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Dec. 1975
FAIRBANKS, ALASKA
AUTOMOTIVE RETROFIT
EVALUATION STUDY
U. S. ENVIRONMENTAL PROTECTION AGENCY
CORVALLIS ENVIRONMENTAL RESEARCH LABORATORY
ARCTIC ENVIRONMENTAL RESEARCH STATION
COLLEGE. ALASKA 99701
CERL-004
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FAIRBANKS, ALASKA AUTOMOTIVE RETROFIT
EVALUATION STUDY
by
Ronald K. Turner
Harold J. Coutts
WORKING PAPER NO. 29
CERL-004
U.S. ENVIRONMENTAL PROTECTION AGENCY
CORVALLIS ENVIRONMENTAL RESEARCH LABORATORY
ARCTIC ENVIRONMENTAL RESEARCH STATION
COLLEGE, ALASKA 99701
December 1975
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EPA REVIEW NOTICE
This report has been reviewed by the Corvallis Environmental Research
Laboratory--Corvallis, and approved for publication. Mention of trade
names or commercial products does not constitute endorsement or recommenda-
tion for use.
AERL Working Paper Series presents results of investigations which
are, to some extent, limited or incomplete. Therefore, conclusions or
recommendations, expressed or implied, are tentative.
i i
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ABSTRACT
During the winter of 1974-1975, automotive retrofit pollution control
devices were installed on 18 domestic in-service automobiles to evaluate
their winter performance for carbon monoxide emission reduction, drive-
ability and fuel economy. The retrofit devices were (1) air bleed to
intake manifold, (2) exhaust gas recirculation plus air bleed, and (3)
catalytic converters. The emissions were measured at idle and at 2500
no-load rpm.
The air bleed devices initially functioned on 8 out of 11 installations.
For the 8-month study, the overall carbon monoxide reduction was 44 percent.
Fuel economy increased 2 to 3 percent. The exhaust gas recirculation plus
air bleed devices were successful on 3 out of 4 installations. A 30 percent
overall reduction in carbon monoxide was attained. Fuel economy increased
about 1 percent. The average carbon monoxide reduction for catalytic con-
verters was 62 percent. These devices worked on all four test vehicles.
Fuel economy was not expected to be affected.
Conclusions indicate that, technically, the retrofits work, but the
practicality of a mandatory retrofit program for the Fairbanks area is in
question.
iii
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TABLE OF CONTENTS
SECTION PAGE
I Summary of Findings ]
II Introduction 3
III Retrofit Devices 5
Air Bleeds to Intake Manifold 5
Exhaust Gas Recirculation plus Air Bleed 5
Catalytic Converters 3
IV Test Equipment and Methods 11
V Discussion 13
Data Summary 13
Air Bleeds 13
Exhaust Gas Recirculation plus Air Bleed 17
Catalytic Converters 13
Fuel Economy 13
Associated Problems and Considerations is
i v
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LIST OF FIGURES
NUMBER PAGE
1 Typical Exhaust Gas Composition vs. Air/Fuel 6
2 Installation of A1r Bleed (STP Corp.) 7
3 Installation of Exhaust Gas Recirculation
plus A1r Bleed (DANA Corp.) 9
4 Installation of Exhaust Gas Recirculation
plus A1r Bleed (STP Cprp.) 10
LIST OF TABLES
NUMBER PAGE
1 Retrofit Evaluation Preliminary Data Summary-
Phase I 14
2 Retrofit Evaluation Preliminary Data Summary-
Phase II 15
v
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ACKNOWLEDGEMENTS
We acknowledge the following individuals for their invaluable assistance
with the project:
Mr. John Miller, head of Scientific Services, Geophysical Institute,
University of Alaska, Fairbanks, Alaska, for providing test vehicles;
The U.S. Environmental Protection Agency, Region X, Seattle, Washington,
for financial support;
The STP Corporation, Santa Monica, California, and Dana Corporation,
Whittier, California, for supplying the retrofit devices and Figures 2, 3
and 4;
The U.S. Department of Transportation, Federal Highway Administration,
Washington, D.C., for use of fuel meters;
The State of Alaska, Department of Highways, Fairbanks, Alaska, for
measuring out the mileposts;
The Atlantic Richfield Company, Harvey Technical Center, Harvey, Illinois,
for use of a lead-in-gasoline analyzer;
The cooperative citizens who volunteered the use of their private
vehicles during the Automotive Retrofit Evaluation Study.
vi
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SECTION I
SUMMARY OF FINDINGS
Three types of retrofit devices were evaluated on 18 vehicles from
October 1974 to June 1975. Exhaust gas concentrations of carbon monoxide
(CO) and hydrocarbons (HC) were measured at normal idle and at 2500 rpm,
no-load engine speeds. The effectiveness of each type of retrofit varied
from vehicle to vehicle.
For the 11 pre-1969 vehicles equipped with air bleed devices, the
overall result was a 44 percent CO reduction. This performance rate
included 3 devices which failed after several months but excludes 2
vehicles on which the devices would not initially work.
Exhaust gas recirculation plus air bleed devices were installed on
one 1968, one 1969, and two 1970 vehicles. The 1968 vehicle would not
operate with either the exhaust gas recirculation plus air bleed or with
the air bleed alone. A 40 percent CO reduction was achieved on the
other three vehicles.
The air bleeds and some exhaust gas recirculation plus air bleed de-
vices included vacuum delay valves on ignition timing as part of the
retrofit package. The valves were designed to reduce HC emissions. How-
ever, it was found that during cold weather driveability tests, they caused
such excessive stumbling on acceleration, especially for the smaller engines,
that they were removed.
On 1971 to 1974 vehicles equipped with catalytic converters, the re-
duction in CO and HC was 62 and 47 percent, respectively.
Changes in fuel economy were measured both with and without retrofits.
Results were in favor of retrofitting, with an overall increase in mileage
of 2 to 3 percent for the air bleed devices and about 1 percent for the
exhaust gas recirculation plus air bleed devices. It had not been antic-
ipated that fuel economy would be affected by the catalytic converter
retrofits.
Driveability was affected on some vehicles equipped with air bleed
and exhaust gas recirculation plus air bleed devices. Hesitation and/or
stumbling on acceleration was noticed on small engine vehicles. No
effect on driveability was evident on vehicles equipped with catalytic
converters except for some reduction in road clearance. Because of
excessive choking, the retrofits did not effectively reduce cold start
emissions. Cold starts may be the highest contributor to total CO
emissions in the Fairbanks central business district.
Knowledgeable engine maintenance is critical in controlling exhaust
pollution. The lower emissions levels possible with vehicles equipped
with emission control devices cannot be realized in continued service
unless a proper inspection/maintenance program is implemented. The
effect of such a program in the Fairbanks area will be limited by the
1
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interest of the vehicle owner, the competence of the service mechanic
and his ability to understand and maintain emission control devices
using exhaust gas analyzers.
2
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SECTION II
INTRODUCTION
As part of the 1970 amendments to the Clean Air Act, states where air
quality was below Federal standards were required to develop an approved
plan to attain these limits. Since none was developed for Alaska, the
U.S. Environmental Protection Agency (EPA) formulated a plan (Transporta-
tion Control Strategy—Federal Register, November 27, 1973) to reduce
ambient carbon monoxide levels in the Fairbanks central business district.
This plan required that retrofit devices be installed in all pre-1975 light
duty vehicles in the Fairbanks North Star Borough. Fairbanks residents
questioned the affect of the devices upon their vehicles during cold weather
operation. In response, EPA decided to evaluate retrofit systems perfor-
mance in the Fairbanks area during the winter and spring of 1974-1975.
Although this report is concerned primarily with the technical aspects
of retrofitting automobiles in the Fairbanks basin, many other factors
should be considered.
The small sample size, 18 test vehicles, represents only 0.04 per-
cent of the approximately 45,000 registered vehicles in the Fairbanks
North Star Borough. Thus, extrapolating from these data may yield an
unfair indication of the effective, realistic reduction of air pollu-
tion that would result if a borough-wide program were implemented.
This study was performed on warmed-up vehicles only. Three types of
retrofit devices were chosen to be evaluated on the following U.S. manu-
factured vehicles:
1. Air bleed to intake manifold - through positive crankcase venti-
lator (PCV) line on all domestic pre-1968 light duty vehicles, hereafter,
simply designated air bleeds.
2. Exhaust gas recirculation plus air bleed - both to intake manifold
through the PCV line on 1968 to 1970 domestic light duty vehicles.
3. Catalytic converters - installed in the exhaust lines of 1970 to
1974 domestic light duty vehicles.
Initially there were 18 vehicles in the Retrofit Program:
(a) 10 with air bleeds supplied by STP Corporation (the 4 pre-1964
vehicles had to first be retrofitted with positive crankcase ventilators).
(b) 2 with exhaust gas recirculation plus air bleed supplied by
DANA Corporation.
(c) 2 with exhaust gas recirculation plus air bleed supplied by
STP Corporation.
(d) 4 with catalytic converters supplied by U0P Corporation.
3
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The authors hope that the technical information provided by this
study will stimulate thought and discussions leading to scientifically
sound decisions regarding an air pollution abatement program in the Fair-
banks, Alaska area.
4
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SECTION III
RETROFIT DEVICES
Air Bleeds to Intake Manifold
At idle most pre-1968 carburetors supply air to fuel ratios (A/F)
richer than 13 to 1, resulting in exhaust gas CO concentrations of more
than 3 percent. Figure 1 shows how the typical exhaust concentrations of
CO, 0? and HC vary with respect to input air to fuel ratio (A/F) The
stoichiometric ratio is the A/F which, for complete combustion, should
produce no CO, 02 or HC in the exhaust. The air bleeds increase the A/F
by adding air below the carburetor, resulting in more complete combustion.
All of the original air bleeds had thumb screws for regulating the air.
When too much air is added, the engine lean-misfires causing increased
exhaust hydrocarbons. Therefore, an exhaust gas CO/HC analyzer is needed
for proper installation. The installation instructions are shown in
Figure 2.
Most carburetors installed in 1970 or after were designed to operate
so lean that addition of an air bleed would cause them to lean-misfire.
Under cold weather operation, improper retrofitting caused some of the
pre-1969 vehicles to lean-misflre.
Since the vacuum delay valves (Figure 2) reduced hydrocarbon only
on accelerations and decelerations, they were removed because, in some
cases, they caused the test vehicles to stumble (have a short, sharp
reduction in acceleration rate). The air bleed devices are considered
(by the authors) to be modified to suit cold climate conditions when
the vacuum delay valve is removed.
Exhaust Gas Recirculation plus Air Bleed
In the exhaust gas recirculation system a valve is connected between
the exhaust and intake manifold. This valve allows a small amount of
exhaust gas to recirculate back into the intake. The amount of exhaust
gas recirculated is controlled by engine speed and load, being least at
idle.
The exhaust gas recirculation is primarily a nitric oxide (NO) con-
trol technique. The function of the recirculated exhaust is to dilute
the intake charge which results in lower peak combustion temperatures,
thus creating less NO.
The air bleed is the only part of this system that reduces CO
emissions. In the DANA system, the air bleed is actually an enlarged
PCV valve which admits more air into the .intake manifold. In the STP
system, fresh air is admitted through the exhaust gas recirculation
valve. Typical installations are shown in the manufacturers' installa-
tion drawings (Figures 3 and 4).
To effectively operate with the two above types of retrofits, auto-
motive engines must have carburetors and vacuum plus centrifugal spark
5
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FIGURE 1
TYPICAL EXHAUST GAS
COMPOSITION VS. AIR/FUEL
15
AIR/FUEL RATIO
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FIGURE 2
STP MODULATING AIR BLEED
Distributor
P.C.V.
Intake Manifold
Carburetor Vacuum Source
o
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advance. Many foreign vehicles lack these three features, and therefore
cannot be retrofitted.
Catalytic Converters
The two systems mentioned above reduce the creation of CO by leaning
out the A/F mixture to the engine. The catalytic converter does not
reduce engine emissions of CO and HC. Instead, it burns them in the
exhaust system. A catalyst is a substance which accelerates a chemical
reaction. In this case, the oxidation of carbon monoxide to carbon di-
oxide is catalyzed. The catalyst is platinum coated alumina pellets
approximately 1/8-inch in diameter.
The oxygen required for combustion of CO and HC (hexane in this case)
can be calculated:
Carbon Monoxide CO > + 1/2 02 » CO2
1 percent + 1/2 percent by volume
n-Hexane C6H14 + 9_1/2 °2 * 6C02 + 7H2°
100 ppm + 0.095 percent by volume
Therefore, it can be seen that for each 1 percent of CO to be oxi-
dized, one-half that amount of 02 is required. The 02 required to burn
the HC (which is usually less than 200 ppm) is small compared to that
necessary for the CO.
There are two ways to get the necessary oxygen into the exhaust. One
is by retrofitting an air pump to inject air (20 percent 02) into the ex-
haust manifold. The other is to adjust the carburetor to operate on or
near the lean side of the stoichiometric ratio (Figure 1).
Retrofitting air pump systems is difficult and expensive. In attempt-
ing a retrofit on a 1971' GMC Sprint, it was found that the dealer-supplied
parts would not fit. Experience with this and two other vehicles indicates
that the cost of installing air pumps alone can amount to over $300 per
vehicle.
Since there were considerable air pump retrofit problems, the catalytic
converters were installed without air pumps. It was found that the carbure-
tors of many newer vehicles can be adjusted lean enough to provide suffi-
cient exhaust oxygen. This was done with the catalytic converter retrofit
vehicles.
The converters are also known as catalytic mufflers because they look
like mufflers and are located in the exhaust pipe just before or in lieu
of conventional mufflers. Installation was performed by a Fairbanks
muffler shop.
8
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FIGURE 3
INSTALLATION DRAWING OF DANA
CORPORATION EXHAUST GAS RECIRCULATION
PLUS AIR BLEED RETROFIT
TO CARBURETOR VACUUM
ENGINE SPEED SWITCH &
SOLENOID VACUUM VALVE
POSITIVE CRANKCASE
VENTILATION VALVE
ifV
EXHAUST PIPE
OUTLET FITTING
STAINLESS STEEL
RETURN TUBING
I— VACUUM OPERATED EXHAUST
GAS RECIRCULATION VALVE
-v.! i\ ]
v\ m\' i
VACUUM SPARK ADVANCE
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AIR CLEANER*
FITTING
VELOCITY NOZZLE*
PCV VALVE
PCV LINE
r
&
$
DISTRIBUTOR*
VACUUM DELAY VALVE
HEAT RISER
RUBBER HOSE*
STP/EGR VALVE*
HEAT RISER
CONVOLUTED*
TUBING
DISTRIBUTOR
VACUUM LINE
FIGURE 4
* SUPPLIED IN KIT
TYPICAL V8 INSTALLATION
EGR PLUS AIR BLEED
STP/EGR NOx EMISSION CONTROL SYSTEM
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SECTION IV
TEST EQUIPMENT AND METHODS
This emission study was performed on warmed up engines at steady state
conditions. The 18 vehicles in the test program are Identified on the
Data Summary Tables (Tables 1 and 2).
Engine rpm was measured with an electric Kal-Equipment Dwell-Tac
Tester, Model #T-111. Exhaust concentrations were measured with a Horiba
Mexa 300 CO/HC meter. Oxygen was measured using a portable Teledyne meter.
The gas analyzers were placed in a heated garage on the West Ridge of the
University of Alaska Fairbanks campus. An insulated and heat traced sample
line was run outside to the vehicle being monitored. Before testing, the
vehicle was warmed up until hot air was coming from the heating system.
Emissions were first measured at 2500 rpm no-load, then at normal idle
speed, both with transmission in neutral. The test procedure is similar
to that developed by Atlantic Richfield Company for their Clean Air Caravan.
A drlveabiHty test was performed by driving east down the University
of Alaska hill to the College Road-University Avenue intersection and back
via the Nenana Highway—a total trip distance of about 3 miles. The retro-
fit device was then defeated and the tests repeated.
The air bleed was defeated by disconnecting from the PCV "T" (velocity
nozzle--Figure 2) and plugging the open hose end. The air bleed was not
always physically removed from the carburetor to distributor vacuum ad-
vance tubing since there was no flow (other than signal) on that line. To
defeat the STP exhaust gas recirculation device, both the rubber hose from
the air cleaner and the convoluted tubing (Figure 4) were disconnected.
The open end left at the velocity nozzle was plugged. To defeat the
DANA exhaust gas recirculation device, the vacuum line to the valve was
disconnected and the air bleed-PCV was replaced with the original (before
retrofit) PCV.
The catalytic converter could not be easily removed and/or by-passed
for testing so 1/8-inch nominal pipe size sample taps were welded into the
exhaust pipe above and below each converter. To prevent nonrepresentative
sampling, the downstream taps were located at least 5 pipe diameters from
the converters. The catalytic converter came with a thermocouple tempera-
ture probe installed in the approximate center of the catalyst bed. Gaso-
line tank filter neck restrictors were installed on the Plymouth, Vega
and Nova. The gasoline in all the catalytic converter retrofit vehicles
was routinely tested for lead by use of a diathiazone absorption color
comparator (ARCO lead test kit).
Constant speed fuel economy tests were performed between the 2-1/2
and 22-1/2 mlleposts on the four-lane Richardson highway, south of
Fairbanks. The Alaska Highway Department provided milepost measurements,
to an accuracy of 1:1000, for the 20-mile course. The course was rela-
tively level with maximum short distance grade less than 1 percent and
maximum curvature less than 2 percent. Each test run consisted of a 40-
mile round trip with the retrofit operating. The device was then defeated
11
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and the run repeated. A stopwatch was used in lieu of a fifth wheel to
calculate actual speed. Four fuel odometers were used. Three were manu-
factured by Columbia Systems—two of which read to 0.01 gallons and one to
0.05 gallons; one from the Kent Moore Tool Company read 0.001 gallons.
The manufacturer stated accuracy varied from + 0.02 percent for the Colum-
bia systems to +3 percent for the Kent Moore meter. They were checked and
calibrated at Arctic Environmental Research Laboratory using water and a
graduated cylinder.
12
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SECTION V
DISCUSSION
Data Summary
All significant data have been condensed and are presented In the
Retrofit Evaluation Preliminary Data Summary Tables (Tables 1 and 2).
Phase I was the Initial testing program that ran from October 1, 1974,
to February 23, 1975. Phase II continued from February 24, 1975, to
June 1, 1975. The composite test temperatures are listed after the en
gine type and displacement (cubic Inches).
Before Installation of retrofits, in most cases, the carburetors'
Idle mixtures were set to the following specifications:
Models
Pre-1968
1968-1969
1970-1971
1973-1974
Air Bleeds
In the first test phase, air bleeds effectively reduced CO over a 6
to 94 percent range. The idle and 2500 rpm removals averaged 55 and 44
percent, respectively. Prior to the second test phase,three vehicles
were removed from the program. The 1964 Chevrolet station wagon and the
1968 Ford station wagon became inoperable when retrofitted. The owner
of the third vehicle, a 1974 Ford 1/2-ton pickup, discontinued its use.
The air bleeds were effective in reducing CO over a 0 to 82 percent range
for the remaining vehicles during Phase II.
Combining the results of the idle and 2500 rpm tests for Phase I
yielded an overall average CO reduction of 39 percent. Overall reduction
from both phases was 44 percent even though only 5 of the original 11
installations were still performing.
During Phase II the air bleeds on the 1968 Chevrolet carryall, 1968
Chevrolet 1/2-ton pickup and the 1968 Jeep were found to have failed on
the dates noted on Table 2. Even though they were readjusted, they were
considered to have failed completely and willbe carried as zero removal
until the 1-year anniversary at which time they would be repaired or re-
placed. Data were handled in this arbitrary manner because 1t was
assumed that the failed device would not have been detected and corrected
except during a routine (yearly) Inspection and maintenance program.
2.5-4 percent CO
2-3 percent CO
1 - 2 percent CO
To manufacturer's specifications
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TABLE I
RETROFIT EVALUATION
PRELIMINARY DATA SUMMARY
PHASE I
From 10/1/74 to 2/24/75
COMP.
AVERAGE %
CO
AVERAGE
% HC
REMARKS AND
TEMP.
REDUCTION
REDUCTION **
FUEL CONSUMPTION MI/GAL.
VEHICLE
MODEL
ENGINE
°F
IDLE 2500 RPM IDLE 2500 RPM
AT CONSTANT 50 MPH
WITH DEVICE WITHOUT DEVICE
AIR BLEEDS
'55 Chevy
1/2TPU
V8-283
-26
59
56
-39
-49
16.8 @ -20°F 16.5 (3 -20°F
Device removed & carb. adjusted as lean
as w/device w/less stumble.
r60 Olds
Sedan
V8-394
+ 15
94
81
4
45
r60 Ford
Sedan
V8-352
+8
61
50
36
15
16.0 @ -20°F 15.6 (3 -20°F
Slight hesitation.
r63 Chevy
StnWgn
V8-283
+ 5
73
26
7
9
Device removed & carb. adjusted as lean
as w/device w/less stumble.
64 Ford
1/2TPU
16-223
-5
66
63
14
-220
15.1 @ -2°F (choking required) 14.4 @ -2°F.
66 Ford
Sedan
V8-352
-2
18
22
2
2
68 GMC
Caryal
V8-327
-3
59
77
22
30
68 Chevy
Caryal
16-250
-14
69
11
-3
3
18.6 (a 0°F 18.4 @ 0°F
68 Chevy
1/2TPU
16-250
-10
21
42
-15
30
68 Jeep
CJ5
V1-225
-8
31
6
29
64
Fuel pump failure.
EXHAUST GAS RECIRCULATION
PLUS AIR
BLEED
68 Ford
StnWgn
16-200
-4
-640
40
-230
-480
20.4 @ -4°F 19.8 @ -4°F
Device removed because of excessive
stumble. Carb. A/F swings too lean.
69 GMC
1/2TPU
V8-350
-19
56
45
42
23
14.42 @ -6°F 14.46 @ -6°F
70 GMC
3/4TPU
V8-350
-25
2
45
-6
-27
15.3 @ 10°F 14.6 (3 +10°F
(w/o EGR but
w/PCV-AB)
70 AMC
Sedan
16-232
+6
78
-n
36
25
23.6 @ -10°F 23.5 G> -10°F
CATALYTIC CONVERTER
71 GMC
Jimmy
16-250
+23
50
66
51
49
21.3 @ 30°F 16.8 @ -2°F
(No air pump)
73 Ply.
Sedan
V8-318
—
—
--
Catalyst not in
yet.
Mo air pump.
73 Chevy
Vega
14-140
+ 14
80
66
42
28
No air pump.
74 Chevy
Nova
16-250
-20
75
83
78
40
No air pump.
*A11 pre-1964 vehicles had to first be retrofitted with positive crankcase ventilation (PCV) systems.
** All negative percent reductions mean an actual increase in emissions.
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TABLE II
RETROFIT EVALUATION
PRELIMINARY DATA SUMMARY
PHASE II From 2/24/75 to 6/1/
COMP. AVERAGE % CO AVERAGE % HC REMARKS AND
TEMP. REDUCTION REDUCTION FUEL CONSUMPTION MI/GAL.
VEHICLE
MODEL
ENGINE
°F
IDLE
2500 RPM
IDLE
2500 RPM
AT CONSTANT 50 MPH
AIR
BLEEDS
55 Chevy
1/2TPU
V8-283
24
76
37
37
23
Engine stumbles on acceleration w/AB.
60 Olds
Sedan
V8-394
40
77
72
50
28
No driveability difference with device.
60 Ford
Sedan
V8-352
35
82
67
20
21
Vehicle out of service; low mileage accumulated.
66 Ford
Sedan
V8-352
42
24
21
17
21
Engine idles rough w/AB.
68 GMC
Caryal
V8-327
24
25
75
20
54
Engine tuned up 3-15-75.
68 Chevy
Caryal
16-250
26
0
0
*
*
AB failure 2-24-75.
68 Chevy
1/2TPU
16-250
20
19
45
*
*
AB failure 3-31-75. 16.3 & 16.7 mi/gal. w/wo AB @ l°l
68 Jeep
CJ5
V6-225
30
0
0
*
~
AB failure 2-26-75. 19.6 & 19.5 mi/gal. w/wo AB @ 12'
EXHAUST GAS RECIRCULATION PLUS AIR BLEED
69 GMC
1/2TPU
V8-350
42
76
57
64
43
_ _ _
70 GMC
3/4TPU
V8-350
18
26
*
32
7
Engine in poor operating condition.
70 AMC
Sedan
16-232
29
74
42
28
27
Carburetor jet backed out 1/4 turn, 5-6-75.
CATALYTIC CONVERTER
71 GMC
Jimmy
16-250
30
31
57
19
51
Engine misfires; unstable idle mixture.
73 Chevy
Vega
14-140
32
92
32
49
26
Temperature of CC 900°F @ idle.
73 Ply.
Sedan
V8-318
43
78
68
67
51
Temperature of CC 1175°F ©idle.
74 Chevy
llova
16-250
26
31
61
49
52
CC striking ground, breaking manifold-tailpipe joint.
~Static conditions showed negative HC reduction.
Dynamic test revealed no negative HC reduction.
Contradictory data deleted.
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Other problems with individual air bleed devices were encountered.
After 5 months, the air bleed on the 1968 1/2-ton pickup failed because
vibrations had loosened the adjusting screw. A retaining spring was
installed around the screw and the device was readjusted.
The owner of the 1968 Jeep encountered a power loss and sluggish
engine performance. Thinking he might improve engine response, he
screwed down the air bleed adjustment, defeating its function. The
initial problem was traced to a faulty carburetor which was repaired
and the device readjusted. After 4 months, the device again failed and
had to be readjusted. An inspection and maintenance program would be
able to detect and correct such failures.
The air bleed on the 1968 Chevrolet carryall was installed inside
the garage at approximately +50°F. Driveability tests at -30°F revealed
stumbling and engine kill at stops caused by a lean A/F mixture. To
cure the driveability problem, the air bleed was then readjusted outside
at -30°F. Based on this experience, it was determined that all air bleed
installation adjustments should be done outside in ambient air during one
of the colder winter days. This particular air bleed device failed to
modulate after the second month.
In general, there were no noted driveability problems with air bleeds
on the larger eight cylinder engines. However, the air bleeds so severely
affected driveability of the 1955 and 1963 Chevrolets that they had to be
removed. The manufacturer felt the problem was lack of ported vacuum sig-
nal to the distributor vacuum advance. Their advice was to adjust idle
mix jets for 2 percent CO. This was done with some improvement in drive-
ablity. However, when the air bleed was removed and the carburetor reset
at 2 percent exhaust CO, the driveability improved further. On Feb-
ruary 11, 1975, a 2 cfm nonadjustable (vs. the regular 3 cfm adjustable)
air bleed with two vacuum delay valves was installed on the 1955 pickup.
With this smaller device the owner reported acceptable driveability with
minor stumbling.
Initially, the 1964 Ford 1/2-ton pickup had an intermittent leak in
its induction system. With this problem it took several days to get its
air bleed working properly. The operator reported that considerably more
choking was required at temperatures of -25°F or colder.
Three vehicles with the air bleed had an increased tendency to diesel
after the ignition was switched off. The three major causes of dieseling
are: [1] too high an idle speed (rpm), [2] too lean a mixture (A/F), and
[3] too low octane fuel. The air bleeds lean out the idle mixture and
for winter operation Fairbanks drivers usually set the idle speed above
the manufacturer's specifications., thus aggravating the problem.
The disadvantage of leaning out the engine at low temperatures is the
risk of increasing HC emissions (lean-misfire). On some vehicles the HC
reduction was less than 10 percent. There were a few vehicles which had
negative HC reductions. The retrofit manufacturer indicated there should
be no HC increases (negative percent reduction) under loaded tests. Two
vehicles, the 1968 1/2-ton pickup and the 1968 Chevrolet carryall, were
instrumented and tested under load. Analytical data confirmed the manu-
facturer's statement. The Phase II data showed about the same percentages
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HC reduction. Because the static testing procedure does not apply for HC
in air bleed type devices, whenever negative reductions were obtained, the
data were deleted from the Phase II Data Summary Table. The Inability of
the static test procedure to accurately quantify HC reductions is of little
significance since this study was aimed primarily at determining CO reduc-
tion performance.
As a research effort to investigate a way to reduce CO and HC effec-
tively, and determine a more economical retrofitting procedure, a PCV
valve designed for a larger engine displacement (307 CID) was installed
on the 1968 Chevrolet carryall equipped with a 250 CID engine. Since the
exhaust gas recirculation system incorporated its air bleed in the PCV
valve, it was felt that this combination would allow more air to bleed
into the Intake manifold simply by making the PCV valve larger. For
comparison, the STP air bleed device was removed and data were taken
using the larger engine PCV valve. Test results upheld this theory.
However, in this case the larger PCV was not as effective in reducing
air pollution and the air bleed was reinstalled.
Exhaust Gas Recirculation Plus Air Bleed
It should be noted that the STP air bleeds and the air bleeds in the
exhaust gas recirculation plus air bleed devices are different types (Fig-
ures 2 and 3).
Excluding the 1968 Ford and the 1970 GMC from the Phase I data, the
exhaust gas recirculation plus air bleed retrofits would probably have
performed as well as the air bleed only group, except that the fuel economy
improvement was less. Overall CO reduction for Phase II was approximately
43 percent for the three exhaust gas recirculation plus air bleed devices.
The overall average CO reduction for both phases was 40 percent for the
1969 and 1970 vehicles.
Some problems were also encountered with these devices. Just after
installation, the PCV-air bleed (Figure 3) on the 1970 GMC 3/4-ton pickup
was intermittently clogging and sticking open (apparently due to machining
lubricants) resulting in poor performance. Cleaning with acetone solved
the problem, but the problem caused overall poor performance (Phase I of
the Data Summary Tables).
Another PCV-air bleed suspected of clogging had been installed on
the 1968 Ford station wagon which had a carburetor that independently
varied the idle A/F mixture. Without any retrofit device, the exhaust
CO would vary from 1 to over 4 percent within two to three minutes during
idling. Unsuccessful attempts were made to clean the idle ports. Instead
of reducing emissions, the idle CO with the device increased over six
times (Phase I of the Data Summary Tables). The DANA retrofit device was
removed because it caused excessive stumble and an STP air bleed was
attached. The engine would not run with the air bleed so the vehicle
was dropped from the test program.
The owners of the 1969 GMC 1/2-ton pickup and the 1970 AMC sedan
noted sluggishness on acceleration with the exhaust gas recirculation
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devices. This was probably due to leaness because of the air bleed or
flame dilution by the recycled exhaust gas.
Catalytic Converters
Before the catalytic converters would work properly, the carburetors
had to be leaned out to get O2 in the exhaust (Figure 1). These devices
were not effective in reducing CO emissions during cold starts because
the catalyst bed temperature had to be warmed to above 600°F before it
would burn the CO to CO2- The warm-up period appeared to range from 3
to 6 minutes. The overall average reduction of CO and HC for both test
phases was 62 and 47 percent, respectively.
The catalytic converter performance appeared to have deteriorated
between Phase I and II. But analytical caution should be exercised since
the data in Phase I are based on only one or two tests. Routine tests
for lead in the gasoline have ruled out lead poisoning of the catalyst.
The idle A/F on the Nova and Jimmy carburetors dropped during the test
period, thus lowering catalytic converter performance. However, the
devices had no effect upon driveabi1ity.
Fuel Economy
The fuel economy effect of the retrofits is listed in the Data Sum-
mary Tables. The fuel consumption (miles per gallon) is listed right
before the test temperature. All tests were performed at constant speed
of 50+2 miles per hour. Each test result is based on a 40-mile run
both with and without the retrofit device. Tests were run consecutively
except on the vehicles equipped with a Catalytic Converter. In general,
the air bleed device varied the mileage from -2 to +5 percent, averaging
a 2 to 3 percent increase. The exhaust gas recirculation plus air bleed
devices increased the mileage by about 1 percent. The catalytic converter
could not be easily removed so the mileage tests had to be performed be-
fore and after installation. The catalytic converter was not expected
to affect mileage. The 4x4 utility vehicle yielded better mileage at
+30°F than at -2°F. Apparently considerable energy (gasoline) is required
to overcome the viscous shear of cold lubricants.
Associated Problems and Considerations
Several problems associated with retrofitting have been noted, but
there were many others.
The first exhaust gas recirculation plus air bleed was installed on
the 1970 AMC. Installation time was 8 hours. Since this was the first
device for the program, extensive time was required due to misleading
installation instructions provided by STP Corporation. As a result,
the device was initially installed on the intake manifold rather than
the exhaust manifold. This caused the engine to surge as excessive
fresh air was drawn into the intake manifold. The associated vacuum
delay valve caused extensive stumble after installation. After removal
of the valve, the owner reported no problems with the retrofitted engine
during the first three months. During the next three months the owner
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reported that the exhaust gas recirculation valve Intermittently stuck
causing erratic Idle. He could solve the problem by lightly tapping the
valve with a mallet. Finally, after six months, the idle surging and
dying problem became so severe that the owner requested removal of the
device. Upon removal, 1t was found that the hose leading from the carbure-
tor to the velocity nozzle was ruptured, apparently causing the problem.
Experience with the 1970 AMC and 1968 Ford Indicates that adding a
retrofit to any engine increases vulnerability and raises the possibility
of partial failure.
The 1968 GMC carryall was given a second tune-up midway through
Phase II because the owner felt 1t was Idling too rough. He backed out
the idle jets approximately one-fourth of a turn to enrich the mixture
causing the idle carbon monoxide levels to increase from 0.2 percent to
3.5 percent with the air bleed. The owner requested that the idle be
left in this state. In this case, the air bleed device probably enticed
the owner to adjust the A/F mixture. This over-riding effect resulted in
higher CO emissions than before retrofitting, thus defeating the entire
retrofit Idea. The vehicle would have easily idled at less than 3.5
percent CO without the air bleed.
The 1968 GMC 1/2-ton pickup required the installation of a new car-
buretor due to mechanical linkage wear. The exhaust gas recirculation
plus air bleed device had been added to the engine prior to the breakdown
and ultimate failure of the carburetor. The owner thought that the retro-
fitting was partially responsible for improper carburetor operation. A
new carburetor was reinstalled giving an Idle CO of 0.9 percent. Several
months later the Idle mix screws were adjusted according to the industry
specifications. The Idle CO then increased from 0.9 percent to 2.2 percent
with the device again showing that a simple carburetor adjustment can
override the objective of retrofitting gasoline engines.
The above two examples illustrate what'could happen in a mandatory
program if the owner decides to readjust his idle mix to compensate for
lack of (or apparent lack of) engine performance due to the retrofit.
It should also be realized that the air bleed and exhaust gas recircula-
tion plus air bleed devices tested may well be modified or deleted if
the manufacturers go into mass production. Therefore, some of the initial
failures and problems encountered in these tests may be replaced by
others.
Within one month after installation, the catalytic converters on the
1973 Plymouth, attached with muffler clamps, were knocked off—presumably
due to rough roads. They were welded back into place with no subsequent
difficulties. The converters on the Nova and Vega also hung low and bumped
high spots in the road, which caused leaks at the exhaust pipe manifold
joints. Because it was mounted up between the frame and the transmis-
sion, the converter on the Jimmy did not have those problems.
Experience with the air bleed and exhaust gas recirculation plus
air bleed types of retrofits during this study indicates that they are
not effective on vehicles with malfunctioning carburetors. Of the 18
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test vehicles, the 1963 Chevrolet, the 1968 Ford, and the 1969 GMC 1/2-ton
pickup would require new carburetors for effective retrofit performance.
Extrapolating these data to all pre-1971 Fairbanks area vehicles indicates
that as many as 10 to 20 percent would require new carburetors for retro-
fitting. The new carburetors would cost approximately $75 to $200 in-
stalled.
Since the air bleed and exhaust gas recirculation plus air bleed
devices are mass produced, they should cost less than $35 for parts and
$20 to $40 for installation. However, the air bleeds require use of an
exhaust gas analyzer for installation. The several garages in the Fair-
banks area that have these analyzers do not routinely use them.
The catalytic converters used in this study cost $115 for the 4
cylinder, $225 for the 6, and $230 for the 8 cylinder vehicles. The
installation charges ran from $40 for the 4 cylinder to $100 for the 8
cylinder vehicles. If they were retrofitted for thousands of vehicles,
the cost should be substantially less. For instance, earlier this year
in Canada, if one were to order a 1975 light duty GM vehicle without a
catalytic converter, the total cost would be about $80 less than with the
converter.
The deterioration factors were not calculated for all the retrofits
because they could not be reasonably separated from the deterioration
factors of other engine components. The authors feel that for Fairbanks
winters, mileage accumulation may not be as significant as the number of
cold starts in causing engine component deterioration. For example, one
cold start at -50°F may put more wear on the valve train than would 1000
miles of highway driving.
The accumulated mileage for the retrofitted vehicles was: 16,000 miles
for the air bleed, 8000 miles for the exhaust gas recirculation plus air
bleed, and 4000 for the-catalytic converter equipped vehicles. Individually,
the accumulations were from 100 miles for the 1960 Ford to 5800 miles for
the 1970 AMC.
This study was too short to determine any long-term effectiveness of
any mandatory retrofit program and, at best, results were only semiqualita-
tive. However, it does document some of the initial problems associated
with retrofitting.
Before a vehicle retrofit program is implemented for the reduction of
CO levels in the Fairbanks area, the problems encountered during this
Study must be considered. An inspection/maintenance program must be
initiated before retrofitting can be effective. Lower levels of exhaust
pollution will result only when the need for proper maintenance is under-
stood and carried out by vehicle owners and competent service mechanics.
Of major concern is the ability to enforce a mandatory retrofit pro-
gram. The driving public has a somewhat negative viewpoint concerning
automotive air pollution equipment. Individuals are interested in the
performance of their vehicles as a means of dependable transportation.
Added expenses and vulnerability are viewed as a personal hassle rather
than health insurance.
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Finally, emissions from the vehicles operated during Fairbanks' win-
ters can be divided into two parts. First, a cold start which involves
2 to 15 minutes of idling; and second, a warm run. It may be that the cold
start portion contributes more CO than the warm run for a typical trip from
the central business district. Preliminary cold start data obtained by the
authors and the University of Alaska* indicates that, because of excessive
choking and catalyst warm-up time, the retrofits are not effective before
the engine warms up.
* For more information on this subject see the interim report entitled "Cold
Start Automotive Emissions in Fairbanks, Alaska," by L.E. Leonard, Univer-
sity of Alaska, Geophysical Institute, Fairbanks, Alaska, Report UAGR-239,
July 1, 1975.
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