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Aug.1973
niniHMi'm"1 ||L| s.i
*t PRO^
COLD REGIONS
AUTOMOTIVE EMISSIONS
U. S. ENVIRONMENTAL PROTECTION AGENCY
ARCTIC ENVIRONMENTAL RESEARCH LABORATORY
COLLEGE, ALASKA 99701
-------
COLD REGIONS AUTOMOTIVE EMISSIONS
This report is the result of the combined effort
of the following people and organizations:
H. J. Coutts
U.S. Environmental Protection Agency
Arctic Environmental Research Laboratory
L. E. Leonard
Geophysical Institute
University of Alaska
K. W. MacKenzie, Jr.
Fairbanks North Star Borough
Dept. of Environmental Services
Working Paper No. 19
August 1973
-------
This paper presents results of investigations
which are to some extent limited or incomplete.
Therefore, conclusions or recommendations—ex-
pressed or implied—are tentative. Mention of
commercial products and/or trade names does not
constitute endorsement.
-------
ERRATA
"COLD REGIONS AUTOMOTIVE EMISSIONS"
page 1 reads carbon dioxide (£0).....
line 7 should read carbon monoxide (CO).
page 18 vertical axes reads 40, 60, 70, 70, 80.
F1g. 7 should read 40, 50, 60, 70, 80
page 22 The CO emissions are calculated as 111 CO
& 23 min
They should be listed as centl'111: CO
min
-------
ABSTRACT
Cold Regions Automotive Emissions
In Fairbanks, Alaska, during February and March 1973,
the emissions of 631 vehicles were analyzed at idle and ad-
justments were made to reduce CO and HC emitted. It was
found that proper adjustment of in-use vehicles could re-
sult in approximately 34% reduction in CO and a 12% reduc-
tion in HC produced at idle. Emission levels of propane
and gasoline and diesel fueled vehicles were measured and
compared. Various pollution control devices are discussed
and considered for cold weather use and conclusions are
drawn. Ice Fog is considered as it relates to CO emission
control.
i
-------
ACKNOWLEDGEMENTS
For their invaluable assistance to this project, we ac-
knowledge the following individuals with sincere thanks:
Mr. John Sweet, Environmental Conservation Manager, Alaska
District, Atlantic Richfield Company, for securing necessary
test equipment; Mr. Richard F. Basset, Retail representative
of Standard Oil of California, Western Operation, Inc., for
providing a site to test the vehicles of the general public;
the personnel of the GSA Motor Pool, State Highway Department
Motor Pool, Yellow Cab Company, and Municipal Utilities System
Motor Pool for their cooperation in testing fleet vehicles,
and the citizens of Fairbanks for their overwhelming response
and cooperation in testing vehicles for the general public.
In addition, we wish-to express a special thank you to
Dr. Fred L. Voelz of Atlantic Richfield's Harvey Technical
Center for technical guidance, analytical assistance and
general support during the Vehicle Emissions Analysis Program.
ii
-------
TABLE OF CONTENTS
Page
Abstract i
Acknowledgements ii
Table of Contents iii
I. Introduction 1
A. Background 1
B. Scope 2
II. Vehicle Emission Analysis Program 5
A. General 5
B. Equipment and Procedure 5
C. Discussion of Procedure 8
D. Theory of Idle Emission Adjustments 11
E. Results 13
F. Direct Comparison of Emissions 20
1. Gasoline vs. Propane 20
2. Foreign vs. Domestic 21
3. Domestic vs. Diesel vs. Propane 23
6. Emission Testing Cycles 24
III. Emission Control Methods 26
A. General 26
B. Air Injection System (Air Pumps) 27
C. Catalytic Converters 29
D. Lean Mixture Operation 31
E. Surraiary Comparison 33
F. Inspection and Maintenance. Programs 35
G. Fuel Volatility 35
H- Cold Start 36
I. Fuel Economy 37
J. Ice Fog 38
IV. Summary 42
V. Conclusions and Recommendations 43
VI. Research Needs 45
VII. References 47
iii
-------
I. INTRODUCTION
A. Background
Alaska is the largest, most sparely populated, least industrialized
state in the nation. Yet its major interior city, Fairbanks, stands as one
of the great environmental ironies in this country today. This city with
an area-wide population of only 44,000 has air pollution levels which rival,
and surpass, those of New York and Los Angeles. The air quality of the
Fairbanks area is degraded mainly by three types of pollutants. These are
carbon dinviiip (CO), ice fog and dust particulates. The toxic health effects
(1 2)
of CO have been well documented. ' ' Records have shown Fairbanks to have
one of the most acute CO problems of all American cities. This paper deals
with this pollutant. Ice fog air pollution is unique to regions with extremely
(3)
cold climates. The nature of ice fog has been well defined/ ' The main ob-
jection to this cold weather phenomenon is that it severely restricts visi-
bility under abnormally difficult driving conditions (-30°F or less). Ice
fog often occurs simultaneously with high ambient CO levels. However, high
CO levels occur much more frequently than ice fog. Therefore, ice fog is dis-
cussed here only with respect to its interrelationship with methods to con-
trol CO emissions. The other pollutant, dust particulate, will not be con-
sidered in this report.
(4)
Studies showv ' that over 80% of the CO present in the low level ambient
air of the Fairbanks area is produced by the internal combustion engine in
motor vehicles. The conclusion here is simple: if air quality is to improve
in Fairbanks, CO contributions from the automobile must be greatly reduced.
The procedure for reducing these emissions is where the dilemma facing Fair-
banks clearly reveals itself.
1
-------
In Fairbanks, motor vehicles must perform the routines of daily operation
at temperatures from -50°F in winter to +95°F in summer. No other city in
the United States experiences such temperature extremes. Fairbanks is located
in a natural bowl surrounded on three sides by hills and has little wind. Arc-
tic winter conditions cuase some of the most extreme thermal inversions in the
world; these inversions trap stagnant air and pollutants. These environmental
differences drastically change the character of motor vehicle utilization com-
pared to cities in the southern 48 states. It is these differences which make
it difficult to directly apply solutions to the Fairbanks situation which have
proved successful outside of cold regions.
Fairbanks must then look inward to solve its unique problems. The research
necessary to find solutions must be done considering that uniqueness. This re-
port is a part of such a research effort.
B. Scope
Due to the severity of vehicle-emitted CO in the Fairbanks area and the non-
availability of research data pertaining to such emission in other areas with
cold climates, the Department of Environmental Services of the Fairbanks North
Star Borough initiated a research program to be known as the Vehicle Emissions
Analysis Program (VEAP). This, report presents the results of that program as
well as other cold region emissions information obtained by the investigators.
In this project, the Fairbanks North Star Borough was assisted by: the
Atlantic Richfield Company (ARCO), which supplied necessary instrumentation, per-
sonnel to instruct in its operation, and data interpretation; Arctic Environmental
Research Laboratory, Environmental Protection Agency (EPA) and the Institute of
Arctic Environmental Engineering (IAEE)* of the University of Alaska who supplied
engineering and technical personnel for both acquisition and reduction of the
data obtained.
~Now part of the Geophysical Institute of the University of Alas-ka.
2
-------
As originally conceived, VEAP would be modeled after the Atlantic Rich-
field Company's Clean Air Caravan Program which had been carried out in
(5)
several cities in the lower 43 states: ' The field testing was planned to
run for a period of four weeks during February and early March 1973, a time
when the average temperature is in the neighborhood of 0°F. Emissions from
private and governmental fleet vehicles as well as those of the general pub-
lic were to be tested. The program was originally outlined as follows:
Part I: Fleet vehicles only at hot idle {idling after engine warm-up)
Measure: RPM
% CO
Parts per million (ppm) HC
Total gas flow at constant RPM
Exhaust gas temperature
Also check effect of air inject into exhaust manifold pollution
control device (limited mainly to 68, 69, arid 73 model years).
Time requirement using two men: 3/4-1 hour/vehicle; or 8-10
vehicles/day.
With one extra man, Orsat Analysis for carbon dioxide (CCL)
and oxygen (0^) could.also be accomplished.
Assuming the fleets have 40-50 vehicles each, then run tests
as follows:
1st week - GSA Motor Pool
2nd week - State Highway Dept. Motor Pool
3rd week - Propane fueled fleet (Yellow Cab)
Total: 120-150 fleet vehicles
Part II: General Public Vehicles (Voluntary) - 4th week.
Measure: RPM
% CO
HC
Check effect of proper idle mix screw adjustment (only if
mechanic is available).
30-60 vehicles/day x 5 days = 150-300 vehicles total.
3
-------
While all of the tests set forth in the original plan were not accomplished,
(see VEAP Program) the total number of vehicles tested far exceeded the early
estimates.
It was thought that the accomplishment of this project would provide
some of the information necessary for governmental organizations to plan re-
alistic strategies to improve air quality in the Fairbanks area. It would
also provide an opportunity for a critical assessment, from an engineering
standpoint, of the physical problems associated with the operation of motor
vehicle emission control systems in cold regions.
This report is limited to discussing the problem of reducing CO emissions
from internal combustion motor vehicles in cold regions as it relates to the
vehicles themselves. Other methods for reducing CO, such as, replacement of
private vehicles with mass transit, electric (battery) powered vehicles, stream-
lining traffic patterns, and limiting vehicle miles traveled are not considered
here. However, all of those measures represent viable solutions or partial
solutions to the CO problem. Specifically, this study has concentrated on
gasoline engines of United States manufacture, some of foreign manufacture,
propane fueled engines and diesels.
4
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II. VEHICLE EMISSIONS ANALYSIS PROGRAM
A. General
The VEAP testing was done during the period of February 6 to March 3,
1973. The air temperatures experienced during that period are shown in
Table 1. As previously mentioned, not all of the data were acquired as
called for by the original plan:
1. Total gas flow measurement at constant RPM was not made on any
vehicles.
2. Exhaust gas temperature was not measured.
3. Orsat analysis on fleet vehicles was not made, but oxygen (02) was
measured for all vehicles.
At the end of the testing program, emissions from over 600 vehicles had been
analyzed.
B. Equipment and Procedure
Exhaust gas concentrations of CO and hydrocarbons (HC, measured as hexane)
were measured for each vehicle using an Olson-Horiba, nondispersive infrared
analyzer. Exhaust system leaks or air pump operation was checked with a Tele-
dyne (>2 meter. Engine speed was measured in RPM with a clip-on (high tension
leads) type induction tachometer. Positive crankcase ventilation (PCV) valves
were checked when necessary with a manometer. Figure 1 is a schematic of the
test set up. The following describes the test procedure carried out on each
vehicle.
1. A vehicle with the engine running at normal operating temperature was
driven into position. The emission sampling probe was placed in the
exhaust pipe and the tachometer was connected. The idle speed, model
year, manufacturer, mileage, engine type, and displacement, if readily
available for the vehicle, were recorded.
5
-------
TABLE 1
Temperature in Fairbanks, Ak., from February 6 to March 3, 1973
8:00 a.m. — 5:00 p.m.
MAXIMUM MINIMUM
DATE TEMPERATURE TEMPERATURE MEAN
Feb. 6 9 -10-2
7 10 - 6 1
8 10 -12 - 2
9 0 -18 -11
10 11 -24 -10
11 10 -26 -10
12 0 -15 - 8
13 0 -17 - 8
14 - 1 -25 -14
15 - 5 -13 - 8
16 2 -16 - 7
17 - 1 -17 - 9
18 11 -19 - 2
19 35 - 8 19
20 34 20 25
21 28 11 18
22 29 13 21
23 18 - 6 8
24 22 - 1 12
25 21 -15 7
26 21 -17 4
27 13 -18 2
28 12 3 8
March 1 9 - 2 4
2 4 - 7 - 2
3 2 -16 - 5
6
-------
BUILDING WAIL
HOSE
SAMPLE PROBE
IN EXHAUST PIPE
CO
VEHICLE
WINDOW
HC
ANALYZER
2
MITER
TACH
TEST SETUP
FIGURE 1
7
-------
2. The condition of the PCV (Positive Crankcase Ventilation) valve
was then checked for vacuum by plugging it with the thumb. Those
that failed this test were more carefully checked with a dry type
manometer.
3. With the transmission in neutral, the engine speed was increased
to 2500 -100 RPM and the steady state CO and HC emissions were
recorded. The engine speed was then returned to idle.
4. The steady state CO and HC levels were recorded at idle.
5. Carburetor adjustments were made if appropriate.
C. Discussion of Procedure
For a full understanding of the significance of each part in the pro-
cedure, a short discussion of the function of the internal combustion engine
carburetor is necessary.
Ninety-five percent of the vehicles tested during this program were powered
by internal combustion engines using gasoline as fuel and the conventional car-
buretor to meter fuel to the engine. It is the function of the carburetor to
properly mix fuel and air for introduction into the combustion chamber (cyl-
inders) to sustain efficient combustion throughout the speed and power band of
the engine. To accomplish this, the modern carburetor is divided into two
major systems, the main metering system and the idle system.
The main metering system is the system by which the carburetor operates
while the engine is running at speeds above idle and/or under load. A simpli-
fied schematic of this system is shown in Fig. 2. Under these conditions, air
flows are high and the resulting pressure drop in the venturi (barrel) draws
fuel up the delivery tube spilling it into the barrel where it mixes with the
air and continues to the intake manifold. The amount of fuel delivered to the
barrel is metered by the main jet. This restricting orifice is fixed in size
8
-------
FUEL
AIR
NEEDLE
VALVE
VENT
VENTURI
ftOAT
CHAMBER
\ DELIVERY TUBE
THROTTLE
VAL/E J
MAIN JET
SIMPLE CARBURETOR MAIN METERING SYSTEM
FIGURE 2
AIR —«>
BLEED
FLOAT
CHAMBER
MDLE
METERING JET
• IDLE
I DISCHARGE
1 PORT
IDLE MIXTURE
SCREW
(a/f)
THROTTLE
NEARLY CLOSED
SIMPLE CARBURETOR IDLE SYSTEM
FIGURE 3
9
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dependent on specific engine parameters such as, displacement, duty cycle,
etc. If the main metering system is functioning properly and if the intake
manifold is flow balanced, the combustion in the cylinders is very efficient
and the resulting CO and HC emissions are low (<2% CO and <200 ppm HC). The
2500 RPM no-load test verifies the condition of this system and detects any
gross malfunctions which could not be compensated for if adjustments are re-
quired to the idle system. If the 2500 RPM CO concentration was above approxi-
mately 4%, then the vehicle's air filter and choke were examined. If they ap-
peared to be restricting air flow, the 2500 RPM test was again run with air
filter removed and/or choke held open to demonstrate ary differences to the
motorist. Other diagnostic information can be revealed by the emission levels
of this test but will not be covered in this report.
The second carburetor function is the idle system. See Fig. 3. When the
engine is not operating under load, an idle system is required because air
flow through the venturi is too small to create the pressure drop necessary to
draw fuel from the delivery tube of the main metering system. At idle, a re-
latively rich mixture (low air to fuel ratio) is metered to the engine to keep
it running at low speeds (idling). Combustion at idle is normally less effi-
cient than under steady-state load, thus, emission levels of CO and HC are ex-
pected to be high during idle. However, unlike the main metering system, the
idle system is equipped with a fuel-air mixture control valve which is adjust-
able (idle mix screw). The main point of the VEAP study was to obtain these
idle emission levels and to find what improvements could be made in the emission
at idle by adjustment to the carburetor idle mix screw. When the vehicle's
emissions of CO and HC were recorded at idle, the levels were compared with the
(51
limits used the Atlantic Richfield Company's Clean Air Caravan. y These
approximate limits were:
10
-------
Pre-1968 model year 3.5 to 5% CO
1968-1969 model year 2.0 to 32J CO
1970 & newer models 1.0 to 1.5% CO
If the CO emissions were above these limits, the idle mix screw was adjusted
with the owner's consent to bring it within the limits. In some cases, satis-
factory adjustment could not be made due to other engine problems not asso-
ciated with the carburetion system. However, in the majority of cases, proper
adjustment was easily made.
D. Theory of Idle Emission Adjustments
Tlae curves of Figure 4 show the typical response of a spark-ignition
internal combustion engine to adjustment of the air-fuel ratio (A/F) with the
idle mix screw. Beginning at the left, it is clearly seen that CO concen-
tration decreases as the A/F increases (leaning out). This is because com-
bustion is more efficient when more air is made available for the reaction.
The HC curve follows a similar course, however, a point is reached where the
HC concentration begins to increase while CO continues to decrease. This re-
sponse is caused by what is normally called misfire. For proper ignition by
the spark plug, the fuel must be vaporized in the intake air. As the A/F is
increased, a point is finally reached when the mixture is simply too lean to
ignite and thus is passed through the system to show up as an increased HC
emission. Since vaporization is necessary, the temperature of the intake air
is important. The colder the air in the intake manifold the less easily the
fuel vaporizes. As a result, misfire occurs at a lower A/F (richer mixture)
with colder intake air (Cold HC curve). Other research has found, in general,
lower temperatures produce higher emissions. Therefore, the optimum
idle adjustment (A/F) is that at which CO and HC are at their relative minimums.
11
-------
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12
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E. Results
The data summary for the VEAP study is presented on Table 2. Figure 5
compares the population of model year of the vehicles tested in the VEAP
study to those in which the total number of vehicles in the Fairbanks area
are considered. A computer solution was used to obtain the reduction in CO
and HC emission which would be statistically possible for the total Fairbanks
vehicle population based on the results of the VEAP study. For this weighted
average, 400 vehicles of the general public from the VEAP study were considered.
The vehicles which were not adjusted or could not be adjusted to gain any im-
provement in emissions were averaged along with vehicles to which adjustments
were made. The following results were obtained:
The VEAP data for domestic manufactured vehicles are plotted in Figures
6 and 7. These curves of vehicle population vs. exhaust CO concentration al-
low one to determine the percentage of a model year grouping that has CO
emissions above a specific concentration. Figure 6 shows that the newer models
are designed to run leaner (higher A/F) than the older model vehicles; i.e.,
to produce a lower exhaust CO concentration. In comparing these curves with
similar curves (for the same model years) from the "lower 48" Atlantic Rich-
field Company's Clean Air Caravan,^ it was found that the VEAP pre-68 models
(for population greater than 10%) emitted a lower CO level; i.e., they were
idling leaner. The authors thought that, due to the 1967 flood, the VEAP pre-68
group may be more skewed toward the newer vehicles. Lower air temperatures
Possible re-
duction at idle
Vehicle
distribution used
CO
HC
35% 12%
33% 12%
R. L. Polk
GCA Report^
13
-------
TABLE 2
VEAP DATA SUMMARY
% Drop
Sample
Number
Vehic.
Tested
Before Adjustment
Avg. % CO Avg.
Idle 2500 Idle
ppm HC*
2500
Number
Vehic.
After Adjustment
Avq. % CO Avg. ppm HC
idle Idle
in % CO
of Vehic
Adjusted
All Vehicles Tested
631
3.4
1.3
350
220
258
2.0
320
38.9
Gasoline Vehicles
599
3.5
1.3
350
230
243
2.1
320
38.2
Diesel Vehicles
10
0.1
0.4
Propane Vehicles
22
2.4
0.2
650
80
15
0.8
670
64.5
All Domestic Vehicles
564
3.4
1.2
360
230
239
2.0
330
40.4
All Foreign Vehicles
67
3.2
1.7
250
150
19
2.6
210
24.6
All Fleet Vehicles
196
2.9
1.0
250
150
70
1.4
270
42.2
Domestic Non-Fleet Vehicles
369
3.7
1.3
420
270
170
2.2
350
39.7
Pre-1968 Domestic Gasoline
113
4.5
2.1
560
340
49
3.2
460
31.4
1968-69 Domestic Gasoline
141
4.2
1.5
420
340
62
2.3
400
38.4
1970-73 Domestic Gasoline
266
2.7
0.8
250
130
105
1.4
240
46.7
GSA Fleet Vehicles
74
3.2
1.4
300
210
31
1.7
220
43.1
State Highway Fleet Vehicles
61
3.0
1.0
210
140
25
1.5
300
58.1
MUS Fleet Vehicles
43
2.5
0.9
200
100
NO ADJUSTMENT
* As Hexane, except for Diesel and Propane Fueled Vehicles.
-------
VEAP N0N-FLEE1 VEHICLES
20
GCA REPORT
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AGE OF VEHICLE IN YEARS
AGE DISTRIBUTION COfVSPARiSON CURVE
FIGURE 5
-------
in Alaska may be another reason for the lean mixtures. Carburetors are volu-
metric devices which will pass about the same volume, but more mass, at lower
temperatures (higher air mass per unit volume at lower temperatures) thus in-
creasing the A/F.
The 68-69 model year data are about comparable (a little richer) to the
Atlantic Richfield Company's (1971) data. Some 68-69 models had limited air
preheat in the carburetor air scoop which heats the combustion air effectively
lowering A/F. At 2500 RPM (Figure 8) both the pre-68 and the 68-69 models
were leaner than those in the Atlantic Richfield Company's 1971 study. Ap-
parently at the higher air intake velocities, the air preheat (on 68-69 models)
was insufficient to keep the mixture rich (less air mass).
The VEAP study included 1970 to 1973 model vehicles which prevented direct
compairson with the 1971 Atlantic Richfield study. The effect of temperature
upon air-to-fuel ratios (leanness) is almost negated for a warmed-up 1970 or
newer engine because there is a more positive control of combustion air temu
perature (~190°F) in the air filter assembly. In the 75% population at idle
for 1973s (VEAP 1973), the CO concentration was 2% (Figure 7) while it was ap-
proximately 4% for 1971s (Atlantic Richfield Company study, Figure 1 of Refer-
ence 8). For the same age (73s in 1973 and 71s in 1971), the 73s were putting
out one half as much CO as were the 71s. In the VEAP study approximately 40£
of the 73s and none of the 71s were fitted with pollution control devices commonly
known as air pumps which may account for the reduced CO emission from the 73s.
A more detailed discussion of these devices is presented in Part III, however,
some discussion is presented at this point to more clearly analyze the VEAP data.
The air pump system injects fresh air behind each engine exhaust valve.
Injected air at this point causes unburned hydrocarbons and CO to burn in the
exhaust manifold instead of passing to the atmosphere through the exhaust system.
16
-------
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VEHICLES
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20
/EHICLES 71 STUDY
VEHICLES 71 STUDY
CO 68-69
£0 PRE-68
CARBON MONOXIDE (%)
CO EMISSIONS vs POPULATION @ IDLE
FIGURE 6
17
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FIGURE 8
19
-------
Gases from the air pumps also tend to dilute the exhaust contaminants. There-
fore, to compare vehic.les with and without air pumps, one must convert to a
common dilution value. Zero percent oxygen (-no dilution) was selected. For
the 73s with air pumps, the idle and 2500 RPM CO levels were 0.7 -0.1% and
0.14 *0.05%. Without air pumps, the respective levels were 2.0 -0.1% CO (1
*0.1% CO after adjustment) and 0.33 *0.05% CO. The injected air oxidized (con-
verted to CO2) 1.3% and 0.2% CO at idle and 2500 RPM, respectively. An after-
adjustment comparison cannot be made since no 1973 air pump vehicles were ad-
justed.
F. Direct Comparison of Emissions
Here direct comparisons are made between the different engine types used
in the vehicles tested. Some conclusions are drawn relating to the desirability
of one type over another, based on the emission levels recorded in this study.
1. Gasoline fueled engines vs. Propane fueled engines.
The idle CO emissions for the propane fueled vehicles before ad-
justment was slightly lower than the gasoline fueled 1970-1973s, 2.4%
vs. 2.7% respectively. Most of the propane engines were comparable to
the gasoline "engines; that is, typical eight-cylinder engines of do-
mestic manufacture with idle speeds of approximately 550 RPM. However,
at 2500 RPM, the propane engines produced only about 1/3 as much CO as
the gasoline engines. To further assess this considerably more desir-
able CO emission characteristic, it would be necessary to make further
comparisons with the engfnes under load and transient operation. Unfor-
tunately such comparisons were beyond the scope of this project.
At idle, the only propane vehicles adjusted were those of the Yel-
low Cab fleet. The propane carburetor manufacturer recommended an idle
20
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mixture setting which would produce an exhaust CO concentration
of 0.25 to 1.0%. The propane suppliers representative therefore
set the vehicles to produce about 0.7% CO concentration. On the
day this was done, the outside air temperature was approximately
-20°F. After adjustment, the propane vehicles appeared very favor-
ably compared to the gasoline vehicles.
Idle CO Avg. after Adjustment
69-72 Propane 0.8%
70-73 Gasoline 1.4%
However, within a week after the adjustments were made, the fleet
mechanic indicated that the engines were misfiring at idle, and
' he had readjusted them to an emission setting of 3.0% CO. No fol-
low up was possible on these vehicles to determine the CO at the
time of the misfiring or whether the misfire was due to "too lean"
operation.
Propane is widely reputed to be :a clean burning fuel and is
advertised as such. However, on the basis of the VEAP study, no
clear evidence was revealed which showed propane to be generally
more favorable than gasoline from an idle emission standpoint. To
solve this question, a much more detailed field testing program in
a Fairbanks or similar climate is necessary. Propane does show a
slightly unfavorable ice fog characteristic, which is detailed in
Part III.
2. Foreign vs. Domestic Manufacture.
In the previous discussion, it was sufficient to compare CO e-
mission on a percent basis since the engines were of equal displace
ment. But when comparing small displacement foreign engines to the
21
-------
larger displacement engines of U.S. manufacturer, it becomes neces-
sary to use a mass or volumetric comparison. A good approximation
to obtain the amount of CO emitted is as follows.
Intake manifold vacuum in (atm) x
engine displacement in (liters) x
RDM _1
engine speed -y-(min ) x
CO concentration (%) = CO (1 lv^-S) at 1 atm.
mm
assuming: moles of combustables = moles combustion products;
moles of fuel are insignificant compared to the moles
of air; 100% volumetric efficiency.
In making comparisons of the VEAP data, average engine displace-
ments are used with the assumption that:
U.S. mfg. average displacement = 300 cu. in. (4.9 liters)
Foreign mfg. average displacement = 1600 c.c. (1.6 liters)
Both engines operate at approximately 16-19" Hg manifold vacuum (17"
used) but the smaller foreign engines idle at approximately 900 RPM
compared to 550 RPM for the U.S. engines. Therefore, calculating the
relative emissions from the data summary for all foreign and domestic
vehicles at idle before adjustment yields:
C(3v}a|' ' ,
Foreign: (-^p-Atm) (1.6 lit. )(^r RPM)(3.2% CO) = 1000 CO.
Domestic: (^—-Atm)(4.9 1 it.)(^p RPM)(3.4% CO) = 200*0"4^- CO.
This comparison shows that as received the average foreign manufactured
vehicle emitted about 1/2 as much CO as the domestic vehicles at idle.
This, of course, is mainly due to the smaller engine size. The results
which were obtained in this study compare very well with the findings
12)
of the U.S. Public Health Servicev ' when in 1967 that organization re-
ported that CO levels from imported compact cars were only 46% as high
as emission levels produced by the standard size domestic vehicles.
22
-------
No after-adjustment comparison can accurately be made since
manufacturer CO emissions criteria were lacking for many foreign
vehicles.
3. Domestic Gasoline vs. Diesel vs. Propane.
Here the total volumetric CO emissions for the three engine
types are compared as received at idle. Using the same method as the
previous-comparison, the average diesel powered passenger car had an
average displacement of 2.1 liters and idled at 600-700 RPM with
negligible manifold vacuum. Thus:
Diesel: (1 Atm)(2.1 liters)RPM)(0.1% CO) = 7o'^-CO.
c mm
1970-1973 Domestic Gasoline:
(^p^-Atm)(4.9 lit.)(^ RPM)(2.7% CO) = 1600 ^ CO.
Propane: (^-7Atm)(4.9 lit.)(^ RPM)(2.4% CO) = CO.
As received at idle, the propane and diesel emitted 88% and 4%, re-
spectively, as much CO as the 1970-73 domestic gasoline engines.
For low CO emissions at idle, there is no contest—the diesels are
definitely superior. ¦ Even after adjustment, the spark ignition engines
cannot compete with the diesel at idle. This statement should not be
taken to mean that if all of the vehicles were converted to diesel the
Fairbanks air pollution problem would disappear. For diesels, CO emis-
sions do increase at higher speed, as is seen in Table 2. Also, diesels
can be relatively high emitters with respect to the heavier HC and al-
dehydes (smoke and odor). The levels of HC and aldehydes at present
are not very high in the Fairbanks area, but,a total vehicle population
of diesels possible could result in an increase of these levels. The
most conclusive statement which can be drawn from this comparison is:
if a significant amount of the Fairbanks vehicle population was diesel
23
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powered, a proportional drop in ambient CO levels would be experienced.
However, a careful study would be required to find the limits of diesel
population which could be tolerated without dangerously increasing other
forms of air pollution. Ice fog emission comparisons are made in Part III.
G. Emission Testing Cycle
As the previous sections indicate, the VEAP study and the analysis of the
data were mainly concerned with CO emissions at idle. Since the highest ambient
CO levels occur in winter in the Fairbanks area when driving conditions are
difficult and traffic is moving slowly, idle emissions are very significant.
But CO emissions at idle contribute only part of the total ambient CO produced
by motor vehicles in the"city. While the percentage contribution at idle is ex-
pected to.be considerable, to date no sophisticated attempt has been made to.
accurately obtain this information.
The present method for making a total•evaluation.of vehicle emissions is
by the use'of a driving cycle. a driving cycle is basically the average
automobile trip. It consists- of: startup, idle, acceleration, deceleration,
and cruise at different rates. ¦ There are several established cycles, ,EPA> CVS-1
and CVS-3, HEW cycle, and the California cycle. All differ slightly but most
are applicable for driving conditions in the "lower 48." In cycle testing, emis-
sions are measured for each of the driving modes and an overall- average emission
is obtained. Unfortunately, noneof these cycles would apply to the winter
driving conditions experienced in Fairbanks. For example, the CVS cycle begins
with startup of a vehicle that has been left standing for 12 hours at +60 to
+86°F. After idling for 20 seconds, the vehicle is driven on a dynamometer, to
simulate a typical trip in which periods of cruising at speeds about 50 mph are
experienced. In comparison, a typical winter driving cycle in Fairbanks might
well begin with a vehicle being started without-preheat after it has stood for
24
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12 hours at -10°F. After 2 to 15 minutes of idle, it is then driven in traf-
fic where the maximum speed reached is 30 to 40 mph and averages about 10 to
20 mph. Of course, this is speculation based on the authors' experience.
However, the point is simply this: before any firm statements are made re-
lating to the total levels of vehicle produced CO emissions in the Fairbanks
area, a typical Fairbanks cycle must be established and vehicles must be
evaluated. The VEAP Program has only been a beginning and does not include
such total emission considerations.
25
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III. EMISSION CONTROL METHODS
A. General
In this section, a variety of CO control techniques are considered as they
relate specifically to climates similar to that found in Fairbanks. The tech-
niques discussed cover a wide range of possibilities. Some are well established
methods well proven with long histories of adequate service; some are in the ex-
perimental stages of development while others are theoretically attractive but'
have not been proven to be feasible, even in the experimental stage. It is im-
portant to remember that CO is produced-as a result of poor combustion efficiency.
The internal combustion engine, by its very nature, is a thermodynamic energy con-
verter which attains a relatively high termal efficiency at the expense of com-
bustion efficiency in normal application. In other words, there are practical
limits to which CO emissions from existing motor vehicles can be reduced in any
environment. It would be the logical conclusion of a comprehensive research ef-
fort to establish such limits for cold regions. This report does not go that far;
rather it only discusses briefly the methods which must be much more painstakingly
considered if such limits are to tie defined.
As noted earlier, CO emissions from internal combustion engines arebasic-
ally an excess fuel problem; i.e., too rich A/F mixture. The solution is,.of
course, to add extra air (oxygen, 0^) to burn the CO. The air can be added through
leaner carburetion or injected into the exhaust system where the CO ca-n burn out-
side of the cylinder before it can be emitted to the ambient air. Operation with
a rich A/F mixture and air injection to allow burning of the CO in the exhaust
system gets around the lean mixture operation problem but uses fuel to heat the
exhaust system rather than powering the vehicle. The two major exhaust treatment
systems which thus far appear to be the most promising are catalytic converters
and air injection systems.
26
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B. Air Injection System (Air Pumps)
The air injection system which is in routine use is commonly known as
the air pump. With the air pump system, the exhaust port and manifold acts
as a thermal reactor or combustion chamber to burn CO and HC. The air pump,
which is about the size of the alternator, is located near the front of the
engine and is.powered by a fan belt. It pumps (injects) fresh air behind
each engine exhaust valve. Injected air at this point causes unburned hydror
carbons ..and CO to burn in the exhaust manifold because of the high gas tem-
perature instead of passing to the atmosphere through the exhaust system.
Exhaust gas.,temperatures, downstream of the manifold are too low for ef.f-i c.i.en.t
CO oxidation (to..^) without the use of'a catalyst to speed up the reaction.
The air injection rate is about 20-30% of the carburetor air flow.
Air pumps were part of the emission controls installed in 1966-67 on
California manufactured Ford, GM, and AMC vehicles. - Some newer models viere.
also equipped. Approximately 4-5% of the pre-68 and post-69 and 10% of the
68-69 VEAP vehicles had air pumps. Air pump performance at idle on a 1968
six cylinder GM'engine is shown in Figure 9, a plot of percentage CO with.and.
without air pumps vs. number of turns, of the idle mixture screw. For both
curves the CO. values have been corrected to 0% O2 to account (correct) for
exhaust, dilution caus-ed by the air pump. Larger, insulated exhaust •manifold(s)
. (thermal reactors) should perform more efficiently than the.units presently
in use.
Lower ambient air temperature (say -40°F) should have little effect upon
air pump system performance. VEAP data tend to confirm.this. For example,
assume 1000°F exhaust temperature before mixing (air injection). Mixture
temperature will be 1.0(1000) '+ 0.25(-40) = 790°F. Theoretical mixture temper^
1.25
ature for Figure 9 was 800*°F. Combustion of the CO and HC will raise that
27
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WITHOUT AIR PUMP
WITH AIR PUMP
3
2
4
TURNS OF IDLE MIX SCREW
CO EMISSIONS VS TURNS OF IDLE MIX SCREW
FOR A GM 250 6-CYL 1968 VEHICLE
CO VALUES ARE CORRECTED TO 0 % 02
FIGURE 9
28
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temperature by 50° to 400°F. During deceleration, the air pump's output is
dumped into the atmosphere to prevent backfiring of the very rich mixture at
the exhaust port. New (1973) GM vehicles can be ordered with air pumps for
less than $20 For retrofit purposes, the U.S. EPA^^ reported instal-
lation costs of approximately $375 and that no developers were interested in
retrofit application. Addition of an air pump to a vehicle should not greatly
affect a-mass ilce fog emission. However, some additional water vapor wiTT sbe~
produced as :a.result of more complete combustion of HC. There is a slight
penalty in gas .mileage and an increase in^ exhaust volume (apparent ice
fog-volume) .by about 25%. Apparent ice fog is a term which refers to the in-
creased plume..volume which is visible at the tail pipe which would, tend to
increase the hazard of following.a vehicle during an ice fog episode.
Air pumps do seem to be ideally suited for use in cold climates to help
reduce CO emissions mainly because of their good service record and low main-
tenance requirements as well as their relative insensitivity to carburetor
maladjustment. Their, increase in apparent ice fog, however, could prove to
be a very significant factor in their acceptability.
C. Catalytic Converters
Catalytic converters have been in use for many years to reduce the CO
emission of interna! combustion engines which operate indoors" i.e., lift
trucks and mining machinery. , Very good results have been obtained in these
applications especially with propane fueled engines. They are, however, re-
latively new to the auto industry when being considered for general use. While
they are commercially-available for automobiles, they have seen only limited7
use in the lower 48 states. To the knowledge of the authors, no record of
their performance ir> cold regions is available.
29
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The catalytic converter is usually a canister containing an oxidizing
catalyst, which is mounted integrally within a vehicle's exhaust system. The
converter is smaller than a muffler and is usually mounted next to the
exhaust manifold for heat conservation. The catalyst, which may be a noble
metal, speeds the oxidation of HC and CO and allows it to occur at temper-
RT
atures lower than with air pumps. For example, a portable "Coleman "
catalytic (platinum-asbestos) heater cperates en the catalytic converter
principle.
Catalyti'c* converters".wfTT* theoretically require an air pump if a vehicle-^'
carburetor can be adjusted "to-give an A/F richer than 14.3. However, from the-
present testing b'eing carried out by the California State Air Resources Control
Board, it appeared that as a practical matter some form of air injection is ¦
required in all cases for the most efficient operation.
The cataTys f'wQst.reach a ¦.certain acti'vatiM""temperature -before significant
conversion (50% of the CO to CO,,) can take place. With usage and deteri-
oration, that temperature can increase, allowing fexcessive emissions during
low temperature operation.
In climates such -as those found-in Fairbanks, two potential problems with,
catalytic converter operation can be expected:
1. Actmtion temperature:
During cold weather startup it may take a considerable length-
of time for'the catalyst bed to reach activation temperature. If
this time should prove excessive, the value of the device to reduce
CO will ¦'"be minimi 2ed since CO will be "emitted throughout the catalyst
warm up-period* This¦ profe-Tern -could perfsaps be solved by preneati'Tig
the catalyst with an electric resistance heater before cold start up.
30
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library
U.S. Environmental Protection flganCf
Corvallis Environmental Research Lab.
200 S.W 35th Street
Corvsllis. Groaon 97330
2. Catalyst overheat:
The second potential problem occurs after the catalyst acti-
vation temperature has been reached during a cold start situation.
Duei to the relatively small thermal mass of the catalyst as com-ma*s or ine
pared with, the engine block and manifolds, activation temperature
can be expected to be reached long before the carburetor choke
has opened. This would result i.n; extremely high exhaust concen-
tration.of combustables (CO and HC). Oxidation of -these unusually
•hi-gb -concentrations wi th-in -the: '-catalytic, converter! ^could-result wr.
temperatures high enough to destroy the catalyst- It is possible
that this problem could be overcome by use of special chokes and'
intake manifold quick heating devices.
Another more general .restriction associated with catalytic converters!
is that not all fuels are acceptable for use. Lead and phosphorus compounds
in gasoline,, for example, may tend to poison the catalyst (destroy catalytic
activity). Lower-48 retrofit installation costs for catalytic converters
were estimated (1972) to cost from $143 to $175.^^ There is no cost esti-
mate available for Alaska. Addition of a catalytic converter to a vehicle
should- affect ice fog emissions in a manner similar to the.air pump-.
In sunmary, regarding the catalytic converter as an emission control de^
vice for:CQld.climates; there is insufficient -information a-t this time to make
any conclusive statements.
D. Lean Mixture Operation
There is,-of course, another more basic method to reduce CO emission.
This is through lean air/fuel carburetion. This method is -discussed, to some
extent in Section II and will be elaborated upon here.
31
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The major advantage of lean mixture operation for CO control is that
more of the CO and HC is used to increase mileage rather than exhaust tem-
perature as with exhaust treatment devices. Lean mixture means an A/F
greater than or equal to 14. Most of the post-1970 models were designed to ;
run with lean mixture carburetors.
To obtain lean mixture operation without one of the newer carburetors,
a method called" intake manifold air bleed can be considered. In this
system air ;for combustion is injected below the carburetor. An air control
valve is used which increases the A/F by metering air to the intake manifold
in response to manifold vacuum. This system would be applicable only as- a
retrofit item on pre-1968 vehicles. Again, however, as with other control
devices, cold climate consideration must be made. At low temperature, as
seen in Part II (Figures 6 and 7) pre-68 vehicles without intake air preheat
tend to run leaner-than those found in the Lower 48. If this is in fact due
to the increased air densities occurring at low temperature, the air bleed-
system could result in overly lean mixtures during winter months. This will
tend to cause reduced drivability, an increase in HC emissions and perhaps
valve burning as a result of the higher cylinder head temperatures; Such de-
vices- at" this "Time exist only in the experimental stage. To the-knowledge-
of the authors no certified air bleed to intake manifold systems are commer-
cially available.
In the Fairbanks area gasoline fueled vehicles could run leaner if.lean
misfire could be eliminated. Misfiring due to lack of sufficient fuel vapori-
zation caused by cold intake manifolds can be corrected by one of two methods:
(1) adjust (ream out) carburetor jets to give a richer mixture; i.e., lower
A/F or (2) insulate intake manifold and heat if necessary to provide more fuel
vaporization. (See warm HC curve, Figure 2) The latter method is preferred since
32
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it is less costly; it will provide better mileage, reduce CO emissions, and
prevent carbon coating of plugs and head(s). On some "hot" engines (crowded
under hood volume) the insulation may have to be removed for summer use. On
inline engines-(where -the-manifolds hang on the
-------
Table 3
MAJOR CO CONTROL SUMMARY COMPARISON
(13)(16)09)
% CO Reduction
Instal led .Cost
Retrofit
with new vehicle
Expected life miles
Expected supplies
cost/miles
Special fuel
Fuel Economy
Temperature Sensitivity
Ice Fog
Other Considerations
Lean Mixture
50±
$20-70
Std. Equip.
Same as engine
< $10
50,000
None.
Increased
Warm intake
-manifold may
be required.
Decrease
Dieseling
and valve
burning with
improper ad-
justment.
Air Pump
Up to 50-**
$200-400
$20 (GM)
Same as engine
< $10
50,000
None,
Slight
Decrease
None
Catalytic
Converter
60-
$150-200
> $20 ?
50,000-
Increase
In common
use since
1966.
$20 * (catalyst)
25,000
Non-lead
Slight
Decrease
Has to be above
activation temper-
ature but below
fusion temperature..
Increase
Not in common
automotive use.
(13)
* Compared to vehicle without that respective control method^
** For pre-1970 .models
34
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F. Inspection and Maintenance Programs
Many of the newer vehicles have emission control devices which upon
malfunction cause higher emission levels than on similar (earlier manufacture)
vehicles without the devices. For example, a plugged PCV valve could more
than double the idle CO emission.
Gaseous fuel carburetors are designed to operate at a high A/F ratio,
to reduce CO emission. But, as shown before, they could easily be maladjusted
to triple the idle CO emissions.
To insure efficient pollution control device operation, an emissions in-
spection program is necessary. Such a program combined with mandatory repair
would detect and correct the harmful emission producing malfunctions. The
New Jersey Department of Environmental Protection instituted an inspection
(12)
(at idle) program in 1972 and has arrived at the following conclusions.
1. With proper training and equipment, the automotive service industry
can tune vehicles for low emissions at reasonable cost.
2. Periodic vehicle emission inspections and maintenance can significantly
reduce CO emissions in urban areas.
Excessive CO emission is caused by too l.ow,..an Air/F.uel ratio (A/F) which
is basically a carburetion problem. Rebuilding faulty carburetors will not
necessarily solve the problem. In rebuilding, pietering rods, jets, and springs
are not always replaced. In any inspection and maintenance (I & M) program,
bench flow testing (for correct A/F) would be requisite for all replacement
(rebuilt) carburetors, followed by proper adjustment once installed.
G. Fuel Volatility
Winter gasolines that are more volatile will allow leaner mixture surge-
free operation. Propane or natural gas, for example, are extremely volatile,
allowing surge-free operation at an A/F of 14.5 or more.
35
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The winter gasolines sold in the Fairbanks area are the same as those
supplied in the northern tier of the Lower 48 states. Blending propane or
butane with gasoline will increase its volatility but might also increase
vaporTlocking tendencies. Depending upon relative amounts of propane or
butane and gasoline, the mixture will begin to boil (Vapor Pressure ^14.7
psia) at -45°F for 100% propane to +100°F for 100% gasoline; therefore, en-
riched gasoline (.it! a .conventional gas tank) cannot be stored in a heated
garage. Proper blending.and usage is required to reduce.the combustion and
container explosion hazard.
H. Cold Start
One cold start to warmup a vehicle may emit much more CO than several
/14 \
minutes of warm idling. Wendell, et al.v ' have stated:
"Unfortunately-, the effectiveness of proposed emission con-
trol devices to reduce emissions from vehicles is not as effective
on cold start emissions as on emissions from automobiles at normal
running temperature. Thus, cold emissions from post-1974 cars will
become increasingly significant. In -particular, 90% of the CO and.
80% of the HC will be emitted during the first 2 minutes."
[of the Federal CVS cycle]
Cold start emission levels are expected to last for more than two min-
utes during sub-arctic driving conditions. To get sufficient fuel vapor for
combustion with a cold intake manifold,, a vehicle.must be choked to a very
rich mixture; A/F down to 1 in some cases. At low temperatures, an A/F
(liquid) ratio of 1 to 1 may be required to.get an Air to Vapor (fuel) ratio,
of, say, 10 to 1.
Cold start emission levels could be greatly reduced if the intake mani-
fold were heated to- normal operating temperature before or immediately after
starting. General Motors Co. (GM)^^ is developing a quick-heat manifold
36
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early fuel evaporation (EFE) device which is coupled with a rapid release
choke. GM has reported that this system has eliminated up to 90% of the
CO produced during the cold starting of 1972 engines [1972 HEW schedule,
first cycle].
Gold start emissions need to be more quantitatively defined for cold
climate regions. A present practical alternative (to cold starts) would be*
to electrica'l ly; heat the intake-manifold before starting'. If the'manifold
..were.. warm .enoughthere, would, be little, need, of a.choke,, for, starting an,
:.30.therwjise^G0'ld-.v.ehncle^ tlm, cold leMmatesv, electric, heaters are routinely
used"torireat -engine "b'locks" 'before- starting. rTtiese electri c* antifreeze" heaters-
supply some heat to the intake .mani*fold»,. especial ly on engines where, the
manifold.. sits between the.heads. . .Insulating the manifold would.raise.its
temperature,-anti:'require;.less electrici ty for easier: starts.
Circulating (tank type) heaters are-more susceptible to circulation re^
sir-iction.than are. direct immersion, heaters. In use,. ethylene glycol-water;
(50-50 ±o:60-:40T solutions. tend'-to..sludge" out (ice. formation)* at temperatures:,
below -40°F. Sometimes this sludge will plug the ty4" I.D. suction line to
tank type -'heaters. In-bTock (immersion-) heaters do not have the low tempers
atu-re^iroula^ton-probleni. Therefore, --they' should be. more reliable.< ifropyw
1 ene:.g:ly col-rwater. solutions should have a much lower sludging temperature;
I. Fuel Economy
Bestdes-ipeduc-ing^ -CO; 1 evel s in the .Fairbanks; area,. an I &• M program woui-ld
save the operator of a "high emitter" considerable cost in. terms:of;fuel.-ex:-:,
penses if'he we're'required' to reduce his vehicle's. CO" emission. For example-,
consider- a..J.ate model vehicle that, is- emitting. 6% CO. (many VEAP vehicles, were,
higher) atboth idle and high speed. Referring to Fig. 4, that would mean
that he was operating at an A/F of 12/1. A late model vehicle should easily
37
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operate at a CO level of IX for an A/F of 14/1. Calculating:
A/F = 12/1, as 1# of fuel is used for every 12+1=13#
Air + Fuel, or F/A+F = 1/13.
Likewise, for A/F = 14/1, F/A+F = 1/15#.
Converting the A/F =12/1 to an (A + F) = 15# basis,
1 15/13 _ 1.15 #F
13 15/13 " 15 WTA+T) *
0 15
Therefore, adjusting a vehicle from 6% to 1% CO will save yyg- x 100 =
13% in fuel costs under steady state driving conditions. For the owner of
one high emitter who spends $10/week for gasoline, this should save him about
$68 per year which should more than pay for the adjustment. The annual sav-
ing would be over $100 for a vehicle that was adjusted down from 8% to 1% CO.
The increased mileage comes from burning the CO .and HC that would be present
in the exhaust at the lower A/F.
J. Ice Fog
Ice fog generated by motor vehicles is of course the result of combustion
(3)
produced water vapor emissions. According to Benson; ' automobiles are a mi-
nor contributor to the total ice fog in the Fairbanks area. On an overall
basis, this may be true. But it is the vehicle-produced ice fog which lingers-
above road surfaces, blocks visibility of traffic signals, other vehicles and
pedestrians and,-in general, creates the extremely hazardous driving conditions
which are the main objections to ice fog.
Newer vehicles, due to poorer fuel economy, emit more water vapor resulting
in more ice fog than older vehicles. For example, a vehicle that gets 10 miles
per gallon puts out about twice as much (mass and volume) water vapor as a
vehicle that gets 20 miles per gallon.
38
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If the exhaust gas water vapor were condensed out (by means of a heat
exchanger) before exiting, there would be negligible water vapor, hence no
ice-fog, emission from vehicles. However, to date, no practical equipment
has been developed to do this effectively.
After making a few basic assumptions, one'can estimate the ice fog
(H^O)" emissions from-different'fuels used in internal combustion engines.
The fuels are dieseV (fuel- oil), gasoline, and propane.
Assumptions:)• (;1): •sZ&'mil.e&>p.errgal-lon..for a 2 litersdiese.l- passenger. >
vehicle.
:(;2) ^switching from-fuel oil to'gasoline-.or propane,
in equal weight vehicles, the motive energy re-
quirement .(Btu/mile) will be 'unchanged.
Surni'iier^ftWt'at^d3^ha.t, in .general, xtieseJ .engines are -371.and. autonmtiveirgas?
oline engines are 25% thermally-efficient. The compression ratio is not
changed by converting from gasoline to propane; therefore,. 25% efficiency.will,
be used with propane.
The heating, value of most, hydrocarbons (fuel oi.l, gasoline, and propane-)
¦i s^aboat^the Tsame ' ('20;000 ;Btu/Tb rh' therefore> "tHe i r mi 1 eage per pound- of-fuel'
wi^-be;propo^tiona-l :to' eff i~ctewetes-• and* w*l 1 • be the» same 'for"-ga-sol4-ne
-propane. -The^denstti-es; .of fuel, oi 1-, -gasoline>: and propane: are .6.5 an.d
4.2 pounds per gallon respectively.
Using -26 mile/gal. diesel yields:
(26) || = 15.8 mile/gallon or
15.8/6.1 = 2.59 mile/pound of gasoline.
Propane would then yield:
2.59(4.2) = 10.9 mile/gallon.
39
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Union Oil Company of California and API data lists arctic fuel oil as 13.7
(19)
weight % hydrogen. Heneirr ' states a carbon to hydrogen mass ratio of
6:1 to 6.8:1 for commercial gasoline. A ratio of 6.5:1, which is 13-.3 weight
% hydrogen will be used-; Propane is 18 weight % hydrogen/
In all the fuels, hydrogen is assumed to burn completely forming nine
pounds of water per pound of hydrogen.
After calculating the water emission from combustion (pounds H^O per
gallon» of^fueU) the1 i'ce-fog-emission based' on miTeage ca?h be, .tabulated ^asl
in Table 4.
Table 4
ICE FOG (ti20)- EMISSION.BASED ON MILEAGE
Fuel Mileage Emissions
mi/gal
mi/lb,fuel
Ib.f^O/gaT
Ib.^O/mi
Diesel (fuel oil)
26
8.3
0.32
Gasoline
16
2.9
7.3
0.46
Propane
11
2.9
6.9
0.63
Diesel»-=:(fueT otl^.
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CO controls would reduce vehicle-produced ice fog, while others would in-
crease it. The important point is that in advocating any one pollution
control system over another, caution should be exercised to insure that
levels of other forms of pollution are not undulynincreased.
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IV. SUMMARY
Perhaps it can be said that this report has raised more questions than
it has answered. Well it might, for as is usually the case when one tries
to become educated in a complex subject, the initial conclusion is that to
do a proper job, further education is needed. This report has considered in
broad terms the problems associated with the control of vehicle produced CO
and, to some extent, ice fog in regions with cold climates. This area has
shown itself to be complex.
Basically, the approach has been to evaluate the emissions of vehicles=as
they exist in the Fairbanks area and find out what can be done to lower emis-
sions by simple adjustments. Then from the data obtained, differences in
vehicles were assessed from an emissions control standpoint. However, when
this was attempted, the conclusions were found to be weak because of a lack
of necessary information. Next, systems and methods to further reduce existing
emissions were considered, but again, the lack of practical field evaluated
information forestalled the desired, firm conclusions. What;then has.this.,
report accomplished?
This report has outlined the problems faced in cold-regions-vehicle-emis-
sion7 tbntro'l , surveyed the problem on the most practical level,- and pointed to-
ways in which the problem might be solved.
It remains to be seen, of course, exactly how the technological, socials
and economic problems will be solved. But research must continue if we are
to live in an acceptable environment with our existing vehicles, while we wait
for industry to develop cleaner running equipment.
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V. CONCLUSIONS AND RECOMMENDATIONS
1) As received at idle, the propane fueled vehicles tested emitted 88%
and diesel vehicles emitted 4% as much carbon monoxide as the average
(300 cu.iini-;V<8i)-domestic gasoline fueled;vehicle.
2) As received at idle, the average foreign manufactured vehicle emit-
ted about Inasmuch CO as the .average domestic.vehicle. Thisis^
due-to the smailer engines used in-foreign vehicles.
3) Proper adjustment-of the carburetor idle mixture screw.produced;.^-,
44%'reduC'tion-iin^CO^ emiss-ions- at'' id!esfor the^M634.o.s 1973. domestic;?
vehicl es "tested.
4) If "all of the motor vehicles in the Fairbanks area were adjusted for
leaner idle operation without requiring high emitters.to have, major:
ceng4
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8) Most of the pollution control equipment and methods presently in
standard use on motor vehicles are helpful in reducing CO emissions
in cold climates." However, they are not always as effective as
they would -bevin 'warmer climates. In addition,-, some of the low
CO emission devices and engine types such as air pumps and propane
fuel tend'-to increase the production of real and apparent ice
fog.* These trade-offs must be kept in perspective when advocating
any- one ¦ GO -contrti"Pcmethod.
9) •Di'ese1^|fevliefed^e^fd?esuar'e':T,oWx'eiiiit4'er-s "Of both CO-and ice..fog; but'
may be relatively high in heavy HC and aldehydes which are not pre-
sently at problem levels' in the Fairbanks" area.
10) There -is -a severeHack-of -information availab-le -rela-t-ing -to the .pperv-
^tfd'n^'and^control 3of^emis;si'on^from''motor'-vehi-clesr in•.eo.M.^ijriate.sv
while the background research necessary to make sound knowledgeable
decisions relating to vehicle emissions control in more temperate
zones vs-extensive.
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VI. RESEARCH NEEDS
This report raises questions about arctic effectiveness of proposed con-
ventional auto emission control devices and suggests alternate techniques
which may reduce pollution while providing better dri veab.il,ity. Concen-
trated investigation in the following areas is necessary to provide rational,
effective and economic criteria for controlling automotive emissions in
cold climates.
1^ A cold regions vehicle emission test cycle must be developed which would
be r.epr.esen.tati v.e of urban driving, hab.i.ts under arctic .winter conditions
to properly assess the. to.tal- emissions .of. a. v.ehicle, at -idle, under load,
and during acceleration and deceleration.
2) A thorough field evaluation of all existing vehicle emission control mea-
sures. mus.t. be. made, w.i.th. care.ful_,. quant.itative consideration given ..to. .the .
cause, and effect relationship between individual pollutant levels which .
might result when the level of one is changed. These tests should be
carried out-wsing the driving cycle of Item 1.
3) Studies are needed to develop.ajid test techniques, surh as heating intake
.mani-fo-tds.,.e.tc\,. wh-ich .ar.e. not, specifically.pollution control, methods..but;
which. would, .increase, the -.efficiency., of- .cold weather, vehicle operation and
thus aid in pollution control.
4) Fuel research .is necessary to develop blends more specifically adaptable,
to-cold-weather,,use.. . Optimum mixtures, of propane .or butane and gasoline
and the determination of safe handling procedures and carburetion re-
quirements might"well be part of such an effort.
5) Immediate attention should be paid to the development ofmethods to-control:
vehicle-produced water vapor which results in the extremely hazardous .pol-
lutant known as ice fog.
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Any future vehicles manufactured and distributed in cold regions by the
automotive industry should be thoroughly evaluated for both acceptable
emission levels and satisfactory operation in those regions. This is
most important to insure customer protection.
46
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VII. REFERENCES
1. National Academy of Engineering, "Effects of Chronic Exposure to Low
Levels of Carbon Monoxide on Human Health, Behavior, and Performance."
Washington, D.C., 1969.
2. U.S. HEW, PHS "Air Quality Criteria for Carbon Monoxide." AP-62, March
1970.
3. Benson, C.S., "Ice Fog: Low Temperature Air Pollution Defined with
Fairbanks, Alaska, as type locality", U.S. Army, Cold Regions Research
and Engineering Laboratory (CRR£L) Research Report 121 (1965).
4. State of Alaska, Air Quality Control Plan, Vol. 2, (Appendix), Depart-
ment of Environmental Conservation, 1972.
5. Voelz,- F;r., e't al\ , "Survey of Nationwide Automobile-Exhaust Emissions
and PCV Systems Conditions - Summer 1970", Atlantic Richfield Company,
Presented at National Combined Fuels and Lubricants,^Powerplant and
Truck Meetings, St. Louis, Mo., October 26-29, 1971.
6. Kruse, R.E., and D.M. Hill, "Exhaust Emissions from Compact Cars",
"National' Center- for AirPollution Control; PHS, USHEW, SAE Trans;v
Vol. 76, Paper 670688, (1967).
7. GCA Corp., (US EPA Report) Transportation Controls to Reduce Motor
Vehicle Emissions iri Fairbanks, Alaska. February, 1973.
8. Voelz, F.L., "Exhaust Emission Levels of In-Service Vehicles - Com-
parison of 1970 and 1971 Surveys", Presented at National Automobile
Engineering'Meetin'g,'Detroit, Mich., May 22-26, 1972. SAE Paper
720498, 12 pp.
9 Michael,.£,R., "Low Ambient Temperature Emission Testing, A Preliminary
Report"V EPA Testing anc Evaluation Branch, Ann ^rbor, Mich., Feb. 1973;
10. Personal communication, A1 G'ullon. May 14, 1973. Acting Chief, Mobi:le
Source Emission Division, Environmental Protection Service, Environment,
Canada.
11. New York, City of, Annual Report of the Bureau of Motor Vehicle Pollu-
tion Control, Department of Air Resources, "Emission Factors - The.Ef-
fects of lCold Temperature oh Exhaust Emissions". (Paragraph B-T of the"
Report and Table 54, "Cold Weather Tests").
1-2. Andreatch,:, A. J., • JiC. • Elston, and R.W. Lahey, "New Jersey REPAIR Project:
Tune-up at Idle", Journal of the Air Pollution Control Association, 21:
757-763, December 1971: i ~
13.. Control :Strategies for In-Use Vehicles, U.S. EPA, Office of Air and Hater
Programs, Mobile Source Pollution Control Program, Washington, D.C. 20460
November 1972.
47
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14. Wendell, R.E., J.E. Norco, and K.G. Croke, "Emission Prediction and
Control Strategy: Evaluation of Pollution from Transportation Systems",
Journal of the Air Pollution Control Association, 23:91-97, Feb. 1973.
15. Callahan, J.M., "GM's 'Hottest' Automotive Emission Elimination", Auto
Indust., 147:(4) 25=28, August 1972.
16. Personal communication, Fred Coleman, Fairbanks Chevrolet Dealer, May
14, 1973.
17. Horowitz, J., "Inspection and Maintenance for Reducing Automobile Emis-
sions, Effectiveness and Cost", Journal of the Air Pollution Control
Association, 23:273-276, April 1973.
18. U.S. EPA, "New Motor .Vehicles and New Motor Vehicle Engines", Federal
Register 37:24250-24320, November 1972.
19. Henein, N.A., and D.J. Patterson, Emission from Combustion Engines and
their Control, Ann Arbor, Ann Arbor Science Publishers Inc., June 1972.
355 pp.
20. Summers, C.M., "The Conversion of Energy", Scientific American, Vol.
224:(3), September 1971.
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