Report No. EPA 460/3-88-009
Analytical Support for
Emission Factors Development
and Air Quality Assessment
Work Assignment No. 0-01:
Analysis of California
I/M Review Committee Data
Task 2 Report
Analysis of the Incremental Effect
of the 2500 RPM Test Mode
on FTP Emissions Reductions
prepared for:
U.S. Environmental Protection Agency
September 30, 1988
prepared by:
Sierra Research, Inc.
1521 I Street
Sacramento, California 95814
(916)444-6666
-------
EPA 460/3-88-009
ANALYTICAL SUPPORT FOR
EMISSION FACTORS DEVELOPMENT
AND AIR QUALITY ASSESSMENT
EPA Contract No. 68-03-3474
Work Assignment No. 0-01:
Analysis of California
I/M Review Committee Data
Task 2 Report:
Analysis of the Incremental Effect
of the 2500 RPM Test Mode
on FTP Emissions Reductions
prepared for:
U.S. Environmental Protection Agency
September 30, 1988
prepared by:
Thomas C. Austin
Thomas R. Carlson
Kathryn A. Gianolini
Sierra Research, Inc.
1521 I Street
Sacramento, CA 95814
(916) 444-6666
-------
ANALYTICAL SUPPORT FOR
EMISSION FACTORS DEVELOPMENT
AND AIR QUALITY ASSESSMENT
Task 2 Report:
Analysis of the Incremental Effect
of the 2500 RPM Test Mode
on FTP Emissions Reductions
Table of Contents
page
1. Summary 1
2. Introduction and Methodology 9
3. Results 15
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1. SUMMARY
Under the California vehicle inspection and maintenance program ("Smog
Check"), a 2500 rpm test mode is used in conjunction with an idle
emissions test and an underhood inspection for visually identifiable
defects. Concerns have been raised about the ability of the 2500 rpm
test to correctly identify vehicles that would fail the Federal Test
Procedure (FTP). Foremost among these concerns is that evaporative
emission control systems may purge during the test, causing exhaust
emission concentrations to temporarily exceed the I/M cutpoints.
Analysis of data from the recently completed California I/M Evaluation
Program indicates that the use of the 2500 rpm test is contributing to
the emission reductions achieved under the Smog Check program. FTP
emission reductions achieved on vehicles that only fail the 2500 rpm
test are slightly less than for idle test failures, but significant
emission reductions are still being achieved.
Based on the California data, it does not appear that the 2500 rpm
test is causing any significant number of "false" failures. However,
the vehicles selected for the testing program were obtained from a
screening facility where I/M testing was performed shortly after the
1-
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Figure 1
Failure Rates for 1980
and Later Model Undercover Vehicles
at Smog Check Station
62.0
55.6
"267B"
Idle Failure
2500 Only
Underhood Only
|i|| Overall
California Standards
207(b) Standards
vehicles drove into the facility. This may not represent the typical
preconditioning that exists at official I/M stations, especially in
programs where vehicles must sometimes wait to be tested in a queue of
parked vehicles.
Figure 1 illustrates the incremental effect of the 2500 rpm test mode
on the Smog Check program failure rate. The failure rates shown in
the figure are calculated from test results on a sample of 1980 and
later model vehicles that should have failed the official Smog Check
test based on screening tests conducted by the California Air
-2-
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Resources Board (ARE). As the figure shows, 16.3% of the vehicles
failed only the 2500 rpm test. Because only 62.0% of the vehicles
failed at the first Smog Check station they were taken to, those which
failed only the 2500 rpm test make up about 26% of the total number of
failed vehicles. (38.0% of the vehicles did not fail because they
either contained underhood defects that were not identified or because
of inconsistent tailpipe emission test results between the ARB
•fc
screening test and the Smog Check station. )
Figure 1 also indicates how the use of the federal 207(b) cutpoints
would have affected the test results. Because of the less stringent
idle standards, the overall failure rate drops from 62.0% to 55.6%.
The 2500 rpm-only failure rate increases from 16.3% to 17.4% because
some vehicles which fail both the California idle cutpoints and the
2500 rpm cutpoints fail only the 2500 rpm cutpoints when the federal
idle standards are used.
Figure 2 illustrates the effect of the 2500 rpm test mode on excess
emissions identified. ("Excess emissions" are defined as emissions
above the FTP standards that each vehicle was certified to meet.) As
the figure shows, the addition of the 2500 rpm test increases the
percent of excess emissions identified by approximately 19% for HC,
21% for CO and 8% for NOx.
* As explained in Section 2, some of the vehicles that failed a
screening test but passed at the Smog Check station were included in
the sample after weighting factors had been applied.
3-
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Figure 2
Excess Emissions Identified
at Smog Check Station #1
Idle Failures
2500 RPM Only Idle or 2500
Failure Mode
Overall
1980 and Later Model
Undercover Vehicles That
Should Have Failed.
Table 1 indicates that there were real benefits associated with the
use of the 2500 rpm mode to fail vehicles. As the table shows, the
percentage reduction in FTP emissions achieved as the result of
repairs performed at Smog Check stations was nearly as large for
vehicles that failed only the 2500 rpm test as it was for vehicles
that failed the idle test (irrespective of 2500 rpm test results).
However, the average emissions of the vehicles that failed only the
2500 rpm test were slightly lower than those of the vehicles that
failed the idle test.
Hydrocarbons
Carbon
Monoxide
Oxides of
Nitrogen
-4-
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Table 1
FTP Emission Reductions Achieved
as a Function of Failure Mode
Failure Mode
Idle Failure
2500-Only
Failure
Condition
Before Repair
After Repair
Change
Before Repair
After Repair
Change
Hydrocarbons
2.20 g/mi
1.50 g/mi
32.0%
1.57 g/mi
1.10 g/mi
-29.7%
Carbon
Monoxide
35.4 g/mi
22.6 g/mi
-36.1%
28.3 g/mi
22.4 g/mi
-20.9%
Oxides of
Nitrogen
1.17 g/mi
1.23 g/mi
+5.1%
1.06 g/mi
1.11 g/mi
+4.9%
One of the concerns expressed by vehicle manufacturers about the 2500
rpm test is that it can cause vehicles that have no defects to fail an
I/M program. This is clearly a problem where "pattern failures" occur
as the result of catalyst protection schemes that cause partial
deactivation of the emission control system under extended idle or
immediately following a restart. However, many of these pattern
failure problems can be eliminated through modification of the
preconditioning procedures that are used in I/M programs. (The
restart procedure can be eliminated for some vehicles and the
pass/fail decision can be based on the lowest emission level achieved
during the sampling period.) Although California has not yet
implemented a set of optimized preconditioning routines, analysis of
the California I/M Evaluation Program data indicates that "false"
failures have not been a significant problem.
-5-
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Figure 3
Errors of Commission and Omission
at Smog Check Station #1
CD
QC
LU
Idle Failures
Idle or 2500
Failures
Errors of Commission Errors of Omission
Type of Error
1980 and Later Model
Undercover Vehicles That
Should Have Failed.
Figure 3 shows the error of commission rates (vehicles that fail I/M
but pass FTP) and error of omission rates (vehicles that pass I/M but
fail FTP) that occurred for vehicles that should have failed the I/M
*
test based on screening tests conducted by ARB. As the figure shows,
* It should be emphasized that the error of omission and commission
rates illustrated in the figure is for a sample of vehicles that
already failed a screening test. The error of commission rate for the
fleet is expected to be higher because there are many marginal FTP
failures that cannot be detected by a no-load tailpipe test and an
underhood inspection. The error of omission rate for the fleet is
more difficult to project.
-6-
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less than 1% of the sample failed the I/M emission tests but passed
the FTP. In contrast, 45.5% of the vehicles failed the FTP but did
not fail either the idle or the 2500 rpm test. (Note that the overall
error of omission rate was somewhat lower due to the fact that some
vehicles failed the I/M test due only to underhood inspection
results.) The figure also indicates that the error of commission rate
would have increased from 45.5% to 61.7% without the 2500 rpm test
mode.
Although the analysis seems to indicate that there are significant
benefits associated with the 2500 rpm test in California I/M program,
it should be noted that California enforces a 9.0 psi Reid Vapor
Pressure standard for gasoline. Higher volatility fuels used in other
states would be expected to increase "false failures" caused by
evaporative system purging during the 2500 rpm test. Further study
may be required to determine whether adequate preconditioning can be
done to eliminate false failures when high volatility fuel is used.
Vehicle manufacturers who were asked to provide information on the
extent to which evaporative emission control system designs and purge
schedules may be affecting 2500 rpm failures did not provide
sufficient information for a detailed analysis of purging effects.
Ford did not provide detailed information, but reported that 2500 rpm
testing would cause the purge ports to be exposed. GM also reported
that purging would occur during the 2500 rpm test mode. However, one
manufacturer (Nissan) reported that purge flow does not occur under
2500 rpm operation in park or neutral gear. (EPA indicates that this
7-
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is inconsistent with information reported to EPA by Nissan.) Analysis
of 2500 rpm failure rates for GM, Ford, Chrysler, Honda, Toyota, and
Nissan vehicles indicated that Nissan was the only manufacturer with
no significant 2500 rpm-only failures. None of 31 Nissan vehicles in
the undercover car sample failed only the 2500 rpm test. All other
manufacturers experienced 2500 rpm-only failure rates ranging from
11.1-16.7%.
It should be pointed out that the overall program benefits associated
with 2500 rpm testing do not indicate a lack of problems with the
test. The limited information obtained regarding evaporative purging
schedules indicates that purging could contribute to false failures.
Information EPA has assembled on other types of pattern failures
clearly indicates that there are a number of individual vehicle models
for which high 2500 rpm emissions frequently occur when there are no
defects present. However, our analysis does show that, at least in
California, there is a very small percentage of vehicles failing only
the 2500 rpm test that are capable of passing the FTP standards.
-8-
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2. INTRODUCTION AND METHODOLOGY
Under a contract with the U.S. Environmental Protection Agency (EPA)
for "Analytical Support for Emission Factors Development and Air
Quality Assessment," Sierra Research, Inc. (Sierra) performs a variety
of Work Assignments for the Emission Control Technology Division
(ECTD) of EPA's Motor Vehicle Emissions Laboratory in Ann Arbor,
Michigan. Work Assignment 0-01 directed Sierra to analyze California
I/M data for the ECTD Technical Support Staff (TSS) . Task number 2 of
that Work Assignment required further evaluation of the effects the
the 2500 RPM test mode has on the program.
The direction provided by TSS was as follows:
The contractor shall analyze the Review Committee's ARE data
for the incremental effect of the 2500 rpm mode on failure
rate, excess emissions identified, errors of omission and
commission, inconsistent emission test results, and
unsuccessful repair rate. The contractor shall perform the
analysis for both California and Federal (207(b)) cutpoints.
The contractor shall address whether or not there are
technology, manufacturer, or other patterns to the occurrence
of 2500 rpm failures. Included shall be an assessment of
whether evaporative system purge contributes to observed high
2500-rpm failure rates, through design features such as lack
of purge at idle, small fuel tank capacity, geometry of the
exhaust system and exposure to the fuel tank, or other
relevant factors.
-9-
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Background
Under the California I/M Evaluation Program, "undercover" vehicles
obtained from the general population were given laboratory tests at
ARB's El Monte laboratory prior to being sent to a randomly selected
Smog Check station. All of the undercover vehicles failed an
inspection given by ARB technicians at the "screening facilities" that
were established on a temporary basis in various locations throughout
the South Coast Air Basin. Based on the screening test, these
vehicles should have failed a properly conducted inspection at a Smog
Check station.
Vehicles which either failed or received pre-inspection maintenance at
the first Smog Check station to which they were taken were referred to
as "F sample" vehicles. The emission reductions achieved through
repair of these vehicles were determined by further testing at the ARB
laboratory.
Under the California I/M program, both tailpipe emission concentration
measurements and underhood inspections for visual defects are
included. For 1980 and later models only, a vehicle must pass
hydrocarbon and carbon monoxide standards at both idle and 2500 rpm no
load (with the transmission in park or neutral). (Emission cutpoints
for older vehicles apply only to the idle test mode.) Table 2 shows
the cutpoints that are used for 1980 and later model vehicles under
the California program. As the table shows, the cutpoints that apply
to the 2500 rpm test mode are equal to the 207(b) cutpoints of 220 ppm
HC and 1.2% CO. The idle emission cutpoints are technology specific.
-10-
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Table 2
Tailpipe Emission Standards
for the California Smog Check Program
Category/Description
15 '80+, NO CAT
16 '80+, OX CAT, w/o AIR
17 '80+, OX CAT, w/ AIR
18 '80+, 3WY CAT
Idle HC
(ppm)
150
150
150
100
Idle CO
(%)
2.5
2.5
1.2
1.2
2500 HC
(ppm)
220
220
220
220
2500 CO
(%)
1.2
1.2
1.2
1.2
Non-catalyst vehicles (of which there are almost none) and oxidation
catalyst vehicles not equipped with air injection are tested against a
less stringent CO cutpoint of 2.5%, while all other types of vehicles
must meet the 1.2% cutpoint that applies under 207(b). However, all
vehicles must meet significantly more stringent HC cutpoints than
those that apply under 207(b). Three-way catalyst equipped vehicles
must meet a 100 ppm cutpoint at idle while other vehicles must meet a
150 ppm cutpoint.
All of the test data compiled during the testing of the undercover
vehicles were used by Sierra to estimate the benefits of the current
Smog Check program. The same database has been used to provide more
detailed analyses requested by TSS.
-11-
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Methodology
In order to provide the information TSS was seeking, the undercover
car sample had to be divided into several different categories. To
determine the effect of the 2500 rpm test, vehicles that failed only
the 2500 rpm test were isolated from the rest of the sample. In
addition, vehicles were also segregated based on whether they would
have failed the 207(b) idle cutpoints. Within each of the vehicle
groupings based on I/M emission measurements, the sample was also
segregated by technology type and make (manufacturer).
A variety of computations were performed for each of the categories
into which the vehicles were divided. These included overall failure
rate and failure mode [for both California and 207(b) standards],
changes in FTP emissions associated with the repair of failed
vehicles, error of commission and omission rates, percent of excess
emissions identified, and the percent of "unsuccessful" repairs.
In the analysis conducted for the draft version of this report, a
group of 65 vehicles referred to as the "X-sample" were excluded from
the analysis. These vehicles were originally deleted from the sample
because they passed the I/M test at the ARB laboratory, even though
they failed at the "screening facility". EPA speculated that these
vehicles may have been "pattern failure" vehicles that only passed at
the ARB laboratory because of differences in preconditioning. If this
was the case, inclusion of these vehicles would reduce the apparent
benefits of the 2500 rpm test mode in identifying excess emissions and
errors of commission would be expected to increase.
-12-
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Further analysis by Sierra indicated that 17 of the 65 vehicles were
(incorrect) underhood-only failures at the screening facility. These
seventeen vehicles did not fail the tailpipe test, so they were not
pattern failures. All the remaining 48 vehicles in the X-sample
passed the tailpipe test at Smog Check station 1. 43 of the 48 were
•&
1980 or later model vehicles.
Given the observed pattern of failures for the X-sample, Sierra does
not believe it is appropriate to include the 43 tailpipe failure
vehicles in the sample with equal weighting. In fact, an argument
could be made that they should not be included at all because the way
vehicles were preconditioned at the screening facility does not
represent the Smog Check station environment. (Routine analysis of
Smog Check station data indicates that it is common for mechanics to
run repeated "initial" tests on failing vehicles until they pass.)
In this analysis, however, the 1980 and later model X-sample vehicles
with tailpipe failures were included in the sample with a one-third
* As might be expected, the FTP emission characteristics of the 43
1980 and later model X-sample vehicles were different from the other
vehicles that failed at the screening facility:
Sample
X- Sample
Others
HC
0.68
1.46
-- grams/mij.e -•
CO
9.57
24.30
NOx
0.79
1.34
In addition, the failure characteristics of the X-Sample vehicles were
significantly different. While 14.4% of the other vehicles were 2500
rpm-only failures, the 2500-only failure rate for the X-Sample was
53.5%.
13-
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weighting factor to account for the fact that they failed at one-third
of the test sites. This increase the total sample of 1980 and later
models from 243 to 286.
Sierra and its subcontractor Radian attempted to obtain information
from vehicle manufacturers regarding the extent to which evaporative
emission control system designs and purge schedules may be affecting
2500 rpm failures; however, the results did not provide sufficient
information for a detailed analysis of purging effects. The plan had
been to further segregate the undercover vehicles by evaporative
system design characteristics before computing I/M statistics and FTP
emission results. Unfortunately, little detailed information was
supplied by manufacturers. Ford did not provide detailed information,
but reported that 2500 rpm testing would cause the purge ports to be
exposed. GM also reported that purging would occur during the 2500
rpm test mode. However, one manufacturer (Nissan) reported that purge
flow does not occur under 2500 rpm operation in park or neutral gear.
All of the analyses conducted are summarized in the following section
of the report.
-14-
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3. RESULTS
Table 3 presents the results of the basic analysis of how the 2500 rpm
test mode affected the I/M test results. The table also shows how the
use of federal 207(b) standards would have affected the results.
(Data shown in the table for "all vehicles" were presented earlier in
Figure 1.) It should be noted that the "sample size" column in the
table relects a 3.0 multiplier applied to all vehicles that were not
Table 3
Failure Rates for 1980 and Later Model
Undercover Vehicles
Failure Rates (%)
California Cutpoints Federal 207(b) Cutpoints
Sample Sample 2500 Idle or 2500 Idle or
Group Size Idle Only 2500 Overall Idle Only 2500 Overall
All Vehicles
No Catalyst
CARB/OXD
CARB/OXD/AIR
CARB/3WAY
CARB/3CL
CARB/3CL/OXD
FI/3CL
Chrysler
Ford
GM
Honda
Nissan
Toyota
772
35.2 16.3 51.6 62.0
26.6 17.4 43.9
31
65
231
95
96
134
22
36
29
23
64
32
.6
.9
.4
.2
.6
.1
9
21
18
16
1
17
.7
.5
.2
.8
.0
.9
32.
58.
47.
40.
65.
50.
3
5
6
0
6
0
41.
76.
63.
55.
75.
50.
9
9
2
8
0
0
55.6
18
49
179
49
30
319
128
16.
6.
38.
42.
56.
31.
46.
7
1
0
9
7
7
1
33.3
14.3
15.1
14.3
3.3
23.5
2.3
50.0
20.4
53.1
57.1
60.0
55.2
48.4
66
38
56
75
80
68
53
.7
.8
.4
.5
.0
.3
.1
33.
12.
34.
42.
30.
22.
23.
3
2
1
9
0
6
4
16.7
8.2
15.1
14.3
13.3
27.0
2.3
50.0
20.4
49.2
57.1
43.3
49.5
25.8
66.7
38.8
54.2
75.5
63.3
63.6
32.8
19.4
32.3
18.6
25.3
37.5
20.2
9.7
26.2
18.6
13.7
4.2
25.4
29.0
58.5
37.2
39.0
41.7
45.5
38.7
76.9
51.5
54.7
63.5
45.5
-15-
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in the "X-Sample". (The actual number of vehicles was 286. The 772
number is derrived from 243 vehicles being multiplied by 3.0 and 43
X-Sample vehicles being added.)
It also should be noted that the sum of the vehicles in each
technology group does not equal the total sample size. Several
vehicles were coded as 3-way catalyst, closed-loop vehicles without
oxygen sensors. Vehicles with this inconsistent combination of
descriptors were not included in the technology specific analysis.
The table shows eight different failure rates for several different
vehicle groupings. Four of the failure rates are associated with the
California standards and four are associated with the federal 207(b)
standards. Under the column entitled "Idle" is the percentage of
vehicles that failed the idle test irrespective of any other test
results (i.e., 2500 rpm failure or underhood). Under the column
entitled "2500 Only" is the percentage of vehicles that failed the
2500 rpm test but not the idle test nor the underhood inspection.
Under the column entitled "Idle or 2500" is the percentage of vehicles
that failed any of the tailpipe cutpoints. Under the column entitled
"Overall" is the percentage of vehicles that failed for any reason,
including underhood failures.
As the table shows, 62.0% of the 1980 and later model undercover
vehicles failed the California emission standards when they were taken
to the first Smog Check station. Of the 38.0% that did not fail, most
contained underhood defects that were not identified. As covered in
-16-
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our Task 5 report under this work assignment ("Analytical Support for
Emission Factors Development and Air Quality Assessment, Analysis of
California I/M Review Committee Data, Task 5 Report: Analysis of
Inspection Inconsistencies Between Different I/M Test Sites," Sierra
Research, Inc., September 30, 1988.), some of the vehicles also passed
at the Smog Check station because of inconsistent tailpipe emission
test results between the screening facility and the Smog Check
station.
Table 3 also indicates that the 2500 rpm test mode increased the
failure rate by 16.3% from what it would have been with only the idle
standards. Without the 2500 rpm test, the tailpipe failure rate would
have been reduced from 62.0% to 45.7%. In addition, the table shows
that the substitution of the federal 207(b) standards would have
reduced the overall failure rate from 62.0% to 55.6%. Note that the
drop in failure rate occurs within the "Idle" category. Because of
the less stringent federal idle standards, the 2500 rpm-only failure
rate increases from 16.3% to 17.4%. (Some vehicles which fail both
the California idle cutpoints and the 2500 rpm cutpoints fail only the
2500 rpm cutpoints when the federal idle standards are used. However,
for two categories [no catalyst and oxidation catalyst-only] the
federal CO idle standard is more stringent than California's,
resulting in a higher idle failure rate.)
Table 3 also shows that the 2500 rpm-only failure rates for GM, Ford,
Chrysler, Honda, Toyota, and Nissan vehicles indicate that Nissan is
the only manufacturer with no significant 2500 rpm-only failures.
-17-
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None of 31 Nissan vehicles in the undercover car sample failed only
the 2500 rpm test. All other manufacturers experienced 2500 rpm-only
failure rates ranging from 9.7-21.5%. Although these results are not
conclusive, it is interesting that the only manufacturer who reported
no evaporative purging under 2500 rpm conditions had the lowest 2500
rpm-only failure rate.
Table 4 shows the error of commission (false failure) and error of
omission (false pass) rates for the undercover cars using both the
California and federal 207(b) cutpoints. As was shown earlier in
Figure 3, there has been no significant problem with errors of
commission if an error of commission is defined as an I/M test failure
of a vehicle that will pass the FTP standards it was certified to
meet. As the table shows, only 25 of 763 tests (3.3%) passed the FTP
standards when tested at the ARB laboratory. However, the error of
commission rate was computed to be only 0.4% based on tailpipe test
results. This is because only one of the seven vehicles that could
pass the FTP failed a tailpipe test. The other six contained
underhood defects that were a legitimate reason for failure whether or
not the FTP standards were exceeded.
Based on tailpipe test results only, overall error of omission rates
were 45.5% for the California standards and 53.0% for the federal
207(b) standards when the 2500 rpm test mode was included. (This
error of omission rate is reduced somewhat by the failure of vehicles
based only on underhood inspection results.) As indicated in Table 4,
the elimination of the 2500 rpm test and the use of the federal 207 (b)
-18-
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Table 4
Undercover Car Commission and Omission Rates
1980 and Later Vehicles
1/M Stringency: California
Sanrole
All Vehicles 763
No Catalyst 18
CARB/OXD 49
CARB/OXD/AIR 176
CARB/3WAY 46
CARB/3CL 30
CARB/3CL/OXD 319
FI/3CL 125
Chrysler 31
Ford 62
GM 228
Honda 95
Nissan 96
Toyota 131
Commission Rates (%)
Passing Idle or
FTP Idle 2500 Diff
25
0
3
3
0
7
11
1
0
0
7
6
7
5
0.7
_
0.0
0.0
-
13.3
0.0
0.8
_
-
0.0
0.0
4.2
0.8
— — • • .
0.9
_
0.0
0.0
-
13.3
0.6
0.8
-
0.4
0.0
4.2
1.5
— —
0.2
_
0.0
0.0
-
0.0
0.6
0.0
_
-
0.4
0.0
0.0
0.8
Omission Rates (%)
Failing Idle or
FTP Idle 2500. Diff.
738
18
46
173
46
23
308
124
31
62
221
89
89
126
61.7
83.3
87.8
59.7
54.4
33.3
64.9
52.8
77.4
61.3
67.1
70.5
32.3
64.1
45.5
50.0
73.5
44.3
39.1
30.0
42.0
50.4
67.7
38.7
49.1
53.7
31.3
46.6
16.2
33.3
14.3
15.3
15.2
3.3
22.9
2.4
9.7
22.6
18.0
16.8
1.0
17.6
Sample
All Vehicles 763
No Catalyst 18
CARB/OXD 49
CARB/OXD/AIR 176
CARB/3WAY 46
CARB/3CL 30
CARB/3CL/OXD 319
FI/3CL 125
Chrysler 31
Ford 62
GM 228
Honda 95
Nissan 96
Toyota 131
I/M Stringency: Federal 207 (b)
Commission Rates (%) Omission Rates (%)
Passing Idle+ Failing Idle+
FTP
25
0
3
3
0
7
11
1
0
0
7
6
7
5
Idle
0
0
0
0
10
0
0
0
0
3
0
.4
.
.0
.0
.0
.0
.0
.0
_
.0
.0
.1
.0
2500
0
0
0
0
10
0
0
0
0
3
0
.7
_
.0
.0
.0
.0
.6
.0
.
.4
.0
.1
.8
Diff.
0.
_
0.
0.
0
0.
0.
0.
_
-
0.
0.
0.
0.
3
0
0
0
0
6
0
4
0
0
8
FTP
738
18
46
173
46
23
308
124
31
62
221
89
89
126
Id
70
66
81
63
54
56
74
75
80
66
78
68
58
75
le
.3
.7
.6
.6
.3
.7
.0
.2
.7
.1
.1
.4
.3
.6
2500
53.0
50.0
73.5
48.3
39.1
43.3
47.7
72.8
71.0
38.7
59.7
54.7
54.2
50.4
Diff.
17.3
16.7
8.2
15.4
15.2
13.4
26.3
2.4
9.7
27.4
18.4
13.7
4.2
25.2
-19-
-------
outpoints would have increased the error of omission rate from 45.5%
to 70.3%. Considering the relatively small sample sizes for
technology groupings and individual manufacturers, there do not appear
to be major differences between the different groupings.
Table 5 presents the percent of excess emissions (emissions in excess
of the FTP standards) that were identified by the various combinations
of test mode and cutpoint stringency. As shown earlier in Figure 2,
Grout)
All Vehicles
No Catalyst
CARB/CXD
CARB/CKD/AIR
CARB/3WAY
CARB/3CL
CARB/3CL/CKD
FI/3CL
Chrysler
Ford
GM
Honda
Nissan
Toyota
Sample
Size
763
18
49
176
46
30
319
125
31
62
228
95
96
131
HC
61.9
19.2
26.1
71.0
74.6
88.9
48.9
74.2
9.1
68.9
40.1
37.8
90.6
61.4
Idle
CO
58.7
12.6
31.9
63.4
73.9
94.8
39.3
79.0
4.1
69.9
32.0
19.1
97.0
60.4
NOx
29.7
22.2
1.1
23.2
68.7
0.0
27.1
41.0
31.3
19.7
27.5
18.9
39.8
36.5
Table 5
Excess Emissions Identified by Short Tests
Undercover Car Data
1980 and Later Vehicles
I/M Stringency: California
Excess Emissions Identified (Z)
2500 Only Idle+2500
HC CO NOx HC CO NOx
18.7
43.9
20.6
16.8
5.6
8.2
30.8
0.2
51.6
8.6
31.7
29.0
0.4
25.6
21.1
54.6
37.1
21.8
5.0
0.2
36.6
0.2
58.2
8.4
32.0
44.3
0.0
30.8
8.2
34.5
9.2
10.8
12.1
53.5
7.5
2.7
0.0
23.9
5.7
12.4
0.0
4.7
80.
63.
46,
88.
80.
97.
79.
74.
60.
77,
71.
66.
91.
87.
.6
.1
,7
.5
.3
.1
,6
.4
,6
.4
.9
,7
,0
.0
79
67
68
85
79
95
75
79
62
78
64
63
97
91
.8
.2
.9
.2
.0
.0
.8
.2
.3
.3
.0
.4
.0
.2
37
56
10
34
80
53
34
43
31
43
33
31
39
41
.9
.7
.2
.0
.8
.5
.7
.8
.3
.6
.2
.3
.8
.2
Overall
HC CO NOx
87,
80.
46.
89.
86.
100.
87.
85.
70.
83.
88.
77,
92.
87.
.3
.9
.7
0
'.5
,0
,8
.6
.0
.0
.3
,8
.0
.0
89.
87.
68,
85.
89.
100.
39.
95.
69.
88
91,
81.
97.
91.
.9
.6
.9
.2
.6
,0
.8
.2
.1
.4
.4
.1
.4
.2
53.
100.
42.
47.
80.
83,
58.
44
52,
56
51.
54,
51,
41
.8
.0
.2
.9
,8
,7
.1
.0
.9
.1
.9
.6
.9
.2
Grouu
All Vehicles
No Catalyst
CARB/OXD
CARB/CKD/AIR
CARB/3WAY
CARB/3CL
CARB/3CL/OXD
FI/3CL
Chrysler
Ford
GM
Honda
Nissan
Toyota
Sample
Size
763
18
49
176
46
30
319
125
31
62
228
95
96
131
HC
57.9
27.7
43.1
67.4
74.6
78.1
44.2
67.7
7.2
67.8
36.0
40.9
84.7
44.3
Idle
CO
56.3
25.8
65.9
57.8
73.9
86.6
37.8
76.2
3.1
68.7
32.2
21.3
92.2
48.0
NOx
20.4
22.1
2.8
15.9
68.7
0.0
21.0
16.6
30.2
18.0
17.0
18.9
12.7
31.6
I/M Stringency: Federal 207(b)
Excess Emissions Identified (Z)
2500 Only Idle+2500
HC CO NOx HC CO NOx
35.3
3.5
20.9
5.6
18.0
3.0
0.2
51.6
9.6
35.0
25.1
3.3
41.2
25.6 8.4
41.5
3.0
27.0
5.0
6.7
45.8
0.2
58.2
9.6
40.7
42.1
1.8
43.7
34.5
7.5
10.5
12.1
53.5
8.3
2.7
0.0
25.6
5.8
11.8
0.0
6.6
79.5 81.9 28.8
63.1
46.7
88.3
80.3
96.1
80.2
67.9
67.2
68.9
84.8
79.0
93.4
83.5
76.4
56.7
10.2
26.4
80.8
53.5
29.3
19.4
58.8
77.4
71.0
66.0
88.0
85.5
61.3
78.3
72.8
63.4
94.0
91.7
30.2
43.6
22.8
30.7
12.7
38.3
Overall
J3£_
84.8
80.9
46.7
88.8
86.5
99.0
84.2
79.8
68.2
83.0
82.1
77.0
90.3
85.5
CO
88.3
87.6
68.9
84.8
89.6
98.4
86.9
93.4
68.1
88.4
86.9
81.1
96.2
91.7
NOx
47.4
100.0
42.2
47.6
80.8
83.7
54.8
19.6
51.8
56.1
41.5
54.0
47.9
38.3
-20-
-------
the inclusion of the 2500 rpm test mode increased the percent of
excess emissions identified from 61.9% to 80.6% for HC, from 58.7% to
79.9% for CO, and from 29.7% to 37.9% for NOx. The underhood
inspection failures further increased the excess emissions
identification rate. Considering sample sizes, there are no major
differences between the manufacturer and technology groupings.
Table 6 is a repeat of Table 1 from the summary. The table shows that
there were additional emission reductions achieved with the use of the
2500 rpm mode to fail vehicles . The percentage reduction in FTP
emissions achieved as the result of repairs performed at Smog Check
stations was nearly as large for vehicles that failed only the 2500
rpm test as it was for vehicles which failed the idle test
(irrespective of 2500 rpm test results). Since the vehicles were
repaired based on their test results relative to the California I/M
stringency (rather than to the federal) , the reductions in FTP
emissions could only be calculated relative to the California I/M
cutpoints. HC reductions after repair were about 30% for both 2500
rpm-only and idle failures. CO reductions after repair for idle
failures were 36.1% compared to 20.9% for 2500 rpm-only failures.
Both groups experienced slight NOx increases of about 5%. The table
also indicates that the average emissions of the vehicles that failed
only the 2500 rpm test were slightly lower than those of the vehicles
that failed the idle test. The grams per mile emission reductions
associated with the repair of 2500 rpm-only failures are therefore
less than for idle failures.
-21
-------
Table 6
FTP Emission Reductions Achieved
as a Function of Failure Mode
Failure Mode
Idle Failure
2500-Only
Failure
Condition
Before Repair
After Repair
Change
Before Repair
After Repair
Change
Hydrocarbons
2.20 g/mi
1.50 g/mi
-32.0%
1.57 g/mi
1.10 g/mi
-29.7%
Carbon
Monoxide
35.4 g/mi
22.6 g/mi
-36.1%
28.3 g/mi
22.4 g/mi
-20.9%
Oxides of
Nitrogen
1.17 g/mi
1.23 g/mi
+5.1%
1.06 g/mi
1.11 g/mi
+4.9%
Finally,- Table 7 shows the unsuccessful repair (waiver) rates as a
function of failure mode. The values in the table are the percentage
of vehicles failing each individual test mode/cutpoint stringency
combination that did not pass the after repair I/M test and received a
waiver. There is a lower waiver rate for 2500 rpm-only failures.
This indicates that there is no greater problem getting vehicles that
only fail the 2500 rpm test to pass an after repair test.
-22-
-------
Sample
Group
All Vehicles
No Catalyst
CARB/OXD
CARB/OXD/AIR
CARB/3WAY
CARB/3CL
CARB/3CL/OXD
FI/3CL
Table 7
Unsuccessful I/M Repair Rates
for 1980 and Later Model Undercover Vehicles
Sample
Size
154
Unsuccessful Repair Rates (%)
California Cutpoints Federal Cutpoints
2500 Idle or 2500 Idle or
Idle Only 2500 Idle Only 2500
30.4 17.6
26.6
36.9
17.6
30.3
4
8
32
13
6
68
23
100.0
0.0
14.3
42.9
25.0
35.7
35.3
100.0
0.0
0.0
0.0
20.0
100.0
0.0
10.3
37.5
25.0
29.2
33.3
100.0
50.0
20.0
42.9
33.3
38.1
50.0
100.0
0.0
0.0
17.4
100.0
100.0
33.3
14.8
37.5
33.3
27.7
54.5
tt' ft ff
-23-
------- |