A Stu(
Mandatory Engine Maintenance
for Reducing Vehicle Exhaust Emissions
Volume I. Executive Summary
FINAL REPORT
July 1973
In Support of:
APRAC Project Number CAPE-13-68
for
Coordinating Research Council, Inc.
Thirty Rockefeller Plaza
New York, New York 10020
TRW/
TRANSPORTATION &
ENVIRONMENTAL
OPERATIONS
ONf SPACf PARK • ReoOMDO BfACH CALIfOflHIA 90?'8
and
Environmental Protection Agency
Air Pollution Control Office
5600 Fishers Lane
Rockville, Maryland 20852
SCOTT RESEARCH LABORATORIES, INC
P. O. BOX Z4I«
SAN BERNARDINO CALIFORNIA »4O*
-------
A Study of
Mandatory Engine Maintenance
for Reducing Vehicle Exhaust Emissions
Volume I. Executive Summary
FINAL REPORT
July 1973
In Support of:
APRAC Project Number CAPE-13-68
for
Coordinating Research Council, Inc.
Thirty Rockefeller Plaza
New York, New York 10020
TRW/
TRANSPORTATION*
'eNVIRONMENTAL
OPERATIONS
Oil SftCC '/>«« • OlDOMOC B[*C» CILI>O«II'
and
Environmental Protection Agency
Air Pollution Control Office
5600 Fishers Lane
Rockville, Maryland 20852
SCOTT RESEARCH LABORATORIES. INC
r. o. BOX *«i«
tAN BtMNAWOIHO. CALiroKNIA M4O*
-------
PREFACE
This report, "A Study of Mandatory Engine Maintenance for Reducing
Vehicle Exhaust Emissions," consists of eight volumes. The following
are the subtitles given for each volume:
o Executive Summary, Volume I, Final Report, July 1973
o Mandatory Inspection/Maintenance Systems Study, Volume II,
Final Report, July 1973
o A Documentation Handbook for the Economic Effectiveness
Model, Volume III, Year End Report, July 1972
o Experimental Characterization of Vehicle Emissions and
Maintenance Studies, Volume IV, Year End Report, July 1972
o Experimental Characterization of Service Organization
Maintenance Performance, Volume V, Year End Report, July 1972
o A Comparison of Oxides of Nitrogen Measurements Made with
- Chemiluminescent and Non-Dispersive Radiation Analyzers,
Volume VI, Year End Report, July 1972
o A User's Manual and Guide to the Economic Effectiveness
Computer Program, Volume VII, Final Report, July 1973
o Experimental Characterization of Vehicle Emissions and
Maintenance States, Volume VIII, Final Report, July 1973
The first volume summarizes the general objectives, approach and
results of the study. The second volume presents the results of a manda-
tory inspection/maintenance system study conducted with a computerized
system model which is described in Volume III. The experimental programs
conducted to develop input data for the model are described in Volume IV
(Interim Report of 1971-72 Test Effort), V, VI and VIII. Volume VII is a
user's manual for the computer code and Volume VIII reports the experi-
mental program and data obtained in the final test phase of the investiga-
tion.
The work presented herein is the product of a joint effort by TRW
Systems Group and its subcontractor, Scott Research Laboratories. TRW,
as the prime contractor, was responsible for overall program management,
experimental design, data management and analysis, and the economic effec-
tiveness study. Scott acquired and tested all of the study vehicles.
Scott also provided technical assistance in selecting emission test pro-
cedures and in evaluating the test results.
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A STUDY OF MANDATORY ENGINE MAINTENANCE PROCEDURES
FOR REDUCING VEHICLE EXHAUST EMISSIONS
TABLE OF CONTENTS
1.0 INTRODUCTION 1
2.0 GENERAL STUDY CONCLUSIONS 4
2.1 Experimental Program 4
2.2 Inspection and Maintenance Procedures 5
2.3 System Sensitivity Analysis 6
2.4 Regional Implications of Vehicle Inspection
and Maintenance 7
3.0 EXPERIMENTAL PROGRAM 8
3.1 San Bernardino and Detroit Surveys of
Engine Adjustments 8
Diagnostic Content of Exhaust Emissions Measured in
Selected Modes 12
3.2 Experiment to Establish the Relationship Between
Engine Adjustments and fxhaust Emissions 13
3.3 Engine Adjustment and Exhaust Emissions Deterioration
Experiment 17
Engine Adjustment Deterioration Rates 19
Engine Component Failure Rates 19
3.4 Evaluation of Garage Maintenance Effectiveness 26
4.0 ECONOMIC EFFECTIVENESS STUDY 29
4.1 Evaluation of Alternative Programs 29
5.0 ANNOTATED BIBLIOGRAPHY 39
11
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LIST OF FIGURES
Figures Page
3-1 Comparison of San Bernardino & Detroit
Emission & Engine Adjustment Distributions .... 14
4-1 Emission Time Histories for an Extensive
Maintenance Program 35
-------
LIST OF TABLES
Table Page
3-1 Engine Adjustment Survey for the San Bernardino Area. . . 10
3-2 Comparison of San Bernardino & Detroit Emission &
Engine Adjustment Distributions 11
3-3 Vehicle Population Weighted Emission Response
Coefficients 16
3-4 Summary of Deterioration Rates (Change Per Mile)
Pre 1966 Vehicles 20
3-5 Summary of Deterioration Rates (Change Per Mile)
1966-1970 Emission Controlled Vehicles 21
3-6 Summary of Deterioration Rates (Change Per Mile)
Post 1970 NO Controlled Vehicles 22
X
3-7 Failure Rates of Engine Components
Pre-1966 Vehicles 23
3-8 Failure Rates of Engine Components
1966-1970 Emission Controlled Vehicles 24
3-9 Failure Rates of Engine Components
Post 1970 NOV Controlled Vehicles 25
X
3-10 Malfunctions Detected and Corrected 28
4-1 Inspection and Maintenance Procedures Studied 31
4-2 Comparison of Optimal Results for Basic
Inspection/Maintenance Procedures 32
4-3 Comparison of Evaluated Programs 37
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KO INTRODUCTION
This is the final report of the Study of Mandatory Engine Maintenance
for Reducing Vehicle Emissions. The overall objective of this program was
to examine the feasibility of using mandatory vehicle inspection and mainte-
nance as a means for controlling automobile exhaust emission levels. Both
the achievable exhaust emission reductions and total program cost were used
in the feasibility assessment. Particular program objectives were the
following:
• Develop an empirically based computer model capable of
evaluating a broad spectrum of vehicle inspection and
maintenance procedures for reducing exhaust emissions.
• Employ the computer model to evaluate selected vehicle
inspection and maintenance options.
• Maintain the computer model in a state of readiness to assist
regional planners in evaluating vehicle inspection and mainte-
nance programs as part of their plan to achieve ambient air
quality goals.
An important aspect of this program was the effort made to base emission
predictions upon firm experimental data. The program therefore involved
designing and executing a series of experiments to acquire data to support
an analytical model capable of evaluating many different inspection and
maintenance procedures. The experiments thus were not field tests of parti-
cular inspection and maintenance procedures but were designed to characterize
effects common to a wide variety of these procedures. The supporting experi-
mental program consisted of the following activities:
• A survey to establish the frequency and extent of engine mal-
adjustments and malfunctions in user vehicle populations.
• Experiments to establish the influence of selected engine
adjustments and states of component degradation upon vehicle
exhaust mass emission rates.
• Experiments to estimate the rates with which engine adjustments
and exhaust emissions deteriorate with vehicle use.
t A survey to establish the effectiveness with which garages
diagnose and repair those engine malfunctions and maladjust-
ments found to be important in an inspection and maintenance
program.
1
-------
The results of these experiments are summarized in Section 3.0 of this docu-
ment and are presented in detail in separate volumes of this report.
Final modifications were made to the economic effectiveness model.
Specifically the model was broadened to evaluate the following two new
strategies:
o Inspections in which the vehicle rejection criteria are
adjusted with program duration so that a constant fraction
of the vehicle population is sent to mandatory maintenance.
o Programs in which the inspection step is omitted but which
involve various degrees of mandatory maintenance for the
entire vehicle population.
The upgraded model was used with the entire background of experimental data
to optimize and reevaluate selected inspection and maintenance strategies.
The principle change in the data base used to support this final evaluation
of procedures was to include the results of the engine adjustment and exhaust
emission deterioration tests. Results of this final evaluation are summarized
in Section 4.0 of this report.
Final program conclusions presented in the following section tend to
support those given in the Year End Report of July 1972. Hydrocarbon and
carbon monoxide emission reductions ranging from five to ten percent are
predicted for inspection and maintenance programs which have been optimized
for their cost effectiveness. It is emphasized that the emission reductions
reported in this study are not those which can be achieved by perfectly
maintaining a selected fraction of a current vehicle population on a one-
time basis. Rather these estimated emission reductions reflect:
o Inspection errors of omission and commission
o Imperfect maintenance
o Maintenance limited to specified components and subsystems
o A growing vehicle population in which the number of newer
cars is increasing and older cars are decreasing
Further, the emission reductions reported are either the reductions aver-
aged over five years of program operation or those obtained at the end of
the fifth program year.
-------
An annotated bibliography of all the major reports prepared during
this program is presented in Section 5.0 for the convenience of readers
wishing to pursue this subject in greater depth.
-------
2.0 GENERAL STUDY CONCLUSIONS
The conclusions derived from this study reflect the final experimental
data and latest version of the economic effectiveness model. This analysis
differs from the previous one (Year End Report - July 1972) in the follow-
ing regards:
o The final data from the experimental study of engine adjust-
ment and exhaust emission deterioration was used throughout
the analysis.
o The economic effectiveness model was revised to reflect the
latest experimental data and forecasting methodologies.
o A wider range of inspection and maintenance alternatives were
examined.
A summary of the final study is presented by major areas of investi-
gation.
2.1 EXPERIMENTAL PROGRAM
A number of conclusions were drawn directly from the experimental
program results:
t The diagnostic content of emission modes are as follows:
- CO and HC emissions in loaded engine operating modes are
influenced by induction components that affect fuel-to-
air ratio.
- Advanced timing Increases NOX emissions under loaded engine
modes and increases HC emissions at idle.
- Idle HC emission measurements are weakly affected by idle
RPM.
- Idle HC and CO emissions are affected by the idle fuel to
air ratio.
- Engine malfunctions are more readily identified by the
exhaust emissions of newer cars because their normal emission
levels are lower.
• Significant emission increases were observed during the deter-
ioration tests, but these changes could not be systematically
related to corresponding changes in engine settings.
-------
• "Cold start" emissions data are highly variable compared to
the hot engine results and show that the older pre-control
vehicles are more sensitive to choke malfunctions than are
the NO controlled vehicles.
X
• The performance of service organizations in correcting emission
related malfunctions and maladjustments was marginal at best,
even when attention was drawn to specific maladjustments.
• Unnecessary repairs can be expected to occur. The absolute
magnitude of the costs incurred is uncertain based on the
data available from this program, but can run from 10-30%
of the repair bill.
2.2 INSPECTION AND MAINTENANCE PROCEDURES
The results from evaluating the three different types of programs
are discussed below. The criteria used to evaluate the relative merit of
each of these programs was a system figure of merit defined as the total
discounted program costs per weighted ton of emission reductions. Emis-
sion weighting factors of 0.6, 0.1 and 0.3 were applied for HC, CO and NO ,
1\
respectively.
1) The results obtained using the latest experimental data and
reconfigured economic effectiveness mode! indicated degradation
in program performance when contrasted with the year end report
results. This can be attributed primarily to the lower rate of
misfire detected in the vehicle population.
2) A hybrid program involving an idle emission inspection and mainte-
nance program as well as the mandatory replacement of air cleaners
and PCV valve, emerged as the most cost effective procedure for
regions with a CO problem.
3) A mandatory maintenance program does not appear very cost effec-
tive, particularly in view of the relatively low repair effective-
ness of maintenance organizations.
4) The largest emission reductions were obtained with a direct
engine inspection followed by an extensive "B" maintenance treat-
ment. This program is eight times more costly than the most cost
effective procedure; however, the emission reductions achieved
are nearly twice as large.
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5) A loaded mode emission inspection followed by the repair of the
idle and ignition systems emerged as the most cost effective
procedure for regions having photochemical smog.
6) Emission inspections performed in state lanes are more cost
effective than inspections performed in licensed or franchised
garages.
7) The most cost effective parameters to maintain are:
a) idle CO, b) timing, c) ignition misfire, d) PCV valve,
e) air cleaner.
2.3 SYSTEM SENSITIVITY ANALYSIS
Sensitivity analyses were performed to measure the influence of data
uncertainties and model assumptions on the effectiveness of various inspec-
tion and maintenance procedures. The candidate procedures were found to be
most sensitive to the following factors which are presented in order of
their importance:
1) Regional Air Pollution - The uniqueness of regional air pollution
problems requires the development of a region specific program.
The characteristics of a given air quality problem, as character-
ized by the emission weighting factor, significantly alter the
relative merit of candidate procedures.
2) Unauthorized Maintenance - During the deterioration experiment^
a large percent of the vehicle owners had their cars maintained
even when specifically requested not to do so. These data suggest
that owners may take deliberate actions to improve their vehicle
performance and driveability at the expense of increased emissions.
Certainly the cooperation of the service industry will be required
if vehicle readjustments which undermine the effectiveness of man-
datory vehicle inspection and maintenance are to be minimized.
3) Service Organization Repair Effectiveness - The effectiveness with
which repair is made by a service organization has a major impact
on resultant emission reductions. For example, if repair relia-
bility were improved, larger HC and particularly larger CO emis-
sion reductions could be achieved.
4) Emission and Engine Deterioration - Engine deterioration and
resultant emission deterioration can have a substantial effect
on procedure effectiveness. Higher rates of deterioration tend
to improve the effectiveness of all procedures in general and the
more extensive procedures in particular.
-------
5) Vehicle Population Characteristics - The analysis has revealed
that shifts in the makeup of the vehicle population, i.e., the
replacement of old cars with newer cars, will have a significant
influence on the cost-effectiveness of the various procedures.
As a result, it is concluded that precontrolled vehicles (espe-
cially for the State of California) are not an important factor
in the long term selection of inspection and maintenance proce-
dures.
6) Extent of Voluntary Maintenance - The extent of voluntary mainte-
nance, as it is currently modeled, has its largest impact on CO.
Obviously, as vehicles are better maintained voluntarily, the
less the need for a mandatory program.
7) Frequency of Inspection and Repair - The frequency of inspection
and maintenance affects program performance. Our studies have
continuously shown that a yearly program is most cost effective.
8) Costs of Unnecessary Repair - The cost of unnecessary repair
accounts tor a major segment of overall program cost. In general,
these costs increase disproportionally with the extent of repair.
Consequently, they introduce an additional bias in favor of idle
oriented programs
9) Inspection Accuracy - Variability in inspection accuracy can have
an important impact on the effectiveness of various inspection
and maintenance alternatives. This is especially the case for
programs with low rejection rates or with complicated diagnostic
procedures.
2.4 REGIONAL IMPLICATIONS OF VEHICLE INSPECTION AND MAINTENANCE
As presented in the year end report, two hypothetical regions were
modeled having different air quality problems and vehicle characteristics.
The economic-effectiveness of mandatory inspection and maintenance is most
influenced by the emission weighting factors assigned in various regions.
Weighting factors which stress CO emission reduction generally result in
a program that does little to control HC and NO emissions. However, large
absolute reductions of CO occur, thereby resulting in extremely good fig-
ures of merit. Those procedures which involve adjusting the idle fueT-to-
air ratio to specification are most effective for controlling CO emissions.
CO emission reductions can be approximately doubled by maintaining compo-
nents of the induction system, but at four times the cost. Even larger
improvements can be achieved if induction system maintenance effectiveness
is improved.
-------
3.0 EXPERIMENTAL PROGRAM
The experimental program involved four major activities:
o A survey of 486 privately owned vehicles in the Los Angeles
and Detroit areas to establish the frequency and extent of
malfunctions and maladjustments in user vehicles.
o Tests of representative power trains in three classes of
vehicles to relate engine adjustments to exhaust emission
levels.
o A periodic test of 450 vehicles in the Los Angeles area to
measure the rates with which engine adjustments and exhaust
emissions deteriorate with vehicle use.
o An experiment to evaluate the effectiveness with which garages
maintain those engine adjustments and malfunctions which were
shown to be critical to exhaust emission levels.
The nature of each of these experiments and the results obtained are
summarized in this section.
3.1 SAN BERNARDINO AND DETROIT SURVEYS OF ENGINE ADJUSTMENTS
Basic to modeling inspection processes and predicting the effect of
maintenance are data which describe how frequently certain key engine adjust-
ments are out of specification and the extent to which these adjustments
deviate from specification. A survey therefore was conducted in the San
Bernardino and Detroit areas to obtain this information. These two areas
were chosen as representative of warm and cold regions of the U.S. and were
compared to determine if climate significantly affected owner maintenance
habits.
Vehicle fleets were acquired in both cities such that the distribution
of vehicles matched the national in-use vehicle distribution by make and
model. Data were desired for three basic vehicle populations; vehicles
without exhaust emission controls .(pre-1966), vehicles with HC and CO
control (1966-1970), vehicles with HC, CO and NO control (post 1970 Calif-
A
ornia vehicles). A total of 486 vehicles were tested.
-------
Table 3-1 presents a summary of the results of this test program for
the San Bernardino area. As shown, the adjustments most frequently out of
specification were ignition timing (basic and vacuum advance), point dwell,
idle speed, idle fuel to air ratio and carburetor float level. Excessively
clogged air cleaners and other failures of the induction system at medium
engine loads which led to high CO emissions also were found frequently.
Vehicle maintenance states were contrasted between Detroit and San
Bernardino for similar vehicle fleets sorted by emission control type. The
results of this analysis, estimates of the mean (X"), standard deviation (S)
and degrees of freedom (d.f.), are presented in Table 3-2. A statistical
comparison of the exhaust emissions and engine adjustments for the two
regions studied indicated a few population differences which were statis-
tically significant at the 90% confidence level. The carbon monoxide emis-
sion levels measured in the high cruise and idle modes are higher in San
Bernardino vehicle fleets than in Detroit. The lower exhaust emissions
measured in Detroit may be the result of a number of factors including more
advanced emission control equipment, lower average accumulated vehicle mile-
age and basic maintenance differences. The lower frequency and level of
misfire in Detroit cars substantially explains the lower HC emissions; how-
ever, the induction related malfunctions affecting CO are not substantially
different for the two regions.
To determine whether or not mileage and model year effects were causing
the differences observed in the exhaust emissions and engine adjustment
states, data from the vehicle fleet in Detroit were partitioned by model year
rather than emission control type. These comparisons showed that only CO
keymode emissions for the 1960-65 vehicles were significantly different.
The Detroit vehicles tended again to have Tower CO emissions. The mileage
accumulation of the Detroit fleet vehicles, however, was still markedly less
than that of the San Bernardino vehicles.
In comparing the 1966-1970 emission controlled vehicle fleets of the
two cities for which the average accumulated mileage was similar, no statis-
tically significant differences in the emission levels were found. Signi-
ficant differences in idle RPM, PCV valve flowrate (49/45 mph Cruise) and
the choke kick adjustments were observed. These deviations are in the
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TABLE 3-1
ENGINE ADJUSTMENT SURVEY FOR THE SAN BERNARDINO AREA
%
Parameter
Satisfactory
Basic Timing 23.8
Total Advance 65.2
Mech. Advance 70.5
Vacuum Advance 67.0
Plug Required Voltage 93.8
Coil Available Voltage 86.7
Point Dwell 58.6
30 mph Cruise, % CO 82.0
Plug Required Voltage 92.1
Misfire Rate 97.3
45 mph Cruise, % CO 81.0
Plug Required Voltage 88.9
Misfire Rate 95.6
60 mph Cruise, WOT
Plug Required Voltage 86.3
Misfire Rate 90.3
Idle Speed 29.5
Idle CO 44.1
Manifold Vac., in. Hg 80.9
Air Cleaner Restriction 77.1
Float Level 65.6
Heatriser Valve 78.2
PCV Performance 88.1
Air Pump Performance 90.4
Vacuum Leaks 97.7
%
Unsatisfactory
76.2
34.8
29.5
33.0
6.2
13.3
41.4
18.0
7.9
2.7
19.0
11.1
4.4
13.7
9.7
70,5
55.9
19.1
22.9
34.4
21.8
11.9
10.6
2.3
Cars
Reported
227
227
227
227
226
226
227
127
227
225
127
226
225
227
227
227
227
225
227
221
225
227
50
224
Rejection
Criteria
Deviation
From Spec.
> ±2 degrees
> ±2 degrees
> ±2 degrees
2 kvolts
< 2 kvolts
z 1 degrees
>2.5% CO
>2 kvolts
>0%
>2.0% CO
>2 kvolts
>m>
>2 kvolts
>0%
> ±30 rpm
>3.5% CO
$ 2 in. Hg
In red zone
of AC
> ±0.06 in.
Frozen
<0 in H20
< 0.2% CO*
**
* Change in CO upon disconnecting the air pump
** Disconnected or leaking vacuum hoses
10
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TABLE 3-2
COMPARISON OF SAN BERNARDINO & DETROIT EMISSION & ENGINE ADJUSTMENT DISTRIBUTIONS
1972 FEDERAL COLD START EMISSIONS
HC, GR/MILE
CO, GR/MILE
NOX, GR/MILE.
LOADED MODE EMISSIONS (49/45 MPH)
HC, PPM
CO, VOLUME %
NOX, PPM
IDLE MODE EMISSIONS'
HC, PPM
CO, VOLUME %
NOX, PPM
TIMING DEVIATION, DEGREES
IDLE SPEED DEVIATION, RMP
AIR CLEANER BLOCKAGE ANGLE, DEGREES
PCV VALVE FLOW RATE, CFM
CHOKE KICK DEVIATION, INCHES
HEAT RISER VALVE FAILURES,' PERCENT
VACUUM DIAPHRAM FAILURES, PERCENT
MISFIRE UNDER LOAD (49/45 MPH1, PERCENT
MISFIRE UNDER LOAD (30/33 .MPHI, PERCENT
MISFIRE AT IDLE, PERCENT
AIR PUMP FAILURES, PERCENT
NOX CONTROL DEVICE FAILURES, PERCENT
VEHICLE MILEAGE, MILES
PRE-EM1SSION CONTROLLED VEHICLES
SAN BERNARDINO
(1940-1965)
X 5 ' D.F.
12.00 7.0 147
'131.5 63 147
3.97 2.0 ]47
383 450 1 47
3.43 2.6 147
1666 864 147
865 989 1 46
6.08 3.0 147
126.8 122 147
0.35 5.7 148
77.9 137 148
60.0 53 137
2.87- 1.3 126
9.24xlQ"3 4.88xlO-2 79
53.1 - 80
25.0 - 27
12.3 11.3 6
14.4 9.6 6
17.5 12.0 6
.
-
83358 26047 1 48
DETROIT
(1940-1967,
X S D.F.
_
_
.
332 374 129
1.64 1.5 129
-
603 582 128
4.50 3.1 129
-
0.62 6.0 123
108.5 146 129
61.7 45 113
2.86 1.3 87
-.0511 "0.0654 97
68.0 - 77
32.6 - 42
14.5 1.8 4
15.1 1.7 4
13.9 3.8 4
.
-
58280 19377 129
T
-
-
-
1.02
7.13*
-
2.64*
4.41*
-
-0.38
-1.81
-0.27
0.05
6.85*
-
-
-0.51
-0.18
0.74
-
-
-
EMISSION CONTROLLED VEHICLES
SAN BERNARDINO
(1966-1970)
X S D.F.
7.25 5.7 149
86.9 46 149
6.33 2.6 149
222 306 148
1.22 1.3 149
2613 976 149
376 546 1 48
4.09 2.6 149
124.2 82 149
0.50 4.6 149
-18.2 108 '49
45.6 53 137
2.62 0.97 138
-4.42x10-3 4.6xlO-2 122
44.0 - 74
21.7 - 91
2.6 0.4 2
4.6 3.6 2
11.5 9.7 2
8.1 - 37
-
43786 20567 1 48
DETROIT
(1968-1971)
X S D.F.
.
.
-
198 107 128
0.69 0.81 128
-
300 230 128
3.15 2.5 128
-
1.07 3.7 124
2.5 90 126
47 44 117
2.85 1.2 118
-.0372 0.0643 98
42.5 - 65
21.3 - 79
4.7 0.4 1
4.8 2.4 1
4.2 0.9 1
-
-
27863 .17340 128
T
-
-
-
0.84
4.03*
-
1.55
3.08*
-
-1.11
-1.72
-0.23
-1.71
4.43*
-
-
-5.75
-0.07
1.30
-
-
-
NOX CONTROLLED VEHICLES
SAN BERNARDINO
(1971)
X S D.F.
4.44 1.8 149
63.4 37 149
5.95 2.0 U9
135 56 149
0.87 1.16 149
2537 740 149
240 199 149
3.34 2.7 149
168 96 149
0.17 3.4 147
-5.68 138 149
28.8 43 130
2.58 0.90 135
-9.56nlO~3 4.06xlO'2 126
3.4 - 29
0.0 - 123
-
-
-
-
4.9 - 81
8059 6451 149
ESTIMATES'OF MEANS SIGNIFICANTLY DIFFERENT (CONFIDENCE EQUAL TO OR GREATER THAN 90%)
-------
direction which would explain the somewhat high CO emissions in the San
Bernardino fleet.
With 1971 vehicles, the HC measurements made during the 49/45 mph
cruise and the CO measurements taken at idle were found to be significantly
different in the two regions. The choke kick adjustments for the fleets
also were found to be significantly different in the two regions.
In general, the data indicate reasonable agreement in the distribution
of engine adjustments for the vehicles of the two cities. Some of the
adjustments such as idle RPM which were set higher in Detroit seem reason-
able because of the colder climate. It was surprising, however, that there
were equally large numbers of heat riser valve failures in the Detroit and
San Bernardino fleets.
Diagnostic Content of Exhaust Emissions Measured in Selected Modes
Previous tests had revealed the difficulty of detecting specific engine
malfunctions from emission measurements. It was shown that emissions
measured in intermediate cruise modes add little information useful in
identifying malfunctions to that obtained from measurements made in idle
and high cruise modes. Further it was found to be ineffective to combine
more than two emission mode measurements to identify malfunctions. None-
theless, experimental data from the San Bernardino and Detroit fleet tests
were reexamined to estimate the probability of malfunction diagnosis using
exhaust emission measurements. Seventy-two case studies were performed
using various "cutpoints" as trial limits to detect engine adjustments which
cause high emissions. Detection (failure isolation) probabilities were
generally low. Only the following exceeded 10%:
• idle mode HC as an indication of timing error
• cruise mode HC or CO as an indication of air cleaner restriction
• idle mode HC as an indication of idle rpm error
The use of emission measurements to screen a vehicle population for
those having a feigner probability of maladjustments and malfunctions is a
-------
more promising approach than the use of emission measurements for failure
isolation. Figure 3-1 shows that deviate engine conditions are revealed
fairly consistently although ambiguously by mode emission tests. To construct
this figure the percent of cars failing the pass/fail criteria for each
emission mode was determined as the pass/fail criteria was varied. These
cars constituted the rejected population indicated on the horizontal axis
as a percent of the total population. Cars in the rejected population next
were analyzed to determine if they were out of specification by at least
the amount indicated for each adjustment. The failed population is those
cars from the rejected population found to have the malfunction or maladjust-
ment indicated. Thus, for example, if an idle hydrocarbon inspection cri-
teria is imposed which rejects 20 percent of the total vehicle population,
then 40 percent of the vehicles in the rejected population would be found
to have a timing adjustment which is greater than 1.5 degrees advanced
from specification. Because only slightly more than 36 percent of the vehicles
in the total population have this maladjustment, the emission inspection has
been of some benefit although both the omission and commission inspection
errors are high.
It is evident from looking at the panels for each of the four maladjust-
ments and malfunctions that the failed fraction in the rejected population
is in most cases greater than the failed fraction in the total population.
The emission mode inspection, thus, is beneficial as a screening tool but is
not specific in diagnosing the cause of failure. This subject is discussed
and further data are presented in Volume IV.
3.2 EXPERIMENT TO ESTABLISH THE RELATIONSHIP BETWEEN ENGINE ADJUSTMENTS
AND EXHAUST EMISSIONS
These tests were performed to establish quantitative relationships
between the state of engine adjustments and vehicle exhaust emissions.
These data are required to predict both the effect of engine component
deterioration with vehicle use upon exhaust emissions and to predict the
emission changes resulting from maintenance.
Again three classes of vehicles were characterized; vehicles without
exhaust emissions control (pre-1966), vehicles with HC and CO control
13
-------
FIGURE 3-1
COMPARISON OF SAN BERNARDINO & DETROIT
EMISSION & ENGINE ADJUSTMENT DISTRIBUTIONS
1966-1970 MODEL YEAR AUTOMOBILES
WITH EXHAUST EMISSION CONTROLS
IDLERPM TIMING
4—
o
Jj
-1
^
2
Q
LU
f—
at
u_
o
as
z
0
t—
u_
<
4U
38
36
34
32
30
28
26
24
22
20
1Q
EMISSION CONTROLLED VEHICLE
/IDLE HC
s**^/
/x
/ \
• \
\
FAILED FRACTION OF TOTAL SET
FOR TIMING
»80 RPM ABOVE SPECIFICATION
/
0 1& 20 3D 40 50
REJECTED FRACTION, °A OF TOTAL POPULATION
o
6
z
Q
I—
u
$
EMISSION CONTROLLED VEHICLES
7.
FAILED FRACTION OF TOTAL SET
FOR TIMING SI.5 DEGREES
ADVANCED OF SPECIFICATION
0 10 20 30 40 50
REJECTED FRACTION, % OF TOTAL POPULATION
PCV FLOW
AIR CLEANER
EMISSION CONTROLLED VEHICLES
49/45 MPH HC OR .
49/45 MPH CO
FAILED FRACTION OF TOTAL SET
FOR AIR CLIM : 100 DEGKES
0 10 20 30 40 50
REJECTED FRACTION, ';, OF TOTAL POPULATION
u. 10
Z
e 6
t—
\j
2 4
EMISSION CONTROLLED VEHICLES
49/45 MPH HC OR 49/45 MPH CO
/ FAI
/ FOI
IDLE CO
FAILE& FRACT [ON OF TOTAL SET
FOR PCV FLOW I1.5CFM
10 20 30 40 50
REJECTED FRACTION, % OFTOTAL POPULATION
14
-------
(1966-1970), and vehicles with HC, CO and NO control (1971). The tests
X
involved from 8 to 11 vehicles in each of these classes in order to study
the basic engine families of each major manufacturer. Repeat tests were
run on two different engines of a single engine family and the engine emis-
sion influence coefficients were shown to be very similar, thus, validating
the experimental approach.
The tests involved a systematic variation of those engine adjustments
which were found for each vehicle class to have a pronounced effect upon
emissions. These included basic ignition timing, idle speed, idle fuel-to-
air ratio, PCV restriction and air cleaner restriction as well as NO
A
control devices and air pumps on cars with this equipment. Experiments
were designed to accommodate a fractional factorial analysis of variance.
A 1/2 replicate of the total possible number of combinations of test var-
iables was used in order to limit the test cost while obtaining statis-
tically meaningful data.
The test sequence for each vehicle began with a complete checkout of
the engine and transmission for nominal operating conditions against manu-
facturer's specifications (not minimum emissions) including replacement as
necessary of ignition, induction and emission control components. Emission
measurements were made using the 1972 Federal Test Procedure, closed 7-mode
procedure, the Federal Short Cycle and the Clayton Keymode Cycle under hot
engine conditions. Choke effects were measured using the 1972 Federal Test
Procedure under cold start conditions. Following baseline emission measure-
ments, the programmed adjustment deviations and/or malfunctions were intro-
duced and the exhaust emission tests were repeated.
These statistically designed experiments relate engine adjustments to
exhaust emissions measured on both a mass and concentration basis. The
population weighted emission responses are summarized in Table 3-3. Emis-
sion response to engine adjustments also was investigated for two constant
speed operating modes. It is significant to note that with few exceptions,
engine malfunctions and maladjustments influence emission modes similarly
for all three classes of vehicles studied. Thus, it is reasonable to anti-
cipate that the same emission inspection procedures will be applicable to
15
-------
TABLE 3-3
VEHICLE POPULATION WEIGHTED
EMISSION RESPONSE COEFFICIENTS
1
Timing Advance
Idle Speed
jldle Fuel to
'Air Ratio
i
Air Cleaner
Restriction
PCV Restriction
Pre 1966
Vehicles
HC
.067
-.0029
.44
.0057
.023
CO
-.84
.029
4.08
.112
-2.44
NOX
.14
.00073
.22
-.0030
.058
1966-1970
Vehicles
HC
.050
-.0055
.029
.0009C
-.084
CO
-.34
.021
7.12
.076
-2.86
NOX
.095
.00026
.029
-.0021
.087
1971
Vehicles
HC
.076
-.0004
.080
.00089
-.155
CO
-1.02
.026
6.77
.069
-7.46
NOX
.13
.00096
-.029
-.0024
.104
Response
Units*
gm/mile, deg
gm/mile, rpm
gm/mile, % CO
gm/mile, degree**
gm/mile, cfm
* Mass emissions measured using 1972 Federal Test Procedures with engine hot start
** Degrees of air cleaner blocking measured with an AC tester
-------
all groups. Of course, because of the substantially lower exhaust emissions
of 1971 vehicles, the pass/fail criteria must be set lower for these vehi-
cles.
Engine malfunctions affecting cold start emissions were also investi-
gated. Three vacuum kick settings (normal +_ 50%) and two heat riser settings
(normal, stuck open) were tested. The results were inconclusive, because
of large variability in the data. Although emission changes were large,
only about 10% of the tests were statistically significant at the 90%
confidence level.
3.3 ENGINE ADJUSTMENT AND EXHAUST EMISSIONS DETERIORATION EXPERIMENT
The objective of the deterioration experiment was to determine the
rate of variation (change per mile of vehicle use) of exhaust emissions and
continuous engine tune adjustments as well as to determine the failure rates
of those engine components which are either operative or inoperative. Three
groups of 150 privately owned vehicles were acquired for these tests con-
sisting of pre-1966 automobiles which were not exhaust emission controlled,
1966-1970 vehicles Which had hydrocarbon and carbon monoxide controls and
1971 vehicles which were also NO controlled. The vehicle mix within each
X
fleet was typical of the national vehicle population.
In this experiment both exhaust emissions and engine adjustments of
each vehicle were measured at approximately four-month intervals. The
vehicles were first subjected to comprehensive inspection and repair. The
following items were checked: spark plugs, coil, points, dwell, condenser,
timing, spark advance (total, mechanical and vacuum), idle RPM, idle fuel
to air ratio, manifold vacuum, air cleaner, float level, choke vacuum kick,
NO control device, PCV valve and air pump. Critical components were tested
/\
and emission measurements made. Parts were replaced as necessary and the
engine tuned to manufacturer's specifications. Emission measurements were
repeated after this initial maintenance to provide a baseline for the deter-
ioration experiment. The emission tests included cold start tests using
the 1972 Federal Test Procedure as well as hot start emission tests performed
under idle as well as loaded engine operating modes. Constant volume sample
(CVS) emission measurements and direct concentration measurements were made.
17
-------
The test vehicles were recalled every four months to inspect engine
adjustments and perform exhaust emission tests. Following four periods of
deterioration (16 months), the vehicles were inspected a final time, emission
tested, returned to manufacturers' specifications, and emission tested again.
A detailed description of the vehicle acquisition procedures, test procedures,
and data analysis procedures is presented in Volumes IV and VIII of this
report.
It was the intent of the experiment that the test vehicles receive no
maintenance during the experiment unless it became required to keep the
vehicle operable. With a comprehensive tune-up at the beginning of testing
it was expected that a large percentage of the vehicles would complete the
program without further maintenance. The vehicle owners were informed of
the purpose of the experiment and were asked to have no tune-up work done.
If repair work were done on an emergency basis, it was to be reported.
Minor adjustments would be made by Scott based upon legitimate need.
It became apparent early in the program that the test vehicles were
being maintained without authorization. As a consequence, part numbers
were recorded and replacement parts marked to detect unauthorized adjust-
ments. At the end of the test program there were only 24, 27 and 29 vehicles
respectively in the three test fleets that had received no known maintenance.
There were 43, 38 and 43 vehicles respectively which had received only minor
adjustments. Another 20 to 30 percent of the vehicles in each fleet had
received major maintenance and finally approximately 30 percent of each
fleet was lost to the program for a variety of other reasons. Of the veh-
icles in the three fleets which received minor adjustments, 49%, 32% and 19%
respectively of these repairs were not reported. The number of unreported
cases of vehicle maintenance was determined by examining parts for their
numbers or markings. Examination of exhaust emissions and engine adjust-
ments suggested many additional cases of maintenance.
An important conclusion of this test program is that adequate program
control of maintenance cannot be achieved over prolonged test periods using
vehicles from the general public. Owner deviation from the instructions
provided can be explained because (1) they were unaware that adjustments
1.8
-------
were being made, (2) they were unaware of the type and extent of maintenance
that they had requested or (3) they were unwilling to report repairs even
though specific inquiries were made. Probably all three cases occurred.
Review of the data developed over a sixteen month test period indicated
that statistically significant deterioration rates were obtained for exhaust
emissions using the 1972 Federal emission test procedures. By contrast
very few statistically significant rates were found for key mode exhaust
concentrations or for engine adjustments. At least part of the difficulty
in establishing statistically significant relationships resulted from the
very limited number of vehicles which accumulated higher mileage without
maintenance.
Engine Adjustment Deterioration Rates
Several methods were employed to develop estimates of deterioration
rates. A summary of the deterioration rates that are considered to be the
best estimates is presented in Tables 3-4, 3-5 and 3-6 respectively for
the Pre-emission, Emission, and NO Controlled Vehicles. Mean values as
/\
well as the upper and lower 95 percent confidence limits are presented.
Review of the test data indicated that statistically significant deteriora-
tion rates were consistently obtained for cold-start 1972 Federal emis-
sions and air cleaner restrictions. There were only three additional cases
in which statistically significant results were obtained. These were HC
emissions during 49/45 mph cruise and PCV flow rates for emission controlled
vehicles and NO emissions during 49/45 mph cruise for NO controlled veh-
X X
ides. It was concluded that the most meaningful result of this experi-
ment was the definition of upper and lower limits of the rates at which
exhaust emission and engine adjustments can be expected to deteriorate.
Engine Component Failure Rates
In addition to the deterioration rates of engine adjustments, the data
taken in the deterioration experiment were analyzed to develop the failure
rates of components which are either operative or failed. Summaries of
the parameter failure rates" of interest are respectively presented in
Tables 3-7, 3-8 and 3-9 for the three test fleets. p
19
Met®r Vehicle Emission
-------
TABLE 3-4
SUMMARY OF DETERIORATION RATES (CHANGE PER MILE)
PRE 1966 VEHICLES
FLEET 1
PARAMETER
COLD 1972 FEDERAL HC, gm/mi^
COLD 1972 FEDERAL CO, gm/m1 %
COLD 1972 FEDERAL NO. gm/mi
A
49/45 MPH CRUISE HC, ppm/mi
49/45 MPH CRUISE CO, % v/mi
49/45 MPH CRUISE NO , ppm/mi
A
IDLE HC, ppm/mi
IDLE CO, % v/mi
IDLE NO. ppm/mi
A
TIMING, degrees/mi
IDLE RPM, rpm/mi
AIR CLEANER, degree/mi
PCV FLOW (33/30 MPH CRUISE), cfm/mi
UPPER LIMIT
T + kS
9.332x10"!
7.569x10";?
-1.230x10"*
3.176x10";?
4.725x10"]?
6.053x10"^
3.174x10"?
3.202x10".;
-1.561xlO"d
1.131x10"?
10.715x10":;
7.729x10"^
3.513xlO"5
MEAN
X"
5.740x10"!*
4.673x10";*
-2. 327x1 O"4*
-0.978x10"^
-1.610x10";
2.306x10"^
-0.382x10"?
1.334x10",
-3.140x10"^
-1.481x10"!
3.766x10,
5.307-xlO"J
-1.424xlO"D
LOWER LIMIT
X" - kS
2.1 48x1 0"!j
1.477xlO"f
-3.354x10"^
-5.132x10"^
-7.945x10",
-1.441x10"*
-3.938x10"^
-0.534x10"^
-7.841X10"-3
-4.093x10"!
-3.183x10":?
2.885x10"^
-6.361X-10"5
* Statistically significant at the 90% confidence level
-------
TABLE 3-5
SUMMARY OF DETERIORATION RATES (CHANGE PER MILE)
1966-1970
EMISSION CONTROLLED VEHICLES
FLEET 2
PARAMETER
0
COLD 1972 FEDERAL HC, gm/m^
COLD 1972 FEDERAL CO, gm/irn ,
COLD 1972 FEDERAL NO , gm/nvT
/\
49/45 MPH CRUISE HC , ppm/mi
49/45 MPH CRUISE CO, % v/mi
49/45 MPH CRUISE NOV, ppm/mi
/\
IDLE HC, ppm/mi
IDLE CO, % v/mi
IDLE N0x, ppm/mi
TIMING, degrees/mi
IDLE RPM, rpm/mi
AIR CLEANER, degrees/mi
PCV FLOW (33/30 MPH CRUISE) ,cfm/mi
UPPER LIMIT
X~+ kS
-A.
2.570x10 ,
4.054x10";?
-2.636x10"^
0.334x10"^
2.568x10,
2.137x10"^
0.629x10"^
1.062x10",
2.267xlO"J
1.240x10"^
4.011x10':?
3.426x10"^
-1.946x10"°
MEAN
I
A
1.333x10 1*
2.351x10"^*
-3.744x10"^*
-2.444x10';?*
-0.278x10"°
-1.203x10"^
0. 046x1 0"?
0.274x10".
-1.088xlO"J
-0.409x10"^
0.053x10"^
2.555x10"^*
-4.758x10"°*
LOWER LIMIT
X" - kS
-4
0.096 10 ,
0.648x10"^
-4.852x10"^
-5.222x10"^
-3.124x10";
-4.543x10"^
-0.537xlO"f
-0.514x10"^
-4.443x10"°
-2.058x10"^
-3.905x10"°
1.684x10"°
-7.570x10"°
*Statistically significant at the 90% confidence level.
-------
TABLE 3-6
SUMMARY OF DETERIORATION RATES (CHANGE PER MILE)
POST 1970
NOV CONTROLLED VEHICLES
A
FLEET 3
PARAMETER
COLD 1972 FEDERAL HC, gm/mi~
COLD 1972 FEDERAL CO, gm/nri ?
COLD 1972 FEDERAL NOV, gm/mr
A
49/45 MPH CRUISE HC, ppm/mi
49/45 MPH CRUISE CO, % v/mi
49/45 MPH CRUISE NOV, ppm/mi
A
IDLE HC, ppm/mi
IDLE CO, % v/mi
IDLE NO , ppm/mi
A
TIMING, degrees/mi
IDLE RPM, rpm/mi
AIR CLEANER, degrees/mi
PCV FLOW (33/30 MPH CRUISE), cfm/mi
UPPER LIMIT
1+ kS
1.191x10"!
1. 474x1 0~r
0.653x10"°
"1.598x10"?
0.320x10";
0.271x10"^
0.260x10"?
0.493x10",
2.762X10"13
1.. 117x10"!
0.856x10,
2.711x10"^
2.199x10"°
MEAN
I
0. 703x1 0"o*
O.SlOxlO'c*
-3.381x10"°*
-0.228x10"^
-0.716x10'°,
-3.002x10"^*
-0.013x10"?
-0.115x10"^
0.200xlO"J
0.345x10"^
-1.510x10",
2.093x10"^*
0.970x10"°
LOWER LIMIT
I - kS
0.215x10"!*
0.147x10"^
-7.415x10"°
-2.054x10";?
-1.752x10";
-6.275x10"^
-0.286x10"?
-0.723x10",
-2.362xlO"J
-0.427x10"^
-3.876x10",
1.475xlO"c
-0.259x10"°
PO
ro
* Statistically significant at the 90% confidence level.
-------
TABLE 3-7
FAILURE RATES OF ENGINE COMPONENTS
PRE-1966 VEHICLES
(FLEET 1)
PARAMETER
HEAT RISER VALVE
% FAILED
SAMPLE SIZE
VACUUM DIAPHRAGM
% FAILED
SAMPLE SIZE
NOX CONTROL DEVICE
% FAILED
SAMPLE SIZE
AIR PUMP
% FAILED
SAMPLE SIZE
MISFIRE, 49/45 CRUISE
MEAN PERCENT MISFIRE
MISFIRE POPULATION
SAMPLE SIZE
MISFIRE, 33/30 CRUISE
MEAN PERCENT MISFIRE
MISFIRE POPULATION
SAMPLE SIZE
MISFIRE, IDLE
MEAN PERCENT MISFIRE
MISFIRE POPULATION
SAMPLE SIZE
MILEAGE, MILES
AS
RECEIVED
51.8
85
21.4
28
_
-
. . _
-
.508
5
150
.564
5
150
.737
5
150
0
FOLLOWING
INITIAL
TUNE-UP
7.0
86
0
28
_
-
_
-
0
0
150
0
0
150
0
" 0
150
0
FIRST
RECALL
38.4
73
0
22
_
-
_
-
.638
4
126
.739
4
126
.574
4
126
3600
SECOND
RECALL
49.2
65
0
19
_
-
_
-
.307
2
no
.350
3
no
.354
3
no
6200
THIRD
RECALL
48.3
60
0
19
_
-
_
-
0.133
1
105
0
0
105
0.217
2
104
9100
FOURTH
RECALL
52.7
38
16.7
12
_
-
_
-
0.914
3
81
0.899
3
81
0.545
3
80
11200
FOLLOWING
FINAL
TUNE-UP
5.4
55
10.5
19
-
-
_
-
0
0
97
0
0
97
0
0
97
11200
ro
OJ
Mean of Total Population
-------
TABLE 3-8
FAILURE RATES OF ENGINE COMPONENTS
1966-1970 EMISSION CONTROLLED VEHICLES
(FLEET 2)
PARAMETER
HEAT RISER VALVE
% FAILED
SAMPLE SIZE
VACUUM DIAPHRAGM
% FAILED
SAMPLE SIZE
NOX CONTROL DEVICE
% FAILED
SAMPLE SIZE
AIR PUMP
% FAILED
SAMPLE SIZE
MISFIRE, 49/45 CRUISE
MEAN PERCENT MISFIRE
MISFIRE POPULATION
SAMPLE SIZE
MISFIRE, 33/30 CRUISE
MEAN PERCENT MISFIRE
MISFIRE POPULATION
SAMPLE SIZE
MISFIRE, IDLE
MEAN PERCENT MISFIRE
MISFIRE POPULATION
SAMPLE SIZE
MILEAGE, MILES
AS
RECEIVED
43.8
73
20.6
92
0
12
7.7
39
.0750
2
148
.0818
2
148
.208
2
148
0
FOLLOWING
INITIAL
TUNE-UP
4.1
73
0
92
0
13
2.6
39
0
0
148
0
0
148
0
0
148
0
FIRST
RECALL
25.0
72
2.4
85
0
15
2.8
35
0
0
130
0
0
130
0
0
130
5000
SECOND
RECALL
35.9
64
5.6
72
0
15
3.1
32
0
0
112
0
0
112
.112
1
112
8100
THIRD
RECALL
48.1
52
4.8
63
13.3
15
0
27
.300
2
98
.304
2
98
.247
2
98
11700
FOURTH
RECALL
48.7
35
9.3
43
11.1
9
0
25
0
0
85
0
0
35
0
0
85
14600
FOLLOWING
FINAL
TUNE-UP
0
53
6.6
61
8.3
12
0
25
0
0
95
0
0
95
0
0
95
14600
ro
Mean of Total Population
-------
TABLE 3-9
FAILURE RATES OF ENGINE COMPONENTS
POST 1970
NOY CONTROLLED VEHICLES
x (FLEET 3)
i : • :
PARAMETER
HEAT RISER VALVE
% FAILED
SAMPLE SIZE
VACUUM DIAPHRAGM
% FAILED
SAMPLE SIZE
NO CONTROL DEVICE
% FAILED
SAMPLE SIZE
AIR PUMP
AS
RECEIVED
3.6
28
0
122
4.8
84
,, FAILED
SAMPLE SIZE I
MISFIRE, 49/45 CRUISE
MEAN PERCENT MISFIRE
MISFIRE POPULATION
SAMPLE SIZE
MISFIRE, 33/30 CRUISE
MEAN PERCENT MISFIRE
MISFIRE POPULATION
SAMPLE SIZE
MISFIRE, IDLE
MEAN PERCENT MISFIRE
MISFIRE POPULATION
MILEAGE, miles
0
0
150
0
0
150
.0993
1
0
FOLLOWING
INITIAL
TUNE-UP
0
28
0
122
2.4
85
-
-
0
0
150
0
0
150
0
0
0
FIRST
RECALL
0
25
1.8
113
6.8
74
-
-
.0544
1
136
.0434
1
136
.0301
1
5700
SECOND
RECALL
4.8
21
4.1
98
4.4
68
-
-
0
0
114
0
0
114
0
0
9600
THIRD
RECALL
0
21
2.1
96
10.4
67
-
-
0
0
111
0
0
111
0
0
13900
FOURTH
RECALL
0
10
1.6
61
13.0
46
-
-
.165
1
86
.173
1
86
.153
1
17400
FOLLOWING
FINAL
TUNE-UP
0
19
2.2
90
14.3
63
-
•*
0
0
106
0
0
106
0
0
17400
IN3
on
Mean of Total Population
-------
It was consistently observed throughout the program that the heat riser
valve has a high frequency of failure. Vacuum diaphragms have comparatively
low rates of failure. NO control devices have a surprisingly large number
X
of failures. The number of vehicles equipped with an air injection reactor
emission control system was small. During initialization, the one vehicle
with a failed air pump was not corrected. This vehicle was the only one
in which an air pump failure was observed. The frequency of misfire was
greatest with the pre 1966 vehicles. Misfire frequency was lower with the
later model vehicles, and overall was less than expected.
3.4 EVALUATION OF GARAGE MAINTENANCE EFFECTIVENESS
Ten vehicles were deliberately malfunctioned or maladjusted and sent
to service agencies for diagnosis and repair. The malfunctions studied
were those identified in earlier experiments as having large effects upon
exhaust emissions. Half of the'vehicles were sent to the service agencies
with instructions to check adjustments, while the others were cited as
having failed emission tests. In the latter case, the probable cause was
identified. No major repairs were allowed. Equal numbers of cars were
sent for maintenance to new car dealers, independent garages and service
stations. Ninety tests were run in Riverside, California, and 150 were
conducted in San Bernardino.
Each test vehicle was given a major tune-up before the experiment began.
Ignition, induction and emission control components were repaired and
adjusted to manufacturer's specifications. Each vehicle then was given
emission tests at idle and under two engine load conditions (Clayton Key-
modes). When it was clear that the engine met the manufacturer's specifi-
cations, the selected malfunctions and maladjustments were deliberately
introduced. The Clayton Keymode tests were re-run to establish the experi-
mental emissions baseline. The car was then delivered to the service agency.
After maintenance, the vehicle was re-inspected and once again subjected
to emission tests using the Clayton Keymodes. In this way, data were
obtained on changes in adjustments and in exhaust emissions resulting from
the maintenance which was performed. All test data were screened for statis-
tical significance before establishing repair effectiveness coefficients
for the Economic Effectiveness Model.
26
-------
The performance effectiveness of all the types of service organizations
tested was marginal to poor for vehicles in both the engine inspection and
emission inspection fleets. A summary of the fraction of malfunctions and
maladjustments corrected by each class of service organization is presented
in Table 3-10. The data were obtained by pooling test results obtained
in the San Bernardino and Riverside areas. This table shows that up to 52%
of the emissions related malfunctions and maladjustments remained uncorrected
following maintenance. Successful maintenance performance ranged from 48 -
68%. These data further suggest that some types of service organizations
may perform better than others with respect to the repair of NO control
A
equipment and the ignition system as well as the adjustment of idle air to
fuel ratio. Table 3-11 shows the range of detection and the range of suc-
cessful repair of engine malfunctions. It indicates that the detection
of a malfunction does not guarantee a successful repair. For example, the
detection rate for an idle fuel-to-air ratio maladjustment ranged from 55%
to 100% while the ability of service organizations to adjust this parameter
to within +1% of manufacturer's specifications ranged from complete failure
to a maximum of 52&. Similar discrepancies between maladjustment detection
and repair can also be seen for idle rpm, timing and choke kick. Detection
and repair percentages were identical for the other malfunctions studied
because the repair generally entailed the replacement of a faulty part
rather than an adjustment to specification.
27
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TABLE 3-10
MALFUNCTIONS DETECTED AND CORRECTED
Independent
Garages
Emission Parameter
Vehicles Vehicles
Total
Malfunctions 133 242
Submitted
Malfunctions
Found and 73 122
Corrected
Malfunctions
Not Corrected 60 120
Percent
Malfunctions 54% 50%
Found and
Corrected
Dealerships Service Stations
Emission Parameter Emission Parameter
Vehicles Vehicles Vehicles Vehicles
134 239 140 243
i
92 120 85 119
42 119 55 124
68% 50% 60% 48%
TABLE 3-11
RANGE OF DETECTION OR REPAIR
FOR ALL VEHICLES UNDER ALL
OR MALFUNCTIONED PARAMETERS
EXPERIMENTAL CONDITIONS
Parameter
Idle CO
Idle RPM
Basic Timing
NO Control Device
/\
Spark Plug Wire Misfire
Spark Plug Misfire
Air Cleaner
PCV Valve
Heat Riser Valve
Choke Kick
Detection, %
55
67
50
12
25
50
67
50
15
27
to
to
to
to
to
to
to
to
to
to
100
100
89
41
100
96
86
90
67
37
Repair, %
0
45
33
12
25
50
67
50
15
15
to
to
to
to
to
to
to
to
to
to
52
73
78
41
100
96
86
90
67
18
Repair Type
Adjustment
"
"
Parts Replacement
Parts Repair or Re-
placement
Parts Replacement
"
»
Parts Repair
Adjustment
28
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4.0 ECONOMIC EFFECTIVENESS STUDY
This section summarizes a study of the economic effectiveness of
mandatory vehicle inspection and maintenance. The primary objectives of
this analysis were:
o To evaluate mandatory vehicle inspection and maintenance as
a means for reducing automobile exhaust emissions.
o To determine the effect of different regional air pollution
problems upon the effectiveness of mandatory vehicle inspection
and maintenance and to identify the more attractive procedures
for different classes of air quality problems.
The main thrust of the analysis was to determine the costs and emission reductions
achieved using a number of candidate procedures. The information presented
herein reflects the latest available experimental data including results
from the deterioration experiments, as well as the most recent refinements
to the economic effectiveness model.
The economic effectiveness model involves both theoretical and empirical
relationships. Theory provides the conceptual framework for describing
inspection and maintenance processes whereas the experimental data yields
the specific transformations needed to define and interconnect the various
model elements.
Development of the model required a detailed specification of the
various relationships characterizing the inspection and maintenance process.
A program of vehicle inspection maintenance can be described in terms of
three basic elements—engineering design, economic analysis and regional
characteristics. Each of these elements describes one fundamental part of
the total process. The economic effectiveness model interrelates these
elements and provides the necessary mathematical algorithms to allow the
design of an inspection and maintenance system having optimum performance'
and cost.
4.1 EVALUATION OF .ALTERNATIVE PROGRAMS
The economic effectiveness model was used to evaluate three basic
inspection ^md maintenance strategies'
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• Mandatory inspection and maintenance
Engine inspection
Exhaust emission inspection
t Mandatory maintenance only
• Hybrid inspection and maintenance procedures which involve
combinations of the two previous strategies
This evaluation provides a good comparison of these strategies and should
be of direct interest to those states and regions that are currently con-
templating a program of inspection and maintenance. The Los Angeles Basin
was selected for this evaluation because: 1) the experimental data used
in the model were developed in the Los Angeles area; 2) the region suffers
from chronic air pollution in the form of photochemical smog to which the
automobile is a significant contributor.
Table 4-1 summarizes the inspection and maintenance alternatives
examined. The idle related adjustments (fuel to air, timing and idle rpm)
involve labor only, are economical to repair and can be selectively mani-
pulated to influence all three exhaust emissions. Ignition related compo-
nents primarily influence HC emissions, although NO emissions are also
*" X
strongly affected by spark timing. The cost of repairing these items is
distributed about evenly between labor and parts. Induction system com-
ponent failures (PCV valve, air cleaner, air pump and choke system) primarily
affect CO emissions and to a lesser degree HC and NO emissions. Repair
/\
costs for these items tend to be largely determined by the cost of replace-
ment parts, although labor costs for atr pump and choke maintenance can be
appreciable.
A sample set of results from the final analysis is given in Table 4-2.
It is emphasized that the emission reductions reported in this study are not
those which can be achieved by perfectly maintaining a selected fraction of
a current vehicle population on a one-time basis. Rather, these estimated
emission reductions reflect:
o Inspection errors of omission and commission
o Imperfect maintenance
30
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TABLE 4-1 INSPECTION AND MAINTENANCE PROCEDURES STUDIED
• Mandatory Inspection and Maintenance
Engine Inspection
1) Idle (Franchised Garage)
2) Extensive A (Franchised
Garage w>th Dynamometer)
3) Extensive B (Franchised
Garage with Dynamometer)
Emission Inspection
1) Idle (State Lane)
2) Extensive A (State Lane
Emission Under Load)
3) Extensive B (State Lane
Emission Under Load)
t Mandatory Maintenance
1) Recommended Manufacturer's
Maintenance
(Franchised Garage)
• Hybrid Inspection and Maintenance
1) Idle Inspection with Mandatory
Replacement
(Franchised Garage)
2) Random Idle Inspection
(State Lane)
Inspection and Maintenance Procedure
Inspect and adjust ICO, idle rpm,
and timing
Inspect and adjust ICO, idle rpm,
timing, repair misfire and NO
control
Inspect and adjust ICO, idle rpm,
timing, repair misfire, air pump,
PCV valve, air cleaner, NO control
and choke system x
Measure ICO, IHC; adjust ICO, idle
rpm and timing
Measure ICO, IHC, LHC; adjust ICO,
idle rpm, timing, repair misfire
and NO control
Measure ICO, IHC, IHC, LCD; adjust
ICO, idle rpm, timing, repair mis-
fire, PCV valve and air cleaner
Undertake specific maintenance
treatment as prescribed by manu-
facturer
Inspect -and adjust ICO, idle rpm,
timing, replace air cleaner and
PCV value
Inspect subset of vehicle popula-
tion using idle emission test and
perform required maintenance
ICO - Idle CO emission measurement
IHC - Idle HC emission measurement
LCO - Loaded CO emission measurement
LHC - Loaded HC emission measurement
31
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TABLE 4-2 COMPARISON OF OPTIMAL RESULTS FOR BASIC
INSPECTION/MAINTENANCE PROCEDURES
IN3
INSPECTION/MAINTENANCE
PROCEDURES
ENGINE PARAMETER INSPECTION
1. IDLE (FRANCHISED)
2. EXTENSIVE A+ (FRANCHISED)
3. EXTENSIVE B++ (FRANCHISED)
EXHAUST EMISSION INSPECTION
4. IDLE (STATE LANE)
5. EXTENSIVE A+ (STATE LANE)
6. EXTENSIVE B++ (STATE LANE)
FIGURE OF MERIT
$/TON+++
ABC
785 320 540
2335 975 1585
2865 1165 1515
575 235 335
1340 558 915
1590 650 945
COST PER
VEHICLE
D E
4.55 5.20
16.85 23.10
32.10 34.95
3.20 4.10
8.90 16.75
11.60 20.70
EMISSION REDUCTIONS, PERCENT
HC
3.3
6.3
7.8
1.7
4.7
4.9
CO
6.1
6.1
10.4
6.8
6.8
7.3
NO
-0.1
-0.1
-1.6
-0.2
-0.2
-0.5
IDLE PLUS IGNITION TUNEUP, WITH DYNAMOMETER A. Computed over five year period.
IDLE PLUS IGNITION PLUS INDUCTION TUNEUP WITH DYNAMOMETER B. Computed at end of last interval.
L.A. BASIN WEIGHTING FUNCTION C. Based on statistically significant
emissions reductions for last interval.
D. Based on total vehicle population.
E. Based on maintained portion of vehicle
population.
-------
o Maintenance limited to specified components and subsystems
o A growing vehicle population in which the number of newer
cars is increasing and older cars are decreasing
Further, the emission reductions reported are either the reductions averaged
over five years of program operation or those obtained at the end of the
fifth program year.
The engine inspection strategy is seen to be less cost effective across
all maintenance treatments than is the emission inspection procedure. This
occurs even though the engine inspection approach normally produces larger
emission reductions.
Because the magnitude and sign of the influence coefficients varied
between the three classes of vehicles studied and because the costs of
repairing some of the parameters were larger than others, a slightly
different approach was used in this study to define optimal procedures.
In previous analyses, all engine adjustments included in a particular
maintenance procedure were inspected in all vehicles and were maintained
on those cars which did not satisfy the specified pass/fail criteria.
While this approach is conceptually correct, it does not necessarily lead
to the most cost effective program. For example, incorporation of the choke
heat riser repair has a relative small effect on emission reduction (due,
in part, to the low reliability of maintenance) while the costs of its
inspection and maintenance are relatively high. Greater emission reduction
can be achieved at lower cost by merely making the pass/fail criteria for
air cleaner more restrictive. This approach eliminates the inspection and
maintenance of some engine components and adjustments for each of the fleets
in order to achieve a program which is optimal in a cost effective sense.
This new approach has not, however, required modification of the basic
structure of the economic effectiveness model. Consequently, the implica-
tions of including aH parameters in the analysis can be studied easily.
The most attractive procedure 0,e., the one having the lowest average
figure of merit of 575.) is an idle CO emission inspection {#4} followed by
the adjustment of the carburetor idle fuel to air ratio. Timing and idle
rnm were also to be
-------
but were found not to be cost effective to maintain on the other two vehicle
classes. This results from the fact that retarding basic timing substantially
increases CO emissions on pre 1966 and post 1970 vehicles thus cancelling
the beneficial effects on the figure of merit of reducing N0x and HC emissions.
(The influence coefficient for CO with respect to timing is nearly five times
as large for the post-1970 vehicles as for the 1966-70 emission controlled
vehicles.) It should be noted that this procedure does not greatly reduce
exhaust emissions and, therefore, may be of little practical interest.
The next two most cost-effective procedures, an inspection of the idle
adjustments followed by their maintenance (#1) and an emission inspection
followed by extensive "A" maintenance (#5), have figures of merit of 785
and 1340, respectively. Because of the favorable figure of merit and the
relative large HC emission reductions achieved (5 percent average and 10
percent in the fifth year), the latter procedure would be attractive for
areas with severe photochemical smog.
The smaller incremental emission reductions effected with the emis-
sion inspection procedure followed by the more extensive "B" maintenance,
result because of the relatively poor ability of this inspection procedure
to detect component failures which affect induction system performance.
Indeed, virtually all of the procedures investigated achieved only modest
CO reductions and had no influence on NO . The largest CO reduction is
J\
achieved with a direct engine inspection procedure and "B" maintenance.
Average and fifth year CO reductions are 10.4 and 15.2, respectively.
These results represent an improvement over those reported in the year-
end report. Again this can be attributed to the higher CO emission deter-
ioration rates determined from the emission deterioration experiment.
The population weighted, average emission time histories (over five
year period) for the two basic inspection approaches are shown in Figure
4-1 for an extensive "B" maintenance treatment. These profiles reveal de-
creasing emission levels with time relative to the baseline case for HC
(Panel A) and CO (Panel B) and nearly constant levels for NO (Panel C).
7\
Two opposing effects shape these profiles—emission Increases due to engine
deterioration and emission decreases due to engine maintenance and vehicle
attrition and replacement, i.e., newer cars entering the population with
34
-------
101
PANEL A
00
LLJ
Z
O
00
00
LU
oo
0
125
100
! 75.
oo -
|« 50
LU
O ?c
u ^5
OO '
z
g
oo
00
O
z
2
0
, -,,,,,M,
IIM.IIIIIIIIII
PANEL B
u****itrrr
BASELINE FLEET
— — - EXTENSIVE B (EMISSION)
MM........i EXTENSIVE B (PARAMETER)
0
2 3
TIME, YEARS
FIGURE 4-1 EMISSION TIME HISTORIES FOR AN
EXTENSIVE MAINTENANCE PROGRAM
35
-------
lower emission levels. As previously noted, all new vehicles entering the
population are assumed to have emission and engine characteristics identical
to the most advanced control systems studies in this program (1971 California
NOV Controlled Vehicles).
/\
The other two basic strategies—mandatory maintenance and hybrid
inspection and maintenance—represent two logical alternatives to the basic
procedures that have been previously studied in depth. A program of manda-
tory maintenance simply requires that all vehicles undergo periodic engine
repair based on procedures set forth by the vehicle manufacturer. This
approach eliminates the need for inspection (except for tests required to
diagnose specific engine malfunctions). Its chief disadvantage is that it
tends to be more expensive and that the adjustment of all vehicles to
manufacturer's specification may yield only marginal emission reductions
(as opposed to repairing only those vehicles with maladjustments that lower
exhaust emissions).
A hybrid program of vehicle inspection and maintenance attempts to
combine the key features of mandatory vehicle inspection antf maintenance
with those of a mandatory maintenance program. The most practical, and
perhaps the most cost-effective program, involves an idle emission inspection
and tune-up followed by the mandatory replacement of PCV valve and air
cleaner. (This procedure is especially attractive for areas characterized
with a CO problem.) Another program which offers some promise involves a
random inspection of vehicles using an idle test followed by the extensive
maintenance of vehicles failing the test. This approach is primarily
oriented toward that subset of vehicles that are poorly maintained and/or
inherently high emitters. Both basic alternatives were examined in detail.
Table 4-3 summarizes the results for the three different inspection
and maintenance strategies examined. As can be seen, the two original
inspection and maintenance procedures (#1 and #2) still appear to yield
the most cost-effective results in terms of the figure of merit. The two
hybrid programs, however, certainly provide competitive alternatives.
Their figures of merit at 1425 and 1750 compare favorably with the 1340
value for the loaded mode emission inspection procedure. Both hybrid
procedures yielded greater emission reductions than the idle engine inspec-
tion and maintenance program. The mandatory maintenance programs, on the
36
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TABLE 4-3
COMPARISON OF EVALUATED PROGRAMS
CANDIDATE PROGRAMS
MANDATORY INSPECTION MAINTENANCE
1) ENGINE INSPECTION (IDLE)
2) EMISSION INSPECTION (EXTENSIVE A)
MANDATORY MAINTENANCE
3) EXISTING MAINTENANCE
4) IMPROVED MAINTENANCE
HYBRID INSPECTION/MAINTENANCE
5) EMISSION INSPECTION WITH REPLACEMENT
1 6) RANDOM INSPECTION (50%)
FIGURE OF MERIT
$/TONH+
A B C
785 320 540
1340 560 915
5030 2200 3510
2045 870 1030
1425 1735 1010
1750 825 1280
COST PER
VEHICLE
D E
4.50 5.25
9.00 16.75
39.60 39.70
39.60 39.70
12.50 13.25
10.25 12.05
EMISSIONS REDUCTIONS, PERCENT
HC CO NO
3.3 6.1 -0.1
4.7 6.8 -0.2
8.1 5.8 -0.2
12.6 17.6 0.4
3.6 9.4 -0.2
3.8 5,.l -1.0
CO
A. COMPUTED OVER FIVE YEAR PERIOD.
B. COMPUTED AT END OF LAST INTERVAL.
C. BASED ON STATISTICALLY SIGNIFICANT EMISSIONS
REDUCTIONS FOR LAST INTERVAL.
D. BASED ON TOTAL VEHICLE POPULATION.
E. BASED ON MAINTAINED PORTION OF VEHICLE
POPULATION.
-------
other hand, showed less attractive performance. Even with improved mainte-
nance (TOO percent efficiency) the cost-effectiveness of these programs
appear marginal.
In summary, the selection of a specific procedure will depend heavily
on the type of air pollution problem under consideration. The candidate
procedures identified above were all designed to reduce HC emissions with
the possible exception of Case #5. (All figures of merit were computed using
the Los Angeles emission weighting factors.) In situations where CO is of
prime importance, the relative attractiveness of these procedures may dra-
matically change.
38
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5.0 ANNOTATED BIBLIOGRAPHY
The following bibliography is presented to serve as a chronological
guide to the many major reports prepared on this program.
"Vehicle Emissions Surveillance Study," August 20, 1971
A study was performed to establish optimum procedures for conducting
an automobile exhaust emission field surveillance program either to charac-
terize vehicular emissions to the atmosphere or to evaluate differences in
vehicular emissions which might result from different vehicle maintenance
policies. Procedures are established for providing emission measurement
standards, acquiring vehicle samples and establishing the temperature state
of vehicles prior to emission testing. Emission tests were limited to using
the 7-mode Federal cycle. Test procedures involve a number of replications
of the 7-mode cycle and use either concentration or mass emission measure-
ments. Considerable experimental data are presented establishing the engine
temperature state which can be achieved as a function of time with various
forced cooling procedures and relating exhaust emissions to the engine tem-
perature at the start of an emission test.
"Evaluation of Instruments for Vehicle Exhaust Emission Inspection."
August 20, 1971
This report contains the results of an instrument evaluation program
which had as its objective to determine the suitability of available com-
mercial instruments for the measurement of vehicle exhaust emissions. Seven-
teen automotive exhaust emissions measuring instruments were evaluated in
terms of accuracy, repeatability, response time, costs and several other
parameters. Conclusions were made with respect to instrument types best
suited for measuring carbon monoxide, hydrocarbons, carbon dioxide and
oxides of nitrogen.
^Executive Summary," Volume I. August 1971
This report is an executive summary of the Phase I study of mandatory
vehicle inspection and maintenance. This volume is one of a three-volume
set prepared at this point in the program.
39
-------
"Modeling of Inspection Maintenance Systems," Volume II, January 1972
This report presents the first definitive discussion on the develop-
ment of the Economic Effectiveness Model. The report presents a detailed
description of the basic study ground rules and underlying assumptions in-
cluding a cataloging of the candidate inspection and maintenance procedures.
It next reviews the status of the model in terms of the existing data base,
model characteristics and system components. This review includes an over-
view of the vehicle emissions, economic and operations research models.
Finally, the report provides some preliminary results for both the engine
and emission inspection procedures.
"Inspection/Maintenance Procedures Development,"Volume III. August 1971
An experiment described in the volume was performed to establish the
frequency and extent of engine maladjustments and malfunctions in an in-use
population of 1966-1969 exhaust emission controlled vehicles. An experiment
also is reported in which the influence of engine malfunctions and maladjust-
ments upon exhaust emissions was determined for the same model year class of
vehicles. Mass and mode concentration" emission data were obtained using the
Federal 7-mode test cycle.
"CRC Extended Phase I Study." January 1972
This report introduces results based on emission measurements made
using the 1972 CVS Federal Test Procedure. The analysis compares the results
obtained earlier using 7-mode emission test data with those based on data
using the 1972 Federal Test Procedure. The report also presents sensitivity
studies that were performed to determine the influence of the input data
and assumptions on the predicted results. The report concludes with a
detailed examination of the regional implications of vehicle inspection
and maintenance for four specific urban areas. In addition, a brief outline
of a new programming package designed to determine optimal pass/fail cri-
teria is presented along with a description of the revised statistical infer-
ence model.
40
-------
"Executive Summary." Volume I (Year-End Report). July 1972
This report is an executive summary of the program at this time and
was a lead volume to a six-volume set of reports.
"Mandatory Inspection Maintenance Systems Study," Volume II (Year End
Report). July 1972
This report presents a summary of the results obtained at the end of
the first year of the extended Phase I program. The analysis concentrated
primarily on evaluating the impact of garage repair effectiveness on proce-
dures selection. The report also examines the regional implications of
vehicle inspection and maintenance. Here two candidate regions, with dif-
fering air pollution problems, are analyzed using data derived from the
experimental programs. All of the analyses reported were carried out using
the Economic Effectiveness Model and the data base available at that time.
"A Documentation Handbook for the Economic Effectiveness Model," Volume III,
(Year End Report), July 1972
This handbook describes the major functional elements of the Economic
Effectiveness Model. The primary purpose of the model is to serve as a
research and design tool for evaluating a mandatory program of vehicle
inspection and maintenance. The model is designed to optimize inspection
and maintenance procedures and select the best arrangement of physical fac-
ilities for urban areas having differing air pollution and demographic char-
acteristics. The handbook consists of four sections and four appendices
which describe the approach, specific analytical models, the analytical
methods of solution, and the basic study ground rules and limiting assumptions.
^Experimental Characterization of Vehicle Emissions and Maintenance Status."
.Volume IV (Year End Report), July 1972
An experiment is described which has as its objective to determine the
rate of deterioration of engine adjustments and exhaust emissions with vehicle
use. Data are reported for the first eight months of a sixteen month experi-
ment. Orthogonal experiments designed to obtain definitive data relating
changes of engine adjustments and component malfunctions to exhaust emissions
41
-------
are described. Also presented are the results of a survey to establish the
frequency and extent of engine maladjustments and malfunction for vehicles
being used in the Detroit area. Three classes of vehicles were studied in
all of these experiments. These classes were pre-1966 vehicles without
exhaust emission controls, 1966-1970 vehicles with HC and CO emission con-
trols and post 1970 vehicles with controls for all three emission species.
Mass emission measurements were made using the 1972 Federal Test Procedure
as well as concentration measurements in selected engine operating modes.
"Experimental Investigation of Service Organization Maintenance Performance,"
Volume V (Year End Report), July 1972
The overall objective of this experiment was to develop measures of
service organization effectiveness in correcting engine part failures, mal-
functions and tune-up parameter maladjustments which cause high exhaust
emissions. Subsidiary objectives were to assess the capability of service
organizations to: detect specific malfunctions, maladjustments and failures;
return malfunctions, maladjustments and failures to manufacturer's specifi-
cations; and to respond to the type of information which might be provided
by mandatory vehicle inspection. Data are presented on maintenance cost
and the performance effectiveness of garages organizations in different
communities. The influence of service organization type (independent,
dealership and service station) on cost and performance effectiveness was
analyzed. The amount of unnecessary maintenance performed by service organ-
izations also was estimated.
"A Comparison of Oxides of Nitrogen Measurements Made With Chemiluminescent
and Non-Dtspersive Radiation Analyzers," Volume VI (Year End Report),
July 1972
Two distinctly different types of instrumentation have been widely
used to measure automotive exhaust emissions of the oxides of nitrogen (NO
and N02). Until quite recently, virtually all measurements were made using
non-dispersive infrared (NDIR) analyzers for NO and non-dispersive ultra-
violet (NDUV) analyzers for N02 until the use of chemiluminescence (CL)
analyzers gained wide acceptance for the measurement of both NO and N09 (NO ),
<_ A
42
-------
Many investigators, however, have noted that significant differences exist
in the data obtained with these two measurement techniques, although little
discussion of these differences is found in the literature. It was the
purpose of this work to investigate differences between CL and NDIR/NDUV
measurements, as applied to dilute samples of automotive exhaust gas. Basic
experimental data are presented and differences in NO emissions measured
X
with the two instrumentation systems are analyzed to establish the cause.
"Executive Summary," Volume I (Final Report), July 1973
This volume summarizes the important findings of the completed program
and supercedes the two previous executive summaries.
"Mandatory Inspection Maintenance Systems Study." Volume II (Final Report),
July 1973
This report summarizes the final results obtained from a systems study
of mandatory vehicle inspection and maintenance. The report focuses on two
areas of general importance which were not examined in early analyses. The
first area involves studying the impact on procedure effectiveness of the
rate with which engine adjustments ami exhaust emissions deteriorate with
vehicle use while the second area is concerned with determining the cost
effectiveness of alternate program strategies including mandatory mainte-
nance only. The study was conducted using the Economic Effectiveness Model
and the complete experimental data base. The report is composed of five
sections which cover the evaluation of alternative programs, system sensi-
tivity analysis and study conclusions.
"A User's Manual and Guide to the Economic Effectiveness Computer Program,"
Volume VII (Final Report), January 1973.
This manual presents a detailed description of the Economic Effective-
ness Computer program. The program provides a generalized methodology for
simulating the dynamic behavior of alternative vehicle inspection and
maintenance procedures. The model has been coded in FORTRAN IV and is
currently operating on a CRC 6500 System. The manual describes for the
programmer/user the operating instructions required to utilize the program
43
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in a variety of operating modes. It is composed of five sections and two
apprendices which provide a discussion of the model's mathematical frame-
work, input requirements and data formats,- program debugging and output
options-, and a complete list of flow schematics and computer listings.
"Experimental Characterization of Vehicle Emissions and Maintenance States,"
Volume VIII (Final Report), July 1973
Data are presented which describe the rate of engine adjustment and
exhaust emission deterioration with time and mileage. Data from the entire
16 months of testing are included in this volume in order to present a com-
plete description of this experiment. Data from the first 8 months of this
experiment were previously reported in Volume IV. Three classes of vehicles
are described which include pre 1966 cars without exhaust emission controls,
1966-1970 cars with HC and CO exhaust controls and post 1970 cars that are
equipped to control HC, CO and NO . The results of additional experiments
A
to determine the repeatability of emissions measurements and the effect of
cold soak temperature upon measured exhaust emission are also presented.
Mass emission measurements were made using the 1972 Federal Test Procedure
and concentration measurements were made in selected engine operating modes.
44
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