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 preehamber,
Two separate intake valves are used on each cylinder of the
CVCC engine. One valve is located in the preehamber 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 preehamber. 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 preehamber), As the burning gases
expand from the preehamber, they ignite and burn tht lean
mixture present in the main chamber, A drawing of th© engine
and a schematic of the combustion system appears in Figure 1,
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The overall air-fuel ratio of the CVCC engine is significantly
leaner than stoichiometric. Conventional engines cannot be
operated as lean because of the difficulty in igniting mixtures
leaner than about 18:1 A/F. Ignition is easily achieved in
the CVCC engine by locating the spark plug in the fuel rich
prechamber. This very lean overall operation is conducive
to low CO emissions because the high availability of oxygen
facilitates the conversion of CO to C02. The turbulent, oxygen
rich, high temperature operation of the main chamber is essential
in controlling HC emissions.
NOx formation is a function of air C^tO-j) availability and
temperature. A significant portion of the combustion in the
engine occurs in the very rich region of the prechamber where
the air availability is low. By the time the Combustion has
progressed to the main chamber, where there is high air
availability, the temperature has dropped because of expansion.
The vehicles tested were the new Honda "Civic's", a larger
model not yet imported into the U.S. The Civic weighs about
1600 pounds and will carry four passengers. The test weight
required for emission testing is 2000 pounds. These cars
have front wheel drive and all three tested by EPA were
equipped with four-speed manual transmissions.
Two of the vehicles had only about 1500 miles on them at the
time of the EPA testing. The third vehicle had completed a
50,000-mile durability run using the AMA mileage accumulation
schedule. Several components of the engine in the 50,000-mile
car were updated to a "production" configuration at the 44,000-
mile point of the durability test. Modifications consisted
of minor changes to the manifolding and the linkage, dashpot
and choke of the carburetor. These changes did not affect
the emission levels. All three vehicles were run on lead
free fuel (.03 gpg) during the emission testing and the mileage
accumulation. The CVCC engine does not require lead free
fuel, but Honda ran the durability on .03 grams per gallon
lead to determine the durability of the valve train should
the use of unleaded fuels be mandatory in the future. The
vehicles were not equipped with any "add-on" type control
systems such as catalysts, thermal reactors, air injection,
or exhaust gas recirculation (EGR) systems.
Test Program
Three different types of emission tests were performed during
the evaluation:
1. 1975 Federal Test Procedure (FTP) 02000 pound
test weight.
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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, C02, 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
Avhich 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 50%
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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The fuel economy over the LA4 (Federal) driving cycle has been
calculated for each test using the carbon balance technique.
Actual fuel weights were taken once on both the 50,000-mile
vehicle and the low mileage vehicle #3652. The correlation with
the carbon balance data indicated there were no significant leaks
in the system. Results are listed for fuel economy using both
the 1975 (11.1 miles) procedure and the 1972 (7.5 miles) procedure
This was easily accomplished since the first two bags of the 1975
procedure are equivalent to the 1972 procedure. The fuel
economy calculated for the 1972 procedure was compared to the
values calculated for vehicles tested by EPA during our certifi-
cation and surveillance programs. The average 1972 FTP fuel
economy of the Honda vehicles tested (20.4 mpg) was 20% lower
than the average of the 2000 pound 1973 certification vehicles
tested by EPA this year (25.5 mpg). Honda data comparing the
CVCC powered Civic to the standard Civic with a conventional
engine also showed some fuel economy penalty with the CVCC
version but only about 10%. Part of this penalty may be due
to the fact that Honda vehicles tested had a relatively high
power to weight ratio.
The fuel economy results listed on Table II indicate that the
fuel economy during the testing at 3QOO pounds compared favorably
to both the average 3000 pound 1973 certification vehicles and
the 3000 pound pre-controlled vehicles of the 1967 model year.
At the 3000 pound test weight, the vehicle still had adequate
power to keep up with all of the accelerations of the LA4
driving cycle.
The emissions results listed on Table II were derived from a
hot start 1972 2-bag test of the low mileage vehicle #3652. An
average bag I/bag 3 ratio for each constituent of .the exhaust
(HC, CO, CC>2, and NOx) was determined from all the 1975 tests
run on this vehicle. These ratios were multiplied by the grams
,of emissions measured during bag 1 of the hot start test to
estimate what a cold start bag 1 would have been. The result
is called "bag 1 (calculated)". Used in combination with the
two bags of the hot start 1972 test, a "calculated composite"
for a cold start 1975 test was determined.
Table III summarizes the results of the steady state testing.
HC and CO emissions decreased as speed increased while NOx
tended to increase. Emissions in every mode were very low as
would be expected from a vehicle that has inherently low emissions
and does not require modulation of emission control devices to
attain desireddriveability and fuel economy objectives.
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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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HONDA CVCC ENGINE
overhead \
camshaft
spark plug
prechamber inlet -valve
prechamber
Figure 1.
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Table I
Honda CVCC Powered Vehicle
1975 Federal Test Procedure
(emission data in grams per mile)
Low Mileage Car
#3652
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
nro
50,000 Mile Car
#2034
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 II
Honda CVCC Powered Vehicle
3000S Test Weight
HC
Bag 1
(calculated)grams 2.45
Bag 2
(measured) grams .14
Bag 3
(measured) grams 1.59
CO C02 NOx
19.01 1654 6.08
7.17 1789 5.39
13.58 1490 6.47
Calculated
Composite gpm
1975 Federal
Standards
HC
.28
.41
'75 FTP '72 FTP
CO NOx mpg mpg
3.08 1.56 19.4 18.7
3.4 3.1
(1)
LA4 fuel economy of average 3000# 1973 vehicles^, 16.2
LA4 fuel economy of average 3000# 1967* vehicles1- ' 15.4
*no emission control systems
Economy and Emission Control", EPA-OAWP-MSPC, Nov. 1972
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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 HC CXD 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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Table IV
Airborne Particulate Emissions
(all data in grams per mile)
Vehicle
Fuel
'75 FTP
Hot '72 FTP
60 mph
Steady state
Honda CVCC
lead-
free
.036
.040
.012
1972 Chev-
rolet
lead-
free
.009
1971 Chev-
rolet
5 gpg
lead
.021
1970 Chev-
rolet
3.0 gpg
lead
.110
Total non-airborne particulates collected in Dow dilution
system 27 feet downstream of tailpipe during all Honda testing
(146 miles) equalled 1.9086 grams. The average gpm of non-
airborne particulates equalled .013.
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ATTACHMENT I
FEDERAL EMISSION TESTING PROCEDURES
FOR LIGHT DUTY VEHICLES
The Federal procedures for emission testing of light
duty vehicles involves operating the vehicle on a chassis
dynamometer to simulate a 7.5 mile (1972 procedure) or
11.1 mile (1975 procedure) drive through an urban area.
The cycle is primarily made up of stop and go-driving and
includes some operation at speeds up to 57 mph. The
average vehicle speed is approximately 20 mph. Both the
1972 and 1975 procedures capture the emissions generated
during a "cold start" (12-hour soak @ 68°F to 86°F before
start-up). The 1975 procedure also includes a "hot start"
after a ten minute shut-down following the first 7.5 miles
of driving.
Vehicle exhaust is drawn through a constant volume
sampler (CVS) during the test. The CVS dilutes the vehicle's
exhaust to a known constant Volume with make up air. A
continuous sample of the diluted exhaust is pumped into
sample bags during the test. "
Analysis of the diluted exhaust collected in the sample
bags is used to determine the mass of vehicle emissions per
mile of operation (grams per mile). A flame ionization de-
tector (FID) is used to measure unburned hydrocarbon (HC)
concentrations. Non-dispersive infrared (NDIR) analyzers arc
used to measure carbon monoxide (CO) and carbon dioxide (C02).
A chemiluminescence (CL) analyzer is used to determine oxides
of nitrogen (NOx) levels.
These procedures are used for all motor vehicles designed
primarily for transportation of property and rated at 6,000
pounds GVW or less, or designed primarily for transportation of
persons and having a capacity of twelve persons or less. Each
new light duty vehicle sold in the United States in model years
1973 and 1974 must emit no more than 3.4 gpm HC, 39. gpm CO
and 3.0 gpm NOx when using the 1972 procedure. In 1975 the
standards will change to .41 gpm.HC. 3.4 gpm CO and 3.1 gpm NOx
using the 1975 procedure. In 1976 the standards will be .41
gpm HC, 3.4 gpm CO and .4 gpm NOx using the 1975 procedure.
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UNITED STATES
ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
OFFICIAL. BUSINESS
PENALTY FOR PRIVATE USE $300
AN EQUAL OPPORTUNITY EMPLOYER
POSTAGE AND FEES PAID
U.S. ENVIRONMENTAL PROTECTION AGENCY
EPA-335
^^Environmental News
Holmes (202) 755-0710
Fitzwater (202) 755-0344
FOR RELEASE A.M.'S SATURDAY, FEBRUARY 3, 1973
EPA TESTS SHOW HONDA ENGINE MEETS 1975 FEDERAL EMISSION STANDARDS
The Environmental Protection Agency has released test
results showing that an auto engine developed by Honda
Motor Company meets the Federal emission requirements for the
1975 model year without the use of exhaust after-treatment
devices such as catalytic converters.
v The tests, which do not constitute official EPA certifi-
cation, were conducted on three vehicles during December, 1972,
in EPA's laboratories in Ann Arbor, Michigan. The results showed
hydrocarbon emissions to be about one-half of the allowable 1975
level, carbon monoxide emissions were more than one-third lower,
^ nitrogen oxides emissions about two-thirds lower.
* The vehicles supplied by Honda were equipped with the
company's Compound Vortex Controlled Combustion Engine, which
is 'Similar in concept to the stratified charge engine. Each
cylinder of the engine has a double combustion chamber. The
smaller "prechamber" is supplied with a rich air-fuel mixture
while the larger main chamber is supplied with a very lean
mixture. Combustion is initiated in the prechamber. The
burning gases then expand into the main chamber to ignite
and burn the lean mixture.
i
(more)
Return this sheet if you do NOT wish to receive this material O. or if change of address is needed D (indicate change, including zip code).
EPA FORM 1510-1 (REV. 8-72)
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The overall air-fuel mixture is much leaner than in
a conventional engine, which requires a much richer mixture
for ignition.
The vehicle model tested was the new Honda "Civic,"
a car not yet imported into the United States. The vehicle is
about the size of the smaller American compacts. The Civic
weighs about 1600 pounds and carries four passengers.
Two of the vehicles had only about 1500 miles on them
at the time of the EPA tests. The third had completed a
50,000 mile durability run,when tested.
The test report issued by EPA concluded that the engines
achieved "lower emission levels than any other gasoline fueled
engine without after-treatment devices ever tested by EPA."
Other findings in the report are:
There does not appear to be a significant fuel economy
or driveability penalty associated with the engine.
It was estimated that the engine could probably have met
the 1975 standards even if installed in a vehicle weighing 50
percent more than the vehicle tested.
--Additional NOX control would be required to meet the
1976 standards. However, the vehicles tested did not employ
devices or special methods for NOX control. _
Copies of the Honda test report are available from the
Press Office, Office of Public Affairs, EPA, 401 M St., S.W.,
Washington, D.C. 20460.
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