EPA-AA-TEB-80-5
Catalyst Effectiveness of High Mileage
In-Use Vehicles
December 1979
by
Lois Platte
Test and Evaluation Branch
Emission Control Technology Division
Office of Air, Noise, and Radiation
United States Environmental Protection Agency
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Catalyst Effectiveness of High Mileage In-Use Vehicles
There has been considerable speculation that fuel switching may have
been a contributing factor to the increased ozone levels experienced in
the Los Angeles area during the recent smog alert. The rationale for
the speculation is that automobiles equipped with catalytic converters
emitted increased hydrocarbons (which through photochemical reactions
form ozone) because of the reduced effectiveness or deactivation of the
catalyst caused by the use of leaded fuel. Many studies are being
conducted to quantify the effect of such misfueling on the amount of
pollutants emitted.
However, this paper focuses on another factor related to the reduced
capacity of the catalyst which also is viewed by some as a contributor
to the air quality problem. The problem is the suspected inadequate
performance of the catalyst due to the effects of deterioration from
aging or mileage accumulation. The "useful life" of light-duty vehicles
has been defined as 50,000 miles or 5 years in Federal regulations. It
is thought by some that the effectiveness of the catalyst on vehicles
that are beyond their "useful life" is drastically reduced. The higher
mileage vehicles may contribute to increased hydrocarbon levels since
many catalyst equipped automobiles now on the road have reached the 5
year or 50,000 mile mark.
To address this issue, this paper will examine the catalyst effec-
tiveness of relatively high mileage vehicles. Previous EPA surveillance
studies of passenger cars have demonstrated that many in-use vehicles
exhibit poor emission performance when compared to the applicable stan-
dards. The causes of the poor performance are misfueling, maladjust-
ments and disablements, and inadequate maintenance of emission com-
ponents. These factors may hinder or block the activity of the cata-
lyst. Thus, the factors must be eliminated or corrected to determine
how well the catalyst performs in reducing emissions. Several EPA
programs have been conducted in which corrective maintenance was per-
formed on in-use vehicles. The data collected in these programs will be
reviewed in an effort to examine the catalyst performance of higher
mileage vehicles that have been restored to a good maintenance state.
Although the concern in the recent Los Angeles pollution episode is with
hydrocarbons, the catalyst effectiveness will be discussed in terms of
all three regulated exhaust pollutants.
It is a matter of debate as to whether or not EPA test vehicles have
been subjected to misfueling. It is questionable whether a vehicle
owner would voluntarily submit his car for emissions testing that was
being conducted by EPA contractors if the owner had misfueled his vehi-
cle. In fact, there is little indication that misfueled vehicles are
recruited in the EPA test programs. Three pieces of information are
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collected in the program which may be used as indications of misfueling.
There are (1) the lead content of the fuel in the vehicle when delivered
for testing, (2) the condition of the fuel tank restrictor, and (3) the
owner's response to a question concerning his use of leaded fuel. The
information gathered on these three items indicates that misfueled
vehicles are not recruited into the EPA test sample to any significant
degree. Thus, for purposes of this study it can be assumed that the
effects of emissions of misfueling are negligible if present at all.
The first program to be reviewed is the Restorative Maintenance
Retesting of Passenger Cars in Detroit. A sample of 1976 and 1977 model
year vehicles were retested over a period of one to one and a half years
of in-use service. All the vehicles were equipped with oxidation cata-
lysts. The accumulated mileage of these vehicles had not reached 50,000
at the final set of tests since the vehicles were less than 2 years old.
Therefore, the data can't be used to directly address the issue of
catalyst effectiveness of vehicles that have passed their "useful life"
point. The data do show however the time trend on catalyst performance
and indicate whether emission performance restorability deteriorates
over time.
Thirteen 1976 model year vehicles were tested in the Detroit program at
three different points in time. The average mileage of the 13 vehicles
was approximately 9,800, 27,400, and 36,400 miles at the respective test
points. The first retest was conducted after approximately one year of
in-use service, while the second retest was conducted after an addi-
tional six months of operation. Six 1977 model year vehicles were
retested once. At the first test the average mileage was approximately
2,600 miles. The second test was performed about six months later at an
average mileage of approximately 19,800 miles.
At each test point, the vehicles underwent a series of restorative
maintenance steps. Each step was followed by a FTP to measure the
maintenance effect on reducing emissions. The maintenance steps fol-
lowed in this program included the correction of maladjustments and
disablements, the repair or replacement of defective parts, and a tune-
up. A maintenance step was performed on a vehicle if the vehicle failed
the emissions standards and required the maintenance performed in that
step.
The test results are given in Figure 1 and 2 for the 1976 and 1977 model
year Detroit vehicles respectively. The HC values given for the 1976
model year retests are affected by one vehicle that has HC measurements
between 32 and 36 gin/mile depending upon the test sequence and set.
These large HC measurements unduly affect the average because they are
so excessive and the sample size is small. The dotted lines given in
Figure 1 indicate the average HC levels without the excessive values.
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The average HC and CO emissions of the restored vehicles return to high
levels in the relatively short time interval between the sets of tests
as is indicated by the results labeled test 1 in the figures. Yet the
average as-received HC and CO emissions were reduced significantly in
each test set following corrective maintenance. The average NOx values
increased slightly for a few of the test sets. The percent of the
vehicles that passed the standards increased from approximately 50% or
less to at least 77% (which represents only 3 failing vehicles). The
passing rates for each test are given in Table 1. Therefore, although
there seems to be some deterioration in the catalyst during its "useful
life," it functions well enough to control emissions to an acceptable
level when the vehicle is restored to a good maintenance state.
Another test program was conducted to gather information on catalyst-
equipped passenger cars which have exceeded their defined "useful life."
A sample of eight St. Louis cars equipped with oxidation catalysts were
tested in the program entitled Restorative Maintenance and Catalyst
Replacement on Very High Mileage Cars in St. Louis. The test vehicles
were sought to obtain a general sample of the popular domestic 1975
model cars with final selection based on odometer reading. The odometer
values ranged from about 71,000 to 138,800 miles. The average mileage
was 104,500.
The first phase of the program involved the usual restorative main-
tenance steps. Figure 3 displays the results of the maintenance actions
in tests 1 through 3. Table 2 gives the corresponding percentages of
the sample vehicles that pass the standards. Even though these vehicles
are significantly beyond their defined "useful life," the final CO and
NOx test results after corrective maintenance are well below the stan-
dard levels. The final average HC level, 1.94 gm/mi, is 23% greater than
the HC standard but is significantly lower than the as-received emission
level. The results suggest that the oxidation catalysts on very high
mileage in-use vehicles are capable of controlling emissions relatively
well.
The average emission levels of 300 catalyst equipped vehicles tested in
a previous program (An Evaluation of Restorative Maintenance on Exhaust
Emissions from In-Use Automobiles, SAE 780082) are displayed on Figure 3
as dotted lines. The 300 car fleet results have been included as a
comparison to a set of restoted vehicles tested at very low mileage
(less than 12,000 miles). These values compared to the high mileage St.
Louis vehicles results indicate that there is some deterioration in the
capacity of the catalyst to control emissions as the vehicle ages and
accumulates mileage.
The second phase of the St. Louis program involved the replacement of
the high mileage catalyst on each of the eight test vehicles. A fourth
FTP was performed following the replacement of the catalyst with a
section of plain pipe to obtain "engine out" emissions. The average HC
and CO "engine out" emissions are respectively 87% and 66% higher than
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the emission levels following corrective maintenance. This is shown by
comparison of test 3 to test 4 results in Figure 3. The dramatic in-
crease in emissions following the replacement of the catalyst with a
section of pipe clearly indicates that the high mileage catalyst is
capable of functioning in reducing HC and CO emissions.
Another FTP was performed following the installation of a new catalyst
on each vehicle. The results are displayed as test 5 in Figure 3. With
the new catalyst, the average HC and NOx levels of the eight vehicles
were reduced to levels that were as low as the low mileage 300 car
fleet. The average CO emissions of the St. Louis sample following
catalyst replacement were not reduced to the level of the 300 car fleet.
Nonetheless, the CO emissions of the new catalyst were comparable to
those of the old catalyst when the vehicles were in a good maintenance
state.
Two additional test programs were conducted that provide information on
catalyst effectiveness in the Los Angeles area. The first program to be
discussed is the Study of Exhaust Emissions from 1975-1979 Passenger
Cars in Los Angeles (Contract No. 68-03-2590). A subsample of 50 vehi-
cles were selected from the total test fleet for the performance of the
restorative maintenance procedures. The 50 vehicles were selected with
a preference for high mileage oxidation catalyst vehicles. Forty-one of
the 50 vehicles subjected to restorative maintenance were 1975-1977
oxidation catalyst vehicles. The non-catalyst vehicles are not con-
sidered in this paper since the principal concern is with catalyst
effectiveness.
The test results for the oxidation catalyst equipped vehicles from the
Los Angeles program are given in Figure 4 and Table 3. Unlike the
results given for the other test programs discussed in this paper, the
average emission values are not reduced to a level less than the stan-
dard following the corrective maintenance. Each of the vehicles se-
lected for maintenance in this program failed the standards on their
as-received test. Because of this selection procedure, the sample is
biased toward poor performance vehicles. However, the emission levels
were significantly reduced following maintenance from the as-received
levels.
The second Los Angeles area test program was conducted on 3-way catalyst
vehicles. Since 3-way catalyst vehicles have been introduced only
recently the test vehicles were not expected to have high mileage. The
average mileage is less than 10,000 miles on these test vehicles. The
sample is included to give an indication of emission performance of
3-way catalyst vehicles at the mileage accumulation stage at which they
are currently operating.
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The Los Angeles study is part of a larger program entitled the Study of
Emissions of_ Passenger Cars in_ Six Cities (Contract No. 68-03-2774).
The Los Angeles program involved the testing of 51 vehicles that under-
went restorative maintenance. Each of these vehicles failed the stan-
dards on their as-received test. The maintenance steps are somewhat
different from previous programs. The first maintenance action was the
correction of "obvious" maladjustments and disablements of the type that
are likely to be discovered in a quick visual underhood inspection. The
second maintenance step involved the replacement of the 0« sensor if it
was found to be non-functional. The last two steps involved the usual
steps of correction of maladjustments and disablements (those not found
in the quick visual inspection) and finally correction of defective
parts and/or a tune-up.
The average test results for the 3-way catalyst vehicles that had res-
torative maintenance are displayed in Figure 5. The figure indicates
that the 3-way system is effective in controlling CO and NOx emissions
at least when these vehicles are relatively new. However, the average
HC emissions are 68% greater than the standard following maintenance.
Only the correction of the "obvious" maladjustments and disablements
have any effect in reducing the as-received HC levels. The HC level was
reduced 14% following that maintenance step.
The percent of vehicles that passed the standards is given in Table 4
for the 3-way catalyst vehicles that were in the restorative maintenance
phase of the Los Angeles study. The passing rate was increased from 0%
to 29% following the maintenance. Most of the failures were related to
the HC standard.
Thus, the relatively low mileage 3-way catalyst vehicles operated in Los
Angeles appear to control CO and NOx to their standards even when tested
in their as-received condition. Most of the vehicles that fail the
standards fail the HC standard.
Based upon the data presented above, the oxidation catalyst is capable
of reducing HC and CO emissions even when the vehicle has advanced well
beyond the defined "useful life." In several studies, the average HC
and CO emission levels of oxidation catalyst vehicles were well below
the standards following restorative maintenance. However, the effec-
tiveness of the oxidation catalyst appears to deteriorate with age and
mileage accumulation.
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Figure 1
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All maladjustments other than
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Major tune-up and replacement
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Figure 2 .
Restorative Maintenance Retesting
Fleet Average Emission Levels of
6 1977 Model..Year Vehicles in Detroit
HC
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All maladjustments
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corrected
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)):ir.cs of Testing : 5/77-8/77
7/V8-10/'/S
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Figure 3
Evaluation of Restorative Maintenance and Catalyst Replacement
On Exhaust Emissions from Eight Very High Mileage Passenger Cars in St. Louis
Average Mileage:104,479
HC
4.0
3.0
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Figure 4
Los Angeles - Contract 68-02-2590
41 Oxidation Catalyst Vehicles
Restorative Maintenance^
2.50
HC2
grains /mile
#1
#2
2.22
•
#3
1.74
#4
1975 Vehicles
N = 13
#1 '
n
J.. JO
#3
1.08
#4
1976 Vehicles
N = 25
.81 .78 .65 .63
K
1977 Vehicles
N = 3
Average
Odometer
62,400 mi.
61,100 mi.
59,257 mi.
grams/mile
42.0
37.6
#1
#2
31.5
#3
27.8
#4
1975 Vehicles
22.6
20.4
#1
#2
14.4
#3
11.7
#4
1976 Vehicles
10.3 10.2 9.3 .LI'2
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#2
#3
#4
1977 Vehicles
2.68
i-,80 -i.78
2
NOx
grams /mile
//I
#2
#3
#4
Test sequence //1-//4 are defined as on Figure 1.
.#1
2.06
n
2.17 2.19
#3
#4
2.33 2.32 2.27
£• • w \J
#1
#2
#3
#4
Dotted lines represent California standards
.9/9.0/2.0 for 1975-76 and .41/9.0/1.5 for
1977.
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' Figure 5
Los Angeles Contract 68-03-2774
Restorative Maintenance Evaluation of Passenger Cars
1978/79 llodel Year Vehicles
1.0-,
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HC
(gin/mi) .
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1234
TEST 8
2.7 zn
Testi? Ilaintcnance performed prior to test
1 As received.
2 Correct any obvious raladjustr.ents or disableuents.
3 Correct or replace 67 sensor.
4 Correct regaining maladjustments and disablements
with readjustments as required.
5 Major tune-up and replacement of defective components.
2.0
2
f
3
lEST
1
f
4 5
HC CO i;_Qx
* California Standards: .41 9.0 1.5
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Table 1
Restorative Maintenance Retesting of Cars in Detroit
Percent Passing Standards
Original Test First Retest Second Retest
Model Test Sequence* Test Sequence* Test Sequence*
Year N_ 1234 1234 1234
1976 13 54 54 85 92 38 38 62 77 54 62 69 77
1977 6 50 100 100 - 50 67 83 - - ' -
* See Figures 1, 2 for descriptions of test sequences
Table 2
Restorative Maintenance and Catalyst Replacement
on Eight Very High Mileage 1975 Cars in St. Louis
Percent Passing Standards
Test
Sequence* Percent Passing
1 13
2 38
3 50
4 0
5 63
* See Figure 3 for descriptions of test sequences.
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Table 3
Los Angeles Contract 68-03-2590
1975-1979 Oxidation Catalyst Vehicles
Restorative Maintenance
Percent Passing
Model Test Sequence
Year N 123^
1975 13 0000
1976 25 0 4 20 28
1977 3 0000
1979 1 0 0 100 100
See Figure 1 for a description of test sequences.
2
This vehicle was not displayed in Figure 1 due to the impracticality
of presenting the results of one vehicle.
Table 4
Los Angeles Contract 68-03-2774
51 1978-1979 3-Way Catalyst Vehicles
Restorative Maintenance
Test Sequence* Percent Passing
1 0
2 20
3 27
4 27
5 29
* See Figure 5 for a description of test sequences.
U.S. GOVERNMENT PRINTING OFFICE. 1980- 651-112/0226
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