71-23
A Report on the Emission Performance of the
Army Sponsored Ford Stratified Charge Engine
April 1971
John C. Thomson
Division of Emission Control Technology
Mobile Source Pollution Control Program
Air Pollution Control Office
ENVIRONMENTAL PROTECTION AGENCY
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Vehicle Tested . .
The vehicle tested during this evaluation was an Army.M-151
1/4 ton truck. This was the same vehicle tested in May
1970 with only minor modifications to the emission control
system. The M-151 is a general purpose vehicle used through-
out the world by the U. S. Army. It is equipped with a four
^
wheel drive system with the front wheel drive portion con-
trolled by the driver. It is also equipped, with a four
speed transmission. This transmission has a very low first
gear and for normal driving it is not used. For all of the
emission tests, the transmission was used only in second,
third and fourth. A modified shift pattern was suggested by
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Ford due to the unusual weight to hdrsepower ratio of this
vehicle. The Army M-151 is tested with an inertia weight of
3000 pounds calculated from the actual weight of the vehicle.
This vehicle is supplied with a seventy horsepower engine,
and when the friction losses of the drive train are taken
into account, can only meet the required accelerations with
difficulty. In addition, the independent rear suspension
system will not tolerate the vibration from the four cylinder
engine at low speed, necessitating more gear changes than
normally required. As a result, it is difficult to achieve
the best possible emission results from this engine as
installed in the Army vehicle.
The engine used in these tests, a 141 CID four cylinder with
3" bore and 3 7/8" stroke, was developed by the Ford Motor
Company through joint U. S. Army - APCO contracts. This
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engine is the "low emission" version of their stratified
charge combustion system and is called the Proco conversion.
The basic stratified charge system used by Ford uses an un-
throttled air intake with fuel injected directly into the
cylinder. This engine uses a low pressure (600 p.s.i.) mechani-
cal fuel injection pump that is integrated with the ignition
distributor. The injected fuel mixes with a portion of the
air in the vicinity of the spark plug, where it is ignited.
The combustion system is shown in Figure 1. The extended tip
spark plug places the spark near the center of the cup combus-
tion chamber.
!
In order to provide low emissions from this engine, several
modifications were made in the control systems. Extensive
dynamometer tests indicated that a very close control over
fuel air ratio was required in order to achieve the emission
values needed to meet 1976 standards. For this reason an air
throttle system was developed to provide a 17:1 air-fuel
ratio. In addition exhaust gas recirculation was added to
reduce the amount of oxides of nitrogen. Due to the direct
cylinder injection this exhaust gas .recirculation seems to
have no effect on driveability, even at 11% recycle used
during the first three minutes of test. During the
remainder of the test, about 9-10% recycle was used.
This engine was provided with a thermal reactor. However,
the contribution of the reactor to emission reduction was
minimal according to Ford data. In addition, an Engelhard
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off-the-shelf catalytic reactor was used to reduce the peak
on hydrocarbons and to encourage a reaction between the CO
and NO in the exhaust. A lead sterile fuel was used to be
compatible with this reactor.
The air-fuel ratio control was an experimental unit and did
not contain an ambient pressure compensator. The lack
of pressure compensation made the system dependent on atmos-
pheric pressure and explains some of the variation in test
data.
As this vehicle does not need enrichment during start or
warm-up, there is little change between cold and hot start
data other than that found due to the cold catalyst. For
this reason repetitive hot starts were not attempted.
Data on two new standard M-151's is also enclosed for infor-
mation. A single number has been obtained by averaging 3
tests on each vehicle.
Data from this vehicle was reported in report number 70-4
"Exhaust Emissions from a Stratified Charge Ford Combustion
Process (FCP) Engine". In addition, data on another stan-
dard M-151 is in report number 70-2 "Emissions from a Standard
M-151 Jeep".
f
Tests Used
In order to evaluate the emission performance of the vehicles
tested the 1972 LA4-S4 test cycle was used for all tests.
This is the test cycle that will be used for certifying all
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new light duty motor vehicles beginning in 1972.
Theemis-
sion standards for various years are shown below, with the
1975 standards also shown with the emissions data.
HC CO N02
1972 3.4 39
1973 3.4 39 3
1975 .46 4.7 3
1976 .46 4.7 *
*The number for 1976 NOX has not been determined although
present thinking is that it will be in the range of 0.3 to 0.7.
Throughout the report, HC will be used to abreviate unburned
hydrocarbons, CO will be used for carbon monoxide and NOx
for oxides of nitrogen.
For these tests results are reported with HC measured using a
flame ionization detector, CO and C02 using-a non dispersive
infrared analyzer and oxides of nitrogen using a modified
Saltzman technique and the chemiluminescent technique.
Emission Results
The results of our tests are reported in Tables 1 and 2.
In
Table 1 a comparison is made between the projected standards,
the vehicle as tested and the standard M-151.
From this table
it appears that the vehicle may meet the standards for 1976.
The emission reduction over the standard vehicle is very
.signifi6ant.
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Conclusions
The Ford stratified charge system has the potential of meet:ing
the 1976 emission standards and still maintain the driveability
. and fuel economy of the uncontrolled vehicle.
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Table 1
1972 LA4-S4 Emission Test Comparison
All Results in Grams Per Mile
HC CO C02 NOx NOX
FID IR IR Saltz CI
PROCO (FCP) 0.3 3.2 439 0.6 0.6
Federal Standards .(1976) 0.46 4.7 ..3-.7 (es t.)
Standard M-151
(I of 2 Vehicles, 6 tests) 5.4 122 428 1.8 2.0
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- Table 2
1972 LA4 Emission Test Results
All Results in Grams Per Mile
All Tests on Ford Proco System
Notes
No EGR
EGR Special Shift
EGR Special Shift
EGR Special Shift
EGR Standard Shift
HC
FID
0.2
0.3
0.3
0.6
0.4
CO
IR
0.9
3.2
1.7
1.5
1.7
C02
IR
376
439
412
386
435
NOX
Saltz
1.9
0.6
0.9
1.0
0.5
NOX
CI
1.9
0.6
0.9
1.2
0.7
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