73-11
An Evaluation of Three Honda
Compound Vortex Controlled
Combustion (CVCC) Powered Vehicles
December 1972
Thomas C. Austin
Test and Evaluation Branch
Environmental Protection Agency
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Background
This fall the Honda Motor Company of Japan announced
publicly that they had developed an engine featuring
Compound Vortex Controlled Combustion (CVCC), which
would meet the Federal emission requirements for model
year 1975 without after-treatment devices such as thermal
reactors or catalysts. Honda also submitted a detailed
report of their testing program on this engine to EPA
as part of their annual status report. To confirm what
appeared to be a substantial breakthrough in emission
control technology, EPA contacted the Honda Motor Company
and offered to conduct confirmatory tests on a vehicle in
the Ann Arbor laboratory. Honda accepted the EPA offer
and delivered three vehicles for test on December 6, 1972.
Vehicles Tested
All three of the vehicles supplied by Honda were equipped
with essentially the same version of the Compound Vortex
Controlled Combustion (CVCC) engine. Minor differences
included the manufacturing processes used (sand vs. die
casting) and differences in control linkages. Each engine
was a water cooled in-line four cylinder with an overhead
cam. Displacement was 1,948 cc (119 CID). Manufacturer
rated maximum horsepower was 65 (DIN) @ 5000 rpm.
The CVCC engine burns a heterogeneous air-fuel mixture. In
concept it is similar in some respects to the more well-known ,
stratified charge engines of Ford (PROCO) and Texaco (TCCS).
While the Ford and Texaco engines use direct cylinder fuel
injection to obtain charge stratification, the Honda CVCC
engine obtains stratification with the use of a prechamber.
Two separate intake valves are used on each cylinder of the
CVCC engine. One valve is located in the prechamber and the
other in the main chamber. The smallest venturi of the three
barrel carburetor used on the engine supplies a rich mixture
to each prechamber. The other two Venturis supply the engines
main chambers with a very lean mixture. Combustion is initiated
in the prechambers with a conventional ignition system and
spark plugs (one plug per prechamber). As the burning gases
expand from the prechamber, they ignite and burn the lean
mixture present in the main chamber. A drawing of the engine
and a schematic of the combustion system appears in Figure 1.
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2. Hot start 1972, 2-bag FTP (§3000 pound test
weight.
3. Steady state tests @ idle, 15, 30, 45 § 60 mph.
The 1975 FTP was used to determine gaseous emissions, particulate
emissions, and fuel economy at the vehicle's standard test
weight of 2000 pounds. Testing for HC, CO, COz, NOx, and
aldehydes was done in the Ann Arbor laboratory. Particulate
testing was done at Dow Chemical in Midland, Michigan.
Particulate levels were also determined using the hot start
1972 FTP as were the HC, CO, C02, and NOx levels. One of the
hot start tests was run at the 3000 pound test weight to
determine the influence of vehicle weight on exhaust emissions
and fuel economy with the CVCC engine.
Gaseous emissions (HC, CO, C02, and NOx) and fuel economy were
determined during steady state operation at idle, 15, 30, 45,
and 60 mph. Particulates were measured at 60 mph.
The Dow particulate procedure simulates an air quench of the
vehicle's exhaust gas by routing the exhaust into a 15 7/8 inch
diameter tube where it is diluted to a 500 cfm flow. Twenty-
seven feet downstream of the tailpipe samples are pulled from
the diluted exhaust through fiberglass filters, millepore
filters and an Anderson Impactor. While the Dow procedure is
not an "official" or standard particulate test, it does
allow us to compare particulate emission levels from different
vehicles using a common procedure.
• /
A description of the Federal Test Procedure for exhaust
emission testing is enclosed (Attachment I).
Test Results
Results are summarized in Tables I, II, III, and IV. Table I
lists the results on the 1975 Federal Test Procedure for all
three vehicles. The first test (not reported) on the low
mileage car #3652 was aborted due to a binding choke linkage
which was immediately repaired. All other tests on all three
vehicles met the levels required for 1975 easily. NOx levels
were less than one-third the 1975 requirement. About a 501
further reduction in NOx would be required for 1976 NOx levels,
but it should be noted that EGR was not used on these vehicles.
Honda representatives made it clear that the three cars supplied
to EPA were 1975 model year prototypes only, with no modifications
to improve NOx emissions.
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Table IV summarizes the particulate testing results. Results
obtained on three other vehicles using conventional engines are
shown for comparison. The data indicates that the particulate .
emissions from the Honda vehicle are essentially the same as from
conventional engines using equivalent fuels.
Although not reported in the Tables, the low mileage vehicle
was also tested for aldehyde emissions using a wet chemical
technique. The formaldehyde level of the exhaust was too low
to be accurately determined with the procedure used. The CVCC
exhaust aldehyde level is much lower than the conventional engine,
apparently less than .01 grams per mile.
The driveability of the CVCC powered vehicles was evaluated on
the road and there were no problems encountered. The engine
was very responsive and the acceleration was very strong. Honda
reported quarter-mile acceleration times of 17.8 seconds. The
vehicles easily maintained expressway speeds with adequate
passing power in reserve.
Conclusions
1. All three Honda CVCC vehicles tested repeatedly met the
emission levels required for 1975. The lowest emitter of the
three had completed the 50,000-mile AMA durability run without
incident.
2. There does not appear to be a significant fuel economy or
driveability penalty associated with the engine.
3. There is apparently adequate cushion in the emission levels at
the 2000-pound test weight to also meet the 1975 levels with a
50% heavier vehicle.
4. There is no particulate emission or smoke problem associated
with the CVCC engine.
5. There is no aldehyde emission problem associated with the
CVCC engine.
6. Additional NOx control will be required to reach the 1976
levels but the vehicles tested did not employ devices or special
calibration for NOx control.
7. The CVCC engine achieved lower emission levels than any other
gasoline fueled engine without after-treatment ever tested by EPA.
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Table I
Low Mileage
#3652
Honda CVCC Powered Vehicle
1975 Federal Test Procedure
(emission data in grams per mile)
Car
Test
Number
16-0109
16-0114
16-0117
16-0118
16-0122
'75 FTP '72 FTP
HC
.20
.15
.16
.21
.19
CO
2.06
1.96
2.28
2.24
2.05
NOx
.75
.83
1.06
.86
.94
mpg
22.0
22.4
21.9
22.1
22.1
mpg
20.9
21.5
20.6
20.9
20.9
AVERAGE
18
2.12
.89^
22.T
50,000
#2034
Mile Car
16-0106
16-0110
16-0115
16-0116
AVERAGE
.19
.25
.26
.26
.24
1.73
1.73
1.70
1.85
1.75
.65
.57
.64
.73
.65
21.1
22.2
21.0
20.8
21.3
20.0
19.7
19.8
19.5
19.8
Low Mileage
Back-up Car
#3606
16-0123
.23
2.00
1.03 20.7
19.5
1975 Federal Standards
.41 3.40 3.1
1976 Federal Standards
.41 3.40
.40
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Table III
Honda CVCC Vehicle #3652
Steady State Emission Levels
and Fuel Consumption
(emission data in grams per mile except for
the idle mode where data is reported in grams
per minute)
MODE . H£ O) NOx MPG
Idle .06 .23 .02 *
15 mph
cruise
2nd gear .08 1.92 .44 21.0
30 mph
3rd gear .01 .67 .50 29.2
45 mph
cruise
4th gear .007 .41 .75 32.1
60 mph
cruise
4th gear .005 .36 .645 33.0
*idle fuel consumption = 228.6 minutes/gallon
or 12.5 grams per minute.
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