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OAR Box 1846 

Prepped by Ollie Stewart 

Document Number: 

9) II-B—6 

Docket Number: 

A-90-07 

Printed 11/18/2008 7:30:14 AM Sheet 9 of 93 
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

ANN ARBOR. MICHIGAN 48105 

HAR 2 -} 13 

MEMORANDUM 

SUBJECT: 

FROM: 

TO: 

THRU: 

OFFICE OF 

AIR AND RADIATION 

Vehicle Selection Procedures for the Proposed Fuels and 

Fuel Additives Rulemaking 

James Greaves, Mechanical Engineer 

Standards Development and Support Branch 

Docket No. A-90-07 

Judith Gray, Project Manager 

Standards Development and Sup 

4&*b(?r&^-~ 

Glenn W. Passavant, Senior Project Manage 

Standards Development and Support Branch 

Chester J. France, Chief 

Standards Development an 

3U^^^M^MM 

pport Branch 

Summary 

This memorandum illustrates how the vehicle selection 

procedure described in the Fuels and Fuel Additives Program Notice 

of Proposed Rulemaking (NPRM) would be performed for gasoline and 

diesel fuels. The results are valid only for the selection of 1991 

model year gasoline and diesel fueled vehicles/engines, but the 

selection method is applicable to other model years and fuel 

families. 

Background 

As part of the proposed Fuels and Fuel Additives Registration 

program implementing Section 211(b)(2) of the Clean Air Act, 

emissions from motor vehicle fuels and fuel additives would be 

generated and tested to determine their composition and potential 

effects on human health. The fuel and additive manufacturers would 

be responsible for selecting and acquiring new vehicles/engines to 

generate these emissions according to criteria specified in the 

NPRM. The proposal requires the use of new vehicles to ensure that 

emissions are attributable to the test fuel or additive/fuel 

mixture. The criteria that determine the vehicle/engine models 

eligible for use in the program are described in Section V(A) (1) of 

the NPRM preamble and Section 79.47(a) of the proposed regulations. 

The proposal specifies that vehicle selection would be performed by 

the fuel and additive manufacturers for the year in which their 
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testing is initiated. The current proposal requires the use of 

emissions from only one vehicle/engine; however, EPA is considering 

an increase in the number of required vehicles/engines to improve 

the accuracy of the program. 

Vehicle/engine selection starts with determining the 

vehicle/engine class and subclass which consume the greatest amount 

of fuel in the fuel family of interest. Next, a survey of the 

engine families within the identified class and subclass from the 

previous model year is performed and the most common emission 

control technology equipment and characteristics are determined. 

The five highest selling engine families with these characteristics 

are then identified. Representatives from these engine families of 

the current model year are selected as the vehicles/engines 

eligible to generate emissions for the program. A diagram of this 

process is shown in Figure 1 and the steps are described in detail 

in this memorandum. 

Selection of Vehicle/Engine Models for Gasoline and Diesel Testing 

Vehicle/engine class refers to the broadest classification of 

vehicles/engines used in the certification of new vehicles (40 CFR 

86) . At the present time there are four on-road vehicle/engine 

classes: light-duty vehicles (LDV), light-duty trucks (LDT), heavyduty engines (HDE), and motorcycles. However, the engines, 

emission control systems, and, therefore, emissions from gasoline 

LDV and LDT are very similar. The LDV and LDT classes are thus 

proposed to be combined for the purpose of this program. The 

proposed vehicle/engine selection method requires that the 

vehicle/engine class that reflects the highest yearly consumption 

of fuel in the fuel family of interest be used to test members of 

the fuel family. Thus, the gasoline fuel family would be 

represented by the combined LDV and LDT classes and the diesel fuel 

family would be represented by the HDE class. 

The next selection criterion is the vehicle/engine subclass. 

Subclass refers to divisions within a vehicle/engine class based 

typically on vehicle/engine size. Subclass is also known as 

"primary intended service class" for HDE. As with vehicle/engine 

class, subclass is chosen to represent the greatest consumption of 

fuel within the fuel family of interest. Not all vehicle/engine 

classes contain subclasses, and the subclass selection process is 

not applicable in these cases. The LDV class does not have 

subclasses; however, the LDT class is currently divided into trucks 

above and below 3750 pounds loaded vehicle weight, and starting in 

1994, a total of four LDT subclasses will be specified. If, as 

proposed, the LDV and LDT are combined for the purposes of this 

rulemaking, the LDT subclass distinctions would not be made, and 

LDV/LDT would be treated as one class with no subclasses. The HDE 

class contains three subclasses--light, medium, and heavy. The HDE 

subclass that represents the greatest annual diesel fuel 

consumption is the heavy subclass (HHDE). 

Once the vehicle/engine class and subclass have been 
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determined, a survey is performed to determine the most common 

emission control technology characteristics within the identified 

class and subclass. The survey procedure makes use of standard 

manufacturer and engine classifications called "engine families," 

which have previously been defined for the purposes of vehicle 

certification (40 CFR 86.082-2 and 86.090-24). First, the engine 

families which pertain to the selected class and subclass are 

listed. Next, the pertinent engine families are sorted into larger 

groups according to similarities in their emission control 

technology characteristics1. Finally, vehicle/engine sales are 

summed across the engine families in each technology group to 

determine the most common engine and emission control 

characteristics. 

The grouping of engine families is to be based on those 

technology systems which, according to good engineering judgment, 

are likely to have the greatest impact on emissions. Thus, they 

may not be as design specific as are some of the criteria used to 

divide families into engine/emission control system combinations. 

Once these systems have been selected, the options for each system 

are identified. For example, the options for catalytic converter 

systems could be 3-way, 3-way plus oxidation, oxidation, and no 

catalytic converter. The options for some variables, such as the 

existence of an exhaust gas recirculation valve, could be yes or 

no. The engine family sales applicable to each option are summed 

separately to determine the system option with the greatest sales. 

This procedure is repeated for the remaining vehicle/engine systems 

identified as most affecting emissions so that a list of the most 

common emission control characteristics is determined. 

Surveys for 1990 model year LDV/LDT and HHDE engine families 

have been performed and the results are presented in Tables 1 and 

2. The light-duty gasoline-fueled vehicle/engine systems 

identified by EPA as most affecting emissions are: fuel system 

type, catalyst type, exhaust gas recirculation valve, air 

injection, feedback, and adaptive learning. The diesel-fueled HHDE 

systems identified by EPA are: fuel injection control type, 

aspiration type, and fuel injection position. As shown in Table 1, 

the most common technology characteristics for light-duty vehicles 

are: multiport fuel injection, a 3-way catalyst with no oxidation, 

closed loop feedback (includes an oxygen sensor), no air injection, 

an exhaust gas recirculation valve, and adaptive learning. Table 

*In some instances there are emission control system 

differences within an engine family which cause engine families to 

be further divided into engine/emission control system 

combinations, also known as engine/system combinations (40 CFR 

86.082-2 and OMS Advisory Circulars 20B and 20B-1). The sorting 

process described above might require the engine/system 

combinations within an engine family to be sorted into different 

technology groups. In general, few engine families have more than 

one engine/system combination, and even fewer would be divided into 

more than one technology group. 
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2 shows that the most common technology characteristics for the 

HHDE are: turbocharger with air-to-air aftercooling, mechanical 

control of fuel injection, and direct injection of fuel into the 

combustion cylinders. 

Once the set of engine families containing the most common 

emission control technology characteristics has been determined, 

the five engine families with the highest sales are identified2. 

Since data concerning current model year engine families could be 

incomplete and difficult to obtain, the survey is to be performed 

over the engine families from the previous model year. However, 

the proposed Fuels and Fuel Additives Registration program 

currently calls for the acquisition of new vehicles/engines to 

generate emissions. Therefore, engine families from the current 

model year corresponding to the engine families selected from the 

survey of the previous model year must be determined and acquired. 

This determination is based on engine and emission control 

equipment similarities between families in the two model years. A 

significant indicator of correspondence would be if data were 

"carried over" from the previous model year engine family for 

current model year engine family certification. 

Finally, once the corresponding engine families from the 

current model year have been identified, a representative must be 

selected from each engine family. The method to be used in this 

program for selecting the appropriate engine family representative 

is the same as that required for vehicle certification purposes. 

Generation of emissions for the certification of light-duty 

vehicles requires an engine operating within a vehicle. The chosen 

vehicle configuration (a unique combination of engine and vehicle 

parameters) is the one expected to produce the largest total mass 

of regulated emissions from that engine family. For heavy-duty 

engines, emissions are generated using the engine on a test stand 

and a vehicle is not required. Thus, the engine code (a unique 

combination of engine parameters) which is expected to produce the 

largest mass of the regulated emissions from that family is 

selected to represent the heavy-duty engine family for the purpose 

of collecting certification emission data. The requirements for 

choosing the vehicle/engine to represent an engine family include 

highest road-load power, largest engine displacement, maximum fuel 

flow calibration, heaviest equivalent test weight, and the 

transmission with the highest numerical final gear ratio (40 CFR 

86. 090-24 (b) (1) (i), (b) (1) (iv) , and (b) (3) (ii))3. 

2Again, the existence of engine/system combinations might 

complicate the process. If the engine/system combinations within 

an engine family are in different technology groups, only the sales 

of the identified engine/system combination are used to determine 

if it is one of the top five sellers. 

3The representative from a selected engine family would have 

to be from an engine/system combination that contained the most 

common emission control technology. 
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The representatives of the five selected engine families would 

be eligible to generate emissions for the Fuels and Fuel Additives 

program. If any of the engine families selected by the survey do 

not have a corresponding current model year engine family, the 

selection would be limited to the remaining engine families. If 

fewer than five engine families were available for the survey (as 

may occur for alternative fuels) the representative of any 

available engine family could be used for testing. 

Alternate Vehicle Selection Scenario in the Fuels and Fuel 

Additives Proposal 

In the preamble of the proposed Fuels and Fuel Additives 

Registration program NPRM, an alternative is presented in which 

emissions would be generated from six vehicles to test a product 

instead of only one. The greater number of vehicles would increase 

the confidence that could be placed on the results of the testing 

by providing a greater amount of emissions test data as well as 

data representing a variety of vehicles common to the of U.S. 

fleet. The method used to select the six vehicles would be similar 

to the selection method described above, with the exception that 

the survey would identify the six most common technology groups 

within the appropriate vehicle/engine class and subclass. These 

groups would represent a range of technology characteristics and, 

therefore, possibly a broader range of emissions and emission 

species. A representative from the engine family with the highest 

sales within each of the six groups would be used to generate 

emissions for the program (presumably the highest emitting 

configuration). The six most common technology groups for gasoline 

and diesel fuels are shown in Tables 3 and 4 for vehicle selection 

for the year 1991. The six groups represent approximately 94 and 

100 percent, respectively, of gasoline-fueled LDV/LDT and dieselfueled HDE sales within the appropriate vehicle/engine class and 

subclass. As a possible variation, more than one representative 

could be selected from the technology group with the highest sales, 

in order to more accurately represent in-use emissions. 

Discussion 

EPA would appreciate comments on the vehicle selection method 

described in this memorandum. Comments are particularly welcome on 

the topics presented in this section. 

EPA usually designs regulatory programs so that their 

implementation does not require regular periodic input from the 

EPA. In this spirit, the proposed Fuels and Fuel Additives program 

would require fuel and additive producers to determine the eligible 

vehicle/engine models for emission generation testing. However, it 

might be more efficient for EPA to play a larger part in vehicle 

selection than has been proposed. Much effort and potentially 

costly errors on the part of the producers could be avoided if EPA 

would yearly present a list of the eligible vehicles/engines. Data 

necessary for the engine family survey process might be difficult 

for fuel and additive producers to obtain. Also, both the 
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producers an EPA would be more assured that testing would be 

performed on eligible engines/vehicles if EPA were to list the 

eligible models. A compromise could be adopted in which EPA would 

present a list of eligible vehicles/engines during the first few 

years of the program only, when much testing would be performed, 

and responsibility shifted to the producers in future years. 

Another option would be for EPA to determine eligible vehicles upon 

specific request from the producers. Comments concerning this 

topic would be appreciated. 

The next discussion topic concerns the number of 

vehicle/engine models eligible to generate emissions for this 

program. Allowing five different models to be eligible for testing 

in each fuel family provides flexibility during vehicle/engine 

selection and acquisition. However, the potential for substantial 

emission variation between eligible models might reduce the 

usefulness and comparability of test results. If only one 

vehicle/engine model were eligible to generate emissions per fuel 

family, the vehicle/engine selection process would be simplified, 

reducing the chances that an ineligible model would be chosen. 

This method would also increase the opportunity for existing base 

fuel data to be compared with additive/base fuel mixture data to 

determine the emissions attributable to the fuel additive. Comment 

is requested on the number of vehicle/engine models per fuel family 

that should be eligible to generate emissions for this program. 

The final issue to be raised for comment is whether the model 

year surveyed to determine the most common emission control 

technology should be altered to allow time for engine/vehicle sales 

data to become available. The proposal states that engine families 

be surveyed from the model year previous to that in which testing 

is initiated. Thus, if testing were to begin in 1994, 1993 model 

year engine families would be surveyed. However, 1993 model year 

engines/vehicles can be produced until December 31, 1993. Thus, 

1993 sales data might not become available until some time in 1994. 

To solve this problem, a cutoff date could be specified. Surveys 

performed before the cutoff date would use engine family data of 

two model years previous, and surveys performed after would use 

engine family data of one model year previous. For example, if the 

cutoff date were April 1 and the survey were performed before April 

1, 1994, then 1992 model year engine families would be surveyed. 

If the survey were performed after April 1, 1994, then 1993 model 

year engine families would be surveyed. Comment is requested on 

whether to adopt this method and, if so, what the cutoff date 

should be. Also, what model year engines/vehicles should be 

acquired for testing when the survey is performed on engine 

families of two model years previous? 
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Figure 1 : Outline of the Vehicle Selection Method 

1. Select vehicle class and subclass with the highest consumption 

of fuel within the fuel family. 

2. Specify the important technology parameters affecting 

emissions for the class/subclass (e.g., fuel system type, catalytic 

converter type, etc.) and specify the possible options for each 

parameter. 

3. Find sales data for each engine family within the vehicle 

class/subclass for the previous model year. 

4. Find data concerning the important technology parameters 

affecting emissions for each engine family within the vehicle 

class/subclass for the previous model year. 

5. Apply the engine family sales data in #3 to the parameter data 

in #4 to determine the sales fraction for each variable in #2 

(e.g., if engine family A accounted for 40% of sales, then the 

catalyst type used in engine family A would have 40% of sales. Sum 

these over all pertinent engine families for each parameter.) 

6. Determine the previous model year engine families which have 

all of the most frequently used technology parameters (as 

determined in #5). 

7. Of the engine families determined in #6, select the five 

engine families with the highest sales. 

8. Determine the current model year engine families that 

correspond to the engine families selected in #7. 

9. For the families determined in #8, find the vehicle 

configurations or engine codes used for certification purposes 

(vehicle configurations are used for light-duty vehicles and engine 

codes are used for heavy-duty engines). 

10. The vehicles/engines found in #9 can be used for the Fuels and 

Fuel Additives Registration program. 
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Table 1 : Projected 1990 Vehicle and Emission Control 

System Technology Distribution s : Light-Duty Gasoline 

Fueled Vehicles and Trucks* 

System or Component 

Fuel System 

Catalyst 

Feedback System 

Air Injection 

Exhaust Gas Recirculation 

Valve 

Adaptive Learning 

Options 

Multi Port 

Throttle Body 

Carburetor 

3-way 

3-way+Oxidation 

Oxidation 

None 

Closed Loop 

Open Loop 

Absent 

Present 

Present 

Absent 

Present 

Absent 

Sales 

Fraction 

(%) 

71.2 

26.9 

2.0 

85.4 

14.3 

0.2 

0.06 

99.6 

0.4 

75.4 

24.6 

77.3 

22.7 

98 

2 

* This data has been taken from Table V.4 of the preamble of the 

Reformulated Gasoline Program Notice of Proposed Rulemaking (56 FR 

31176, July 9, 1991,). These figures reflec t both light-duty 

vehicle and light-duty truck sales. 
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Table 2 : Projected 1990 Vehicle and Emission Control 

System Technology Distributions : Heavy Heavy-Duty 

Diesel Fueled Engines* 

System or Component Options Sales 

Fraction 

ill 

Aspiration TC w/Air-Water Aftercooler 57 

TC w/Air-Air Aftercooler 43 

Natural 0 

Turbo-charged 0 

Fuel System Control Mechanical 

Electronic 

73 

27 

Fuel Injector Position Direct 

Prechamber 

99, 

0, 

Note : TC = turbocharged 

* These figures have been calculated from the 1990 heavy-duty 

diesel engine certification data base and from engine certification 

applications. 
Table 3 : The Six Most Common Technology Groups Based 

on Projected Sales - Light-Duty Gasoline Fueled 

Vehicles* 

p.n 

Group 

1 

2 

3 

4 

5 

6 

Fuel 

System 

Multi 

Multi 

TBI 

Multi 

Multi 

TBI 

Catalyst Air Feedback EGR 

Iniectio n 

Sales 

3-Way Absent 

3-Way Absent 

3-Way Absent 

3-Way+0x Present 

3-Way Present 

3-Way Present 

Cl 

Cl 

Cl 

Cl 

Cl 

Cl 

Loop 

Loop 

Loop 

Loop 

Loop 

Loop 

Valve Fraction 

Present 

Absent 

Present 

Present 

Present 

Present 

(%) 

32.0 

20.8 

20.7 

10.4 

7.6 

2.3 

93.8 

Note : EGR = Exhaust Gas Recirculation 

Multi = Multiport Fuel Injection 

TBI = Throttle Body Fuel Injection 

Cl Loop = Closed Loop 

* This data has been taken from Table V.4 of the preamble of the 

Reformulated Gasoline Program Notice of Proposed Rulemaking (56 FR 

31176, July 9, 1991,). These figures reflect both light-duty 

vehicle and light-duty truck sales. 

X 
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Table 4 : The Six Most Common Technology Groups Based 

on Projected Sales - Heavy, Heavy-Duty Diesel Fueled 

Engines* 

Group 

1 

2 

3 

4 

5 

6 

Aspiration 

TAW 

TAA 

TAA 

TAW 

TAA 

TAW 

Fuel Svstem 

Control 

Mechanical 

Mechanical 

Electrical 

Electrical 

Electrical 

Mechanical 

Fuel Iniector 

Position 

Direct 

Direct 

Direct 

Direct 

Prechamber 

Prechamber 

Sales 

Fraction 

1%1 

37.6 

35.0 

21.5 

5.0 

0.6 

0.2 

99.9 

Note : TAW = Turbocharged with Air-to-Water Aftercooler 

TAA = Turbocharged with Air-to-Air Aftercooler 

* These figures have been calculated from the 1990 heavy-duty 

diesel engine certification data base and from engine certification 

applications.