INGAA Emissions Data Collection: 

Carbon Monoxide Emissions from Natural Gas-Fired 

Two-Stroke Cycle and Four-Stroke Cycle Lean Burn 

Reciprocating Internal Combustion Engines 

Emissions Data for Reciprocating Internal Combustion Engine 

National Emission Standard for Hazardous Air Pollutants 

(RICE NESHAP): 2010 Amendments for Existing Engines 

Technical Report: 

CO Emissions Data for Lean Burn Engines 

and MACT Floor Analysis 

Prepared for: 

Interstate Natural Gas Association of America 

10 G Street NE, Suite 700 

Washington, DC 20002 

Prepared by: 

Innovative Environmental Solutions, Inc. 

P.O. Box 177 

Cary, IL 60013 

April 2010
Technical Report: Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 

i 

TABLE OF CONTENTS 

1. Project Objectives and Data Sources .......................................................................................... 1 

2. MACT Floor Determination: Basis and Analysis Approach ...................................................... 3 

2.1. Identifying Best Performing Units....................................................................................... 4 

2.2. MACT Floor Variability ...................................................................................................... 7 

3. Data Summary: Four-Stroke Cycle Lean Burn Engines ............................................................. 9 

3.1. Comparison with EPA 4SLB Data....................................................................................... 12 

3.2. Variability and Factors that Influence 4SLB CO Emissions ............................................... 12 

4. Data Summary: Two-Stroke Cycle Lean Burn Engines ............................................................. 15 

4.1. Overview of MACT Floor Engines and 2SLB Engine Subcategories ................................ 20 

4.2. Emissions Variability Assessment ...................................................................................... 22 

4.3. Discussion of CSU 2SLB Engine Data and NOx – CO Tradeoff........................................ 23 

5. Conclusions and Recommendations............................................................................................ 28 

Appendices ........................................................................................................................................ 30 

Appendix A: 4-stroke Lean Burn Engine Data 

Appendix B: 2-stroke Lean Burn Engine Data 
Technical Report: Natural Gas-Fired Engine Emissions Data for MACT Floor 

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1.0 Project Objectives and Data Sources 

A rule to amend the Reciprocating Internal Combustion Engines (RICE) National 

Emission Standards for Hazardous Air Pollutants (NESHAP) was proposed on March 5, 

2009. The proposed rule addresses standards for existing major source engines 500 

horsepower (hp) and smaller and existing area source engines of all sizes. The Interstate 

Natural Gas Association of America (INGAA) is a trade association of the interstate 

natural gas transmission industry, and INGAA member companies operate stationary 

natural gas-fired spark ignition internal combustion (IC) engines. These engines are 

installed at compressor stations along the pipelines to transport natural gas to residential, 

commercial, industrial and electric utility customers. INGAA submitted comments on 

the proposed rule on June 3, 2009, and a primary concern was the basis of proposed 

emission standards for gas-fired IC engines. This concern was primarily due to 

deficiencies in the data used to establish emission standards for a regulation that will 

impact thousands of engines. These deficiencies include both a lack of emissions data 

and data quality issues. INGAA’s concerns are detailed in its comments, which are 

available in the rule docket (Docket Document No. EPA-HQ-OAR-2008-0708-0155). 

The proposed rule addresses existing engines; thus, emissions data for existing equipment 

are of interest. INGAA conducted an emissions data collection effort, gathering data 

from its members to supplement the emissions data available for the rulemaking. The 

proposed rule includes carbon monoxide (CO) emission standards for lean burn engines, 

with CO emissions a surrogate for HAP emissions. Formaldehyde emission standards 

were proposed for rich burn engines. CO testing has been completed for many engines, 

typically associated with NOx compliance tests. Thus, it was anticipated that CO data 

would be available for lean burn engine categories. Formaldehyde testing is relatively 

rare, but formaldehyde data were also solicited. The objective of this effort was to: 

• Assess the availability of emissions data for the three primary natural gas-fired IC 

engine subcategories: 2-stroke lean burn (2SLB), 4-stroke lean burn (4SLB), and 4-

stroke rich burn (4SRB) engines; 

• Collect available emissions data, including CO data for 2SLB and 4SLB engines and 

formaldehyde data for 4SRB engines; 

• Compile and organize the data into a report for transmittal to EPA; and, 

• Review and analyze the data to assess implications for the emission standard, 

including the basis for the minimum standard required under the Clean Air Act. This 

minimum standard is referred to as the “MACT floor”. The Clean Air Act requires 

that the emission standard for existing units be based on the average emission 

limitation achieved by the best performing 12% of engines in a subcategory. In 

recent Court cases, it has been clearly delineated that NESHAP standards can take 

into account emissions variability, which considers emissions at adverse operating 

conditions that are reasonably likely to recur. Thus, INGAA analysis considered the 

MACT floor and emissions variability. As discussed in Sections 3, 4, and 5, this 

review concludes emissions variability warrants CO standards over 370 ppmv (at 

15% O2) for both 4SLB and 2SLB engine subcategories and specific 

recommendations are discussed in those sections. 
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Since CO data are relatively common, INGAA members provided data summaries for 

review and compilation. A significant amount of CO data were collected for lean burn 

engines, especially 2SLB engines, which are the most common units used in gas 

transmission. Formaldehyde data for 4SRB engines were generally not available. Since 

formaldehyde data are sparse, INGAA understands that other efforts are underway to test 

4SRB engines and recommends that EPA consider those data for establishing 4SRB 

standards. 

This report presents the results of the INGAA emissions data collection effort and 

provides CO emissions data for 2SLB and 4SLB engines. A summary of the engine 

types and collected data presented in this report includes: 

• CO emissions test data from over 400 natural gas-fired engines, including 85 fourstroke lean burn engines and 325 two-stroke lean burn engines; 

• Over 3,000 test runs and 1,000 individual tests (i.e., 3 test runs are common for many 

compliance tests); 

• Most engines are larger than 500 hp, consistent with the population of existing gas 

transmission engines, but test data are included for engines 500 hp and smaller. 

Engines with multiple tests and multiple test conditions across the operating envelope are 

of special interest for assessing emission variability. Data review indicates that many 

engines had four or fewer test runs (i.e., a single “test” often includes 3 or 4 “test runs” at 

a single operating condition). The number of test runs per engine varied from one to over 

fifty. Based on Court decisions, EPA’s approach for standard development assesses 

variability on emissions from the best performing 12% of sources (i.e., “MACT floor 

units”). Thus, it is informative if MACT floor units have emissions data at multiple test 

conditions and across the operating range. 

In addition, INGAA and its members have actively engaged in other emissions testing 

programs for over 15 years. These include projects at the Colorado State University 

(CSU) Engines and Energy Conversion Laboratory (EECL) engine testbed, which 

includes a 2SLB engine common in gas transmission. For example, in 1999 EPA funded 

testing on the CSU 2SLB engine to develop data for the original RICE MACT standard, 

and gas transmission stakeholders participated in that effort through the Pipeline 

Research Committee International (PRCI) and Gas Research Institute (GRI). Compared 

to engines in field operations where tests are predominantly high load compliance tests, 

this 2SLB engine provides data over a broader range of standard operating conditions. 

As noted in the June 2009 INGAA comments, these tests may provide data to assess 

emissions variability. Thus, data from the CSU 2SLB engine are included in this report, 

and the test data from the 1999 EPA study are supplemented with additional CSU data. 

EPA also funded 4SLB engine tests at CSU. Unfortunately, that engine was sited at the 

test bed for only a sort time and additional data beyond the EPA program are not 

available for the 4SLB engine. The EPA test data are already in the rule docket. The 

CSU 2SLB data are discussed in Section 4. In addition, 2SLB data from recent testing 

completed by compression service providers is included in this report, as discussed in 

Section 4. 
Technical Report: Natural Gas-Fired Engine Emissions Data for MACT Floor 

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While this is primarily a “data report”, the document includes analysis and discussion that 

provide a technical summary of the collected data. In addition to this introduction, 

Section 2 of this report discusses the process associated with the “MACT floor” analysis 

based on INGAA’s understanding of Clean Air Act requirements and recent Court cases. 

This “process” includes identifying the best performing 12% of engines and assessing 

variability from that engine population. Section 3 presents summary data and tables for 

the 4SLB engine subcategory. Section 4 presents summary data and tables for the 2SLB 

engine subcategory. Section 5 summarizes the results and conclusions. Detailed data 

and quality assurance information are provided in appendices. Appendix A provides data 

tables for the 4SLB engines and Appendix B provides data tables for the 2SLB engines. 

The table format includes a unique engine identifier, test run identifier, engine 

information (e.g., make, model, type), test information (e.g., test date, engine load), 

emissions data, and averages of multi-run tests if more than one test-run is completed at a 

single operating condition (e.g., compliance tests). In addition to these appendices, 

supplementary information such as test reports and test validation documentation for 

engines that populate the MACT floor will be provided to EPA separately. 

2.0 MACT Floor Determination: Basis and Analysis Approach 

Appendices A and B provide the data from the INGAA collation of reciprocating engine 

emission tests. Appendix A presents 4SLB data and Appendix B presents 2SLB data. 

For tests (e.g., compliance tests) with multiple test runs (typically three runs) at the same 

engine operating condition, the average of the runs is presented and each test run is 

shown as a separate row. These data are summarized in Sections 3 and 4, and INGAA 

includes analysis and discussion of our perspective of this dataset, including 

identification of the “MACT floor” and consideration of variability. This section 

discusses the basis for the analysis in this report. 

Section 112(d)(3)(A) of the Clean Air Act requires that emission standards for existing 

engines be based on “the average emission limitation achieved by the best performing 

12% of the existing sources...”. This emission level is typically referred to as the 

“MACT floor”. As discussed below, decisions from the D.C. Circuit Court support the 

consideration of variability in establishing the emission standard. The analysis and 

discussion in Sections 3 and 4 focus on the engines that comprise the MACT floor with 

data for all engines in the Appendices. The methodology for defining the MACT floor 

engines is discussed below. 

For this analysis, INGAA considered the Clean Air Act, Court decisions regarding the 

basis for determining Section 112(d) emission standards, EPA’s analysis for existing 

compression ignition engines in the March 3, 2010 RICE NESHAP amendments, and 

recent EPA MACT floor analysis from other NESHAP rules. In addition, this analysis is 

supplemented by INGAA’s understanding of reciprocating engine emissions, the inherent 

variability in emissions from natural gas-fired reciprocating engines, and operating 

conditions such as load that can affect lean burn engine CO emissions. 
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For lean burn gas-fired engines, the proposed rule establishes CO as a surrogate for HAP 

emissions such as formaldehyde. In discussions with INGAA, EPA has indicated that it 

is acceptable to complete the MACT floor analysis based on CO emissions data, and 

companion HAP data (e.g., formaldehyde) are not necessary. Since CO measurement is 

common in compliance tests, available test results offer considerable data and the 

INGAA data collection focused on CO emissions data. Since formaldehyde emissions 

testing typically has not been required and formaldehyde is more difficult to measure 

than CO, it was expected that very little formaldehyde data would be available from 

previously conducted tests. This was verified in the data collection effort. 

INGAA understands that EPA will complete a MACT floor analysis based on available 

data, including the data in this report. INGAA is compelled to provide its perspective of 

the MACT floor analysis and consideration of variability based on Clean Air Act 

requirements and recent Court decisions. Because there are many existing reciprocating 

internal combustion engines and it is not feasible to have a detailed understanding of 

emissions from all engines, any available dataset will have inherent limitations or 

deficiencies and those limitations need to be considered in the analysis. For example, 

although this report provides considerable data from many engines, there are limitations 

that could result in an unreasonable outcome depending upon the technical analysis of the 

data. INGAA compiled data from previous tests and some limitations include: 

• The CO data are primarily from previous compliance emission tests. The CO 

emissions data were not collected as part of a comprehensive testing project with 

specific objectives to understand either “best performing” CO levels or emission 

variability. Thus, the dataset characteristics strongly reflect compliance test criteria; 

• Almost all the test data are from compliance tests such as annual performance tests or 

quarterly portable analyzer tests. These tests are typically driven by NOx concerns 

that require high load tests. The proposed rule requires compliance at all operating 

conditions including low load, and it is commonly understood that lean burn engine 

CO emissions increase at lower load. CO test data at low load are sparse; thus, the 

collective data set significantly under-represents low load operating conditions and 

bias the data, on average, towards high load conditions with lower characteristic CO 

emissions and higher NOx emissions. 

• The number of tests for any particular engine varies from one test , which often 

includes three test runs at one operating condition, to numerous tests conducted over a 

period of years and/or at various operating conditions. As discussed below, this 

influences the preferred approach for identifying best performing engines when 

comparing emissions in the dataset – i.e., which emissions data are used to determine 

the best performing engines when considering engines with multiple tests. 

2.1 Identifying Best Performing Units 

The March 2009 proposed rule established the “MACT floor” technology as an 

uncontrolled engine – i.e., no add on HAP controls are applied. INGAA supports that 

conclusion, and the analysis for RICE subcategories is not complicated by multiple HAP 

or CO control technologies within the INGAA data population. The INGAA CO 
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emissions data are from engines that do not include CO controls – i.e., do not include an 

oxidation catalyst. 

INGAA understands that EPA plans to focus on the best performing units (i.e., data from 

the best performing 12%) when assessing variability. However, different approaches can 

be considered, and have been used by EPA in NESHAP rules, to identify the best 

performing units in the dataset. Since the engines in this report include some engines 

with single or very few tests and other engines with multiple tests at various times and/or 

operating conditions, the basis of this comparison is important. 

In addition, some tests include multiple test runs at a single operating condition – i.e., 

three tests runs that are averaged for a compliance test. Other tests in the data set are 

single runs. The analysis approach needs to identify how data will be treated for tests 

with multiple test runs completed at a single operating condition. 

Based on docket documents, INGAA understands that for the March 2010 compression 

ignition NESHAP amendments, when multiple test runs are available for a single test 

condition, such as three “high load” test runs for a compliance test, EPA used the average

of the multiple runs (i.e. the test average) when comparing emissions data between 

engines to identify the best performing 12%. If only a single run is available at a 

particular test condition (e.g., prevalent for test data from EPA-sponsored and other tests 

at the Colorado State University engine test bed), that single test result is used for the 

inter-engine comparison to identify the best performing 12%. INGAA uses this same 

approach in the Section 3 and Section 4 discussion.

The next step is to consider how to evaluate engines and compare data between engines 

when some engines have multiple tests. This comparison “ranks” the engines and 

identifies the best performing 12% of the engine population. In the INGAA data set, 

engines with multiple tests include engines tested at different times (e.g., annual or 

quarterly compliance tests over a period of time), and, to a lesser extent, engines tested at 

multiple operating conditions (e.g., multiple loads). As described below, INGAA 

recommends that for engines with multiple CO emission tests, the lowest or best 

performing CO emissions from each engine should be used for engine-to-engine 

comparisons to identify the best performing 12%. This approach bases the comparison 

on the best performance for each individual engine, and provides the best assurance that 

tests completed at similar operating conditions (e.g., tests at high load) are compared 

when defining the engines that comprise the top 12%. 

To further explain, consider an alternative approach where the highest CO emissions are 

used for engine-to-engine comparisons when an engine has multiple tests. Since the CO 

data compiled from INGAA members are typically from compliance tests, high load is 

the norm. Thus, for engines in the data set with a single test, a high load test with lower 

characteristic CO emissions is most likely. Alternatively, an engine with multiple tests 

may have data over a broader array of conditions, including changes to load or other 

parameters that can impact CO such as the air to fuel ratio (i.e., AFR which reflects the 

amount of excess combustion air) or ambient conditions (e.g., summer versus winter 
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tests). The prevalence of compliance test data also ensures that multi-test engines very 

likely include data at full load with lower characteristic CO emissions. 

If the top 12% is selected based on comparing the highest CO from multi-test engines, it 

is likely that an operating condition with higher characteristic CO emissions (e.g., lower 

load and/or higher AFR) from the multi-test engine would be compared to a full load test 

with lower characteristic CO emissions for the single-test engine. This is an inequitable 

comparison which will result in multi-test engines being precluded from or limited in the 

engine population that comprises the best performing 12%. In addition, this approach 

prevents the comparison of CO emissions at common operating conditions (e.g., high 

load and nominal AFR) for the multi-test versus single test engines, and also prevents 

consideration of operating conditions that reflect “best performance” for multi-test 

engines. 

Based on this understanding of the emissions dataset and associated test conditions, 

INGAA believes that the most logical and technically preferred approach is to compare 

engine-to-engine data under similar operating conditions where feasible. Such a 

comparison has a higher probability of identifying the better performing engines. For 

example, comparing CO emissions from two engines at high load provides an indication 

of the better performer. However, comparing high load emissions (with lower 

characteristic CO) from one engine with low load emissions (with higher characteristic 

CO) from another engine does not provide a reasonable basis for assessing which engine 

is the better performer because there is a discrepancy in load, a key operating parameter 

that is known to impact lean burn engine CO emissions. 

Engine emission characteristics also support the common operating condition comparison 

that is best achieved by comparing lowest emissions from multi-test engines. For 

example, for lean burn reciprocating engines, it is generally expected that CO emissions 

are more variable across the range of typical engine conditions (e.g., load and AFR) on an 

individual engine than the variability that would be reflected by comparing multiple 

similar engines at a common high load operating condition. If all engines in the dataset 

were tested under a similar range of operating conditions and had a similar number of test 

points, this issue would be less compelling. However, for the data provided in this report, 

where the number of tests per engine varies from a single test on many engines to more 

than ten tests on other engines, this analytical approach is important not only for defining 

best performers, but also for providing the ability to consider data from multiple tests to 

better understand emissions variability. 

While the alternative approach (i.e., identifying MACT floor engines based on highest 

CO emissions) is not detailed in this report, INGAA review of the dataset confirms the 

concerns expressed here: sorting the data based on the best performing or lowest CO 

emissions for multi-test engines results in many engines with multiple tests in the MACT 

floor (as shown in Sections 3 and 4); in contrast, an alternative that sorts the engines 

based on maximum emissions results in nearly all of the MACT floor engines being 

single test engines (i.e., CO based on one test run or one, three run test at a single 

operating condition). The latter outcome hinders the ability to assess emissions 
Technical Report: Natural Gas-Fired Engine Emissions Data for MACT Floor 

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variability for the best performing 12% of engines. It also fails to identify the engines 

with the best CO emissions performance. 

Thus, INGAA strongly recommends that the “best performing” engines within a 

subcategory be based on selecting the lowest CO test from multi-test engines for 

comparison with other engines. INGAA believes that this approach is consistent with the 

Clean Air Act and has the most technical merit for equitably comparing engine emissions 

performance and identifying best performing engines. In addition, since this approach 

will limit the likelihood that multi-test engines will be inappropriately excluded from the 

“MACT floor” engine population, this approach also facilitates consideration of the range 

of emissions for best performing engines and CO emissions variability. INGAA analysis 

and discussion in Sections 3 and 4 use this approach for identifying the engines in the 

“MACT floor”. 

2.2 MACT Floor Variability 

As noted above, EPA has indicated that review of emissions variability should be limited 

to the “MACT floor” units – i.e., the engine population in the best performing 12%. This 

report does not discuss possible alternatives to this interpretation for the variability 

assessment; however, the EPA approach does introduce limitations when considering the 

vast array of engine types and applications. 

For example, it is commonly understood that ambient conditions (e.g., temperature, 

humidity or precipitation) and elevation can impact emissions. Both higher elevation and 

cooler ambient temperature can increase CO emissions. If data from the MACT floor 

engine population are limited to engines at lower elevation or from warmer weather tests, 

than variability associated with these factors will not be captured. In addition, some 

engines with multiple tests over a broad range of operating conditions may provide 

informative emissions variability data; however, if the lowest CO emissions are not 

within the best performing 12%, then that data set is not included in the analysis. 

These factors, along with the fact that the CO data in this report are not based on a test 

program designed to characterize and understand variability but rather are primarily from 

high load compliance tests, indicate that the emissions variability in the data set is likely 

to be conservative and under-estimate the CO emissions variability that will occur on best 

performing engines in practice. The INGAA data represent a relatively large data set, 

and it is understood that there are practical limitations to the amount of data and 

emissions characterization studies that can be completed for an equipment category as 

diverse as reciprocating internal combustion engines. Nonetheless, it is important to 

consider these limiting factors when assessing variability. 

This report is an “emissions data report” with complementary technical discussion, and 

detailed citations and legal justification for considering variability are not provided. 

However, a review of recent Court decisions provides insight into assessing variability 

when establishing the MACT floor for existing engines. The 2007 Brick MACT 

encapsulates many of these decisions by referring to the recent record from other 

NESHAP challenges. Examples include: 
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• The Brick MACT decision reiterates a finding from the 2001 Cement Kiln MACT 

decision and a related 1999 decision where the D.C. Circuit Court explained, “EPA 

would be justified in setting the floors at a level that is a reasonable estimate of the 

performance of the ‘best controlled similar unit’ under the worst reasonably 

foreseeable circumstances.” 

• “Cement Kiln” also acknowledges that it is acceptable for EPA to consider the range 

of emissions from the best performing sources and that results at more adverse 

conditions “are more helpful than normal operating data would be in estimating 

performance under a variety of conditions and thus in helping to assure that properly 

designed and operated sources can achieve the standard.” 

• The Brick MACT decision also references the 2003 Mossville Environmental Action 

versus EPA decision in which the D.C. Circuit Court “...held that floors may 

legitimately account for variability because “each [source] must meet the [specified] 

standard every day and under all operating conditions.” 

• A similar theme is evident in a 1999 Sierra Club versus EPA decision noting that the 

MACT floor standard must be achieved at all times and relevant factors should be 

considered, “under the most adverse circumstances which can reasonably be expected 

to recur.” 

Thus, it is acceptable and expected for EPA to consider emission levels associated with 

normally anticipated and recurring operating conditions, and Court decisions 

acknowledge that data from more adverse operating conditions may better inform the 

basis of the standard. For the context of the lean burn engine emission standard 

considered in this report, higher CO emissions associated with reasonable operating 

conditions likely to recur are of special interest. These operating conditions and 

associated emissions are of interest due to the nature of the dataset, where high load 

compliance tests are prevalent due to the basis for historical engine tests. Thus, the data 

distribution is not indicative of actual day-to-day operations and more adverse conditions 

(for CO emissions) such as low load are significantly under-represented. 

In addition, Court cases buttress EPA’s position that the floor should not be based on 

“worst performer” units with the MACT floor technology (i.e., lean burn engines without 

HAP/CO control for this standard) that are not within the best performing 12%. For 

example, the Brick MACT decision references a Cement Kiln MACT finding, “...that 

EPA may not use emission levels of the worst performers to estimate variability of the 

best performers without a demonstrated relationship between the two...”. Demonstrating 

a relationship could provide an avenue to consider variability from units outside the top 

12% (e.g., a unit not within the floor that is the same make and model as a MACT floor 

unit but located at a different elevation). However, this is not pursued in the analysis in 

this report. 

In summary, in considering variability, INGAA recommends that EPA: 

• Identify “best performing” engines based on the lowest CO emissions for engines 

with multiple tests; 
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• Incorporate the range of emissions from best performing engines into the standard 

setting process; 

• Consider whether the operating conditions associated with higher CO test results 

points are within the envelope of reasonable operations and likely to recur; 

• Consider that the CO emission data distribution for this dataset is not indicative of 

actual day-to-day operations and more adverse conditions for CO emissions such as 

low load are under-represented; 

• Consider that the units must meet the standard every day and under all operating 

conditions; and 

• Establish a standard that MACT floor units can meet if operating “under the most 

adverse circumstances which can reasonably be expected to recur.” 

In Sections 3 and 4, data are summarized for the engines that comprise the best 

performing 12%. The analysis and discussion of the CO emissions data collected by 

INGAA are based on the principles discussed above. 

3.0 Data Summary and Discussion: Four-Stroke Cycle Lean Burn Engines 

This section discusses the CO emissions data for 4-stroke lean burn engines, and focuses 

on emissions for the best performing 12% of engines. CO emissions data are available 

from eighty-five 4SLB engines with over 1,000 test runs. Engine size ranged from 

approximately 600 hp to 7,800 hp and includes large bore, slow speed “integral” engines 

and higher speed separable engines. Integral engines are common in gas transmission 

and include the engine and compressor (i.e., driven equipment) in one package with both 

driven off a common crankshaft. For separable engines (e.g., Caterpillar and Waukesha 

engines), the driven equipment (e.g., compressor, pump, electric generator) is a separate 

package linked to the engine drive shaft. 

Because these data are from gas transmission, the most prevalent engine manufacturer in 

the data set is Ingersoll Rand, which is the primary 4SLB integral engine manufacturer. 

Other engine manufacturers represented within the data set include Cooper Bessemer, 

Caterpillar, Waukesha, Superior, and Wartsila. Since INGAA members participated in 

the EPA testing for the RICE MACT at the Colorado State University EECL, the CSU 

Waukesha 3521GL engine is included in this report. Emissions data are in Appendix A, 

but this 4SLB engine is not in the best performing 12%. 

The emissions review and analysis, and data presentation are consistent with the 

discussion in Section 2. When a single test included multiple test runs (e.g., 3-run 

compliance test), the average of the three runs was used for comparison with other 

engines. This is consistent with the EPA diesel engines data presentation for the March 

2010 RICE NESHAP amendments. When an engine has data for more than one test, the 

lowest (i.e., best performing) emissions level from the multiple tests was used for 

comparison with other engines. Based on this comparison, the engine population that 

comprises the best performing 12% was identified. Eighty six engines were evaluated 
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and eleven engines comprise the best performing 12%. This evaluation is termed the 

“MACT floor” and these engines are referred to as “MACT floor units” or “MACT floor 

engines” in this report. 

All of the 4SLB data are presented in Appendix A, with the individual tests associated 

with the eleven MACT floor engines presented in Appendix A-1 and the remaining 

engines in Appendix A-2. Each test run is shown in a single row in the data tables, and 

the average of multiple runs at a common operating condition is shown where applicable. 

INGAA members provided summary data and test reports for MACT floor engines will 

be provided to EPA separately. 

For both 4SLB engines and 2SLB engines in Section 4, standard test methods were used. 

Tests were typically to demonstrate compliance with emission limits (e.g., annual tests, 

quarterly tests) or in some cases to collect data for initial Title V permits or define an 

engine specific emission rate. Standard methods were used including EPA reference 

methods (e.g., Method 10 for CO), the ASTM portable analyzer test method, or other 

standard portable methods (e.g., state sanctioned methods). Additional detail on test 

methods and data quality assurance for MACT floor engines is available in test reports 

that will be provided separately. 

Table 1 presents summary information for the best performing 12% of the engines (i.e. 

the MACT Floor units), including the minimum emissions, maximum emissions, number 

of tests, and horsepower range for the tests. The engines are ranked based on the 

minimum emission level. In addition to the MACT floor units, the next two best 

performing engines are shown to indicate the next units that would be included in the 

MACT floor if the number of MACT floor units changes (e.g., other data are available 

that increases the number of MACT floor units). In addition, Table 1 indicates whether 

the engines are equipped with low emission combustion (LEC) technology for lower 

NOx emissions. LEC is a technology difference that could warrant a separate 

subcategory, but since both engine types are represented in the floor, this does not appear 

necessary. 
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Table 1. Summary of INGAA CO Emissions Data for 4SLB MACT Floor UnitsA

Performance CO (ppm, 15% O2)

Rank ID No. Make Model Min Max # TestsE Min. Load Tested (%) hp 

T

1 1 Ingersoll Rand 512 KVS 114 214 16 78 1,92 2 Cooper Bessemer LSV-16 123 140 3 78 3,343 3 Ingersoll Rand 36 KVS 124 270 16 76 794 4 Ingersoll Rand KVH-616 128 240 13 57 2,395 5 Ingersoll Rand 512 KVS 131 226 16 80 1,626 6 Cooper Bessemer LSV-16 135 144 3 82 3,557 7 Ingersoll Rand 36 KVS-FT 137 375 11 47 478 8 Ingersoll Rand 36 KVS 139 298 16 71 709 9 Caterpillar G3516 141 196 5 76 65

10 10 Ingersoll Rand KVT 512 149 226 6 67 2,02

11A 11 Ingersoll Rand KVSR 412 153 223 2 88 1,79

12 12 Waukesha 3521GL 154 338 3 75 5813 13 Superior 12SGTB 159 254 38 79F 1,61

A The first eleven engines comprise the MACT floor from the INGAA data. The next two best performing enginB Maximum horsepower tested is at or near maximum rated load. C Low (NOx) Emission Combustion configuration (e.g., enhanced ignition and/or mixing, pre-combustion chambD Engine ID No. 7 included “operating map” testing in March 2006. Multiple operating conditions were run to m

47% to 99% load. This is the broadest load range tested for any of the 4SLB engines in the MACT floor and th

emissions are associated with the low load test condition. 

E Number of “tests” at unique conditions; not number of test runs. A multi-test run average (e.g., 3-run complianF Load not available for all tests associated with quarterly portable analyzer tests.
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3.1 Comparison with EPA 4SLB Data 

INGAA discussed the EPA database emission data for 4SLB engines in its June 2009 comments. 

Those data are not presented in this report, but INGAA briefly reviewed the EPA data for 

comparison to the engines and CO emissions in Table 1. There are about 12 uncontrolled 4SLB 

engines in the EPA database with CO emission levels ranging from less than 100 ppmv to 420 

ppmv. Two or three engines have “best performing” CO emissions commensurate with the 

MACT floor engines in Table 1. Nearly all of the tests are at relatively high load (80% or 

higher) and there are no engines with multiple tests that include low load (i.e. < 60 - 70%) data in 

the EPA data set. The EPA CSU engine was tested at loads as low as 59% of full load with CO 

emissions as high as 420 ppmv, but its lowest emission test was over 200 ppmv and thus it is not 

in the best performing 12% of the engine population. 

If the EPA database engines are combined with the INGAA 4SLB data, the new total engine 

count would result in twelve or thirteen total engines in the MACT floor; these would include 

two or three engines from the EPA database (i.e., engine-specific identification is not clear in the 

EPA database and a “MACT floor” engine from the EPA database may be two similar engines or 

a single engine with multiple tests). These engines were tested at one point in time at high load 

and do not provide insight into variability. Thus, integrating the EPA and INGAA engines into a 

single data set should not significantly impact the determination of the MACT floor units shown 

in Table 1. In addition, that data integration should not significantly impact the variability 

analysis. 

As discussed in Section 2, INGAA believes that the variability analysis needs to consider the 

range of emissions, and the related operating conditions for the emissions. The data in Table 1 

and Appendix A document that nearly all the emission tests were conducted at higher load, 

typically 80% load or higher, and there are very few low load tests. The lack of low load data is 

not indicative of the typical operating profile for lean burn engines in common applications, but 

rather due to the preponderance of compliance tests emissions data, where high load is typically 

required for demonstrating compliance with NOx limits. Variability review should thus value 

tests on lean burn MACT floor engines that are completed over a range of operating conditions, 

such as load, because these tests provide more insight into emissions variability and operation 

under adverse conditions. This is consistent with the Court’s conclusion, noted in Section 2, that 

data under more adverse conditions are more helpful in establishing the standard. 

Based on the March 2010 RICE NESHAP, the emission standard will apply under all operating 

conditions other than startup. Thus, the operating conditions associated with CO emissions data 

for the MACT floor engines must be considered when assessing variability. This approach is 

warranted to achieve the directive of recent Court decisions that units must comply every day 

and under all operating conditions, and that it is reasonable to establish a standard that MACT 

floor units can meet if operating “under the most adverse circumstances which can reasonably be 

expected to recur.” Lower load is a common and recurring condition for engines. 

3.2 Variability and Factors that Influence 4SLB CO Emissions

For many gas transmission applications, it is commonly understood that a reciprocating engine is 

the preferred compressor driver (i.e., rather than a combustion turbine) because a reciprocating 
Technical Report: Natural Gas-Fired Engine Emissions Data for MACT Floor 

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13 

engine performs better at reduced load and increases operational flexibility. While higher load 

operation is generally preferable and inherent to pipeline system operating principles, gas 

transmission operations respond to pipeline demands, which require operational flexibility and 

lower load operation. Thus, reciprocating engines will continue to be an integral component of 

natural gas pipeline operational flexibility, and lower load operation is and will continue to be an 

inherent part of reciprocating engine operations in natural gas transmission. However, as 

discussed in Section 2, available emissions data are predominantly from high load compliance 

tests. The 4SLB data in the EPA database are also primarily high load data. With lower load 

significantly under-represented in the available data, special consideration of low load data is 

warranted when assessing emissions variability. 

Thus, even though the INGAA data set includes many engines and test points, the population of 

test data is predominately from high load compliance tests, and the data do not adequately or 

uniformly encompass or capture emissions under more adverse conditions, such as operation at 

lower load operation or leaner air-to-fuel ratio where CO emissions will be higher. Since the 

MACT floor emission limit must be achievable at all times, proper consideration of emissions 

variability and the range of potential engine operating conditions is imperative to the analysis. 

”At all times” achievability should not be overlooked or dismissed when establishing the MACT 

floor, because failure to assess lower load operation and reasonable operating envelopes could 

result in technically questionable conclusions. This issue is discussed further below. Section 4.2 

on 2SLB engines provides a hypothetical example of how data from more adverse operating 

conditions better inform the variability assessment. The example in Section 4.2 illustrates why it 

is reasonable to consider the relevance of data that better capture emissions over a range of 

operating conditions when assessing variability and that same rationale applies for 4SLB engines 

in this data set. 

From Table 1, only one of the 4SLB MACT floor engines has data over an operating envelope 

that includes less than 50% load – the Ingersoll Rand 36 KVS-FT engine, the seventh engine 

listed in Table 1 with Unit Identification Number 7. The tested load range is well within normal 

operating scenarios and lower load operation (i.e., lower than 47% load) will recur in practice for 

gas transmission engines. This engine is rated at 1,000 hp and was purposefully tested over a 

range of common operating conditions in March 2006. This existing dataset is especially 

valuable because it provides better insight into adverse operating conditions and emissions 

variability across common operating conditions than other 4SLB engines in the INGAA data set. 

The test data for this engine are presented in Appendix A-1 and summarized in Table 2. The 

engine was tested over a range of common loads and speeds; but even for this more robust data 

set the minimum load was 47%, and lower operating loads occur in normal operation. 

 
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Table 2. CO Emissions Summary for Ingersoll Rand 36 KVS-FT. 

Test No. Load (hp) Speed 

(rpm) % load %O2

CO (ppm, at 

15% O2) 

1 573 270 57 12.4 230 

2 472 270 47 13.4 375 

3 990 330 99 11.8 137 

4 926 300 93 12.2 202 

5 853 270 85 12.1 182 

6 725 270 73 11.9 207 

7 795 300 80 11.0 200 

8 872 330 87 11.0 175 

9 752 330 75 11.2 213 

10 675 300 68 10.9 178 

11 571 270 57 11.2 182 

The Ingersoll Rand 36 KVS-FT engine data demonstrate expected CO emission trends, with CO 

lowest at high load and increasing with lower loads. Although these data represent a more 

complete range of operating conditions and loads than other 4SLB MACT floor engines, the data 

do not capture the full range of expected operating conditions. For example, engine operation at 

lower than 47% of rated load will occur for gas transmission engines during normal operations. 

These March tests occurred at relatively cool ambient temperatures of 29 to 37oF, but this range 

does not represent minimum temperatures for this site, and lower temperature can increase CO 

emissions. 

Thus, while the test at 47% load represents the most adverse condition for this particular test 

program, it is not indicative of the most adverse condition likely to recur – i.e., lower load and/or 

cooler temperature are two parameters that will adversely effect CO emissions and would likely 

result in higher CO emissions over the course of annual operation. Those effects are not 

captured in this data set or other data that are available for this review, but support the assertion 

that 375 ppmv CO (at 15% O2) for the low load (47%) test does not fully address the variability 

that is inherent to this MACT floor engine. 

The data set for this MACT floor analysis is imperfect, and it is clear that the range of emissions 

(i.e., variability) for the MACT floor engines is limited by the fact that most tests were 

conducted at high load for compliance purposes, while the standard will require compliance 

under all operating conditions. Similarly, even the most robust test data within the MACT floor 

engines are limited by the testing completed. The 2006 test was not designed or conducted to 

evaluate emissions over the full range of operating conditions, but fortuitously included tests at 

lower load than other MACT floor units, as well as high load tests. Thus, when considering 

operating conditions and emissions variability that are likely to recur for MACT floor engines, it 

is reasonable to conclude that a 4SLB CO standard of at least 375 ppmv is warranted. 
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While INGAA understands that the regulatory criteria and standards differ, this emission level 

can be compared with other emission results and technology driven standards to provide context. 

For example, the spark ignition RICE New Source Performance Standard (NSPS) is based on 

“best demonstrated technology” for new engines and the NSPS does not require catalytic control 

– i.e., the technology basis is similar to the RICE NESHAP MACT floor. The NSPS CO 

standard is 540 ppmv (at 15% O2) for new, modified and reconstructed engines, and decreases to 

270 ppmv for new, non-emergency units manufactured after 2010 or 2011 (date depends on 

NSPS subcategory). Thus, the most adverse emission level shown in Table 2 is within the range 

of anticipated CO emissions for a new engine with best demonstrated technology. For another 

comparison, the EPA-sponsored 4SLB RICE MACT tests at CSU include testing over a 

reasonable operating envelope, but the minimum load was only about 59% of rated capacity. CO 

emissions for those tests ranged from 305 to 420 ppmv, with the highest emissions actually from 

a higher load test with marginally leaner operation (i.e., slightly higher excess O2). 

4.0 Data Summary and Discussion: Two-Stroke Cycle Lean Burn Engines 

This section discusses the CO emissions data for 2-stroke lean burn engines, and focuses on 

emissions for the best performing 12% of engines. The majority of compressor drivers in the 

U.S. natural gas transmission sector are 2SLB integral engines. Because of this prevalence, there 

are many tests available; however, as discussed in Section 3 for 4SLB engines, the vast majority 

are high load compliance tests in response to NOx requirements. Data are available from 325 

engines with over 3,000 test runs. Despite this wealth of data, there are still limitations due to 

the lack of low load tests. In addition, the 2SLB engine category could be more complicated due 

to technical differences inherent to engine design that could warrant the need for additional 

subcategories. Example technical differences include cylinder displacement (i.e., size), air 

supply (e.g., turbo-charged, piston scavenged), and air flow (e.g., “uniflow” versus loop 

scavenged designs). 

These and other factors present technical differences that affect the engine “type” and 

characteristic emissions – and thus may warrant consideration for additional 2SLB subcategories. 

However, INGAA believes that with proper consideration of variability, the emission differences 

for different 2SLB engine types are minimized. Thus, despite these design differences, it may be 

feasible to avoid additional subcategorization if a MACT floor engine has test data over a broad 

enough range of operating conditions to encompass emissions variability indicative of 

performance for the MACT floor engines for different possible subcategories – i.e., variability 

exhibited across the operating envelope may reasonably capture the emission differences due to 

design and operational differences between 2SLB engine types. Or, expressed another way, 

while the lowest or best performing emissions for different possible subcategories may be 

significant and reflective of different engine types, emissions variability across the operating 

range for different engine types may suppress some of the differences seen at the “best 

performing” point (i.e., lowest emissions exhibited at high load and nominal speed and AFR). 

These issues are discussed further below, after the summary data for “MACT floor” engines are 

presented. 
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Two-stroke lean burn engines are typically large bore, slow speed integral units and the size of 

tested engines ranged from under 300 hp (Ajax engines) to more than 10,000 hp with most 

engines from 1,000 to 4,000 hp. The most prevalent 2SLB engine types (based on manufacturer) 

are Cooper Bessemer, Clark, Worthington, and Cooper Cameron (Ajax). Within the engine lines 

produced by these manufacturers, operated by INGAA members, and represented in the INGAA 

dataset, there are more 2SLB engine models in this report with unique design and technical 

attributes than 4SLB engine models with design and technical attributes that significantly impact 

CO emissions. These array of differences are due in part to different ways of “handling the air” 

to promote cylinder scavenging (i.e., sweep out the exhaust products for the two-stroke cycle). 

In addition to the INGAA data, 2SLB Ajax engine test data is presented in this report from the 

Exterran, JW Power and CSI (EJC) Group that also recently submitted a test report to EPA for 

rich burn engines. The Ajax engine CO emissions tests completed during the EJC test program 

were limited in scope. The CO data were reviewed along with the INGAA data and CSU engine 

data (discussed below). None of the Ajax engines, including an Ajax engine operated by an 

INGAA member, exhibited CO emissions low enough for inclusion in the MACT floor. Thus, 

the data for these engines are shown in Appendix B-3 with units that comprise 88% of the 2SLB 

engine population that are not MACT floor engines. 

In addition, INGAA members participated in EPA testing for the RICE MACT at CSU, and the 

CSU Cooper Bessemer GMV-4TF engine is included in this report, with a separate section 

discussing the engine and emission results. This engine is extremely important to the 2SLB 

engine dataset because: 

• The Cooper GMV engine is the most prevalent engine model in natural gas transmission. 

There are several different primary designs mainly differentiated by air handling (e.g., piston 

scavenged, blower scavenged, turbo-charged); 

• The CSU engine cylinder bore and stroke, parameters that impact emission performance, are 

characteristic of in-service engines. While the CSU engine has a lower full load rating than 

most field applications of Cooper GMV engines, this difference is due to the number of 

cylinders – i.e., four cylinders for the CSU engine where eight is the most standard GMV 

configuration. Despite this difference in maximum rating, the key “size” characteristics 

(cylinder bore and stroke) and engine systems that impact performance and emissions for the 

CSU GMV-4 are the same as GMV engines with more cylinders and higher rated capacities. 

• The EPA-sponsored tests at CSU captured some operational variability. As discussed below, 

the “best performing” CO results from the CSU test matrix for the EPA-sponsored RICE 

MACT testing are just marginally higher than the threshold that defines the best performing 

12%. Thus, the engine would not be a MACT floor unit based solely on the EPA tests. 

However, this engine has been used for numerous other studies and supplemental data are 

available from “standard” engine configurations (i.e., not “experimental” configurations 

associated with technology review or development projects at the CSU test bed) with a wider 

range of emissions. Additional supplemental data are further discussed below and presented 

in Appendix B-2. CO emissions from these supplemental tests include test points with 

marginally lower (and marginally higher) emissions than from the EPA tests. This results in 

the CSU engine being in the best performing 12%, and thus establishes the engine as a 

MACT floor unit. 
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• For 2SLB engines, the full range of emissions data from the CSU engine provides the best 

data set to assess variability for 2SLB engines. Although, like other engines, low load test 

data are limited. The lack of low load emissions data is due to the historical focus on NOx 

emissions; because NOx emissions decrease at lower load for 2SLB engines, minimal low 

load data have been collected. However, some emission data are available for engine 

operation at lower loads and marginally higher air-to-fuel ratios, and these data provide an 

indication of CO variability at operating conditions that recur in practice for 2SLB engines. 

The emissions review and analysis, and data presentation in this section are consistent with the 

discussion in Section 2. When a single test included multiple tests runs (e.g., 3-run compliance 

test), the average of the three runs was used for engine-to-engine comparisons. This is consistent 

with the EPA diesel engines data presentation for the March 2010 RICE NESHAP amendments. 

When an engine has data for more than one test, the lowest (i.e., best performing) emissions level 

from the multiple tests was used for comparison with other engines. Based on this comparison, 

the engine population that comprises the best performing 12% was identified. 325 engines were 

evaluated, so thirty-nine engines comprise the best performing 12% if all 2SLB units are grouped 

in a single subcategory. (A section below discusses the possible need for additional 

subcategories but INGAA believes that additional subcategories may not be necessary if 

emissions variability is assessed as discussed in Sections 4.2 and 4.3.) 

All of the 2SLB emission test data are presented in Appendix B, with the MACT floor engines in 

Appendix B-1, CSU engine data tabulated in Appendix B-2, and the balance of the 2SLB engine 

population in Appendix B-3. Each test run is shown in a single row in the data tables, and the 

average of multiple runs at a common operating condition is shown where appropriate. 

Table 3 presents summary information for the best performing 12% of the 2SLB engines (i.e. the 

MACT floor units) from the INGAA data set, including the minimum CO emissions, maximum 

CO emissions, number of tests, and horsepower range for the tests. The CSU engine is included 

in the MACT floor. The engines are ranked based on the minimum emission level. In addition 

to the MACT floor units, the next three best performing engines are shown to indicate the next 

units that would be included in the MACT floor if the number of MACT floor units changes 

(e.g., other data are available that increases the number of MACT floor units). In addition, Table 

3 indicates whether the engines are LEC-equipped for lower NOx emissions. LEC includes 

technology differences that could warrant separate subcategories. 
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Table 3. Summary of INGAA CO Emissions Data for 2SLB MACT Floor Units (39 units comprise 

CO (ppm, 15% O2) Performance 

Rank ID No. Make Model Min Max # TestsE Approximate Min. Load Tested (%) 

1 2S-90 Cooper Bessemer GMVA-10 33 104 11 84% 12 2S-137 Cooper Bessemer GMW-6TF 40 198 13 53% 3 2S-57 Cooper Bessemer GMV-10TF 43 43 1 >90% 4 2S-80 Cooper Bessemer GMVA-10 50 56 2 95% 15 2S-86 Cooper Bessemer GMVA-10 51 108 10 80% 6 2S-79 Cooper Bessemer GMVA-10 52 52 1 >90% 7 2S-145 Cooper Bessemer GMV-8TF 53 142 13 75% 18 2S-96 Cooper Bessemer GMVC-10 53 53 1 >90% 9 2S-132 Cooper Bessemer GMW-10 53 325 5 72% 1

10 2S-55 Cooper Bessemer GMV-10TF 54 54 1 >90% 11 2S-78 Cooper Bessemer GMVA-10 56 56 1 >90% 12 2S-141 Cooper Bessemer GMW-6TF 56 127 10 67% 13 2S-78 Cooper Bessemer GMVA-10 56 56 1 >90% 14 2S-91 Cooper Bessemer GMVA-10 57 114 12 78% 15 CSUA,D Cooper Bessemer GMV-4TF 58 407 98 62% 16 2S-85 Cooper Bessemer GMVA-10 58 91 10 86% 117 2S-87 Cooper Bessemer GMVA-10 58 190 10 86% 118 2S-97 Cooper Bessemer GMVC-10 59 59 1 >90% 19 2S-144 Cooper Bessemer GMW-8TF 59 301 14 64% 120 2S-140 Cooper Bessemer GMW-6TF 59 238 14 77% 21 2S-124 Cooper Bessemer GMVH-8 59 59 1 >90% 22 2S-88 Cooper Bessemer GMVA-10 61 161 10 89% 123 2S-105 Cooper Bessemer GMVH-12 61 64 2 90% 224 2S-89 Cooper Bessemer GMVA-10 62 98 10 75% 25 2S-82 Cooper Bessemer GMVA-10 62 146 9 >90% 26 2S-108 Cooper Bessemer GMVH-12 63 125 15 91% 2
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CO (ppm, 15% O2) Performance 

Rank ID No. Make Model Min Max # TestsE Approximate Min. Load Tested (%) 

27 2S-115 Cooper Bessemer GMVH-12 64 118 27 86% 228 2S-118 Cooper Bessemer GMVH-12 64 117 27 87% 229 2S-134 Cooper Bessemer GMW-6TF 65 135 13 55% 30 2S-119 Cooper Bessemer GMVH-12 65 123 17 65% 131 2S-113 Cooper Bessemer GMVH-12 67 122 27 73% 132 2S-95 Cooper Bessemer GMVB-10 67 97 24 73% 133 2S-146 Cooper Bessemer GMW-8TF 68 150 13 82% 134 2S-110 Cooper Bessemer GMVH-12 68 128 27 80% 235 2S-83 Cooper Bessemer GMVA-10 68 95 10 62% 36 2S-117 Cooper Bessemer GMVH-12 69 122 27 84% 237 2S-112 Cooper Bessemer GMVH-12 69 132 27 91% 238 2S-139 Cooper Bessemer GMW-6TF 69 278 13 60% 

39A 2S-84 Cooper Bessemer GMVA-10 70 123 9 82% 1

40 2S-129 Cooper Bessemer GMW-10 71 327 10 85% 241 2S-107 Cooper Bessemer GMVH-12 71 117 16 89% 2

A The first 39 engines comprise the MACT floor from the INGAA data (plus CSU engine) and EJC Group data. 

in the list are also shown. 

B Maximum horsepower tested is at or near maximum rated load. C Low (NOx) Emission Combustion configuration (e.g., enhanced ignition and/or mixing, pre-combustion chambD The CSU engine is included in the MACT floor. Data are presented in Appendix B-2, and the data are discusseE Number of “tests” at unique conditions; not number of test runs. Counts multi-test run average (e.g., 3-run com
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4.1 Overview of MACT Floor Engines and 2SLB Engine Subcategories

INGAA discussed the EPA database emission data for 2SLB engines in its June 2009 comments. 

Those data are not presented in this report, with the exception of the CSU engine, as discussed 

below. There are about fifteen to twenty 2SLB engines in the EPA database, and several have 

emissions at or below the MACT threshold of 70 ppmv from Table 3. The integration of EPA 

engines with the data in this report would not have a significant impact on the analysis. 

However, in comparing CSU data, an apparent discrepancy was discovered. It appears that the 

EPA database recorded “as measured” CO values as “corrected to 15% O2.” The original CSUEPA report was reviewed to confirm that the CSU CO emissions data presented in this document 

are correct and based on the original data in the report. (The report citation is provided in 

Section 4.3.) 

The CSU engine is a Cooper Bessemer GMV-4TF engine and the MACT floor engines in Table 

3 are all Cooper GMV and GMW engines. Other Cooper engine models, or Clark or 

Worthington engines are not represented in the MACT floor. This is likely due to two primary 

factors: Cooper engines are relatively “well-mixed” in comparison to Clarks and Worthingtons 

(e.g., Worthingtons use “uniflow” rather than “looped” air scavenging which significantly affects 

mixing), and the GMV and GMW series include many engines that are not turbo-charged. In 

addition, the GMV cylinders are smaller (smaller bore and stroke or swept cylinder volume) than 

nearly all other 2SLB engines in the INGAA dataset, with Ajax engines an exception. More 

recent vintage Cooper engines include turbochargers. Thus, a 2SLB floor comprised entirely of 

Cooper GMV and GMW engines could inappropriately represent other types of 2SLB engines, 

and additional subcategories may need to be considered to address different types of engines. 

However, if variability is appropriately considered, the need for additional subcategories may be 

mitigated. 

INGAA understands that emission levels are not the basis for defining a subcategory. This 

decision must be based on unique size, type or class attributes according to the Clean Air Act. 

While detailed documentation is not provided in this report, there are distinct differences 

between different types of 2SLB engines, and those differences are reflected in the CO emissions 

data. Thus, for comparison to the summary emissions data provided in Table 3, Table 4 presents 

the best performing units for 2SLB engine types not represented in the MACT floor (i.e. engines 

other than Cooper GMVs and GMWs). In addition, detailed data in Appendix B show different 

characteristic emissions for different 2SLB engine types. There are inherent physical and 

operational characteristics within the 2SLB subcategory, and INGAA believes that additional 

subcategories based on different types of technology (or different size) could be justified and 

may be warranted. However, this would add complexity to rule development and 

implementation. Review of the emission ranges in Table 3 and Table 4 indicates that 

considering variability within the data set for GMVs – primarily based on more comprehensive 

data from CSU tests – offsets some of the CO emission differences evident at the lowest or best 

performing points. Thus, properly accounting for variability may in part reconcile emission 

differences that could otherwise compel INGAA to strongly support developing additional 2SLB 

subcategories. 
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Table 4. Summary of Best Performing 2SLB Engines Excluding Cooper GMV 

and GMW Engines. 

A

 Clark, Worthington and Cooper Engines (excluding GMV and GMW) total 175 

engines, thus 21 units comprise the best performing 12% for this engine group. 

The lowest emissions (i.e., minimum CO) and cut point for the best performing 12 percent is 

higher for these engines than units in Table 3. In addition, some engines exhibit a significantly 

higher maximum. However, the upper end of the CO emissions range from the CSU data set (in 

Table 3) is similar in magnitude to some engines in Table 4. Appendix B data for all engines, 

including the 88% not in the MACT floor, indicate that many of the makes / models of engines 

in Table 4 have emissions significantly higher than the best performing units shown in Table 4. 
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Thus, the range of emissions (variability) in Tables 3 and 4 is not high enough to ensure that 

many of the engines in the INGAA data set can achieve those levels without additional action; 

that is, variability is not being assessed in this report as a convenient means to facilitate 

compliance, but rather as an imperative part of the standard setting process. 

The range of emissions for the CSU engine provides a reasonable means to assess variability. If 

all 2SLB engines are grouped into one subcategory regardless of technical differences, then over 

thirty engines comprise the MACT floor and, as shown in Table 3, the CSU engine is included in 

the best performing 12 percent. However, if the engines in Table 3 are used to establish a 

standard without consideration of lower load and other common and more adverse operating 

conditions, then INGAA would recommend reviewing the need for additional subcategories. 

INGAA does not provide a detailed technical basis for subcategories in this report. However, if 

needed, that technical information can be provided so that the different 2SLB engine types can 

be better documented and subcategories can be supported. 

4.2 Emissions Variability Assessment

As discussed in Section 3, reciprocating engines are preferentially used in gas transmission 

because of their operational flexibility and ability to perform reasonably well across a range of 

loads based on pipeline demand. INGAA believes that it is appropriate, technically justifiable, 

and consistent with D.C. Circuit Court directives to carefully consider the available emissions 

data that best captures the range of expected operations (i.e., adverse conditions that are 

reasonably likely to recur) when assessing variability. If an emissions dataset for variability 

analysis is homogeneous (i.e., all or most units tested under similar operating conditions that 

encompass the expected/normal range of engine operation), determining and considering which 

of the available emissions data best captures the range of expected operations is less of an 

issue. However, even though the INGAA data set includes many engines and test points, the 

population of test data is predominately from high load compliance tests and does not adequately 

encompass or capture emissions under more adverse conditions, such as lower load operation, 

where CO emissions will be higher. Since the MACT floor emission limit must be achievable at 

all times, proper consideration of emissions variability and the range of potential engine 

operating conditions is imperative to the analysis. ”At all times” achievability should not be 

overlooked or dismissed when establishing the MACT floor, because failure to assess lower load 

operation and reasonable operating envelopes could result in technically questionable 

conclusions. 

To illustrate this point, consider an example case where the initial step of MACT review has 

been completed and there are two “units” in the MACT floor. Both units utilize the same 

technology. As is commonly observed for engines, this example assumes that it is understood 

and technically supported that emissions for these units will vary across the operating envelope. 

One of the two units (unit 1) has a single data point measured at optimal operating conditions 

(e.g., full load, warm ambient conditions, and nominal air to fuel ratio for a lean burn engine). 

Conversely, unit 2 has emissions data from multiple test conditions. One test condition for unit 2 

is identical to the unit 1 data point (high load, and nominal settings) and results in similar 

emissions. The other data points for unit 2 cover the full operating envelope and include a range 

of operating conditions at different points in time; that is, the emission data encompass seasonal 

variation (cold versus warm weather) and include a range of process operations. Although data 
Technical Report: Natural Gas-Fired Engine Emissions Data for MACT Floor 

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from unit 2 show similar emissions under the similar optimal operating condition, significant 

variability is exhibited in its more robust data set. In this instance, it is appropriate and 

technically superior to assess variability based on the data set from the second unit. 

In addition, if the unit 2 data are combined or integrated with the single test from the first unit, 

different weighting should be applied to the datasets. If each unit is assigned similar weighting, 

the technical insight on variability from the more complete data set will be compromised, and 

proper consideration will not have been given to the range of observed operating conditions that 

are likely to recur as reflected in the unit 2 data. 

INGAA believes that it is imperative that technical objectives for assessing variability consider 

the range of reasonable operating conditions. In this example, that would mean that the 

variability assessment would consider the range of emissions associated with the more robust 

data set from the second unit, and limitations associated with the single data point from the first 

unit would be recognized. 

Thus, the breadth of operating conditions and associated CO emissions data from individual 

MACT floor engines should be considered when assessing variability. This approach is 

warranted to achieve the directive of recent Court decisions that units must comply every day 

and under all operating conditions, that data under adverse conditions may be more informative, 

and that it is reasonable to establish a standard that MACT floor units can meet if operating 

“under the most adverse circumstances which can reasonably be expected to recur.” Lower load 

is a common and recurring condition for engines that will impact CO emissions for lean burn 

engines. 

4.3 Discussion of CSU 2SLB Engine Data and NOx – CO Tradeoff

The CSU Engines & Energy Conversion Laboratory Cooper-Bessemer GMV-4TF has four 

cylinders with 14 inch diameter cylinder bore and 14-inch piston stroke. The nominal speed is 

300 rpm and the nominal maximum load is 440 brake-horsepower. This engine is used to 

characterize emissions and evaluate the impacts of ignition and mixing enhancements on engine 

performance. It has been instrumental in supporting the development of technologies that are 

reducing emissions in the existing gas transmission fleet. During the course of these 

evaluations, the CSU engine is often operated and tested at standard, baseline configurations to 

provide a benchmark for the particular project. The standard configurations, typical of the 2SLB 

engine population, include an open combustion chamber (OCC) design and a pre-combustion 

chamber (PCC) design. Emission data from multiple test projects that include standard 

configuration tests provide a dataset to evaluate emission variability for a single engine. In 

addition to OCC and PCC, some open chamber tests used multi-strike spark plugs. The CSU 

data incorporate the impacts of time (e.g., different ambient conditions, time lapse since engine 

maintenance) and normal range operating parameters (e.g. load, air-to-fuel ratio, ignition timing). 

Thus, these emissions data represent operation at conditions that are reasonably expected to 

recur, and are common to the fleet of Cooper GMV and other gas transmission engines. 
Technical Report: Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 

24 

Table 5 presents emission measurement data, sorted from lowest to highest CO emissions, from 

test projects conducted on the CSU engine. These projects include the EPA sponsored testing1

and an emissions tradeoff paper from a 1999 conference2. Additional data are provided from 

industry or manufacturer sponsored testing and those results are documented in Appendix B-2. 

These data are for engine operation in standard, baseline configurations and do not include 

emission data from engine operation associated with evaluating developmental or experimental 

control technologies. CO emissions range from 58 to 407 ppmvd at 15% O2. These data also 

demonstrate the tradeoff between CO and NOx emissions, with NOx ranging from 8 to 1,317 

ppmvd at 15% O2. These emissions are not indicative of long-term performance that is 

continuously achieved, but rather the range of emissions that can occur under operating 

conditions associated with variations in load and excess air. 

Figure 1 plots the CO emission data as a function of NOx emissions. As expected, operations 

associated with higher NOx result in the lowest CO emissions. Thus, a too strident CO standard 

could compel operators to operate at conditions that result in higher NOx. The curve shows the 

familiar CO/NOx trade-off, illustrates the emissions variability, and demonstrates the overlap of 

the CO emissions data from different test projects at similar NOx emission levels. The data 

congruency supports the ability to consider emissions from these different points in time, and 

supplement the EPA program data already in the EPA database with additional test results. 

Additional data details are provided in Appendix B. 

 

1

 CSU-EPA 2000 – “Final Report: Testing a 2-Stroke Lean Burn Gas-Fired Reciprocating Internal Combustion 

Engine to Determine the Effectiveness of an Oxidation Catalyst System for Reduction of Hazardous Air 

Pollutants,” EPA/OAQPS, EPA-454/R-00-036a, July 2000. 

2

 CSU GMC 1999 – “Carbon Pollutant Emissions and Engine Performance Trade-Offs vs NOx Emissions for 

Reciprocating Internal Combustion Engines Utilized in Gas Transmission Service.” Gary Hutcherson, CSU; Chad 

Fletcher, Enginuity International, Inc.; Greg Beshouri, Advanced Engine Technologies Corporation (AETC). 

Presented at 1999 Gas Machinery Conference, Houston, October 6, 1999. 
Technical Report: Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 

25 

 Table 5. CSU CB GMV-4TF Standard Configurations Emissions Data.

Load O2 CO NOx Project Test # 

% % dry ppmvd @ 15% O2 

CSU-GMC 1999 4A-1 112% 13.5% 58 740 

CSU-GMC 1999 2A-6 100% 13.4% 59 1,018 

CSU-GMC 1999 0.10 86% 11.9% 59 1,116 

CSU-GMC 1999 2B-3 101% 13.2% 61 1,315 

CSU-GMC 1999 3A-6 86% 12.2% 61 1,159 

CSU-GMC 1999 0.20 101% 13.6% 61 862 

CSU-GMC 1999 4A-2 112% 13.6% 65 456 

CSU-GMC 1999 2A-7 86% 13.4% 65 786 

CSU-GMC 1999 4B-8 86% 12.0% 65 1,317 

CSU-GMC 1999 2A-5 100% 13.6% 66 648 

CSU-GMC 1999 0.40 112% 13.3% 66 797 

CSU-GMC 1999 3B-1 112% 13.0% 67 1,154 

CSU-GMC 1999 2A-4 101% 13.7% 68 560 

CSU-GMC 1999 2A-8 100% 13.8% 69 585 

CSU-GMC 1999 4A-3 112% 13.9% 71 275 

CSU-GMC 1999 2B-2 100% 13.6% 72 750 

CSU-GMC 1999 0.02 100% 13.9% 73 482 

CSU-EPA PAH-1 85% 14.6% 73 304 

CSU-EPA 6 100% 14.3% 75 202 

CSU-EPA 4 86% 14.7% 75 306 

CSU-GMC 1999 3B-2 112% 13.4% 75 826 

CSU-GMC 1999 0.04 112% 13.4% 76 471 

CSU-EPA 9A 100% 14.5% 78 123 

CSU-GMC 1999 2A-3 100% 13.8% 78 331 

CSU-EPA 10 100% 14.6% 78 145 

CSU-EPA 13 100% 14.6% 81 88 

CSU-GMC 1999 3A-1 86% 14.3% 81 248 

CSU-GMC 1999 0.00 100% 14.0% 83 236 

CSU-EPA 1 100% 14.6% 83 101 

CSU-GMC 1999 0.00 112% 13.6% 84 283 

CSU-GMC 1999 4A-4 112% 14.4% 85 117 

CSU-GMC 1999 2A-2 101% 14.0% 85 184 

CSU-GMC 1999 0.01 86% 14.5% 86 177 

CSU-GMC 1999 3A-2 86% 14.4% 87 151 

CSU-EPA 16 100% 14.6% 88 152 

CSU-GMC 1999 3B-3 112% 13.7% 88 402 

CSU-GMC 1999 2A-12 100% 13.8% 89 129 

CSU-GMC 1999 1B-1 100% 14.0% 89 438 

CSU-GMC 1999 2B-1 100% 14.0% 89 388 

CSU-GMC 1999 4B-7 86% 14.4% 89 243 

CSU-GMC 1999 0.00 100% 14.1% 91 141 

CSU-EPA 15 100% 14.7% 92 133 

CSU-GMC 1999 0.00 101% 13.8% 92 49 

CSU-GMC 1999 4A-5 112% 14.5% 93 110 

CSU-EPA 14 100% 14.6% 95 82 
Technical Report: Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 

26 

Table 5. CSU CB GMV-4TF Standard Configurations Emissions Data. (continued)

Load O2 CO NOx Project Test # % % dry ppmvd @ 15% O2 

CSU-GMC 1999 0.00 86% 14.6% 95 87 

CSU-GMC 1999 2A-1 101% 13.8% 96 134 

CSU-GMC 1999 2A-9 101% 14.3% 98 133 

CSU-GMC 1999 3A-3 86% 14.6% 99 120 

CSU-GMC 1999 0.00 112% 14.2% 102 73 

CSU-GMC 1999 2A-10 100% 14.2% 102 124 

CSU-GMC 1999 0.00 100% 14.1% 102 88 

CSU-GMC 1999 1B-2 101% 14.2% 105 223 

CSU-GMC 1999 3A-4 86% 14.7% 109 99 

CSU-GMC 1999 0.00 100% 14.2% 111 56 

CSU-GMC 1999 4B-6 86% 14.7% 114 105 

CSU-GMC 1999 1B-6 101% 14.3% 115 81 

CSU-EPA 5 100% 15.1% 116 41 

CSU-GMC 1999 0.00 112% 14.5% 116 51 

CSU-GMC 1999 0.00 86% 14.7% 116 61 

CSU-GMC 1999 2A-11 100% 13.8% 116 117 

CSU-EPA 12 86% 15.3% 120 32 

CSU-EPA PAH-3 85% 15.3% 121 30 

CSU-GMC 1999 3A-5 86% 14.8% 122 94 

CSU-EPA 11 86% 15.2% 123 29 

CSU-GMC 1999 3B-4 112% 14.7% 124 68 

CSU-EPA PAH-2 85% 15.4% 127 29 

CSU-GMC 1999 0.00 112% 14.6% 130 51 

CSU-GMC 1999 0.00 86% 14.7% 131 50 

CSU-EPA 8 86% 15.6% 134 33 

CSU-GMC 1999 0.00 100% 14.6% 136 46 

PRCI PCC Eval FE_BL_BM2 100% 14.3% 141 88 

CSU-GMC 1999 1B-5 100% 14.7% 142 32 

CSU-GMC 1999 0.00 101% 14.8% 151 41 

CSU-GMC 1999 4B-5 86% 15.0% 152 46 

CSU-GMC 1999 0.00 86% 14.8% 152 46 

CSU-GMC 1999 3B-5 112% 15.0% 158 29 

CSU-GMC 1999 0.00 86% 15.0% 174 43 

CSU-GMC 1999 1B-3 101% 15.0% 187 21 

CSU-GMC 1999 4B-4 86% 15.1% 188 26 

PRCI PCC Eval FE_BL_FS1 100% 14.5% 192 40 

PRCI PCC Eval FE_BL_FS5 101% 14.5% 195 49 

PRCI PCC Eval FE_BL_FS2 100% 14.6% 200 39 

PRCI PCC Eval FE_BL_FS4 100% 14.5% 201 43 

PRCI PCC Eval FE_BL_FS3 100% 14.5% 202 40 

CSU-GMC 1999 3B-6 112% 15.1% 202 22 

PRCI PCC Eval FE_BL_BM1 100% 14.6% 208 39 

CSU-GMC 1999 4B-1 101% 15.2% 216 26 

CSU-EPA 3 62% 16.1% 246 9 

CSU-GMC 1999 4B-3 86% 15.2% 249 18 
Technical Report: Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 

27 

Table 5. CSU CB GMV-4TF Standard Configurations Emissions Data. (continued)

Load O2 CO NOx Project Test # % % dry ppmvd @ 15% O2 

CSU-EPA 2-7 69% 15.8% 259 8 

PRCI PCC Eval FE_BL_BM6 100% 14.8% 263 19 

PRCI PCC Eval FE_BL_BM3 100% 14.8% 277 21 

PRCI PCC Eval FE_BL_BM4 100% 14.8% 280 21 

PRCI PCC Eval FE_BL_BM5 100% 14.8% 282 21 

CSU-GMC 1999 1B-4 101% 15.5% 343 10 

PRCI PCC Eval FE_BL_BM7 100% 14.9% 369 15 

CSU-GMC 1999 4B-2 86% 15.8% 407 11 

CSU Cooper GMV-4TF CO versus NOx Emissions

0

50

100

150

200

250

300

350

400

450

0 200 400 600 800 1,000 1,200 1,400

NOx (ppmvd at 15% O2)

CO (ppmvd at 15% O2)

1999 CSU-GMC - OCC

1999 CSU-GMC - PCC

1999 CSU-GMC - MSOCC

1999 CSU-EPA - PCC

2009 CSU-PRCI - PCC

Figure 1. CSU engine standard configurations emission data; CO vs. NOx emissions.

For context, the NOx emission levels in Figure 1 can be compared to published emission factors 

for 2SLB engines. For example, in the NOx SIP Call Phase 2 Rule, EPA determined that a NOx 

emission factor of 16.8 g/bhp-hr is representative of uncontrolled gas transmission reciprocating 

engines. This equates to approximately 1,100 to 1,200 ppmv NOx (at 15% O2) for typical 2SLB 

engine efficiency. The EPA AP-42 document presents uncontrolled NOx emission factors for 

load above 90% and a separate factor for load less than 90%. At the higher load, the AP-42 NOx 

emission factor (presented in lb/MMBtu) is approximately 850 ppmv and at lower load the 

emission factor is approximately 500 ppm. The CO emission factors are approximately 170 and 

155 ppmv, respectively. This indicates that higher NOx levels introduced by supplementing data 
Technical Report: Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 

28 

from the EPA sponsored CSU tests with additional CSU test data are well within expected 

ranges. In addition, as one might expect, the CO emissions from the CSU engine, a “best 

performing” MACT floor unit, are lower than the AP-42 emission factors for comparable NOx 

levels. 

In addition, when only considering the CO data from the EPA-sponsored tests, the lowest CO 

point was 73 ppmv (at 15% O2). CO data from other tests as low as 58 ppmv are marginally 

lower, which firmly establishes the CSU engine in the MACT floor. As shown in Table 3, the 

MACT floor cut point is 69 ppmv or only slightly lower than the lowest CO from the EPA tests. 

Considering measurement accuracy, the MACT floor cut point and 73 ppmv measured during the 

EPA tests are essentially the same; this agreement indicates that the CSU engine is effectively a 

“MACT floor” unit based solely on the EPA results. However, the additional test data further 

support the range of emissions and emissions variability for the CSU Cooper GMV-4TF engine. 

As shown in Table 5 and Figure 1, CO emissions are as high as 407 ppmv, with several tests in 

the range of 240 to 407 ppmv. For EPA sponsored tests in this range (Test Points 3 and 2-7), 

these are lower load operation tests with commensurate lower peak combustion temperatures 

resulting in low NOx and higher CO. For other tests with higher CO, the engine was configured 

with the standard pre-combustion chamber technology and air flow was marginally leaner at the 

highest emitting point, but within common PCC operations. The engine configuration and 

operation were consistent with a unit complying with a low NOx emission limit. 

While higher load operation is generally preferable and inherent to pipeline systems operating 

principles, response to pipeline demands requires operational flexibility and lower load 

operation. Thus, reciprocating engines have historically operated and will continue to operate 

across the load range under standard operating scenarios. With lower load and variations in 

other conditions such as excess air (or “turbo boost”) significantly under-represented in the 

available data, special consideration of test results associated with those typical conditions is 

warranted when assessing emissions variability. In addition, the CSU data shows that lower load 

results in higher CO emissions, and the lowest load available from CSU test data is well over 

50% - i.e., higher than loads that recur in normal operation. Based on the available data for 

MACT floor engines, the test data from the CSU engine best captures the range of operating 

conditions that are likely to recur, and those emission bounds should be a primary consideration 

for the variability assessment. Similar to 4SLB engines, the data from 2SLB engines support a 

standard of approximately 400 ppm or higher. 

5.0 Conclusions and Recommendations 

This report provides historical CO emissions data collected by INGAA. In general, test 

requirements for existing reciprocating engines have been driven by NOx concerns; thus, the 

operating conditions for the INGAA CO data are predominantly high load. Since CO tends to 

increase at lower load for existing lean burn engines, this limitation in the dataset (i.e. underrepresentation of low load emission data) is an important consideration when assessing 

variability. 
Technical Report: Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 

29 

MACT floor engines and associated data are discussed in Sections 3 and 4, and the test data are 

tabulated in the Appendices. INGAA review of MACT floor implications are based on the 

principles discussed in Section 2. After the best performing units are identified, limitations in 

the dataset should be recognized when assessing variability. For both the 4SLB and 2SLB 

engine subcategories, low load data are limited. However, for each subcategory, there is a 

MACT floor engine that provides data over a broader range of conditions than the majority of the 

units that have either limited tests or multiple tests at higher load. 

The D.C. Circuit Court has indicated that variability among MACT floor units can be considered 

when establishing the emission standard, because the units must meet NESHAP standards at all 

times and under adverse operating conditions. Thus, it is reasonable to consider emissions 

associated with adverse operating conditions that are likely to recur. That variability is likely 

under-estimated in the INGAA data set because the emissions data are not based on a project or 

testing designed to characterize variability, and common operating conditions associated with 

parameters such as reduced load or marginally higher excess air are not adequately represented 

by the data. Because of the data limitations, the emissions data from some MACT floor engines 

may provide more insight than others when considering variability. 

For both the 4SLB and 2SLB engine subcategories, a specific engine with data available from 

broader test conditions is discussed in the report. Data from both of these engines indicate that 

emissions variability warrants CO standards over 370 ppmv (at 15% O2) for both 4SLB and 

2SLB engines. For context, comparing this level to the “best demonstrated technology” basis for 

lean burn engines under the NSPS, indicates that these existing engines would have a CO 

standard similar to or more stringent than a new, NSPS affected engine. 

In addition, while the body of the report focuses on MACT floor engines, the complete data sets 

in Appendix A and Appendix B indicate that many engines will not readily achieve this standard, 

and action will be required. This could introduce new complexities. Add-on control technology 

(an oxidation catalyst) is challenged by the relatively low exhaust temperature for 2SLB engines, 

and low load and low NOx conditions most conducive to higher CO are also the conditions with 

the lowest exhaust temperatures. These implications should also be considered when 

establishing the standard and ensuring that variability is adequately addressed. 

Finally, if variability is properly accounted for, then subcategories may not be necessary and 

added complexity could be avoided. If INGAA recommendations to properly consider CO 

emissions data associated with tests under more adverse operating conditions are not adopted in 

the EPA analysis, and EPA concludes that lower standards properly assess variability, then 

INGAA recommends that additional subcategories be considered. There are different types of 

engines within both the 4SLB and 2SLB subcategories due to design and technology differences 

such as engine cylinder displacement (which EPA has used in other engine rules), NOx control 

configuration, air handling, and scavenging design for 2SLB engines. This report introduces 

some of these issues but detailed documentation is not provided on additional subcategories. If 

needed, INGAA can provide additional background documentation on the technical basis that 

establishes different engine types for developing more refined subcategories. 
Technical Report: Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 

30 

APPENDICES 

Appendix A: Four-Stroke Lean Burn Engine CO Emissions Test Data 

Appendix A-1: 4SLB Engine CO Emissions Data for MACT Floor Engines 

Appendix A-2: 4SLB Engine CO Emissions Data for Engines not in the MACT Floor 

Appendix B: Two-Stroke Lean Burn Engine CO Emissions Test Data 

Appendix B-1: 2SLB Engine CO Emissions Data for INGAA MACT Floor Engines 

Appendix B-2: 2SLB Engine Emissions Data Summary for CSU GMV-4TF Engine 

Appendix B-3: 2SLB Engine CO Emissions Data for Engines not in the MACT Floor 
Technical Report: Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 

31 

APPENDIX A-1: 4SLB Engine CO Emissions Data for MACT Floor Engines 

Engine 

ID No. Engine Make Model 

Rated 

Load 

(hp) 

Test 

No. 

Run 

No. Test Date 

Test 

Load 

(hp) 

%O2

CO 

(ppmv at 

15% O2)

Avg 

CO1

4S-1 Ingersoll-Rand 512 KVS 2,500 5 1 10/31/1999 2442 10.1 115 

4S-1 Ingersoll-Rand 512 KVS 2,500 5 2 10/31/1999 2420 10.0 114 

4S-1 Ingersoll-Rand 512 KVS 2,500 5 3 10/31/1999 2413 10.0 113 

114 

4S-1 Ingersoll-Rand 512 KVS 2,500 7 1 10/2/2000 2374 10.7 126 

4S-1 Ingersoll-Rand 512 KVS 2,500 7 2 10/2/2000 2375 10.7 126 

4S-1 Ingersoll-Rand 512 KVS 2,500 7 3 10/2/2000 2392 10.7 125 

126 

4S-1 Ingersoll-Rand 512 KVS 2,500 3 1 11/4/1998 2423 11.0 139 

4S-1 Ingersoll-Rand 512 KVS 2,500 3 2 11/4/1998 2457 11.1 125 

4S-1 Ingersoll-Rand 512 KVS 2,500 3 3 11/4/1998 2470 11.2 129 

131 

4S-1 Ingersoll-Rand 512 KVS 2,500 1 1 10/22/1997 2357 11.1 148 

4S-1 Ingersoll-Rand 512 KVS 2,500 1 2 10/22/1997 2397 11.4 134 

4S-1 Ingersoll-Rand 512 KVS 2,500 1 3 10/22/1997 2455 11.4 134 

139 

4S-1 Ingersoll-Rand 512 KVS 2,500 8 1 5/31/2001 2501 10.3 146 

4S-1 Ingersoll-Rand 512 KVS 2,500 8 2 5/31/2001 2490 10.3 146 

146 

4S-1 Ingersoll-Rand 512 KVS 2,500 4 1 4/28/1999 2396 10.9 151 

4S-1 Ingersoll-Rand 512 KVS 2,500 4 2 4/28/1999 2390 10.9 152 

4S-1 Ingersoll-Rand 512 KVS 2,500 4 3 4/28/1999 2384 11.0 155 

153 

4S-1 Ingersoll-Rand 512 KVS 2,500 6 1 4/4/2000 2087 11.2 165 

4S-1 Ingersoll-Rand 512 KVS 2,500 6 2 4/4/2000 2087 11.2 162 

4S-1 Ingersoll-Rand 512 KVS 2,500 6 3 4/4/2000 2088 11.2 162 

163 

4S-1 Ingersoll-Rand 512 KVS 2,500 16 1 9/14/2009 2470 11.6 178 

4S-1 Ingersoll-Rand 512 KVS 2,500 16 2 9/14/2009 2472 11.6 179 

178 

4S-1 Ingersoll-Rand 512 KVS 2,500 14 1 9/3/2008 2441 11.1 185 

4S-1 Ingersoll-Rand 512 KVS 2,500 14 2 9/3/2008 2443 11.1 186 

185 

4S-1 Ingersoll-Rand 512 KVS 2,500 13 1 10/2/2007 2428 11.5 187 

4S-1 Ingersoll-Rand 512 KVS 2,500 13 2 10/2/2007 2433 11.5 186 

186 

4S-1 Ingersoll-Rand 512 KVS 2,500 15 1 5/14/2009 2205 11.6 191 

4S-1 Ingersoll-Rand 512 KVS 2,500 15 2 5/14/2009 2201 11.6 193 

192 

4S-1 Ingersoll-Rand 512 KVS 2,500 9 1 3/30/2005 1959 12.2 201 

4S-1 Ingersoll-Rand 512 KVS 2,500 9 2 3/30/2005 2019 12.2 202 

201 

4S-1 Ingersoll-Rand 512 KVS 2,500 10 1 9/21/2005 2428 11.3 203 

4S-1 Ingersoll-Rand 512 KVS 2,500 10 2 9/21/2005 2477 11.3 205 

204 

4S-1 Ingersoll-Rand 512 KVS 2,500 2 1 4/23/1998 2350 12.4 285 

4S-1 Ingersoll-Rand 512 KVS 2,500 2 2 4/23/1998 2311 11.1 168 

4S-1 Ingersoll-Rand 512 KVS 2,500 2 3 4/23/1998 2275 11.1 171 

208 

4S-1 Ingersoll-Rand 512 KVS 2,500 12 1 4/18/2007 1989 12.1 214 

4S-1 Ingersoll-Rand 512 KVS 2,500 12 2 4/18/2007 2000 12.1 209 

212 

4S-1 Ingersoll-Rand 512 KVS 2,500 11 1 4/12/2006 2497 11.4 216 214 
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32 

4S-1 Ingersoll-Rand 512 KVS 2,500 11 2 4/12/2006 2499 11.5 213 

4S-2 Cooper-Bessemer LSV-16SG 4,400 1 1 2/25/2010 4,205 15.3 113 

4S-2 Cooper-Bessemer LSV-16SG 4,400 1 2 2/25/2010 4,278 15.0 132 

123 

4S-2 Cooper-Bessemer LSV-16SG 4,400 1 3 2/25/2010 3,716 15.5 134 134 

4S-2 Cooper-Bessemer LSV-16SG 4,400 1 4 2/25/2010 3,347 13.2 140 140 

4S-3 Ingersoll-Rand 36 KVS 1,000 2 1 4/23/1998 963 10.9 124 

4S-3 Ingersoll-Rand 36 KVS 1,000 2 2 4/23/1998 964 10.9 126 

4S-3 Ingersoll-Rand 36 KVS 1,000 2 3 4/23/1998 963 10.8 122 

124 

4S-3 Ingersoll-Rand 36 KVS 1,000 6 1 4/4/2000 843 10.9 128 

4S-3 Ingersoll-Rand 36 KVS 1,000 6 2 4/4/2000 846 10.8 126 

4S-3 Ingersoll-Rand 36 KVS 1,000 6 3 4/4/2000 846 10.8 125 

126 

4S-3 Ingersoll-Rand 36 KVS 1,000 5 1 10/31/1999 1044 10.7 127 

4S-3 Ingersoll-Rand 36 KVS 1,000 5 2 10/31/1999 1041 10.7 127 

4S-3 Ingersoll-Rand 36 KVS 1,000 5 3 10/31/1999 1037 10.7 128 

127 

4S-3 Ingersoll-Rand 36 KVS 1,000 7 1 10/2/2000 1003 11.4 141 

4S-3 Ingersoll-Rand 36 KVS 1,000 7 2 10/2/2000 1002 11.4 139 

4S-3 Ingersoll-Rand 36 KVS 1,000 7 3 10/2/2000 1003 11.3 139 

140 

4S-3 Ingersoll-Rand 36 KVS 1,000 16 1 8/25/2009 936 10.8 142 

4S-3 Ingersoll-Rand 36 KVS 1,000 16 2 8/25/2009 933 10.8 146 

144 

4S-3 Ingersoll-Rand 36 KVS 1,000 14 1 9/3/2008 966 11.0 153 

4S-3 Ingersoll-Rand 36 KVS 1,000 14 2 9/3/2008 964 11.0 153 

153 

4S-3 Ingersoll-Rand 36 KVS 1,000 1 1 10/22/1997 993 11.2 155 

4S-3 Ingersoll-Rand 36 KVS 1,000 1 2 10/22/1997 974 11.2 155 

4S-3 Ingersoll-Rand 36 KVS 1,000 1 3 10/22/1997 967 11.3 161 

157 

4S-3 Ingersoll-Rand 36 KVS 1,000 10 1 9/21/2005 970 11.5 163 

4S-3 Ingersoll-Rand 36 KVS 1,000 10 2 9/21/2005 998 11.5 163 

163 

4S-3 Ingersoll-Rand 36 KVS 1,000 11 1 4/12/2006 906 11.7 168 

4S-3 Ingersoll-Rand 36 KVS 1,000 11 2 4/12/2006 907 11.7 164 

166 

4S-3 Ingersoll-Rand 36 KVS 1,000 3 1 11/3/1998 950 11.3 165 

4S-3 Ingersoll-Rand 36 KVS 1,000 3 2 11/3/1998 926 11.4 166 

4S-3 Ingersoll-Rand 36 KVS 1,000 3 3 11/3/1998 910 11.5 176 

169 

4S-3 Ingersoll-Rand 36 KVS 1,000 8 1 5/30/2001 987 11.8 170 

4S-3 Ingersoll-Rand 36 KVS 1,000 8 2 5/30/2001 980 11.8 170 

170 

4S-3 Ingersoll-Rand 36 KVS 1,000 9 1 3/30/2005 798 11.3 169 

4S-3 Ingersoll-Rand 36 KVS 1,000 9 2 3/30/2005 799 11.4 176 

172 

4S-3 Ingersoll-Rand 36 KVS 1,000 13 1 10/2/2007 951 11.4 180 

4S-3 Ingersoll-Rand 36 KVS 1,000 13 2 10/2/2007 955 11.4 179 

179 

4S-3 Ingersoll-Rand 36 KVS 1,000 15 1 5/14/2009 860 11.5 203 

4S-3 Ingersoll-Rand 36 KVS 1,000 15 2 5/14/2009 862 11.5 205 

204 

4S-3 Ingersoll-Rand 36 KVS 1,000 4 1 4/27/1999 960 11.5 224 

4S-3 Ingersoll-Rand 36 KVS 1,000 4 2 4/27/1999 954 11.6 233 

4S-3 Ingersoll-Rand 36 KVS 1,000 4 3 4/27/1999 952 11.6 241 

233 
Technical Report: Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 

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4S-3 Ingersoll-Rand 36 KVS 1,000 12 1 4/18/2007 799 11.8 274 

4S-3 Ingersoll-Rand 36 KVS 1,000 12 2 4/18/2007 799 11.8 267 

270 

4S-4 Ingersoll-Rand KVH-616 4,200 13 1 8/4/1999 3489 9.87 128 128 

4S-4 Ingersoll-Rand KVH-616 4,200 10 1 8/4/1999 3175 9.89 128 128 

4S-4 Ingersoll-Rand KVH-616 4,200 9 1 8/4/1999 2958 9.94 131 131 

4S-4 Ingersoll-Rand KVH-616 4,200 12 1 8/4/1999 3169 10.19 152 152 

4S-4 Ingersoll-Rand KVH-616 4,200 3 1 8/22/1995 3243 10.27 152 152 

4S-4 Ingersoll-Rand KVH-616 4,200 6 1 8/22/1995 3801 10.29 160 160 

4S-4 Ingersoll-Rand KVH-616 4,200 1 1 8/22/1995 4209 10.29 160 160 

4S-4 Ingersoll-Rand KVH-616 4,200 11 1 8/4/1999 2881 10.49 162 162 

4S-4 Ingersoll-Rand KVH-616 4,200 4 1 8/22/1995 2950 11.10 205 205 

4S-4 Ingersoll-Rand KVH-616 4,200 5 1 8/22/1995 2777 11.10 205 205 

4S-4 Ingersoll-Rand KVH-616 4,200 8 1 8/4/1999 2393 11.11 223 223 

4S-4 Ingersoll-Rand KVH-616 4,200 7 1 8/22/1995 4007 11.12 240 240 

4S-4 Ingersoll-Rand KVH-616 4,200 2 1 8/22/1995 3229 11.12 240 240 

4S-5 Ingersoll-Rand 512 KVS 2,000 3 1 11/4/1998 1967 11.6 127 

4S-5 Ingersoll-Rand 512 KVS 2,000 3 2 11/4/1998 1939 11.6 130 

4S-5 Ingersoll-Rand 512 KVS 2,000 3 3 11/4/1998 1917 11.7 136 

131 

4S-5 Ingersoll-Rand 512 KVS 2,000 5 1 10/30/1999 1949 11.5 155 

4S-5 Ingersoll-Rand 512 KVS 2,000 5 2 10/30/1999 1957 11.5 155 

4S-5 Ingersoll-Rand 512 KVS 2,000 5 3 10/30/1999 1962 11.4 153 

154 

4S-5 Ingersoll-Rand 512 KVS 2,000 4 1 4/28/1999 1910 11.5 152 

4S-5 Ingersoll-Rand 512 KVS 2,000 4 2 4/28/1999 1904 11.5 158 

4S-5 Ingersoll-Rand 512 KVS 2,000 4 3 4/28/1999 1901 11.6 158 

156 

4S-5 Ingersoll-Rand 512 KVS 2,000 15 1 5/14/2009 1820 11.8 157 

4S-5 Ingersoll-Rand 512 KVS 2,000 15 2 5/14/2009 1813 11.9 158 

157 

4S-5 Ingersoll-Rand 512 KVS 2,000 1 1 10/22/1997 1922 11.6 164 

4S-5 Ingersoll-Rand 512 KVS 2,000 1 2 10/22/1997 1961 11.6 164 

4S-5 Ingersoll-Rand 512 KVS 2,000 1 3 10/22/1997 1998 11.6 154 

161 

4S-5 Ingersoll-Rand 512 KVS 2,000 14 1 9/3/2008 1903 11.9 166 

4S-5 Ingersoll-Rand 512 KVS 2,000 14 2 9/3/2008 1902 11.9 164 

165 

4S-5 Ingersoll-Rand 512 KVS 2,000 10 1 9/21/2005 1942 11.6 172 

4S-5 Ingersoll-Rand 512 KVS 2,000 10 2 9/21/2005 1953 11.5 165 

168 

4S-5 Ingersoll-Rand 512 KVS 2,000 12 1 4/18/2007 1672 12.2 169 

4S-5 Ingersoll-Rand 512 KVS 2,000 12 2 4/18/2007 1667 12.2 170 

170 

4S-5 Ingersoll-Rand 512 KVS 2,000 13 1 10/2/2007 1962 11.8 170 

4S-5 Ingersoll-Rand 512 KVS 2,000 13 2 10/2/2007 1958 11.8 169 

170 

4S-5 Ingersoll-Rand 512 KVS 2,000 16 1 8/25/2009 2015 11.5 177 

4S-5 Ingersoll-Rand 512 KVS 2,000 16 2 8/25/2009 2003 11.5 177 

177 

4S-5 Ingersoll-Rand 512 KVS 2,000 9 1 3/30/2005 1674 11.8 186 

4S-5 Ingersoll-Rand 512 KVS 2,000 9 2 3/30/2005 1660 11.8 183 

185 

4S-5 Ingersoll-Rand 512 KVS 2,000 11 1 4/12/2006 2040 11.4 185 185 
Technical Report: Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 

34 

4S-5 Ingersoll-Rand 512 KVS 2,000 11 2 4/12/2006 2035 11.4 184 

4S-5 Ingersoll-Rand 512 KVS 2,000 8 1 5/31/2001 1969 11.3 190 

4S-5 Ingersoll-Rand 512 KVS 2,000 8 2 5/31/2001 1972 11.3 197 

194 

4S-5 Ingersoll-Rand 512 KVS 2,000 7 1 10/2/2000 2037 11.6 211 

4S-5 Ingersoll-Rand 512 KVS 2,000 7 2 10/2/2000 2035 11.5 212 

4S-5 Ingersoll-Rand 512 KVS 2,000 7 3 10/2/2000 2028 11.5 212 

212 

4S-5 Ingersoll-Rand 512 KVS 2,000 6 1 4/4/2000 1626 11.8 218 

4S-5 Ingersoll-Rand 512 KVS 2,000 6 2 4/4/2000 1628 11.8 214 

4S-5 Ingersoll-Rand 512 KVS 2,000 6 3 4/4/2000 1628 11.8 211 

214 

4S-5 Ingersoll-Rand 512 KVS 2,000 2 1 4/28/1998 1714 12.3 207 

4S-5 Ingersoll-Rand 512 KVS 2,000 2 2 4/28/1998 1691 12.6 229 

4S-5 Ingersoll-Rand 512 KVS 2,000 2 3 4/28/1998 1666 12.6 243 

226 

4S-6 Cooper-Bessemer LSV-16SG 4,400 2 3 2/26/2010 4,323 9.6 135 135 

4S-6 Cooper-Bessemer LSV-16SG 4,400 2 1 2/26/2010 3,550 10.3 137 137 

4S-6 Cooper-Bessemer LSV-16SG 4,400 2 2 2/26/2010 3,975 9.9 144 144 

4S-7 Ingersoll-Rand 36 KVS-FT 1,000 3 1 3/23/2006 990 11.8 137 137 

4S-7 Ingersoll-Rand 36 KVS-FT 1,000 8 1 3/23/2006 872 11.0 175 175 

4S-7 Ingersoll-Rand 36 KVS-FT 1,000 10 1 3/23/2006 675 10.9 178 178 

4S-7 Ingersoll-Rand 36 KVS-FT 1,000 5 1 3/23/2006 853 12.1 182 182 

4S-7 Ingersoll-Rand 36 KVS-FT 1,000 11 1 3/23/2006 571 11.2 182 182 

4S-7 Ingersoll-Rand 36 KVS-FT 1,000 7 1 3/23/2006 796 11.0 200 200 

4S-7 Ingersoll-Rand 36 KVS-FT 1,000 4 1 3/23/2006 926 12.2 202 202 

4S-7 Ingersoll-Rand 36 KVS-FT 1,000 6 1 3/23/2006 725 11.9 207 207 

4S-7 Ingersoll-Rand 36 KVS-FT 1,000 9 1 3/23/2006 752 11.2 213 213 

4S-7 Ingersoll-Rand 36 KVS-FT 1,000 1 1 3/22/2006 573 12.4 230 230 

4S-7 Ingersoll-Rand 36 KVS-FT 1,000 2 1 3/22/2006 472 13.4 375 375 

4S-8 Ingersoll-Rand 36 KVS 1,000 5 1 10/31/1999 983 10.4 136 

4S-8 Ingersoll-Rand 36 KVS 1,000 5 2 10/31/1999 981 10.4 140 

4S-8 Ingersoll-Rand 36 KVS 1,000 5 3 10/31/1999 976 10.5 140 

139 

4S-8 Ingersoll-Rand 36 KVS 1,000 7 1 10/2/2000 986 11.2 166 

4S-8 Ingersoll-Rand 36 KVS 1,000 7 2 10/2/2000 986 11.3 166 

4S-8 Ingersoll-Rand 36 KVS 1,000 7 3 10/2/2000 987 11.2 166 

166 

4S-8 Ingersoll-Rand 36 KVS 1,000 14 1 9/3/2008 965 11.4 170 

4S-8 Ingersoll-Rand 36 KVS 1,000 14 2 9/3/2008 968 11.4 170 

170 

4S-8 Ingersoll-Rand 36 KVS 1,000 11 1 4/12/2006 911 11.7 172 

4S-8 Ingersoll-Rand 36 KVS 1,000 11 2 4/12/2006 908 11.6 172 

172 

4S-8 Ingersoll-Rand 36 KVS 1,000 13 1 10/2/2007 977 11.6 173 

4S-8 Ingersoll-Rand 36 KVS 1,000 13 2 10/2/2007 977 11.6 171 

172 

4S-8 Ingersoll-Rand 36 KVS 1,000 16 1 8/25/2009 938 11.5 168 

4S-8 Ingersoll-Rand 36 KVS 1,000 16 2 8/25/2009 936 11.5 176 

172 

4S-8 Ingersoll-Rand 36 KVS 1,000 10 1 9/21/2005 955 11.5 178 

4S-8 Ingersoll-Rand 36 KVS 1,000 10 2 9/21/2005 950 11.5 178 

178 
Technical Report: Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 

35 

4S-8 Ingersoll-Rand 36 KVS 1,000 2 1 4/28/1998 705 10.6 186 

4S-8 Ingersoll-Rand 36 KVS 1,000 2 2 4/28/1998 706 10.6 188 

4S-8 Ingersoll-Rand 36 KVS 1,000 2 3 4/28/1998 706 10.3 166 

180 

4S-8 Ingersoll-Rand 36 KVS 1,000 8 1 5/30/2001 984 11.7 181 

4S-8 Ingersoll-Rand 36 KVS 1,000 8 2 5/30/2001 981 11.8 185 

183 

4S-8 Ingersoll-Rand 36 KVS 1,000 6 1 4/4/2000 802 11.2 185 

4S-8 Ingersoll-Rand 36 KVS 1,000 6 2 4/4/2000 799 11.2 186 

4S-8 Ingersoll-Rand 36 KVS 1,000 6 3 4/4/2000 798 11.3 186 

186 

4S-8 Ingersoll-Rand 36 KVS 1,000 9 1 3/30/2005 763 12.1 196 

4S-8 Ingersoll-Rand 36 KVS 1,000 9 2 3/30/2005 761 12.1 189 

192 

4S-8 Ingersoll-Rand 36 KVS 1,000 1 1 10/22/1997 936 11.3 195 

4S-8 Ingersoll-Rand 36 KVS 1,000 1 2 10/22/1997 904 11.3 195 

4S-8 Ingersoll-Rand 36 KVS 1,000 1 3 10/22/1997 900 11.3 195 

195 

4S-8 Ingersoll-Rand 36 KVS 1,000 3 1 11/3/1998 822 11.5 197 

4S-8 Ingersoll-Rand 36 KVS 1,000 3 2 11/3/1998 816 11.5 197 

4S-8 Ingersoll-Rand 36 KVS 1,000 3 3 11/3/1998 816 11.5 191 

195 

4S-8 Ingersoll-Rand 36 KVS 1,000 15 1 5/14/2009 859 11.7 205 

4S-8 Ingersoll-Rand 36 KVS 1,000 15 2 5/14/2009 856 11.7 203 

204 

4S-8 Ingersoll-Rand 36 KVS 1,000 12 1 4/18/2007 795 12.0 211 

4S-8 Ingersoll-Rand 36 KVS 1,000 12 2 4/18/2007 790 12.1 217 

214 

4S-8 Ingersoll-Rand 36 KVS 1,000 4 1 4/27/1999 901 12.0 301 

4S-8 Ingersoll-Rand 36 KVS 1,000 4 2 4/27/1999 902 11.9 298 

4S-8 Ingersoll-Rand 36 KVS 1,000 4 3 4/27/1999 901 11.8 295 

298 

4S-9 Caterpillar G3516 880 3 1 10/15/2002 785 8.80 142 

4S-9 Caterpillar G3516 880 3 2 10/15/2002 785 8.80 141 

4S-9 Caterpillar G3516 880 3 3 10/15/2002 785 8.80 139 

141 

4S-9 Caterpillar G3516 880 5 1 2/20/2003 747 8.50 157 

4S-9 Caterpillar G3516 880 5 2 2/20/2003 747 8.50 156 

4S-9 Caterpillar G3516 880 5 3 2/20/2003 747 8.50 156 

156 

4S-9 Caterpillar G3516 880 4 1 12/12/2002 806 9.00 160 

4S-9 Caterpillar G3516 880 4 2 12/12/2002 806 9.00 162 

4S-9 Caterpillar G3516 880 4 3 12/12/2002 806 9.00 161 

161 

4S-9 Caterpillar G3516 880 2 1 6/27/2002 861 8.59 190 

4S-9 Caterpillar G3516 880 2 2 6/27/2002 861 8.59 191 

4S-9 Caterpillar G3516 880 2 3 6/27/2002 861 8.61 189 

190 

4S-9 Caterpillar G3516 880 1 1 4/12/2002 659 8.39 183 

4S-9 Caterpillar G3516 880 1 2 4/12/2002 659 8.37 198 

4S-9 Caterpillar G3516 880 1 3 4/12/2002 659 8.33 206 

196 

4S-10 Ingersoll-Rand KVT-512 3,000 1 1 10/25/1995 2712 10.23 149 149 

4S-10 Ingersoll-Rand KVT-512 3,000 6 1 12/27/2006 2823 11.50 183 

4S-10 Ingersoll-Rand KVT-512 3,000 6 2 12/27/2006 2812 11.50 180 

4S-10 Ingersoll-Rand KVT-512 3,000 6 3 12/27/2006 2833 11.50 187 

183 
Technical Report: Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 

36 

4S-10 Ingersoll-Rand KVT-512 3,000 4 1 10/25/1995 2024 11.26 201 201 

4S-10 Ingersoll-Rand KVT-512 3,000 3 1 10/25/1995 2902 10.61 202 202 

4S-10 Ingersoll-Rand KVT-512 3,000 5 1 4/26/2001 2921 11.97 220 220 

4S-10 Ingersoll-Rand KVT-512 3,000 2 1 10/25/1995 2253 10.62 226 226 

4S-11 Ingersoll Rand KVS-412 ~2,050 1 1 9/13/1995 2,044 12.7 156 

4S-11 Ingersoll Rand KVS-412 ~2,050 1 2 9/13/1995 2,007 12.8 156 

4S-11 Ingersoll Rand KVS-412 ~2,050 1 3 9/13/1995 1,793 12.7 146 

153

4S-11 Ingersoll Rand KVS-412 ~2,050 2 1 3/22/2006 1,962 15.0 219 

4S-11 Ingersoll Rand KVS-412 ~2,050 2 2 3/22/2006 1,943 15.0 224 

4S-11 Ingersoll Rand KVS-412 ~2,050 2 3 3/22/2006 1,946 14.8 225 

223

 

NOTE 1: ppmvd @ 15% O2; Values in column are either multi-run average or value of a single test (i.e., a one run test)