EPA-AA-IMS/ST-80-4
TEB 80-13
Effects of Gasohol on Idle
HC and CO Emissions
by
Thomas Darlington
Inspection/Maintenance Staff
Richard Lawrence
Technology Assessment & Evaluation Branch
March, 1980
NOTICE
Technical Reports do not necessarily represent final EPA decisions or posi-
tions. They are intended to present technical analysis of issues using data
which are currently available. The purpose in the release of such reports
is to facilitate the exchange of technical information and to inform the
public of technical developments which may form the basis for a final EPA
decision, position or regulatory action.
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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Summary
A test program was run to investigate the effects of gasohol on CO and HC
emissions on an I/M idle test. Three vehicles were set-up to operate on
either gasoline or gasohol. A Hamilton emissions analyzer was used to
measure tailpipe emissions. CO emissions were varied in each of the cars by
adjusting the idle mixture screw, and HC emissions were varied by inducing a
misfire with a misfire generator. At each CO and HC value as specified in
the program, the fuel was switched from gasoline to gasohol while its effect
was noted on tailpipe emissions. The data obtained provided a basis for
determining gasohol's ability to reduce CO and HC emissions for an idle
test.
As the cars were maladjusted, gasohol was found to reduce idle CO about 1.1%
CO. The reduction in idle CO was relatively constant for all three cars
between idle mixture settings of 1.5% and 7.0% CO, and the catalyst cars
experienced a greater average reduction (Figures 3-5).
Unlike the relatively constant idle CO reductions, idle HC reductions attri-
buted to gasohol were vehicle dependent. A non-catalyst car experienced
practically no reductions, a catalyst car experienced an average 188 ppm
reduction, and a second catalyst car experienced a complete reduction (to
zero) for all levels of HC tested (Figures 6-8).
This limited data indicate that a catalyst vehicle just passing New Jersey
standards of 3.0% CO and 300 ppm HC on gasohol would emit about 4.1% CO and
480 ppm HC on gasoline. Similarly, a catalyst vehicle just passing Portland
standards of 1.0% CO and 225 ppm HC would emit about 2.1% CO and 400 ppm HC
on gasoline.
Background
3
A previous EPA test program using a test procedure similar to the,standard
FTP test on a fleet of eleven passenger cars has shown that gasohol reduces
exhaust HC mass (gm/mile) emissions by about nine percent and reduces ex-
haust CO mass (gm/mile) emissions twenty to thirty-four percent compared to
gasoline. However, evaporative HC emissions, which are not measured in an
idle test, increased 62%, resulting in a net HC increase on vehicles fueled
with gasohol. The extensive use of idle tests in State I/M programs war-
ranted determining gasohol emission characteristics on an idle test proce-
dure.
I/ A misfire generator works by grounding the primary of the ignition coil
a controllable percentage of time.
2] Levels of HC were induced by misfire to the limit of HC observed with
this car on gasoline (305 ppm HC).
3/ "Gasohol Test Program," Richard Lawrence, TAER, MVEL, EPA, December, 1978.
4/ 10% ethanol, 90% Gasoline.
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Purpose
The purpose of this study was to investigate the effects of gasohol on CO
and HC emissions in an I/M idle test.
Test Program
Three vehicles were set up to operate from two fuel containers at the front
of the vehicles. The vehicles used were a 1974 Ford Maverick (no catalyst),
a 1977 Chevette (pellet catalyst), and a 1979 Ford Fairmont (monolith cata-
lyst). Vehicle specifications are tabulated in Figure 1. A selector valve
was set up to switch operation of the vehicles between two fuels. Fuels
used were Indolene HO (Fuel 1) and 90% Indolene + 10% Ethanol (Fuel 2).
Indolene HO is a standard reference test fuel. The change in emissions
caused by the addition of ethanol to Indolene is similar to tJie change in
emissions caused by the addition of ethanol to commercial fuel.
The following procedure was used to test each vehicle in each configuration:
1. Warm-up car at idle 15 minutes on Fuel 1.
2. Disconnect and plug cannister line to carburetor.
3. Operate at 2500 rpm for 1 minute.
A. Drop back to idle and read HC, CO and rpm.
\
5. Operate at 2500 rpm for 1 minute, read HC, CO.
6. Switch to Fuel 2 and purge (at 2500 rpm).
7. Drop back to idle and read HC, CO and rpm.
8. Operate at 2500 rpm 1 minute, read HC, CO.
9. Switch back to Fuel 1 and purge (at 2500 rpm).
10. Drop back to idle and read HC, CO and rpm.
11. Change initial HC or CO as indicated in the following configur-
ations.
_5/ "Gasohol Test Program", Richard Lawrence
6/ Cannister line was disconnected to reduce test-to-test variability
caused by cannister loading and purging.
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Target Configurations
1. Adjustment of idle mixture screw to vary CO.
a. Fairmont and Chevette: As-Received, .3%, .5%, 1.0%, 2.0%, 3.0%,
4.0%, 5.0% CO.
b. Maverick: As-Received, .3%, .5%, 1.0%, 2.0%, .... 8.0% CO.
2. Inducement of misfire to vary HC.
a. Fairmont and Chevette: As-Received, 100 ppm or less, 200, 300,
400, 500, 600 ppm Hexane.
b. Maverick: As-Received, 100 ppm or less, 200, 300, . . ., 900 ppm
Hexane.
3. Adjustment of idle mixture plus misfire to vary both CO and HC.
a. Fairmont and Chevette:
CO 2% 3% 3.5% 4% 5% 6%
HC 200 300 350 400 500 600
b. Maverick:
CO 2% 3% 4% 5% 67,
HC 200 300 400 500 600
Results and Discussion
Before testing, both Hamilton analyzers were calibrated according to manu-
facturer procedures with gas standards available at MVEL. Calibration
results are explained in Figure 2.
During testing, it was found that numerous "flow faults" occurring in the
gas sample line of the analyzer were caused by excessive water build-up in
the gas sample line. A water trap was added to the sample line to prevent
this condition from occurring. Sample line modification is illustrated in
Figure 2.
Also during testing it was found that one of the test cars (1979 Fairmont)
had a return line from the fuel pump to the gas tank. When remote tanks
were connected to the fuel pump, unused fuel from these tanks was drained
into the vehicle's main tank. This situation was remedied by returning
unused fuel to the inlet side of the fuel pump.
The following list of comparisons explains results obtained from testing.
Data is graphed and tabulated in the Appendix.
Tj A "flow fault" condition is observed on the analyzer in the form of an
indicator light whenever flow is restricted in the sample line.
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When Idle Mixture Screw was Adjusted:
1. Idle CO decreased on gasohol compared to gasoline by an average of 1.14%
CO between idle settings of 1.2% CO and 8.4% CO. A clear illustration of
this decrease is shown for each car in Figures 9-11. The two catalyst cars
experienced a greater average reduction of CO (1.28% CO) than the non-cata-
lyst car (.90% CO).
2. At 2500 rpm:
a. In the non-catalyst car CO emissions were less on gasohol than
gasoline by 1.45% CO.
b. In the catalyst cars, CO emissions were nearly zero for all con-
figurations (both gasoline and gasohol).
When Misfire was Induced with a Misfire Generator:
3. Idle HC decreased on gasohol compared to gasoline by an average of:
a. 31 ppm Hexane for the non-catalyst car over a range of 100-700 ppm.
b. 188 ppm for the pelleted catalyst car over a range of 300-700 ppm,
and
c. 100% reduction for four configurations tested on the monolithic
catalyst car (70-305 ppm).
These results are illustrated graphically in Figures 12-14.
4. At 2500 rpm, average HC emission on gasohol:
a. Decreased in the non-catalyst car 63 ppm from gasoline.
b. Remained relatively stable at zero for both catalyst cars (both
gasoline and gasohol).
When Idle Mixture Screw was Adjusted While Misfire was Induced:
5. Idle CO decreased on gasohol compared to gasoline by an average of .85%
CO (three cars).
6. Idle HC was almost unchanged in the non-catalyst car, but decreased on
gasohol compared to gasoline on the catalyst cars an average of 109 ppm.
These results are illustrated graphically in Figures 15-17.
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Conclusions
Limited data gathered from this test program clearly demonstrates gasohol's
ability to reduce CO and HC emissions at idle as compared to gasoline. Idle
emissions decreased on gasohol compared to gasoline by about 1.1% CO and 200
ppm HC on two catalyst equipped vehicles when they were operated close to
New Jersey I/M standards of 3.0% CO and 300 ppm HC.
Evaporative HC emissions and NOx exhaust emissions are not measured during
the I/M idle test. However, data taken during the earlier Gasohol Test
Program indicates that these emission components increase on gasohol.
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Appendix
Figure
Figure
Figures
Figures
Figures
Figures
Figures
Table
Table
Table
Table
Table
1
2
3-5
6-8
9-11
12-14
15-17
1
2
3
4
5
Vehicle Specifications
Analyzer Sample Line Modifications
CO on Gasoline (% CO) vs. Change in CO
from Gasoline to Gasohol
HC on Gasoline (ppm HC) vs. Change in HC
from Gasoline to Gasohol
Idle CO: Gasoline vs. Gasohol (% CO)
Idle HC: Gasoline vs. Gasohol (ppm HC)
Idle CO vs. HC: Gasoline to Gasohol
Idle CO - Gasoline vs. Gasohol
2500 rpm CO - Gasoline vs. Gasohol
Idle HC - Gasoline vs. Gasohol
2500 rpm HC - Gasoline vs. Gasohol
Idle CO and HC - Gasoline vs. Gasohol
(combined misfire and idle mixture adjust)
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Figure 1 Vehicle Specifications
Iden tification
Mileage
Year
EGR
Air Pump
Catalyst
Eng. Configuration
Displacement
1974 Maverick
G12-28104
60500
1974
Yes
Yes
None
6-inline
250 CID
1977 Chevette
EPA-128435
6600
1977
Yes
No
Pellet
4-inline
85 CID
1979 Fairmont
G51-11375
1000
1979
Yes
No
Monolith
4-inline
140 CID
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Fig. 2. Sample Line Modification: Hamilton Analyzers
Diagram shows addition of water trap to stock sample line.
IT,
3jl
31=
^ I o
4' Additional Sample
Line Plus Probe
Tailpipe
Stock
Sample
Line
Water
Trap
Analyzer
Calibration of Analyzers
Hamilton Computerized Emissions Analyzers were used to measure tailpipe emissions
during testing. The manufacturer states the analyzer can detect HC and CO in
the following ranges and tolerances*:
Emission
CO
HC
Range
Tolerance
0.0 - 10.0% +3% of full scale
0 - 2000 ppm (hex.) +3% of full scale
The analyzer was calibrated before testing began according to manufacturer
procedures using gas standards of HC and C0 in the followin8 concentrations:
Gas
HC
CO
Concentration
3815.5 ppm propane
5.158% CO
* Autosense Owner's Manual. Hamilton Test Systems, Autosense Service Center,
900 River Street, Windsor, Connecticut 06095.
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10
Figures 3-5. CO on Gasoline
Figures 6-8»HC on Gasoline
(% CO) vs. Change in CO (% CO) (ppm HC) vs. Changes in HC (ppm HC)
From Gasoline to Gasohol. All From Gasoline to Gasohol. All Changes
Changes are reductions. are reductions.
Figure 3 Figure 6
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Figure 4 Firure 7
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MC IPPH1 8H90LIHC
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11
Figures 9-11.Idle CO; Gasoline
Figures 12-14Idle HC: Gasoline
vs.
7
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Figure 9
IOH MVEIUCII W 010. L1HE
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Figure 10
1077 CNEVE7TE US OE6. LIHI
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x X
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t 2 S « S 0 7
CO OH OMOLIHE. X
ri:arc 11
70 nUBHONT U DEO. LIHC
x
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vs
700
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. Gasohol (ppm HC)
Figure 12
107« MVEftiCK «5 DEO. LIHE
X
X
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x/x
x*'
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b tOO tOO 900 MO 100 000 71
RC tPPHI OH90LIHE
Figure 13
1077 CHEVETTE «S OEO. LIHE
x
x
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I 100 tOO 900 MO 100 000 70
NC IPPHI M90LIHE
Figure I/:
070 rmmoHT M no. LIHC
x
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/ » i »-k| fa 1 1 1
100 lof 90S MO SOO 000 701
0
1
(
CO OH OASOLIHC. (
HC IfPH) 6HSOLIHC
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12
Figures 15-17. Idle CO vs. HC; G asoline to Gasohol
Idle CO was adjusted with idle mixture screw while HC
was adjusted with i-iisfire Generator.
Figure 15
187U NflVERICK X-6fl80LI«C,0-e«30HOL
eoo
500
5*00
ft.
0900
z
200
100
0
0
fr * -
. *
8 X
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600
SOO
Figure 17
1919 rmnitoirr x-onaouNE.o-OASOMOi
2*0
100
PERCENT CO
1231
fERCENT CO
700
Figure 16
1977 CHEVE1TE X-OB80LIME.O-OflSOHOL
3 «
PERCENT CO
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13
Table 1. Idle CO: Gasoline vs. Gasohol
% CO Gasoline
% CO Gasohol
Diff.
% Diff.
1974 Maverick
*AR
AR
AR
.68
1.85
,78
,29
,96
,08
,10
6.22
.86
1.60
2.21
,89
,72
,73
6.10
.21
.83
1.53
2.03
3.10
4.15
10
97
.42
.61
.05
.76
.40
,06
,95
.10
6.98
8.37
5.33
1977 Chevette
.01
.20
1.05
1.15
2.04
2.91
4.95
1979 Fairmont
.01
.02
.01
.92
1.98
3.07
3.49
5.20
6.42
7.17
.26
.58
.80
1.02
.89
.90
1.13
1.00
.89
.85
1.40
1.16
1.74
1.68
1.82
1.15
.20
.81
1.52
1.11
1.12
1.08
1.61
.77
.56
1.20
38
49
43
37
27
28
22
16
14
98
87
52
60
45
39
19
95
98
99
55
36
26
31
13
8
14
Average of Differences (column 3)
Maverick .90 (s =
Chevette 1.40 (s =
Chevette and 1.28 (s =
Fairmont
Fairmont 1.13 (s = .35) Excluding leanest two points.
,16) Excluding leanest point.**
,36) " " "
,30) Excluding leanest points.
Total
1.14 (s = .36) Excluding leanest points.
* "AR" is As-received condition.
** Leanest points were excluded because average reduction is greater than
CO gasoline initial setting.
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14
Table 2. 2500 rpm CO Gasoline vs. Gasohol, Maverick Only*
% CO Gasoline % CO Gasohol Diff. % Diff.
AIR 3.96 2.30 1.66 42
4.82 3.28 1.54 32
4.40 2.99 1.41 32
A.62 3.49 1.13 24
4.10 3.00 1.10 27
4.31 2.81 1.50 35
4.24 3.27 .97 23
4.92 1.78 3.14 64
3.77 3.19 .58 15
Average of Differences (column 3)
1.45 (s = .36)
* Chevette and Fairmont exhibited no difference in 2500 rpm gasoline and gasohol
readings (approximately zero % CO on both fuels).
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15
Table 3. Idle HC Gasoline vs. Gasohol
HC ppm Gasoline HC ppm Gasohol Diff. % Diff.
1974 Maverick
*AR 185 175 10 5
290 230 60 21
340 330 10 3
395 395 0 0
440 390 50 11
505 490 15 3
605 535 70 12
700 670 30 4
1977 Chevette
AR 300 180 120 40
400 300 100 25
500 200 300 60
600 380 220 37
700 500 200 29
1979 Fairmont**
73 0 73 100
160 0 160 100
210 0 210 100
305 0 305 100
Average of Differences (column 3)
Maverick 31 (s = 26)
Chevette 188 (s = 81)
Fairmont: All reductions were 100% reduction.
* "AR" is as-received condition.
** 305 ppm HC on gasoline was HC reading at 10.0% misfire.
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16
Table 4. 2500 rpm HC Gasoline vs. Gasohol
Maverick Only*
HC ppm Gasoline HC ppm Gasohol Diff. % Diff.
205 190 15 7
305 265 40 13
340 325 15 4
445 370 75 17
450 360 90 20
575 505 70 12
665 590 75 11
800 680 120 15
Average of Differences (column 3)
63 (s = 37)
* Chevette and Fairmont exhibited very low (less than 20 ppm) HC levels
at 2500 rpm for both gasoline and gasohol.
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Table 5 - Idle CO and HC: Gasoline vs. Gasohol
i
2
i
O
n
R
Combined
idle mixture adjustment
% CO Gasoline % CO Gasohol %
1.90
2.35
3.40
4.45
5.10
.92
1.2
2.0
3.0
4.3
5.0
1.29
1.75
2.82
3.40
4.50
Average of
Maverick
Chevette
Fairmont
1.23
2.50
2.90
3.30
4.40
.01
.52
.60
1.85
3.60
4.20
.01
.30
1.70
2.80
3.90
Differences
1
Catalyst Cars (Chevette &
and misfire
CO* Diff.
.67
.15
.5
1.15
.7
.91
.68
1.4
1.15
.70
.80
1.28
1.45
1.12
.60
.60
% CO Diff
.57 (s = .47)
.94 (s = .28)
.01 (s = .39)
.97 (s = .32)
induced
% Diff
35
6
15
26
14
99
57
70
38
16
17
100
83
40
18
13
HC ppm Gasoline
1974 Maverick
200
300
400
500
600
1977 Chevette
165
210
240
360
465
600
1979 Fairmont
73
200
300
400
500
ppm Diff.
2 (s = 18)
110 (s = 61)
107 (s = 39)
109 (s = 49)
HC ppm Gasohol ppm Diff.
220
320
400
480
590
6
78
60
245
440
550
0
30
210
300
400
20+
20+
0
20
10
159
132
180
115
25
50
% Diff
10+
7+
0
4
2
96
63
75
32
5
8
73
170
90
100
100
100
85
30
29
20
Fairmont)
'+" sign means increase in emissions
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