EPA-AA-TEB-81-23
Fuel Economy and Exhaust Emissions
of a Methanol-Fueled Chevette
by
H. Anthony Ashby
May 1981
Test and Evaluation Branch
Emission Control Technology Division
Office of Mobile Source Air Pollution Control
Office of Air, Noise, and Radiation
U.S. Environmental Protection Agency
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Abstract
This report presents the results of a series of tests conducted over a
period of several months on a 1979 Chevrolet Chevette powered by
anhydrous methanol. Baseline tests with gasoline were also conducted
about three months before the methanol test series began. The car is
part of an alcohol evaluation program run by the Bonneville Power
Administration. These tests were conducted for EPA in Portland, Oregon
by a test contractor, Hamilton Test Systems.
The exhaust emissions from this car were greatly affected by air-fuel
ratio and state of tune. Driveability was not good during most tests
when CO met Federal standards. The best optimized adjustments gave a 10
percent better energy efficiency on pure methanol than on gasoline with
approximately similar exhaust emission levels.
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Background
In 1979, the Bonneville Power Administration (BPA) of the U.S. Department
of Energy began a program of evaluating alcohols as motor vehicle fuels
and gasoline extenders. BPA's activity reflected its interest in
domestically produced alcohol for motor fuel and the need to develop user
experience and information on the subject. With the enactment of the
Energy Security Act of 1980, BPA's program became more significant.
To BPA personnel, methanol (CH^OH) is particularly attractive as a
motor fuel because it is cheaper than ethanol (02^08), which is made
from food crops such as corn, grain, or sugar beets. Methanol would be
made from coal, municipal wastes, and forest wastes.
By the summer of 1980 BPA's program was far enough along that exhaust
emissions tests were needed. Data from Federal exhaust emissions tests
would reveal whether emission-control performance was degraded by the use
of alcohol-gasoline blends or conversion to straight alcohol.
Following inquiries from BPA, the EPA Portland Study Project Office
arranged for a series of tests to be conducted by its testing contractor,
Hamilton Test Systems. In August and September 1980, baseline gasoline
tests and a series of tests with alcohol-gasoline blends were conducted
on a BPA owned Chevette. After the car was converted to run on straight
methanol, a series of tests was conducted between November 1980 and
February 1981.
Test Vehicle
The test vehicle was a 1979 Chevrolet Chevette with 98 cubic inch
displacement engine and automatic transmission. Emission controls on
this car include exhaust gas recirculation and oxidation catalyst.
Dynamometer loads for testing were 2500 Ibs. inertia weight and 9.2
actual hp at 50 mph.
For the gasoline baseline tests, the car was in totally stock condition
with all engine operating variables at manufacturer's specifications.
Converting the engine to run on raethanol included these steps:
The idle mixture was adjusted and the main metering jet was enlarged.
The carburetor float was coated with a methanol-resistant substance. A
mixture heater below the carburetor and a fuel preheater, both making use
of the heat in the engine coolant, were employed to aid in methanol
vaporization. A cold start device was installed for providing a spray of
gasoline into the carburetor during cold ambient cold starts. (This
manually-operated device was not used in the emissions tests.)
The initial ignition timing was advanced about 8 degrees from
manufacturer's specification. Original equipment spark plugs were
replaced with ones of lower heat rating.
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In its original form, the methanol conversion included the plugging of
the vacuum line to the EGR valve. This had been done because of the
erroneous assumption that fueling with methanol automatically resulted in
low NOx emissions. After the first set of tests, the EGR vacuum line was
unplugged.
Testing Program
The tests consisted of the cold start 1975 Federal Test Procedure (FTP)
and the Highway Fuel Economy Test (HFET) for measuring exhaust emissions
and fuel economy. Engine diagnostic tests were conducted from time to
time to check the engine's state of tune. Evaporative emissions were not
measured.
Baseline conditions were established with Indolene HO Unleaded and
commercial unleaded gasolines in tests in August and September 1980.
In November, shortly after the conversion to methanol was completed, a
set of duplicate tests were conducted. These were followed by additional
sets of duplicate tests after various repairs and adjustments from
November 1980 through February 1981.
Results and Discussion
FTP composite mass emissions, FTP fuel economy, and HFET fuel economy are
listed in Table 1. There are also comments on the car's performance on
the FTP. Included are the "baseline" data using Indolene HO and
commercial unleaded regular gasoline plus five different sets of
duplicate tests using anhydrous methanol. (All fuels except Indolene
were supplied by BPA.)
It is important to note that in the Federal Test Procedure, hydrocarbons
are" measured with a flame ionization detector. The response of this
instrument to methanol is significantly less than unity.. Therefore, the
HC emissions listed are estimated to be only 75% of the actual levels of
unburned fuel emitted.
On methanol, the .car was plagued with driveability problems during the
first three minutes of operation on the FTP. These problems were the
result of methanol's high heat of vaporization and the resulting
difficulty in vaporizing methanol in a cold engine. The need to go to
wide-open throttle (WOT) in order to follow the FTP speed-time schedule
reflects the lower energy content of methanol when compared to gasoline.
In the as-received condition after the conversion to methanol, the NOx
emissions were almost three times as high as the baseline tests on
gasoline. (See results for tests 6 and 7.) The party making the
conversion had believed that because methanol "burned cooler" there was
no need for NOx control and so plugged the EGR vacuum line.
The plug was removed for tests 8 and 9. This resulted in reduced NOx
emissions but also severely degraded driveability. The high CO emissions
on test 9 led to the discovery that the carburetor float had swollen in
the presence of methanol and had stuck in a low position, thereby causing
over-fueling. Replacement of that float resulted in tests 10 and 11.
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The vehicle was in fleet service at BPA during most of December and
January, during which time mixture adjustments were made to improve the
cold-ambient driveability. The result of those adjustments are seen in
tests 12 and 13, with the CO emissions at over two times the Federal
standard, and almost three times the baseline levels.
The final adjustment made in this series of tests was to install
different jets in the carburetor. Tests 14 and 15 showed that this
action produced acceptable emissions and unimpaired driveability on the
FTP.
The average results from the baseline on unleaded regular gasoline and
the final "optimized" methanol version are as follows:
Emissions Fuel Economy
HC CO NOx ~TTPHFET
Gasoline .56 13.0 1.13 24.7 30.5
Methanol .75 15.4 1.20 13.3 16.0
The true HC emissions from methanol are probably about one gram per mile.
Fuel Economy can also be expressed according to the energy available in
the fuel. The following values were taken from SAE paper number 800891:
Energy content, gasoline 115,400 Btu/gallon
Energy content, methanol 56,560 Btu/gallon
The FTP fuel economy ratings then become:
Gasoline: 2.14 x 10~4 mile per Btu
Methanol: 2.35 x 10~4 mile per. Btu
It can be said that the energy in the methanol is being utilized about
10% more efficiently than that in the gasoline. This may be attributable
to the advanced spark timing in the methanol configuration.
Conclusions
Tests 14 and 15 showed that a relatively simple conversion of a gasoline
engine to methanol can result in acceptable levels of emissions and
relatively unimpaired driveability. That statement is heavily
qualified. Few people making such conversions will have the benefit of
Federal exhaust emissions tests to use as a diagnostic tool. Few will
also have a customer who is concerned with exhaust emissions.
Despite its reputation among its enthusiasts, methanol does not
automatically "burn clean". All emission controls on a gasoline engine
should remain in place and functioning when a methanol conversion is
made. Particular care must be taken to ensure that there is no material
incompatibility in the fuel system that could lead to overfueling the
air-fuel charge.
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Test Vehicle Condition
No. Repairs, Adjustments
2
3
4
5
6
. 7
8
9
10
11
12
13
14
15
Stock
After conversion
to methanol (EGR
vacuum line
plugged, timing +8'
from mfr. spec.)
Removed plug from
EGR vacuum line
Repaired sticking
carburetor float
Adjusted A/F mixture
to improve cold-
ambient operation.
Replaced carb jet
Table 1
Emissions and Fuel Economy
1979 Chevette, 98 CID, A3
FTP Emissions Fuel Economy
Fuel (gms/mi) (mi/gal)
HC* CO NOx FTP HFET
Indolene HO .47 12.0 1.22 25.1 no test
.51 10.9 1.15 24.9 30.0
.46 11.2 1.15 24.7 30.3
Unleaded- .60 12.4 1.12 24.6 30.7
Regular . .51 13.5 1.14 24.7 30.3
Methanol .58 10.0 3.18 13.6 16.1
.53 12.8 3.21 13.6 16.9
Methanol .81 13.8 .99 13.8 16.6
.88 27.1 .96 13.1 16.8
Methanol .90 12.7 1.06 13.6 17.0
.71 9.5 1.17 13.7 17.0
Methanol .86 35.4 2.06 12.2 14.8
.78 33.4 2.15 12.4 15.1
Methanol .81 15.6 1.19 13.4 16.4
.68 15.2 1.20 13.1 15.6
Comments
Stumble at 165 sec. on FTP. WOT accel. at
170 sec.
Same
Same
Same
Same
Stall at 25 sec, Stumble at 45, 55, 165.
WOT 168-173
Same
Stall at 24 sec, Many stalls at 340. WOT
165-175, 190-200.
Stall at 24 sec, WOT 190-200. False starts
on FTP Bag 3.
Stall at 22 sec, Stumbled btwn. 40-165
WOT 170-175, 190-200
Same
No stalls or stumbles
Stall at 23 sec.
No stalls or stumbles
Brief stumble at 190
sec.
NOTE: In the carbon balance fuel economy calculations, these values were used:
2421 gm C per gallon Indolene and Unleaded Regular
1153 gm C per gallon Methanol
*Due to the response charactersties of the FID instruments to methanol,
only 75% of the actual levels of unburned fuel emitted.
the HC emissions listed are estimated to be
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