EPA-AA-IMS-81-24
Technical Report
Emission Effects of Inspection and Maintenance
at Cold Temperatures
Tom Darlington
Inspection and Maintenance Staff
Emission Control Technology Division
Office of Mobile Source Air Pollution Control
Office of Air, Noise, and Radiation
U.S. Environmental Protection Agency
Ann Arbor, Michigan

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Table of Contents
Page
1.0 INTRODUCTION & SUMMARY	4
2.0	BACKGROUND	6
2.1	General Causes of High CO Emissions at Low Temperatures	6
2.2	Primary Sources of CO Emissions	7
2.2.1	Choke Operation	7
2.2.2	Maladjustment of Idle Mixture	8
2.2.3	Heated Air Intake Systems	9
2.3	External Factors	9
2.4	Technology Which Reduces Cold Start Emissions	9
2.4.1	New Technology	9
2.4.2	Block Heaters	10
2.5	Inspection and Maintenance Programs	10
2.6	Notes on Test Procedures Used	11
3.0	TEST PROGRAM DESCRIPTION	12
3.1	I/M Effectiveness Test Sequence	12
3.2	Vehicles	13
3.3	Controlled Environment Test Cell	13
3.4	Maladjustments and Disablements	13
3.5	Other Notes on Test Procedures	14
4.0	RESULTS	15
4.1	Effects of Maladjustments on FTP Composite CO Emissions	15
4.2	Effects of Maladjustments on FTP Bag 1 CO Emissions	16
4.3	Effects of Maladjustments on Idle Warm-Up Plus
Bag 1 CO Emissions	16
4.4	Effects of Maladjustments on Idle Warm-Up Plus
Bag 1 and 2 CO Emissions	17
4.5	Effects of Idle Warm-Up Period on Trip CO Emissions	18
4.6	Effects of Maladjustments on Fuel Consumption	18
4.7	Four-Mode Idle Test Results	19
5.0	CONCLUSIONS	20
5.1	Differences in CO Reductions at 20°F and 50°F	20

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APPENDICES
Page
Appendix 1	Urban Dynamometer Driving Schedule	25
Appendix 2	Survey of Idle Warm-Up Times	26
Appendix 3	Test Vehicle Specifications	27
Appendix 4	Controlled Environment Test Cell Diagrams	28
Appendix 5	Individual Vehicle CO Emission Results	30
Appendix 6	Individual Vehicle Gas Mileage and
Fuel Consumption Results	32
Appendix 7	Four Mode Idle Test Results	33

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1.0 INTRODUCTION AND SUMMARY
This report discusses the potential effectiveness of Inspection and
Maintenance (I/M) programs at reducing CO emissions from vehicles operated at
cold temperatures. The EPA has extensively studied the effectiveness of I/M
at reducing emissions at 75° F, and has shown that I/M is capable of reducing
CO emissions on failed vehicles by about 50% at 75° F. At warm temperatures
maladjustment of idle mixture is the most common cause of high CO emissions.
At colder temperatures the operation of choke systems causes high CO
emissions. However, vehicles which have maladjusted idle mixture may emit
more CO in cold temperatures than vehicles without maladjusted idle mixture.
I/M would therefore be capable of producing some CO reductions from vehicles
operated in cold temperatures. This report centers on how much these
reductions might be.
We have concentrated our analysis on CO emission behavior because most CO
non-attainment areas have heightened CO air quality problems during the
winter. Although HC emissions from vehicles also increase substantially in
cold weather, most areas have little or no problem with ozone since the days
are short, the sun is often blocked by clouds, and temperatures are cold, all
of which inhibit the photochemical reactions which produce ozone. We have
also analyzed fuel consumption characteristics in cold temperatures.
Four vehicles were deliberately maladjusted and tuned up to simulate the
effects of an Inspection and Maintenance (I/M) program on vehicles needing
emission-related repairs. The results indicated that I/M has the potential
for reducing CO emissions from in-use vehicles operated at temperatures below
75°F. However, these results and conclusions should be viewed as preliminary
until the State of Alaska presents data on the effectiveness using in-use
vehicles. The table below shows CO reductions obtained from three of the four
vehicles which were tuned-up after receiving tests with idle mixture
maladjusted. One of the vehicles had a sealed idle mixture screw which we did
not maladjust. Vehicles received other maladjustments, which are discussed in
Sections 3 and 4. However, idle mixture is the most important maladjustment
and is the only maladjustment summarized.

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Table 1
CO Reductions Obtained in Going
From Maladjusted Idle Mixture Configuration
to Tuned-Up Configuration: Average of 3 Vehicles


g/mi,
. Reductions
% Reductions
Test Cycle
Distance
20 °F

o
o
20 °F
50 °F
FTP* Composite
7.5 miles
23.8
g/mi
25.1 g/mi
36%
52%
FTP Bag 1 Only
3.59
12.3

48.4
9%
35%
5 min. Idle Warm-Up +
3.59
40.2

47.1
30%
59%
FTP Bag 1






5 min. Idle Warm-Up +
7.5**
44.5

43.2
41%
57%
FTP Bag 1 + Bag 2
* The actual driving distance on the FTP is 11.1 miles. However, emissions
from the 11.1 mile trip are reweighted to reflect the average incidence of hot
and cold start trips during the day (57% and 43%, respectively), and an
average trip distance of 7.5 miles. In cold climates, these average
percentages of hot and cold starts may be different. See Appendix 1 for
further explanations of FTP terminology.
** Although this trip distance like that of the FTP is 7.5 miles, the emission
results have not been reweighted like the FTP to include any hot start trip
results.
The CO g/mi reductions in the table above are nearly the same at 20° as at 50°
for the FTP composite and 5 minute idle warm-up plus FTP Bag 1 + 2 test
cycles. However, for the shorter test cycles of the FTP Bag 1 and the 5
minute idle warm-up plus FTP Bag 1, the reductions at 20° are significantly
less than at 50°. We attribute this relationship to the hypothesis that
maladjusting idle mixture changes the air/fuel ratio less at 20° than at 50°
for the shorter test cycles, since during a short trip at 20° the carburetor
is very rich to begin with because of choke operation. Consequently, fixing
the maladjustment has less impact at 20° than at 50°F. This relationship has
been confirmed with fuel consumption data. For a detailed explanation of this
relationship, see Section 5.1.
The FTP composite CO reduction at 50° (52%) closely matches the 50% reduction
in CO emissions obtained from failed vehicles in the Portland, Oregon I/M
program. This suggests that our idle mixture maladjustment is typical of
in-use vehicles.
Revised 10/26/82

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2.0	BACKGROUND
The first part of the background section contains a conceptual discussion of
why CO emissions are high at cold temperatures. Next, the specific systems
which cause the high CO emissions (e.g., choke and idle mixture) are
discussed. External factors such as driving habits can also affect the amount
of CO produced, so this is discussed in Section 2.3. Lastly, we concentrate
on those things which show potential at reducing CO emissions at cold
temperatures: new technology on late model cars, block heaters, and I/M
programs.
2.1	General Causes of High CO Emissions at Cold Temperatures
Most vehicles even when properly maintained emit substantially more CO at cold
temperatures than they do at warm temperatures. There are several reasons for
this phenomenon. First, at low temperatures, engine starting requires-
carburetor choking because of the low volatility of gasoline at low
temperatures. Much of the gasoline entering the engine is in excess of
stoicheometry and exits the engine as CO. Second, low temperatures also
result in longer engine cranking times than would be experienced at warmer
temperatures. Like choking, long cranking times can add more low-volatility
fuel to the engine, resulting in more incompletely burned combustion
products. Third, the choke does not completely open up at the instant the
vehicle is started. Depending on what other choke controls are present on a
vehicle (electric assist, thermostatic coil, etc.) it may take several minutes
for the choke to completely open up. Fourth, internal friction in the drive
train and the power required to drive the accessories (heater, wipers) are
higher, requiring greater power output from the engine during warm-up.
Finally, during engine starting and warm-up the catalyst is cold and unable to
operate effectively. All of these factors contribute to high CO emissions in
the first few minutes of vehicle operation; in well-maintained cars they have
very little effect on CO emissions after vehicles are warmed-up.
On a more general level, there are many sources which may be identified as
causing high CO emissions in typically--rather than properly—maintained
vehicles at cold temperatures. Some of these sources are "naturally
occurring" sources (or design sources) which are, from an engineering
standpoint, absolutely essential to start an engine and keep it running
initially in cold weather. An example of a naturally occurring source in an
engine is the operation of the choke system described in the preceeding
paragraph. Operation of the choke system produces high CO emissions, but its
operation is necessary to get the engine started.
Other causes of high CO emissions in vehicles at cold temperatures are very
similar to the causes of high CO emissions in vehicles at warm temperatures
and can be grouped into a single heading: malmaintenance. Malmaintenance can
take the form of deliberate maladjustments such as maladjusted idle mixture
and choke controls, or can arise through owner neglect of timely maintenance.
Examples of this latter type of malmaintenance are plugged PCV valves and
dirty air cleaners.

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Still other potential sources o£ high CO emissions in vehicles at cold
temperatures are not really within the engine but are external to it, and
these are driving habits. For example, at cold temperatures, drivers are
likely to warm-up their vehicles at idle for a few minutes before embarking on
a trip. This may produce more CO emissions than if the vehicle is simply
started and driven in cold weather.
Each of these causes has an effect on the total trip CO emissions coming from
a vehicle which is operated at cold temperatures. A detailed analysis of each
cause is helpful in understanding how they affect total CO emissions.
2.2 Primary Sources of CO Emissions
2.2.1 Choke Operation
The choke system on most vehicles consists of a choke plate which rotates in
the top of the carburetor air horn, a set of linkages attached to the
accelerator pedal which control the initial choke plate setting, a choke
vacuum break system which opens the choke slightly once the engine is started
and an electric or thermostatic assisted choke coil which controls how fast
the choke system turns off (opens) from then on. When a vehicle is started in
cold weather, the choke plate is closed, creating a high vacuum in the
carburetor which draws more fuel into the engine. The choke vacuum break
works to open the choke a small amount once the engine has started, so that
more air can get into the engine. After the vehicle is running, the coil
heats up and gradually opens the choke plate, thereby reducing the vacuum in
the intake manifold and the amount of fuel delivered to the engine. At idle,
the choke does not fully open until 5 or 6 minutes have passed.* If a vehicle
is forced to warm-up more quickly by higher speed/load operation, the choke
may open more quickly.
Normal choke operation, therefore, causes high CO emissions since a very rich
mixture of fuel in air is needed at low temperatures to get a cold engine
started and keep it running. However, a maladjustment of choke controls can
also produce very high CO emissions. If the electric assist assembly of the
choke coil becomes disconnected, the choke plate may stay closed much longer
than it really needs to, thereby causing the engine to produce much more CO
emissions and use much more fuel than is necessary. Disconnections or
maladjustments of choke linkages can also contribute to high CO emissions, if
such maladjustments prevent the choke from opening completely once the engine
is warm. Maladjustments of the choke vacuum break can also contribute to high
CO emissions, if they do not allow the choke to open when the engine is
driving the car.
* "Cold Temperature Emission Factors", Don E. Koehler, Energy Technology
Center, Department of Energy, Bartlesville, Oklahoma, pg. 4.

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2.2.2 Maladjustment of Idle Mixture
An idle mixture screw or screws are present on practically every vehicle that
has a carburetor. The position of the screw controls the amount of fuel that
is delivered to the engine while it is idling. On most pre-1981 model year
vehicles, these screws are very easy to adjust or maladjust. On 1981 and
later vehicles, however, the Parameter Adjustment Regulations require idle
mixture to be non-adjustable.* Manufacturers have sealed the idle mixture
screws after adjustment with metal caps or plugs. Adjustment of idle mixture
after sealing is in most cases not necessary, however, it is possible.**
Maladjustments of idle mixture screws which cause lean mixtures in the engine
are not very common because they cause poor driveability. The engine, being
too lean, may misfire or stall. Maladjustments which cause rich mixtures are
far more common, because many people feel that driveability may be improved
with a richer idle mixture. (Actually, poor driveability can be the result of
many different factors. Maladjustment of idle mixture is an easy task and
performing the maladjustment can sometimes cover up for other problems which
may be causing poor driveability.) A maladjustment of idle mixture which
causes a rich mixture results in an engine producing high CO emissions.
However, this fact has been noted mostly for vehicles tested at 75° in which
the choke system was not required to operate for very long after starting.
At this temperature, idle mixture can have a large percentage effect on total
CO emissions if it is maladjusted. At colder temperatures, the percentage
effect of idle mixture maladjustment on total CO emissions may be smaller.
One purpose of this report is to investigate whether and by how much the
effect of idle mixture maladjustments is affected by temperature.
If a vehicle which has a rich maladjustment of this idle mixture is started
and operated in cold weather (20°F, for example), the resulting high CO
emissions are caused by both choke operation and maladjusted idle mixture. It
is likely that choke operation is the dominant factor in high CO emissions
while the engine is cold, and that maladjusted idle mixture is the dominant
factor when the engine is warmed-up and the choke is fully open. However, it
is possible that a maladjusted idle mixture screw could cause additional cold
start CO emissions above and beyond those produced as the result of choke
operation.
* 1979 and 1980 GM cars also have idle mixture screws which are sealed with
metal plugs in recesses in the carburetor.
** The carburetors must first be removed, the caps or plugs are knocked off or
drilled out, the carburetor is replaced on the engine and then adjustments can
be performed.

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2.2.3 Heated Air Intake Systems
The heated air intake system collects heated air from around the exhaust
manifold of the engine and mixes it with cold air entering the air filter so
that warmed air, instead of predominantly cold air, enters the carburetor to
mix with fuel. The warmer air results in a larger fraction of the fuel being
vaporized than would be the case if colder air were used. This allows total
fuel delivery to be reduced without affecting driveability.
Officials from the State of Alaska have noticed that many in-use vehicles in
Alaska have disconnected heated air intake systems. They are unsure as to
whether the disconnects are deliberate or are the result of normal
deterioration, but they suspect the latter reason because it does not make
sense that people would deliberately disable their vehicles to obtain poorer
cold weather driveability. EPA was unsure of the CO emission effects at cold
temperatures of disconnecting the heated air intake system, so this
maladjustment was added to the I/M effectiveness study, since a disconnected
heated air intake system would be easy to spot in an I/M program that included
an underhood inspection and since the repair is quite simple.
2.3	External Factors
Driving habits are external factors which can affect the amount of CO produced
by vehicles at cold temperatures. Many people warm-up their cars at idle
before embarking on a trip. During idle warm-up periods, the throttle linkage
often engages a high idle cam, making an engine idle faster when warming up
than when it is already warm. This is done to prevent stalling out and
promote faster warm-up times. However, the fast idle speed is lower than the
engine speed that would be used in driving the car. Also, there is no load on
the engine when it is in the fast idle configuration. As a consequence, an
engine warms up more slowly during an idle warm-up than it would if
immediately driven. A longer warm-up time would seem to promote the
production of more CO emissions. However, since the engine is not under load
and is not operating at a higher speed, the volumetric flow rate of air and
fuel through the engine is lower than it would be if the car were immediately
driven. This would seem to decrease the amount of CO produced during idle
warm-up as contrasted to driving immediately after start-up.
2.4	Technology Which Reduces Cold Start Emissions
2.4.1 New Technology
In recent years automobile manufacturers have made improvements in emission
control and fuel delivery systems which have resulted in reduced cold start
emissions. These improvements were in part motivated by the fact that
manufacturers had to reduce CO emissions during the cold start portion of the
75° FTP certification test in order to meet progressively more stringent
standards, particularly the 1981 light-duty vehicle (LDV) CO emission standard
of 3.4 g/mi. Some of the most important improvements made by automobile
manufacturers which have resulted in reduced cold start emissions are (1)
early fuel evaporation systems which preheat the air/fuel mixture in the
intake manifold in order to increase fuel evaporation and thereby improve
cvlinder-to-cylinder fuel distribution and allow total fuel delivery to be

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reduced, (2) closer placement of catalysts to the engine to reduce catalyst
warm-up time, (3) more precise fuel delivery systems such as intake port fuel
injection or throttle body fuel injection and (4) closed loop computer control
of fuel delivery via carburetor or injection systems. These latter systems,
especially the fuel injection systems, deliver fuel to the engine in much more
precise amounts depending on engine temperature, speed, load, and other engine
operating variables.
2.4.2 Block Heaters
Block heaters have been in use for a long time. One of the most common types
of block heaters is called the "frost plug heater." In this system, an
electric heating element is placed in contact with the engine coolant. The
element heats the coolant, thereby keeping certain parts of the engine such as
the engine block or parts of the engine which have direct contact with the
heated water significantly warmer than they would be without the heater.
There is little FTP data on the effects of block heaters on CO emissions.
However, EPA-MVEL is currently conducting a study on three vehicles of the
effect of a frost plug electric heater on CO emissions. The results of this
study should be available within several months of the date at which this
report is published.
2.5 Inspection/Maintenance Programs
An Inspection and Maintenance (I/M) program is a state or locally run program
in which registered vehicles in certain urban areas are required to obtain and
pass a tailpipe emission inspection periodically. Vehicles that have
hydrocarbon (HC) or carbon monoxide (CO) emissions (at idle, 2500 rpm, and/or
loaded cruise) which are greater than state or locally established emission
standards are required to have maintenance to pass that standard.
The EPA has extensively studied the emission reduction- potential of I/M.
EPA's evaluation of 1975 through 1977 model year vehicles in the Portland,
Oregon I/M program revealed that I/M was capable of reducing CO emissions from
vehicles needing repair by about 50%. Put in terms of. mass emission levels,
the fleet of vehicles receiving repairs due to I/M underwent a 20 gm/mi CO
emission reduction from about 40 gm/mi before I/M to about 20 gm/mi after
I/M.* However, these tests were performed at 75°F. The emission reduction
potential of I/M until recently has not been studied at colder temperatures.
Vehicles with maladjusted idle mixture, which is the most common
malmaintenance item in pre-1981 model year vehicle populations,** can be
detected by Inspection and Maintenance (I/M) programs, since maladjustments of
idle mixture cause high idle CO emissions, and these emissions can be detected
by the idle analyzers used in all I/M programs. Most choke maladjustments
* "Questions and Answers Concerning the Technical Details of Inspection and
Maintenance", April, 1979, EPA-IMS-002/QA-1. Available on request from the
I/M Staff, EPA, 2565 Plymouth Road, Ann Arbor, Michigan 48105.
** Vehicles with maladjusted idle mixture may be more common in cold weather
climates than warm weather climates, since the maladjustments are thought to
improve driveability, and driveability may be perceived to be a more frequent
problem in a cold climate than a warm one.

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probably cannot be detected by an idle analyzer, since vehicles are usually
tested when fully warmed-up. However, when an underhood inspection is
included in the I/M test, disconnected choke assist systems can be readily
spotted. Therefore, I/M can reduce CO emissions from vehicles that have
either maladjusted idle mixture or disconnected choke assists. There is
nothing that I/M could or should do about high CO emissions which are the
result of normal choke operation.
2.6 Notes on Test Procedures Used
The 1975 Federal Test Procedure (FTP) with minor modifications where necessary
was used as the primary test cycle within this test program. The FTP requires
vehicle exhaust emissions to be measured in three separate phases of a 31
minute typical urban driving cycle at 75°F. The distinction between phases is
made to characterize the emissions produced from different modes of engine
operation such as cold starting and engine warm-up plus possibly some
stabilized operation, pure stabilized operation, and hot starting. The
driving cycle of the FTP is presented graphically in Appendix 1.
These three phases of the FTP — the cold transient phase, the cold stabilized
phase, and the hot transient phase — are sometimes referred to by their
respective bag numbers (Bag 1, 2, and 3, respectively), since the emissions
from each phase are collected in the different bags and analyzed separately.
The full FTP constitutes a trip distance of 11.1 miles. Emissions collected
during the 11.1 mile trip are reweighted to reflect the average incidence of
hot and cold starts (57% and 43%, respectively) and an average trip distance
of 7.5 miles. However, the distance on Bag 1 (the cold start phase) is only
3.59 miles, and the distance of Bag 1 plus Bag 2 is 7.5 miles. Also, vehicles
are always fully warmed-up prior to the end of the driving cycle on Bag 1,
even when tested at temperatures of 20°F, so Bag 2 always represents
stabilized operation. The comparatively short trip of Bag 1 represents a mix
of cold and warm engine operation, with the mix of the two depending on
temperature.
The 1975 FTP has only a 20 second cold idle warm-up included in the driving
cycle. This is significantly shorter than would be expected in cold weather.
Alaska officials conducted a study in their voluntary I/M program which
revealed that many people in Alaska warm-up their cars at idle for between 2
and 5 minutes.* Therefore, for some phases of testing we added idle warm-up
periods onto the driving cycle of the FTP in an attempt to more closely
simulate cold weather driving.
* The results of this study are tabulated in Appendix 2.

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3.0	TEST PROGRAM DESCRIPTION
Ideally, the effectiveness of I/M should be evaluated by recruiting a large
sample of in-use vehicles, testing them over the range of cold temperatures of
interest, performing I/M-type repairs on the vehicles that would have failed a
typical I/M test, and retesting the vehicles at cold temperatures. However,
the resources to conduct this type of program were not available to EPA. The
only alternative left was to take 4 cars, tune them to manufacturers
specifications, test them at 20°F and 50°F, maladjust and disable them into a
condition that might be expected of some in-use vehicles which would fail an
I/M test, and retest them at 20°F and 50°F. I/M's effect on these vehicles
could then be evaluated by comparing maladjusted emissions at 20°F and 50°F to
the tuned-up emissions at 20°F and 50°F.
3.1	I/M Effectiveness Test Sequence
The test program used to evaluate I/M's effectiveness in cold temperatures is
presented in Table 2.
Table 2
Test Sequence for I/M Effectiveness Study
1.	Check tune-up specifications prior to testing
2.	FTP @ 75°
3.	4-Mode Idle @ 75°
4.	Cool to 50°
5.	FTP @ 50°
6.	4-Mode Idle @ 50°
7.	Cool to 50°
8.	5 min. idle @ 50°
9.	LA-4* following 5 min. idle
10.	Cool to 20°
11.	FTP @ 20°
12.	4-Mode Idle @ 20°
13.	Cool to 20°
14.	5 min. idle @ 20°
15.	LA-4 following idle
16.	Tune-up if maladjusted
17.	FTP (3 75°
18.	Maladjust vehicle (idle mixture, heated air intake,
choke assist) and return to step 5.
* An LA-4 is the driving cycle of the first two phases (cold transient and
cold stabilized, i.e., Bag 1 and Bag 2) of the FTP.

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Steps one through three were performed to assure that each test vehicle was
operating properly. Steps four through eighteen represent all the tests
performed on one vehicle in one configuration (i.e., tuned-up or maladjusted)
at the two temperatures, 20°F and 50°F. The tests conducted at 50° represent
an internal cycle which is repeated at 20°. Steps four through nine as a
group is an example of this internal cycle; the rationale for using this
particular sequence is as follows. The FTP (discussed in Section 2.3 and
illustrated in Appendix 1), which is conducted first, combines a cold start
(that is, driving almost immediately after the engine is started) with other
phases of driving such as stabilized and hot start operation, and is the
benchmark test procedure which is also used in certification of new vehicle
prototypes. The 4-Mode idle is typical of an I/M test that could be conducted
by an I/M program. It consists of Idle(N), 2500 rpm, Idle(N) and Idle(D).
Emissions are sampled from the tailpipe with a garage infrared analyzer during
all four test modes. The five minute idle warm-up followed by an LA-4 was
conducted to simulate a cold climate driving cycle. The LA-4 (illustrated in
Appendix I) is very similar to the 1975 FTP, except that the hot-start (third)
phase of operation is omitted.
3.2	Vehicles
The four vehicles used in this test program were a 1978 Ford LTD, a 1977
Chevrolet Nova, a 1980 Chevrolet Citation, and a 1980 Pinto. Specifications
for the vehicles are listed in Appendix 3.
The Ford vehicles had air pumps with air pump control systems which routed
pump air to the atmosphere (instead of to the exhaust manifold) after 1-2
minutes of engine operation at idle.
3.3	Controlled Environment Test Cell
The vehicles were tested in the Controlled Environment Test Cell (CETC)
located in EPA's Motor Vehicle Emission Laboratory in Ann Arbor, Michigan.
The cell contains a large roll electric dynamometer for simulating vehicle
loads and inertia weights and a constant speed fan for engine cooling. A
diagram of the cell is presented in Appendix 4. The cell is capable of
maintaining any temperature between 20°F and 100°F throughout the duration of
a test.
3.4	Maladjustments and Disablements
The idle mixture maladjustment was performed by first adjusting the idle
mixture of the vehicles to zero-gain propane, or the point at which an
injection of propane into the carburetor caused no increase in engine rpm.
Then the screw was turned out one full turn. The heated air intake system was
disabled by disconnecting the stove pipe from the exhaust manifold to the air
filter. The choke assist system was disabled by disconnecting power to the
thermostatic coil.
Throughout the remainder of this report, we will use the term maladjustments
to mean both maladjustments and disablements.

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3.5 Other Notes on Test Procedures
The starting procedures used during testing were the manufacturers'
recommended cold start and warm start procedures. The cold start procedures
for all vehicles required the driver to set the choke with the accelerator
pedal prior to turning the key. The warm start procedures required the driver
to turn the key without depressing the accelerator pedal.
A large fan was used to blow air over the test vehicles. The speed of the fan
was controlled by the speed of the vehicles, so that the fan's speed increased
with the speed of the test vehicle. A deflector was placed in front of the
vehicle to prevent cooling air from the fan from passing over the vehicle when
idle emissions were sampled.
In most instances a vehicle was allowed to "soak" overnight at the test
temperature (20°?) so that there was reasonable assurance that all components
(tires, oil, etc.) of a vehicle were at the test temperature. However, in
order to expedite testing, a "forced cool down" technique was sometimes
employed. In this cooling technique, fan speed was increased to approximately
55 mph while cell air was maintained carefully at 20°F. This reduced the
"soak time" necessary to cool all components (including engine crankcase oil,
which is the slowest component to cool) to 20° from about 12 hours (with no
fan cooling) to about 4 hours. Vehicles were determined ready for testing
when their engine crankcase oil temperature reached a value of 20+ 2°F.

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4.0	RESULTS
4.1	Effects of Maladjustments on FTP Composite CO Emissions
The effect on FTP CO emissions of various maladjustments is illustrated in
Table 3. Only three of the four vehicles received idle mixture
maladjustment. The Citation, which had a sealed carburetor, did not.
Therefore, emissions from the vehicles in this configuration are compared to
tuned-up emissions from only these three vehicles which had the idle mixture
maladjustment. The other two maladjustments included all four vehicles,
therefore, a separate four vehicle average was computed for tuned-up
emissions. This approach was used in analyzing all of the results related to
I/M effectiveness. Each vehicle received one test at each configuration.
Table 3
Average FTP Composite CO Emissions (g/mi)
for Different Maladjustments
Number of Vehicles	Test Temperature
Configuration
In Sample
20°F
50°F
Tuned-up
3
42.2 g/mi
22.8 g/mi
Malad. Idle Mix
3
66.0
47.9
Tuned-up
4
35.8 g/ai
19.8 g/mi
Disc. Choke Assist
4
195.4
108.6
Disc. Heated Air Intake
4
34.2
29.2
It is evident from Table 3 that vehicles in most maladjusted configurations
emit substantially more CO emissions than when they are tuned-up. However,
Table 3 also shows that CO emissions decreased at 20° when the heated air
intake system was disabled.* Reasons for this behavior are discussed in
Section 5.1. CO emissions from the vehicles with their choke assist systems
* The same relationship was not observed in the average values at 50°F.
However, 3 out of the 4 test vehicles experienced a reduction in FTP CO
emissions at 50" when the heated air intake system was disabled. The average
value reflected an increase because one vehicle experienced a very large
increase in CO emissions. See Table 1 in Appendix 4 for individual vehicle
results.

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16
disconnected are very high. The technicians driving these test vehicles
reported very poor driveability of the vehicles when this maladjustment was
performed. Consequently, we do not expect too many people to disconnect their
choke assist systems to improve driveability in cold weather. Therefore, we
will concentrate the discussion of the results of other test cycles mainly
around the most common maladjustment, idle mixture, and to a lesser extent on
the disconnected heated air intake system.
4.2 Effects of Maladjustments on FTP Bag 1 CO Emissions
The driving cycle of Bag 1 of the FTP is 3.59 miles, so this comparison is
relevant for those vehicles in a cold weather area where vehicles only travel
about this distance and are not allowed to warm-up at idle first. Table 4
presents data illustrating the effects of the maladjustments on Bag 1 CO
emissions.
Table 4
Average Bag 1 CO Emissions (g/mi)
for Different Maladjustments
Number of Vehicles Test Temperature
Configuration		In Sample	 20°F	50°F
Tuned-up
3
131.9 g/mi
90.1 g/mi
Malad. Idle Mix
3
144.2
138.5
Tuned-up
4
114.7 g/mi
78.0 g/mi
Disc. Choke Assist
4
286.8
229.8
Disc. Heated Air Intake
4
112.8
98.8
Although the effect on Bag 1 emissions at 20°F is not as pronounced as it was
for FTP composite CO emissions, it is evident that vehicles in maladjusted
configurations emit more CO emissions from the driving cycle of Bag 1 than
when they are tuned-up. At 50°F the CO reduction is greater going from the
maladjusted idle mixture state to the tuned-up state than at 20°. Reasons for
this behavior are discussed in Section 5.1.
4.3 Effects of Maladjustments on Idle Warm-Up Plus Bag 1 CO Emissions
This comparison is relevant to a cold weather driving cycle in a similar
manner to the previous one, except that the driving cycle over which emissions
were collected included a five minute idle warm-up period. Therefore, this
comparison relates to those vehicles in a cold weather area that only travel
about three or four miles but are allowed to warm-up at idle for five minutes
prior to travelling.

-------
17
The results in Table 5 are presented in g/mile. Although no miles are
travelled during an idle warm-up, CO emissions are produced. Therefore, we
added the mass emissions from the idle warm-up to the mass emissions from
Bag 1, and divided the total by the number of miles travelled over the driving
cycle for Bag 1, which is 3.59 miles.
Table 5
Average Idle Warm-Up Plus Bag 1
CO Emissions (g/mi) for Different
Maladjus tments
Configuration
Number of Vehicles
In Sample	
Test Temperature
20°F
50°F
Tuned-up
Malad. Idle Mix
111.9 g/mi
133.8
32.4	g/mi
79.5
Tuned-up
Disc. Choke Assist
Disc. Heated Air Intake
4
4
93.6 g/mi
382.0
98.9
32.1 g/mi
230.4
45.0
Once again, CO emissions from the vehicles in maladjusted configurations are
substantially higher than CO emissions from the vehicles in tuned-up
configurations, with the exception of the disconnected heated air intake
systems at 20°.'
4.4 Effects of Maladjustments on Idle Warm-Up Plus Bag 1 and 2 CO Emissions
This comparison is relevant to a cold weather driving cycle that consists of a
short idle warm-up (5 min.) and a subsequent trip which is longer than the one
in Section 4.3 (7.5 as opposed to 3.6 miles). The results are presented in
Table 6.
Table 6
Average Idle Warm-Up Plus Bag 1 and 2
CO Emissions (g/mi) for Different
Maladjustments
Conf igurat ion
Tuned-up
Malad. Idle Mix
Number of Vehicles
In Sample	
3
3
Test Temperature
20°F
62.8 g/mi
107.3
50°F
32.2 g/mi
75.4
Tuned-up
Disc. Choke Assist
Disc. Heated Air Intake
4
4
4
52.1 g/mi
280.7
67.6
28.2 g/mi
174.2
45.1
Revised 10/26/82

-------
18
CO emissions from most of the maladjusted configurations are significantly
higher than in the tuned-up configuration. The disconnected heated air intake
is again the only exception.
4.5 Effects of Idle Warm-Up on Trip CO Emissions
In section 2.3 we discussed the factors that would affect whether CO emissions
would be higher from a trip if an idle warm-up period were added. Table 7
presents a comparison of the results of the vehicles in tuned-up configuration
for the Bag 1 test cycle with a 5 minute idle warm-up as cSmpared to the Bag 1
test cycle without an idle warm-up.
Table 7
Average CO Emissions for Trip
Without 5 Minute Idle Warm-Up
and Trip with 5 Minute Idle Warm-Up
Test Cvcle	Number of Vehicles	2Q°F	50°F
5 rain. Idle Warm-Up	4	407 gms. 191 gms.
+ Bag 1
Bag 1 Only	4	412	280
At 20°F, there appears to be very little difference in trip emissions between
the idle warm-up case and the non-idle warm-up case. At 50°F, the idle
warm-up case results in less CO emissions for the trip. It is unlikely that
anyone would regularly warm-up their car at idle at 50° F.
4.6 Effects of Maladjustments on Fuel Consumption
The fuel consumption data is presented in such a way to contrast	fuel
consumption from Bag 1 without an idle warm-up period to fuel consumption from
an idle warm-up plus Bag 1. This will illustrate the differences in	fuel
consumption due to different cold weather driving cycles for a short	trip
(3.59 miles). The data are presented in Tables 8 and 9; other	fuel
consumption data is presented in Appendix 5.
Table 8
FTP Bag 1 Fuel Consumption (gals.)
Without Idle Warm-Up
Number of Vehicles	Test Temperature
Configuration		In Sample		20°F	50°F
Tuned-up	3	.30 gals.	.26 gals.
Ma lad. Idle Mix	3	.30	.28
Tuned-up	4	.27 gals.	.24 gals.
Disc. Choke Assist	4	.38	.32
I-).- cr uppcpj	intake	4	.27	.24

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19
Table 9
Idle Warm-Up Plus Bag 1
Fuel Consumption (gals.)
Configuration
Number of Vehicles
In Sample	
20°F
Test Temperature
50 °F
Tuned-up
Malad. Idle Mix
3
3
.38 gals.
.39
.31 gals.
.39
Tuned-up
Disc. Choke Assist
Disc. Heated Air Intake
4
4
4
.34 gals.
.53
.36
.29 gals.
.43
.36
Generally, fuel consumption is higher (for both Tables 8 and 9) in the
maladjusted configurations than the tuned-up configurations. In no case did a
maladjustment decrease fuel consumption. Tables 8 and 9 also indicate that
fuel consumption is higher when vehicles are warmed-up at idle than when they
are not warmed-up.
4.7 Four Mode Idle Test Results
The results from the idle (N) mode which came after the 2500 rpm
preconditioning period for the Four Mode Idle Test are presented in Appendix
7. Of the three vehicles that received the idle mixture maladjustment, all
three would have been detected by an I/M program with a cutpoint for these
vehicles of 3.021 CO or less.

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20
5.0 CONCLUSIONS
Inasmuch as this test program was limited Co four vehicles, these conclusions
should be viewed as preliminary. EPA loaned the Mobile Emissions Test
Facility (METFac) to the Alaska Department of Environmental Conservation
(ADEC) for the purpose of studying I/M effectiveness in cold weather. During
the 1981-82 winter, the METFac test program recruited in-use vehicles and
tested them as received, not in deliberately maladjusted configurations.
Consequently, the results from the ADEC program will be a more realistic
indicator of how an I/M program could reduce CO emissions in a cold climate.
The METFac program also tested a larger sample of vehicles.
The results of this, test program indicated that for all test cycles used,
reductions in CO emissions occurred when vehicles with maladjusted idle
mixture and disconnected choke assists were tuned-up. This relationship did
not necessarily occur with the repair of the disconnected heated air intake
system. One explanation for this result might be that disablement of the
heated air intake system causes colder, denser, air to pass through the
carburetor, resulting in leaner air/fuel mixtures than would be the result if
the heated air intake system were not disabled. The leaner mixtures would
result in lower CO emissions. Driveability might suffer since fuel
vaporization would be worse with the colder air, causing lean misfires. Such
misfires would not increase CO emissions, however.
The data in Section 4 illustrate that Bag 1 CO emissions from a vehicle with
maladjusted idle mixture are predominantly but not exclusively caused by
normal choke behavior. For example, in Table 5 (page 17) at 50°F the tuned-up
CO emissions on three vehicles are 60.5 g/mi. At 20° F, the tuned up
emissions are 138.4 g/mi, reflecting more choke action. At 20° in the
maladjusted idle mixture configuration, the CO emissions are 164.9 g/mi,
reflecting both increased choke and the maladjustment. Consequently, if a
vehicle has maladjusted idle mixture, a significant portion of Bag 1 CO
emissions will be due to the maladjustment, not just choke behavior. This
means that I/M could be effective at reducing CO emissions from short trips in
cold climates as well as from longer trips in moderate and warm climates.

5.1 Differences in CO Reductions at 20° F and 50
For the FTP composite and 5 minute plus FTP Bag 1 and 2 test cycles, the CO
g/mi reductions obtained in going ¦ from the maladjusted to the tuned-up
configuration for 20° and 50° are approximately the same. These data, along
with the FTP Bag 1 and idle warm-up - plus FTP Bag 1 test cycle data, are
presented in Table 10.

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21
Table 10
CO Reductions Obtained in Going
From Maladjusted Idle Mixture Configuration
to Tuned-Up Configuration: Average of 3 Vehicles




g/mi.
Reductions
Test Cycle


Distance
20 °F

50 °F
FTP Composite


7.5 miles
23.8
g/mi
25.1
FTP Bag 1 Only


3.59
12.3

48.4
5 min. Idle Warm-Up
+ FTP
Bag 1
3.59
40. 2

47.1
5 min. Idle Warm-Up
+ FTP
Bag 1 + Bag 2
7.5
44.5

43.2
For the longer distance test cycles of the FTP composite and 5 minute idle +
Bag 1 + Bag 2, the CO reductions at 20° F are about the same as at 50° F. At
the shorter test cycles (FTP Bag 1 and 5 minute idle plus FTP Bag 1), the CO
reductions due to correcting malajusted idle mixture are smaller at 20° F than
they are at 50° F. These trends are understandable, if it can be demonstrated
that an idle mixture maladjustment has a smaller g/mi impact on an engine when
it is in a choking mode than when it is in a warm stabilized mode. If this is
true, then the shorter test cycles' comparative lack of warm stabilized
operation would explain the smaller g/mi effect of maladjustment in these
cycles. The problem then is to explain why an idle mixture maladjustment
should have only a small effect when the choke is engaged.
We know that choke behavior during cold start delivers extra fuel to the
engine causing corresponding increases in CO emissions. We also know that
maladjusting idle mixture also adds extra fuel to the engine, even during
choke-on conditions, presumably resulting in higher CO emissions. The
question then centers on why CO emissions due to maladjusted idle mixture are
not as high during cold start as they are during stabilized operation.
The answer to this question can be found in examining the effects of choke
behavior and maladjusted idle mixture on the air/fuel ratio. Figure 1 shows
the effects of changing air/fuel ratio on exhaust gas composition. On the
rich side of stoicheometry (approximately 14.7/1), CO concentration is
linearly dependent on air/fuel ratio.
Revised 10/26/82

-------
22
Figure 1
Exhaust Gas Composition Vs.
Measured Air/Fuel Ratio, For
Unsupercharged Automotive
Engine s*
14
12
•	Gtrfion Moftoud*
•	Cjrbon 0«a«J«
•	Orytm
i
4
:
o
i
10
u
ItawN Nr-fwri M*
Our hypothesis is that at stabilized or warm engine temperatures when an
engine is running at stoichiometric or leaner, maladjusting idle mixture
causes a significant decrease in air/fuel ratio, resulting in a significant
increase in CO emissions. In Figure 1, this situation might be represented by
the CO emission increase in going from an air/fuel ratio of 14.7 to 13, a
decrease of 1.7 in the air fuel ratio. Conversely, when the engine is cold
and the choke is operating, the air/fuel ratio is already .very low even if the
idle mixture is correctly adjusted. We suspect that maladjusting idle mixture
causes almost the same amount of excess fuel to reach the engine when the
engine is cold as when it is warm. However, because the denominator (fuel) of
the air fuel ratio is already so large when the engine is cold due to choking
action, the same excess fuel from the idle mixture maladjustment causes a
smaller decrease in air/fuel ratio when the engine is cold than when the
engine is warm. In Figure 1, this situation might be represented by an
* From Emissions from Combustion Engines and Their Control, D.J. Patterson and
N.A. Henein, Ann Arbor Science Publishers, 1979, pg. 99.

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23
initial air/fuel ratio with the choke operating at about 12; with the addition
of the idle mixture maladjustment the air/fuel ratio might only drop 1.2
points to 10.8, versus the drop of 1.7 cited earlier.* Consequently, the
reduction in air/fuel ratio and corresponding increase in CO emissions is not
as large at cold engine temperatures as at warm engine temperatures. This
effect is rather slight, leaving room for the possibility that in fact
maladjusting the idle mixture causes a smaller amount of excess fuel to reach
the engine when it is cold.
Whether an idle mixture maladjustment causes the same or less excess fuel to
reach a choked engine as a warm engine has not yet been settled by this
discussion. Given the changes in intake vacuum patterns that occur with
choking, it is certainly conceivable that less excess fuel comes through the
idle circuit. If it is true that maladjusting the idle mixture causes less
excess fuel for cold engines than it does for warm engines, then our test data
Should show a larger fuel consumption difference between maladjusted and
tuned-up configurations at 50° F than at 20° F. Fuel consumption data for the
FTP Bag 1 and 5 minute idle warm-up plus FTP Bag 1 at 20° and 50° are
presented in Table 11.
Table 11
Fuel Consumption Going from
Maladjusted and Tuned-Up
Configurations, Average of
Three Vehicles
Test Cycle
FTP Bag 1
Idle warm-up plus
FTP Bag 1
Configuration
Maladjusted
Tuned-up
Maladjusted
Tuned-up
Fuel Consumption (gals.)
20°	50°
.303 gals.
.303
.390 gals.
.383
.283 gals,
.260
.390 gals,
.313
The data in Table 11 confirm our hypothesis, since there is a greater fuel
consumption difference between maladjusted and tuned-up configurations at 50°F
than at 20°F.
* Further explanation: Assume 14.7 units of air and 1 unit or fuel during
warm operation with a properly adjusted idle mixture. An idle mixture
maladjustment might increase fuel delivery by 0.131 units, reducing the A/F
ratio to 13. Choke operation might increase fuel delivery by 0.225 units, for
an A/F ratio of 12. Both choke and idle mixture might increase fuel delivery
0.356 units, for an A/F ratio of 10.8.

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24
APPENDICES

-------
Urban
Dynamometer Driving Schedule
(l.A-4)
60
SO
40
:»o
20
10
i i i I i
7 8 » 9 10
11 12 13
2.1 22
16 17 18 19
•tj
'cJ
<0
51
(X
H-
X
fs>
U»
Minutes
[- - Bag 1 Cold Transient
Bag 2 Cold Stabilized
Ex |>l ana t i on
Pictured are the driving cycles of Bags 1 and 2 of the FIT. This portion is
referred to as the l.A-4, or Urban Dynamometer Driving Cycle. The 1975 FTP
adds a 10 minute eiigine-off period (referred to as a "hot soak") after Bag 2,
followed by the Hag I driving cycle which is then referred to as Hag 3 (hot
transient). In some of our tests, we also used a "Bag A", which was the Bag 2
driving cycle repealed after Bag 3.

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26
Appendix 2
The following questions, among others, were asked of 500 participants in the
1979-80 Anchorage Free Emission Control Test (AFECT), eliciting these
responses:
How long do you let the vehicle warm up in the morning on cold mornings
after starting the vehicle for the first time?
How long do you let the vehicle warm up after work during cold days?
When you are shopping and leave the store, how long do you warm up the
vehicle before driving it?
WARM-UP	WARM-UP	WARM-UP
TIME - AM	TIME - PM	TIME - POST
MINUTES % CUMULATIVE % % CUMULATIVE % SHOPPING % CUMULATIVE %
0
8.9
8.9
14.3
14.3
36.0
0.5
10.0

11.6

22.2
1,0
8.9

15.8

17.3
1.5
3.9

5.8

4.5
2.0
9.0
41.1
10.7
58.2
8.1
2.5
3.5

3.0

0.6
3.0
6.1

5.8

2.9
3.5
3.8

2.6

0.4
4.0
3.9

3.2

0.1
4.5
0.2

0.2

6.2
5.0
17.3
75.5
15.0
88.0
4.5
5.5
0.0

0.0

—
6.0
0.2

0.2

—
6.5
0.7

0.2

—
7.0
0.0

0.2

—
7.5
5.1

2.4

—
8.0
0.0

0.0

—
8.5
0.0

0.0

—
9.0
0.4

0.4

—
10.+
18.0

8.8

2.0

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27
Appendix 3
Test Vehicle Specifications
Ford LTD
Nova
Ci tation
Pinto
Year
Emission
Contro1
Sys tem
Engine
Configuration
Di splacement
VIN
Inertia
Weight
Ac tual
Horsepower
Se tting
1978
EGR, Air
pump , oxid,
cat.
V-8
302 CID
1977
EGR, oxid.
cat.
1-6
2 50 CID
1980
EGR, pulse-
air, 3-way
cat., closed
loop fuel
control
1-4
2500 CC
1980
EGR, pulse-
air, oxid.
cat.
1-4
2.3L(14 0CID)
F8863F182034F 1X27D7W100815 1X685AW140457 0T11A114948
4500	3500	2750	2750
10.9
11.2
7.3
9.7
Indolene HO was used as a test fuel on all vehicles at all temperatures.

-------
I'i>v I rcmnuiutn 1 I'nil t:cl Ion Agency
(rear)
(Cronl;)
Vehicle Exhauat
WilpOL HlOl U
AI sieway
Control Punel.

-------
Controlled Environment Test Cell
U.S. Environmental Protection Agency
O

h
*
a
Evaporators
a
a
Air Return Duct
O
O	Ax tul
Blower Outlet
South Side
Insulated Ceiling
Screen Ceiling
Deflector
(in place)
O
O
North Side
Dynamometer
Rolls.
4?
*o
-a
(0
0
0.
H-
X
n
o
a
rt
H-
a
c
ro
p.
K>
kO
Ground Floor
AXIAL AIR FLOW DIAGRAM

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30
Appendix 5
Individual Vehicle CO Emission Results
Table 1
FTP Composite CO Emissions (gm/mi)
208F	50°F
Configuration
LTD
Nova
Citation
Pinto
LTD
Nova
Ci tation
Pinto
Tuned-Up
52.8
29.1
16.5
44.9
35.9
21.7
11.2
10.7
Ma lad. Idle CO
88.1
43.8
*
66.1
88.1
38.0
~
17.6
Disc. Choke Assem.
54.6
427.5
133.7
165.8
57.4
266.6
51.0
59.4
Disc. Heat Intake
49.8
27.4
17.2
42.5
56.5
20.2
9.5
10.6
Table 2
FTP Bag 1 CO Emissions (gm/mi)
	 20°F 	 	 50°F 	
Configuration LTD Nova Citation Pinto	LTD Nova Citation Pinto
Tuned-Up 239.3 96.3 63.1 60.2	155.8 66.8 41.4 47.9
Malad. Idle CO 253.2 103.9 * 75.5	288.4 72.7 * 54.4
Disc. Choke Assem. 252.7 410.0 264.3 220.1	260.8 401.4 113.4 143.6
Disc. Heat Intake 227.6 93.0 66.8 63.7	253.3 60.7 31.8 49.5

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31
Table 3
Idle warm-Up + Bag 1 CO Emissions
(gm/rai. )
Configuration
Tuned-Up
20°F
LTD Nova
131.5 104.8
Citation
38.7
Pinto
99.3
LTD
37.3
Nova
35.0
50°F
Citation
30.
Pinto
25.1
Malac. Idle CO
Disc. Choke As sen.
Disc. Heat Intake
157.6 124.3	*	119.6 101.7
190.6 657.9 320.3 359.2 82.3
127.2 106.8	55.9 105.5 56.0
83.4
454.2
39.0
200.4
25.2
53.4
184.7
59.9
* Idle mixture was
not maladjusted on this
vehicle
because it
had a
sealed idle
mixture screw




Table 4






Idle
Wartn-Uo +
3ag 1 and
2 CO Emissions






(gm/mi . )







20°F



¦ 50°F

Configuration
LTD
Nova
Citation
Pinto
LTD
Nova
Ci tat ion
Pinto
Tuned-Up
64.0
57.1
20.3
67.2
59.2
23.2
16.3
14.2
Malad. Idle CO
150.0
76.6
*>«
95.3
138.0
57.5
*
30.6
Disc. Choke As sen.
112.8
556. 8
190.0
263.3
107.8
355.4
121. 7
111.9
Disc. Heat Intake
109.2
59.6
28.5
73.4
106.1
25.0
20.1
29.1
* Idle mixture was
not maladjus
ted on this
veh ic la
because it
had a
sealed idle
mixture screw.
Se vised 10/25/82

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32
Appendix 6
Individual Vehicle Gas Mileage and Fuel
Consumption Results
Table 1
FTP Composite Fuel Economy
(mpg)
20°F
Configuration
LTD
Nova
Ci tation
Pinto
LTD
Nova
Tuned-Up
12.2
17.0
22.5
19.7
13.3
18.4
Malad. Idle CO
10.4
17.0
*
19.5
10.9
17.9
Disc. Choke Assem.
12.2
6.8
15.6
15.0
13.1
10.2
Disc. Heat Intake
12.3
17.0
19.8
20.7
12.7
18.4
Table 2
FTP Bag 1 Fuel Consumption (gals.) Without
Idle Warm-Up
20 °F
Configuration	LTD Nova Ci tation Pinto LTD Nova
Tuned-Up	.41 .29	.19	.21	.34 .24
Malad. Idle CO
.42
.27
*
.22
.42
.24
Disc. Choke Assem.
.42
.51
.31
.29
.39
.45
Disc. Heat Intake
.40
.27
.22
.21
.39
.23
Table 3
Idle Warm-Up Fuel Consumption +
Bag 1 Fuel Consumption
20°F
Configurat ion
LTD
Nova
Ci tation
Pinto
LTD
Nov,
Tuned-Up
.44
.42
.22
.29
.33
.40
Malad. Idle CO
.44
.43
~
.30
.43
.46
Disc. Choke Assem.
.47
.79
.45
.41
.36
.69
Disc. Heat Intake
.45
.42
.26
.32
.35
. 45
50°F
Ci tation
Pinto
24.1
21.9
*
20.8
20.4
16.9
24.0
22.5
50°F

Citation
Pinto
.16
.20
*
.19
.20
.23
.16
.19
50°F

Citat ion
Pinto
.23
.21
•k
.28
.30
.35
.39
.23
* Idle mixture was not maladjusted on this vehicle because it had a sealed idle mixture sere

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33
Appendix 7
Four Mode Idle Test

Results
- Second Idle
N Mode Tabulated



(Idle
N-2500
RPM - Idle N - Idle D)






Temperature = 20° F




LTD

Nova
Citation
Pinto

Configuration
HC
CO
HC
CO HC
CO
HC
CO
Tuned-Up
9 5ppm
0.03%
180ppm
1.5% lOppm
0.1%
160ppm
0.8%
Malad. Idle CO
115
3.2
420
3.7 *
*
700
5.1
Disc. Choke Assem.
110
0.03
175
1.7 10
0.03
320
0.7
Disc. Heat Intake
110
0.02
500
6.2 10
0.01
275
6.8



Temperature = 50°




LTD

Nova
Citat
ion
Pint o

Conf iguration
HC
CO
HC
CO HC
CO
HC
CO
Tuned-Up.
95ppm
0.02%
180ppm
0.8% OOppm
0.0%
15ppm
0.02%
Malad. Idle CO
125
3.8
400
3.5 *
~
330
3.2
Disc. Choke Assem.
60
0.03
185
1.1 00
00
330
3.2
Disc, heat Intake
150
0.02
330
5.1 5
0.0
20
0.05
* Idle mixture was
idle mixture screw.
not maladjusted on this vehicle because it had
a
sealed

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DATE: NOV 2 1982
SUBJECT: Report on I/M Effectiveness .pf Cold Temperatures

FROM: Phil Lorang, Chief
Inspection/Maintenance Staff
TO: Air Proarams Branch Chiefs, Regions I-X
Recently we sent you a report entitled "Emission Effects of
Inspection and Maintenance at Cold Temperatures" (EPA-AA-
IMS-81-24). Since that time we have discovered that some of
the data for one vehicle were reported incorrectly. Fixing
the data for this vehicle does not result in any change in
conclusions. Rather, it reveals that I/M is more effective
in terms cf percent reductions for the 5 minute idle plus
Bag 1 test cycle than previously reported. See the table
below.
Comparison of 5 Minute Idle Plus
Bag 1 Test Cycle: Erroneous Data
vs. Corrected Data
Reductions Obtained in Average of 3 Vehicles
(Nova, LTD, Pinto); Going From Maladjusted
Idle Mixture to Tuned-Up Configuration
CO g/mi Reductions % Reductions
20 °F	50 °F	2 0 °F 50°F
Case
Erroneous	26.5
Corrected	40.2
Tables affected by the above
5), Table 5 (page 17), Table
31) of the report. We have
pages indicated and attached
67.4	16% 53%
47.1	30% 59%
corrections are Table 1 (page
10 (page 21), and Table 3 (page
made these corrections en the
the new pages to this memo.

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2
Please remove the old pages from the report and insert the
new corrected pages. If you sent this report to someone we
are not aware of, make sure they are also aware of these
changes. We are notifying everyone to whom we sent the
report. If you have questions on these changes, please call
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Attachments

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5
Table 1
CO Reductions Obtained in Going
From Maladjusted Idle Mixture Configuration
to Tuned-Up Configuration: Average of 3 Vehicles


g/mi. Reductions
X Reductions
Test Cycle
Distance
20 °F
50°F
20 °F
50 °F
FTP* Composite
7.5 miles
23.8 g/mi
25.1 g/mi
36%
52%
FTP Bag 1 Only
3.59
12.3
48.4
9%
35%
5 min. Idle Warm-Up +
3.59
40.2
47.1
30%
59%
FTP Bag 1





5 min. Idle Warm-Up +
7.5**
44.5
CM
41%
57%
FTP Bag 1 + Bag 2
* The actual driving distance on the FTP is 11.1 miles. However, emissions
from the 11.1 mile trip are reweighted to reflect the average incidence of hot
and cold start trips during the day (57% and 43%, respectively), and an
average trip distance of 7.5 miles. In cold climates, these average
percentages of hot and cold starts may be different. See Appendix 1 for
further explanations of FTP terminology.
** Although this trip distance like that of the FTP is 7.5 miles, the emission
results have not been reweighted like the FTP to include any hot start trip
results.
The CO g/mi reductions in the table above are nearly the same at 20° as at 50°
for the FTP composite and 5 minute idle warm-up plus FTP Bag 1 + 2 test
cycles. However, for the shorter test cycles of the FTP Bag 1 and the 5
minute idle warm-up plus FTP Bag 1, the reductions at 20° are significantly
less than at 50°. We attribute this relationship to the hypothesis that
maladjusting idle mixture changes the air/fuel ratio less at 20° than at 50°
for the shorter test cycles, since during a short trip at 20° the carburetor
is very rich to begin with because of choke operation. Consequently, fixing
the maladjustment has less impact at 20° than at 50°F. This relationship has
been confirmed with fuel consumption data. For a detailed explanation of this
relationship, see Section 5.1.
The FTP composite CO reduction at 50° (52%) closely matches the 50% reduction
in CO emissions obtained from failed vehicles in the Portland, Oregon I/M
program. This suggests that our idle mixture maladjustment is typical of
in-use vehicles.
Revised 10/26/82

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17
The results in Table 5 are presented in g/mile. Although no miles are
travelled during an idle warm-up, CO emissions are produced. Therefore, we
added the mass emissions from the idle warm-up to the mass emissions from
Bag 1, and divided the total by the number of miles travelled over the driving
cycle for Bag 1, which is 3.59 miles.
Table 5
Average Idle Warm-Up Plus Bag 1
CO Emissions (g/mi) for Different
Maladjus tments
Conf iguration
Number of Vehicles
In Sample	
Test Temperature
20°F
50°F
Tuned-up
Malad. Idle Mix
111.9 g/mi
133.8
32.4	g/mi
79.5
Tuned-up
Disc. Choke Assist
Disc. Heated Air Intake
4
4
93.6 g/mi
382.0
98.9
32.1 g/mi
230.4
45.0
Once again, CO emissions from the vehicles in maladjusted configurations are
substantially higher than CO emissions from the vehicles in tuned-up
configurations, with the exception of the disconnected heated air intake
systems at 20°.
4.4 Effects of Maladjustments on Idle Warm-Up Plus Bag 1 and 2 CO Emissions
This comparison is relevant to a cold weather driving cycle that consists of a
short idle warm-up (5 min.) and a subsequent trip which is longer than the one
in Section 4.3 (7.5 as opposed to 3.6 miles). The results are presented in
Table 6.
Table 6
Average Idle Warm-Up Plus Bag 1 and 2
CO Emissions (g/mi) for Different
Maladjustments
Number of Vehicles	Test Temperature
Configuration	In Sample	 20°F	50°F
Tuned-up	3 62.8 g/mi 32.2 g/mi
Malad. Idle Mix	3	107.3	75.4
Tuned-up	4 52.1 g/mi 28.2 g/mi
Disc. Choke Assist	4	280.7	174.2
Disc. Heated Air Intake	4 67.6	45.1
Revised 10/26/82

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21
Table 10
CO Reductions Obtained in Going
.From Maladjusted Idle Mixture Configuration
to Tuned-Up Configuration: Average of 3 Vehicles
Test Cycle
FTP Composite
FTP Bag 1 Only
5 min. Idle-Warm-Up + FTP Bag 1
5 min. Idle Warm-Up + FTP Bag 1 + Bag 2

g/mi. Reductions
Distance
20°F
o
o
7.5 miles
23.8 g/mi
25.1
3.59
12.3
48.4
3.59
40.2
47.1
7.5
44.5
43.2
For the longer distance test cycles of the FTP composite and 5 minute idle +
Bag 1 + Bag 2, the CO reductions at 20° F are about the same as at 50° F. At
the shorter test cycles (FTP Bag 1 and 5 minute idle plus FTP Bag 1), the CO
reductions due to correcting malajusted idle mixture are smaller at 20° F than
they are at 50° F. These trends are understandable, if it can be demonstrated
that an idle mixture maladjustment has a smaller g/mi impact on an engine when
it is in a choking mode than when it is in a warm stabilized mode. If this is
true, then the shorter test cycles' comparative lack of warm stabilized
operation would explain the smaller g/mi effect of maladjustment in these
cycles. The problem then is to explain why an idle mixture maladjustment
should have only a small effect when the choke is engaged.
We know that choke behavior during cold start delivers extra fuel to the
engine causing corresponding increases in CO emissions. We also know that
maladjusting idle mixture also adds extra fuel to the engine, even during
choke-on conditions, presumably resulting in higher CO emissions. The
question then centers on why CO emissions due to maladjusted idle mixture are
not as high during cold start as they are during stabilized operation.
The answer to this question can be found in examining the effects of choke
behavior and maladjusted idle mixture on the air/fuel ratio. Figure 1 shows
the effects of changing air/fuel ratio on exhaust gas composition. On the
rich side of stoicheometry (approximately 14.7/1), CO concentration is
linearly dependent on air/fuel ratio.
Revised 10/26/82

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31


Idle
Warm-Up
20°F
Table 3
+ Bag 1 CO
(gm/mi.)
Emissions
50°F

Configuration
LTD
Nova
Citation
Pinto
LTD
Nova
Citation
Pinto
Tuned-Up
131.5
104.8
38.7
99.3
37.3
35.0
30.8
25.1
Malad. Idle CO
157.6
124.3
*
119.6
101.7
83.4
*
53.4
Disc. Choke Assem.
190.6
657.9
320.3
359.2
82.3
454.2
200.4
184.7
Disc. Heat Intake
127.2
106.8
55.9
105.5
56.0
39.0
25.2
59.9
* Idle mixture was
not maladjusted
on this
vehicle because it
had a
sealed idle
mixture :




Table 4




Idle Wann-Up + Bag 1 and 2 CO Emissions
(gm/mi.)
20°F
50°F
Configuration
LTD
Nova
Citation
Pinto
LTD
Nova
Citation
Pinto
Tuned-Up
64.0
57.1
20.3
67.2
59.2
23.2
16.3
14.2
Malad. Idle CO
150.0
76.6

95.3
138.0
57.5
*
30.6
Disc. Choke Assem.
112.8
556.8
190.0
263.3
107.8
355.4
121.7
111.9
Disc. Heat Intake
109.2
59.6
28.5
73.4
106.1
25.0
20.1
29.1
* Idle mixture was
not m
aladjusted
on this
vehicle !
because it
had a
sealed idle
mixture ;
Revised 10/26/82

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32
Appendix 6
Individual Vehicle Gas Mileage and Fuel
Consumption Results
Table 1
FTP Composite Fuel Economy
(mpg)
20°F	50°F
Configuration
LTD
Nova
Citation
Pinto
LTD
Nova
Citat ion
Pinto
Tuned-Up
12.2
17.0
22.5
19.7
13.3
18.4
24.1
21.9
Malad. Idle CO
Disc. Choke Assem.
Disc. Heat Intake
10.4
12.2
12.3
17.0
6.8
17.0
~k
15.6
19.8
19.5
15.0
20.7
10.9
13.1
12.7
17.9
10.2
18.4
*
20.4
24.0
20.8
16.9
22.5
Table 2
FTP Bag 1 Fuel Consumption (gals.) Without
Idle Warm-Up
20 °F	50°F
Configuration
LTD
Nova
Ci tation
Pinto
LTD
Nova
Citation
Pinto
Tuned-Up
.41
.29
.19
.21
.34
.24
.16
.20
Malad. Idle CO
.42
.27
*
.22
.42
.24
*
.19
Disc. Choke Assem.
.42
.51
.31
.29
.39
.45
.20
.23
Disc. Heat Intake
.40
.27
.22
.21
.39
.23
.16
.19
Configuration	LTD
Tuned-Up	.44
Malad. Idle CO	.44
Disc. Choke Assem.	.47
Disc. Heat Intake	.45
Table 3
Idle Warm-Up Fuel Consumption +
Bag 1 Fuel Consumption
20°F
Nova
.42
.43
.79
.42
Citation
.22
*
.45
.26
Pinto
.29
LTD
.33
Nova
.40
50°F
Citat ion
.23
Pinto
.21
.30
.43
.46
-k
.28
.41
.36
.69
.30
.35
.32
.35
.45
.39
.23
* Idle mixture was not maladjusted on this vehicle because it had a sealed idle mixture sere

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33
Appendix 7
Four Mode Idle Test
Results - Second Idle N Mode Tabulated
(Idle N-25GO R£M - Idle M - Idle D)



Temperature
« 20° F




LTD

Nova

Citation
Pinto

Conf iguration
HC
CO
_h£
CO
HC
CO
HC
CO
Tuned-Up
9 5ppm
0.03%
180ppm
1.5%
lOppm
0.1%
160ppm
0.8%
Ma lad. Idle CO
115
3.2
420
3.7
it
*
700
5.1
Disc, Choke Assem.
110
0.03
175
1.7
10
0.03
320
0.7
Disc. Heat Intake
110
0.02
500
6.2
10
0.01
275
6.8



Temperature
¦ 50°




LTD

Nova

Citation
Pinto

Configuration
HC
CO
HC
CO
HC
CO
HC
CO
Tuned-Up
95ppm
0.02%
180ppm
0.8%
OOpptn
0.0%
15ppm
0.02%
Ma lad. Idle CO
12 5
3.8
400
3.5
•k
¦k
330
3.2
Disc. Choke Asaetn.
60
0.03
185
1.1
00
00
330
3.2
Disc, heat Intake
150
0.02
330
5.1
5
0.0
20
0.05
* Id le mixture was not maladjusted on this vehicle
idle mixture screw.
because it had
a sea led

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