I/M Lookup Table Update
4% United States
|M^pUIl Environmental Protection
hI Agency
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I/M Lookup Table Update
Transportation and Regional Programs Division
U.S. Environmental Protection Agency
Prepared for EPA by
Sierra Research, Inc.
EPA Contract No. 68-C7-0051
Work Assignment No. 2-03
&EPA
United States
Environmental Protection
Agency
EPA-420-B-00-100
October 2000
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DISCLAIMER NO. 1
The accuracy of the information contained in this database has not been
verified by some of the manufacturers of the vehicles. Inaccuracies
regarding drivetrain configuration (e.g., two-wheel versus four-wheel
drive) and other parameters could affect the safety of dynamometer testing.
In addition, the failure to properly identify vehicles with "traction control"
systems could lead to excessive stress on vehicle components during
dynamometer testing. To minimize the risks associated with such
inaccuracies, it is recommended that vehicles be adequately restrained
during dynamometer testing until the validity of the information in the
database has been confirmed. To minimize the risk of damage to vehicles,
it is recommended that drivers be trained to detect the drive configuration
of all vehicles and to recognize when a traction control system is present.
DISCLAIMER NO. 2
Although the information described in this report has been funded wholly
or in part by the United States Environmental Protection Agency under
Contract No. 68-C7-0051, it has not been subjected to the Agency's peer
and administrative review and is being released for information purposes
only. It therefore may not necessarily reflect the views of the Agency and
no official endorsement should be inferred.
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I/M LOOKUP TABLE UPDATE
Table of Contents
page
1. Introduction 1
2. Sources of Data 3
EPA Certification Database 3
Manufacturer Identification 5
Federal Register Data 5
Vehicle Manufacturers 7
Small-Volume Manufacturers 8
1968-1972 Model Year Data 8
Default Parameters 9
Manufacturer Fuel Economy Data 11
Miscellaneous Additional Sources 12
3. Database Format 13
Lookup Table 13
Database Format 16
4. Computational Methodologies 22
1979 and Newer Vehicles 22
Pre-1979 Model Year Vehicles 33
5. Lookup Table Updates 35
1999 Models 35
Evaporative Fuel Inlet Pressure Test Data 35
Other Modifications 36
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List of Tables
page
1. EPA Certification Data 4
2. Manufacturers Contacted Regarding Vehicle Testability 7
3. Format of EPA I/M Lookup Table 17
4. Data Sources for EPA I/M Lookup Table 23
5. Light-Duty Truck Definitions 26
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1. INTRODUCTION
A number of states have implemented enhanced vehicle emissions inspection and
maintenance (I/M) programs. Vehicles subject to enhanced I/M have exhaust emissions
measured while undergoing "loaded mode" testing, i.e., in which the vehicle is driven on
a standard driving cycle on a chassis dynamometer. One or a combination of the possible
driving cycles listed below are currently being used in the enhanced I/M programs.
1. A 240-second, stop-and-go driving (transient) test called the "IM240."
2. Shorter transient test cycles such as the IM93, IM147 (which are both subsets of
the IM240), or BAR31 tests.
3. A shorter, steady-state test called the "Acceleration Simulation Mode" (ASM)
2525, designed to simulate acceleration during in-use vehicle operation. Although
ASM tests are run at a steady speed, the dynamometer is set to load the vehicle
more than if the vehicle were cruising at a steady speed. "ASM2525" is run at
25% of the load required to accelerate at 3.3 mph/sec (the maximum acceleration
rate on the FTP) at a speed of 25 mph.
4. A second ASM test mode called the "ASM5015 " "ASM5015" is run at 50% of
the load required to accelerate at 3.3 mph/sec (the maximum acceleration rate on
the FTP) at a speed of 15 mph.
To efficiently use one or more of the above tests, an I/M test facility must be able to
quickly and easily adjust the chassis dynamometer power absorption and (in the case of
the IM240 or another transient test cycle) inertia weight settings for each vehicle, so that
the vehicle engine is properly loaded during testing. Under enhanced I/M test guidance
issued by EPA,* the dynamometer settings are to be automatically selected for each
vehicle, based on vehicle parameters entered into the test record by the I/M lane
inspector.
According to the enhanced test guidance, EPA is responsible for supplying an electronic
lookup table that can be used to automatically select the proper dynamometer settings for
* "IM240 & Evap Technical Guidance," U.S. Environmental Protection Agency, EPA420-R-00-007, April
2000, and "Acceleration Simulation Mode Test Procedures, Emission Standards, Quality Control
Requirements, and Equipment Specifications," U.S. Environmental Protection Agency, EPA-AA-RPSD-
IM-96-2, July 1996.
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each particular vehicle. Under contract to EPA, Sierra Research developed and released
in September 1994 an initial version of the Lookup Table that contained both
dynamometer settings and purge/pressure testability data. Subsequent versions have also
been prepared and released by Sierra for EPA. This report addresses Sierra's latest
release (Version 1.8.4) of the Lookup Table. Changes incorporated into Version 1.8.4 of
the table include the addition of 1999 model-year vehicles, deletion of data on alternative
test pressures for conducting the fuel inlet vehicle evaporative control system integrity
(pressure) test, deletion of heavy-duty vehicle data records, correction/addition of test
parameters based on a detailed comparison with I/M test data provided by the state of
Virginia and other independent sources of data, and other miscellaneous updates.
Section 2 of this report provides background on the sources of data used to construct and
update the electronic Lookup Table. Section 3 describes the format of the database and
Section 4 contains the computational methodologies used to construct it. Section 5
provides additional details on the changes incorporated into Version 1.8.4 of the table.
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2. SOURCES OF DATA
Several sources were accessed to obtain necessary vehicle parameter data. Each of these
sources is discussed below, along with a description of the data obtained from each
source.
EPA Certification Database
The primary source of information used to initially develop the Lookup Table was
certification data obtained from EPA's certification databases located on the Wayne State
University mainframe computer in Detroit, Michigan. Pertinent data from this source are
described in Table 1. The listed data were provided by EPA for 1981 and later model
year vehicles (data on curb weight, rather than equivalent test weight, were provided for
some models). In addition, incomplete data for model years 1978-1980 were also
provided. For example, vehicle coastdown times were not provided for most of the
1978-1980 models.
Determination of Model Names - The EPA certification data described above contain
certain model names that are listed in a very cryptic fashion. Cryptic model codes for
GM, Toyota, and New United Motor Manufacturers Inc. (NUMMI) models are used
extensively in the database. Manufacturers of other models identified by coded name
include Chrysler, Ford, Fuji, Isuzu, and Suzuki (Ford and Fuji used cryptic names before
1983 only). Because I/M inspectors will use publicly known model names to identify
vehicles brought in for testing, a method was needed to convert the model codes
contained in the certification database into the proper model names. Accordingly,
additional certification data (for 1979 and later models) containing a "carline code" field
and another database containing a carline code decoder were obtained from EPA. This
information was used to decode most of the model codes.
A SAS program was created to read in the additional certification data and the carline
code decoder database. The two data sets were merged by model year and carline code to
create one data set (for model years 1979-1993) containing the following vehicle
parameters: model year, manufacturer, engine family, model name, equivalent test
weight, axle ratio, test vehicle type, and transmission configuration.
The program then read in all the certification data initially provided by EPA, and kept
only the vehicles associated with the manufacturers using the carline codes. It also
determined whether each model's transmission type was manual, automatic, or either.
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Table 1
EPA Certification Data
• Model year (MDYR)
• Manufacturer (MFR)
• Model (MODL)
• Vehicle type (VTYP)
• Sales class (SACL)
• Altitude code (ALTC)
• Engine type (ETYP)
• Fuel type (FTYP)
• Engine family (ENFM)
• Evaporative family (EVFM)
• Coastdown time (VCDT)
• Displacement (DISP)
• Number of cylinders (#CYL)
• Drive axle weight/full (VAXF)
• Drive axle weight/empty (VAXE)
• Evaporative system type (EVSY)
• Main fuel tank capacity (MTNK)
• Auxiliary fuel tank capacity (ATNK)
• Model code (MDCD)
• Drive type (DRCD)
• Axle ratio (AXLR)
• Transmission configuration (VTRN)
• EPA test type (TTYP)
• Equivalent test weight (ETW)
The combined carline/certification data set and the additional certification data set were
merged by model year, manufacturer engine family, and equivalent test weight. This
process gave an excellent match between the certification data set and the model names,
with only 21 engine family/model records not able to be identified. A subsequent attempt
was made to match these outstanding records with engine family/model combinations
identified in additional certification data (described below) published annually in the
Federal Register.
The outstanding records were matched to possible model names. Because a single data
record in the Federal Register data set can represent several different models, multiple
records were generated in the engine-family-specific vehicle parameter database for most
of the outstanding certification records, with a separate record corresponding to each
possible model.
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Review of model names in the two certification data sets revealed a significant number of
errors and inconsistencies in model naming convention. Accordingly, a list of common
"publicly known" model names was created and merged with the two data sets to
eliminate inconsistent entries. The resulting model names were used in the Lookup Table
to replace corresponding model names and/or codes.
Manufacturer Identification
A separate list of manufacturers was provided by EPA for use in the database. This list,
which includes both the full name and a two-character "EPA Manufacturer Subcode" for
each listed manufacturer, is contained in the Society of Automotive Engineers' (SAE's)
J2008 recommended organization of vehicle service information. These names and
subcodes were merged with the four-character manufacturer abbreviation included in the
EPA certification data to convert the abbreviations to the full names and subcodes
contained in SAE J2008. The resulting subcodes and full names are included in fields 2
and 3, respectively, of the Lookup Table.
For some manufacturers, no match was found between the certification database codes
and entries on the SAE J2008 list. This was particularly true for manufacturers of older
models, some of whom may not be in business at present. For such vehicles, the full
name of the manufacturer (if it could be determined) or (at a minimum) the manufacturer
abbreviation included in the EPA certification database was included in field 3 of the
Lookup Table. Field 2 has been left blank for these vehicles.
Federal Register Data
EPA certification data for each model year are also published annually in the Federal
Register. Based on discussions with EPA's Freedom of Information Officer at
Ann Arbor, it was learned that these data were available in electronic format for model
years 1979-1993.* These data included the following applicable vehicle parameters:
• Model year;
• Manufacturer;
• Model description;
• Engine family;
• Engine displacement;
• Transmission type;
* At the time the first version of the Lookup Table was developed, the 1993 model year was the most recent
for which Federal Register data were available. Subsequent updates to the table have been based on
electronic copies of the vehicle certification and fuel economy data provided directly to Sierra by EPA
technical staff.
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• Inertia weight class;* and
• Actual dynamometer horsepower.**
A program was developed to convert these data into standard ASCII text files. (As
provided by EPA, they were formatted in tabular fashion identically to how they appear in
the Federal Register.) This approach is summarized below.
Federal Register Data Retrieval - A FORTRAN program was written to read Federal
Register data files and print out the year, manufacturer, vehicle type, model name, engine
family, emission control system entries, engine displacement, fuel delivery system,
transmission type, equivalent test weight (ETW), and "actual" dynamometer horsepower.
The program results in a listing that includes each model associated with an engine
family, along with the ETWs listed for each certification vehicle used for a particular
group of models.*** If an engine family has two possible displacements, there would also
be separate records created for each displacement. For example, 30 separate data records
would be created for an engine family with 5 possible models, 3 different ETWs, and 2
displacements, each with a different combination of model, ETW, and displacement. If
both a manual and automatic transmission were listed for a certain engine family test, the
transmission-type entry would be listed in the record as "E" (for either). Otherwise, the
transmission type would be labeled as either "M" for manual or "A" for automatic.
The resulting Federal Register data were merged into the vehicle parameter database. In
addition, Federal Register certification data for the 1973-1978 model years, which were
not available electronically, were entered manually and merged into the vehicle parameter
database as well. Records from the two certification data sources (EPA and the Federal
Register) were compared on the basis of model year, manufacturer, model name, and
engine family. Federal Register records that had identical entries to EPA records in these
four fields were deleted from the database, since the ETW data contained in the EPA
database are more accurate than those contained in the Federal Register data. (The ETWs
contained in the EPA data are specific to the vehicle-engine family combination
identified in each record, whereas ETWs in the Federal Register data are based on the
certification vehicles considered to be representative of a group of vehicle-engine family
combinations.)
This methodology resulted in the use of Federal Register certification data for those
vehicle-engine family combinations (i.e., 1973-1978 models plus some later model
vehicles) for which no records were available in the EPA certification database.
* Equivalent test weight, rather than inertia weight class, was recorded for 1980 and later models.
" This value was recorded only for 1983 and later models.
"* The Federal Register data are a compilation of the results of certification tests submitted by the vehicle
manufacturers. Test results may be submitted for one or more "certification" vehicles considered
representative of a group of models containing the same engine family.
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Vehicle Manufacturers
In addition to the certification data obtained above, additional data related to vehicle
testability were obtained directly from the manufacturers listed in Table 2. These
manufacturers were asked to provide the following information related to the testability
of their models:
• Traction control present;
• Manual traction control disablement possible;
• Anti-lock braking (ABS) present;
• Anti-lock braking disablement possible;
• Four-wheel-drive present;
• Full-time four-wheel-drive; and
• Relevant evaporative control system design information.
Table 2
Manufacturers Contacted
Regarding Vehicle Testability
•BMW
• Chrysler
• Ford
• General Motors
• Honda
• Hyundai
• Isuzu
• Mazda
• Mitsubishi
• Nissan
• Saab
• Subaru
• Toyota
• Volkswagen
• Volvo
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Vehicle testability data received from the manufacturers were incorporated into the
vehicle parameter database and the consolidated Lookup Table.* Possible entries are "Y",
"N", "M", and "U", for yes, no, maybe, and unknown, respectively. "U" was entered for
those models for which no data were received. "M" entries were entered into the vehicle
testability fields for those models that may or may not be equipped with the various
systems described above.
The "M" category is particularly applicable to the Lookup Table, since the aggregated
vehicle records included in that database may contain a combination of vehicles, some of
which are equipped with these systems and some of which are not. An "M" would also
be entered for those models on which one of the above systems (e.g., ABS) was offered
as an option by the manufacturer. As noted during the September 13, 1994 meeting of
the IM240 Test Parameter Subcommittee meeting, ABS and/or traction control systems
may be offered as options on a wide range of models and model years, depending on the
manufacturer. For such vehicles, a determination will need to be made at the time of
inspection as to whether a particular vehicle is equipped with traction control.
Manufacturer Review of Lookup Table - Several manufacturers have reviewed the
various releases of the Lookup Table, and provided corrections and additions to the data.
This includes the three domestic manufacturers (i.e., General Motors, Ford, and Chrysler)
as well as some of the foreign manufacturers. These modifications are included in
subsequent versions of the table.
Small-Volume Manufacturers
Data from small-volume manufacturers (those producing fewer than 5,000 vehicles per
year) are not included in the certification database provided by EPA. They are, however,
included in the Federal Register data set. Available Federal Register data for 1973-1993
models produced by small-volume manufacturers were therefore included in the initial
version of the Lookup Table. Since subsequent updates to the table have been based
primarily on certification data provided directly to Sierra by EPA, 1994 and later models
produced by small-volume manufacturers are not included.
1968-1972 Model Year Data
No certification data, from either the EPA databases or the Federal Register data, were
available for 1968-1972 model year vehicles. Because of the extremely limited nature of
available data from other sources (e.g., annual Automotive News Marketing Data Books
* The approach used to consolidate the full vehicle parameter data set into the Lookup Table data set is
described in Section 3.
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and a listing* of 1972 models compiled and provided to Sierra by Automotive Testing
Laboratories [ATL]), these data are not included in the Lookup Table.
Default Parameters
Default dynamometer parameters, which can be used in cases where model identification
is impossible, were also developed. For Version 1.1 of the Lookup Table, track road-load
horsepower (TRLHP) and inertia weight default values contained in
Section 85.2221(c)(5) of an earlier version of EPA's high-tech guidance were used.
(TRLHP settings for inertia weights of 5500 and 6000 lbs were linearly extrapolated from
the data contained in Section 85.2221(c)(5), which include inertia weights only up to
5000 lbs.) For Versions 1.2 through 1.5.1, the IM240 default values were modified based
on a revised list of defaults** provided by EPA. In addition, ASM default values
developed by EPA*** were incorporated. The revised default values included TRLHP and
generic tire/roll losses (GTRL) on both 8.625" and 20.0" diameter dynamometer rolls.
These values were disaggregated according to both vehicle body style and either number
of cylinders or vehicle test weight.
As part of the development of Version 1.6.1 of the Lookup Table, EPA directed Sierra to
review and determine if the defaults contained in the table should be updated. An
analysis was therefore conducted of the existing default values. Existing Lookup Table
entries were sorted according to body shape, number of cylinders, and model year
grouping. Five model year groups were selected: 1973-80, 1981-84, 1985-89, 1990-94,
and 1995-97. These groups were chosen on a relatively arbitrary basis to determine the
degree of variance and trends in TRLHP and ETW values among model years.
Assuming the observations were normally distributed within each analysis category (i.e.,
body shape/#cylinders/model year group combination), lower-limit confidence intervals
were then calculated for TRLHP and ETW in each category using a Student's-^ test as
follows. Using lower-limit intervals of 5% and 20% recommended by EPA (meaning
that 95% and 80%, respectively, of all observations occur above the interval), appropriate
^-values were looked up from a standard statistical table as a function of sample size n
(e.g., tm for large n is 1.645). The lower limit values for TRLHP and ETW were then
calculated using the following equation:
* "Vehicle Manual: 1972-1978," Automotive Testing Laboratories, Inc., undated.
" "Default IM240 Dynamometer Loading, Test Weights, and Tire Losses," U.S. EPA, June 7, 1995.
"* "ASM2 Procedures and Equipment Specifications, Ver 1.5," U.S. Environmental Protection Agency,
July 6, 1995.
tXG
Lower Limit = ju -
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where u and o are the sample mean and standard deviation, respectively, and t and n are
defined as above.
TRLHP and ETW values resulting from these lower-limit metrics are thus considered
conservative, since they represent underloading of most vehicles in each range.
Several observations were drawn from the results of the above analysis:
• Some shape/cylinder categories exhibited a significant spread in TRLHP and
ETW values across the model year ranges, while others did not.
• There did not appear to be any predominant trend in TRLHP values over time
(i.e., they do not all decline or increase with increasing model year).
• With few exceptions, ETW values appeared to generally increase with model year
(i.e., newer models are heavier on average for a given shape and number of
cylinders).
• There were significant differences in the existing defaults contained in the Lookup
Table, and the 5% and 20% lower-limit intervals.
• A limited number of other year/shape/cylinder categories contained no applicable
data records.
• In almost all cases, there was little difference in the 5% and 20% lower-limit
intervals for either TRLHP or ETW.
It was also noted that no defaults currently exist in the Lookup Table for rotary engines.
TRLHP values associated with rotary engine-equipped vehicles appear roughly
comparable to those of four-cylinder vehicles. However, ETW values for the rotary
vehicles are heavier than the four-cylinder vehicles.
Based on the above results, a decision was made to develop and incorporate updated
default values into Version 1.6.1 of the Lookup Table. The approach chosen to create the
updated defaults included the following elements:
1. New TRLHP and ETW defaults would be developed based on the 20% lower-
limit intervals. Revised ETW defaults would be rounded to the nearest 250
pounds.
2. Model-year-specific defaults would be developed to replace the previous single
set of defaults contained at the beginning of the first (1973-1978 model year)
Lookup Table file. Defaults for year/shape/cylinder containing no data records
would be developed from neighboring model years. Model-year-specific defaults
would not be included for year/shape/cylinder combinations not manufactured in
those years.
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3. Default values for rotary engines would be added to the Lookup Table.
Model-year-specific defaults are now included at the beginning of each model year
grouping in the table. To avoid confusion with the previous default values, new Lookup
Table vehicle identification codes (or "index numbers") have been developed for all
defaults. The convention used for the index numbers contained in the default records is
MY99XX. For example, the first default value for the 1973 model year would have an
index number of 739901, the second 739902, and so on.
Manufacturer Fuel Economy Data
As noted in Sierra's 1997 report* to EPA on the Lookup Table, a comparison of EPA
certification data with other sources of vehicle model and test weight information shows
that use of the certification data as the principal source of information has introduced
some errors into the table. This finding is also supported by comments received from
some of the manufacturers. It is primarily because the certification data do not include a
full listing of all models actually sold by the manufacturers in a particular model year. In
addition, it is apparent that some models that were certified were never actually sold.
As a result of this finding, Sierra recommended to EPA in 1997 that future efforts to
update the Lookup Table be based on fuel economy data that the manufacturers must
submit to EPA. Unlike the certification data, the fuel economy data contain a complete
listing of dynamometer parameters for all models sold by each manufacturer.
At roughly that same time (i.e., circa 1997), EPA also transferred its certification and fuel
economy data from the Wayne State databases mentioned previously to an in-house inter-
relational database system called the Certification and Fuel Economy Information System
(CFEIS). This contractor-developed Oracle-based system is maintained by EPA staff.
While EPA technical staff concurred with Sierra's 1997 recommendation to use
manufacturer fuel economy data as the primary basis for future updates to the Lookup
Table, the switch to the CFEIS system has complicated this transition. According to EPA
database staff, the inter-relational nature of the CFEIS system makes it somewhat difficult
to determine the exact source (i.e., certification or fuel economy submittals) of data
elements extracted from the system. EPA is continuing to investigate this issue, with the
intent being to migrate as soon as possible to using fuel economy data as the primary
source of data for new model year vehicles in future releases of the Lookup Table.
*"VIN-Based Lookup Table," prepared for U.S. Environmental Protection Agency, Sierra Research, Inc.,
Report No. SR97-10-01, October 13, 1997.
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Miscellaneous Additional Sources
Additional ABS and traction control data were also obtained from Tier One, a market
research firm specializing in automotive electronics. The Tier One data, which included
detailed information disaggregated by make, model, model year, and vehicle platform,
were input to the Lookup Table* for those manufacturers that did not supply data directly
to Sierra. In addition, data contained in an all-wheel-drive/traction control guide**
produced by the Colorado Department of Public Health and Environment were reviewed
and incorporated, where appropriate, into the Lookup Table.
Data on pressure testability status and canister location, obtained from the Louisville I/M
program, selected vehicle manufacturers (e.g., Chrysler), and All Data on-line automotive
service manuals, were also incorporated into Version 1.1 of the Lookup Table.
Additional purge and pressure testability data (e.g., the appropriate level of pressurization
to be used) obtained from the vehicle manufacturers were included in subsequent
releases.*** In addition, gas cap adapter data (i.e., which adapters to use with which
vehicles) provided by Stant Manufacturing were incorporated into Version 1.4 and
subsequent releases of the table.
Several independent sources of information regarding vehicle models and test weights
were also accessed during development of Version 1.4 and subsequent releases of the
Lookup Table. These sources include the Kelly Blue Book, the Automotive News
Market Data Book, the Standard Catalog of Imported Cars, and the Standard Catalog of
American Light-Duty Trucks.
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* Tier One data for 1988-1995 models produced by domestic manufacturers were included in Version 1.1
of the Lookup Table. These data were expanded in Version 1.2 to include imported vehicles and the older
domestic models.
" "All Wheel Drive/Traction Control Guide," Colorado Department of Public Health and Environment,
June 1995.
"*As discussed in more detail in Section 5, these data have been deleted from Version 1.8.4 and
subsequent versions of the Lookup Table.
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3. DATABASE FORMAT
A comprehensive vehicle parameter database, disaggregated to the engine family level,
was initially developed from the sources listed in Section 2. This data set was then
collapsed into a more aggregated data set, for distribution to I/M programs as an
electronic Lookup Table. The Lookup Table database is described below, followed by
detailed format specifications for the table.
Lookup Table
The Lookup Table contains fields for data specified by EPA staff, as well as additional
data suggested by the I/M contractors (e.g., canister location). In some cases, data are not
currently available for certain vehicle parameters. Fields for these parameters are
included for future use, but have been left blank in the current version.
The first nine fields in each database record contain vehicle identification entries. These
fields are as follows:
1. Model year;
2. Manufacturer code;*
3. Manufacturer name;
4. Manufacturer division;
5. Public model name;
6. Body style (e.g., sedan, wagon, etc.);
7. Number of cylinders;
8. Engine displacement; and
9. Transmission type.
Following the above entries, each record contains a unique vehicle identification code,
which can be used to cross-reference the record with entries for the same vehicle listing in
other versions of the Lookup Table.**
* The second and third fields both reference the vehicle manufacturer, with the second field being a
two-character code and the third the full name of the manufacturer.
"Vehicle identification codes were changed between Versions 1.1 and 1.2 of the Lookup Table. Versions
1.2 and later releases have consistent vehicle IDs.
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Fields are then provided for the type of fuel burned by the vehicle (only gasoline-powered
and a relatively few alternatively fueled vehicles are currently included in the Lookup
Table), evaporative control system, and the number and location of evaporative canisters.
A simple locational coding system for canister location has been developed, based on the
quadrant codes listed below.
1 = left front
2 = right front
3 = right rear
4 = left rear
M = multiple locations
While much more elaborate (e.g., x/y coordinate systems) locational systems could be
adopted, it is believed that a system that simply identifies general canister locations is
much more likely to be used by I/M inspectors.
A field for the sales class of the vehicle* is then provided. This is followed by fields for
all required IM240 dynamometer settings, e.g., ETW, TRLHP, and 8.625" and 20.0"
GTRL. Because the Lookup Table is disaggregated only to the level described above, a
methodology for aggregating multiple ETW values into the database records contained in
the table has been developed and is explained below. Reasons for excluding certain
vehicle parameters from the Lookup Table are also discussed.
Methodology for Developing Test Parameters by Vehicle Category - In developing this
methodology, a review was conducted of the approach previously employed by EPA to
construct the Lookup Table used by ATL for IM240 testing in Hammond, Indiana, and
Phoenix, Arizona. Under that approach, ETW and TRLHP values were averaged to
obtain a value for each vehicle category. In cases of significant variation within a single
vehicle category, EPA used a somewhat subjective approach that attempted to select
ETW and TRLHP values between the minimum and maximum values for the category so
that (1) the values increased as engine size increased, and (2) there were no
"unreasonable" jumps in values from model year to model year.
An alternative approach to that previously used by EPA has been employed to develop
ETW values for each vehicle category. This methodology follows guidance provided by
EPA to use a conservative approach to compute the test parameters for each vehicle
category. EPA's guidance indicated that (1) an engine should be underloaded, rather than
overloaded, in developing test parameters for the aggregated vehicle categories; and
(2) ETW is more important than TRLHP in setting the dynamometer test parameters. In
accordance with this guidance, the lowest ETW value in each vehicle category was used
for that category. (In cases where a vehicle category contained both EPA and Federal
Register certification data records, the lowest ETW from the EPA certification records
was used.) Vehicle coast down time (VCDT) and drive axle weights (VAXF and VAXE)
'Sales class entries have been simplified in Version 1.4 and subsequent releases of the Lookup Table to
simply identify whether a vehicle was certified as a passenger vehicle or truck.
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corresponding to the selected ETW were then used to compute TRLHP and GTRL,
respectively.* In cases where a corresponding VCDT value was not included in the
certification database for a minimum ETW within a specific vehicle category, the VCDT
corresponding to the ETW value closest to the minimum was used. (A similar
methodology was used in the case of missing drive axle weight data.)
Following the IM240 dynamometer settings, similar dynamometer settings for the two
most common ASM test modes (ASM5015 and ASM2525) have been incorporated into
the Lookup Table, using formulas supplied by EPA.** Fields are then provided for
average drive axle weight, wheelbase, and drive layout code (e.g., front, rear, etc.).
Following that are fields for fuel tank size (to aid in pressure testing) and dynamometer
testability (e.g., four-wheel-drive, traction control, and ABS status).
In keeping with the conservative approach to aggregating test parameters discussed
above, the minimum fuel tank size for a specific vehicle within each vehicle category has
been assumed for that category as well. In cases of yes/no answers that vary across
engine families contained within a single vehicle category, an "M" (for maybe) entry has
been used to indicate the possibility of a particular option. For example, if a single
vehicle category includes both full-time and selectable four-wheel-drive vehicles, an "M"
would be entered in the full-time four-wheel-drive field.
Fields are also included for location codes of the four-wheel-drive selector and manual
traction disablement switch. Version 1.7.2 of the Lookup Table was the first release to
include information provided by the manufacturers (i.e., Volkswagen) on the location of
the traction control disablement switch. It was therefore necessary to develop a standard
nomenclature for mapping the location of the switch. In consultation with Volkswagen, it
was decided to use the same mapping scheme as recently proposed for mapping the
location of the OBDII diagnostic link connector (DLC). This standardization of a single
mapping approach for identifying both items will help avoid inspector confusion in
finding the disablement switch and DLC on individual vehicles.
A field is provided for entry of an upper fuel economy limit, for use as a quality control
check on the testing results. Following that are fields for the testability status of the
vehicle for the EPA and inlet pressure tests, and the EPA and tracer purge tests.***
Comment fields are also provided for each pressure and purge test, to allow entry of the
reason (if applicable) for a vehicle being untestable on that test. In addition, fields are
provided for minimum and maximum test pressures for the two pressure tests. As
discussed in more detail in Section 5, however, all alternative test pressures have been
deleted from the Lookup Table beginning with Version 1.8.2.
* Computational methodologies are described in Section 4.
" "ASM Horsepower Equations," U.S. Environmental Protection Agency, July 1995.
"*No acceptable tracer purge test has been approved by EPA at present.
-15-
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The next-to-the-last field contains the date of the record. There was some confusion in
the past regarding the convention used in modifying the date of each individual Lookup
Table record. Some users believed this date should change with each new version of the
Lookup Table and be consistent for all records contained in that version. Other users felt
the record date should only be changed for those records modified in that version of the
table (i.e., there would be no change of date if the record were not modified). They also
pointed out that each version of the Lookup Table has its own revision date and it makes
little sense to put the same date in all the individual records as well.
After considering this issue, Sierra recommended and EPA agreed that the date of record
will remain the same in succeeding versions of the table, unless a change is made to the
record. Any record in Version 1.8.4 that contains an updated date is therefore either new
or has been modified in some manner.
The final field is the gas cap adapter that should be used in testing the vehicle using the
Stant testing apparatus.
Database Format
Table 3 provides a detailed format listing for the Lookup Table. The data set is formatted
as a series of comma-separated, variable length ASCII text files. To keep the data set at a
manageable size, it has been divided into files of no more than 1 Mb in length. This has
resulted in five data files, covering the following model year ranges:
1. 1973-1978;
2. 1979-1984;
3. 1985-1990;
4. 1991-1996; and
5. 1997-1999.
To aid in proper field identification, comma-separated headings for each field have been
added as the first line in the five data files. The abbreviations used for each field heading
are included in Table 3.
Beginning with Version 1.6.1 of the Lookup Table, actual data values have been deleted
from certain of the Lookup Table fields. These include Fields 21, 23-25, 27-29, and 54.
These fields are now marked as "reserved" in Table 3.
Fields 19 and 20 have been redefined respectively as VINPLC and VINCHAR beginning
with Version 1.7.2 of the table. VINPLC indicates the location of the VIN digit that
identifies the GVWR range of certain makes of light-duty trucks (LDTs) that include
models both under and over 6000 lbs GVWR. VINCHAR includes all VIN characters
that represent LDTs with GVWRs of less than or equal to 6000 pounds. Additional
details on the contents of these fields are provided in Section 4.
-16-
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Table 3
Format of EPA I/M Lookup Table
Maximum
Field
Length*
Name
Abbrev.
Description
1
2
Model Year
MDYR
alphanumeric (last 2 digits, DF=default records)
2
2
Manufacturer Code
MFRC
alphanumeric (2-digit SAE J2008 abbreviation)
3
40
Manufacturer Name
MFRN
alphanumeric (full name)
4
17
Manufacturer Division
DIV
alpha (full name)
5
23
Public Model Name
PNAME
alpha (commonly known name of model)
6
1
Body Style
SHAPE
numeric (l=sedan, 2=station wagon, 3=pickup,
4=sport/utility, 5=minivan, 6=full-size van)
7
2
No. of Cylinders
NCYL
alphanumeric (R = rotary)
8
3
Engine Displacement
DISPLR
numeric (liters, includes decimal, n.n)
9
1
Transmission Type
TRANY
alpha (M=manual, A=automatic, E=either)
10
8
Vehicle Category ID
VCID
numeric, unique code for vehicles with identical entries in
first 8 fields
11
1
Fuel Type
FULTYPE
numeric (l=gasoline, 2=natural gas, others=reserved)
12
2
Evaporative System
EVSYS
numeric (0=not recorded, l=crankcase, 2=canister, 3=tank,
4=none, 5=canister+charcoal air cleaner, 98=various types,
99=other)
13
1
No. of Evap Canisters
NCAN
alphanumeric (V=varies)
14
2
Location of Canisters
LOCAN
alphanumeric (1-4 = vehicle quadrant locations,
FT=on fuel tank, M=multiple locations)
15
2
Sales Class
SACL
alphanumeric (V=vehicle, T=truck, E=either)
16
4
Equivalent Test Weight
ETW
numeric (lbs, nnnnn)
17
4
Inertia Weight Class
IWC
numeric (lbs, nnnnn)
* All fields are comma separated, variable length.
-17-
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Table 3 (continued)
Format of EPA I/M Lookup Table
Maximum
Field
Length*
Name
Abbrev.
Description
18
4
Track Road-Load
TRLHP
numeric (hp, includes decimal, nn.n)
Horsepower (50 mph)
19
2
VIN Digit
VINPLC
numeric (nn)
20
8
VIN Character
VINCHAR
alphanumeric
21
1
(Reserved)
22
4
Tire/Roll Interface
GTRL8
numeric (hp, includes decimal, nn.n)
Losses on 8.625"
Roll at 50 mph
23
1
(Reserved)
24
1
(Reserved)
25
1
(Reserved)
26
4
Tire/Roll Interface
GTRL20
numeric (hp, includes decimal, nn.n)
Losses on 20.0"
Roll at 50 mph
27
1
(Reserved)
28
1
(Reserved)
29
1
(Reserved)
30
4
Total ASM5015
THP5015
numeric (hp, includes decimal, nn.n)
Horsepower
31
4
Total ASM2525
THP2525
numeric (hp, includes decimal, nn.n)
Horsepower
32
4
ASM5015 Horsepower
HP50158
numeric (hp, includes decimal, nn.n)
for 8.625" Roll
* All fields are comma separated, variable length.
-18-
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Table 3 (continued)
Format of EPA I/M Lookup Table
Field
33
34
35
36
37
38
39
40
41
42
43
Maximum
Length* Name
4 ASM2525 Horsepower
for 8.625" Roll
4 ASM5015 Horsepower
for 20.0" Roll
4 ASM2525 Horsepower
for 20.0" Roll
4 ASM5015 Tire/Roll
Interface Losses
on 8.625" Roll
4 ASM2525 Tire/Roll
Interface Losses
on 8.625" Roll
4 ASM5015 Tire/Roll
Interface Losses
on 20.0" Roll
4 ASM2525 Tire/Roll
Interface Losses
on 20.0" Roll
4 Average Drive Axle Wt.
5 Wheelbase
1 Drive Layout Code
1 Full-time 4-Wheel?
Abbrev. Description
HP25258 numeric (hp, includes decimal, nn.n)
HP501520 numeric (hp, includes decimal, nn.n)
HP252520 numeric (hp, includes decimal, nn.n)
GTRL1508 numeric (hp, includes decimal, nn.n)
GTRL2508 numeric (hp, includes decimal, nn.n)
GTRL1520 numeric (hp, includes decimal, nn.n)
GTRL2520 numeric (hp, includes decimal, nn.n)
DAXWT numeric (lbs, nnnn)
WHLBS numeric (inches, includes decimal, nnn.n)
DRLCD numeric (l=front drive, 2=rear drive, 3=selectable
4-wheel-drive, 4=full-time 4-wheel drive, 5=varies)
FWDS alpha (Y,N,M,U)
* All fields are comma separated, variable length.
-19-
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Table 3 (continued)
Format of EPA I/M Lookup Table
Maximum
Field
Length*
Name
Abbrev.
Description
44
1
Location of Four-Wheel
LFWD
alphanumeric (1-8 = vehicle location)
Selector
45
Main Fuel Tank Size
MTNK
numeric (gallons, nn.n)
46
1
Auxiliary Fuel Tank?
ATNKQ
alpha (Y=yes,N=no,M=maybe,U=unknown)
47
Auxiliary Tank Size
ATNK
numeric (gallons, nn.n)
48
1
Traction Control?
TC
alpha (Y,N,M,U)
49
1
Traction Control
TCS
alpha (Y,N,M,U)
Disablement?
50
1
Disablement Switch
LTC
alphanumeric (1-8 = vehicle location)
Location
51
1
Anti-lock Braking?
ABS
alpha (Y,N,M,U)
52
1
ABS Disablement
ABSS
alpha (Y,N,M,U)
Possible?
53
1
2-Wheel-Drive Dyno
DYNTST2
alpha (N,M)
Testing Possible?
54
1
(Reserved)
55
1
(Reserved)
56
3
EPA Pressure Test Status
PRSTAT
alpha (NOT, LOW, MED, HIG, ALT, C A, UNK)
57
3
EPA PT Comments
PRSTCOM
alpha (VLV, CLM, INA, PRT, UNK)
58
4
EPA PT Min. Pressure
EPAMIN
numeric (nn.n in of H20, includes decimal)
59
4
EPA PT Max. Pressure
EPAMAX
numeric (nn.n in of H20, includes decimal)
60
3
Inlet Pressure Test Status
PRSTAT 1
alpha (NOT, LOW, MED, HIG, UNK)
61
3
Inlet PT Comments
PRST1COM
alpha (NYL, INA, B P, UNK)
* All fields are comma separated, variable length.
-20-
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Table 3 (continued)
Format of EPA I/M Lookup Table
Maximum
Field
Length*
Name
Abbrev.
Description
62
4
Inlet PT Min. Pressure
INLPRMIN
numeric (nn.n in of H20, includes decimal)
63
4
Inlet PT Max. Pressure
INLPRMAX
numeric (nn.n in of H20, includes decimal)
64
3
EPA Purge Test Status
PUSTAT
alpha (NOT, LOW, MED, HIG, UNK)
65
3
EPA Purge Test
PUSTCOM
alpha (as needed)
Comments
66
3
Tracer Purge Test Status
PUSTAT 1
alpha (NOT, LOW, MED, HIG, UNK)
67
3
Tracer Purge Test
PUST1COM
alpha (BRP, UNK)
Comments
68
4
Tracer Purge Test
TRCPUMIN
numeric (nn.n in of H20, includes decimal)
Minimum Pressure
69
4
Tracer Purge Test
TRCPUMAX
numeric (nn.n in of H20, includes decimal)
Maximum Pressure
70
9
Date of Record
RDATE
alphanumeric (dd/MMM/yy)
71
1
Gas Cap Configuration
GASCAP
alphanumeric (A,B,C,E,F,G,H,L,0,Z,U,N)
Total
271 (not including commas)
m#
* All fields are comma separated, variable length.
-21-
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4. COMPUTATIONAL METHODOLOGIES
The majority of the vehicle parameter data contained in the I/M Lookup Table were either
imported directly from one of the EPA certification data sets or provided by the
manufacturers. However, it was necessary to compute or otherwise develop the values of
some vehicle parameters. Data sources are summarized in Table 4. More complete
descriptions of a selected number of the vehicle parameters, including the methods and
formulas used for the required computations, are presented below. For ease of reference,
each parameter is referenced by its respective field number in the vehicle parameter
database. The discussion is divided into two separate model-year categories (1979 and
newer, and 1973-1978), due to differences in the type of data available for each
category.* Unless otherwise noted, the information presented for 1979 and newer models
also applies to the older models as well.
1979 and Newer Vehicles
The sources of data for these vehicles are the EPA certification and fuel economy
databases that, prior to 1998, were located on the Wayne State computer system. These
data are now being maintained by EPA on its in-house Oracle database, CFEIS.
Transmission Type (field #9) - The various transmission types contained in the
certification database were aggregated into three categories: manual, automatic, or either.
Vehicle Category Identification Number (field #10) - A unique code was developed and
assigned to each vehicle grouping that had identical entries in fields 1-9. This code
begins with the last two digits of the model year of vehicles included in each category,
followed by additional numbers assigned by Sierra.
Fuel Type (field #11) - Almost all records contained in the Lookup Table are for gasoline-
powered vehicles (fuel type =1). Beginning with the 1997 model year, a limited number
of alternatively fueled vehicle records are included, as follows:
* Data for vehicles produced by small-volume manufacturers are not contained in the EPA certification
database, but are included in the certification data published annually in the Federal Register. As a result,
the information presented below for model years 1973-1978 also applies to all 1973-1993 models
produced by small-volume manufacturers. As noted previously, no 1994 and newer models produced by
small-volume manufacturers are included in the Lookup Table.
-22-
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Fie
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
Table 4
Name
Data Sources for EPA I/M Lookup Table
Source of Data
Model Year
Manufacturer Code
Manufacturer Name
Manufacturer Division
Public Model Name
Body Style
No. of Cylinders
Engine Displacement
Transmission Type
Vehicle Category ID
Fuel Type
Evaporative System Type
No. of Evap Canisters
Location of Canisters
Sales Class
Equivalent Test Weight
Inertia Weight Class
Track Road-Load hp at 50 mph (TRLHP)
VIN Digit
VIN Characters
(Reserved)
Tire/Roll Interface Losses on
8.625" Roll at 50 mph (GTRL8)
(Reserved)
(Reserved)
(Reserved)
Tire/Roll Interface Losses on
20.0" Roll at 50 mph (GTRL20)
Cert database (MDYR)
Code in SAE J2008, based on Cert database (MFR)
Name in SAE J2008, based on Cert database (MFR)
Developed by Sierra, based on Cert database
Developed by Sierra, based on Cert database (MODL)
Unique code developed by Sierra
Cert database (#CYL), manufacturers
Cert database (DISP), manufacturers
Cert database (developed from VTRN)
Unique code developed by Sierra
Cert database (developed from FTYP), manufacturers
Cert database (EVSY), manufacturers
All-Data on-line database, manufacturers
All-Data on-line database, manufacturers
Cert database (SACL)
Cert database (ETW), manufacturers, other independent sources
Computed from ETW
Computed from ETW and VCDT, manufacturers
VIN decoding handbooks
VIN decoding handbooks
Computed from DAXWT
Computed from DAXWT
-23-
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Fie
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
Table 4 (continued)
Name
Data Sources for EPA I/M Lookup Table
Source of Data
(Reserved)
(Reserved)
(Reserved)
Total ASM5015 Horsepower
Total ASM2525 Horsepower
ASM5015 Horsepower for 8.625" Roll
ASM2525 Horsepower for 8.625" Roll
ASM5015 Horsepower for 20.0" Roll
ASM2525 Horsepower for 20.0" Roll
ASM5015 Tire/Roll Interface Losses
on 8.625" Roll
ASM2525 Tire/Roll Interface Losses
on 8.625" Roll
ASM5015 Tire/Roll Interface Losses
on 20.0" Roll
ASM2525 Tire/Roll Interface Losses
on 20.0" Roll
Average Drive Axle Wt. (DAXWT)
Wheelbase
Drive Layout Code
Full-time Four-Wheel-Drive?
Location of Four-Wheel Selector
Main Fuel Tank Size
Auxiliary Fuel Tank?
Auxiliary Fuel Tank Size
Traction Control?
Manual Traction Control Disablement
Possible?
EPA ASM
EPA ASM
EPA ASM
EPA ASM
EPA ASM
EPA ASM
EPA ASM
horsepower
horsepower
horsepower
horsepower
horsepower
horsepower
horsepower
equations
equations
equations
equations
equations
equations
equations
EPA ASM horsepower equations
EPA ASM horsepower equations
EPA ASM horsepower equations
Average of VAXF and VAXE in Cert database
Manufacturers (limited data)
Cert database (developed from DRCD), manufacturers
Manufacturers, Colorado DPHE
Not currently entered
Cert database (MTNK), manufacturers
Assumed=Y, if Cert database contains value for ATNK
Cert database (ATNK)
Manufacturers, Tier One, Colorado DPHE
Manufacturers, Colorado DPHE
-24-
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Fie
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
Table 4 (continued)
Data Sources for
Name
Location of Disablement Switch
Anti-lock Braking?
Anti-lock Braking Disablement
Possible?
2-Wheel-Drive Dyno Testing
(Reserved)
(Reserved)
EPA Pressure Test Status
EPA PT Comments
EPA PT Min. Pressure
EPA PT Max. Pressure
Inlet Pressure Test Status
Inlet PT Comments
Inlet PT Min. Pressure
Inlet PT Max. Pressure
EPA Purge Test Status
EPA Purge Test Comments
Tracer Purge Test Status
Tracer Purge Test Comments
Tracer Purge Test Min. Pressure
Tracer Purge Test Max. Pressure
Date of Record
Gas Cap Configuration
PA I/M Lookup Table
Source of Data
Manufacturers (limited data)
Manufacturers, Tier One
Manufacturers
Sierra, from 4-wheel-drive and traction control data
Louisville I/M program
Manufacturers
No longer populated
No longer populated
Louisville I/M program
Manufacturers
No longer populated
No longer populated
Not currently entered
Not currently entered
Not currently entered
Manufacturers
Manufacturers
Manufacturers
Sierra
Stant Manufacturing
-25-
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Flexible-fuel vehicles (FFVs), with fuel type = 1; and
Dedicated natural gas vehicles, with fuel type = 2.
Equivalent Test Weight (field #16) - For 1994-1996 models, 300 lbs was added to the
curb weight data provided by EPA, and the resulting value rounded to the nearest 125-lb
increment, to compute equivalent test weight (ETW). In some cases, data provided
directly to Sierra by the manufacturers were used in place of the certification data.
Beginning with the 1997 model year records contained in the Lookup Table, the ETW
data incorporate changes in certification test weights specified in the Code of Federal
Regulations (CFR) for heavy light-duty trucks (LDTs). The issue of light-duty truck
definitions is relatively complicated, and confused by the fact that the definitions
contained in the CFR are not the same as those used in previous versions of EPA's high-
tech test guidance. Table 5 is provided below to illustrate the differences between these
definitions.
Table 5
Light-Duty Truck Definitions
Ref.
Category
Weight Range
Light LDT:
0-6,000 lbs GVWR
LDT1
Light LDT under 3,751 lbs LVWa
CFR
LDT2
Light LDT of 3,751-5,750 lbs LVW
Heavy LDT:
6,001-8,500 lbs GVWR
LDT3
heavy LDT of 3,751-5,750 TWb
LDT4
heavy LDT greater than 5,750 TW
High-Tech
Guidance
(June 1996)
LDT1
0-6,000 lbs GVWR
LDT2
6,000-8,500 lbs GVWR
High-Tech
Guidance
(April 2000)
LDT (0-6,000 lbs GVWR)
LDT (6,001-8,500 lbs GVWR)
"LVW = curb weight + 300 lbs, which is equivalent to the equivalent test weight (ETW) values
contained in the EPA I/M Lookup Table for most vehicles. The ETW values are basically rounded
versions of the test weight basis (see next footnote) for each vehicle.
bTW = total weight. TW is equivalent to LVW for all vehicles except MY1994 and later Tier 1
heavy LDTs (e.g., those certified to the Tier 1 standards). For MY1994 and later Tier 1 heavy
LDTs, ALVW is to be used for TW. ALVW is defined as (curb weight + GVWR) / 2.
-26-
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The definitions noted in the table for the June 1996 version of EPA's high-tech guidance
are consistent with those contained in EPA's MOBILE models, but clearly conflict with
the CFR definitions. The August 1998 and later versions of the guidance address this
issue somewhat by eliminating the 1 and 2 after the LDT titles in the standards tables.
According to CFR §86.129-94, test weights for model year 1994 and later heavy LDTs
certified to Tier 1 standards are to be based on adjusted loaded vehicle weight (ALVW).
ALVW is defined as the average of curb weight plus gross vehicle weight rating (i.e.,
[curb weight + GVWR] / 2) in CFR section 86.094-2. EPA also inserted ALVW in place
of LVW for the 5,750 lb breakpoint in the standards in the August 1998 guidance and
indicated this breakpoint is to be used for 1996 and newer vehicles. (The June 1996
version indicated it should be used for 1994+ Tier 1 LDTs.) This is because Tier 1
vehicles were phased in beginning with the 1994 model year, with 1996 being the first
model year with all vehicles certified to Tier 1 standards. EPA's revision to include the
1996 model year as the first year for the 5,750 lb breakpoint eliminates the need for
inspectors to determine whether a 1994-1995 vehicle was certified to the Tier 1
standards, in order to set the appropriate IM240 cutpoints.
The effect of the above requirement is that the proper IM240 test weight for 1996 and
newer heavy LDTs is the average of curb weight plus GVWR. However, it appears that
the 1996 model year certification data provided to Sierra for inclusion in the Lookup
Table did not include ALVW values. A review of ETW values for the 1996 LDTs
included in the table shows few in the 5,500 lbs or greater range. The reason for this
oversight is unclear, but may be related to the transition to the CFEIS system that
occurred at about this same time period. Conversely, a review of 1997 model year and
later data contained in the Lookup Table shows a number of LDTs with heavier ETWs
(up to as much as 8,000 lbs), which clearly reflect the correct use of ALVW.
The significance of this issue is that to properly test all of the 1997 models included in the
table, IM240 programs will either need to have dynamometers that have the capability of
handling inertia weight settings of up to as much as 8,500 lbs, or simply underload the
vehicles relative to how they were initially certified.
Inertia Weight Class (field #17) - These data are computed from the ETW values
contained in the certification database or provided by the manufacturers, using the
approach incorporated into the conversion table contained in CFR §86.129-94. Under
this method, all ETW values are rounded down to the nearest inertia weight class. Thus,
for example, vehicles with ETWs of 3000 and 3250 lbs would both be considered to have
the same inertia weight class of 3000 lbs. For the lighter vehicles (i.e., those with ETWs
less than 3000 lbs), the CFR table includes inertia weight classes in increments of
250 lbs. For ETWs of greater than 3000 lbs, the CFR inertia weight classes are based on
increments of 500 lbs. The same approach is used to compute the inertia weight classes
in the Lookup Table, with all ETWs above 3000 lbs being rounded down to the nearest
500-lb inertia weight class, and all ETWs below 3000 lbs rounded down to the nearest
250-lb inertia weight class.
-27-
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Track Road-Load Horsepower (field #18) - These data are computed from the ETW and
VCDT values contained in the certification database, using the formula contained in
§85.2226(a)(2)(iv) of the high-tech I/M test procedures.* This formula is as follows:
TRLHP = C0.5*ETW/32.2N) * CVf-Vn2)
(550*ET)
where: ET = vehicle coastdown time (VCDT) from 55 to 45 mph
ETW = equivalent test weight (lbs)
Vj = initial velocity in ft/sec equivalent to 55 mph
V2 = final velocity in ft/sec equivalent to 45 mph
As discussed previously, VCDT data were not available for a large portion of the
1979-1980 models contained in the Wayne State databases. For these models, an
alternate method of computing TRLHP values must be used. TRLHP settings for these
models, based on vehicle type and either inertia weight class or number of cylinders, are
selected using the revised IM240 and ASM default values (dated June 7, 1995, and
July 6, 1995, respectively) provided by EPA. For vehicles with inertia weights heavier
than shown in the revised default table, TRLHP values corresponding to the heaviest test
weight for the appropriate vehicle category were used.
In some cases, data provided directly to Sierra by the manufacturers were used in place of
the certification data or default values.
VIN Digit and VIN Characters (fields #19 and 20) - The respective EPA guidance
documents for IM240 and ASM testing contain separate sets of recommended cutpoints
for light trucks with a gross vehicle weight rating (GVWR) of (1) 0-6000 pounds; and
(2) 6001-8500 pounds. As a result, GVWR information is needed for these vehicles in
order to determine the correct emissions standards to which they should be tested.
Version 1.7.2 and subsequent versions of the Lookup Table have therefore been modified
to aid I/M programs in determining the GVWR for a particular vehicle.
To accomplish this, Fields 19 and 20 have been defined as VINPLC and VINCHAR.
(These fields were reserved in the previous version of the Lookup Table.) These fields
are populated for 1981 and later makes of light-duty trucks (LDTs) that include models
both under and over 6000 lbs GVWR. Certain pre-1981 records are also populated, if
available VIN decoding information indicates that 1981+ VIN standardization rules also
apply to these vehicles. Data included in the two fields are as follows:
1. VINPLC indicates the location of the VIN digit that identifies the GVWR range
of the vehicle; and
'Unless otherwise noted, all references to the high-tech test procedures contained in this section refer to the
June 1996 version of the guidance.
-28-
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2. VINCHAR includes all VIN characters that represent LDTs with GVWRs of
less than or equal to 6000 pounds.
As an example of the available information, GVWR range is indicated by the fourth VIN
digit on 1994-95 Ford LDTs, based on the following codes:
• A = Under 3000 lbs • G = 8001-8500 lbs
• B = 3001-4000 lbs ^= 8501-9000^
• C = 4001-5000 lbs •J = 9001-10000 lbs
• D = 5001-6000 lbs • 3 = 10001-14000 lbs
• E = 6001-7000 lbs • 4 = 14001-16000 lbs
• F = 7001-8000 lbs
In this example, VINPLC would be populated with a "4" and VINCHAR would contain
the following entry: "ABCD." The combination of these entries indicates that a 1994-95
Ford LDT that has an A, B, C, or D in the fourth VIN digit will have a GVWR of less
than or equal to 6000 pounds. Users can thus use this information and the VIN entry to
determine whether a particular 1994-95 Ford LDT should be subject to 0-6000 or
6001-8500 pound tailpipe standards.
Generic Tire/Roll Interface Losses on 8.625" Roll (field #22) - These data are computed
from the full and empty drive axle weights (VAXF and VAXE) contained in the Cert
database, using the formula contained in §85.2226(a)(2)(xv) of the high-tech I/M test
procedures and assuming that average drive axle weight (DAXWT) equals
(VAXF+VAXE)/2. The formula is as follows:
GTRL@50mph_8 = (-0.378193) + [(0.0033207) * (DAXWT)]
Generic Tire/Roll Interface Losses on 20.0" Roll (field #26) - These data are computed
from the full and empty drive axle weights (VAXF and VAXE) contained in the
certification database, using the formula contained in §85.2226(a)(2)(xvi) of the high-tech
I/M test procedures and assuming that average drive axle weight (DAXWT) equals
(VAXF+VAXE)/2. The formula is as follows:
GTRL@50mph.20 = (0.241645) + [(0.0020844) * (DAXWT)]
Total ASM5015 Horsepower (field #30) - These data are computed from the following
ASM horsepower equations provided by EPA and the At8, Bt8 and Ct8 default values
provided in §85.2226(a)(2)(xiii):
THP5015 = HP50158 + GTRL@ 15 mph.8
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HP50158 = ETW/250*
GTRL@ 15 mph-8 = {[Atg*(15 mph)] + [Bt8*(15 mph)2] + [Ct8*(15 mph)3]} *
GTRL@ 50 mph.8
where: At8 = 0.76 / 50
Bt8 = 0.33 /2,500
Ct8 =-0.09/ 125,000
Total ASM2525 Horsepower (field #31) - These data are computed from the following
ASM horsepower equations provided by EPA and the At8, Bt8, and Ct8 default values
provided above:
THP2525 = HP25258 + GTRL@ 25 mph.8
HP25258 = ETW/300*
GTRL@25mph.8 = {[At8*(25 mph)] + [Bt8*(25 mph)2] + [Ct8*(25 mph)3]} *
GTRL,g 50 mph_8
ASM5015 Horsepower for 8.625" Roll (field #32) - These data are based on the
following equation, which is presented in SAE Paper No. 891120:
HP50158 = ETW/250
ASM2525 Horsepower for 8.625" Roll (field #33) - These data are based on the
following equation, which is presented in SAE Paper No. 891120:
HP25258 = ETW/300
ASM5015 Horsepower for 20.0" Roll (field #34) - These data are computed from the
following ASM horsepower equations provided by EPA and the At20, Bt20, and Ct20
default values provided in §85.2226(a)(2)(xiii):
HP501520 = THP5015 - GTRL^ 15 mph_20
GTRL@15mph.20 = {[At20*(15 mph)] + [Bt20*(15 mph)2]+ [Ct20*(15 mph)3]} *
GTRL@ 50 mph-20
where: At20 = 0.65 / 50
Bt20 = 0.48/2,500
* This equation is contained in SAE Paper No. 891120.
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= -0.13 / 125,000
ASM2525 Horsepower for 20.0" Roll (field #35) - These data are computed from the
following ASM horsepower equations provided by EPA and the At20, Bt20, and Ct20
default values provided above:
HP252520 = THP2525 - GTRL„ 25 mph-20
GTRL(gj 25 mph-20 = {[At20*(25 mph)] + [Bt20*(25 mph)2] + [Ct20*(25 mph)3]} *
GTRL^ 50 mph_2o
ASM5015 Tire/Roll Interface Losses on 8.625" Roll (field #36) - These data are
computed from the following ASM horsepower equation provided by EPA and the At8,
Bt8, and Ct8 default values provided above:
GTRL@ 15mph-8 = {[Atg*(15 mph)] + [Bt8*(15 mph)2] + [Ct8*(15 mph)3]} *
GTRL@ 50 mph.8
ASM2525 Tire/Roll Interface Losses on 8.625" Roll (field #37) - These data are
computed from the following ASM horsepower equation provided by EPA and the At8,
Bt8, and Ct8 default values provided above:
GTRL@25mph_8 = {[At8*(25 mph)] + [Bt8*(25 mph)2] + [Ct8*(25 mph)3]} *
GTRL@ 50 mph-8
ASM5015 Tire/Roll Interface Losses on 20.0" Roll (field #38) - These data are computed
from the following ASM horsepower equation provided by EPA and the At20, Bt20, and
Ct20 default values provided above:
GTRL@15mph.2o = {[At20*(15 mph)] + [Bt20*(15 mph)2]+ [Ct20*(15 mph)3]} *
GTRL@ 50 mph-20
ASM2525 Tire/Roll Interface Losses on 20.0" Roll (field #39) - These data are computed
from the following ASM horsepower equation provided by EPA and the At20, Bt20, and
Ct20 default values provided in above:
GTRL@25mph-20 = {[At20*(25 mph)] + [Bt20*(25 mph)2] + [Ct20*(25 mph)3]} *
GTRL@ 50 mph-20
Average Drive Axle Weight (field #40) - These data are computed from the full and
empty drive axle weights (VAXF and VAXE) contained in the certification database,
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assuming that DAXWT = (VAXF+VAXE)/2. In some cases, when no value of VAXE is
provided in the Certification database, the DAXWT is calculated as 60% of ETW for
front-wheel-drive sedans and station wagons, and 50% of ETW for all other vehicle
types.
Wheelbase (field #41) - These data are available in non-electronic form in the annual
Automotive News Market Data Books for each model year. In addition, the All
Wheel/Traction Control Guide compiled by the Colorado Department of Public Health
and Environment (CDPHE) also contains wheelbase data. Only limited wheelbase data
provided by the manufacturers (e.g., Ford) have been input to the I/M Lookup Table.
Drive Layout Code (field #42) - The various drive code types contained in the
certification database have been aggregated into three categories: front, rear, or four-
wheel. It is impossible to tell from the certification data whether a vehicle has selectable
or full-time four-wheel-drive. Because of this, the manufacturers were asked to identify
which vehicles had full-time four-wheel drive. These data were used to disaggregate
vehicles equipped with four-wheel-drive into selectable or full-time four-wheel-drive
categories.
Full-Time Four-Wheel-Drive (field #43) - As discussed above, data from the
manufacturers were used to identify which vehicles had full-time four-wheel-drive. Data
from the CDPHE All Wheel/Traction Control Guide were also input, where appropriate,
in cases of missing manufacturer data.
Location of Four-Wheel Selector (field #44) - Due to time and resource constraints, these
data have not been input to the Lookup Table.
Auxiliary Fuel Tank (Yes/No") (field #46) - A "yes" answer is assumed for this entry if the
certification database contains a value for the auxiliary fuel tank size; otherwise, this
entry is assumed to be "no."
Location of Traction Control Disablement Switch (field #50) - Only limited data provided
by the manufacturers (e.g., Volkswagen) have been input to the Lookup Table. As
described in more detail in Section 5, the location codes used in this field are identical to
those proposed for use in mapping the location of OBDII diagnostic link connectors.
EPA Pressure Test Status and Comments (fields #56-57) - These data are based on
pressure testability data obtained from the Louisville I/M program and reasons for
untestability received from selected manufacturers.
Minimum and Maximum Pressures for EPA Pressure Test (fields #58-59") - These fields
have been left blank starting with Version 1.8.2 of the Lookup Table.
Inlet Pressure Test Status and Comments (fields #60-61) - These data are based on
pressure testability data obtained from the Louisville I/M program and reasons for
untestability received from selected manufacturers.
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Minimum and Maximum Pressures for Inlet Pressure Test (fields #62-63) - These fields
have been left blank starting with Version 1.8.2 of the Lookup Table.
Tracer Purge Comments (field #67) - These data are based on reasons for untestability
received from selected manufacturers.
Minimum and Maximum Pressures for Tracer Purge Test (fields #68-69) - These data are
based on data received from selected manufacturers.
Gas Cap Configuration (field #71) - To facilitate gas cap pressure testing, this field
identifies the gas cap adapter type that should be used for testing the vehicle, based on
data received from Stant Manufacturing. A description of the field is provided below.
Field Entry Stant Adapter Descriptor
A
Blue
B
Yellow
C
Red
E
Green
F
Black*
G
Gray
H
Threaded
L
Light Blue (new)
0
Orange (new)
Z
Varies
U
Untestable
N
Unknown or no adapter required
Pre-1979 Model Year Vehicles
The database descriptions, data sources, and computational methodologies presented
above primarily apply to those model years contained in the EPA certification and fuel
economy data provided directly to Sierra by EPA, i.e., for model year 1979 and later. In
addition to those data, Sierra also obtained certification data for the 1979-1993 model
years that were published annually in the Federal Register. These data were similar, but
not identical, to the certification data provided by EPA. (The Federal Register data
included some models that were not included in the EPA databases.) Federal Register
data for model years 1973-1978 were also entered manually. As described previously,
fewer data are available for these earlier model years. Accordingly, the following
'According to Stant, an upgraded black adapter has been developed to address problems that users have
experienced in attempting to test certain Honda models because the fuel fillpipes on these vehicles are
slightly different from SAE specifications. The upgraded adapter can be visually distinguished from the
previous unit based on the presence of a white "gripping ring." Stant intends to continue to use the color
black to describe the upgraded version of this adapter. Since this is how it is coded in the I/M Lookup
Table, no change will be made to the table entries in response to the upgrade.
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methodologies were used to develop the necessary vehicle test parameters (dynamometer
settings) for those models for which only Federal Register certification data are available
(i.e., 1972-1978 models plus some later model vehicles).
Number of Cylinders (field #5) - These values are not included in the Federal Register
database; therefore, this field has been left blank for pre-1979 vehicles for which no data
have been provided by the manufacturers or obtained from other sources.
Equivalent Test Weight (field #IS) - These values are included in the Federal Register
database only for 1980 and later models; therefore, this field has been left blank for pre-
1980 vehicles for which no data have been obtained from independent sources (e.g., the
Automotive News Market Data Book) or provided by the manufacturers.
Inertia Weight Class (field #19) - Inertia weight class (IWC) data were included in the
Federal Register data set for 1979 and earlier models. These values, rounded down to the
nearest 500-lb weight class for IWC values above 3000 lbs and down to the nearest
250-lb weight class for IWC values below 3000 lbs, were used unless better data (e.g.,
from the manufacturers) were available. For 1980 and later models, inertia weight classes
were computed by rounding ETW values in the same manner.
Track Road-Load Horsepower (field #20) - TRLHP settings for IM240 testing were based
on the model-year-specific default values developed by Sierra using the approach
described in Section 2. In some cases, data provided directly to Sierra by the
manufacturers were used in place of the default values.
Average Drive Axle Weight (field #32) - As described above, DAXWT data are needed
to compute GTRL values. Because these data were not published in the Federal Register,
the GTRL values in EPA's revised default table were assumed. The DAXWT values for
pre-1979 vehicles were calculated as 60% of ETW for front-wheel-drive sedans and
station wagons, and 50% of ETW for all remaining vehicle types.
###
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5. LOOKUP TABLE UPDATES
Additional modifications, based on comments received on the previous version of the
Lookup Table, were incorporated into Version 1.8.4 of the table. These changes are listed
below.
1999 Models
1999 model year vehicles, based on manufacturer fuel economy and vehicle certification
data, data submitted by the vehicle manufacturers, and other sources, have been added to
the table. A limited number of models (particularly those manufactured by small-volume
manufacturers) may be missing. Users are encouraged to contact Sierra or EPA directly if
they identify missing models.
Data Parameters - For the 1999 models included in the table, complete dynamometer
loadings and testability parameters have been included. Stant gas cap adapter information
was also added based on a review of the listings contained in the Stant manual.
Default Values - 1999 model-year-specific default values have been included at the
beginning of the records for this model year.
Evaporative Fuel Inlet Pressure Test Data
Data regarding alternative test pressures for use in conducting the fuel inlet vehicle
evaporative control system integrity (pressure) test that were provided in previous
versions of the table have been deleted due to (1) concerns that some of the test pressures
were sufficiently high to create the potential for damaging evap systems; (2) the
infeasibility of identifying suitable test pressures for 1996-1999 model year vehicles due
to the phase-in of vehicles equipped with enhanced evaporative emission control systems
into the in-use fleet; and (3) the fact that no programs have been using the alternative test
pressures. It is recommended that anyone wishing to conduct vehicle pressure testing
follow EPA guidance and use the standard test pressure specified contained therein.
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Other Modifications
Miscellaneous Changes - Information provided by the Virginia Department of
Environmental Quality was used to investigate differences between test data recorded in
its I/M program and information contained in the table. Based on the results of this
review, miscellaneous changes were made related to transmission type, engine
displacement, and division and model names.
Updated information provided by Honda, Mitsubishi, Subaru, Isuzu, and Land Rover
regarding previously existing records was incorporated.
An extensive review was performed of existing records in the table. This resulted in
corrections to (1) TRLHP settings for a few 1994-1995 models; (2) drive layout code
entries for a number of 1978-1998 models (most related to four-wheel-drive options); and
(3) gas cap entries for some 1990-1991 Hondas. In addition, it was noted that a number
of 1997-1998 models included in the table had exceptionally high test weights and
TRLHP. These models appear to be heavy-duty vehicles and should not be included in
the table (which is supposed to contain information on only passenger cars and light-duty
trucks). They were therefore deleted.
Record Date - The date on each record that was either added or modified as a result of the
above changes reflects the release date of Version 1.8.4 of the Lookup Table.
m#
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