701 Applicability and general provisions.

1066.710 Cold-testing procedures for measuring CO and NMHC emissions and determining fuel 

economy.

Subpart I—Exhaust Emission Test Procedures for Motor Vehicles

1066.801 Applicability and general provisions.

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1066.810 Road load power, test weight, and inertia weight class determination.

1066.814 Vehicle preparation.

1066.820 Exhaust emission test procedures for FTP emissions.

1066.822 Composite calculations for FTP exhaust emissions.

1066.830 Supplemental Federal Test Procedures; overview.

1066.831 Exhaust emission test procedures for aggressive driving.

1066.832 Exhaust emission test procedure for SC03 emissions.

1066.835 AC17 Air conditioning efficiency test procedure.

1066.839 Highway fuel economy test procedure.

1066.840 Fuel storage system leak test procedure.

Subpart J—[Reserved]

 Subpart K—Definitions and Other Reference Material 

1066.1001 Definitions. 

1066.1005 Symbols, abbreviations, acronyms, and units of measure. 

1066.1010 Reference materials. 

Authority: 42 U.S.C. 7401-7671q.

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Subpart A—Applicability and General Provisions 

§1066.1 Applicability. 

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

(1) Model year 2014 and later heavy-duty highway vehicles we regulate under 40 CFR part 1037 

that are not subject to chassis testing for exhaust emissions under 40 CFR part 86. 

(2) Model year 2022 and later highway vehicles (light-duty and heavy-duty) that are subject to 

chassis testing for exhaust emissions under 40 CFR part 86. See 40 CFR part 86 for provisions 

describing how to implement this part 1066.

(b) The procedures of this part may apply to other types of vehicles, 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 vehicles, 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 vehicles. In this part, we refer to each of these 

other parts generically as the “standard-setting part.” For example, 40 CFR part 1037 is the 

standard-setting part for heavy-duty highway vehicles and parts 86 and 600 are the standardsetting parts for light-duty vehicles. For vehicles subject to 40 CFR part 86, subpart S, treat 

subpart I of this part as belonging to 40 CFR part 86. This means that references to the standardsetting part include subpart I of this part.

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

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

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

(f) 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. 

§1066.2 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, or any other statements you make to us related to this part 1066. 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 engine 

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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 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 are 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 vehicles conform to the regulations. 

§1066.5 Overview of this part 1066 and its relationship to the standard-setting part. 

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

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

for a particular type of vehicle. Before using this part’s procedures, read the standard-setting 

part to answer at least the following questions: 

(1) What drive schedules must I use for testing? 

(2) Should I warm up the test vehicle 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. See 40 

CFR 1065.5 regarding requests to omit measurement of N2O and CH4 for vehicles, not subject to 

N2O or CH4 emission standards. 

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

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

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

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

(8) [Reserved]

(9) Are there any emission standards specified at particular 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: 

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information is available to give us a reasonable basis 

for estimating or approximating the vehicle’s 

emission rates

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and are there different emission standards or 

procedures that apply to field testing? ¶
Table 1 of §1066.5—Description of Part 1066 subparts. 

This subpart Describes these specifications or procedures 

Subpart A Applicability and general provisions. 

Subpart B Equipment for testing. 

Subpart C Dynamometer specifications. 

Subpart D Coastdowns for testing. 

Subpart E How to prepare your vehicle and run an emission test. 

Subpart F How to test hybrid vehicles. 

Subpart G Test procedure calculations. 

Subpart H Cold temperature testing.

Subpart I Exhaust emission test procedures for motor vehicles.

Subpart J Reserved.

Subpart K Definitions and reference material.

§1066.10 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 noted 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 vehicles 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 

vehicles 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 as described in 40 CFR 1065.10(c). All the test procedures noted 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 40 CFR 1065.10(c)(2) and "alternate procedures" are those allowed by 40 CFR 

1065.10(c)(7). If we require you to request approval to use other procedures under this 

paragraph (c), you may not use them until we approve your request. 

§1066.15 Overview of test procedures. 

This section outlines the procedures to test vehicles that are subject to emission standards. 

(a) In the standard-setting part, we set emission standards in g/mile (or g/km), 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. 

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both, 

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

mathematically to be equivalent on a carbon-mass basis. 

(v) Nonmethane organic gases, NMOG, which are calculated either from fully or partially 

speciated measurement of hydrocarbons including oxygenates, or by adjusting measured NMHC 

values based on fuel oxygenate properties.

(3) Particulate mass, PM. 

(4) Carbon monoxide, CO.

(5) Carbon dioxide, CO2.

(6) Methane, CH4.

(7) Nitrous oxide, N2O.

(8) Formaldehyde, CH2O.

(b) Note that some vehicles may not be 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) The provisions of this part apply for chassis dynamometer testing where vehicle speed is

controlled to follow a prescribed duty cycle while simulating vehicle driving through the 

dynamometer’s road-load settings. We generally set emission standards over test intervals 

and/or drive schedules, as follows: 

(1) Vehicle operation. Testing involves measuring emissions and miles travelled while operating

the vehicle on a chassis dynamometer. Refer to the definitions of “duty cycle” and “test 

interval” in §1066.1001. Note that a single drive schedule may have multiple test intervals and 

require weighting of results from multiple test intervals to calculate a composite distance-based 

emission 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, as applicable. You may extract and store a proportional sample of exhaust in an appropriate 

container, such as a bag, and then measure NOx, HC, CO, CO2, CH4, N2O, and CH2O 

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, subject to the provisions of 40 CFR 1065.201. 

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how test intervals are defined for field testing.

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(d) Refer to the standard-setting part for calculations to determine g/mile emission rates. 

(e) You must use good engineering judgment for all aspects of testing under this part. While this 

part highlights several specific cases where good engineering judgment is especially relevant, the 

requirement to use good engineering judgment is not limited to those provisions where we 

specifically re-state this requirement. 

§1066.20 Units of measure and overview of calculations. 

(a) System of units. The procedures in this part follow both conventional English Units and the 

International System of Units (SI), as detailed in NIST Special Publication 811, which we 

incorporate by reference in §1066.1010. Except where specified, equations work with any 

system of units. Where the equations depend on the use of specific units, these units are 

identified. 

(b) Units conversion. Use good engineering judgment to convert units between measurement 

systems as needed. For example, if you measure vehicle speed as kilometers per hour and we 

specify a precision requirement in terms of miles per hour, convert your measured kilometer per 

hour value to miles per hour before comparing it to our specification. The following conventions 

are used throughout this document and should be used to convert units as applicable: 

(1) 1 hp = 33,000 ft·lbf/min = 550 ft·lbf/s = 0.7457 kW. 

(2) 1 lbf = 32.174 ft·lbm/s2 = 4.4482 N.

(3) 1 inch = 25.4 mm. 

(4) 1 mile = 1609.344 m.

(5) For ideal gases, 1 μmol/mol = 1 ppm.

(6) For ideal gases, 10 mmol/mol = 1 %.

(c) Temperature. We generally 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. Unless 

specified otherwise, always use absolute temperature values for multiplying or dividing by 

temperature. 

(d) 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. 

Always use absolute pressure values for multiplying or dividing by pressure.

(e) Rounding. The rounding provisions of 40 CFR 1065.20 apply for calculations in this part. 

This generally specifies that you round final values but not intermediate values. Use good 

engineering judgment to record the appropriate number of significant digits for all measurements. 

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

accuracy, repeatability, linearity, or noise specification. See 40 CFR 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 (such as X ±Y), target the associated control point to that single value (X). 

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

these examples, you would target the maximum pressure or 30 kPa, respectively.

(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”. 

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(g) Scaling of specifications with respect to an applicable standard. Because this part 1066 

applies to a wide range of vehicles and emission standards, some of the specifications in this part 

are scaled with respect to a vehicle’s applicable standard or weight. 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. Flow-weighted 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 flow-weighted mean 

concentration, because the CVS system itself flow-weights the bag concentration. 

§1066.25 Recordkeeping. 

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

Refer to the standard-setting part and §1066.695 regarding specific recordkeeping requirements. 

(b) You must promptly send us organized, written records in English if we ask for them. We 

may review them at any time.

(c) We may waive specific reporting or recordkeeping requirements we determine to be 

unnecessary for the purposes of this part and the standard-setting part. Note that while we will 

generally keep the records required by this part, we are not obligated to keep records we 

determine to be unnecessary for us to keep. For example, while we require you to keep records 

for invalid tests so that we may verify that your invalidation was appropriate, it is not necessary 

for us to keep records for our own invalid tests.

Deleted: e

Deleted: Refer to 40 CFR 1065.602 for 

information needed to estimate and calculate flowweighted means.

Deleted: If the standard-setting part does not 

specify recordkeeping requirements, store these 

records in any format and on any media and 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, Measurement Instruments, Fuel, and Analytical Gas 

Specifications 

§1066.101 Overview. 

(a) This subpart addresses equipment related to emission testing, as well as test fuels and 

analytical gases. This section addresses emission sampling and analytical equipment, test fuels, 

and analytical gases. 

(b) The provisions of 40 CFR part 1065 specify engine-based procedures for measuring 

emissions. Except as specified otherwise in this part, the provisions of 40 CFR part 1065 apply 

for testing required by this part as follows: 

(1) The provisions of 40 CFR part 1065, subpart B, describe equipment specifications for 

exhaust dilution and sampling systems; these specifications apply for testing under this part as 

described in §1066.110. 

(2) The provisions of 40 CFR part 1065, subpart C, describe specifications for measurement 

instrument; these specifications apply for testing under this part as described in §1066.120. 

(3) The provisions of 40 CFR part 1065, subpart D, describe specifications for measurement 

instrument calibrations and verifications; these specifications apply for testing under this part as 

described in §1066.130. 

(4) The provisions of 40 CFR part 1065, subpart H, describe specifications for fuels, engine 

fluids, and analytical gases; these specifications apply for testing under this part as described in 

§1066.145.

(5) The provisions of 40 CFR part 1065, subpart I, describe specifications for testing with 

oxygenated fuels; these specifications apply for NMOG determination as described in §1066.665. 

(c) The provisions of this subpart are intended to specify systems that can very accurately and 

precisely measure emissions from motor vehicles such as light-duty vehicles. To the extent that 

this level of accuracy and/or precision is not necessary for testing highway motorcycles or 

nonroad vehicles, we may waive or modify the specifications and requirements of this part for 

testing these other vehicles, consistent with good engineering judgment. For example, it may be 

appropriate to allow the use of a hydrokinetic dynamometer that is not able to meet all the 

performance specifications described in this subpart.

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analytical gases

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operating outside of a laboratory, except that 

provisions related to measuring

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§1066.105 Ambient controls and vehicle cooling fans.

(a) Ambient conditions. Dynamometer testing under this part generally requires that you 

maintain the test cell within a specified range of ambient temperature and humidity. Use good 

engineering judgment to maintain relatively uniform temperatures throughout the test cell before

testing. You are generally not required to maintain uniform temperatures throughout the test cell 

while the vehicle is running due to the heat generated by the vehicle. Measured humidity values 

must represent the conditions to which the vehicle is exposed, which includes intake air; other 

than the intake air, humidity does not affect emissions so humidity need not be uniform 

throughout the test cell.

(b) General requirements for cooling fans. Use good engineering judgment to select and 

configure fans to cool the test vehicle in a way that meets the specifications of paragraph (c) of 

this section and simulates in-use operation. If you demonstrate that the specified fan 

configuration is impractical for special vehicle designs, such as vehicles with rear-mounted 

engines, or it does not provide adequate cooling to properly represent in-use operation, you may 

ask us to approve increasing the fan’s capacity or using additional fans.

(c) Allowable cooling fans for vehicles at or below 14,000 pounds GVWR. Cooling fan 

specifications for vehicles at or below 14,000 pounds GVWR depend on the test cycle. 

Paragraph (c)(1) of this section summarizes the cooling fan specifications for the different test 

cycles; the detailed specifications are described in paragraphs (c)(2) through (5) of this section. 

See §1066.410 for instruction regarding how to use the fans during testing.

(1) Cooling fan specifications for different test cycles are summarized as follows:

(i) For the FTP test cycle, the allowable cooling fan configurations are described in paragraphs 

(c)(2) and (4) of this section.

(ii) For the US06 test cycle, the allowable cooling fan configurations are described in paragraphs 

(c)(2) and (5) of this section.

(iii) For the LA-92 test cycle, the allowable cooling fan configurations are described in 

paragraphs (c)(2), (4), and (5) of this section.

(iv) For SC03 and AC17 test cycles, the allowable cooling fan configuration is described in 

paragraph (c)(3) of this section.

(v) For the HFET test cycle, the allowable cooling fan configurations are described in paragraphs 

(c)(2) and (4) of this section.

(2) You may use a road-speed modulated fan system meeting the specifications of this paragraph 

(c)(2) for anything other than SC03 and AC17 testing. Use a road-speed modulated fan that 

achieves a linear speed of cooling air at the blower outlet that is within ±3.0 mph (±1.3 m/s) of 

the corresponding roll speed when vehicle speeds are between 5 and 30 mph (2.2 to 13.4 m/s), 

and within ±6.5 mph (±2.9 m/s) of the corresponding roll speed at higher vehicle speeds; 

however you may limit the fan’s maximum linear speed to 70 mph. We recommend that the 

cooling fan have a minimum opening of 0.2 m2 and a minimum width of 0.8 m.

(i) Verify the air flow velocity for fan speed corresponding to vehicle speeds of 20 and 40 mph 

using an instrument that has an accuracy of ±2 % of the measured air flow speed.

(ii) For fans with rectangular outlets, divide the fan outlet into the as shown in Figure 1 of this 

section. As denoted by the “+” in the figure, measure flow from the center of each section; 

however do not measure the flow from the center section.

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paragraph (c)(4) of this section is also allowable with 

advance approval.

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Figure 1 of §1066.105—Rectangular fan outlet grid.

(iii) For fans with circular outlets, divide the fan outlet into 8 equal sections as shown in Figure 2 

of this section . As denoted by the “+” in the figure, measure flow on the radial centerline of 

each section (at 22.5°) at a radius of two-thirds of the total radius.

Figure 2 of §1066.105—Circular fan outlet grid.

(iv) Verify that the fan air flow velocity vector perpendicular to the axial flow velocity vector is 

less than 15% of the mean velocity measured at fan speeds corresponding to vehicle speeds of 20 

and 40 mph.

(v) Verify that the uniformity of the fan axial flow tolerance is within ±4.0 mph at fan speeds 

corresponding to 20 mph and within ±8.0 mph at fan speeds corresponding to 40 mph. For 

example, at 20 mph, flow at all axial locations denoted by the “+” across the discharge nozzle 

must be between 16 and 24 mph. Measure the fan axial air flow velocity approximately 60 cm 

from the nozzle outlet at each point of the discharge area grid.

(3) For SC03 and AC17 testing, use a road-speed modulated fan with a minimum air flow nozzle 

discharge area that is equal to or exceeds the vehicle’s frontal inlet area. We recommend using a 

fan with a discharge area of 1.7 m2.

(i) Air flow volumes must be proportional to vehicle speed. When meeting the minimum 

discharge area requirements, the flow volume would vary from 0 m3/s at 0 mph to approximately 

45 m3/s at 60 mph. If this fan is also the only source of test cell air circulation or if fan 

operational mechanics make the 0 mph air flow requirement impractical, air flow of 2 mph or 

less at 0 mph vehicle speed is allowed.

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(ii) Verify that the fan air flow velocity vector perpendicular to the axial flow velocity vector is

less than 10 % of the mean velocity measured at fan speeds corresponding to vehicle speeds 

between 20 and 40 mph.

(iii) Verify that the uniformity of fan axial flow tolerance is 20 % of the fan speed corresponding 

to vehicle speeds of 20 and 40 mph. For example, at 20 mph, flow at all axial locations across 

the discharge nozzle must be between 16 and 24 mph. Measure the fan axial air flow velocity 

approximately 60 cm from the nozzle outlet at each point of a one foot grid over the entire

discharge area.

(iv) The instrument used to verify the air velocity must have an accuracy of ±2 % of the 

measured air flow speed.

(v) In addition to the road-speed modulated fan, we may approve the use of one or more fixedspeed fans to provide proper cooling to represent in-use operation, but only up to a total of 2.50 

m3/s for all additional fans.

(4) You may use a fixed-speed fan with a maximum capacity up to 2.50 m3/s for FTP, LA-92, 

and HFET testing. 

(5) You may use a fixed-speed fan with a maximum capacity up to 7.10 m3/s for US06 and LA92 testing.

(d) Allowable cooling fans for vehicles above 14,000 pounds GVWR. For all testing, use a roadspeed modulated fan system that achieves a linear speed of cooling air at the blower outlet that is 

within ±3.0 mph (±1.3 m/s) of the corresponding roll speed when vehicle speeds are between 5 

and 30 mph (2.2 to 13.4 m/s), and within ±10 mph (±4.5 m/s) of the corresponding roll speed at 

higher vehicle speeds. For vehicles above 19,500 pounds GVWR, we recommend that the 

cooling fan have a minimum opening of 2.75 m2, a minimum flow rate of 60 m3/s at 50 mph, and 

a minimum speed profile across the duct, in the free stream flow, that is ±15 % of the target flow 

rate.

§1066.110 Equipment specifications for emission sampling systems.

(a) This section specifies equipment related to emission testing, other than measurement 

instruments. This equipment includes two broad categories—dynamometers (described further 

in subpart C of this part) and emission-sampling hardware. Other related sections in this subpart 

identify measurement instruments (§1066.120), describe how to evaluate the performance of 

these instruments (§§1066.130 and 1066.137), describe how to calibrate a CVS (§1066.140),

specify engine fluids and analytical gases (§1066.145), and specify requirements for analyzer 

interference and quench verification (§1066.150). 

(b) The following equipment specifications apply for testing under this part:

(1) Tailpipe connections. Connect a vehicle’s exhaust system to any dilution stage as follows:

(i) Minimize laboratory exhaust tubing lengths. You may use a total length of laboratory tubing

up to 4 m, without needing to heat or insulate the tubing. However, you may use a total length of 

laboratory tubing up to 10 m if you insulate and/or heat the tubing to minimize the temperature 

difference between the exhaust gas and the tubing wall over the course of the emission test. The 

laboratory exhaust tubing starts at the end of the vehicle’s tailpipe. The laboratory exhaust 

tubing ends at the first sample point or the point of first dilution. You may use flexible 

laboratory exhaust tubing at any location in the laboratory exhaust system; although we 

recommend that you limit the amount of flexible tubing to the extent practicable. For multipleDeleted: grid

Deleted: ,
tailpipe configurations where the tailpipes combine into a single flow path for emission sampling, 

the start of the laboratory exhaust tubing may be taken at the last joint where the exhaust flow 

first becomes a single, combined flow.

(ii) You may insulate or heat any laboratory exhaust tubing. 

(iii) Use laboratory exhaust tubing materials that are smooth-walled and not chemically reactive 

with exhaust constituents. (For purposes of this paragraph (b)(1), nominally smooth spiral-style 

and accordion-style flexible tubing are considered to be smooth-walled.) For measurements 

involving PM, tubing materials must also be electrically conductive. Stainless steel is an 

acceptable material for any measurements. You may use short sections of nonconductive 

flexible tubing to connect a PM sampling system to the vehicle’s tailpipe; use good engineering 

judgment to limit the amount of nonconductive surface area exposed to the vehicle’s exhaust.

(iv) 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.

(v) You must seal your system to the extent necessary to ensure that any remaining leaks do not 

affect your ability to demonstrate compliance with the applicable standards. We recommend that 

you seal all known leaks.

(vi) Electrically ground the entire exhaust system, with the exception of nonconductive flexible 

tubing, as allowed under paragraph (b)(1)(iii) of this section.

(vii) For vehicles with multiple tailpipes, route the exhaust into a single flow. To ensure mixing 

of the multiple exhaust streams before emission sampling, we recommend a minimum Reynolds 

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

diameter of the combined flow at the first sampling point. You may configure the exhaust 

system with turbulence generators, such as orifice plates or fins, to achieve good mixing; this

may be required for Re# less than 4000. Re# is defined in 40 CFR 1065.640.

(2) Provisions from 40 CFR part 1065. Use equipment specifications in 40 CFR 1065.140 

through 40 CFR 1065.190, except as follows:

(i) For PM background measurement, the following provisions apply instead of the analogous 

provisions in 40 CFR 1065.140(b):

(A) You need not measure PM background for every test. You may apply PM background 

correction using a moving-average background value as long as your background PM sample 

media (e.g., filters) were all made by the same manufacturer from the same material . Use good 

engineering judgment to determine how many background samples make up the moving average

and how frequently to update those values. For example, you might take one background sample 

per week and average that sample into previous background values, maintaining five 

observations for each calculated average value. Background sampling time should be 

representative of the test interval duration to which the background correction is applied.

(B) You may sample background PM from the dilution tunnel at any time before or after an 

emission test using the same sample train used during the emission test. For this background 

sampling, the dilution tunnel blower must be turned on, the vehicle must be disconnected from 

the exhaust transfer tube, and the exhaust transfer tube must be capped. You may apply PM 

background correction using a moving-average background value obtained by averaging 

background samples across multiple sites, consistent with good engineering judgment.

Deleted: y

Deleted: We recommend a minimum Reynolds 

number, Re#, of 4000 for the combined exhaust 

stream, where Re# is based on the inside diameter of 

the combined flow at the first sampling point. 
(C) The duration of your background sample does not need to be the same as the test cycle in 

which you are applying the background correction, provided it is not inconsistent with the use of 

good engineering judgment.

(D) Your background correction may not exceed 5 μg or 5 % of the net PM mass expected at the 

standard, whichever allowance is greater.

(ii) The provisions of 40 CFR 1065.140(d)(2)(iv) do not apply.

(iii) For PM samples, configure dilution systems using the following limits:

(A) Control the dilution air temperature as described in 40 CFR 1065.140(e)(1), except that the 

temperature may set to (15 to 52) °C. Use good engineering judgment to control PM sample 

temperature as required under 40 CFR 1065.140(e)(4).

(B) Apply the provisions of this paragraph (b)(2)(iii)(B) instead of 40 CFR 1065.140(e)(2). Add 

dilution air to the raw exhaust such that the overall dilution factor of diluted exhaust to raw 

exhaust, as determined in Eq. 1066.620-2 or 1066.620-3, is within the range of (7:1 to 20:1). 

Compliance with this dilution factor range may be determined for an individual test interval or as 

a time-weighted average over the entire duty cycle as determined in Eq. 1066.620-4. The 

maximum dilution factor limit of 20:1 does not apply for plug-in hybrid electric vehicles 

(PHEVs) and hybrid electric vehicles (HEVs), since the dilution factor is infinite when the 

engine is off; however we strongly recommend that you stay under the maximum dilution factor 

limit when the engine is running. For partial-flow sampling systems, determine dilution factor 

using Eq. 1066.620-3. When determining dilution factor for PM samples utilizing secondary 

dilution air, multiply the dilution factor by the dilution ratio of secondary dilution air to primary 

diluted exhaust.

(iv) In addition to the allowances in 40 CFR 1065.140(c)(6) you may also heat the dilution air as 

described in paragraph (b)(2)(iii)(A) of this section to prevent or limit aqueous condensation.

(v) If you choose to dilute the exhaust by using a remote mix tee, which dilutes the exhaust at the 

tailpipe, you may use the following provisions consistent with good engineering judgment,

provided they do not affect your ability to demonstrate compliance with the standard:

(A) You may use accordion-style or smooth-walled flexible tubing in the dilution tunnel 

upstream of flow or gaseous emission measurement locations.

(B) You may use smooth-walled electrically conductive flexible tubing in the dilution tunnel 

upstream of where PM emission measurements are made.

(C) Materials for inside surfaces are limited to 300 series stainless steel and polymer-based 

materials.

(D) Use good engineering judgment to ensure that the materials you choose do not cause or 

contribute to significant loss of PM from your sample.

(vi) Paragraph (b)(1)(vi) of this section applies instead of 40 CFR 1065.145(b).

(c) The following table summarizes the requirements of paragraph (b)(2) of this section:
Table 1 of §1066.110–Summary of equipment specifications from 40 CFR part 1065, subpart B,

that apply for chassis testing

40 CFR part 1065 

references Applicability for chassis testing under this part

40 CFR 1065.140

Use all except:

40 CFR 1065.140(b) applies as described in this 

section.

Use 40 CFR 1065.140(c)(6), with the additional 

allowance described in this section.

Do not use 40 CFR 1065.140(d)(2)(iv). 

Use 40 CFR 1065.140(e)(1) as described in this 

section. 

Do not use 40 CFR 1065.140(e)(2).

40 CFR 1065.145 Use all except 40 CFR 1065.145(b).

40 CFR 1065.150 

through 1065.190 Use all.

§1066.120 Measurement instruments.

The measurement instrument requirements in 40 CFR part 1065, subpart C, apply with the 

following exceptions:

(a) The provisions of §1066.122 apply instead of 40 CFR 1065.202.

(b) The provisions of 40 CFR 1065.210 and 1065.295 do not apply.
§1066.122 Data updating, recording, and control for measurement instruments.

This section specifies criteria that your test system must meet for updating and recording data. It 

also specifies criteria for controlling the systems related to driver demand, the dynamometer, 

sampling equipment, and measurement instruments.

(a)(1) This paragraph (a)(1) applies where we specify a minimum command and control 

frequency that is greater than the minimum recording frequency, such as for sample flow rates 

from a CVS that does not have a heat exchanger. For these measurements, the rate at which you 

read and interpret the signal must be at least as frequent as the minimum command and control 

frequency. You may record values at the same frequency, or you may record them as mean

values, as long as the frequency of the mean values meets the minimum recording frequency. 

You must use all read values, either by recording them or using them to calculate mean values. 

For example, if your system reads and controls the sample flow rate at 10 Hz, you may record 

these values at 10 Hz, record them at 5 Hz by averaging pairs of consecutive points together, or 

record them at 1 Hz by averaging five consecutive points together. 

(2) For all other measured values covered by this section, you may record the values 

instantaneously or as mean values, consistent with good engineering judgment. 

(3) You may not use rolling averages of measured values where a given measured value is 

included in more than one recorded mean value. 

(b) Use data acquisition and control systems that can command, control, and record at the 

following minimum frequencies:

Table 1 of §1066.122–Data recording and control minimum frequencies

Applicable 

Section Measured Values

Minimum 

Command and 

Control 

Frequencya

Minimum 

Recording 

Frequencyb,c,d

§1066.310

§1066.320 Vehicle speed — 10 Hz

§1066.430 Continuous concentrations of raw or dilute 

analyzers — 1 Hz

§1066.430

§1066.501 Power analyzerc — 1 Hz

§1066.430 Bag concentrations of raw or dilute analyzers — 1 mean value 

per test interval

40 CFR 1065.545

§1066.430

Diluted exhaust flow rate from a CVS with a 

heat exchanger upstream of the flow 

measurement

N/A 1 Hz

40 CFR 1065.545

§1066.430

Diluted exhaust flow rate from a CVS without 

a heat exchanger upstream of the flow 

measurement

5 Hz 1 Hz means

40 CFR 1065.545

§1066.430

Dilution air flow if actively controlled (for 

example, a partial-flow PM sampling system)e 5 Hz 1 Hz means

40 CFR 1065.545

§1066.430

Sample flow from a CVS that has a heat 

exchanger 1 Hz 1 Hz

40 CFR 1065.545

§1066.430

Sample flow from a CVS that does not have a 

heat exchanger 5 Hz 1 Hz means

§1066.425 Ambient temperature — 1 Hzf

§1066.425 Ambient humidity — 1 Hzf

Deleted: V

Deleted: may be recorded 

Deleted: . They may also be recorded 

Deleted: s of the

Deleted: provided 

Deleted: A

Deleted: read must be 

Deleted: recorded or used to 

Deleted: the 

Deleted: a

Deleted: b

Deleted: —

Deleted: N/A
§1066.425 Heated sample system temperatures, including 

PM filter face — 1 Hz

a

CFVs that are not using active control are exempt from meeting this requirement due to their operating 

principle.

b

1 Hz means are data reported from the instrument at a higher frequency, but recorded as a series of 1 s 

mean values at a rate of 1 Hz.

c

For CFVs in a CVS, the minimum recording frequency is 1 Hz. For CFVs used to control sampling from a 

CFV CVS, the minimum recording frequency is N/A.

d

For power analyzers’ sampling frequency, follow SAE J1711 (incorporated by reference in §1066.1010).

e

This is not applicable to CVS dilution air.

f

Unless specified elsewhere in this part or the standard setting part. Note that this provision does not apply 

to soak periods where recording frequencies are not specified. For these instances, we recommend a 

recording frequency of ≤ 0.016 Hz.

Deleted: b
§1066.130 Measurement instrument calibrations and verifications.

The measurement instrument calibration and verification requirements in 40 CFR part 1065,

subpart D, apply with the following exceptions:

(a) The calibration and verification provisions of 40 CFR 1065.303 do not apply for engine speed, 

torque, fuel rate, or intake air flow.

(b) The linearity verification provisions of 40 CFR 1065.307 do not apply for engine speed, 

torque, fuel rate, or intake air flow. Section 1066.137 specifies additional linearity verification 

provisions that apply specifically for chassis testing.

(c) The provisions of §1066.220 apply instead 40 CFR 1065.310.

(d) The provisions of 40 CFR 1065.320, 1065.325, and 1065.395 do not apply.

(e) If you are measuring flow volumetrically (rather than by molar), the provisions of §1066.140 

apply instead of 40 CFR 1065.340.

(f) The provisions of §1066.150 apply instead 40 CFR 1065.350(c), 1065.355(c), 1065.370(c),

and 1065.375(c).

(g) Table 1 of this section summarizes the required and recommended calibrations and 

verifications that are unique to testing under this part and indicates when these have to be 

performed. Perform other required or recommended calibration and verifications as described in 

40 CFR 1065.303, with the exceptions noted in this section. Table 1 follows:

Table 1 of §1066.130–Summary of required calibration and verifications.

Type of calibration or 

verification Minimum frequencya

40 CFR 1065.307: Linearity 

verification

The linearity calibrations from 40 CFR part 1065 do not apply under this part for engine 

speed, torque, fuel rate, or intake air flow; the linearity verification described in §1066.137 

applies for the following measurements:

Dynamometer Speed: See §1066.220.

Dynamometer Torque: See §1066.220.

40 CFR 1065.310: Torque This calibration does not apply for testing under this part; see §1066.220.

40 CFR 1065.320: Fuel flow This calibration does not apply for testing under this part.

40 CFR 1065.325: Intake flow This calibration does not apply for testing under this part.

40 CFR 1065.340: CVS 

calibration

This calibration does not apply for CVS flow meters calibrated volumetrically as described in

§1066.140.

40 CFR 1065.345: Vacuum leak Required upon initial installation of the sampling system; recommended within 35 days

before the start of an emissions test and after maintenance such as pre-filter changes.

40 CFR 1065.350(c), 

1065.355(c), 1065.370(c), and 

1065.375(c)

These provisions do not apply for testing under this part; see §1066.150.

40 CFR 1065.395: Inertial PM 

balance and weighing These verifications do not apply for testing under this part.

a

Perform calibrations and verifications more frequently if needed to conform to the measurement system manufacturer’s

instructions and good engineering judgment.

§1066.137 Linearity verification.

This section describes requirements for linearity verification that are unique to testing under this 

part. (Note: see the definition of “linearity” in 40 CFR 1065.1001, where we explain that 

linearity means the degree to which measured values agree with respective reference values and 

that the term “linearity” is not used to refer to the shape of a measurement instrument's 

unprocessed response curve.) Perform other required or recommended calibration and 

verifications as described in 40 CFR 1065.307, with the exceptions noted in this section. 

Deleted: Section 1066.133 specifies additional 

calibration and verification provisions that apply 

specifically for chassis testing.
(a) For testing under this subpart, linearity verification under 40 CFR part 1065 is not required 

for speed, torque, fuel flow rate, or intake air flow.

(b) For gas analyzer linearity, use one of the following options:

(1) Use instrument manufacturer recommendations and good engineering judgment to select at 

least ten reference values, yrefi, that cover the range of values that you expect during testing (to 

prevent extrapolation beyond the verified range during emission testing). We recommend 

selecting zero as one of your reference values. For each range calibrated, if the deviation from a 

least-squares best-fit straight line is 2 % or less of the value at each data point, concentration 

values may be calculated by use of a straight line curve fit for that range. If the deviation 

exceeds 2 % at any point, use the best-fit nonlinear equation that represents the data to within 

2 % of each test point to determine concentration. If you use a gas divider to blend calibration 

gases, verify that the calibration curve produced names a calibration gas within 2 % of its 

certified concentration. Perform this verification between 15 and 50 % of the full scale analyzer 

range.

(2) Use the linearity requirements of 40 CFR 1065.307, except for CO2 measurements used for 

determining fuel economy and GHG emissions for motor vehicles at or below 14,000 pounds

GVWR. If you choose this linearity option (b)(2), noting that this option cannot be used for CO2

measurements, you must drift check and drift correct your emission data according to 40 CFR 

1065.672.

(c) For dilution air, diluted exhaust, and raw exhaust 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 full-flow 

dilution system, we recommend a reference subsonic venturi flow meter with a restrictor valve 

and a blower to simulate flow rates. For dilution air, diluted exhaust for partial-flow dilution, 

and raw exhaust, 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 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 Qrefi

 for 30 seconds and use the arithmetic mean of the values, Qref

 , as the 

reference value. Refer to §1065.602 for an example of calculating arithmetic mean.

(iii) Linearity criteria. The values measured during flow meter linearity verification must meet 

the following criteria: | xmin(a1-1)+a0 | ≤ 1 % · Qmax

 , a1 = 0.98-1.02, SEE = ≤ 2 % · Qmax , and r

2

≥ 0.990.

(d) Perform linearity verifications for the following temperature measurements instead of those 

specified at 40 CFR 1065.307(e)(7):

(1) Test cell ambient air.

(2) Dilution air for PM sampling, including CVS, double-dilution, and partial-flow systems.

(3) PM sample.

Deleted: single calibration factor

Field Code Changed

Field Code Changed

Field Code Changed

Field Code Changed

Deleted: c
(4) Chiller sample, for gaseous sampling systems that use thermal chillers to dry samples and 

that use chiller temperature to calculate dewpoint at the chiller outlet. For testing, if you choose 

to use the 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 verify the 

accuracy of the high alarm temperature setpoint using good engineering judgment without 

following the linearity verification for chiller temperature. We recommend that you input a 

simulated reference temperature signal below the alarm setpoint, increase this signal until the 

high alarm trips, and verify that the alarm setpoint value is no less than 2 °C below the reference 

value at the trip point.

(5) CVS flow meter inlet temperature.

(e) Perform linearity verifications for the following pressure measurements instead of those 

specified at 40 CFR 1065.307(e)(8):

(1) Exhaust back pressure at the tailpipe.

(2) Barometric pressure.

(3) CVS flow meter inlet gage pressure or absolute pressure transducer.

(4) 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 verify the accuracy of the low alarm pressure setpoint using good 

engineering judgment without following the linearity verification for sample dryer pressure. We 

recommend that you input a reference pressure signal above the alarm setpoint, decrease this 

signal until the low alarm trips, and verify that the alarm setpoint value is no more than 4 kPa 

above the reference value at the trip point. 

(f) When following procedures or practices that we incorporate by reference in §1066.1010, you 

must meet the linearity requirements given by the procedure or practice for any analytical 

instruments not covered under 40 CFR 1065.307, such as GC-FID or HPLC.

§1066.140 Diluted exhaust flow calibration.

(a) Overview. This section describes how to calibrate flow meters for diluted exhaust constantvolume sampling (CVS) systems. We recommend that you also use this section to calibrate flow 

meters that use a subsonic venturi or ultrasonic flow to measure raw exhaust flow. You may 

follow the molar flow calibration procedures in 40 CFR 1065.340 instead of the procedures in 

this section.

(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 40 CFR 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 the flow meter meets the requirements in 40 CFR 1065.340(c).

(d) Reference flow meter. Calibrate each 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, or an ultrasonic flow meter. Use a reference flow meter that reports 

Deleted: d

Deleted: e

Deleted: a set of critical flow venturis, 
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. Calibrate the system with any upstream screens or other restrictions that will 

be used during testing and that could affect the flow ahead of the reference flow meter. You 

may not use any 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 each positive-displacement pump (PDP) to determine a flowversus-PDP 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, Qref

 . This may include several 

measurements of different quantities, such as reference meter pressures and temperatures, for 

calculating Qref

 .

(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 (f)(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 §1066.650(a).

(10) Repeat the steps in paragraphs (f)(6) through (9) of this section for each speed at which you 

operate the PDP.

(11) Use the equations in §1066.652(a) 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 

40 CFR 1065.341.

(13) Ensure that the lowest inlet pressure tested during calibration is at least as low as the lowest 

PDP inlet pressure that will occur during emission testing. You may not use the PDP below the 

lowest inlet pressure tested during calibration.

Deleted: e

Deleted: e
(g) SSV calibration. Calibrate each subsonic venturi (SSV) to determine its discharge coefficient,

Cd, for the expected range of inlet pressures. Calibrate an SSV flow meter as follows:

(1) Configure your calibration 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, Qref

 . This may include several 

measurements of different quantities for calculating Qref

 , such as reference meter pressures and 

temperatures.

(ii) The mean temperature at the venturi inlet, Tin .

(iii) The mean static absolute pressure at the venturi inlet, in p .

(iv) Mean 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 an equation to quantify Cd as a function of Re# by using the collected data and the 

equations in §1066.650(b). Section 1066.650 also includes statistical criteria for validating the 

Cd versus Re# equation.

(10) Verify the calibration by performing a CVS verification (i.e., propane check) as described in 

40 CFR 1065.341 using the new Cd versus Re# equation.

(11) Use the SSV only between the minimum and maximum calibrated flow rates. If you want 

to use the SSV at a higher or lower flow rate, you must recalibrate the SSV.

(12) Use the equations in §1066.652(b) to determine SSV flow during a test.

(h) CFV calibration. The calibration procedure described in this paragraph (h) establishes the 

value of the calibration coefficient at measured values of pressure, temperature and air flow.

Calibrate a critical-flow venturi (CFV) to verify its calibration coefficient, Kv, at the lowest 

expected static differential pressure between the CFV inlet and outlet. Calibrate a CFV flow 

meter as follows:

(1) Configure your calibration 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, Qref

 . This may include several 

measurements of different quantities, such as reference meter pressures and temperatures, for 

calculating Qref

 .

(ii) The mean temperature at the venturi inlet, Tin .

(iii) The mean static absolute pressure at the venturi inlet, in p .

(iv) 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 (h)(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 restriction.

(9) Determine Kv and the lowest allowable pressure ratio, r, according to §1066.650.

(10) Use Kv to determine CFV flow during an emission test. Do not use the CFV below the 

lowest allowed r, as determined in §1066.650.

(11) Verify the calibration by performing a CVS verification (i.e., propane check) as described in 

40 CFR 1065.341.

(12) If your CVS is configured to operate multiple CFVs in parallel, calibrate your CVS using

one of the following methods:

(i) Calibrate every combination of CFVs according to this section and §1066.650(c). Refer to 

§1065.652(c) for instructions on calculating flow rates for this option.

(ii) Calibrate each CFV according to this section and §1066.650. Refer to §1066.652 for 

instructions on calculating flow rates for this option.

(i) Ultrasonic flow meter calibration. [Reserved]

Figure 1 of 1066.140—CVS calibration configurations.

Deleted: f
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
§1066.145 Test fuel, engine fluids, analytical gases, and other calibration standards.

(a) Test fuel. Use test fuel as specified in the standard-setting part, or as specified in 40 CFR 

part 1065, subpart H, if it is not specified in the standard-setting part.

(b) Lubricating oil. Use lubricating oil as specified in 40 CFR 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.

(c) Coolant. For liquid-cooled engines, use coolant as specified in 40 CFR 1065.745.

(d) Analytical gases. Use analytical gases that meet the requirements of 40 CFR 1065.750.

(e) Mass standards. Use mass standards that meet the requirements of 40 CFR 1065.790.

§1066.150 Analyzer interference and quench verification limit.

Analyzers must meet the interference and quench verification limits in the following table on the 

lowest, or most representative, instrument range that will be used during emission testing, instead 

of those specified in 40 CFR part 1065, subpart D:

Table 1 of §1066.150–Analyzer interference and quench verification limits.

Verification Limit

40 CFR 1065.350 ±2 % of full scale

40 CFR 1065.355 ±2 % of full scale

40 CFR 1065.370 ±2 % of full scale

40 CFR 1065.375 ±2 % of the flow-weighted mean concentration of 

N2O expected at the standard
Subpart C—Dynamometer Specifications 

§1066.201 Dynamometer overview.

This subpart addresses chassis dynamometers and related equipment. 

§1066.210 Dynamometers.

(a) General requirements. A chassis dynamometer typically uses electrically generated load 

forces combined with its rotational inertia to recreate the mechanical inertia and frictional forces 

that a vehicle exerts on road surfaces (known as “road load”). Load forces are calculated using 

vehicle-specific coefficients and response characteristics. The load forces are applied to the 

vehicle tires by rolls connected to motor/absorbers. The dynamometer uses a load cell to 

measure the forces the dynamometer rolls apply to the vehicle’s tires. 

(b) Accuracy and precision. The dynamometer’s output values for road load must be NISTtraceable. We may determine traceability to a specific international standards organization to be 

sufficient to demonstrate NIST-traceability. The force-measurement system must be capable of 

indicating force readings as follows:

(1) For dynamometer testing of vehicles at or below 20,000 pounds GVWR, the dynamometer 

force-measurement system must be capable of indicating force readings during a test to a 

resolution of ±0.05 % of the maximum load-cell force simulated by the dynamometer or ±9.8 N 

(±2.2 lbf), whichever is greater.

(2) For dynamometers testing of vehicles above 20,000 pounds GVWR the force-measurement 

system must be capable of indicating force readings during a test to a resolution of ±0.05 % of 

the maximum load-cell force simulated by the dynamometer or ±39.2 N (±8.8 lbf), whichever is 

greater.

(c) Test cycles. The dynamometer must be capable of fully simulating vehicle performance over

applicable test cycles for the vehicles being tested as referenced in the corresponding standardsetting part, including operation at the combination of inertial and road-load forces 

corresponding to maximum road load conditions and maximum simulated inertia at the highest 

acceleration rate experienced during testing.

(d) Component requirements. The following specifications apply: 

(1) The nominal roll diameter must be 120 cm or greater. The dynamometer must have an 

independent drive roll for each drive axle as tested under §1066.410(g), except that two drive 

axles may share a single drive roll. Use good engineering judgment to ensure that the 

dynamometer roll diameter is large enough to provide sufficient tire-roll contact area to avoid 

tire overheating and power losses from tire-roll slippage. 

(2) Measure and record force and speed at 10 Hz or faster. You may convert measured values to 

1-Hz, 2-Hz, or 5-Hz values before your calculations, using good engineering judgment.

(3) The load applied by the dynamometer simulates forces acting on the vehicle during normal 

driving according to the following equation: 

2 i i-1

i ii

i i-1

v v FR A B v C v M

t t

    

 Eq. 1066.210-1 

Where: 

Deleted: intermediate 

Deleted: readingsto a resolution of ±0.05 % of the 

maximum forces simulated by the dynamometer or 

±0.9 N (±0.2 lbf), whichever is greater, during a test.

Deleted: (1) For vehicles with a gross vehicle 

weight rating (GVWR) at or below 14,000 lbs, the 

dynamometer must be able to fully simulate a 

driving schedule with a maximum speed of 36 m/s 

(80 mph) and a maximum acceleration rate of 3.6 

m/s2

 (8 mph/s) in two-wheel drive and four-wheel 

drive configurations.¶

(2) For vehicles with GVWR above 14,000 lbs, the 

dynamometer must be able to fully simulate a 

driving schedule with a maximum speed of 29 m/s 

(65 mph) and a maximum acceleration rate of 1.3 

m/s2

 (3 mph/s) in either two-wheel drive or fourwheel drive configurations.¶

Deleted: dynamometer must meet the 

Deleted: he

Deleted: 1.20 to 1.25 meters.

Deleted: ,

Deleted: .() ou measure force and speed at 10 Hz 

or faster you may use good engineering judgment to 

convert to 1-Hz, 2-Hz, or 5-Hz values

Deleted: ()
FR = total road-load force to be applied at the surface of the roll. The total force is the sum of 

the individual tractive forces applied at each roll surface. 

i = a counter to indicate a point in time over the driving schedule. For a dynamometer operating 

at 10-Hz intervals over a 600-second driving schedule, the maximum value of i should be 6,000. 

A = a vehicle-specific constant value representing the vehicle’s frictional load in lbf or newtons. 

See subpart D of this part. 

B = a vehicle-specific coefficient representing load from drag and rolling resistance, which are a 

function of vehicle speed, in lbf/mph or N·s/m. See subpart D of this part. 

v = linear speed at the roll surfaces as measured by the dynamometer, in mph or m/s. Let vi-1 = 0

for i = 0. 

C = a vehicle-specific coefficient representing aerodynamic effects, which are a function of 

vehicle speed squared, in lbf/mph2 or N·s2/m2. See subpart D of this part. 

M = mass of the vehicle in lbm or kg. For vehicles at or below 14,000 pounds GVWR, 

determine the vehicle’s mass based on equivalent test weight (ETW) as specified in §1066.810

and set dynamometer inertia simulation as specified in §1066.410(h). For vehicles above 14,000 

pounds GVWR, determine the vehicle’s mass based on the test weight, taking into account the 

effect of rotating axles, as specified in §1066.310(b)(7) and dividing the weight by the 

acceleration due to gravity as specified in 40 CFR 1065.630, consistent with good engineering 

judgment. 

t = elapsed time in the driving schedule as measured by the dynamometer, in seconds. Let ti-1 = 0

for i = 0. 

(4) We recommend that a dynamometer capable of testing vehicles at or below 20,000 pounds 

GVWR be designed to apply an actual road-load force within ±1 % or ±9.8 N (±2.2 lbf) of the 

reference value, whichever is greater. Dynamometers that do not fully meet this specification 

may be used consistent with good engineering judgment. For example, slightly higher errors 

may be permissible during highly transient operation for vehicles above 8,500 pounds GVWR. 

(e) Dynamometer manufacturer instructions. This part specifies that you follow the dynamometer 

manufacturer’s recommended procedures for things such as calibrations and general operation. 

If you perform testing with a dynamometer that you manufactured or if you otherwise do not 

have these recommended procedures, use good engineering judgment to establish the additional 

procedures and specifications we specify in this part, unless we specify otherwise. Keep records 

to describe these recommended procedures and how they are consistent with good engineering 

judgment, including any quantified error estimates.

§1066.215 Summary of verification and calibration procedures for chassis dynamometers. 

(a) Overview. This section describes the overall process for verifying and calibrating the 

performance of chassis dynamometers.

(b) Scope and frequency. The following table summarizes the required and recommended 

calibrations and verifications described in this subpart and indicates when they must occur: 

Table 1 of §1066.215–Summary of required dynamometer calibrations and verifications. 

Type of calibration or verification Minimum frequencya

§1066.220: Linearity verification 

Speed: Upon initial installation, within 370 days before testing, and after 

major maintenance. 

Torque (load): Upon initial installation and after major maintenance. 

§1066.225: Roll runout and diameter

verification Upon initial installation and after major maintenance. 

§1066.230: Time verification Upon initial installation and after major maintenance. 

Deleted: is

Deleted: C

Deleted: C

Deleted: S

Deleted: Si

Deleted: C

Deleted: M = mass of vehicle in lbm or kg. 

Determine

Deleted: () The

Deleted: must

Deleted: generally

Deleted: , within 370 days before testing,
§1066.235: Speed measurement

verification

Upon initial installation, within 370 days before testing, and after major 

maintenance. 

§1066.240: Torque (load) transducer

verification Upon initial installation, within 7 days of testing, and after major maintenance. 

§1066.245: Response time

verification

Upon initial installation, within 370 days before testing, and after major 

maintenance. 

§1066.250: Base inertia verification Upon initial installation and after major maintenance. 

§1066.255: Parasitic loss verification Upon initial installation, after major maintenance, and upon failure of a

verification in §1066.270 or §1066.280. 

§1066.260: Parasitic friction 

compensation evaluation 

Upon initial installation, after major maintenance, and upon failure of a

verification in §1066.270 or §1066.280. 

§1066.265: Acceleration and 

deceleration verification Upon initial installation and after major maintenance. 

§1066.270: Unloaded coastdown

verification Upon initial installation, within 7 days of testing, and after major maintenance. 

§1066.280 Dynamometer readiness 

verification

Upon initial installation, within 1 day before testing, and after major 

maintenance. a

Perform calibrations and verifications more frequently, according to measurement system manufacturer instructions 

and good engineering judgment. 

(c) Automated dynamometer verifications and calibrations. In some cases, dynamometers are 

designed with internal diagnostic and control features to accomplish the verifications and 

calibrations specified in this subpart. You may use these automated functions instead of 

following the procedures we specify in this subpart to demonstrate compliance with applicable 

requirements, consistent with good engineering judgment. 

(d) Sequence of verifications and calibrations. Upon initial installation and after major 

maintenance, perform the verifications and calibrations in the same sequence as noted in Table 1 

of this section, except that you may perform speed linearity verification after the verifications in 

§§1066.225 and 1066.230. At other times, you may need to perform specific verifications or 

calibrations in a certain sequence, as noted in this subpart. If you perform major maintenance on 

a specific component, you are required to perform verifications and calibrations only on 

components or parameters that are affected by the maintenance. 

(e) Corrections. Unless the regulation directs otherwise, if the dynamometer fails to meet any 

specified calibration or verification, make any necessary adjustments or repairs such that the 

dynamometer meets the specification before running a test. Repairs required to meet 

specifications are generally considered major maintenance under this part. 

§1066.220 Linearity verification for chassis dynamometer systems. 

(a) Scope and frequency. Perform linearity verification for dynamometer speed and torque at 

least as frequently as indicated in Table 1 of §1066.215. The intent of linearity verification is to 

determine that the 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 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. 

Deleted: within 7 days before testing, and 

Deleted: within 7 days before testing, and 

Deleted: before

Deleted: .

Deleted: calibration

Deleted: .

Deleted: a measurement
(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) Operate the dynamometer system at the specified operating conditions. This may include any 

specified adjustment or periodic calibration of the dynamometer system. 

(3) Set dynamometer speed and torque to zero. 

(4) Verify the dynamometer speed or torque signal based on the dynamometer manufacturer’s 

recommendations. 

(5) After verification, check for zero speed and torque. Use good engineering judgment to 

determine whether or not to rezero or re-verify speed and torque before continuing. 

(6) For both speed and torque, use the dynamometer manufacturer’s recommendations and good 

engineering judgment to select reference values, yrefi, that cover a range of values that you expect 

would prevent extrapolation beyond these values during emission testing. We recommend 

selecting zero speed and zero torque as reference values for the linearity verification. 

(7) Use the dynamometer 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 the influence of 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) Set the dynamometer to operate at a reference condition. 

(9) Allow time for the dynamometer to stabilize while it measures the reference values. 

(10) At a recording frequency of at least 1 Hz, measure speed and torque values for 30 seconds 

and record the arithmetic mean of the recorded values, i y . Refer to 40 CFR 1065.602 for an 

example of calculating an arithmetic mean. 

(11) Repeat the steps in paragraphs (c)(8) though (10) of this section until you measure speeds 

and torques at each of the reference settings. 

(12) 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 40 CFR 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. Table 1 follows:

Table 1 of §1066.220–

Dynamometer measurement systems that require linearity verifications

Measurement 

system Quantity Linearity criteria 

| ymin(a1-1)+a0 | a1 SEE r

2

Speed v <0.05 % · max v 0.98-1.02 <2 % · max v >0.990 

Torque (load) T <1 % · Tmax 0.99-1.01 <1 % · Tmax >0.990 

(d) Reference signals. Generate reference values for the linearity-verification protocol in 

paragraph (c) of this section as described for speed and torque in 40 CFR 1065.307(d). 

Deleted: a

Deleted: temperatures and pressures

Deleted: and apply the dynamometer brake to 

ensure a zero-speed condition

Deleted: Span

Deleted: .

Deleted: spanning

Deleted: span

Deleted: or

Deleted: conditions

Deleted: xmin

Deleted: S

Deleted: 98

Deleted: 02

Deleted: 2
§1066.225 Roll runout and diameter verification procedure. 

(a) Overview. This section describes the verification procedure for roll runout and roll diameter. 

Roll runout is a measure of the variation in roll radius around the circumference of the roll. 

(b) Scope and frequency. Perform these verifications upon initial installation and after major 

maintenance that could affect roll surface finish or dimensions (such as resurfacing or polishing).

(c) Roll runout procedure. Verify roll runout based on the following procedure, or an equivalent 

procedure based on good engineering judgment: 

(1) Perform this verification with laboratory and dynamometer temperatures stable and at 

equilibrium. Release the roll brake and shut off power to the dynamometer. Remove any dirt, 

rubber, rust, and debris from the roll surface. Mark measurement locations on the roll surface 

using a nominally permanent marker. Mark the roll at a minimum of four equally spaced 

locations across the roll width; we recommend taking measurements every 150 mm across the 

roll. Secure the marker to the deck plate adjacent to the roll surface and slowly rotate the roll to 

mark a clear line around the roll circumference. Repeat this process for all measurement 

locations. 

(2) Measure roll runout using an indicator with a probe that allows for measuring the position of 

the roll surface relative to the roll centerline as it turns through a complete revolution. The 

indicator must have some means of being securely mounted adjacent to the roll. The indicator 

must have sufficient range to measure roll runout at all points, with a minimum accuracy of 

±0.025 mm. Calibrate the indicator according to the instrument manufacturer’s instructions. 

(3) Position the indicator adjacent to the roll surface at the desired measurement location. 

Position the shaft of the indicator perpendicular to the roll such that the point of the indicator is 

slightly touching the surface of the roll and can move freely through a full rotation of the roll. 

Zero the indicator according to the instrument manufacturer’s instructions. Avoid distortion of 

the runout measurement from the weight of a person standing on or near the mounted dial 

indicator. 

(4) Slowly turn the roll through a complete rotation and record the maximum and minimum 

values from the indicator. Calculate runout as the difference between these maximum and 

minimum values. 

(5) Repeat the steps in paragraphs (c)(3) and (4) of this section for all measurement locations. 

(6) The roll runout must be less than 0.254 mm (0.0100 inches) at all measurement locations. 

(d) Diameter procedure. Verify roll diameter based on the following procedure, or an equivalent 

procedure based on good engineering judgment: 

(1) Prepare the laboratory and the dynamometer as specified in paragraph (c)(1) of this section. 

(2) Measure roll diameter using a Pi Tape®. Orient the Pi Tape® to the marker line at the desired 

measurement location with the Pi Tape® hook pointed outward. Temporarily secure the Pi 

Tape® to the roll near the hook end with adhesive tape. Slowly turn the roll, wrapping the Pi 

Tape® around the roll surface. Ensure that the Pi Tape® is flat and adjacent to the marker line 

around the full circumference of the roll. Attach a 2.26-kg weight to the hook of the Pi Tape®

and position the roll so that the weight dangles freely. Remove the adhesive tape without 

disturbing the orientation or alignment of the Pi Tape®. 

(3) Overlap the gage member and the vernier scale ends of the Pi Tape® to read the diameter 

measurement to the nearest 0.01 mm. Follow the manufacturer’s recommendation to correct the 

measurement to 20 °C, if applicable. 

(4) Repeat the steps in paragraphs (d)(2) and (3) of this section for all measurement locations. 

Deleted: .

Deleted: a dial

Deleted: dial 

Deleted: a magnetic base assembly or other

Deleted: dial 

Deleted: and precision 

Deleted: dial

Deleted: dial

Deleted: dial 

Deleted: dial

Deleted: dial

Deleted: dial 

Deleted: 25
(5) The measured roll diameter must be within ±0.254 mm of the specified nominal value at all 

measurement locations. You may revise the nominal value to meet this specification, as long as 

you use the corrected nominal value for all calculations in this subpart. 

§1066.230 Time verification procedure. 

(a) Overview. This section describes how to verify the accuracy of the dynamometer’s timing 

device. 

(b) Scope and frequency. Perform this verification upon initial installation and after major 

maintenance. 

(c) Procedure. Perform this verification using one of the following procedures: 

(1) WWV method. You may use the time and frequency signal broadcast by NIST from radio 

station WWV as the time standard if the trigger for the dynamometer timing circuit has a 

frequency decoder circuit, as follows: 

(i) Contact station WWV by telephone by dialing (303) 499-7111 and listen for the time 

announcement. Verify that the trigger started the dynamometer timer. Use good engineering 

judgment to minimize error in receiving the time and frequency signal. 

(ii) After at least 1000 seconds, re-dial station WWV and listen for the time announcement. 

Verify that the trigger stopped the dynamometer timer. 

(iii) Compare the measured elapsed time, yact, to the corresponding time standard, yref, to 

determine the time error, yerror, using the following equation: 

act ref

error

ref

100 % y y y

y

  

Eq. 1066.230-1 

(2) Ramping method. You may use an operator-defined ramp function to serve as the time 

standard as follows: 

(i) Set up a signal generator to output a marker voltage at the peak of each ramp to trigger the 

dynamometer timing circuit. Output the designated marker voltage to start the verification 

period. 

(ii) After at least 1000 seconds, output the designated marker voltage to end the verification 

period. 

(iii) Compare the measured elapsed time between marker signals, yact, to the corresponding time 

standard, yref, to determine the time error, yerror, using Eq. 1066.230-1. 

(3) Dynamometer coastdown method. You may use a signal generator to output a known speed 

ramp signal to the dynamometer controller to serve as the time standard as follows: 

(i) Generate upper and lower speed values to trigger the start and stop functions of the coastdown 

timer circuit. Use the signal generator to start the verification period. 

(ii) After at least 1000 seconds, use the signal generator to end the verification period. 

(iii) Compare the measured elapsed time between trigger signals, yact, to the corresponding time 

standard, yref, to determine the time error, yerror, using Eq. 1066.230-1. 

(d) Performance evaluation. The time error determined in paragraph (c) of this section may not 

exceed ±0.001 %. 

§1066.235 Speed verification procedure. 

(a) Overview. This section describes how to verify the accuracy of the dynamometer speed 

determination. When performing this verification, you must also verify the dynamometer speed 

Deleted: 25

Deleted: Dial

Deleted: at

Deleted: set up

Deleted: in the signal generator

Deleted: the

Deleted: Equation

Deleted: Equation

Deleted: and resolution of
at any devices used to display or record vehicle speed (for example a driver’s aid) is 

representative of the speed input from the dynamometer speed determination. 

(b) Scope and frequency. Perform this verification upon initial installation, within 370 days 

before testing, and after major maintenance. 

(c) Procedure. Use one of the following procedures to verify the accuracy and resolution of the 

dynamometer speed simulation: 

(1) Pulse method. Connect a universal frequency counter to the output of the dynamometer’s 

speed-sensing device in parallel with the signal to the dynamometer controller. The universal 

frequency counter must be calibrated according to the counter manufacturer’s instructions and be 

capable of measuring with enough accuracy to perform the procedure as specified in this 

paragraph (c)(1). Make sure the instrumentation does not affect the signal to the dynamometer 

control circuits. Determine the speed error as follows: 

(i) Set the dynamometer to speed-control mode. Set the dynamometer speed to a value of 

approximately 4.5 m/s (10 mph); record the output of the frequency counter after 10 seconds. 

Determine the roll speed, vact, using the following equation: 

roll

act

f d v n

  

 Eq. 1066.235-1 

Where: 

f = frequency of the dynamometer speed sensing device, accurate to at least four significant 

figures. 

droll = nominal roll diameter, accurate to the nearest 1.0 mm, consistent with §1066.225(d). 

n = the number of pulses per revolution from the dynamometer roll speed sensor. 

Example:

f = 2.9231 Hz = 2.9231 s-1 

droll = 904.40 mm = 0.90440 m 

n = 1 pulse/rev 

act

2.9231 0.90440

1 v   

vact = 8.3053 m/s 

(ii) Repeat the steps in paragraph (c)(1)(i) of this section for the maximum speed expected during 

testing and at least two additional evenly spaced speed points between the starting speed and the 

maximum speed point.

(iii) Compare the calculated roll speed, vact, to each corresponding speed set point, vref, to 

determine values for speed error at each set point, verror, using the following equation: 

verror = vact - vref

Eq. 1066.235-2 

Example:

vact = 8.3053 m/s 

vref = 8.3000 m/s 

verror = 8.3053 – 8.3000 = 0.0053 m/s

Deleted: instrument

Deleted: between

Deleted: 2

Deleted: and the maximum speed expected during 

testing;

Deleted: Sact

Deleted: in s-1, 

Deleted: in m, 

Deleted: .01

Deleted: Sact

Deleted: Sact

Deleted: the

Deleted: Sref

Deleted: value

Deleted: , Serror

Deleted: Serror = Sact - Sref¶

Deleted: Sact

Deleted: Sref

Deleted: Serror
(2) Frequency method. Install a piece of tape in the shape of an arrowhead on the surface of the 

dynamometer roll near the outer edge. Put a reference mark on the deck plate in line with the 

tape. Install a stroboscope or photo tachometer on the deck plate and direct the flash toward the 

tape on the roll. The stroboscope or photo tachometer must be calibrated according to the 

instrument manufacturer’s instructions and be capable of measuring with enough accuracy to 

perform the procedure as specified in this paragraph (c)(2). Determine the speed error as 

follows: 

(i) Set the dynamometer to speed control mode. Set the dynamometer speed to a speed value of 

approximately 4.5 m/s (10 mph). Tune the stroboscope or photo tachometer until the signal 

matches the dynamometer roll speed. Record the frequency. Determine the roll speed, yact, 

using Eq. 1066.235-1, using the stroboscope or photo tachometer’s frequency for f. 

(ii) Repeat the steps in paragraph (c)(2)(i) of this section for the maximum speed expected during 

testing and at least two additional evenly spaced speed points between the starting speed and the 

maximum speed point.

(iii) Compare the calculated roll speed, vact, to each corresponding speed set point, vref, to 

determine values for speed error at each set point, yerror, using Eq. 1066.235-2.

(d) Performance evaluation. The speed error determined in paragraph (c) of this section may not 

exceed ±0.02 m/s at any speed set point. 

§1066.240 Torque transducer verification. 

Verify torque-measurement systems by performing the verifications described in §§1066.270 

and 1066.280. 

§1066.245 Response time verification. 

(a) Overview. This section describes how to verify the dynamometer’s response time to a 

tractive effort force step change. 

(b) Scope and frequency. Perform this verification upon initial installation, within 370 days 

before testing (i.e., annually), and after major maintenance. 

(c) Procedure. Use the dynamometer’s automated process to verify response time. You may 

perform this test either at two different inertia settings corresponding approximately to the 

minimum and maximum vehicle weights you expect to test or using base inertia and two 

acceleration rates that cover the range of acceleration rates experienced during testing (for 

example 0.5 and 8 mph/s). Use good engineering judgment to select road-load coefficients 

representing vehicles of the appropriate weight. Determine the dynamometer’s settling response 

time, ts, based on the point at which there are no measured results more than 10 % above or 

below the final equilibrium value, as illustrated in Figure 1 of this section. The observed settling 

response time must be less than 100 milliseconds for each inertia setting. 

Deleted: Use the method described in this 

paragraph (c)(2) only if the dynamometer does not 

have a readily available output signal for speed 

sensing.

Deleted: single

Deleted: arrow

Deleted: between 15 kph and the maximum speed 

expected during testing.

Deleted: Equation

Deleted: yact

Deleted: the

Deleted: yref

Deleted: a value

Deleted: , vyerror

Deleted: Equation

Deleted: .(

Deleted: and calibration

Deleted: Calibrate

Deleted: as

Deleted: 40 CFR 1065.310

Deleted: Perform

Deleted: .
Figure 1 of §1066.245—Example of a settling response time diagram. 

Time (t)

ts

Response

1.1

1.0

0.9

§1066.250 Base inertia verification. 

(a) Overview. This section describes how to verify the dynamometer’s base inertia. 

(b) Scope and frequency. Perform this verification upon initial installation and after major 

maintenance (such as maintenance that could affect roll assembly inertia). 

(c) Procedure. Verify the base inertia using the following procedure: 

(1) Warm up the dynamometer according to the dynamometer manufacturer’s instructions. Set 

the dynamometer’s road-load inertia to zero, turning off any electrical simulation of road load 

and inertia so that the base inertia of the dynamometer is the only inertia present, and motor the 

rolls to 5 mph. Apply a constant force to accelerate the roll at a nominal rate of 1 mph/s. 

Measure the elapsed time to accelerate from 10 to 40 mph, noting the corresponding speed and 

time points to the nearest 0.01 mph and 0.01 s. Also determine average force over the 

measurement interval. 

(2) Starting from a steady roll speed of 45 mph, apply a constant force to the roll to decelerate 

the roll at a nominal rate of 1 mph/s. Measure the elapsed time to decelerate from 40 to 10 mph, 

noting the corresponding speed and time points to the nearest 0.01 mph and 0.01 s. Also 

determine average force over the measurement interval. 

(3) Repeat the steps in paragraphs (c)(1) and (2) of this section for a total of five sets of results at 

the nominal acceleration rate and the nominal deceleration rate. 

(4) Use good engineering judgment to select two additional acceleration and deceleration rate 

pairs that cover the middle and upper rates expected during testing. Repeat the steps in 

paragraphs (c)(1) through (3) of this section at each of these additional acceleration and 

deceleration rates. 

Deleted: .

Deleted: rates
(5) Determine the base inertia, Ib, for each measurement interval using the following equation: 

b

final init

F I v v

t

 



Eq. 1066.250-1 

Where: 

F = average dynamometer force over the measurement interval as measured by the dynamometer.

vfinal = roll surface speed at the end of the measurement interval to the nearest 0.01 mph. 

vinit = roll surface speed at the start of the measurement interval to the nearest 0.01 mph. 

t = elapsed time during the measurement interval to the nearest 0.01 s. 

Example:

F = 1.500 lbf = 48.26 ft·lbm/s2 

vfinal = 40.00 mph = 58.67 ft/s 

vinit = 10.00 mph = 14.67 ft/s 

t = 30.00 s 

b

48.26

58.67 14.67

30.00

I  

Ib = 32.90 lbm 

(6) Calculate the base inertia error, Iberror, for each of the thirty measured base inertia values, Ib, 

by comparing it to the manufacturer’s stated base inertia, Ibref, using the following equation: 

bref bact

berror

bref

100 % I I I

I

  

Eq. 1066.250-2 

Example:

Ibref = 32.96 lbm 

bact I = 32.90 lbm (from paragraph (c)(5) of this section)

berror

32.96 32.90 100 %

32.96

I   

Iberror = 0.18 % 

(7) Determine the base inertia arithmetic mean value, b I , from the ten acceleration and 

deceleration interval base inertia values for each of the three acceleration/deceleration rates. 

Then determine the base inertia arithmetic mean value, b I , from the three 

acceleration/deceleration rate mean base inertia values. Calculate base inertia mean values as 

described in 40 CFR 1065.602(b)

Comment [CAL1]: Equation updated. 

Deleted: , in ft·lbm/s2

Deleted: Sfinal

Deleted: Sinitial

Deleted: ial

Deleted: Sfinal

Deleted: Sinitial

Deleted: ial

Deleted: (6) Determine the arithmetic mean value 

of base inertia from the five measurements at each 

acceleration and deceleration rate. Calculate these 

six mean values as described in 40 CFR 1065.602(b). 

(7

Deleted: 33.01

Deleted: –

Deleted: 15
(8) Calculate the inertia error for the final mean base inertia value from paragraph (c)(7) of this 

section. Use Eq. 1066.250-2, substituting the final mean base inertia value from paragraph (c)(7) 

of this section for the individual base inertia. 

(d) Performance evaluation. The dynamometer must meet the following specifications to be used 

for testing under this part: 

(1) All base inertia errors determined under paragraph (c)(6) of this section may not exceed 

±1.0 %. 

(2) The mean base inertia error determined under paragraph (c)(8) of this section may not exceed 

±0.20 %. 

§1066.255 Parasitic loss verification. 

(a) Overview. Verify the dynamometer’s parasitic loss as described in this section, and correct 

as necessary. This procedure determines the dynamometer’s internal losses that it must 

overcome to simulate road load. Characterize these losses in a parasitic loss curve that the 

dynamometer uses to apply compensating forces to maintain the desired road-load force at the 

roll surface. 

(b) Scope and frequency. Perform this verification upon initial installation, after major 

maintenance, and upon failure of a verification in either §1066.270 or §1066.280. 

(c) Procedure. Perform this verification by following the dynamometer manufacturer’s 

specifications to establish a parasitic loss curve, taking data at fixed speed intervals to cover the 

range of vehicle speeds that will occur during testing. You may zero the load cell at a selected 

speed if that improves your ability to determine the parasitic loss. Parasitic loss forces may 

never be negative. Note that the torque transducers must be zeroed and spanned prior to 

performing this procedure. 

(d) Performance evaluation. Some dynamometers automatically update the parasitic loss curve 

for further testing. If this is not the case, compare the new parasitic loss curve to the original 

parasitic loss curve from the dynamometer manufacturer or the most recent parasitic loss curve 

you programmed into the dynamometer. You may reprogram the dynamometer to accept the 

new curve in all cases, and you must reprogram the dynamometer if any point on the new curve 

departs from the earlier curve by more than ±9.0 N for dynamometers capable of testing vehicles 

at or below 20,000 pounds GVWR or ±36.0 N (±8.0 lbf) for dynamometers not capable of 

testing vehicles at or below 20,000 pounds GVWR. 

§1066.260 Parasitic friction compensation evaluation. 

(a) Overview. This section describes how to verify the accuracy of the dynamometer’s friction 

compensation. 

(b) Scope and frequency. Perform this verification upon initial installation, after major 

maintenance, and upon failure of a verification in either §1066.270 or §1066.280. Note that this 

procedure relies on proper calibration of speed and torque, as described in §§1066.235 and

1066.240. You must also first verify the dynamometer’s parasitic loss curve as specified in 

§1066.255. 

(c) Procedure. Use the following procedure to verify the accuracy of the dynamometer’s friction 

compensation: 

(1) Warm up the dynamometer as specified by the dynamometer manufacturer. 

(2) Perform a torque verification as specified by the dynamometer manufacturer. For torque 

verifications relying on shunt procedures, if the results do not conform to specifications, 

Deleted: each

Deleted: value of 

Deleted: 6

Deleted: Equation

Deleted: 265

Deleted: inertias associated with each acceleration 

and deceleration rate

Deleted: inertias

Deleted: The

Deleted: error

Deleted: 7

Deleted: .50 % relative to any individual value.

Deleted: % relative to any mean value.

Deleted: and correct 

Deleted: These

Deleted: are characterized

Deleted: within 7 days of testing, and 

Deleted: the

Deleted: In some cases, the dynamometer

Deleted: s

Deleted: 4.5 N (±1.0 lbf).

Deleted: 

Deleted: within 7 days before testing, and 

Deleted: .

Deleted: verification or 
recalibrate the dynamometer using NIST-traceable standards as appropriate until the 

dynamometer passes the torque verification. Do not change the dynamometer’s base inertia to 

pass the torque verification. 

(3) Set the dynamometer inertia to the base inertia with the road-load coefficients A, B, and C set 

to 0. Set the dynamometer to speed-control mode with a target speed of 50 mph or a higher 

speed recommended by the dynamometer manufacturer. Once the speed stabilizes at the target 

speed, switch the dynamometer from speed control to torque control and allow the roll to coast 

for 60 seconds. Record the initial and final speeds and the corresponding start and stop times. If 

friction compensation is executed perfectly, there will be no change in speed during the 

measurement interval. 

(4) Calculate the power equivalent of friction compensation error, FCerror, using the following 

equation: 

  2 2

error init final 2

I FC v v

t   

Eq. 1066.260-1 

Where: 

I = dynamometer inertia setting. 

t = duration of the measurement interval, accurate to at least 0.01 s. 

vinit = the roll speed corresponding to the start of the measurement interval, accurate to at least 

0.05 mph.

vfinal = the roll speed corresponding to the end of the measurement interval, accurate to at least 

0.05 mph. 

Example:

I = 2000 lbm = 62.16 lbf·s2

/ft 

t = 60.0 s 

vinit = 9.2 mph = 13.5 ft/s 

vfinal = 10.0 mph = 14.7 ft/s 

  2 2

error

62.16 13.5 14.7

2 60.00

FC   

FCerror = –16.5 ft·lbf/s = –0.031 hp 

(5) The friction compensation error may not exceed ±0.15 hp for dynamometers capable of 

testing vehicles at or below 20,000 pounds GVWR, or ±0.6 hp for dynamometers not capable of 

testing vehicles at or below 20,000 pounds GVWR. 

§1066.265 Acceleration and deceleration verification. 

(a) Overview. This section describes how to verify the dynamometer’s ability to achieve 

targeted acceleration and deceleration rates. Paragraph (c) of this section describes how this 

verification applies when the dynamometer is programmed directly for a specific acceleration or 

deceleration rate. Paragraph (d) of this section describes how this verification applies when the 

dynamometer is programmed with a calculated force to achieve a targeted acceleration or 

deceleration rate. 

(b) Scope and frequency. Perform this verification or an equivalent procedure upon initial 

installation and after major maintenance that could affect acceleration and deceleration accuracy. 

Note that this procedure relies on proper calibration of speed as described in §1066.235. 

Deleted: 10

Deleted: , in lbf·s2/ft

Deleted: Sfinal = the roll speed corresponding to the 

end of the measurement interval, accurate to at least 

0.1 mph.¶

Sinit

Deleted: 1

Deleted: 

Deleted: Sfinal

Deleted: Sinit

Deleted: 1 hp.
(c) Verification of acceleration and deceleration rates. Activate the dynamometer’s function 

generator for measuring roll revolution frequency. If the dynamometer has no such function 

generator, set up a properly calibrated external function generator consistent with the verification 

described in this paragraph (c). Use the function generator to determine actual acceleration and 

deceleration rates as the dynamometer traverses speeds between 10 and 40 mph at various 

nominal acceleration and deceleration rates. Verify the dynamometer’s acceleration and 

deceleration rates as follows: 

(1) Set up start and stop frequencies specific to your dynamometer by identifying the rollrevolution frequency, f, in revolutions per second (or Hz) corresponding to 10 mph and 40 mph 

vehicle speeds, accurate to at least four significant figures, using the following equation: 

roll

v n f d   

Eq. 1066.265-1 

Where: 

v = the target roll speed, in inches per second (corresponding to drive speeds of 10 mph or 40 

mph). 

n = the number of pulses from the dynamometer’s roll-speed sensor per roll revolution. 

droll = roll diameter, in inches. 

(2) Program the dynamometer to accelerate the roll at a nominal rate of 1 mph/s from 10 mph to 

40 mph. Measure the elapsed time to reach the target speed, to the nearest 0.01 s. Repeat this 

measurement for a total of five runs. Determine the actual acceleration rate for each run, aact, 

using the following equation: 

final init

act

v v a t 

Eq. 1066.265-2 

Where: 

aact = acceleration rate (decelerations have negative values). 

vfinal = the target value for the final roll speed. 

vinit = the setpoint value for the initial roll speed. 

t = time to accelerate from vinit to vfinal. 

Example:

vfinal = 40 mph 

vinit = 10 mph 

t = 30.003 s 

act

40.00 10.00

30.03 a  

aact = 0.999 mph/s 

(3) Program the dynamometer to decelerate the roll at a nominal rate of 1 mph/s from 40 mph to 

10 mph. Measure the elapsed time to reach the target speed, to the nearest 0.01 s. Repeat this 

measurement for a total of five runs. Determine the actual acceleration rate, aact, using Eq.

1066.265-2 

Deleted: S

Deleted: Sfinal

Deleted: Sinit

Deleted: Sinit

Deleted: Sfinal

Deleted: Sinal

Deleted: Sinit

Deleted: Equation
(4) Repeat the steps in paragraphs (c)(2) and (3) of this section for additional acceleration and 

deceleration rates in 1 mph/s increments up to and including one increment above the maximum 

acceleration rate expected during testing. Average the five repeat runs to calculate a mean 

acceleration rate, act a , at each setting. 

(5) Compare each mean acceleration rate, act a , to the corresponding nominal acceleration rate, 

aref, to determine values for acceleration error, aerror, using the following equation: 

act ref

error

ref

100 % a a a a

  

Eq. 1066.265-3 

Example:

act a = 0.999 mph/s 

aref = 1 mph/s 

error

0.999 1 100 %

1 a   

aerror = –0.100 % 

(d) Verification of forces for controlling acceleration and deceleration. Program the 

dynamometer with a calculated force value and determine actual acceleration and deceleration 

rates as the dynamometer traverses speeds between 10 and 40 mph at various nominal 

acceleration and deceleration rates. Verify the dynamometer’s ability to achieve certain 

acceleration and deceleration rates with a given force as follows: 

(1) Calculate the force setting, F, using the following equation: 

FIa   b

Eq. 1066.265-4 

Where: 

Ib = the dynamometer manufacturer’s stated base inertia, in lbf·s2

/ft. 

a = nominal acceleration rate, in ft/s2

. 

Example:

Ib = 2967 lbm = 92.217 lbf·s2

/ft

a = 1 mph/s = 1.4667 ft/s2 

F   92.217 1.4667

F = 135.25 lbf

(2) Set the dynamometer to road-load mode and program it with a calculated force to accelerate 

the roll at a nominal rate of 1 mph/s from 10 mph to 40 mph. Measure the elapsed time to reach 

the target speed, to the nearest 0.01 s. Repeat this measurement for a total of five runs. 

Determine the actual acceleration rate, aact, for each run using Eq. 1066.265-2. Repeat this step 

to determine measured “negative acceleration” rates using a calculated force to decelerate the 

roll at a nominal rate of 1 mph/s from 40 mph to 10 mph. Average the five repeat runs to 

calculate a mean acceleration rate, act a , at each setting. 

Deleted: 

Deleted: Equation
(3) Repeat the steps in paragraph (d)(2) of this section for additional acceleration and 

deceleration rates as specified in paragraph (c)(4) of this section. 

(4) Compare each mean acceleration rate, act a , to the corresponding nominal acceleration rate, 

aref, to determine values for acceleration error, aerror, using Eq. 1066.265-3

(e) Performance evaluation. The acceleration error from paragraphs (c)(5) and (d)(4) of this 

section may not exceed ±1.0 %. 

§1066.270 Unloaded coastdown verification. 

(a) Overview. Use force measurements to verify the dynamometer’s settings based on 

coastdown procedures. 

(b) Scope and frequency. Perform this verification upon initial installation, within 7 days of 

testing, and after major maintenance. 

(c) Procedure. This procedure verifies the dynamometer’s settings derived from coastdown 

testing. For dynamometers that have an automated process for this procedure, perform this 

evaluation by setting the initial speed, final speed, inertial coefficients, and road-load coefficients 

as required for each test, using good engineering judgment to ensure that these values properly 

represent in-use operation. Use the following procedure if your dynamometer does not perform 

this verification with an automated process: 

(1) Warm up the dynamometer as specified by the dynamometer manufacturer. 

(2) With the dynamometer in coastdown mode, set the dynamometer inertia for the smallest 

vehicle weight that you expect to test and set A, B, and C road-load coefficients to values typical 

of those used during testing. Program the dynamometer to coast down over the dynamometer 

operational speed range (typically from a speed of 80 mph through a minimum speed at or below

10 mph). Perform at least one coastdown over this speed range, collecting data over each 10 

mph interval. 

(3) Repeat the steps in paragraph (c)(2) of this section with the dynamometer inertia and roadload coefficients set for the largest vehicle weight that you expect to test. 

(4) Determine the average coastdown force, F, for each speed and inertia setting for each of the 

coastdowns performed using the following equation: 

Iv v  init final F

t

  

Eq. 1066.270-1 

Where: 

F = the average force measured during the coastdown for each speed interval and inertia setting, 

expressed in lbf·s2/ft and rounded to four significant figures.

I = the dynamometer’s inertia setting, in lbf· s2/ft. 

vinit = the speed at the start of the coastdown, expressed in ft/s and rounded to four significant 

figures. 

vfinal = the speed at the end of the coastdown interval, rounded to four significant figures.

t = coastdown time for each speed and inertia setting, accurate to at least 0.01 s. 

Example:

I = 2000 lbm = 65.17 lbf·s2

/ft

vinit = 25 mph = 36.66 ft/s 

vfinal = 15 mph = 22.0 ft/s

t = 5.00 s 

Deleted: Equation

Deleted: 4

Deleted: and

Deleted: and the

Deleted: tooperate at 10

Deleted: .

Deleted: a

Deleted: two times at

Deleted: setting. Repeat these coastdown steps in

Deleted: increments up to and including one 

increment above the maximum speed expected 

during testing. You may stop the verification before 

reaching 0 mph, with any appropriate adjustments in 

calculating the results

Deleted: 

Deleted: Ssi

Deleted: setting 

Deleted: 

Deleted: 

Deleted: Ssi = 10

Deleted: 14
65.17 36.66 22.0  

5.00

F   

F = 191.1 lbf 

(5) Calculate the target value of coastdown force, Fref, based on the applicable dynamometer 

parameters for each speed and inertia setting. 

(6) Compare the mean value of the coastdown force measured for each speed and inertia setting, 

Fact , to the corresponding Fref to determine values for coastdown force error, Ferror, using the 

following equation: 

act ref

error

ref

100 % F F F

F

  

Eq. 1066.270-2 

Example:

Fref = 192 lbf 

F act = 191 lbf 

error

191 192 100 %

192

F   

Ferror = 0.5 % 

(d) Performance evaluation. The coastdown force error determined in paragraph (c) of this 

section may not exceed the following:

(1) For vehicles at or below 20,000 pounds GVWR, calculate Ferrormax from the following 

formula:

Ferrormax (%) = (2.2 lbf/Fref)·100 

Eq. 1066.270-3

Example:

Fref = 192 lbf

Ferrormax (%) = (2.2/192)·100 = 1.14%

(2) For vehicles above 20,000 pounds GVWR, the maximum allowable error, Ferrormax, for all 

speed and inertia settings is ±1.0 % or ±39.2 N, whichever is greater.

(e) If the dynamometer is not able to meet this requirement, diagnose and repair the 

dynamometer before continuing with emission testing. Diagnosis should include performing the 

verifications in §1066.255 and §1066.260.

§1066.280 Daily dynamometer readiness verification.

(a) Overview. This section describes how to verify that the dynamometer is ready for emission 

testing.

(b) Scope and frequency. Perform this verification upon initial installation, within 1 day before 

testing, and after major maintenance.

(c) Procedure. For dynamometers that have an automated process for this verification procedure, 

perform this evaluation by setting the initial speed and final speed and the inertial and road-load 

coefficients as required for the test, using good engineering judgment to ensure that these values 

Deleted: –

Deleted: 7)

Deleted: maximum allowable

Deleted: ,

Deleted: , for all speed and inertia settings is 

calculated

Deleted: , except that Ferrormax for vehicles with 

GVWR above 14,000 lbs may be up to ±1.0 %:
properly represent in-use operation. Use the following procedure if your dynamometer does not 

perform this verification with an automated process:

(1) With the dynamometer in coastdown mode, set the dynamometer inertia to the base inertia 

with the road-load coefficient A set to 20 lbf (or a force that results in a coastdown time of less 

than 10 minutes) and coefficients B and C set to 0. Program the dynamometer to coast down for 

one 10 mph interval from 55 mph down to 45 mph. If your dynamometer is not capable of 

performing one discrete coastdown, then coast down with preset 10 mph intervals that include a

55 mph to 45 mph interval.

(2) Perform the coastdown.

(3) Determine the coastdown force and coastdown force error using Eqs. 1066.270-1 and 

1066.270-2.

(d) Performance evaluation. The coastdown force error determined in paragraph (c) of this 

section may not exceed the following:

(1) For vehicles at or below 20,000 pounds GVWR, ±1.0 % or ±9.8 N (±2.2 lbf), whichever is 

greater. 

(2) For vehicles above 20,000 pounds GVWR, ±1.0 % or ±39.2 N (±8.8 lbf), whichever is 

greater.

(e) If the verification results fail to meet the performance criteria in paragraph (d) of this section,

perform the procedure up to two additional times. If the dynamometer is consistently unable to 

meet the performance criteria, diagnose and repair the dynamometer before continuing with

emission testing. Diagnosis should include performing the verifications in §1066.255 and 

§1066.260.

§1066.290 Driver’s aid. 

Use good engineering judgment to provide a driver’s aid that facilitates compliance with the 

requirements of §1066.430. Verify the speed accuracy of the driver’s aid as described in 

§1066.235. 
Subpart D—Coastdown 

§1066.301 Overview of coastdown procedures. 

(a) The coastdown procedures described in this subpart are used to determine the load 

coefficients (A, B, and C) for the simulated road-load equation in §1066.210(d)(3). 

(b) The general procedure for performing coastdown tests and calculating load coefficients is 

described in SAE J1263 and SAE J2263 (incorporated by reference in §1066.1010). This 

subpart specifies certain deviations from those procedures for certain applications. 

(c) Use good engineering judgment for all aspects of coastdown testing. For example, minimize 

the effects of grade by performing coastdown testing on reasonably level surfaces and 

determining coefficients based on average values from vehicle operation in opposite directions 

over the course. 

§1066.305 Coastdown procedures for motor vehicles at or below 14,000 pounds GVWR.

For motor vehicles at or below 14,000 pounds GVWR, develop representative road-load 

coefficients to characterize each test vehicle. Calculate road-load coefficients by performing 

coastdowns using the provisions of SAE J1263 and SAE J2263 (incorporated by reference in 

§1066.1010). Perform coastdowns at a starting speed as specified in SAE J2263, or at the 

highest speed from the range of applicable duty cycles as specified in §1066.810(c). Use the 

same road-load coefficients for all duty cycles. However, if your test conditions are substantially 

different from the conditions represented by your road-load coefficients, such as coldtemperature testing, you may use good engineering judgment to develop separate road-load 

coefficients.

§1066.310 Coastdown procedures for vehicles above 14,000 pounds GVWR. 

This section describes coastdown procedures that are unique to vehicles above 14,000 pounds 

GVWR. These procedures are valid for calculating road-load coefficients for chassis and posttransmission powerpack testing and for calculating drag area (CDA) for use in the GEM 

simulation tool under 40 CFR part 1037. 

(a) Determine load coefficients by performing a minimum of 16 valid coastdown runs (8 in each 

direction). 

(b) Follow the provisions of Sections 1 through 9 of SAE J1263, and SAE J2263 (incorporated 

by reference in §1066.1010), except as described in this paragraph (b). The terms and variables 

identified in this paragraph (b) have the meaning given in SAE J1263 or J2263 unless specified 

otherwise. 

(1) The test condition specifications of SAE J1263 apply except as follows for wind and road 

conditions: 

(i) We recommend that you do not perform coastdown testing on days for which winds are 

forecast to exceed 6.0 mph. 

(ii) The grade of the test track or road must not be excessive (considering factors such as road

safety standards and effects on the coastdown results). Road conditions should follow Section 

7.4 of SAE J1263, except that road grade may exceed 0.5%. If road grade is greater than 0.02% 

over the length of the test surface, then the road grade as a function of distance along the length 

of the test surface must be incorporated into the analysis. To calculate the force due to grade use 

Section 11.5 of SAE J2263. 

Deleted: 710

Deleted: heavy-duty

Deleted: heavy-duty motor vehicles.Note as 

specified in the standard setting parts, this section 

does not apply for certain heavy-duty vehicles, such 

as those regulated under 40 CFR part 86, subpart S

Deleted: 710

Deleted: asroad

Deleted: in
(2) Operate the vehicle at a top speed above 70 mph, or at its maximum achievable speed if it 

cannot reach 70 mph. If a vehicle is equipped with a vehicle speed limiter that is set for a 

maximum speed below 70 mph, you must disable the vehicle speed limiter. Start the test at or 

above 70 mph or at the vehicle’s maximum achievable speed if it cannot reach 70 mph. Collect 

data through a minimum speed at or below 15 mph. Data analysis for valid coastdown runs must 

include a maximum speed as described in this paragraph (b)(2) and a minimum speed of 15 mph. 

(3) Gather data regarding wind speed and direction, in coordination with time-of-day data, using 

at least one stationary electro-mechanical anemometer and suitable data loggers meeting the 

specifications of SAE J1263, as well as the following additional specifications for the 

anemometer placed adjacent to the test surface: 

(i) Calibrate the equipment by running the zero-wind and zero-angle calibrations within 24 hours 

before conducting the coastdown procedures. If the coastdown procedures are not complete 24 

hours after calibrating the equipment, repeat the calibration for another 24 hours of data 

collection. 

(ii) Record the location of the anemometer using a GPS measurement device adjacent to the test 

surface (approximately) at the midway distance along the test surface used for coastdowns. 

(iii) Position the anemometer such that it will be at least 2.5 but not more than 3.0 vehicle widths 

from the test vehicle’s centerline as the test vehicle passes the location of that anemometer. 

(iv) Mount the anemometer at a height that is within 6 inches of half the test vehicle’s maximum 

height. 

(v) Place the anemometer at least 50 feet from the nearest tree and at least 25 feet from the 

nearest bush (or equivalent roadside features). 

(vi) The height of the grass surrounding the stationary anemometer may not exceed 10% of the 

anemometer’s mounted height, within a radius equal to the anemometer’s mounted height. 

(4) You may split runs as per Section 9.3.1 of SAE J2263, but we recommend whole runs. If 

you split a run, analyze each portion separately, but count the split runs as one run with respect to 

the minimum number of runs required. 

(5) You may perform consecutive runs in a single direction, followed by consecutive runs in the 

opposite direction, consistent with good engineering judgment. Harmonize starting and stopping 

points to the extent practicable to allow runs to be paired. 

(6) All valid coastdown run times in each direction must be within 2.0 standard deviations of the 

mean of the valid coastdown run times (from 70 mph down to 15 mph) in that direction. 

Eliminate runs outside this range. After eliminating these runs you must have at least eight valid 

runs in each direction. You may use coastdown run times that do not meet these standard 

deviation requirements if we approve it in advance. In your request, describe why the vehicle is 

not able to meet the specified standard deviation requirements and propose an alternative set of 

requirements. 

(7) Analyze data for chassis and post-transmission powerpack testing or for use in the GEM 

simulation tool as follows:

(i) Follow the procedures specified in Section 10 of SAE J1263 or Section 11 of SAE J2263 to 

calculate coefficients for chassis and post-transmission powerpack testing.

(ii) Determine drag area, CDA, as follows instead of using the procedure specified in Section 10

of SAE J1263: 

(A) Measure vehicle speed at fixed intervals over the coastdown run (generally at 10 Hz), 

including speeds at or above 15 mph and at or below 70 mph. Establish the height or altitude 

Deleted: You must reach 

Deleted: of greater than 70 mphsuch that data 

collection of the coastdown can start at or 

Deleted: Data collection must occur 

Deleted: of 70 mph

Deleted: Run

Deleted: calibration data collection. ¶

(ii) The anemometer must have had its outputs 

recorded at a wind speed of 0.0 mph

Deleted: each

Deleted: test in which it is used

Deleted: iii

Deleted: iv

Deleted: v

Deleted: vi

Deleted: vii

Deleted: each direction

Deleted: (7

Deleted: SAE J1263, 

Deleted: i
corresponding to each interval as described in SAE J2263 if you need to incorporate the effects 

of road grade. 

(B) Calculate the vehicle’s effective mass, Me, in kg by adding 56.7 kg to the measured vehicle 

mass for each tire making road contact. This accounts for the rotational inertia of the wheels and 

tires. 

(C) Calculate the road-load force for each measurement interval, Fi, for values of i ≥ 1 using the 

following equation: 

i i1

i e

v v F M

t

    

Eq. 1066.310-1 

Where: 

Me = the vehicle’s effective mass, expressed to at least the nearest 0.1 kg. 

v = vehicle speed at the beginning and end of the measurement interval. 

Δt = elapsed time over the measurement interval, in seconds. 

(D) Plot the data from all the coastdown runs on a single plot of Fi vs. vi

2

 to determine the slope 

correlation, D, based on the following equation: 

2

ie m i

h F M g A Dv s

    



Eq. 1066.310-2 

Where: 

g = gravitational acceleration = 9.81 m/s2

. 

Δh = change in height or altitude over the measurement interval, in m. Assume Δh = 0 if you are 

not correcting for grade. 

Δs = distance the vehicle travels down the road during the measurement interval, in m. 

Am = the calculated value of the y-intercept based on the curve-fit. 

(E) Calculate drag area, CDA, in m2

 using the following equation: 

adj

D

2 D

C A



 

Eq. 1066.310-3 

Where: 

ρ = air density at reference conditions = 1.17 kg/m3

. 

adj

act

98.21

293

T D D

p

             

Eq. 1066.310-4 

T = average ambient absolute temperature during testing, in K. 

act p = actual average ambient pressuring during the test, in kPa. 

(8) Determine the A, B, and C coefficients identified in §1066.210 as follows:

(i) For chassis and post-transmission powerpack testing, follow the procedures specified in 

Section 10 of SAE J1263 or Section 12 of SAE J2263.

(ii) For the GEM simulation tool, use the following values:

A = Am

Deleted: ii

Deleted: iii

Deleted: Vehicle

Deleted: Let v0 = 0.

Deleted: Elapsed

Deleted: iv

Deleted: Gravitational

Deleted: Change

Deleted: Distance

Deleted: v

Deleted: m

Deleted: Air

Comment [CAL2]: Equation updated. 

Deleted: Average

Comment [CAL3]: Updated. 

Deleted: Average
B = 0 

C = Dadj

§1066.320 Dynamometer road-load setting.

Determine dynamometer road-load settings for chassis testing by following SAE J2264 

(incorporated by reference in §1066.1010).
Subpart E— Preparing Vehicles and Running an Exhaust Emission Test

§1066.401 Overview. 

(a) Use the procedures detailed in this subpart to measure vehicle emissions over a specified 

drive schedule. Different procedures may apply for criteria pollutants and greenhouse gas 

emissions as described in subpart I of this part or the standard-setting part. This subpart 

describes how to: 

(1) Determine road-load power, test weight, and inertia class. 

(2) Prepare the vehicle, equipment, and measurement instruments for an emission test. 

(3) Perform pre-test procedures to verify proper operation of certain equipment and analyzers 

and to prepare them for testing. 

(4) Record pre-test data. 

(5) Sample emissions. 

(6) Record post-test data. 

(7) Perform post-test procedures to verify proper operation of certain equipment and analyzers. 

(8) Weigh PM samples. 

(b) The overall test generally consists of prescribed sequences of fueling, parking, and driving at 

specified test conditions. An exhaust emission test generally consists of measuring emissions 

and other parameters while a vehicle follows the drive schedules specified in the standard-setting 

part. There are two general types of test cycles: 

(1) Transient cycles. Transient test cycles are typically specified in the standard-setting part as a 

second-by-second sequence of vehicle speed commands. Operate a vehicle over a transient cycle 

such that the speed follows the target values. Proportionally sample emissions and other 

parameters and use the calculations in 40 CFR part 1065, subpart G, or subpart G of this part to 

calculate emissions. The standard-setting part may specify three types of transient testing based 

on the approach to starting the measurement, 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) Cruise cycles. Cruise test cycles are typically specified in the standard-setting part as a 

discrete operating point that has a single speed command. 

(i) Start a cruise cycle as a hot running test, where you start to measure emissions after the 

engine is started and warmed up and the vehicle is running at the target test speed. 

(ii) Sample emissions and other parameters for the cruise cycle in the same manner as a transient 

cycle, with the exception that the reference speed value is constant. Record instantaneous and 

mean speed values over the cycle. 

§1066.407 Vehicle preparation and preconditioning. 

Prepare the vehicle for testing (including measurement of evaporative and refueling emissions,

as required) as described in the standard-setting part. 

§1066.410 Dynamometer test procedure. 

Deleted: Vehicle Preparation

Deleted: a

Deleted: An

Deleted: 86, subpart B, or 40 CFR part 

Deleted: This section describes steps to take before 

measuring exhaust emissions for those vehicles that 

are subject to 

Deleted: or

Deleted: emission tests

Deleted: specified in the standard setting part. 

Other preliminary procedures may apply as specified 

in 

Deleted: (a) Prepare the vehicle for testing as 

described in 40 CFR 86.131-00.(b) If testing will 

include measurement of refueling emissions, 

perform the vehicle preconditioning steps as 

described in 40 CFR 86.153-98. Otherwise, perform 

the vehicle preconditioning steps as described in 40 

CFR 86.132-00.¶
(a) Dynamometer testing may consist of multiple drive cycles with both cold-start and hot-start 

portions, including prescribed soak times before each test interval. The standard-setting part 

identifies the driving schedules and the associated sample intervals, soak periods, engine startup 

and shutdown procedures, and operation of accessories, as applicable. Not every test interval

includes all these elements. 

(b) Place the vehicle onto the dynamometer without starting the engine (for cold-start test cycles) 

or drive the vehicle onto dynamometer (for hot-start and hot-running cycles only) and position a 

fan that directs cooling air to the vehicle during dynamometer operation as described in this 

paragraph (b). This generally requires squarely positioning the fan in front of the vehicle and 

directing the airflow to the vehicle’s radiator. Use good engineering judgment to design and 

configure fans to cool the test vehicle in a way that properly simulates in-use operation, 

consistent with the specifications of §1066.105. Except for the following special cases, use a 

road-speed modulated fan meeting the requirements of §1066.105(c)(2) or (d) that is placed 

within 90 cm of the front of the vehicle and ensure that the engine compartment cover (i.e., 

hood) is closed:

(1) For SC03 and AC17 testing, use a road-speed modulated fan meeting the requirements of 

§1066.105(c)(3) that is placed within 60 to 90 cm of the front of the vehicle and ensure that the 

engine compartment cover is closed. Position the discharge nozzle such that its lowest point is 

not more than 16 cm above the floor of the test cell.

(2) For FTP, LA-92, US06, or HFET testing of vehicles at or below 14,000 pounds GVWR, you 

may use a fixed-speed fan meeting the requirements of §1066.105(c)(4) or (c)(5) as specified in 

the following table, with the engine compartment cover open:

Table 1 of §1066.410–Fixed-speed fan capacity and position specifications. 

Test cycle Maximum fan capacity Approximate distance from 

the front of the vehicle

FTP Up to 2.50 m3/s 0 to 30 cm

US06 Up to 7.10 m3/s 0 to 60 cm

LA-92 Up to 7.10 m3/s 0 to 60 cm

HFET Up to 2.50 m3/s 0 to 30 cm

(c) Record the vehicle’s speed trace based on the time and speed data from the dynamometer

using the recording frequencies given in §1066.122 Table 1. Record speed to at least the nearest 

0.01 mph and time to at least the nearest 0.1 s. 

(d) You may perform practice runs for operating the vehicle and the dynamometer controls to 

meet the driving tolerances specified in §1066.430 or adjust the emission sampling equipment. 

Verify that the accelerator pedal allows for enough control to closely follow the prescribed 

driving schedule. We recommend that you verify your ability to meet the minimum dilution 

factor requirements of §1066.110(b)(2)(iii)(B) during these practice runs. 

(e) Inflate tires on drive wheels according to the vehicle manufacturer’s specifications. The tire 

pressure for drive wheels must be the same for dynamometer operation and for dynamometer

coastdown procedures used for determining road-load coefficients. Report these tire pressure 

values with the test results. 

(f) Tie down or load the test vehicle as needed to provide a normal force at the tire and 

dynamometer roll interface to prevent wheel slip. For vehicles above 14,000 pounds GVWR,

report this force with the test results. 

Deleted: phase. See the 

Deleted: for test cycles

Deleted: times for the appropriate vehicle category. 

A test phase consists of 

Deleted: (with accessories operated according to 

the standard-setting part), operation over the drive 

cycle, 

Deleted: engine 

Deleted: During dynamometer operation, 

Deleted: cooling 

Deleted: .

Deleted: within 30 centimeters of the

Deleted: with GVWR 

Deleted: lbs

Deleted: either of the following cooling fan 

configurations:¶

(i) Use 

Deleted: to appropriately direct cooling air to the 

vehicle

Deleted: . The 

Deleted: may not exceed 2.50 m3/s. If you 

determine that additional cooling is needed to 

properly represent in-use operation, use good 

engineering judgment to increase the fan’s capacity 

or use additional fans, subject to our approval

Deleted: (ii) Use a road-speed modulated fan 

system that achieves a linear speed of cooling air at 

the blower outlet that is within ±3.0 mph (±1.3 m/s) 

of the corresponding roll speed when vehicle speeds 

are between 5 and 30 mph (2.2 to 13.4 m/s), and 

within ±6.5 mph (±2.9 m/s) of the corresponding roll 

speed at higher vehicle speeds. The fan must provide 

no cooling air for vehicle speeds below 5 mph, 

unless we approve your request to provide cooling ... [1]

Deleted: 2.50 m3/s

Deleted: 2.5

Deleted: 3

Deleted: m/s or 0.1 

Deleted: 1

Deleted: 0

Deleted: to

Deleted: You may not measure emissions during a ... [2]

Deleted: the

Deleted: wheel tires

Deleted: drive wheels’ 

Deleted: For vehicles with GVWR above 14,000 ... [3]

Deleted: pull down mechanism that allows ... [4]

Deleted: forces that

Deleted: would see if a loaded vehicle were ... [5]

Deleted: loaded vehicle
(g) Use good engineering judgment when testing vehicles in four-wheel drive or all-wheel drive 

mode. (For purposes of this paragraph (g), the term four-wheel drive includes other multiple 

drive axle configurations.) This may involve testing on a dynamometer with a separate 

dynamometer roll for each drive axle. Alternatively, two drive axles may use a single roll, as 

described in §1066.210(d)(1). This testing may also involve operation on a single roll by

deactivating the second set of drive wheels. For all vehicles at or below 14,000 GVWR, we will 

test your vehicle using the same dynamometer mode of operation that you tested it in and those 

results will be considered the official test results. We may also test your vehicle in another 

dynamometer mode for information gathering purposes. If we choose to perform this additional 

testing, we will ask you to configure the vehicle to accommodate testing in the alternate 

dynamometer mode.

(h) Determine test weight as follows:

(1) For vehicles at or below 14,000 pounds GVWR, determine ETW as described in §1066.810. 

Set dynamometer vehicle inertia, I, based on dynamometer type, as follows: 

(i) For two-wheel drive dynamometers, set I = ETW.

(ii) For four-wheel drive dynamometers, set I = 0.985·ETW.

(2) For vehicles above 14,000 pounds GVWR, determine the vehicle’s effective mass as 

described in 1066.310. This is the test weight.

(i) Warm up the dynamometer as recommended by the dynamometer manufacturer. 

(j) Following the test, determine the actual driving distance by counting the number of 

dynamometer roll or shaft revolutions, or by integrating speed over the course of testing from a 

high-resolution encoder system. 

§1066.420 Vehicle operation. 

This section describes how to test a conventionally configured vehicle (vehicles with 

transmission shifters, foot pedal accelerators, etc). You may ask us to modify these procedures 

for vehicles that do not have these control features. 

(a) Start the vehicle as follows:

(1) At the beginning of the test cycle, start the vehicle according to the procedure described in 

the owners manual. In the case of hybrid vehicles, this would generally involve activating 

vehicle systems such that the engine will start when the vehicle’s control algorithms determine 

that the engine should provide power instead of or in addition to power from the rechargeable 

energy storage system (RESS). Unless we specify otherwise, engine starting throughout this part 

generally refers to this step of activating the system on hybrid vehicles, whether or not that 

causes the engine to start running.

(2) Place the transmission in gear as described by the test cycle in the standard-setting part. 

During idle operation, apply the brakes if necessary to keep the drive wheels from turning.

(b) If the vehicle does not start after your recommended maximum cranking time, wait and 

restart cranking according to your recommended practice. 

If you do not recommend such a cranking procedure, stop cranking after 10 seconds, wait for 10 

seconds, then start cranking again for up to 10 seconds. You may repeat this for up to three start 

attempts. If the vehicle does not start after three attempts, you must determine and record the

reason for failure to start. Shut off sampling systems and either turn the CVS off or disconnect 

the exhaust tube from the tailpipe during the diagnostic period to prevent flow through the 

exhaust system. Reschedule the vehicle for testing. This may require performing vehicle 

preparation and preconditioning if the testing needs to be rerun from a cold start. If failure to 

Deleted: , which may require disengaging

Deleted: , either with a switch available to the 

driver or by some other means; however, operating 

such a vehicle on a single roll may occurbut only if 

this mode of operation does not decrease emissions 

or energy consumption relative to normal in-use 

operation

Deleted: Alternatively, for heavy-duty motor 

vehicles, up to two drive axles may use a single drive 

roll, as described in §1066.210(d)(2).

Deleted: We may test such vehicles in four-wheel 

or all-wheel mode on one or more rolls to confirm 

that the alternate dynamometer procedures did not 

decrease emissions.

Deleted: 40 CFR part 86.129-00(h

Deleted: i

Deleted: Pre-test verification procedures and 

pre-test data collection
start occurs during a hot-start test, you may reschedule the hot-start test without repeating the 

cold-start test, as long as you bring the vehicle to a hot-start condition before starting the hotstart test.

(c) Repeat the recommended starting procedure if the engine has a false start (i.e., an incomplete 

start).

(d) Take the following steps if the engine stalls:

(1) If the engine stalls during an idle period, restart the engine immediately and continue the test. 

If you cannot restart the engine soon enough to allow the vehicle to follow the next acceleration, 

stop the driving schedule indicator and reactivate it when the vehicle restarts.

(2) Void the test if the vehicle stalls during vehicle operation. If this happens, remove the 

vehicle from the dynamometer, take corrective action, and reschedule the vehicle for testing. 

Record the reason for the malfunction (if determined) and any corrective action. See the 

standard-setting part for instructions about reporting these malfunctions. 

(e) Operate vehicles during testing as follows:

(1) Where we do not give specific instructions, operate the vehicle according to the 

recommendations in the owners manual, unless those recommendations are unrepresentative of 

what may reasonably be expected for in-use operation.

(2) If vehicles have features that preclude dynamometer testing, you may modify these features 

as necessary to allow testing, consistent with good engineering judgment, as long as it does not 

affect your ability to show that your vehicles comply with standards. Send us written 

notification describing these changes along with supporting rationale.

(3) Operate vehicles during idle as follows:

(i) For vehicles with automatic transmission, operate at idle with the transmission in “Drive” 

with the wheels braked, except that you may shift to “Neutral” for the first idle period and for 

any idle period longer than one minute. If you put the vehicle in “Neutral” during an idle, you 

must shift the vehicle into “Drive” with the wheels braked at least 5 seconds before the end of 

the idle period. Note that this does not preclude vehicle designs involving engine operation with 

stop-start functions where the engine stops when the brake is applied below a certain threshold 

speed and restarts upon release of the brake.

(ii) For vehicles with manual transmission, operate at idle with the transmission in gear with the 

clutch disengaged, except that you may shift to “Neutral” with the clutch engaged for the first 

idle period and for any idle period longer than one minute. If you put the vehicle in “Neutral” 

during idle, you must shift to first gear with the clutch disengaged at least 5 seconds before the 

end of the idle period. Note that this does not preclude vehicle designs involving engine 

operation with stop-start functions where the engine stops when the clutch is disengaged below a 

certain threshold speed and restarts upon reengagement of the clutch.

(4) Operate the vehicle with the appropriate accelerator pedal movement necessary to achieve the 

speed versus time relationship prescribed by the driving schedule. Avoid smoothing speed 

variations and excessive accelerator pedal perturbations.

(5) Operate the vehicle smoothly, following representative shift speeds and procedures. For 

manual transmissions, the operator shall release the accelerator pedal during each shift and 

accomplish the shift with minimum time. If the vehicle cannot accelerate at the specified rate, 

operate it at maximum available power until the vehicle speed reaches the value prescribed for 

that time in the driving schedule.

(6) Decelerate as follows:
(i) For vehicles with automatic transmission, use the brakes or accelerator pedal as necessary, 

without manually changing gears, to maintain the desired speed.

(ii) For vehicles with manual transmission, shift gears in a way that represents reasonable shift 

patterns for in-use operation, considering vehicle speed, engine speed, and any other relevant

variables. Disengage the clutch when the speed drops below 15 mph, when engine roughness is 

evident, or when good engineering judgment indicates the engine is likely to stall. 

Manufacturers may recommend shift guidance in the owners manual that differs from the shift 

schedule during testing as long as both shift schedules are included in the application for 

certification. In this case, we may use the shift schedule based on the shift pattern described in 

the owners manual.

§1066.425 Test preparation.

(a) Follow the procedures for PM sample preconditioning and tare weighing as described in 40 

CFR 1065.590 if you need to measure PM emissions. 

(b) For vehicles above 14,000 pounds GVWR with compression-ignition engines, verify the 

amount of nonmethane hydrocarbon contamination as described in 40 CFR 1065.520(g).

(c) 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 (c). For 

purposes of this paragraph (c), “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 must be (20 to 30) °C. See §1066.430(i) for circumstances under 

which ambient temperatures must remain within this range during the test. 

(2) Dilution air conditions must meet the specifications in §1066.110(b)(2). We recommend 

verifying dilution air conditions just before starting each test interval.

(d) Control test cell ambient air humidity as follows:

(1) For vehicles at or below 14,000 pounds GVWR, follow the humidity requirements in Table 1 

of this section, unless the standard-setting part specifies otherwise. When complying with 

humidity requirements in the table, where no tolerance is specified, use good engineering 

judgment to maintain the humidity level near the specified value within the limitations of your 

test facility.

(2) For vehicles above 14,000 pounds GVWR, you may test vehicles at any humidity.

Table 1 of §1066.425–Test cell humidity requirements. 

Test cycle

Humidity requirement 

(grains H2O per pound

dry air)

Tolerance (grains H2O

per pound dry air)

AC17 69 ± 5 average, 

± 10 instantaneous

FTP1 and LA-92 50

HFET 50

SC03 100 ± 5

US06 50

1

FTP humidity requirement does not apply for cold (-7°C), intermediate 

(10 °C), and hot (35 °C) temperature testing.

(e) You may perform a final calibration of proportional-flow control systems, which may include 

performing practice runs. 

Deleted: your engine must comply with a PM 

standard

Deleted: (b

Deleted: b

Deleted: b

Deleted: m

Deleted: (2) Atmospheric pressure must be 

(80.000 to 103.325) kPa. You are not required to 

verify atmospheric pressure prior to a hot-start test 

interval for testing that also includes a cold start.¶

(3

Deleted: 40 CFR 1065.140, except in cases where 

you preheat your CVS before a cold-start test.

Deleted: phase

Deleted: (c) You may test vehicles at any intakeair humidity.

Deleted: d
(f) You may perform the following procedure to precondition sampling systems: 

(1) Operate the vehicle over the test cycle. 

(2) Operate any dilution systems at their expected flow rates. Prevent aqueous condensation in 

the dilution systems as described in 40 CFR 1065.140(c)(6), taking into account allowances 

given in §1066.110(b)(2)(iv). 

(3) Operate any PM sampling systems at their expected flow rates. 

(4) Sample PM using any sample media. You may change sample media during preconditioning. 

You must 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. 

(g) 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, 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. 

(5) Allow heated or cooled components such as sample lines, filters, chillers, and pumps to 

stabilize at their operating temperatures. 

(6) Adjust the sample flow rates to desired levels using bypass flow, if desired. 

(7) Zero or re-zero any electronic integrating devices before the start of any test interval. 

(8) Select gas analyzer ranges. You may not switch the gain of an analyzer’s analog operational 

amplifier(s) during a test. However, you may switch (automatically or manually) gas analyzer 

ranges during a test if such switching changes only the range over which the digital resolution of 

the instrument is applied. For batch analyzers, select ranges prior to final bag analysis.

(9) Zero and span all continuous gas analyzers using gases that meet the specifications of 40 

CFR 1065.750. For FID analyzers, you may account for the carbon number of your span gas 

either during the calibration process or when calculating your final emission value. For example, 

if you use a C3H8 span gas of concentration 200 ppm (mol/mol), you may span the FID to 

respond with a value of 600 ppm (mol/mol) of carbon or 200 ppm of propane. However, if 

your FID response is equivalent to propane, include a factor of three to make the final calculated 

hydrocarbon mass consistent with a molar mass of 13.875389. When utilizing an NMC-FID, 

span the FID analyzer consistent with the determination of their respective response factors, RF, 

and penetration fractions, PF, according to 40 CFR 1065.365. 

(10) 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, use good engineering judgment to decide whether or not to re-zero, re-span, 

or re-calibrate a gas analyzer before starting a test. 

(11) If you correct for dilution air background concentrations of associated engine exhaust 

constituents, start sampling and recording background concentrations at the same time you start 

sampling exhaust gases. 

(12) Turn on cooling fans immediately before starting the test. 

(h) Proceed with the test sequence described in §1066.430.

Deleted: e

Deleted: .

Deleted: for at least 10 min

Deleted: (7) Proceed with the test sequence 

described in §1066.430.¶

(f) Verify the amount of nonmethane hydrocarbon 

(or equivalent) contamination in the exhaust and 

background HC sampling systems within 8 hours 

before the start of the first test drive cycle for each 

individual vehicle tested as described in 40 CFR 

1065.520(g).¶

¶

§1066.425 Engine starting and restarting.¶

(a) Start the vehicle’s engine as follows:¶

(1) At the beginning of the test cycle, start the engine 

according to the procedure you describe in your 

owners manual.

Deleted: During idle operation, you mayIf you 

don’t recommend such a cranking procedure, stop 

cranking after 10 seconds, wait for 10 seconds, then 

start cranking gain for up to 10 seconds. You may 

repeat this for up to three start attempts. Shut off 

sampling systems and either turn the CVS off, or 

disconnect the exhaust tube from the tailpipe during ... [6]

Deleted: (6) Verify that there are no significant ... [7]

Deleted: 8

Deleted: 9

Deleted: switch

Deleted: only 

Deleted: is performed by changing

Deleted: span

Deleted: During a test you may not switch the ... [8]

Deleted: 10

Deleted: NIST-traceable 

Deleted: Span

Deleted: on a 

Deleted: basis 

Deleted: one (C1).

Deleted: 

Deleted: ,

Deleted: 

Deleted: . Span

Deleted: analyzers

Deleted: 11

Deleted: and

Deleted: , you may

Deleted: 12

Deleted: 13

Deleted: c) Operate vehicles during testing as ... [9]

Deleted: (1) Where we do not give specific ... [10]
§1066.430 Performing emission tests.

(a) See the standard-setting part for drive schedules. These are defined by a smooth fit of a

specified speed vs. time sequence. 

(b) The driver must attempt to follow the target schedule as closely as possible, consistent with 

the specifications in paragraph (b) of this section. Instantaneous speeds must stay within the 

following tolerances: 

(1) The upper limit is 2.0 mph higher than the highest point on the trace within 1.0 s of the given 

point in time. 

(2) The lower limit is 2.0 mph lower than the lowest point on the trace within 1.0 s of the given 

time. 

(3) The same limits apply for vehicle operation without exhaust measurements, such as vehicle 

preconditioning and warm-up, except that the upper and lower limits for speed values are ±4.0 

mph. In addition, up to three occurrences of speed variations greater than the tolerance are 

acceptable for vehicle operation in which no exhaust emission standards apply, as long as they 

occur for less than 15 seconds on any occasion and are clearly documented as to the time and 

speed at that point of the driving schedule.

(4) Void the test if you do not maintain speed values as specified in this paragraph (b), except as 

allowed by this paragraph (b)(4). Speed variations (such as may occur during gear changes or 

braking spikes) may occur as follows, provided that such variations are clearly documented, 

including the time and speed values and the reason for the deviation: 

(i) Speed variations greater than the specified limits are acceptable for up to 2.0 seconds on any 

occasion. 

(ii) For vehicles that are not able to maintain acceleration as specified in §1066.420(e)(5), do not 

count the insufficient acceleration as being outside the specified limits. 

(5) We may approve an alternate test cycle and cycle-validation criteria for vehicles that do not 

have enough power to follow the specified driving trace. The alternate driving specifications 

must be based on making best efforts to maintain acceleration and speed to follow the specified 

test cycle. We must approve these alternate driving specifications before you perform this 

testing.

(c) Figure 1 and Figure 2 of this section show the range of acceptable speed tolerances for typical 

points during testing. Figure 1 of this section is typical of portions of the speed curve that are 

increasing or decreasing throughout the 2-second time interval. Figure 2 of this section is typical 

of portions of the speed curve that include a maximum or minimum value. 

Deleted: (ii) For vehicles with manual 

transmission, operate at idle with the transmission in 

gear with the clutch disengaged, except that you may 

shift to “Neutral” with the clutch disengaged for the 

first idle period and for any idle period longer than 

one minute. If you put the vehicle in “Neutral” 

during idle, you must shift to first gear with the 

clutch disengaged at least 5 seconds before the end 

of the idle period.¶

(6) Decelerate without changing gears, using the 

brakes or accelerator pedal as necessary to maintain 

the desired speed. Keep the clutch engaged on 

manual transmission vehicles and do not change 

gears after the end of the acceleration event. 

Depress manual transmission clutches when the 

speed drops below 6.7 m/s (15 mph), when engine 

roughness is evident, or when engine stalling is 

imminent.¶

(7) For test vehicles equipped with manual 

transmissions, shift gears in a way that represents 

reasonable shift patterns for in-use operation, 

considering vehicle speed, engine speed, and any 

other relevant variables. You may recommend a 

shift schedule in your owners manual that differs 

from your shift schedule during testing as long as 

you include both shift schedules in your application 

for certification. In this case, we may use the shift 

schedule you describe in your owners manual.¶

(d

Deleted: trace drawn through the

Deleted: e

Deleted: 1

Deleted: m/s (2 

Deleted: )

Deleted: 1

Deleted: m/s (2 

Deleted: )

Deleted: 2

Deleted: m/s (±4 

Deleted: ).

Deleted: without exhaust measurements

Deleted: e

Deleted: paragraph (c)(5) of this section,

Deleted: (f
Figure 1 of §1066.430—Example of the allowable ranges for the driver’s trace. 

Figure 2 of §1066.430—Example of the allowable ranges for the driver’s trace. 

1.0 s

Time

S

peed

Allowable

Range

2.0 mph

2.0 mph

1.0 s

1.0 s

Time

S

peed

Allowable

Range

2.0 mph

2.0 mph

1.0 s
(d) Start testing as follows: 

(1) If a vehicle is already running and warmed up, and starting is not part of the test cycle, 

operate the vehicle as follows: 

(i) For transient test cycles, control vehicle speeds to follow a drive schedule consisting of a 

series of idles, accelerations, cruises, and decelerations. 

(ii) For cruise test cycles, control the vehicle operation to match the speed of the first interval of 

the test cycle. Follow the instructions in the standard-setting part to determine how long to 

stabilize the vehicle during each interval, how long to sample emissions at each interval, and 

how to transition between intervals. 

(2) If engine starting is part of the test cycle, start recording continuous data, any electronic 

integrating devices, and batch sampling before starting the engine. Initiate the driver’s trace 

when the engine starts.

(e) Perform the following at the end of each test interval, except as specified in subpart I of this 

part:

(1) Shut down the vehicle if it is part of the test cycle or if testing is complete.

(2) Continue to operate all sampling and dilution systems to allow the response times to elapse. 

Then stop all sampling and recording, including background sampling. Finally, stop any 

integrating devices and indicate the end of the duty cycle in the recorded data. 

(f) If testing involves engine shutdown followed by another test interval, start a timer for the 

vehicle soak when the engine shuts down. Turn off cooling fans, close the vehicle hood (if 

applicable), and turn off the CVS or disconnect the exhaust tube from the tailpipe(s) of the 

vehicle unless otherwise instructed in the standard-setting part. If testing is complete, disconnect 

the exhaust tube from the vehicle tailpipe(s) and drive the vehicle from dynamometer.

(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 40 CFR 1065.545. Void any samples that 

did not maintain proportional sampling according to those specifications. 

(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 40 CFR 1065.595. 

(3) As soon as practical after the interval or test cycle is complete, or optionally during the soak 

period if practical, perform the following:

(i) Begin drift check for all continuous gas analyzers as described in paragraph (g)(5) of this 

section and zero and span all batch gas analyzers as soon as practical prior to any batch sample 

analysis. You may perform this batch analyzer zero and span prior to the end of the test cycle or 

interval.

(ii) Analyze any conventional gaseous batch samples (HC, CH4, CO, NOx, and CO2) no later 

than 30 minutes after an interval or test cycle is complete, or during the soak period if practical. 

Analyze background samples no later than 60 minutes after the test cycle is complete.

(iii) Analyze nonconventional gaseous batch samples (including background), such as NMHCE, 

N2O, or NMOG sampling with ethanol, as soon as practicable using good engineering judgment. 

(4) Range validation. If an analyzer operated above 100 % of its range at any time during the 

test, perform the following steps:

(i) 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.

Deleted: g

Deleted: phase

Deleted: phase

Deleted: phase

Deleted: phases

Deleted: initiate

Deleted: logging, sampling of exhaust gases, and 

Deleted: measured values 

Deleted: .(h) At

Deleted: continue

Deleted: the recording of 

Deleted: samples

Deleted: i) Shut down the vehicle if it is part of the 

test cycle or if testing is complete.¶

(j

Deleted: phase

Deleted: k

Deleted: :(

Deleted: Drift

Deleted: 6

Deleted: the

Deleted: ¶

(ii) Analyze any conventional gaseous batch samples

no later than 30 minutes after a test phase is 

complete, or during the soak period if practical.

Deleted: ,

Deleted: NMHCEsampling

Deleted: iii) Analyze background samples no later 

than 60 minutes after the test cycle is complete.

Deleted: (4
(ii) 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 consistently operates at less than 100 % of its range.

Keep records of any tests where the analyzer exceeds its range. We may consider these results to 

be failures, consistent with good engineering judgment.

(5) 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 that analyzer drift does not exceed 2.0 % of the analyzer full scale. 

(h) [Reserved] 

(i) Measure and record ambient pressure. Measure and record ambient temperature continuously 

to verify that it remains within the temperature range specified in §1066.425(c)(1) throughout the 

test. Also measure humidity if required, such as for correcting NOx emissions, or meeting the 

requirements of §1066.425(d).

(j) For vehicles at or below 14,000 pounds GVWR, determine overall driver accuracy using 

Energy Based Drive Metrics as follows:

(1) Compare the following drive cycle metrics, based on measured vehicle speeds, to a reference 

value based on the target cycle that would have been generated by driving exactly to the target 

trace as described in SAE J2951 (incorporated by reference in §1066.1010).

(i) Determine the Energy Economy Rating as described in Section 5.4 of SAE J2951. 

(ii) Determine the Absolute Speed Change Rating as described in Section 5.5 of SAE J2951.

(iii) Determine the Inertia Work Rating as described in Section 5.6 of SAE J2951.

(iv) Determine the phase weighted composite Energy Based Drive Metrics for the criteria 

specified in paragraphs (i), (ii), and (iii) of this section as described in Section 5.7 of SAE J2951.

(2) The standard-setting part may require you to provide to us 10 Hz data to characterize both 

target and actual values for cycle energy. Calculate target values based on the vehicles speeds 

from the specified test cycle.

Deleted: and correct for

Deleted: as described in 40 CFR 1065.550

Deleted: l

Deleted: m

Deleted: temperature and 

Deleted: Also measure humidity, as required, 

such as for correcting NOx emissions. For testing 

vehicles with the following engines, you must

Deleted: 420(b

Deleted: :

Deleted: (1) Air-cooled engines.¶

(2) Engines equipped with emission control devices 

that sense and respond to ambient temperature.¶

(3) Any other engine for which good engineering 

judgment indicates that this is necessary to remain 

consistent with 40 CFR 1065.10(c)(1).¶

Subpart F—Hybrids¶

Deleted: 6.1.2

Deleted: Calculate

Deleted: , IR, using the both the sums of the 

incremental driven and the target inertia work as 

described in Eq. 1066.430-1.¶

  

 

i i ii

i i

ID D IT T

i=1 i=1

IT T

i=1

n n

n

F D FD

IR

F D





    

 

  



 



¶

Eq. 1066.430-1¶

¶

Where:¶

i FID = the driven inertial force over an interval 

i, as described by Equation 18 of SAE J2951.¶

i FIT = the target inertial force over an interval j, 

as described by Equation 19 of SAE J2951.¶

Di D = the incremental driven distance over an 

interval i, as described by Equation 12 of SAE 

J2951.¶

Ti D = the incremental target distance over an 

interval j, as described by Equation 13 of SAE 

J2951.

Comment [CAL4]: Equation updated. 

Comment [CAL5]: Updated. 

Comment [CAL6]: Updated. 
Subpart F—Hybrids and Electric Vehicles

§1066.501 Overview. 

For HEV, PHEV, and EV; use the following procedures:

(a) Correct the results for Net Energy Change of the RESS as follows: 

(1) For vehicles at or below 14,000 pounds GVWR, follow SAE J1711 (incorporated by 

reference in §1066.1010) except as noted in this paragraph (a). Use ±1 % of reading or ±0.3 % 

of full scale, whichever is greater, in place of the current measurement accuracy in Section 4.2a

of SAE J1711. For test elements that are not specific for hybrid vehicles, if J1711 differs from 

the standard setting part then the standard setting part takes precedence.

(2) For vehicles above 14,000 pounds GVWR, follow SAE J2711 (incorporated by reference in 

§1066.1010) for requirements related to charge-sustaining operation.

(3) For PHEV and HEV power analyzers, use an integration frequency of 20 Hz or less.

(4) For pure EVs, irrespective of GVWR, follow SAE J1634 (incorporated by reference in 

§1066.1010). 

(b) This paragraph (b) applies for vehicles that include an engine-powered generator or other 

auxiliary power unit that provides motive power. For example, this would include a vehicle that 

has a small gasoline engine that generates electricity to charge batteries. Unless we approve 

otherwise, measure emissions for all test cycles when such an engine is operating. For each test 

cycle for which emissions are not measured, you must validate that such engines are not 

operating at any time during the test cycle.

Deleted: To correct fuel economy or emission

Deleted: pure electric vehicle (

Deleted: )

Deleted: ,

Deleted: , use the proceduresspecified for chargesustaining operation in SAE 

Deleted: 710).

Deleted: 3
Subpart G—Calculations 

§1066.601 Overview. 

(a) This subpart describes calculations used to determine emission rates. See the standard setting 

part and the other provisions of this part to determine which equations apply for your testing. 

This subpart describes how to– 

(1) Use the signals recorded before, during, and after an emission test to calculate distancespecific 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 weighing of a PM filter or multiple readings from a bag 

sample. Although you may use an average of multiple measurements from a single test, you may 

not use test results from multiple emission tests to report emissions. We allow weighted means 

where appropriate, such as for sampling onto a PM filter over the FTP. You may discard 

statistical outliers, but you must report all results. 

§1066.610 Mass-based and molar-based exhaust emission calculations. 

(a) Calculate your total mass of emissions over a test cycle as specified in paragraph (c) of this 

section or in 40 CFR part 1065, subpart G, as applicable. 

(b) For composite emission calculations over multiple test intervals and corresponding weighting 

factors, see the standard-setting part. 

(c) To calculate total mass emissions, multiply a concentration by its respective flow and density

as specified in Eq. 1066.610-1. Before calculating mass emissions as specified in paragraph (d) 

and (e) of this section, perform the following sequence of preliminary calculations to correct 

recorded concentration measurements:

(1) For vehicles above 14,000 pounds GVWR, correct all THC and CH4 concentrations for initial 

contamination as described in 40 CFR 1065.660(a), including continuous readings, sample bag 

readings, and dilution air background readings. This correction is optional for vehicles at or 

below 14,000 pounds GVWR.

(2) Correct all concentrations measured on a “dry” basis to a “wet” basis, including dilution air 

background concentrations.

(3) Calculate all NMHC and CH4 concentrations, including dilution air background 

concentrations, as described in 40 CFR 1065.660.

(4) For vehicles at or below 14,000 pounds GVWR, calculate HC concentrations, including 

dilution air background concentrations, as described in this section and §1066.665 for NMOG. 

For emission testing of vehicles above 14,000 pounds GVWR, with fuels that contain 25% or 

more oxygenated compounds by volume, calculate HC concentrations, including dilution air 

background concentrations, as described in 40 CFR part 1065, subpart I, for THCE and NMHCE.

(5) Correct all NOx emission values for test cell ambient air humidity as described in §1066.630.

(6) Correct all gaseous concentrations for dilution air background as described in §1066.620.

(7) Correct all PM filter masses for sample media buoyancy as described in 40 CFR 1065.690.

(d) Calculate the emission mass of each gaseous pollutant using the following equation:

m V xc [emission] mix [emission] [emission]    

Deleted: You

Deleted: .

Deleted: 86.144 or 40 CFR 

Deleted: phases

Deleted: before

Deleted: of this section
 Eq. 1066.610-1

Where:

m[emission] = emission mass over the test interval.

Vmix = total dilute exhaust volume over the test interval at standard reference conditions, 

corrected for any volume removed for emission sampling and the addition of secondary dilution 

air (if applicable).

ρ[emission] = density of the appropriate chemical species as given in §1066.1005(f).

x[emission] = measured emission concentration in the sample, after dry-to-wet and background 

corrections.

c = 10-2 for emission concentrations % and 10-6 for emission concentrations in ppm.

Example:

Vmix = 170.878 m3 (from paragraph (f) of this section) 

ρNOx = 1913 g/m3

xNOx = 0.9721 ppm

c = 10-6

6

NOx m 170.878 1913 0.9721 10 0.3177 g    

(e) The calculation of PM is dependent on how many PM filters are used (for example as 

described in §1066.822(b)), as follows:

(1) Except as specified in paragraphs (e)(2) and (3) of this section, calculate mPM using the 

following equation:

  mix

PM PMfil PMbkgnd

PMstd sdastd

V m mm V V

        

 Eq. 1066.610-2

Where:

mPM = mass of particulate matter emissions over the test interval, as described in 

§1066.820(b)(1), (2), and (3).

Vmix = total dilute exhaust volume over the test interval at standard reference conditions , 

corrected for any volume removed for emissions sampling and the addition of secondary dilution 

air (if applicable).

Vsdastd = total volume of secondary dilution air flow sampled through the filter over the test phase

at standard temperature and pressure.

mPMfil = mass of particulate matter emissions on the filter over the test interval.

mPMbkgnd = mass of particulate matter on the background filter.

Example:

Vmix = 170.878 m3 (from paragraph (f) of this section)

VPMstd = 0.925 m3 (from paragraph (f) of this section)

Vsdastd = 0.527 m3 (from paragraph (f) of this section)

mPMfil = 0.0000045 g

mPMbkgnd = 0.0000014 g

PM   170.878 0.0000045 0.0000014 0.00133 g 0.925 0.527 m          
(2) If you sample PM onto a single filter as described in §1066.820(b)(4), calculate mPM using 

the following equation:

        mix

PM PMfil PMbkgnd

ct-PMstd ct-sdastd ht-PMstd ht-sdastd

s-PMstd s-sdastd 0.43 0.57

V m mm VV VV

V V

   

      

 Eq. 1066.610-3

Where:

mPM = mass of particulate matter emissions over the entire FTP as sampled according to 

§1066.820(b)(4).

Vmix = total dilute exhaust volume over the test interval at standard reference conditions, 

corrected for any volume removed for emissions sampling and the addition of secondary dilution 

air (if applicable).

V[interval]-PMstd = total volume of dilute exhaust sampled through the filter over the test interval (ct 

= cold transient, s = stabilized, ht = hot transient) at standard reference conditions.

V[interval]-sdastd = total volume of secondary dilution air sampled through the filter over the test 

interval (ct = cold transient, s = stabilized, ht = hot transient) at standard reference conditions.

mPMfil = mass of particulate matter emissions on the filter over the test interval.

mPMbkgnd = mass of particulate matter on the background filter.

Example:

Vmix = 633.691 m3

Vct-PMstd = 0.925 m3

Vct-sdastd = 0.527 m3

Vs-PMstd = 1.967 m3

Vs-sdastd = 1.121 m3

Vht-PMstd = 1.122 m3

Vht-sdastd = 0.639 m3

mPMfil = 0.0000106 g

mPMbkgnd = 0.0000014 g

      PM   633.691 0.0000106 0.0000014

0.925 0.527 1.122 0.639

1.967 1.121

0.43 0.57

m

   

       

mPM = 0.00222 g

(3) If you sample PM onto a single filter as described in §1066.820(b)(5), calculate mPM using 

the following equation:

        mix

PM PMfil PMbkgnd

ct-PMstd ct-sdastd cs-PMstd cs-sdastd ht-PMstd ht-sdastd hs-PMstd hs-sdastd

0.43 0.57

V m m m VV VV VV VV

   

         

 Eq. 1066.610-4
Where:

mPM = mass of particulate matter emissions over the entire FTP as sampled according to 

§1066.820(b)(5).

Vmix = total dilute exhaust volume over the test interval at standard reference conditions, 

corrected for any volume removed for emissions sampling and the addition of secondary dilution 

air (if applicable).

V[interval]-PMstd = total volume of dilute exhaust sampled through the filter over the test interval (ct 

= cold transient, cs = cold stabilized, ht = hot transient, hs = hot stabilized) at standard reference 

conditions.

V[interval]-sdastd = total volume of secondary dilution air sampled through the filter over the test 

interval (ct = cold transient, cs = cold stabilized, ht = hot transient, hs = hot stabilized) at 

standard reference conditions.

mPMfil = mass of particulate matter emissions on the filter over the test interval.

mPMbkgnd = mass of particulate matter on the background filter.

Example:

Vmix = 972.121 m3

Vct-PMstd = 0.925 m3

Vct-sdastd = 0.529 m3

Vcs-PMstd = 1.968 m3

Vcs-sdastd = 1.123 m3

Vht-PMstd = 1.122 m3

Vht-sdastd = 0.641 m3

Vhs-PMstd = 1.967 m3

Vhs-sdastd = 1.121 m3

mPMfil = 0.0000229 g

mPMbkgnd = 0.0000014 g

      PM   972.121 0.0000229 0.0000014

0.925 0.529 1.968 1.123 1.122 0.641 1.967 1.121

0.43 0.57

m

   

      

mPM = 0.00401 g

(f) This paragraph (f) describes how to correct flow and flow rates to standard reference 

conditions and provides an example for determining Vmix based on CVS total flow and the 

removal of sample flow from the dilute exhaust gas. Using good engineering judgment, you may 

use predetermined nominal values for removed sample volumes, except for flows used for batch 

sampling.

(1) Correct flow and flow rates to standard reference conditions as needed using the following 

equation:

[flow]act in std

[flow]std

std in

V pT V

p T

   

 Eq. 1066.610-5

Where:

V[flow]std = total volume of flow at the flow meter at standard reference conditions.

V[flow]act = total volume of flow at the flow meter at test conditions.

Deleted: 155
pin = absolute static pressure at the flow meter inlet, measured directly or calculated as the sum 

of atmospheric pressure plus a differential pressure referenced to atmospheric pressure.

Tstd = standard temperature.

pstd = standard pressure.

Tin = average temperature of the dilute exhaust sample at the flow meter inlet.

Example:

VPMact = 1.071 m3

pin = 101.7 kPa

Tstd = 293.15 K

pstd = 101.325 kPa

Tin = 340.5 K

3

PMstd

1.071 101.7 293.15 0.925 m

101.325 340.5

V     

(2) The following example provides a determination of Vmix based on CVS total flow and the 

removal of sample flow from one dilute exhaust gas analyzer and one PM sampling system that 

is utilizing secondary dilution. Note that your Vmix determination may vary from Eq. 1066.610-6 

based on the number of flows that are removed from your dilute exhaust gas and whether your 

PM sampling system is using secondary dilution. For this example, Vmix is governed by the 

following equation:

VV V V V mix CVSstd gasstd PMstd sdastd  

 Eq. 1066.610-6

Where:

VCVSstd = total dilute exhaust volume over the test interval at the flow meter at standard reference 

conditions.

Vgasstd = total volume of sample flow through the gaseous emission bench over the test interval at 

standard reference conditions.

VPMstd = total volume of dilute exhaust sampled through the filter over the test interval at 

standard reference conditions.

Vsdastd = total volume of secondary dilution air flow sampled through the filter over the test 

interval at standard reference conditions.

Example:

Using Eq. 1066.610-5

VCVSstd = 170.451 m3, where VCVSact = 170.721 m3, pin = 101.7 kPa, and Tin = 294.7 K

Using Eq. 1066.610-5

Vgasstd = 0.028 m3, where Vgasact = 0.033 m3, pin = 101.7 kPa, and Tin = 340.5 K

Using Eq. 1066.610-5

VPMstd = 0.925 m3, where VPMact = 1.071 m3, pin = 101.7 kPa, and Tin = 340.5 K

Using Eq. 1066.610-5

Vsdastd = 0.527 m3, where Vsdaact = 0.531 m3, pin = 101.7 kPa, and Tin = 296.3 K

Vmix = 170.451 + 0.028 + 0.925 – 0.527 = 170.878 m3

(g) Total sample volume over a test interval. Calculate total flow, V[flow], for a CVS or exhaust 

gas sampler as follows: 
(1) Varying versus constant flow rates. The calculation methods depend on differentiating 

varying and constant flow, as follows:

(i) We consider the following to be examples of varying flows that require a continuous 

multiplication of concentration times volumetric 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.

(ii) We consider the following to be examples of constant exhaust flows: CVS diluted exhaust 

with a CVS flow meter that has an upstream heat exchanger, an electronic flow control, or both.

(2) Continuous sampling. For continuous sampling, you must frequently record a continuously 

updated flow signal. This recording requirement applies for both varying and constant flow rates.

(i) Varying flow rate. If you continuously sample from a varying exhaust flow rate, calculate 

V[flow] using the following equation:

[flow] i

i 1

N

V Qt    

 Eq. 1066.610-7

Where:

∆t = 1/frecord Eq. 1066.610-8

Example:

N = 505

QCVS1

 = 0.276 m3

/s

QCVS2

 = 0.294 m3

/s

frecord = 1 Hz

Using Eq. 1066.610-8,

t = 1/1 = 1 s

CVS CVS505 V Q     (0.276 0.294 ... ) 1 

VCVS = 170.721 m3

(ii) Constant flow rate. If you continuously sample from a constant exhaust flow rate, use the 

same calculation described in paragraph (g)(2)(i) of this section or calculate the mean flow

recorded over the test interval and treat the mean as a batch sample, as described in paragraph 

(g)(3)(ii) of this section. 

(3) Batch sampling. For batch sampling, calculate total flow by integrating a varying flow rate or 

by determining the mean of a constant flow rate, as follows:

(i) Varying flow rate. If you proportionally collect a batch sample from a varying exhaust flow 

rate, integrate the flow rate over the test interval to determine the total flow from which you 

extracted the proportional sample, as described in paragraph (g)(2)(i) of this section. 

(ii) Constant flow rate. If you batch sample from a constant exhaust flow rate, extract a sample 

at a proportional or constant flow rate and calculate V[flow] from the flow from which you extract 

the sample by multiplying the mean flow rate by the time of the test interval using the following 

equation: 

V Qt [flow]   

Eq. 1066.610-9
Example:

QCVS

 = 0.338 m3

/s

t = 505 s 

CVS V   0.338 505

VCVS = 170.69 m3

§1066.620 Dilution air background correction.

(a) Correct the emissions in a gaseous sample for background using the following equation:

[emission] [emission]dexh [emission]bkgnd

1 xx x 1

DF

              

 Eq. 1066.620-1

Where:

x[emission]dexh = measured emission concentration in dilute exhaust (after dry-to-wet correction for 

dry measurements).

x[emission]bkgnd = measured emission concentration in the dilution air (after dry-to-wet correction

for dry measurements).

DF = dilution factor determined in paragraph (b) of this section.

Example:

xNOxdexh = 1.08305 ppm

xNOxbkgnd = 0.12456 ppm

DF = 9.14506

NOx

1 1.08305 0.12456 1 0.97211 ppm 9.14506 x                

(b) Determine the dilution factor, DF, over the test interval using the following equation:

 Eq. 1066.620-2

Where:

xCO2 = amount of CO2 measured in the sample over the test interval.

xNMHC = amount of C1-equivalent NMHC measured in the sample over the test interval.

xCH4 = amount of CH4 measured in the sample over the test interval.

xCO = amount of CO measured in the sample over the test interval.

 = atomic hydrogen-to-carbon ratio of the test fuel. You may measure  or use default values 

from Table 1 of 40 CFR 1065.655.

 = atomic oxygen-to-carbon ratio of the test fuel. You may measure  or use default values 

from Table 1 of 40 CFR 1065.655.

Example:

CO2 NMHC CH4 CO

1

1 3.76 1 ( ) 2 42

DF

x x xx                     
xCO2 = 1.456 % = 0.01456

xNMHC = 0.84 ppm = 0.00000084

xCH4 = 0.26 ppm = 0.00000026

xCO = 80.4 ppm = 0.0000804

 = 1.92

 = 0.03

 

1 9.14506

1.92 1.92 0.03 1 3.76 1 0.01456 0.00000084 0.00000026 0.0000804

2 42

DF                      

(c) Determine the dilution factor, DF, over the test interval for partial-flow dilution sample 

systems using the following equation:

dexhstd

exhstd

V DF

V 

 Eq. 1066.620-3

Where:

Vdexhstd = total dilute exhaust volume sampled over the test interval at standard reference 

conditions.

Vexhstd = total exhaust volume sampled from the vehicle at standard reference conditions.

Example:

Vdexhstd = 170.9 m3

Vexhstd = 15.9 m3

170.9 11.1

15.4

DF  

(d) Determine the time-weighted dilution factor, DFw, over the duty cycle using the following 

equation:

i

i 1

w

i

i 1 i

1

N

N

t

DF

t

DF













 Eq. 1066.620-4

Where:

N = number of test intervals.

i = test interval number

t = duration of the test interval.

DF = dilution factor over the test interval.

Example:

N = 3

DF1 = 14.40

t1 = 505 s

DF2 = 24.48

t2 = 867 s

DF3 = 17.28

Deleted: that measure PM 

Deleted: PM

Deleted: through the filter 

Deleted: PM
t3 = 505 s

w

505 867 505 18.82

111 505 867 505

14.40 24.48 17.28

DF                   

§1066.630 NOx intake-air humidity correction.

See the standard-setting part to determine if you may correct NOx emissions for the effects of 

intake-air humidity. Correct NOx emissions for intake-air humidity as described in this section. 

See §1066.610(c)(1) for the proper sequence for applying the NOx intake-air humidity correction.

(a) For vehicles at or below 14,000 pounds GVWR, apply a correction for any reciprocating 

engines for the following test cycles:

(1) Calculate a humidity correction using a time-weighted mean value for ambient humidity over

the test interval. Calculate absolute ambient humidity in grams H2O vapor per kilogram of dry 

air using the following equation:

  H2O d

air atmos d

1000 % 0.01

% 0.01

M p RH H

M p p RH

      

 Eq. 1066.630-1

Where:

MH2O = molar mass of H2O.

pd = saturated vapor pressure at the ambient dry bulb temperature.

RH% = relative humidity of ambient air

Mair = molar mass of air.

patmos = atmospheric pressure.

Example:

MH2O = 18.01528 g/mol

pd = 2.93 kPa

RH % = 37.5 %

Mair = 28.96559 g/mol

patmos = 96.71 kPa

  2

1000 18.01528 2.93 37.5 0.01 7.14741 g H O vapor kg dry air 28.96559 96.71 2.93 37.5 0.01

H      

(2) Use the following equation to correct measured concentrations to a reference condition of 

10.71 grams H2O vapor per kilogram of dry air for the FTP, US06, LA-92, SC03, and HFET test 

cycles:

 

s

NOxdexhcor NOxdexh 1 0.0329 10.71

H x x H    

 Eq. 1066.630-2

Where:

xNOxdexh = measured dilute NOx emissions.

Hs = humidity scale. Set = 1 for FTP, US06, LA-92, and HFET test cycles. Set = 0.8825 for the 

SC03 test cycle.

H = ambient humidity, from paragraph (a)(1) of this section.

Deleted: , in g/mol

Deleted: , in kPa

Deleted: , in %.

Deleted: , in g/mol

Deleted: , in kPa

Deleted: absolute
Example:

H = 7.14741 g H2O vapor/kg dry air 

xNOxdexh = 1.21 ppm

  NOxdexhcor

1 1.21 1.08305 ppm 1 0.0329 7.14741 10.71 x    

(b) For vehicles above 14,000 pounds GVWR, apply correction factors as described in 40 CFR 

1065.670.

§1066.640 Removed water correction.

Correct for removed water if water removal occurs upstream of a concentration measurement

and downstream of a flow meter used to determine mass emissions over a test interval. Perform 

this correction based on the amount of water at the concentration measurement and on the 

amount of water at the flow meter.

§1066.650 Flow meter calibration calculations.

This section describes how to calibrate various flow meters based on mass flow rates. Calibrate 

your flow meter according to 40 CFR 1065.640 instead if you calculate emissions based on 

molar flow rates.

(a) PDP calibration calculations. Perform the following steps to calibrate a PDP flow meter:

(1) Calculate PDP volume pumped per revolution, Vrev, for each restrictor position from the 

mean values determined in §1066.140:

ref in std

rev

nPDP in std

QTp V

f p T

    



Eq. 1066.650-1

Where:

Qref

 = mean flow rate of the reference flow meter.

Tin = mean temperature at the PDP inlet.

pstd = standard pressure = 101.325 kPa.

nPDP f = mean PDP speed.

in p = mean static absolute pressure at the PDP inlet.

Tstd = standard temperature = 293.15 K.

Example:

Qref

 = 0.1651 m3

/s

Tin = 299.5 K

pstd = 101.325 kPa 

nPDP f = 1205.1 r/min = 20.085 r/s

in p = 98.290 kPa
Tstd = 293.15 K

0.1651 299.5 101.3

20.085 98.290 293.15

Vrev

    

Vrev = 0.00866 m3/r

(2) Calculate a PDP slip correction factor, Ks for each restrictor position from the mean values 

determined in §1066.140:

out in

s

nPDP out

1 p p K

f p

  

Eq. 1066.650-2

Where:

nPDP f = mean PDP speed.

out p = mean static absolute pressure at the PDP outlet.

in p = mean static absolute pressure at the PDP inlet.

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 Vrev, versus PDP Ks, by calculating slope, a1, and 

intercept, a0, as described in 40 CFR 1065.602.

(4) Repeat the procedure in paragraphs (a)(1) through (3) of this section for every speed that you 

run your PDP.

(5) The following example illustrates a range of typical values for different PDP speeds:

Table 1 of §1066.650–

Example of PDP calibration data

nPDP f

(r/s)

a1 

(m3/s)

a0 

(m3/r)

12.6 0.841 0.056

16.5 0.831 -0.013

20.9 0.809 0.028

23.4 0.788 -0.061

(6) For each speed at which you operate the PDP, use the appropriate regression equation from 

this paragraph (a) to calculate flow rate during emission testing as described in §1066.652.

(b) SSV calibration. The equations governing SSV flow assume one-dimensional isentropic 

inviscid flow of an ideal gas, except that the equations can account for compressible flow. 

Paragraph (b)(2)(iv) of this section describes other assumptions that may apply. If good 

engineering judgment dictates that you account for gas compressibility, you may either use an 

Comment [CAL7]: Not italic. 

Comment [CAL8]: Not italic. 
appropriate equation of state to determine values of Z as a function of measured pressure and 

temperature, 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 pressure and 

temperature, or you may develop your own calibration equations based on good engineering 

judgment.

(1) Calculate volumetric flow rate, Q , as follows

t in std

d f

std mix in

ARp T Q CC

p Z M RT

     



Eq. 1066.650-3

Where:

Cd = discharge coefficient, as determined in paragraph (b)(2)(i) of this section.

Cf = flow coefficient, as determined in paragraph (b)(2)(ii) of this section.

At = cross-sectional area at the venturi throat.

R = molar gas constant.

pin = static absolute pressure at the venturi inlet.

Tstd = standard temperature.

pstd = standard pressure.

Z = compressibility factor.

Mmix = molar mass of gas mixture.

Tin = absolute temperature at the venturi inlet.

(2) Perform the following steps to calibrate an SSV flow meter:

(i) Using the data collected in §1066.140, calculate Cd for each flow rate using the following 

equation:

std mix in

d ref

f t in std

p Z M RT

C Q C ARp T

       



Eq. 1066.650-4

Where: 

Qref

 = measured volumetric flow rate from the reference flow meter.

(ii) Use the following equation to calculate Cf for each flow rate:

 

   

1

2

1

2

f 4

2 1

1

r

C

r









 





      

   

Eq. 1066.650-5

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 (b)(2)(iii) of this section.

 = ratio of venturi throat diameter to inlet diameter.

Deleted: 
(iii) Calculate r using the following equation:

in

1 p r p

  

Eq. 1066.650-6

Where:

Δp = differential static pressure, calculated as venturi inlet pressure minus venturi throat pressure.

(iv) You may apply any of the following simplifying assumptions or develop other values as 

appropriate for your test configuration, consistent with good engineering judgment:

(A) For raw exhaust, diluted exhaust, and dilution air, you may assume that the gas mixture is 

incompressible and therefore behaves as an ideal gas (Z=1).

(B) For raw exhaust, you may assume =1.385.

(C) For diluted exhaust and dilution air, you may assume =1.399.

(D) For diluted exhaust and dilution air, you may assume Mmix is a function only of the amount 

of water in the dilution air or calibration air, xH2O, as follows:

  mix air H2O H O H2O 2 M     M x Mx 1

Eq. 1066.650-7

Where:

Mair = 28.96559 g/mol

xH2O = amount of H2O in the dilution air, determined as described in 40 CFR 1065.645.

MH2O = 18.01528 g/mol

Example:

xH2O = 0.0169 mol/mol

Mmix     28.96559 1 0.0169 18.01528 0.0169  

Mmix = 28.7805 g/mol

(E) For diluted exhaust and dilution air, you may assume a constant molar mass of the mixture, 

Mmix, for all calibration and all testing if you control the amount of water in calibration air and in 

dilution air, as shown in the following table:

Deleted: 4

Deleted: 0

Comment [CAL9]: Example problem updated. 

Deleted: 789
Table 2 of §1066.650–

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

< 0 28.96559 < 18

0 28.89263 < 21

5 28.86148 < 22

10 28.81911 < 24

15 28.76224 < 26

20 28.68685 -8 to 28

25 28.58806 12 to 31

30 28.46005 23 to 34

a

The specified ranges are valid for all calibration and emission testing over the 

atmospheric pressure range (80.000 to 103.325) kPa.

(v) The following example illustrates the use of the governing equations to calculate Cd of an 

SSV flow meter at one reference flow meter value:

Example:

Qref

 = 2.395 m3

/s

Z = 1

Mmix = 28.7805 g/mol = 0.0287805 kg/mol

R = 8.314472 J/(mol·K) = 8.314472 (m2·kg)/(s2·mol·K)

Tin = 298.15 K

At = 0.01824 m2

pin = 99.132 kPa = 99132 Pa = 99132 kg/(m·s2)

 = 1.399

 = 0.8

Δp = 7.653 kPa

2.312 1 0.922

99.132 r  

 

   

1.399 1

1.399

2 1.399

1

2

f 4

2 1.399 0.922 1

1.399 1 0.8 0.922

C





          

Cf = 0.472

d

101325 1 0.0287805 8.314472 298.15 2.395

0.472 0.01824 8.314472 99132 293.15

C        

Cd = 0.985

(vi) Calculate the Reynolds number, Re#, for each reference volumetric flow rate, Qref

 , using the 

throat diameter of the venturi, dt, and the uncorrected air density, . Assume an initial Cd value 

of 0.98 to calculate Qref

 . Because the dynamic viscosity, μ, is needed to compute Re#

, you may 

Deleted: 789

Deleted: 789

Deleted: 2.312

Comment [CAL10]: Example problem updated. 

Comment [CAL11]: Example problem updated. 

Deleted: 274

Comment [CAL12]: Example problem updated. 

Deleted: 1.695
use your own fluid viscosity model to determine μ for your calibration gas (usually air), using 

good engineering judgment. Alternatively, you may use the Sutherland three-coefficient 

viscosity model to approximate μ, as shown in the following sample calculation for Re#:

# ref

t

4 Q Re =

d



 

 

 



Eq. 1066.650-8

Where, using the Sutherland three-coefficient viscosity model: 3

2 in 0

0

0 in

T TS

T TS  

              

Eq. 1066.650-9

Where:

0 = Sutherland reference viscosity.

T0 = Sutherland reference temperature.

S = Sutherland constant.

Table 3 of §1065.640–

Sutherland three-coefficient viscosity model parameters

Gasa μ0 T0 S

Temp range 

within ±2 % 

errorb

Pressure 

limitb

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.

b

The model results are valid only for ambient conditions in the specified 

ranges.

Example:

μ0 = 1.716·10-5 kg/(m·s)

T0 = 273 K

S = 111 K 3

2 5 298.15 273 111 1.716 10

273 298.15 111                

μ = 1.838·10-5 kg/(m·s)

Tin = 298.15 K

dt = 152.4 mm = 0.1524 m

 = 1.1508 kg/m3

Deleted: 

Comment [CAL13]: Example problem updated. 
#

5

4 1.1508 2.395

3.14159 0.1524 1.838 10

Re = 

 

 

Re# = 1.2531·106

(vii) Calculate ρ using the following equation:

in mix

in

p MW

R T    

Eq. 1066.650-10

Example:

99132 0.0287805

8.314472 298.15    

ρ = 1.1509 kg/m3

(viii) Create an equation for Cd as a function of Re#, using paired values of the two quantities. 

The equation may involve 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 Caa

Re  

Eq. 1066.650-11

(ix) Perform a least-squares regression analysis to determine the best-fit coefficients for the 

equation and calculate the equation’s regression statistics, SEE and r

2

, according to 40 CFR 

1065.602.

(x) If the equation meets the criteria of SEE ≤ (0.5 % · Qrefmax

 ), you may use the equation for the 

corresponding range of Re#, as described in §1066.652.

(xi) If the equation does not meet the specified statistical criteria, you may use good engineering 

judgment to omit calibration data points; however, you must use at least seven calibration data 

points to demonstrate that you meet the criteria. For example, this may involve narrowing the 

range of flow rates for a better curve fit.

(xii) Take corrective action if the equation does not meet the specified statistical criteria even 

after omitting calibration data points. 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 calibration process, we recommend applying tighter tolerances to measurements and allowing 

more time for flows to stabilize.

(xiii) Once you have an equation that meets the specified statistical criteria, you may use the 

equation only for the corresponding range of flow rates.

(c) 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 calibration coefficient, Kv, for each venturi, or calibrate 

each combination of venturis as one venturi by determining Kv for the system.

(1) To determine Kv for a single venturi or a combination of venturis, perform the following 

steps:

(i) Calculate an individual Kv for each calibration set point for each restrictor position using the 

following equation:

Comment [CAL14]: Example problem updated. 

Deleted: 8

Deleted: quantitites

Deleted: vii

Deleted: §

Deleted: i

Deleted: and r

2 ≥ 0.995

Deleted: to determine Cd for emission tests

Deleted: 5

Deleted: 4
refstd in

v

in

Q T K =

p

 

Eq. 1066.650-12

Where:

Qrefstd

 = mean flow rate from the reference flow meter, at standard reference conditions.

Tin = mean temperature at the venturi inlet.

in p = mean static absolute pressure at the venturi inlet.

(ii) Calculate the mean and standard deviation of all the Kv values (see 40 CFR 1065.602). 

Verify choked flow by plotting Kv as a function of in p .Kv will have a relatively constant value

for choked flow; as vacuum pressure increases, the venturi will become unchoked and Kv will 

decrease. Paragraphs (c)(1)(iii) through (viii) of this section describe how to verify your range of 

choked flow.

(iii) If the standard deviation of all the Kv values is less than or equal to 0.3 % of the mean Kv, 

use the mean Kv in Eq. 1066.652-7, and use the CFV only up to the highest venturi pressure ratio,

r, measured during calibration using the following equation:

CFV

in

1 p r p

  

Eq. 1066.650-13

Where:

pCFV = differential static pressure; venturi inlet minus venturi outlet.

(iv) If the standard deviation of all the Kv values exceeds 0.3 % of the mean Kv, omit the Kv value

corresponding to the data point collected at the highest r measured during calibration.

(v) 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.

(vi) If the number of remaining Kv values is seven or greater, recalculate the mean and standard 

deviation of the remaining Kv values.

(vii) If the standard deviation of the remaining Kv values is less than or equal to 0.3 % of the 

mean of the remaining Kv, use that mean Kv in Eq 1066.652-7, and use the CFV values only up 

to the highest r associated with the remaining Kv.

(viii) If the standard deviation of the remaining Kv still exceeds 0.3 % of the mean of the 

remaining Kv values, repeat the steps in paragraph (c)(1)(iv) through (vii) of this section.

(2) During exhaust emission tests, monitor sonic flow in the CFV by monitoring the CFV 

pressure ratio. Based on the calibration data selected to meet the criteria for paragraphs 

(c)(1)(iv) and (vii) of this section, in which Kv is constant, select the data values associated with 

the calibration point with the lowest absolute venturi inlet pressure to determine the r limit. 

Calculate r during the exhaust emission test using Eq. 1066.650-8 to demonstrate that the value 

of r during all emission tests is less than or equal to the r limit derived from the CFV calibration 

data.
§1066.652 PDP, SSV, and CFV flow rate calculations.

This section describes the equations for calculating flow rates from various flow meters. After 

you calibrate a flow meter according to §1066.650, use the calculations described in this section

to calculate flow during an emission test. Calculate flow according to 40 CFR 1065.642 instead 

if you calculate emissions based on molar flow rates.

(a) PDP volumetric 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 §1066.650(a), to 

calculate volumetric flow rate, Q as follows:

rev std in

nPDP

in std

VTp Q f T p    



Eq. 1066.652-1

Where:

fnPDP = pump speed.

Vrev = PDP volume pumped per revolution.

Tstd = standard temperature = 293.15 K.

pin = static absolute pressure at the PDP inlet.

Tin = pump inlet absolute temperature.

pstd = standard pressure= 101.325 kPa.

1 out in

rev 0

nPDP out

a p p V a

f p

  

Eq. 1066.652-2

pout = static absolute pressure at the PDP outlet.

Example:

a1 = 50.43 m3/min = 0.8405 m3/s

fnPDP = 755.0 r/min = 12.58 r/s

pout = 99.950 kPa

pin = 98.575 kPa 

a0 = 0.056 m3/r

Tin = 323.5 K

Using Eq. 1066.652-2,

rev

0.8405 99.950 98.575 0.056

12.58 99.950

V   

Vrev = 0.063 m3/r

0.06383 293.15 98.575 12.58

323.5 101.3 Q     



Q = 0.7079 m3

/s

(b) SSV volumetric flow rate. Calculate SSV volumetric flow rate during an emission test, Q , 

as follows: 

t in std

d f

std mix in

ARp T Q CC

p Z M RT

     



Comment [CAL15]: Equation updated. 

Deleted: pout = static absolute pressure at the PDP 

outlet.¶

Comment [CAL16]: Equation updated. 
Eq. 1066.652-3

Where:

Cd = discharge coefficient, as determined based on the Cd versus Re# equation in 

§1066.650(b)(2)(vii).

Cf = flow coefficient, as determined in §1066.650(b)(2)(ii).

At = venturi throat cross-sectional area.

R = molar gas constant.

pin = static absolute pressure at the venturi inlet.

Tstd = standard temperature.

pstd = standard pressure.

Z = compressibility factor.

Mmix = molar mass of gas mixture.

Tin = absolute temperature at the venturi inlet.

Example: 

Cd = 0.890

Cf = 0.472

At = 0.01824 m2

R = 8.314472 J/(mol·K) = 8.314472 (m2·kg)/(s2·mol·K)

pin = 98.496 kPa

Tstd = 293.15 K

pstd = 101.325 kPa

Z = 1

Mmix = 28.7789 g/mol = 0.0287789 kg/mol 

Tin = 296.85 K

0.01824 8.314472 98.496 293.15 0.89 0.472

101.325 1 0.0287805 8.314472 296.85 Q       



Q = 2.155 m3

/s

(c) CFV volumetric 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 calibration coefficient, Kv, for each venturi, calculate the individual 

volumetric flow rates through each venturi and sum all their flow rates to determine Q . If you 

use multiple venturis and you calibrated each combination of venturis, calculate Q using the Kv

that was determined for that combination of venturis.

(1) To calculate volumetric flow rate through one venturi or a combination of venturis, use the 

mean Kv you determined according to §1066.650(c) and calculate the appropriate volumetric

flow rate, Q , during an emission test as follows:

v in

in

K p Q = T 

Eq. 1066.652-7

Where:

Q = air flow rate of flow meter, in m3

/s.

Deleted: i

Deleted: 

Deleted: 274

Comment [CAL17]: Example problem updated. 

Deleted: 1.252
Kv = flow meter calibration coefficient, in m

3

·K1/2/(kPa·s).

Tin = temperature at the venturi inlet, in K.

pin = absolute static pressure at the venturi inlet, in kPa.

Example: Kv = 0.074954 m

3

·K1/2/(kPa·s)

pin = 99.654 kPa Tin = 353.15 K

0.074954 99.654

353.15

Q





Q = 0.39748 m

3

/s

(2) [Reserved] Deleted: 

]
§1066.665 NMOG determination.

For vehicles subject to an NMOG standard, determine NMOG as described in paragraph (a) of 

this section. Except as specified in the standard-setting part, you may alternatively calculate 

NMOG results based on measured NMHC emissions as described in paragraphs (c) through (f) 

of this section.

(a) Determine NMOG by independently measuring alcohols and carbonyls as described in 40 

CFR 1065.805 and 1065.845. Use good engineering judgment to determine which alcohols and 

carbonyls you need to measure. This would typically require you to measure all alcohols and 

carbonyls that you expect to contribute 1% or more of total NMOG emissions. Calculate NMOG

with the following equation, using density values specified in §1066.1005(f):

OHCi

NMOG NMHC NMHC OHCi[THC-FID] OHCi

1 1 OHCi

N N

i i

m m m RF m    

     

Eq. 1066.665-1

Where:

mNMOG = the sum of the mass of NMOG in the exhaust.

mNMHC = the mass of NMHC and all oxygenated hydrocarbons (OHCs) in the exhaust, as 

determined using Eq. 1066.610-1. Calculate NMHC mass based on ρNMHC.

ρNMHC = the effective C1-equivalent density of NMHC as specified in §1066.1005(f):.

mOHCi = the mass of oxygenated species i in the exhaust calculated using Eq. 1066.610-1.

ρOCHi = the C1-equivalent density of oxygenated species i.

RFOHCi[THC-FID] = the response factor of a THC-FID to oxygenated species i relative to propane 

on a C1-equivalent basis as determined in 40 CFR 1065.845.

(b) The following example shows how to determine NMOG emissions as described in paragraph 

(a) of this section for (OHC) compounds including ethanol (C2H5OH), methanol (CH3OH), 

acetaldehyde (C2H4O), and formaldehyde (CH2O) as C1-equivalent concentrations:

mNMHC = 0.0125 g

mCH3OH = 0.0002 g

mC2H5OH = 0.0009 g

mHCHO = 0.0001 g

mC2H4O = 0.00005 g

RFCH3OH[THC-FID] = 0.63

RFC2H5OH[THC-FID] = 0.75

RFHCHO[THC-FID] = 0.00

RFC2H4O[THC-FID] = 0.50

ρNMHC-liq = 576.816 g/m3

ρCH3OH = 1332.02 g/m3

ρC2H5OH = 957.559 g/m3

ρHCHO = 1248.21 g/m3

ρC2H4O = 915.658 g/m3

NMOG

0.0002 0.0009 0.63 0.75

1332.02 957.559 0.0125 576.816

0.0001 0.00005 0.00 0.5

1248.21 915.658

0.0002 0.0009 0.0001 0.00005

m

     

  

   



 

Deleted: T

Deleted: 66

Deleted: 2
mNMOG = 0.013273

(c) For ethanol-gasoline blends less than 25 % ethanol by volume, you may calculate NMOG 

emissions from measured NMHC emissions as follows:

(1) For hot-start and hot running test cycles or intervals other than the FTP, you may determine 

NMOG based on the test cycle NMHC emission rate using the following equation:

NMOGh NMHCh e e  1.03

Eq. 1066.665-2

Where:

eNMOGh = mass emission rate of NMOG from the hot running test cycle.

eNMHCh = mass emission rate of NMHC from the hot running test cycle, calculated using ρNMHC-liq.

Example:

eNMHCh = 0.025 g/mi

NMOGh e   0.025 1.03 0.026 g/mi

(2) You may determine weighted composite NMOG for FTP testing based on the weighted 

composite NMHC emission rate and the volume percent of ethanol in the fuel using the 

following equation:

e e VP NMOGcomp NMHCcomp EtOH      1.0302 0.0071

Eq. 1066.665-3

Where:

eNMOGcomp = weighted composite mass emission rate of NMOG from the FTP test interval.

eNMHCcomp = weighted composite mass emission rate of NMHC from the FTP test interval,

calculated using ρNMHC-liq.

VPEtOH = volume percentage of ethanol in the test fuel. Use good engineering judgment to 

determine this value either as specified in 40 CFR 1065.710 or based on blending volumes, 

taking into account any denaturant.

Example:

eNMHCcomp = 0.025 g/mi

VPEtOH = 10.1 %

eNMOGcomp     0.025 1.0302 0.0071 10.1 0.0275 g/mi  

(3) You may determine NMOG for the transient portion of the FTP cold-start test interval for use 

in fuel economy and CREE calculations based on the NMHC emission rate for the test interval 

and the volume percent of ethanol in the fuel using the following equation:

e e VP NMOG-FTPct NMHC-FTPct EtOH      1.0246 0.0079

Eq. 1066.665-4

Where:

eNMOG-FTPct = mass emission rate of NMOG from the transient portion of the FTP cold-start test 

(bag 1).

eNMHC-FTPct = mass emission rate of NMHC from the transient portion of the FTP cold-start test 

(bag 1), calculated using ρNMHC-liq.

VPEtOH = volume percentage of ethanol in the test fuel.

Comment [CAL18]: Equation updated. 

Deleted: ot

Deleted: over

Deleted: ot

Deleted: over

Deleted: ot

Comment [CAL19]: Example updated. 

Deleted: 5

Comment [CAL20]: Example updated. 

Deleted: complete 

Deleted: over

Deleted: 

Deleted: interval

Deleted: over

Deleted: interval
Example:

eNMHC-FTPct = 0.052 g/mi

VPEtOH = 10.1 %

eNMOG-FTPct     0.052 1.0246 0.0079 10.1 0.0574 g/mi  

(4) You may determine NMOG for the stabilized portion of the FTP test interval for either the 

cold-start or hot-start test (bag 2 or bag 4) for use in fuel economy and CREE calculations based 

on the NMHC emission rate for the test interval and the volume percent of ethanol in the fuel 

using the following equation 

e e VP NMOG-FTPcs-hs NMHC-FTPcs-hs EtOH    1.1135 0.001 

Eq. 1066.665-5

Where:

eNMOG-FTPcs-hs = mass emission rate of NMOG from the stabilized portion of the FTP test (bag 2 

or bag 4).

eNMHC-FTPcs-hs = mass emission rate of NMHC from the stabilized portion of the FTP test (bag 2 

or bag 4), calculated using ρNMHC-liq.

VPEtOH = volume percentage of ethanol in the test fuel.

(5) You may determine NMOG for the transient portion of the FTP hot-start test interval for use 

in fuel economy and CREE calculations based on the NMHC emission rate for the test interval 

and the volume percent of ethanol in the fuel using the following equation:

e e VP NMOG-FTPht NMHC-FTPht EtOH    1.0195 0.0031 

Eq. 1066.665-6

Where:

eNMOG-FTPht = mass emission rate of NMOG from the transient portion of the FTP hot-start test 

(bag 3).

eNMHC-FTPht = mass emission rate of NMHC from the transient portion of the FTP hot-start test 

(bag 3), calculated using ρNMHC-liq.

VPEtOH = volume percentage of ethanol in the test fuel.

(d) You may take the following additional steps when determining fuel economy and CREE 

under 40 CFR part 600:

(1) Calculate NMOG by interval using Eq. 1066.665-3 for individual bag measurements from the 

FTP.

(2) Calculate NMOG for two-bag FTPs using Eq. 1066.665-3 for hybrid-electric vehicles as 

described in 40 CFR 600.114.

(e) We consider NMOG emission values for diesel-fueled vehicles, CNG-fueled vehicles, LNGfueled vehicles, and LPG-fueled vehicles to be equivalent to NMHC emission values for all test 

cycles.

(f) For all fuels not covered by paragraphs (c) and (e) of this section, manufacturers may propose 

a methodology to calculate NMOG results from measured NMHC emissions. We will approve 

adjustments based on comparative testing that demonstrates how to properly represent NMOG 

based on measured NMHC emissions.

Deleted: 5

Comment [CAL21]: Example updated. 

Deleted: FTP 

Deleted: over

Deleted: FTP 

Deleted: 

Deleted: interval

Deleted: over

Deleted: FTP 

Deleted: interval

Deleted: complete

Deleted: over

Deleted: interval

Deleted: over

Deleted: interval
§1066.695 Data requirements.

Record the following information for each test:

(a) Test number.

(b) A brief description of the test vehicle (or other system/device tested).

(c) Date and time of day for each part of the test sequence.

(d) Test results. Also include a validation of driver accuracy as described in §1066.430(j).

(e) Driver and equipment operators.

(f) Vehicle information as applicable, including identification number, model year, applicable 

emission standards, vehicle model, vehicle class, carline, test group, durability group, engine 

family, evaporative/refueling emission family, basic engine description (including displacement, 

number of cylinders, turbocharger/supercharger used, and catalyst type), fuel system (type of 

fuel injection and fuel tank capacity and location), engine code, gross vehicle weight rating,

equivalent test weight, inertia weight class, actual curb weight at zero miles, actual road load at 

50 mph, transmission class and configuration, axle ratio, odometer reading, idle rpm, and drive 

wheel tire pressure.

(g) Dynamometer identification, inertia weight setting, indicated power absorption setting, and 

records to verify compliance with the driving distance and cycle-validation criteria as calculated 

from measured roll or shaft revolutions.

(h) Analyzer bench identification, analyzer ranges, recordings of analyzer output during zero, 

span, and sample readings.

(i) Associate the following information with the test record: test number, date, vehicle 

identification, vehicle and equipment operators, and identification of the measurements recorded.

(j) Test cell barometric pressure and humidity. You may use a central laboratory barometer if 

the barometric pressure in each test cell is shown to be within ±0.1 % of the barometric pressure 

at the central barometer location.

(k) Records to verify compliance with the ambient temperature requirements throughout the test 

procedure and records of fuel temperatures during the running loss test.

(l) [Reserved]

(m) For CVS systems record, dilution factor for each interval of the exhaust test and the 

following additional information:

(1) CFV and SSV Vmix for each interval of the exhaust test.

(2) PDP. Test measurements required to calculate Vmix for each interval of the exhaust test.

(n) The humidity of the dilution air if you remove H2O from an emission sample before 

measurement.

(o) Temperature of the dilute exhaust mixture and secondary dilution air (in the case of a doubledilution system) at the inlet to the respective gas meter or flow instrumentation used for 

particulate sampling. Determine minimum values, maximum values, average values, and percent 

of time outside of the tolerance over each test interval for the purpose of meeting the record 

keeping requirement of §1066.25.

(p) The maximum gas temperature over the course of the test within 20 cm upstream or 

downstream of the PM sample media.

(q) If applicable, the temperature of the heated FID, the gas in the heated sample line, and the 

heated filter. Determine minimum values, maximum values, average values, and percent of time 

outside of the tolerance over each test interval for the purpose of meeting the record keeping 

requirement of §1066.25.

Deleted: (e.g., filter)
(r) Gas meter or flow measurement instrumentation readings used for batch sampling over each 

test interval. Determine minimum, maximum, and average values over each test interval for the 

purpose of meeting the record keeping requirement of §1066.25.

(s) The stabilized pre-test weight and post-test weight of each particulate sample media (e.g., 

filter).

(t) Continuous temperature and humidity of the ambient air in which the particulate sample 

media (e.g., filter) are stabilized. Determine minimum values, maximum values, average values, 

and percent of time outside of the tolerance over each test interval for the purpose of meeting the 

record keeping requirement of §1066.25.

(u) For vehicles fueled by natural gas, the test fuel composition, including all carbon-containing 

compounds (except CO); e.g. CO2, of the natural gas-fuel used during the test. Record C1 and C2

compounds individually. You may record C3 through C5 hydrocarbons together, and you may 

record C6 and heavier hydrocarbon compounds together.

(v) Additional required records for liquefied petroleum gas-fueled vehicles. For vehicles fueled 

by liquefied petroleum gas, the test fuel composition, including all carbon-containing compounds

(except CO); e.g. CO2. Each hydrocarbon compound present, through C4 compounds, shall be 

individually reported. C5 and heavier hydrocarbons may be reported as a group. Record C1 and 

C4 compounds individually. You may record C5 and heavier hydrocarbon compounds together.

(w) For the AC17 air conditioning efficiency test procedure in §1066.835: interior volume, 

climate control system type and characteristics, refrigerant used, compressor type, and 

evaporator/condenser characteristics. 

Deleted: at the start and end of
Subpart H—Cold-Temperature Test Procedures

§1066.701 Applicability and general provisions.

(a) The procedures of this part 1066 may be used for testing at any ambient temperature. 

Section 1066.710 describes the provisions that apply for testing motor vehicles at a nominal 

temperature of 20 °C (68 °F); these procedures apply for motor vehicles as described in 40 CFR 

part 86, subpart S, and 40 CFR part 600. For other vehicles, see the standard-setting part to 

determine if your vehicle is required to meet emission standards outside the normal (20 to 30) °C 

((68 to 86) °F) temperature range.

(b) Do not apply the humidity correction factor in §1066.630(a) for cold-temperature testing.

§1066.710 Cold-testing procedures for measuring CO and NMHC emissions and 

determining fuel economy.

This section describes procedures for measuring carbon monoxide (CO) and nonmethane 

hydrocarbon (NMHC) emissions and determining fuel economy on a cold day using the FTP

driving schedule (see §1066.801). Figure 1 of this section shows the steps encountered as the 

test vehicle undergoes these procedures.

Deleted: testing

Deleted: 

Deleted: vechicles
Figure 1 of §1066.710— Cold-testing sequence for measurement of CO and NMHC emissions and determining fuel economy.
(a) Follow the exhaust emission measurement procedures specified in §§1066.410 through 

1066.430 and §1066.820(d), subject to the following exceptions and additional provisions:

(1) Measure and control ambient conditions as specified in paragraph (b) of this section.

(2) Use the heater and defroster as specified in paragraph (c) of this section.

(3) Precondition and stabilize the vehicle as specified in paragraphs (d) and (e) of this section. 

Ensure that there is no precipitation or dew on the vehicle before the emission test.

(4) For dynamometers that have independently heated bearings, start the emission test within 20 

minutes after the end of dynamometer warm up; for other dynamometers, start the emission test 

within 10 minutes after the end of dynamometer warm up.

(5) Adjusted the dynamometer to simulate the operation of a vehicle on the road at −7 °C. Base 

this adjustment by determining the road load force profile at −7 °C. You may also base the 

adjustment on a 10 percent decrease in the target coastdown time used for FTP testing.

(6) Analyze samples for NMHC, CO, and CO2. You do not need to analyze samples for other 

pollutants.

(b) Maintain ambient conditions as follows instead of following the specifications in subpart E of 

this part:

(1) Ambient temperature for emission tests. Measure and record ambient temperature in the test 

cell at least once every 60 seconds during the sampling period. The temperature must be (−7.0 

±1.7) °C at the start of the test and average temperature must be (−7.0 ±2.8) °C during the test. 

Instantaneous temperature values may be above −4.0 °C or below −9.0 °C, but not for more than 

3 minutes at a time during the test.

(2) Ambient temperature for preconditioning. Ambient temperatures must be between (−12.0

and −1.0) °C throughout the preconditioning period. The average ambient temperature during 

preconditioning must be (−7.0 ±2.8) °C. Instantaneous temperature values may be above 

−4.0 °C or below −9.0 °C, but not for more than 3 minutes at a time during the preconditioning 

period. You may precondition vehicles at temperatures above −7.0 °C or with a temperature 

tolerance greater than that described in this section (or both) if you determine that this will not 

cause NMHC, CO, or CO2 emissions to decrease; if you modify the temperature specifications 

for vehicle preconditioning, adjust the procedures described in this section appropriately for your 

testing. Use good engineering judgment to demonstrate that you meet the specified temperature 

tolerances specified in this paragraph (b)(2).

(3) Ambient humidity. Maintain humidity low enough to prevent condensation on the 

dynamometer rolls during testing.

(c) Heater and defroster usage. During the test, operate the vehicle interior climate control 

system with the interior heating system on and the air flow directed to the mode that primarily 

defrosts the front window. Set air conditioning controls to the “Off” position. You may not use 

any supplemental auxiliary heat during this testing. You may set the heater to any temperature 

and fan setting during vehicle preconditioning. The vehicle’s interior climate controls must be 

used to achieve the operation specified in this paragraph (c). Use good engineering judgment 

and take into account engine control changes (e.g., engine-off logic, idle speed operation, spark 

advance changes) and engine control features that may be directly affected by the fan or 

temperature settings.

(1) Manually controlled systems. (i) Prior to the first acceleration, 20 seconds after the start of 

the UDDS, set the climate control as follows (these settings may be initiated prior to starting the 

vehicle if allowed by the vehicle’s climate control system):

Deleted: c

Deleted: d

Deleted: 3

Deleted: 4

Deleted: average 

Deleted: during the sampling period 

Deleted: 4
(A) Temperature. Set manually operated to maximum heat. Automatic systems may optionally 

use the provisions of this paragraph (c)(1) and must set the temperature to 72 °F (22 °C) or 

higher.

(B) Fan speed. Set the fan speed to full off, or if a full off position is not available, the lowest 

available speed.

(C) Airflow direction. Direct airflow to the front window (window defrost mode). Using good 

engineering judgment, an alternative vent setting may be used if necessary to achieve the 

temperature and fan speed settings in this paragraph (c)(1).

(D) Air source. If independently controllable, set the airflow source control to the position 

which draws in outside air.

(ii) At the second idle of the test cycle, which occurs at the first deceleration to zero miles per 

hour, 125 seconds after the start of the test, set the fan speed to maximum, and, if not already set 

in this position, the airflow shall be directed fully to the front window in the window defrost 

mode. The temperature and air source settings must remain the same as in paragraph (c)(1) of 

this section. You must have the setting change completed by 130 seconds after the start of the 

test.

(iii) At the sixth idle of the test cycle, which occurs at the deceleration to zero miles per hour,

505 seconds after the start of the test, set the fan speed to the lowest setting that maintains air 

flow. You must have the setting change completed by 510 seconds after the start of the test. 

Using good engineering judgment, you may use alternative vent and/or higher fan speed settings 

for the remainder of the test. The temperature and air source settings must remain as in 

paragraph (c)(1)(i) of this section for the remainder of the test.

(2) Automatic control systems. Automatic control systems may use either the provisions in 

paragraph (c)(1) of this section or manufacturers may set the temperature at 72 °F and the air 

flow control to the front window defroster mode for the entire duration of the test.

(3) Multiple-zone systems. Vehicles with separate driver and passenger controls, or separate 

controls for the front seating region and for the passenger region behind the driver, must set all 

temperature and fan controls according to paragraphs (c)(1) through (c)(3) of this section.

(4) Alternative test procedures. We may approve the use of other settings under 40 CFR 

86.1840-01 if, for example, a vehicle’s climate control system is not compatible with the 

provisions of this section.

(d) Take the following steps to prepare and precondition vehicles for testing under this section:

(1) Prepare the vehicle as described in §1066.814(a). 

(2) Fill the fuel tank to approximately 40 % of the manufacturer’s nominal fuel tank capacity 

with the appropriate test fuel for low-temperature testing specified 40 CFR part 1065, subpart H. 

The temperature of the dispensed test fuel must be at or below 15.5 °C. If the leftover fuel in the 

fuel tank before the refueling event does not meet these specifications, drain the fuel tank before 

refueling. You may operate the vehicle prior to the preconditioning drive to eliminate fuel 

effects on adaptive memory systems.

(3) You may start the preconditioning drive once the fuel in the fuel tank reaches (−7.0 °C 

±5.6) °C. Precondition the vehicle as follows:

(i) Push or drive the vehicle onto the dynamometer.

(ii) Operate the vehicle over one UDDS. You may perform additional vehicle preconditioning 

with repeated driving over the UDDS, subject to our advance approval. 

Deleted: c

Deleted: The temperature of the dispensed test 

fuel must be at or below 15.5 °C.
(iii) Turn off the test vehicle and any cooling fans within 5 minutes after completing the 

preconditioning drive. Ambient temperature must be between (−12.0 to −1.0) °C in the 5 

minutes following the preconditioning drive.

(iv) Do not manually purge or load the evaporative canister.

(e) Soak the vehicle for (12 to 36) hours to stabilize it at test temperatures before starting the 

emission test as described in this paragraph (e). If you move a stabilized vehicle through a warm 

area when transporting it to the dynamometer for testing, you must restabilize the vehicle by 

holding it at an ambient temperature within the range specified in paragraph (b)(1) of this section 

for at least six times as long as the vehicle was exposed to warmer temperatures. Use one of the 

following methods to reach a stabilized condition:

(1) Cold storage. Measure and record ambient temperature in the test cell at least once every 60 

seconds during the ambient cold soak period; use these measured values to calculate an hourly 

average temperature. Ambient temperatures must be between (−12.0 and −1.0) °C throughout 

the ambient cold soak period. Each hourly average temperature must be (−7.0 °C ±2.8) °C. 

Instantaneous ambient temperatures during the ambient cold soak period may be above −4.0 °C 

or below −9.0 °C, but not for more than 3 minutes at a time. 

(2) Forced-cooling or warming. Position fans to blow temperature-controlled air onto the vehicle 

to stabilize the vehicle at the specified temperatures for emission testing. Position fans to target 

the vehicle’s drive train, engine block, and radiator rather than the oil pan. You may not place 

fans under the vehicle. You may consider the vehicle to be stabilized at the test temperature 

when the bulk oil temperature reaches (−7.0 ±1.7) °C; measure oil temperature at one or more 

points away from the side or bottom surfaces of the oil pan. Each oil temperature measurement 

must be within the specified range before stabilization is complete. Once the vehicle reaches this 

stabilized condition, cold soak the vehicle within the stabilized temperature range for at least one 

hour before starting the emission test. During this time, keep the ambient temperature within the 

range specified in paragraph (b)(1) of this section.

Deleted: d

Deleted: d

Deleted: 1

Deleted: 12

Deleted: hold
Subpart I—Exhaust Emission Test Procedures for Motor Vehicles 

§1066.801 Applicability and general provisions.

This subpart I specifies how to apply the test procedures of this part for motor vehicles at or 

below 14,000 pounds GVWR, including light-duty vehicles, light-duty trucks, and heavy-duty 

vehicles at or below 14,000 pounds GVWR that are subject to chassis testing for exhaust 

emissions. For these vehicles, references in this part 1066 to the standard-setting part include 

this subpart I.

(a) Use the procedures detailed in this subpart to measure vehicle emissions over a specified 

drive schedule in conjunction with subpart E of this part. Where the procedures of subpart E of 

this part differ from this subpart I, the provisions in this subpart I take precedence.

(b) Collect samples of every pollutant for which an emission standard applies, unless specified 

otherwise.

(c) This subpart covers the following test procedures:

(1) The Federal Test Procedure (FTP), which includes the general driving cycle. This procedure 

is also used for measuring evaporative emissions. This may be called the conventional test since 

it was adopted with the earliest emission standards.

(i) The FTP consists of one Urban Dynamometer Driving Schedule (UDDS) as specified in 

paragraph (a) of Appendix I of 40 CFR part 86, followed by a 10-minute soak with the engine 

off and repeat driving through the first 505 seconds of the UDDS. Note that the UDDS 

represents about 7.5 miles of driving in an urban area. Engine startup (with all accessories 

turned off), operation over the initial UDDS, and engine shutdown make a complete cold-start 

test. The hot-start test consists of the first 505 seconds of the UDDS following the 10-minute 

soak and a hot-running portion of the UDDS after the first 505 seconds. The first 505 seconds of 

the UDDS is considered the transient portion; the remainder of the UDDS is considered the 

stabilized (or hot-stabilized) portion. The hot-stabilized portion for the hot-start test is generally 

measured during the cold-start test; however, in certain cases, the hot-start test may involve a 

second full UDDS following the 10-minute soak, rather than repeating only the first 505 seconds. 

See §§1066.820 and 1066.822.

(ii) Evaporative emission testing includes a preconditioning drive with the UDDS and a full FTP 

cycle, including exhaust measurement, followed by evaporative emission measurements. In the 

three-day diurnal test sequence, the exhaust test is followed by a running loss test consisting of a 

UDDS, then two New York City Cycles as specified in paragraph (e) of Appendix I of 40 CFR 

part 86, followed by another UDDS; see 40 CFR 86.134-96. Note that the New York City Cycle 

represents about 1.18 miles of driving in a city center. The running loss test is followed by a 

high-temperature hot soak test as described in 40 CFR 86.138-96 and a three-day diurnal 

emission test as described in 40 CFR 86.133-96. In the two-day diurnal test sequence, the 

exhaust test is followed by a low-temperature hot soak test as described in 40 CFR 86.138-96(k) 

and a two-day diurnal emission test as described in 40 CFR 86.133-96(p). 

(iii) Refueling emission tests for vehicles that rely on integrated control of diurnal and refueling 

emissions includes vehicle operation over the full FTP test cycle corresponding to the three-day 

diurnal test sequence to precondition and purge the evaporative canister. For non-integrated 

systems, there is a preconditioning drive over the UDDS and a refueling event, followed by 

repeated UDDS driving purge the evaporative canister. The refueling emission test procedures 

are described in 40 CFR 86.150 through 86.157.

Comment [CAL22]: The acronyms for the test 

cycles are spelled out in this paragraph. Note that 

the acronyms first occur in 1066.105 and are not 

spelled out there. They are defined in 1066.1005. 

Should we just use the acronyms in this paragraph 

(c)? Should we define the acronyms in 1066.105? 

Deleted: f

Deleted: 7
(2) The Supplemental Federal Test Procedure (SFTP) measures the emission effects from 

aggressive driving and operation with the vehicle’s air conditioner. The SFTP is based on a 

composite of three different test elements. In addition to the FTP, vehicles generally operate

over the US06 and SC03 driving schedules as specified in paragraphs (g) and (h) of Appendix I 

of 40 CFR part 86, respectively. In the case of heavy-duty vehicles above 10,000 pounds 

GVWR and at or below 14,000 pounds GVWR, SFTP testing involves additional driving over 

the LA-92 driving schedule specified in paragraph (c) of 40 CFR part 86, Appendix I, instead of 

the US06 driving schedule. Note that the US06 driving schedule represents about 8.0 miles of 

relatively aggressive driving; the SC03 driving schedule represents about 3.6 miles of urban 

driving with the air conditioner operating; and the LA-92 driving schedule represents about 9.8

miles of relatively aggressive driving for commercial trucks. See §§1066.820 and 1066.822.

(3) The Highway Fuel Economy Test (HFET). The HFET is specified in Appendix I of 40 CFR 

part 600. Note that the HFET represents about 10.2 miles of rural and freeway driving with an 

average speed of 48.6 mph and a maximum speed of 60.0 mph. See §1066.839.

(4) Cold-temperature testing. Cold-temperature standards apply for CO and NMHC emissions 

when vehicles operate over the FTP at a nominal temperature of -7 °C. See 40 CFR part 86, 

subpart C.

(5) Emission measurement to determine air conditioning credits for greenhouse gas standards. In 

this optional procedure, manufacturers operate vehicles over repeat runs of the AC17 test 

sequence to allow for calculating credits as part of demonstrating compliance with CO2 emission 

standards. The AC17 test sequence consists of a UDDS preconditioning drive, followed by 

emission measurements over the SC03 and HFET driving schedules. See §1066.835.

(d) The following provisions apply for all testing:

(1) Ambient temperatures encountered by the test vehicle must be (20 to 30) °C, unless 

otherwise specified. Where ambient temperature specifications apply before or between test 

measurements, the vehicle may be exposed to temperatures outside of the specified range for up 

to 10 minutes to account for vehicle transport or other actions to prepare for testing. The 

temperatures monitored during testing must be representative of those experienced by the test 

vehicle. For example, do not measure ambient temperatures near a heat source.

(2) Do not operate or store the vehicle at an incline if good engineering judgment indicates that it 

would affect emissions.

(3) If a test is void after collecting emission data from previous test segments, the test may be 

repeated to collect only those data points needed to complete emission measurements. You may 

combine emission measurements from different test runs to demonstrate compliance with 

emission standards. 

(4) Prepare vehicles for testing as described in §1066.814.

(e) The following figure illustrates the FTP test sequence for measuring exhaust and evaporative 

emissions:
Figure 1 of §1066.801–FTP test sequence. 

Fuel drain and fill

Vehicle Soak

Preconditioning drive

1 hour MAX

Fuel drain and fill

Precondition canister Precondition canister

Cold start exhaust test Cold start exhaust test

10 minutes 10 minutes

Hot start exhaust test Hot start exhaust test

1-5 hours 7 minutes MAX

Running loss test Hot soak test

7 minutes max 68 - 86 °F ambient

Hot soak test

90-100 °F ambient Vehicle soak

Vehicle soak Diurnal emission test

2 heat builds in 48 hours

Diurnal emission test

3 heat builds in 72 hours

6-36 hours

12-36 hours

1 hour

6-36 hours

1 hour

6-36 hours

Start

End

End

Diesel 

Only

§1066.810 Road load power, test weight, and inertia weight class determination.

(a) Simulate a vehicle’s test weight on the dynamometer using the appropriate equivalent test 

weight shown in Table 1 of this section. Equivalent test weights are established according to 

each vehicle’s test weight basis, as described in paragraph (b) of this section. Table 1 also 

specifies the inertia weight class corresponding to each equivalent test weight; the inertia weight 

class allows for grouping vehicles with a range of equivalent test weights. Table 1 follows:

Table 1 of §1066.810–Equivalent test weights (pounds)

Test weight

basis

Equivalent test 

weight

Inertia weight 

class

Up to 1062 1000 1000 

1063 to 1187 1125 1000 

1188 to 1312 1250 1250 

1313 to 1437 1375 1250 

1438 to 1562 1500 1500 

1563 to 1687 1625 1500 

1688 to 1812 1750 1750 

1813 to 1937 1875 1750 

1938 to 2062 2000 2000 

2063 to 2187 2125 2000 

2188 to 2312 2250 2250 

2313 to 2437 2375 2250 

2438 to 2562 2500 2500 

2563 to 2687 2625 2500 
2688 to 2812 2750 2750 

2813 to 2937 2875 2750 

2938 to 3062 3000 3000 

3063 to 3187 3125 3000 

3188 to 3312 3250 3000 

3313 to 3437 3375 3500 

3438 to 3562 3500 3500 

3563 to 3687 3625 3500 

3688 to 3812 3750 3500 

3813 to 3937 3875 4000 

3938 to 4125 4000 4000 

4126 to 4375 4250 4000 

4376 to 4625 4500 4500 

4626 to 4875 4750 4500 

4876 to 5125 5000 5000 

5126 to 5375 5250 5000 

5376 to 5750 5500 5500 

5751 to 6250 6000 6000 

6251 to 6750 6500 6500 

6751 to 7250 7000 7000 

7251 to 7750 7500 7500 

7751 to 8250 8000 8000 

8251 to 8750 8500 8500 

8751 to 9250 9000 9000 

9251 to 9750 9500 9500 

9751 to 10250 10000 10000 

10251 to 10750 10500 10500 

10751 to 11250 11000 11000 

11251 to 11750 11500 11500 

11751 to 12250 12000 12000 

12251 to 12750 12500 12500 

12751 to 13250 13000 13000 

13251 to 13750 13500 13500 

13751 to 14000 14000 14000 

(b) The test weight basis for non-MDPV heavy-duty vehicles is “adjusted loaded vehicle weight”. 

For all other vehicles, the test weight basis for establishing equivalent test weight is “loaded 

vehicle weight”. These load terms are defined in 40 CFR 86.1803.

(c) For FTP, SFTP, New York City Cycle, HFET, and LA-92 testing, determine road load forces

for each test vehicle at speeds between 9.3 and 71.5 miles per hour. The road load force must 

represent vehicle operation on a smooth, level road with no wind or calm winds, no precipitation, 

an ambient temperature of approximately 20 °C, and atmospheric pressure of 98.21 kPa. You 

may extrapolate road load force for speeds below 10 mph.

§1066.814 Vehicle preparation.

(a) Include additional fittings and adapters, as required, to accommodate a fuel drain at the 

lowest point possible in the tank(s) as installed on the vehicle.

(b) For preconditioning that involves loading an evaporative emission canister with butane, 

provide valving or other means as necessary to allow purging and loading of the canister.

(c) For vehicles to be tested for running loss emissions (40 CFR 86.134), prepare the fuel tank

for measuring temperature and pressure as specified in 40 CFR 86.107–98(e) and (f) and 40 CFR 

86.134. Vapor temperature measurement is optional during the running loss test.

(d) For vehicles to be tested for running loss emissions, prepare the exhaust system by sealing or 

plugging all detectable sources of exhaust gas leaks. Inspect or test the exhaust system to ensure 

Deleted: and 

Deleted: 10

Deleted: 0
that there are no leaks that would cause exhaust hydrocarbon emissions to be detected as running 

losses.

(e) The following provisions apply for preconditioning steps to reduce nonfuel emissions to 

normal vehicle background levels for vehicles subject to Tier 3 evaporative emission standards 

under 40 CFR 86.1813:

(1) You must notify us in advance if you plan to perform such preconditioning. This notice must 

include a detailed description of the intended procedures and any measurements or thresholds for 

determining when stabilization is complete. You need not repeat this notification for additional 

vehicle testing in the same or later model years as long as your preconditioning practice 

conforms to these procedures.

(2) You may precondition a vehicle as described in paragraph (e)(1) of this section only within 

12 months after the vehicle’s original date of manufacture, except that you may remove the spare 

tire and replace the windshield washer fluid with water for any testing.

§1066.820 Exhaust emission test procedures for FTP testing.

(a) General. The FTP exhaust emission test sequence consists of a cold-start test and a hot-start 

test as described in §1066.801.

(b) PM sampling options. Collect PM using any of the procedures specified in paragraphs (b)(1) 

through (5) of this section and use the corresponding equation in §1066.822 to calculate FTP 

composite emissions. Testing must meet the requirements related to filter face velocity as 

described in 40 CFR 1065.170(c)(1)(vi), except as specified in paragraphs (b)(4) and (5) of this 

section. For procedures involving flow weighting, set the filter face velocity to a weighting 

target of 1.0 to meet the requirements of 40 CFR 1065.170(c)(1)(vi). Allow filter face velocity 

to decrease as a percentage of the weighting factor if the weighting factor is less than 1.0. Use 

the appropriate equations in §1066.620 to show that you meet the dilution factor requirements of 

§1066.110(b)(2)(iii)(B).

(1) You may collect a separate PM sample for transient and stabilized portions of the cold-start 

UDDS and the hot-start UDDS. This may either be done by sampling with 3 bags or 4 bags. 

You may omit the stabilized portion of the hot-start test (bag 4) and use the stabilized portion of 

the cold-start test (bag 2) in its place.

(2) You may collect PM on one filter over the cold-start UDDS and on a separate filter over the 

hot-start UDDS.

(3) You may collect PM on one filter over the cold-start UDDS (bag 1 and bag 2) and on a 

separate filter over the 867 seconds of the stabilized portion of the cold-start UDDS and the first 

505 seconds of the hot-start UDDS (bag 2 and bag 3). Note that this option involves duplicate 

measurements during the stabilized portion of the cold-start UDDS.

(4) You may collect PM on a single filter over the cold-start UDDS and the first 505 seconds of 

the hot-start UDDS. If you use this method, adjust your sampling system flow rate to weight the 

filter face velocity over the three intervals of the FTP based on weighting targets of 0.43 for bag 

1, 1.0 for bag 2, and 0.57 for bag 3.

(5) You may collect PM on a single filter over the cold-start UDDS and the full hot-start UDDS. 

If you use this method, adjust your sampling system flow rate to weight the filter face velocity 

based on weighting targets of 0.75 for the cold-start UDDS and 1.0 for the hot-start UDDS.

(c) Gaseous sampling options. Collect gaseous samples using any of the following procedures:

(1) You may collect a single sample for a full UDDS (cold-start or hot-start).

(2) You may sample emissions separately for transient and stabilized portions of any UDDS.
(3) You may omit the stabilized portion of the hot-start test (bag 4) and use the stabilized portion 

of the cold-start test (bag 2) in its place.

(d) Test sequence. Follow the exhaust emission measurement procedures specified in 

§§1066.410 through 1066.430, subject to the following exceptions and additional provisions:

(1) Take the following steps for the cold-start test:

(i) Precondition the vehicle as described in 40 CFR 86.132. Initiate the cold-start test following 

the 12 to 36 hour soak period.

(ii) Start sampling and recording simultaneously with starting the vehicle. Place the vehicle in 

gear 15 seconds after engine starting, which is 5 seconds before the first acceleration.

(iii) At the end of the deceleration scheduled to occur 505 seconds into the cold-start UDDS, 

simultaneously switch all the sample flows from the cold-start transient interval to the stabilized 

interval, stopping all cold-start transient interval sampling and recording, including background 

sampling. Reset integrating devices for the stabilized interval and indicate the end of the coldstart interval in the recorded data. Operate the vehicle over the remainder of the UDDS. Turn 

the engine off 2 seconds after the end of the last deceleration in the stabilized interval (1,369 

seconds after the start of the driving schedule).

(iv) Five seconds after the engine stops running, stop all stabilized interval sampling and 

recording, including background sampling. Stop any integrating devices for the stabilized 

interval and indicate the end of the stabilized interval in the recorded data. Note that the 5 

second delay is intended to account for sampling system transport.

(2) Take the following steps for the hot-start test:

(i) Initiate the hot-start test (9 to 11) minutes after the end of the sample period for the cold-start 

UDDS. 

(ii) Repeat the steps in paragraph (d)(1)(ii) of this section. Operate the vehicle over the first 505 

seconds of the UDDS. At the end of the deceleration scheduled to occur 505 seconds into the 

hot-start UDDS, turn off the engine and simultaneously stop all hot-start sampling and recording, 

including background sampling, and any integrating devices.

(iii) For tests that do not include bag 4 operation, turn the engine off. To include bag 4 

measurement, operate the vehicles over the remainder of the UDDS and conclude the testing as 

described in paragraphs (d)(1)(iii) and (iv) of this section.

(3) This completes the procedure for measuring FTP exhaust emissions. See 40 CFR part 86, 

subpart B, and §1066.801 for continuing to evaporative or refueling tests. 

§1066.822 Composite calculations for FTP exhaust emissions.

(a) Determine the mass of exhaust emissions of each pollutant for each FTP test interval as 

described in §1066.610.

(b) Calculate the final composite gaseous test results as a mass-weighted value, e[emission]-FTPcomp, 

in grams per mile using the following equation:

c h

[emission]-FTPcomp

ct cs ht hs

0.43 0.57 m m e DD DD

  

         

 Eq. 1066.822-1

Where:

mc = the combined mass emissions determined from the cold-start UDDS test interval (generally 

known as bag 1 and bag 2), in grams.

Deleted: (4) You may apply the provisions of 

paragraph (b) of this section for any gaseous batch 

measurement, consistent with good engineering 

judgment.¶

Deleted: Fifteen seconds after the engine starts, 

place the transmission in gear. Twenty seconds after 

the engine starts, begin the initial vehicle 

acceleration of the driving schedule.
Dct = the measured driving distance from the transient portion of the cold-start test (bag 1), in 

miles.

Dcs = the measured driving distance from the stabilized portion of the cold-start test (bag 2), in 

miles.

mh = the combined mass emissions determined from the hot-start UDDS test interval in grams. 

This is the hot-stabilized portion from either the first or second UDDS (bag 2, unless you 

measure bag 4), in addition to the hot transient portion (bag 3).

Dht = the measured driving distance from the transient portion of the hot-start test (bag 3), in 

miles.

Dhs = the measured driving distance from the stabilized portion of the hot-start test (bag 4), in 

miles. Set Dhs = Dcs for testing where the hot-stabilized portion of the UDDS is not run.

(c) Calculate the final composite PM test results as a mass-weighted value, ePM-FTPcomp, in grams

per mile as follows:

(1) Use the following equation for PM measured as described in §1066.820(b)(1), (2), or (3):

PM-cUDDS PM-hUDDS

PM-FTPcomp

ct cs ht hs

0.43 0.57 m m e DD DD

  

         

 Eq. 1066.822-2

Where:

mPM-cUDDS = the combined PM mass emissions determined from the cold-start UDDS test interval 

(bag 1 and bag 2), in grams, as calculated using Eq. 1066.610-2.

mPM-hUDDS = the combined PM mass emissions determined from the hot-start UDDS test interval

(bag 3 and bag 4), in grams, as calculated using Eq. 1066.610-2. This is the hot-stabilized 

portion from either the first or second UDDS (bag 2, unless you measure bag 4), in addition to 

the hot transient portion (bag 3).

(2) Use the following equation for PM measured as described in §1066.820(b)(4):

   PM

PM-FTPcomp

ct cs ht 0.43 0.57

m e D D D    

 Eq. 1066.822-3

Where:

mPM = the combined PM mass emissions determined from the cold-start UDDS test interval and 

the first 505 seconds of the hot-start UDDS test interval (bag 1, bag 2, and bag 3), in grams, as 

calculated using Eq. 1066.610-3.

(3) Use the following equation for PM measured as described in §1066.820(b)(5):

   PM

PM-FTPcomp

ct cs ht hs 0.43 0.57

m e D D DD   

 Eq. 1066.822-4

Where:

mPM = the combined PM mass emissions determined from the cold-start UDDS test interval and 

the hot-start UDDS test interval (bag 1, bag 2, bag 3, and bag 4), in grams, as calculated using Eq. 

1066.610-4.

§1066.830 Supplemental Federal Test Procedures; overview.
Sections 1066.831 and 1066.832 describe the detailed procedures for the Supplemental Federal 

Test Procedure (SFTP). This testing applies for all vehicles subject to the SFTP standards in 40 

CFR part 86, subpart S. The SFTP test procedure consists of FTP testing and two additional test 

elements—a sequence of vehicle operation with more aggressive driving and a sequence of 

vehicle operation that accounts for the impact of the vehicle’s air conditioner. 

(a) The SFTP standard applies as a composite representing the three test elements. The emission 

results from the aggressive driving test element (§1066.831), the air conditioning test element 

(§1066.832), and the FTP test element (§1066. 820) are analyzed according to the calculation 

methodology and compared to the applicable SFTP emission standards as described in 40 CFR 

part 86, subpart S.

(b) The test elements of the SFTP may be run in any sequence that includes the specified 

preconditioning steps.

§1066.831 Exhaust emission test procedures for aggressive driving.

(a) This section describes how to test using the US06 or LA-92 driving schedule. The US06 

driving schedule can be divided into two test intervals—the US06 City cycle comprises the 

combined portions of the cycle from 1 to 130 seconds and from 495 to 596 seconds, and the 

US06 Highway cycle comprises the portion of the cycle between 130 and 495 seconds. See 

§1066.801 for further information on the driving schedules.

(b) Take the following steps to precondition vehicles for testing under this section:

(1) Drain and refill the vehicle’s fuel tank(s) in any of the following cases:

(i) For aggressive-driving tests that do not follow FTP or HFET testing.

(ii) For a test element that starts more than 72 hours after the most recent FTP or HFET 

measurement (with or without evaporative emission measurements).

(iii) For testing in which the test vehicle has not remained in an area where ambient temperatures 

were within the range specified for testing since the previous FTP or HFET.

(2) Keep ambient temperatures within the ranges specified for test measurements throughout the 

preconditioning sequence.

(3) Warm up the vehicle to a stabilized condition as follows:

(i) Push or drive the vehicle onto the dynamometer.

(ii) Operate the vehicle one time over one of the driving schedules specified in this paragraph 

(b)(3)(ii). You may ask us to use a particular preconditioning driving schedule if that is related 

to fuel effects on adaptive memory systems. For our testing, we will generally operate the 

vehicle over the same preconditioning cycle that will be used for testing in this section. You 

may exercise your sampling equipment, but you may not determine emissions results during 

preconditioning. Choose from the following driving schedules:

(A) The first 505 seconds of the UDDS (bag 1)

(B) The last 866 seconds of the UDDS (bag 2).

(C) The HFET driving schedule.

(D) US06 driving schedule or, for heavy-duty vehicles above 10,000 pounds GVWR with a 

power to weight ratio at or below 0.024 hp/lbm, just the highway portion of the US06 driving 

schedule. 

(E) The SC03 driving schedule.

(F) The LA-92 driving schedule. 

(4) Allow the vehicle to idle for (1 to 2) minutes. This leads directly into the test measurements 

described in paragraph (c) of this section.
(c) For testing involving the full US06 driving schedule, you may collect emissions from 

separate city and highway test intervals (see 40 CFR part 600), or you may collect emissions 

over the full US06 driving schedule as a single test interval. Take the following steps for to 

measure emissions over separate city and highway test intervals:

(1) At 130 seconds, simultaneously stop all US06 City, and start all US06 Highway sampling,

recording, and integrating (including background sampling). At 136 seconds (before the 

acceleration), record the measured dynamometer roll revolutions.

(2) At 495 seconds, simultaneously stop all US06 Highway, and start all US06 City sampling,

recording, and integrating (including background sampling). At 500 seconds (before the 

acceleration), record the measured dynamometer roll revolutions.

(3) Except as specified in paragraph (c)(4) of this section, treat the emissions from the first and 

second portions of the US06 City test interval as a single sample.

(4) If you collect gaseous emissions over separate city and highway test intervals, you may still 

collect PM over the full US06 driving schedule as a single test interval. If you do this, calculate 

a composite dilution factor based on city and highway emissions using Eq. 1066.620-4 to show 

that you meet the dilution factor requirements of §1066.110(b)(2)(iii)(B). 

(d) For diesel-fueled vehicles, measure THC emissions on a continuous basis as described in 40 

CFR part 1065. For separate measurement of the city and highway test intervals as described in 

paragraph (c) of this section, perform separate calculations for each portion of the test cycle.

(e) Follow the exhaust emission measurement procedures specified in §§1066.410 through 

1066.430, subject to the following exceptions and additional provisions:

(1) Following the preconditioning specified in paragraph (b) of this section, place the vehicle in 

gear and simultaneously start sampling and recording. Begin the first acceleration 5 seconds 

after placing the vehicle in gear.

(2) Operate the vehicle over the full US06 driving schedule, except as follows:

(i) For heavy-duty vehicles above 10,000 pounds GVWR, operate the vehicle over the LA-92 

driving schedule.

(ii) Heavy-duty vehicles at or below 10,000 pounds GVWR with a power-to-weight ratio at or 

below 0.024 hp/lbm may be certified using only the highway portion of the US06 driving 

schedule as described in 40 CFR 86.1816-18.

(iii) All heavy-duty vehicles shall be tested at their adjusted loaded vehicle weight as described 

in 40 CFR 86.1816-18.

(3) Turn the engine off 2 seconds after the end of the last deceleration. Five seconds after the 

engine stops running, stop all sampling and recording, including background sampling. Stop any 

integrating devices and indicate the end of the test cycle in the recorded data.

(4) Correct calculated NOx emissions as described in §1066.630(a)(1).

§1066.832 Exhaust emission test procedure for SC03 emissions.

This section describes how to test using the SC03 driving schedule (see §1066.801). This 

procedure is designed to determine gaseous exhaust emissions while simulating an urban trip on 

a hot summer day. The provisions of 40 CFR part 86 and 40 CFR part 600 waive SC03 testing 

for some vehicles; in those cases, calculate SFTP composite emissions by adjusting the 

weighting calculation as specified in 40 CFR part 86, subpart S.

(a) Drain and refill the vehicle’s fuel tank(s) if the test element starts more than 72 hours after the 

last drain and fill operation.

Deleted: §1066.830

Deleted: . See

Deleted: before

Deleted: driving schedule
(b) Keep the vehicle in an environment meeting the conditions described in paragraph (f) of this 

section throughout the preconditioning sequence. 

(c) Warm up the vehicle to a stabilized condition as follows: 

(1) Push or drive the test vehicle onto the dynamometer.

(2) Close the vehicle’s windows before testing.

(3) The test cell and equipment must meet the specifications in paragraph (e) of this section. 

Measure and control ambient conditions as specified in paragraph (f) of this section.

(4) Set the vehicle’s air conditioning controls by selecting A/C mode and “maximum”, setting 

airflow to “recirculate” (if so equipped), selecting the highest fan setting, and turning the A/C 

temperature to full cold (or 72 °F for automatic systems). Turn the control to the “on” position 

before testing so the air conditioning system is active whenever the engine is running.

(5) Operate the test vehicle one time over the first 505 seconds of the UDDS (bag 1), the last 867 

seconds of the UDDS (bag 2), or the SC03 driving schedule. If the air conditioning test 

sequence starts more than 2 hours after a different exhaust emission test, you may instead operate 

the vehicle one time over the full UDDS.

(6) Following the preconditioning drive, turn off the test vehicle and the vehicle cooling fan(s) 

and allow the vehicle to soak for (9 to 11) minutes.

(d) Follow the exhaust emission measurement procedures specified in §§1066.410 through 

1066.430, subject to the following exceptions and additional provisions: 

(1) Place the vehicle in gear 15 seconds after engine starting, which is 3 seconds before the first 

acceleration. Follow the SC03 driving schedule. 

(2) Turn the engine off 2 seconds after the end of the last deceleration. Five seconds after the 

engine stops running, stop all sampling and recording, including background sampling. Stop any 

integrating devices any indicate the end of the test cycle in the recorded data. Note that the 5 

second delay is intended to account for sampling system transport.

(3) Correct calculated NOx emissions as described in §1066.630(a)(2).

(e) The following requirement apply for the test cell and cooling fan configuration:

(1) Minimum test cell size. The test cell must be at least 20 feet wide, 40 feet long, and 10 feet 

high, unless we approve the use of a smaller test cell. We will approve this only if you 

demonstrate that the smaller test cell is capable of meeting all the requirements of this section.

(2) Vehicle frontal air flow. Verify that the fan configuration meets the requirements of 

§1066.105(c)(3).

(f) Maintain ambient conditions as follows: 

(1) Ambient temperature. Measure and record ambient temperature in the test cell at least once 

every 30 seconds during the sampling period. Alternatively, if you collect data of at least 0.2 Hz, 

you may use a moving average of intervals of not more than 30 seconds to record and report air 

temperature and humidity. Control ambient temperature during all phases of the air conditioning 

test sequence to 35.0 ±3.0 °C throughout the test and (33.6 to 36.4) °C on average. 

(2) Ambient humidity. Measure and record ambient humidity in the test cell at least once every 

30 seconds during the sampling period. Control ambient humidity during emission sampling as 

described in §1066.425(d).

(3) Conditions before and after testing. Use good engineering judgment to demonstrate that you 

meet the specified instantaneous temperature and humidity tolerances in paragraphs (e)(1) and 

(2) of this section at all times before and between emission measurements.

(4) Solar heat load. Simulate solar heating as follows:

Deleted: a

Deleted: e

Deleted: b

Deleted: 3

Deleted: c

Deleted: (1) Close the vehicle’s windows before 

testing.¶

(2) The test cell and equipment must meet the 

specifications in paragraph (d) of this section. 

Measure and control ambient conditions as specified 

in paragraph (e) of this section.¶

(3) Set the vehicle’s air conditioning controls by 

selecting A/C mode and “maximum”, setting airflow 

to “recirculate” (if so equipped), selecting the 

highest fan setting, and turning the A/C temperature 

to full cool (or 72 °F for automatic systems). Turn 

the control to the “on” position before testing so the 

air conditioning system is active whenever the 

engine is running.¶

Deleted: 4

Deleted: 5

Deleted: before

Deleted: end of the driving schedule

Deleted: 6

Deleted: d

Deleted: before each test

Deleted: e

Deleted: 

Deleted: emission sampling

Deleted: 
(i) You may use a metal halide lamp, a sodium lamp, or a quartz halogen lamp with dichroic 

mirrors as a radiant energy emitter. We may also approve the use of a different type of radiant 

energy emitter if you demonstrate that it meets the requirements of this section. 

(ii) We recommend achieving radiant heating with spectral distribution characteristics as 

described in the following table:

Table 1 of §1066.832–Recommended Spectral Distribution

Band width (nm) Percent of total spectrum

Lower limit (%) Upper limit (%)

<320a — 0

320–400 0 7

400–780 45 55

>780 35 53

a

Note that you may need to filter the UV region between 280 and 320 nm.

(iii) Determine radiant energy intensity experienced by the vehicle as the average value between 

two measurements along the vehicle’s centerline, one at the base of the windshield and the other 

at the bottom of the rear window (or equivalent location for vehicles without a rear window). 

This value must be 850 ±45 W/m2. Instruments for measuring radiant energy intensity must 

meet the following minimum specifications:

(A) Sensitivity of 9 microvolts per W/m2.

(B) Response time of 5 seconds. For purposes of this requirement, “response time” means the 

time for the instrument to reach 95 percent of its equilibrium response after a step change in 

radiant intensity.

(C) Linearity of ± 0.5 %.

(D) Cosine response error of no more than ± 1 % for 0–70 degree zenith angles. The cosine 

response error is the percentage difference between the intensity measured at a given angle and 

the intensity predicted from the zero-degree intensity and the cosine of the incident angle. The 

angle of incidence of radiant energy is defined as 90 degrees from the test cell floor.

(iv) Check the uniformity of radiant energy intensity at least every 500 hours of emitter usage or 

every 6 months, whichever is sooner, and after any major modifications affecting the solar 

simulation. Determine uniformity by measuring radiant energy intensity as described in 

paragraph (e)(4)(iii) of this section at each point of a 0.5 m grid over the vehicle’s full footprint, 

including the edges of the footprint, at an elevation 1 m above the floor. Measured values of 

radiant energy intensity must be between (722 and 978) W/m2 at all points.

§1066.835 AC17 air conditioning efficiency test procedure.

(a) Overview. This section describes a voluntary procedure for measuring the net impact of air 

conditioner operation on CO2 emissions. See 40 CFR 86.1868 for provisions describing how to 

use these procedures to calculate credits and otherwise comply with emission standards. 

(b) Test cell. Operate the vehicle in a test cell meeting the specifications described in 

§1066.832(e). You may add airflow up to at a maximum of 4 miles per hour during engine 

idling and when the engine is off if that is needed to meet ambient temperature or humidity 

requirements.

Deleted: 86

Deleted: d
(c) Ambient conditions. Measure and control ambient conditions as specified in §1066.832(f), 

except that you must control ambient temperature during emission sampling to (22.0 to 28.0) °C

throughout the test and (23.5 to 26.5) °C on average. For the emission sampling portion of the 

test, these tolerances apply to the combined SC03 and HFET drive cycles. Note that you must 

set the same ambient temperature target for both the air conditioning on and off portions of 

emission sampling. Control ambient temperature during the preconditioning cycle and 30 

minute soak (non-emissions sampling modes) to 25.0 ±5.0 °C. For these same non-emissions 

modes target the specified ambient humidity levels but you do not need to meet the humidity 

tolerances. Note that solar heating is disabled for certain test intervals as described in this 

section.

(d) Interior air temperature measurement. Measure and record the vehicle’s interior air 

temperature at least once every 5 seconds during the sampling period. Measure temperature at 

the outlet of the center-most duct on the dashboard and approximately 30 mm behind the driver 

and passenger’s headrests. 

(e) Air conditioning system settings. For testing that requires the air conditioning to be operating, 

set the vehicle’s air conditioning controls as follows: 

(1) For automatic systems, set the temperature control to 72 °F (22 °C).

(2) For manual systems, select A/C mode, set the temperature to full cold and “maximum”, set 

airflow to “recirculate” (if so equipped), and select the highest fan setting. During the first idle 

period of the SC03 driving schedule (between 186 and 204 seconds), reduce the fan speed to 

nominally 50 % of maximum fan speed, set airflow to “fresh air” (if so equipped), and adjust the 

temperature setting to target a temperature of 55° F (13 °C) at the dashboard air outlet. Maintain

these settings for the remainder of the test. You may rely on prior temperature measurements to 

determine the temperature adjustment setting, however, if the 55 °F (13 °C) dashboard air 

temperature cannot be met, setting the control to 50% of maximum blower, airflow to “fresh air” 

and temperature to full cold is sufficient. If the vehicle is equipped with technology that defaults

to recirculated air at ambient temperatures above 75 °F (22 °C), that technology should remain 

enabled throughout the test, which may mean not setting the airflow to “recirculate” at the start 

and/or not setting the airflow to "fresh air" during the first idle period of the SCO3 driving 

schedule.

(f) Test procedure. Follow the exhaust emission measurement procedures specified in 

§§1066.410 through 1066.430, subject to the following exceptions and additional provisions: 

(1) Prepare each test vehicle for a series of tests according to 40 CFR 86.132-00 (a) through (g). 

If the vehicle has been tested within the last 36 hours concluding with a 12 to 36 hour soak, 

continue on to paragraph (f)(2) of this section, otherwise perform an additional UDDS 

preconditioning cycle that concludes with a 12 to 36 hour soak. You may use a forced cool 

down system to bring critical vehicle temperatures to within soak temperature limits. Critical 

temperatures include: transmission oil, engine oil, engine coolant, and cabin air temperatures.

(2) Open the vehicle’s windows and operate the vehicle over a preconditioning UDDS with no 

solar heating and with the air conditioning off. At the end of the preconditioning drive, turn off 

the test vehicle and all cooling fans. 

(3) Turn on solar heating within one minute after turning off the engine. Once the solar energy 

intensity reaches 805 W/m2, let the vehicle soak for 30 ±1 minutes. You may alternatively rely 

on prior measurements to start the soak period after a defined period of warming up to the 

specified solar heat load. Close the vehicle’s windows at the start of the soak period; ensure that 

the windows are adequately closed where instrumentation and wiring pass through to the interior.

Deleted: 86

Deleted: e

Deleted: 25.0 ±3.0

Deleted: 6

Deleted: 4

Deleted: the

Deleted: ing
(4) Turn the air conditioning control to the “on” position before testing so the air conditioning 

system is active whenever the engine is running. Place the vehicle in gear 15 seconds after 

engine starting, which is 3 seconds before the first acceleration. At the end of the driving 

schedule, simultaneously switch all the sampling, recording, and integrating from SC03 to HFET, 

including background sampling. Indicate the end of the test cycle in the recorded data. Record 

the measured dynamometer roll revolutions corresponding to the SC03 driving schedule.

(5) Directly following the SC03 driving schedule, operate the vehicle over the HFET driving 

schedule. Turn the vehicle off at the end of the driving schedule and simultaneously stop all 

sampling, recording, and integrating, including background sampling. Indicate the end of the 

test cycle in the recorded data. Record the measured dynamometer roll revolutions 

corresponding to the HFET drive schedule. Turn off the solar heating.

(6) Allow the vehicle to remain on the dynamometer for (10 to 15) minutes after emission 

sampling has concluded. Repeat the testing described in paragraphs (f)(1) through (5) of this 

section and turn off the vehicle’s air conditioner and the solar heating throughout the test run. 

You may adjust the vehicle windows open or closed.

(g) Calculations. (1) Determine the mass of CO2 emissions for each of the two test intervals as 

described in §1066.610.

(2) Calculate the composite mass-weighted emissions of CO2, eCO2-AC17comp, representing the 

average of the SC03 and HFET emissions, in grams per mile using the following equation:

SC03 HFET

CO2-AC17comp

SC03 HFET

0.5 0.5 m m e D D

   

         

 Eq. 1066.835-1

Where:

mSC03 = mass emissions from the SC03 test interval, in grams.

mHFET = mass emissions from the HFET test interval, in grams.

DSC03 = measured driving distance during the SC03 test interval, in miles.

DHFET = measured driving distance during the HFET test interval, in miles.

§1066.839 Highway fuel economy test procedure.

This section describes the procedure for the highway fuel economy test (HFET). This test 

involves emission sampling and fuel economy measurement for certain vehicles as described in 

40 CFR part 86, subpart S, and in 40 CFR part 600. See §1066.801 for further information on 

the driving schedules. Follow the exhaust emission measurement procedures specified in 

§§1066.410 through 1066.430, subject to the following exceptions and additional provisions: 

(a) Perform the HFET immediately following the FTP when this is practical. If the HFET 

procedure starts more than 3 hours after an FTP (including evaporative emission measurements, 

if applicable), operate it over one UDDS to precondition the vehicle. We may approve 

additional preconditioning in unusual circumstances.

(b) Operate the vehicle over the HFET driving schedule for preconditioning. Allow the vehicle 

to idle for 15 seconds (with the vehicle in gear), then start a repeat run of the HFET driving 

schedule and simultaneously start sampling and recording. 

(c) Turn the engine off at the end of the HFET driving schedule and stop all sampling and 

recording, including background. Stop any integrating devices and indicate the end of the test 

cycle in the recorded data.

Deleted: Follow the SC03 driving schedule. 

Deleted: , but leave the vehicle’s windows open

Deleted: [

Deleted: ]

Deleted: (h) Recordkeeping. In addition to the 

information specified in §1066.695, you must record 

the following information for each vehicle tested: 

interior volume, climate control system type and 

characteristics, refrigerant used, compressor type, 

and evaporator/condenser characteristics. ¶
§1066.840 Fuel storage system leak test procedure.

(a) Scope. Perform this test as required in the standard-setting part to verify that there are no 

significant leaks in your fuel storage system.

(b) Measurement principles. Leaks are detected by measuring pressure, temperature, and flow to 

calculate an equivalent orifice diameter for the system. Use good engineering judgment to 

develop and implement leak test equipment. Your leak test equipment must meet the following 

requirements:

(1) Pressure, temperature, and flow sensors must be calibrated with NIST-traceable standards. 

(2) Correct flow measurements to standard reference conditions.

(3) Leak test equipment must have the ability to pressurize fuel storage systems to at least 4.1 

kPa and have an internal leak rate of less than 0.20 standard liters per minute.

(4) You must be able to attach the test equipment to the vehicle without permanent alteration of 

the fuel storage or evaporative emission control systems.

(5) The point of attachment to the fuel storage system must allow pressurization to test system 

integrity of the fuel tank and of fuel lines and vapor lines reaching up to and including the gas 

cap and the evaporative canister. The evaporative system test port available on some vehicles is 

an example of an effective attachment point.

(c) Leak test procedure. Test a vehicle’s fuel storage system for leaks as follows:

(1) Refuel vehicle to 40 % of its nominal fuel tank capacity.

(2) Soak the vehicle for 6 to 24 hours at a temperature between (20 and 30) °C; record this 

setpoint temperature and maintain temperatures throughout the leak test at this setpoint 

temperature within a tolerance ± 2 °C.

(3) Before performing the test, purge the fuel storage system of any residual pressure, bringing 

the system into equilibrium with ambient pressure.

(4) Seal the evaporative canister’s vent to atmosphere and ensure that the vehicle’s purge valve is 

closed.

(5) Attach the leak test equipment to the vehicle.

(6) Pressurize the fuel storage system with N2 or another inert gas to at least 2.4 kPa. Use good 

engineering judgment to avoid overpressurizing the system.

(7) Maintain gas flow through the system for at least 180 seconds, ensuring that the flow reading 

is stable for an effective leak diameter of ± 0.002 inches.

(8) Use the following equation, or a different equation you develop based on good engineering 

judgment, to calculate the effective leak diameter, Deff:

  

2

0.5057

gas

eff

in atmos in atmos

N

7.844

V

d

pp pp

SG T

   

   

  

Where:

deff = effective leak diameter, in inches.

Vgas = volumetric flow of gas, in m3/s.

pin = inlet pressure to orifice, in kPa.

patmos = atmospheric pressure, in kPa.

SGN2 = specific gravity of N2 at 101.325 kPa and 15.5 °C = 0.967

Comment [CAL23]: Equation updated. 

Deleted: D

Deleted: 1

Deleted: 2

Comment [CAL24]: Should we specify that this 

is the SG of N2 compared to air? 

Deleted: atmospheric pressure
T = temperature of flowing medium, in K.

(9) You may perform any number of replicate tests, but all the tests for a vehicle must use the 

same attachment point. The average value of replicate tests is the official result for a given 

vehicle.

(10) You may use special or alternative test procedures as described in 40 CFR 1065.10(c).

(d) Equipment calibration. Use good engineering judgment to calibrate the leak check device.
Subpart J—[Reserved] Deleted: H
Subpart K—Definitions and Other Reference Material 

§1066.1001 Definitions. 

The definitions in this section apply to this part. The definitions apply to all subparts unless we 

note otherwise. Other terms have the meaning given in 40 CFR part 1065. The definitions 

follow:

 Bag 1 means relating to the first 505 s of the FTP cold-start test interval. Note that the 

term bag 1 may also apply to measurement of constituents that are not collected in a bag, such as 

PM and continuously measured THC.

 Bag 2 means relating to the last 867 s of the FTP cold-start test interval.

 Bag 3 means relating to the first 505 s of the FTP hot-start test interval. 

 Bag 4 means relating to the last 867 s of the FTP hot-start test interval, if run. Note that 

bag 2 is generally used in place of bag 4.

 Base inertia means a value expressed in mass units to represent the rotational inertia of 

the rotating dynamometer components between the vehicle driving tires and the dynamometer 

torque-measuring device, as specified in §1066.250. 

 C1-equivalent means a convention of expressing HC concentrations based on the total 

number of carbon atoms present, such that the C1-equivalent of an HC concentration equals the 

concentration multiplied by the mean number of carbon atoms in each HC molecule. For 

example, the C1-equivalent of 10 ppm of propane (C3H8) is 30 ppm. C1-equivalent concentration

values may be denoted as “ppmC” in the standard-setting part. Densities may also be expressed 

on a C1 basis. Note that calculating HC masses from concentrations and densities is only valid 

where they are each expressed on the same carbon basis.

Driving schedule means a series of vehicle speeds that a vehicle must follow during a test. 

Driving schedules are specified in the standard-setting part. A driving schedule may consist of 

multiple test intervals. 

Duty cycle means a set of weighting factors and the corresponding test cycles, where the 

weighting factors are used to combine the results of multiple test intervals into a composite result. 

 FTP means one of the following:

(1) The test cycle consisting of one UDDS as specified in paragraph (a) of Appendix I of 40 CFR 

part 86, followed by a 10-minute soak with the engine off and repeat driving through the first 

505 seconds of the UDDS. See §1066.801(c)(1).

(2) The entire test procedure for measuring exhaust and/or evaporative emissions as described in 

§1066.801(c).

Footprint has the meaning given in the standard-setting part.

 HFET means the test cycle specified in Appendix I of 40 CFR part 600.

 LA-92 means the test cycle specified in Appendix I, paragraph (c), of 40 CFR part 86.

Nonmethane organic gas (NMOG) means the combination of organic gases other than 

methane as calculated in §1066.665. Note that for this part, the organic gases are summed on a 

mass basis without any adjustment for photochemical reactivity.

Parts-per-million (ppm) means ppm on a molar basis. For hydrocarbon concentrations 

including HC, THC, NMHC, and NMOG, ppm means ppm on a C1-equivalent molar basis.

Road-load coefficients means sets of A, B, and C road-load force coefficients that are 

used in the dynamometer road-load simulation, where road-load force at speed v equals A + B·v

+ C·v

2

. 

 SC03 means the test cycle specified in Appendix I, paragraph (h), of 40 CFR part 86.

Deleted: 701

Deleted: phases

Deleted: phases

Deleted: S

Deleted: S

Deleted: S2
 SFTP means the collection of test cycles as given in 1066.801(c)(2).

 Standard reference conditions means the following:

(1) Pressure at 101.325 kPa.

(2) Temperature at 293.15 K.

 Test interval means a period over which a vehicle’s emission rates are determined 

separately. For many standards, compliance with the standard is based on a weighted average of 

the mass emissions from multiple test intervals. For example, the standard-setting part may 

specify a complete duty cycle as a cold-start test interval and a hot-start test interval. 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 weight has the meaning given in §1066.810.

 UDDS means the test cycle specified in Appendix I, paragraph (a), of 40 CFR part 86.

 US06 means the test cycle specified in Appendix I, paragraph (g), of 40 CFR part 86. 

 Unloaded coastdown means a dynamometer coastdown run with the vehicle wheels 

removed from the roll surface. 

 We (us, our) means the Administrator of the Environmental Protection Agency and any 

authorized representatives.

§1066.1005 Symbols, abbreviations, acronyms, and units of measure. 

The procedures in this part generally follow either the International System of Units (SI) or the 

United States customary units, as detailed in NIST Special Publication 811, which we 

incorporate by reference in §1066.1010. See 40 CFR 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 Unit in terms of SI 

base units 

 atomic hydrogen to carbon ratio mole per mole mol/mol 1

A area square meter m2 m2

A vehicle frictional load pound force or newton lbf or N kg·s-2

Am calculated vehicle frictional load pound force or newton lbf or N kg·s-2

a0

intercept of least squares 

regression 

a1 slope of least squares regression 

a acceleration feet per second squared or 

meters per second squared ft/s2

 or m/s2 m·s-2

B vehicle load from drag and 

rolling resistance

pound force per mile per hour 

or newton second per meter lbf/mph or N·s/m kg·s-1·m-1

 ratio of diameters meter per meter m/m 1

 atomic oxygen to carbon ratio mole per mole mol/mol 1

c conversion factor 

C vehicle-specific aerodynamic 

effects

pound force per mile per hour 

squared or newton second 

squared per meter squared

lbf/mph2 or N·s2/m2 kg·m-2

C#

number of carbon atoms in a 

molecule C#

number of carbon 

atoms in a molecule C#

Deleted: phase

Deleted: duration

Deleted: for comparison to an emission

Deleted: phase

Deleted: phase

Deleted: phases

Deleted: standard-setting

Deleted: off

Deleted: 705

Deleted: 710
Cd discharge coefficient 

CDA drag area meter squared m2 m2

Cf flow coefficient 

Cp heat capacity at constant pressure joule per kelvin J/K J·K-1

Cv heat capacity at constant volume joule per kelvin J/K J·K-1

d diameter meters m m 

D distance miles or meters mi or m m

D slope correlation

pound force per mile per hour 

squared or newton second 

squared per meter squared

lbf/mph2 or N·s2/m2 kg·m-2

DF dilution factor 1

h change in height meters m m

s distance traveled during 

measurement interval meters m m

e mass weighted emission result grams/mile g/mi

F force pound force or newton lbf or N kg·s-2

f frequency hertz Hz s-1

fn angular speed (shaft) revolutions per minute r/min 2·π·60-1·m·m-1·s-1

FC friction compensation error horsepower or watt W kg·m2·s-3

FR road load force pound force or newton lbf or N kg·s-2

g gravitational acceleration meters per second squared m/s2 m·s-2

 ratio of specific heats

(joule per kilogram kelvin) 

per (joule per kilogram 

kelvin) 

(J/(kg·K))/(J/(kg·K)) 1

 ambient humidity grams water vapor per 

kilogram dry air

g H2O vapor/kg dry 

air

g H2O vapor/kg dry 

air

I inertia pound mass or kilogram lbm or kg kg 

I current ampere A A

i indexing variable 

IR inertia work rating 

K correction factor 1

Kv calibration coefficient m4·s·K0.5/kg m4·s·K0.5·kg-1

 viscosity, dynamic pascal second Pa·s m-1·kg·s-1

M molar mass gram per mole g/mol 10-3·kg·mol-1

Me effective mass kilogram kg kg

m mass pound mass or kilogram lbm or kg kg 

N total number in series 

n total number of pulses in a series 

p pressure pascal Pa m -1·kg·s-2

pd

saturated vapor pressure at 

ambient dry bulb temperature kilopascal kPa m -1·kg·s-2

PF penetration fraction 

Q flow cubic feet or cubic meter ft3 or m3 m3

Q flow rate cubic feet per minute or cubic 

meter per second ft3

/min or m3/s m3/s

ρ mass density kilogram per cubic meter kg/m3 kg·m-3

R dynamometer roll revolutions revolutions per minute rpm 2·π·60-1· m·m-1·s-1

r ratio of pressures pascal per pascal Pa/Pa 1

r

2 coefficient of determination 

Deleted: M

Field Code Changed
Re# Reynolds number 

RF response factor

RH relative humidity

S Sutherland constant kelvin K K

SEE standard estimate of error 

SG specific gravity

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 

Δt time interval, period, 1/frequency second s s 

U voltage volt V m2·kg·s-3·A-1

v speed miles per hour or meters per 

second mph or m/s m·s-1

V volume cubic meter m3 m3

VP volume percent

x concentration of emission over a 

test interval part per million ppm

y generic variable 

Z compressibility factor Z compressibility 

factor Z

(b) Symbols for chemical species. This part uses the following symbols for chemical species and 

exhaust constituents: 

Symbol Species 

CH4 methane 

CH3OH methanol

CH2O formaldehyde

C2H4O acetaldehyde

C2H5OH ethanol

C2H6 ethane

C3H7OH propanol

C3H8 propane

C4H10 butane

C5H12 pentane

CO carbon monoxide 

CO2 carbon dioxide 

H2O water

HC hydrocarbon

HCHO formaldehyde

N2 molecular nitrogen

NMHC nonmethane hydrocarbon 

NMHCE nonmethane hydrocarbon equivalent 

NMOG nonmethane organic gas

NO nitric oxide 

NO2 nitrogen dioxide 

NOx oxides of nitrogen 

N2O nitrous oxide 

Deleted: -

Deleted: mass

Deleted: kilogram

Deleted: kg

Deleted: kg
O2 molecular oxygen 

OHC oxygenated hydrocarbon

PM particulate matter

THC total hydrocarbon 

THCE total hydrocarbon equivalent 

(c) 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

(d) Subscripts. This part uses the following subscripts to define a quantity: 

Subscript Quantity 

0 reference

abs absolute quantity 

AC17 air conditioning 2017 test interval

act actual or measured condition 

actint actual or measured condition over the speed interval 

adj adjusted

air air, dry

atmos atmospheric 

b base 

bkgnd background

c cold

comp composite

cor corrected

cs cold stabilized

ct cold transient

cUDDS cold-start UDDS

D driven

dew dewpoint

dexh dilute exhaust quantity

dil dilute

e effective 

emission emission specie

error error 

EtOH ethanol

exh raw exhaust quantity

exp expected quantity 

fil filter

final final

flow flow measurement device type

gas gaseous

h hot

HFET highway fuel economy test 

hs hot stabilized

Deleted: mass

Deleted: int ... [11]

Deleted: coastdown
ht hot transient

hUDDS hot-start UDDS

i an individual of a series 

ID driven inertia

in inlet

int intake

init initial quantity, typically before an emission test 

IT target inertia

liq liquid

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 

mix dilute exhaust gas mixture

out outlet

PM particulate matter

record record

ref reference quantity 

rev revolution 

roll dynamometer roll 

s settling 

s slip

s stabilized

sat saturated condition 

SC03 air conditioning driving schedule

span span quantity

sda secondary dilution air

std standard conditions

T target

t throat

test test quantity 

uncor uncorrected quantity 

w weighted

zero zero quantity 

(e) Other acronyms and abbreviations. This part uses the following additional abbreviations and 

acronyms: 

A/C air conditioning

AC17 air conditioning 2017 test interval

ALVW adjusted loaded vehicle weight

ASME American Society of Mechanical Engineers

CFR Code of Federal Regulations 

CFV critical-flow venturi

CNG compressed natural gas

CVS constant-volume sampler

EPA Environmental Protection Agency 

ETW equivalent test weight

EV electric vehicle

Deleted: final

Deleted: final

Deleted: .,

Deleted: si

Deleted: speed interval

Deleted: span

Deleted: span quantity
FID flame-ionization detector 

FTP Federal test procedure

GC gas chromatograph

GEM greenhouse gas emissions model

GHG greenhouse gas (including CO2, N2O, and CH4)

GPS global positioning system

GVWR gross vehicle weight rating 

HEV hybrid electric vehicle

HFET highway fuel economy test

HLDT heavy light-duty truck

HPLC high pressure liquid chromatography

IBR incorporated by reference

LA-92 Los Angeles 1992 driving schedule

MDPV medium-duty passenger vehicle

NIST National Institute for Standards and Technology 

NMC nonmethane cutter

PDP positive-displacement pump

PHEV plug-in hybrid electric vehicle

PM particulate matter

RESS rechargeable energy storage system 

ppm parts per million

SAE Society of Automotive Engineers 

SC03 air conditioning driving schedule

SEA selective enforcement audit

SFTP supplemental federal test procedure

SI International System of Units

SSV subsonic venturi

UDDS urban dynamometer driving schedule

US06 aggressive driving schedule

U.S.C. United States Code 

WWV NIST radio station call sign

(f) This part uses the following densities of chemical species:

Symbol Quantity1,2 g/m3 g/ft3

ρCH4 density of methane 666.905 18.8847

ρCH3OH density of methanol 1332.02 37.7185

ρC2H5OH C1-equivalent density of ethanol 957.559 27.1151

ρC2H4O C1-equivalent density of acetaldehyde 915.658 25.9285

ρC3H8 density of propane 611.035 17.3026

ρC3H7OH C1-equivalent density of propanol 832.74 23.5806

ρCO density of carbon monoxide 1164.41 32.9725

ρCO2 density of carbon dioxide 1829.53 51.8064

ρHC-gas effective density of hydrocarbon - gaseous fuel3 (see 3) (see 3)

ρHCHO density of formaldehyde 1248.21 35.3455

ρHC-liq effective density of hydrocarbon - liquid fuel4 576.816 16.3336

ρNMHC-gas effective density of nonmethane hydrocarbon - gaseous fuel3 (see 3) (see 3)

Deleted: cycle
ρNMHC-liq effective density of nonmethane hydrocarbon - liquid fuel4 576.816 16.3336

ρNMHCE-gas effective density of nonmethane equivalent hydrocarbon -

gaseous fuel3 (see 3) (see 3)

ρNMHCE-liq effective density of nonmethane equivalent hydrocarbon -

liquid fuel4 576.816 16.3336

ρNOx effective density of oxides of nitrogen5 1912.5 54.156

ρN2O density of nitrous oxide 1829.66 51.8103 1

Densities are given at 20 °C and 101.325 kPa.

2

Densities for all hydrocarbon containing quantities are given in g/m3-carbon atom and g/ft3-

carbon atom.

3

The effective density for natural gas fuel and liquefied petroleum gas fuel are defined by an 

atomic hydrogen-to-carbon ratio, , of the hydrocarbon components of the test fuel. ρHCgas = 

41.57·(12.011 + (·1.008)). 4

The effective density for gasoline and diesel fuel are defined by an atomic hydrogen-to-carbon 

ratio, , of 1.85. 5

The effective density of NOx is defined by the molar mass of nitrogen dioxide, NO2.

(g) 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

MH2O molar mass of water 18.01528 1

See paragraph (g)(1) of this section for the composition of dry air.

(h) 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

n nano 10-9

§1066.1010 Reference materials. 

(a) Certain material is 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, the Environmental Protection Agency must publish a notice of 

the change in the Federal Register and the material must be available to the public. All approved 

material is available for inspection at U.S. EPA, Air and Radiation Docket and Information 

Center, 1301 Constitution Ave., NW., Room B102, EPA West Building, Washington, DC 20460, 

(202) 202-1744, and is available from the sources listed below. It is also available for inspection 

at the National Archives and Records Administration (NARA). For information on the 

Deleted: k

Deleted: 0.0

Comment [CAL25]: We also use Δ as a prefix – 

but it does not fit the table. 

Deleted: 710
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. 

(b) Society of Automotive Engineers, 400 Commonwealth Dr., Warrendale, PA 15096–0001, 

(877) 606–7323 (U.S. and Canada) or (724) 776–4970 (outside the U.S. and Canada), 

http://www.sae.org. 

(1) SAE J1263, Road Load Measurement and Dynamometer Simulation Using Coastdown 

Techniques, Revised March 2010, IBR approved for §§1066.301(b) and 1066.310(b).

(2) SAE J1634, Electric Vehicle Energy Consumption and Range Test Procedure, Revised 

October 2012, IBR approved for §1066.501.

(3) SAE J1711, Recommended Practice for Measuring the Exhaust Emissions and Fuel Economy 

of Hybrid-Electric Vehicles, Including Plug-In Hybrid Vehicles, Revised June 2010, IBR 

approved for §§1066.122 and 1066.501.

(4) SAE J2263, Road Load Measurement Using Onboard Anemometry and Coastdown 

Techniques, Revised December 2008, IBR approved for §§1066.301(b) and 1066.310(b).

(5) SAE J2264, Chassis Dynamometer Simulation of Road Load Using Coastdown Techniques, 

Issued April 1995, IBR approved for §1066.320.

(6) SAE J2711, Recommended Practice for Measuring Fuel Economy and Emissions of HybridElectric and Conventional Heavy-Duty Vehicles, Issued September 2002, IBR approved for 

§1066.501. 

(7) SAE J2951, Drive Quality Evaluation for Chassis Dynamometer Testing, Revised November 

2011, IBR approved for §1066.430.

(c) National Institute of Standards and Technology, 100 Bureau Drive, Stop 1070, Gaithersburg, 

MD 20899-1070, (301) 975-6478, www.nist.gov, or inquiries@nist.gov.

(1) NIST Special Publication 811, 2008 Edition, Guide for the Use of the International System of 

Units (SI), March 2008, IBR approved for §§1066.20(a) and 1066.1005.

(2) [Reserved] 

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Comment [CAL26]: New versions is being 

balloted. Update IBR with new revision date. 

Deleted: 

Comment [CAL27]: Revise to current version 

when revision is finalized – late 2013. 

Deleted: .(

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(ii) Use a road-speed modulated fan system that achieves a linear speed of cooling air at the 

blower outlet that is within ±3.0 mph (±1.3 m/s) of the corresponding roll speed when vehicle 

speeds are between 5 and 30 mph (2.2 to 13.4 m/s), and within ±6.5 mph (±2.9 m/s) of the 

corresponding roll speed at higher vehicle speeds. The fan must provide no cooling air for 

vehicle speeds below 5 mph, unless we approve your request to provide cooling during lowspeed operation based on a demonstration that this is appropriate to simulate cooling for in-use 

vehicles. 

(2) For vehicles with GVWR above 14,000 lbs, use a road-speed modulated fan system that 

achieves a linear speed of cooling air at the blower outlet that is within ±3.0 mph (±1.3 m/s) of 

the corresponding roll speed when vehicle speeds are between 5 and 30 mph (2.2 to 13.4 m/s), 

and within ±10 mph (±4.5 m/s) of the corresponding roll speed at higher vehicle speeds. The fan 

must provide no cooling air for vehicle speeds below 5 mph, unless we approve your request to 

provide cooling during low-speed operation based on a demonstration that this is appropriate to 

simulate the cooling experienced by in-use vehicles. We recommend that the cooling fan have a 

minimum opening of 2.75 m2

, a minimum flow rate of 3,600 m3/min at 50 mph, and that it 

maintain a minimum speed profile across the duct, in the free stream flow, of ±15 % of the target 

flow rate. 

(3) If the cooling specifications in this paragraph (b) are impractical for special vehicle designs, 

such as vehicles with rear-mounted engines, you may arrange for an alternative fan configuration 

that allows for proper simulation of vehicle cooling during in-use operation, subject to our 

approval. 

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You may not measure emissions during a practice run 

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For vehicles with GVWR above 14,000 lbs, you must use a 

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pull down mechanism that allows simulation of the actual 

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would see if a loaded vehicle were actually being tested. Use of this mechanism will ensure that 

wheel slip does not occur when trying to accelerate 

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During idle operation, you mayIf you don’t recommend such a cranking procedure, stop 

cranking after 10 seconds, wait for 10 seconds, then start cranking gain for up to 10 seconds. 

You may repeat this for up to three start attempts. Shut off sampling systems and either turn the 

CVS off, or disconnect the exhaust tube from the tailpipe during the diagnostic period. 

Reschedule the vehicle for testing from a cold start. 

(c) Repeat the recommended starting procedure if the engine has a “false start”. 

(2) If the engine stalls during operation other than idle, stop the driving schedule indicator, 

restart the engine, accelerate to the speed required at that point in the driving schedule, reactivate 

the driving schedule indicator, and continue the test. 

(3) Void the test if the vehicle will not restart within one minute. 

§1066.430 Performing emission tests. 
The overall test consists of prescribed sequences of fueling, parking, and driving at specified test 

conditions. 

(a) Vehicles are tested for criteria pollutants and greenhouse gas emissions as described in the 

standard-setting part. 

(b 

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(6) Verify that there are no significant vacuum-side leaks according to 40 CFR 1065.345. 

(7 

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 During a test you may not switch the gains of an analyzer’s analog operational amplifier(s). 

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c) Operate vehicles during testing as follows: 

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(1) Where we do not give specific instructions, operate the vehicle according to your 

recommendations in the owners manual, unless those recommendations are unrepresentative of 

what may reasonably be expected for in-use operation. 

(2) If vehicles have features that preclude dynamometer testing, modify these features as 

necessary to allow testing, consistent with good engineering judgment. 

(3) Operate vehicles during idle as follows: 

(i) For a vehicle with an 

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int speed interval