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SAN ANTONIO, TEXAS 

 

HOUSTON, TEXAS  WASHINGTON, DC

June 25, 2010

Dr. Robert Giannelli and Mr. Christopher Laroo

Environmental Protection Agency

2000 Traverwood Drive

Ann Arbor, MI 48105

SUBJECT: Letter Report for Work Assignment 2-17, EPA Contract EP-C-05-018, under 

SwRI Project 03.14936.17, SwRI Proposal No. 03-59283.

Contract Title: Testing and Analytical Support for Regulation of Motor Vehicles, 

Engines, Fuels, and Fuel Additives

Assignment Title: Review of Partial Flow Sampling Effects on Particulate Matter 

Characteristics

I. EXECUTIVE SUMMARY

A peer review on the feasibility of using partial flow sampling systems (PFSS) for 

particulate matter (PM) collection under transient engine operation was conducted. The Code of 

Federal Regulations (CFR) Part 1065 addressed the majority of issues required to insure good 

practices in PM collection using CVS and/or PFSS under transient testing. Additional

requirements related to PFSS sample flow response time and to the linear regression statistics 

between exhaust flow and PFSS sample flow should be included in the CFR to insure accurate 

operation of the PFSS.

There is a good agreement between the Caterpillar Report Results and Project E-66 

results relative to testing with high efficiency diesel particle filter (DPF), with PM emissions 

level at 10 percent of the 2007 PM standard. Due to the low PM emissions and due to the large 

variability associated with PM measurement, the CVS and the PFSS seemed equivalent.

However, at the near the 2007 PM standard, there was a considerable difference between 

the results included in the Caterpillar Report and the results obtained in Project E-66. The 

Caterpillar Report showed that PM emissions between CVS and PFSS were within 10 percent 

using one engine and one PFSS, and Project E-66 showed that such difference can range from 13 

lower to 67 percent higher than CVS using different cycles and three different PFSS made by 

AVL, Horiba, and Sierra.
Mr. Chris Laroo

Environmental Protection Agency

June 25, 2010

Page 2 of 13

REPORT 03.14936.17

In conclusion, while all the ground work in CFR Part 1065 has been done to make PFSS 

and CVS equivalent under transient testing, there isn’t sufficient independent experimental data 

to support such equivalency, particularly at PM emissions level near the 2007 PM standard. At 

10 percent of the 2007 PM standard or below, PFSS and CVS can give statistically equivalent 

results on PM, particularly when the coefficient of variation (COV) can be as high as 67 percent, 

as determined using the Caterpillar Report for the round robin study (see Appendix A).

II. INTRODUCTION

Particulate matter (PM) collection by partial flow sampling systems (PFSS) is already 

approved by EPA for steady-state testing. As of today, these systems are not approved for onhighway and nonroad transient testing. In 2002, work reported with commercially available 

PFSS [1], such as the AVL SPC, Horiba MDLT, and Sierra BG-2, showed that the response 

time of the sample flow relative to changes in exhaust flow was slow -- on the order of one 

second. When the PFSS ran in a look-ahead mode, where the exhaust signal of a particular 

transient cycle was prerecorded and anticipated to eliminate the lag in response time, the AVL 

SPC and Horiba MDLT gave improved PM emissions results to within less than 10 percent of 

that of the CVS. Furthermore, when the BG-2 was replaced with a prototype BG-3 having a 

fast response sample flow of better than 300 ms, the PM emissions changed from being 20, 22, 

and 42 percent below CVS using the BG-2, to being 0, 3, and 12 percent above CVS using the 

prototype BG-3, for the Federal test procedure (FTP) transient cycle, nonroad transient cycle 

(NRTC), and European transient cycle (ETC), respectively. One of the most important 

conclusions of the 2002 study was that the PFSS requires a fast response sample flow of less 

than 300 ms, before it can be considered for transient testing. The use of a look-ahead function 

with a pre-recorded signal was not acceptable to EPA and the Engine Manufacturers 

Association (EMA).

In 2006, as a part of Project E-66 Phase 3 [2], an improved version of the three 

commercially- available PFSS were evaluated, shown below, besides two other prototype 

PFSS:

• AVL SPC

• Horiba MDLT

• Sierra BG-3

• Cummins PFSS (prototype)

• Sensors MPS (prototype)

In Project E-66 Phase 3, all commercially available systems tested met the sample flow 

response time criteria of less than 300 ms. In addition, the commercially available PFSS were 

tested at similar dilution parameters to that of the CVS using guidance from Project E-66 

Phases 1 and 2 [3,4]. Results from Project E-66 Phase 3 showed no statistically significant 

difference in the PM emissions performance of PFSS, compared to CVS, when the engine was 

equipped with a diesel particle filter (DPF), and the PM emissions were at 10 percent of the 

2007 standard. However, when the PFSS units were used for engine exhaust treated with the 

DPF with Bypass at an approximate PM emission level of 80 percent of the 2007 standard, the 

PM emission results were not consistent. Under transient engine operation over the FTP and 
Mr. Chris Laroo

Environmental Protection Agency

June 25, 2010

Page 3 of 13

REPORT 03.14936.17

NRTC, the MDLT and BG-3 gave higher PM emissions results than that of the CVS. The PM 

emissions using the MDLT was in the range from 30 percent to 69 percent higher, and it was 21 

to 33 percent higher with the BG-3 for the FTP and NRTC, respectively. The AVL SPC gave 

PM results to within one percent of CVS for the FTP, and it was 13 percent lower with the 

NRTC. Additional work with the AVL SPC showed an improved comparison between the SPC 

and CVS when the dilution parameters were matched. 

Project E-66 Phase 3 concluded that commercially available PFSS meet the criteria 

required on sample flow response time and proportionality with exhaust flow, and further 

improvement to the comparison with CVS could be achieved by tightening the dilution 

parameters under which both the CVS and the PFSS would operate. 

Tightening of dilution and sampling parameters in the Code of Federal Regulations Title 

40, Part 1065, at the recommendation of Project E-66 [2,3,4], should provide some significant 

benefit to the feasibility of using PFSS under transient testing, as compared to the CVS. The 

purpose of this report is to address issues requested by EPA relative to the following tasks:

• Task 1. Comment on the ability of the limits set in 1065.140(e) and 1065.170(c)(1)(vi) 

to control PM formation characteristics to minimize CVS to CVS, PF to PF, and CVS 

to PF variability, noting that setting these limits was based on the outcome of CRC E66, which showed that these parameters have significant effect on PM formation.

• Task 2. Comment on the attached document from Sierra showing the results of the 

Sierra BG-3 test vs. the CVS at two different laboratories on 6 different engines. Note 

that both the PF and CVS measurement systems were compliant with 40 CFR Part 

1065, including 140(e), 1065.170(c)(l)(vi), and 1065.545. This data was used by EPA to 

justify the allowance for the use of partial flow for transient PM measurement and the 

reviewer should comment on this as well.

• Task 3. Comment on the ability of 1065.545 to determine whether or not a partial flow 

sampling system maintains sampling proportionality over the course of a transient test, 

keeping in mind that the same check in 1065.545 is used to determine proportionality 

for CVS sampling systems.

• Task 4. Comment on whether or not PF flow systems will produce PM emission results 

that are comparable to CVS systems over transient test cycles.

III. REVIEW

Task 1

CFR Part 1065.140(e) and 1065.170(c) address the tightening of various parameters that 

can have a profound impact on PM emissions, as shown in CRC Project E-66 Phases 1, 2, and 3. 

Parameters that are now defined and specified in the CFR are:

• sample probe transfer line length and insulation before dilution, (< 26 cm insulated or as 

short as possible)
Mr. Chris Laroo

Environmental Protection Agency

June 25, 2010

Page 4 of 13

REPORT 03.14936.17

• dilution air temperature (25°C±5°C)

• residence time (1 sec to 5 sec, with minimum of 0.5 second in secondary dilution)

• dilution ratio (minimum range of 5 to 7, with minimum of 2 in primary dilution)

• filter face temperature (47°C ± 5°C)

• filter face velocity (100 cm/sec)

• filter media (Teflon Membrane, highly recommended)

• filter collection efficiency

• filter size (circular, 46.5±0.6 mm in diameter, with > 38 mm exposed diameter)

• filter handling (use of cassette, seal or cover before return to stabilization chamber)

The tightening and specifications of the above parameters should provide significant 

improvements to PM sampling practices and minimize CVS to CVS, PFSS to PFSS, and CVS to 

PFSS variability and accuracy, based on the current stage of knowledge. However, more 

independent verifications of how these parameters improve the relationship between CVS and 

PFSS are recommended. 

Task 2

EPA submitted a document to SwRI from Caterpillar showing PM emissions comparison 

between a BG-3 and a CVS at Caterpillar and West Virginia University using a total of five 

engines. One engine meets the 2004 PM standard, and four engines equipped with catalyzed 

diesel particle filters (DPF) meet the 2007/2010 on-highway PM standard. One of the engines 

was equipped with a bypass to elevate the PM emissions level to near the 2007 PM standard.

The round robin testing for engines with DPF, included in the Caterpillar Report, show 

that the coefficient of variation (COV) based on average PM emissions can range from 14 

percent to 67 percent. The COV was only provided in the Caterpillar Report as a percent of the 

standard, and the above COV was recalculated to determine the COV based on the average value 

measured. The COV for the BG-3 was 67 percent and the COV for the Caterpillar CVS was 46 

percent. These COVs are within the range of the COVs obtained with other laboratories. So, with 

such a high variability in measurement at such a low level, it is difficult to discern differences 

between the performance of a PFSS and a CVS. This is consistent with Project E-66 findings 

under similar PM emissions levels.

At near the PM standard level, the report mentioned that, on average, the CVS and the 

BG-3 were within less than 10 percent using the NRTC. However, we don’t know if this 

performance will be consistent if other engine cycles were used, as shown in Project E-66 Phase 

3. In addition, the Caterpillar Report did not provide any information on insuring exhaust mixing 

prior to PM sampling from the exhaust pipe when the bypass was used. 

The Caterpillar Report does not include all the details of testing for a good peer review 

evaluation. It does not show results in relation to the T-Test and the F-Test performed. It simply 

states that the systems passed the T-Test and the F-Test, and there was not sufficient information 

in the report to reproduce such results. It mainly shows a graphical representation of the data, 

except in the round robin case. 
Mr. Chris Laroo

Environmental Protection Agency

June 25, 2010

Page 5 of 13

REPORT 03.14936.17

Task 3

CFR Part 1065.545, as it applies to partial flow, specifies a standard error of estimate 

(SEE) of less or equal to 3.5% at the mean flow in order to demonstrate proportionality between 

exhaust flow and PFSS sample flow. The SEE alone is not sufficient. It is important to specify at 

least a coefficient of determination (R2) to demonstrate linearity. In the 2006 work [2], all 

commercially-available PFSS met an R2 of better than 0.985, even without removing five percent 

of the data. It is highly recommended that an R2 be specified to be > 0.98, as it applies to the 

correlation between exhaust flow and PFSS sample flow. It is important to note that ISO 16183 

specifies a SEE, R2, and intercept. To eliminate the requirement for intercept, one can force the 

regression to go through zero to ensure no bias near the zero intercept. Thus, it is recommended 

that an R2 of 0.98 or better be required using a regression line that is forced through zero, along 

with the 3.5 percent SEE requirement. 

Another issue that was not mentioned in the CFR is the response time of the sample flow 

of the PFSS. While all three commercially-available PFSS discussed above meet the response 

time of 300 ms or better, it is important that this requirement be specified in the CFR, either 

through some defined procedure, or be stated as a PFSS manufacturer requirement. 

The above two recommendations should not really stall any progress made with the 

current commercially available PFSS since they all already meet them. However, including the 

above recommendations in the CFR will eliminate future less capable systems from being used 

as official PFSS.

Task 4

Over the last decade, commercially available PFSS have improved drastically, 

particularly in sample flow response time changes relative to changes in exhaust flow while 

maintaining proportionality and a short lag time of less than 300 ms. This achievement made the 

PFSS fundamentally acceptable to transient testing in light of the work performed in 2002 [1]. 

The tightening of PM sampling procedures that are implemented in CFR Part 1065 significantly 

improve the quality of PM sampling and minimize variability in PM filter mass collection 

whether it applies to CVS or PFSS. However, the drastic reduction in PM emissions with the use 

of DPFs to levels at or below 10 percent of the 2007 PM standard continue to make PM 

collection and weighing a difficult process, resulting in major variability.

With current technology engines well below the 2007 PM standard, it will be difficult to 

discern any differences between CVS and PFSS PM emissions performance. Thus, the PFSS is 

suitable to be used in this capacity, and a two standard deviation COV at the 95 percent 

confidence level can be as high as 120 to 140 percent among laboratories, and as high as 100 

percent for repeated measurements. This applies to both CVS and PFSS at PM emissions level at 

or below 10 percent of the 2007 PM standard. This is based on the round robin results and 

Project E-66.

At levels near the 2007 PM standard, Project E-66 suggests that PM emissions using 

PFSS can range from 13 percent lower to 69 percent higher than that of the CVS, depending on 
Mr. Chris Laroo

Environmental Protection Agency

June 25, 2010

Page 6 of 13

REPORT 03.14936.17

the PFSS manufacturer and the cycle tested. Recent work by Caterpillar suggests that such 

differences can be as much as 10 percent using the BG-3 with a Caterpillar C-9 engine under the 

NRTC. Furthermore, it was stated in the Caterpillar Report that the PFSS and the CVS met the 

T-test and the F-test, specified in Part 1065. SwRI, however, was not able to verify these results 

based on the Caterpillar Report nor was able to discern that exhaust mixing was achieved when 

the bypass was used.

While the PFSS meet all the fundamental criteria required for PM measurement under 

transient testing, independent verification of the performance of the PFSS compared to the CVS 

is recommended, particularly at levels near the 0.01 g/hp-hr standard, where engines may fail the 

standard. 

III. REFERENCES

1. Khalek, I.A, T. Ullman, S. Shimpi, C. Jackson, B. Dharmawardhana, W. Silvis, N. 

Kreft, N. Harvey, D. Munday, Y. Yamagishi, R. Graze, J. Smitherman, and J. Adkins, 

“Performance of Partial Flow Sampling Systems Relative to Full Flow CVS for 

Determination of Particulate Emissions under Steady-State and Transient Diesel 

Engine Operation,” SAE Paper No. 2002-01-1718, 2002.

2. Khalek, I.A., “2007 Diesel Particulate Measurement Research,” CRC Project E-66 

Phase 3 Final Report to CRC, crcao.org, May 2007.

3. Khalek, I.A., “2007 Diesel Particulate Measurement Research,” CRC Project E-66 

Phase 1 Final Report to CRC, crcao.org, May 2005.

4. Khalek, I.A., “2007 Diesel Particulate Measurement Research,” CRC Project E-66 

Phase 1 Final Report to CRC, crcao.org, May 2006.

Prepared by: Approved by:

Imad A. Khalek, Ph.D Jeff J. White

Program Manager Director

Department of Emissions R&D Department of Emissions R&D

DEPARTMENT OF EMISSIONS RESEARCH AND DEVELOPMENT

ENGINE, EMISSIONS AND VEHICLE RESEARCH DIVISION

This report shall not be reproduced, except in full, without the written approval of Southwest Research Institute®

Results and discussion given in this report relate only to the test items described in this report.

.

/sat

 
Mr. Chris Laroo

Environmental Protection Agency

June 25, 2010

Page 7 of 13

REPORT 03.14936.17

APPENDIX A

Sierra Instruments Model BG-3 vs. CVS Multiple Engine Correlation Study 

Forward:

In 2006, Sierra Instruments Inc. recognized that demonstration of correlation of the 

Model BG-3 transient partial flow sampling system to full-flow CVS systems for particulate 

matter (PM) sampling and gravimetric measurement, per Parts 86, 1065, et al., was a necessary 

step toward acceptance of the unit as a certification-grade device. With input from technical 

partner Caterpillar Inc., a series of correlation tests were defined. In all, 120 pairs of 

simultaneously obtained test data were taken at West Virginia University (WVU) and at 

Caterpillar Inc in Part 1065-compliant CVS-equipped test cells. The testing was conducted 

between March, 2008 and April, 2009.

The engines and after-treatment systems used are shown below in Table 1. Testing was 

performed on both on-highway and non-road engines on the heavy-duty FTP or non-road 

transient cycle (NRTC) as required for certification of the engine types tested. In order to 

provide a representative mix of EGR and non-EGR equipped engines from various 

manufacturers, engines from John Deere, Cummins and Caterpillar were tested, producing cycle 

PM levels ranging from approximately 0.5 to 100 milligrams/hp-hr.

 

TABLE 1, TEST PLAN SUMMARY FOR BG-3 –CVS CORRELATION STUDY

Manufacturer Model

Test 

Lab Use Cycle

PM 

Limit Emissions abatement

Cummins ISX 

565

WVU On-road FTP 2004 EGR

Deere 6081 WVU Off-road NRTC Tier 

IV

CCRT (added for test)

Cat C-11 Cat On-road FTP 2007 CCRT

Cat C-9 Cat Off-road NRTC Tier 

IV

CCRT (added for test)

Cat C-9 Cat Off-road NRTC N/A CCRC w/ Bypass 

(added for test)

Cat C-13 Cat On-Road FTP 2007 Production DPF

The Deere engine was a Tier II engine equipped with CCRT to achieve Tier IV NRTC 

cycle PM limits. The Caterpillar C-11 was a MY2004 engine equipped with a CCRT and which 

is currently the heavy duty diesel industry round-robin test engine. The Caterpillar C-9 engine is 

used as a mule by Caterpillar for test measurement method development at their engine 

development center. The C-9 was also equipped with CCRT technology and included an 

engineered bypass for a portion of the tests. The bypass was added specifically to evaluate the 

correlation of the BG-3 to the CVS at emissions levels approaching the 2007/2010 on-highway 

engine PM emissions limits.
Mr. Chris Laroo

Environmental Protection Agency

June 25, 2010

Page 8 of 13

REPORT 03.14936.17

T he testing included a 10x repetition of the heavy duty diesel engine transient cycle 

certification procedure. One cold and one hot test cycle were obtained per day for a minimum of 

10 cold-hot repeats per engine. These results were weighted as per 40CFR Part 86 requirements 

for engine certification (1/7*Cold Result, g/hp-hr + 6/7*Hot Result, g/hp-hr = Weighted Cycle 

Emissions. g/hp-hr). Paired-t and F-test statistical analysis was subsequently performed on the 

weighted test results to determine acceptability at 90% confidence level per Part 1065.12. 

Maintaining consistency between BG-3 and CVS specific to critical sampling system setup 

parameters such as filter face velocity, dilution ratio, residence time, filter temperature and 

dilution air temperature was actively pursued to maintain the technical integrity of the correlation 

study. All aforementioned parameters were maintained within 40CFR Part 1065-required limits.

Correlation Testing Results

The initial phase of testing was performed at the West Virginia University Center for 

Alternate Fuels, Engines and Emissions, Morgantown, West Virginia (WVU). Graphs #1 and 

#2, below, denote cold-hot cycle-weighted results on the Cummins and Deere engines, 

respectively for run days 1-10. It should be noted that post-test analysis of the Cummins engine 

day #5 gaseous emissions results showed significant within-day increases in the hot test cycle 

hydrocarbon (+26.2%) and carbon monoxide (+3.7%) emissions (directional indicators for PM), 

relative to results from Day 4 and Day 6, that were reflected in the BG-3 results (+12.7%) but not 

from the CVS (+1.37%). A weighing error specific to the CVS filter is suspected. This analysis 

questions only the CVS result from Day 5 of this series. The graph below includes the Day 5 

results for completeness. All engines in this program were able to complete their prescribed test 

cycles in accordance with the speed and torque regression statistics required by Part 1065 and 

Part 86. BG-3 Standard Error of Estimate (%SEE) results were well below the 3.5% limit 

required by Part 1065 for all runs at both WVU and at Caterpillar.

GRAPH 1- BG-3 VS. CVS CORRELATION RESULTS, CUMMINS ISX 565 ONHIGHWAY ENGINE, WVU DATA

BG-3 vs CVS Cold-Hot Results, Cummins Engine, FTP Cycle

0

20

40

60

80

100

120

1 2 3 4 5 6 7 8 9 10

Run Set #

PM, mg/hp-hr

CVS, mg/hp-hr

BG-3, mg/hp-hr
Mr. Chris Laroo

Environmental Protection Agency

June 25, 2010

Page 9 of 13

REPORT 03.14936.17

GRAPH 2- BG-3 VS. CVS CORRELATION RESULTS, DEERE 8.1L ENGINE W/ 

CCRT, WVU DATA

The second phase of correlation testing was performed at the Caterpillar Technical 

Center, Mossville, Illinois, in a CVS test cell with a fully 1065 compliant particulate sampling 

system. The C-11 industry (EPA-EMA) round robin engine with CCRT was at Caterpillar for 

inter-lab comparison testing at that time. It was considered an excellent candidate for BG-3-

CVS correlation testing due to the number of labs having already tested the engine, including 

EPA. Graph 3 shows the cold-hot weighted results from the C-11 tests at Caterpillar. The 

variability in results shown in Graphs 2, 3, 4 and 6 are dominated by uncertainties in the filter 

weighing process, coupled with engine and CCRT-based day-to-day variability. This level of 

variability is an expected outcome when measuring PM, using approved gravimetric methods, 

from engines operating at between 5 and 20% of the 2007 PM standard. There were no 

emissions system or engine setup changes made during the course of the test and test filters were 

re-weighed to verify PM mass results. 

Table 2 compares BG-3 and Caterpillar CVS data against results obtained by participants 

in the EPA-EMA round-robin inter-lab comparison program. This chart includes the coefficient 

of variance (1std dev/mean) relative to the 2007/2010 particulate standard. This comparison 

underscored the correlation for both sample mean and variance values from the Caterpillar CVS 

and BG-3 versus a broader population of test labs from testing a common engine and aftertreatment package. 

BG-3 vs CVS Cold-Hot Results, Deere Tier II Engine w/ DPF, NRTC Cycle

0

0.5

1

1.5

2

2.5

3

1 2 3 4 5 6 7 8 9 10

Run Pair #

PM, mg/hp-hr

CVS, mg/hp-hr

BG-3, mg/hp-hr
Mr. Chris Laroo

Environmental Protection Agency

June 25, 2010

Page 10 of 13

REPORT 03.14936.17

GRAPH 3- BG-3 VS. CVS CORRELATION RESULTS, C-11 ENGINE W/ CCRT, 

CATERPILLAR DATA

TABLE 2- COMPARISON OF BG-3 AND CATERPILLAR CVS MEAN AND % 

COEFFICIENT OF VARIANCE (COV) RESULTS WITH TEST LABS 

PARTICIPATING IN THE C-11 ROUND-ROBIN ENGINE STUDY.

Lab

Cold/Hot 

PM, g/hphr

COV Expressed 

as % of 2010 PM 

limit

A .0012 7.0

B .0007 1.0

C .0010 3.0

D* .003 10.13

A2** .0031 20.2

E .0007 4.49

F .0007 2.08

Cat CVS .0010 4.58

BG-3 .00115 7.66

*-Lab used incorrect filter media

**Reran using denormalized FTP test cycle; labs listed after lab A2 ran the denormalized cycle

 BG-3 vs. CVS, Cold-Hot Weighted Results, C-11 R-R Engine, FTP Cycle 

0.0

0.5

1.0

1.5

2.0

2.5

3.0

1 2 3 4 5 6 7 8 9 10

Run #

PM, mg/hp-hr

CVS, mg/hp-hr

BG-3, mg/hp-hr
Mr. Chris Laroo

Environmental Protection Agency

June 25, 2010

Page 11 of 13

REPORT 03.14936.17

GRAPH 4- BG-3 VS. CVS CORRELATION RESULTS, C-9 ENGINE W/ CCRT, 

CATERPILLAR DATA

During testing, questions regarding the BG-3 to CVS correlation at PM levels 

approaching the 2007/2010 standard were raised, essentially due to the disparity in PM levels 

generated by the selected engines relative to both the on-highway 2007/2010 and non-road Tier 

IV emissions standards. The results found on Graph 5 were obtained during BG-3 to CVS 

correlation testing from a C-9 with an engineered 17.25mm fixed bypass installed around the 

CCRT, selected to yield an emissions level of approximately 85% of the 2007/2010 standard. 

The engine was operated on the NRTC for this correlation exercise. Comparing the paired 

results from this test sequence showed that 9 out of 10 cold-hot BG-3 results are within less than 

10% of the corresponding CVS result. Reviewing this same paired dataset using a tighter 

comparison standard, 8 out of 10 of the cold-hot BG-3 results were within 6% of their CVS coldhot cohorts. This agreement underscores the correlation integrity across the anticipated range of 

PM levels to be certified (or re-certified) using Part 86 or Part 1065 methods on NRTC or FTP 

cycles.

Graph 6 summarized cold-hot results obtained on the 2008 Caterpillar C-13 engine. As 

previously stated, elevated levels of variability from both measurement systems are expected 

when sampling particulate matter at 5% of the 2007/2010 PM emissions limit. In the case of the 

C-13, net filter loadings of less than 5 micrograms were routinely measured from both the CVS 

and BG-3.

 BG-3 vs. CVS Cold-Hot Weighted Results, Tier III C-9 w/ DPF

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

2.00

1 2 3 4 5 6 7 8 9 10

Run #

PM, mg/hp-hr

CVS, mg/hp-hr

BG-3, mg/hp-hr
Mr. Chris Laroo

Environmental Protection Agency

June 25, 2010

Page 12 of 13

REPORT 03.14936.17

GRAPH 5- BG-3 VS. CVS CORRELATION RESULTS, C-9 ENGINE W/ PARTIALLY 

BYPASSED CCRT, CATERPILLAR DATA

GRAPH 6- BG-3 VS. CVS CORRELATION RESULTS, 2008 C-13 ENGINE, 

CATERPILLAR DATA

BG-3 vs. CVS Cold-Hot Weighted Results, C-9 with Bypassed DPF, NRTC

0.00

2.00

4.00

6.00

8.00

10.00

12.00

1 2 3 4 5 6 7 8 9 10

Run Number

PM, mg/hp-hr

CVS, mg/hp-hr

BG-3, mg/hp-hr

BG-3 vs. CVS Cold-Hot Weighted Results, C-13 Engine, FTP Cycle 

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1 2 3 4 5 6 7 8 9 10

Run #

PM, mg/hp-hr

CVS, mg/hp-hr

BG-3, mg/hp-hr
Mr. Chris Laroo

Environmental Protection Agency

June 25, 2010

Page 13 of 13

REPORT 03.14936.17

In conclusion, based on test results from this initiative, the Sierra BG-3 passes paired-t 

and F-test results for equivalent means and equivalent variances, respectively for cold-hot cycle 

weighted transient test results per Part 1065.12, on engines ranging from approximately 1/20 to 

10x the applicable limit for 2007 on-road and Tier IV off-road engine certifications. Further, 

based on test results from an engine with a CCRT and engineered partial bypass, the Sierra BG-3 

passes paired-t and F-test results for equivalent means and equivalent variances, respectively for 

cold-hot cycle weighted transient test results per Part 1065.12 at PM emissions levels of 

approximately 85% of the applicable limit for 2010 on-road, and approximately 60% of the Tier 

IV off-road standard.