EXHAUST EMISSIONS FROM A VEHICLE RETROFITTED
WITH THE MONOCAR HC CONTROL SYSTEM
June 1972
Thomas C. Austin
Office of Air Programs
Environmental Protection Agency
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Background
The Monocar HC device was first seen by a Government
representative in the summer of 1969 when Mr. Ken Mills of
HEW observed a prototype device under test at the Automotive
Research Associates (ARA) laboratory in San Antonio, Texas.
Our first written contact with Monocar occured in June of 1970
when EPA's predecessor (NAPCA) was offered a device for testing.
NAPCA accepted this offer in October and Monocar acknowledged
receipt of our agreement to test. We were telephoned by Monocar
in December of 1970 at which time we again stated that we were
willing to test their system. In May of 1971 we were again
contacted by Monocar at which time they told us they were mod-
ifying their system to include NOx control and that they would
like to arrange testing after their own preliminary tests were
complete. In June of 1971 we again told Monocar we would test
their system if data on the new system indicated a potential
for emissions reductions.
In October of 1971 Mr. John Brogan (EPA) received a letter
from Mr. William A. Hayne of the Council on Environmental Quality.
Mr. Hayne asked us to test the Monocar device that had been given
to him by Dr. Echeverria, the brother of Mexico's President.
In November we contacted Monocar, informed them we were going to
test the device supplied by Mr. Hayne and asked them for install-
ation instructions. Rather than send instructions, three Monocar
representatives visited our laboratory in December and brought
with them the equipment necessary to convert our 1971 Ford
Galaxie to the configuration in which the vehicle is sold in
Mexico. This involved changing the carburetor, intake manifold
and distributor. We agreed to test the Monocar system on the
vehicle as it is manufactured in Mexico and report the results
with and without the Monocar system installed.
System Tested
The Monocar system is an air bleed device combined with
distributor modifications which partially eliminate vacuum
advance. The air bleed part of the system consists of an ad-
justable valve which is mounted anywhere in the engine compartment,
The valve is connected to the intake manifold at the base of the
carburetor. On the vehicle tested, a spacer plate fitted between
the carburetor and the intake manifold was drilled to accept two
-a
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small, knurled tubes. Rubber tubing connects these tubes to
the air bleed valve. An open-celled foam air cleaner is used
on the air bleed valve to reduce the amount of dust inducted.
On vehicles without spacer plates between the carburetor and
intake manifold it is necessary to drill into the intake mani-
fold at the base of the carburetor. In either case carburetor
removal is necessary to clean metal chips from the intake manifold,
The distributor modification ,consists of changing the vacuum
advance spring (Ford vehicles only). The modified spring re-
duces vacuum advance. Table II illustrates the difference
between the modified and standard distributors.
Vehicle Tested
The vehicle used to evaluate the Monocar system was a 1971
Ford Galaxie powered by a 351 CID engine with a two barrel car-
buretor and an automatic transmission. This vehicle is one of
the EPA-owned fleet used to evaluate devices and systems. / At
the request of the Monocar people this vehicle was converted to
the configuration manufactured and sold in Mexico. This involved
replacing the intake manifold and carburetor with a four barrel
induction system (Holley carburetor #4550) , changing the dis-
tributor and changing the spark plugs. In this configuration
the vehicle had no emission control system.
At the conclusion of the series of baseline and device
tests the vehicle was returned to the stock (U.S.A. production)
configuration with the two barrel intake system. Another series
of baseline tests was run to compare the control effectiveness
of the Monocar system on an uncontrolled engine to the control
effectiveness of the Ford Motor Company low emission engine
calibration.
Test Program
The 1975-76 Federal Test Procedure was used to determine
exhaust emission levels. This test involves starting a vehicle
after it has been parked in a 68-86°F ambient for at least 12
hours and operating it on a chassis dynamometer simulating an
11.1 mile urban drive which contains a 1.0 minute stop after the
first 7.5 miles. Vehicle exhaust is diluted to constant volume
and a portion of the diluted exhaust is collected continuously
in sample bags during the 31 minutes of driving.
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A flame ionization detector (FID) is used to determine
unburned hydrocarbon (HC) concentration. Non-dispersive in-
frared (NDIR) analyzers are used to determine carbon monoxide
(CO) and carbon dioxide (C0~) concentrations. A chemiluminescent
(CL) analyzer is used to determine both nitric oxide (NO) and
nitrogen dioxide (NO^). The sum of NO and N02 is reported as NOx.
Pollutant concentrations are used to determine the average mass
of emissions per mile of operation.
Two series of tests were run on the Monocar HC system.
During the first series of tests the vehicle exhibited high
hydrocarbons and an erratic idle. After the first test series
it was discovered that two spark plugs were damaged and the
carburetor was calibrated overly rich. This first test series
was voided and a complete second test series was run.
Test Results
The results of the testing appears in Table I. This'table
compares emission levels achieved with the Monocar system
(partial and complete) with the Mexican version (uncontrolled)
of the 1971 Ford and the U.S. version (calibrated for low
emissions) of the 1971 Ford. Also appearing in Table I is the
fuel consumption for each configuration. Fuel consumption
figures reported were calculated from the emissions data by a
carbon balance , technique. Tuc a.clua.1 weight of fuel used was
determined on several tests and the results agreed with the
calculated values. ,
As can be seen from Table I, the Monocar HC system
reduced exhaust emissions from the "uncontrolled" configuration
(baseline A) significantly. This was accomplished with an 11%
increase in fuel consumption. Comparing the Mex:ican version to
the U.S. production version (baseline B), the U.S. production
vehicle produced yower emission levels than the Mexican vehicle
with the Monocar system. The U.S. production version (baseline B)
also had 13% lower fuel consumption than the Monocar modified
Mexican.production version.
A series of tests using only the air bleed portion of the
Monocar HC system demonstrated results typical of enleanment
devices; hydrocarbons were reduced slightly, carbon monoxide
was reduced significantly and oxides of nitrogen were increased
slightly. Incorporating the modification to partially eliminate
vacuum advance reduced oxides of nitrogen and hydrocarbons signi-
ficantly.
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Conclusions
1. The Monocar HC system is an effective control method for
lowering exhaust emissions from uncontrolled vehicles with
minor fuel consumption penalty.
2. The Monocar HC system is not as effective as the recalibrated
carburetors and ignition system which have been developed by
the auto manufacturers.
3. Driveability of the vehicle with the Monocar HC system
installed was not as good as either "baseline" vehicle
(Mexican or U.S. production versions). Increased tendency to
stall after start up was noticed.
4. The proper installation of the Monocar HC system requires
an extremely competent mechanic. This statement is made
because system installation requires removal of the carburetor
and drilling into the intake manifold.
r
5. The durability of the Monocar HC system should be proven
before the system can be considered for retrofit applications.
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Table I
Monocar HC Test Program - 1975 Federal Test Procedure
Test
Number
HC
gpm
CO
gpm
NOx Calculated
gpm mpg
Baseline A (Holley carb.,
Mexican distributor)
Baseline B (stock '71 Ford)
Monocar HC air bleed
Monocar HC air bleed and
distributor modification
Change from Baseline A
Change from Baseline B
18-0204
12-2163
12-2168
Average
18-0261
18-0263
Average
18-0202
18-0192
12-2174
Average
12-2211
12-2214
Average
4,
3,
3,
02
58
58
3.72
2.04
2.10
2.07
2.65
4.24
2.72
3.20
2.29
1.79
2,04
/
-45%
-II
50.56
53.47
56.56
53.70
12.80.
12.14
12.45
15.40
17.90
18.10
17.14
24.16
12.77
5.23
5.67
5.19
5.36
3,
3,
69
65
+48%
6.21
6.26
6.12
6.20
3.98
3.67
3.83
-281
+ 4%
12.95
12.65
12.77
12.80
12.92
12.98
3.67 12.95
14.00
13.26
12.74
13.30
11.10
11.40
11.25
-11%
-13%
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"~~^f Monocar HC Distributor Modification
Manifold
Vacuum (inches
0
1
2
3
,4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
Degrees
Standard Spring
Hg)
0
0
0
0
0
0
0
1
3
4.8
6
6.5
7.5
8.5
9.5
10
10.8
11.5
11.5
11.5
11.5
11.5
of Distributor
Monocar Spring
0
0
.0
0
.0
0
0
0
0
0
'0
0
.3
.3
1
2.3
3.3
4
4.8
5.8
6.3
7
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