72-12
Evaluation of a Dual-Chamber,
Spark-Ignition, Two-Stroke Engine
March 1972
Henry L. Gompf
Test and Evaluation Branch
Environmental Protection Agency
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Background
The Dynatech Corporation of Cambrd Ige, Massaehusetts developed
modifications 'for a two-stroke small displacement engine. Because
of this unique approach and little experience with evaluating
two-stroke systems, the Test and Evaluation Branch scheduled
a brief evaluation of the system.
Vehicle Tested
A 1967 Saab equipped with a manual four-speed transmission was
used in the test program. The vehicle has a three cylinder,
49.6 CID engine with oil injection. The engine was modified
by replacing the stock cylinder head. The replacement head .
provided a divided chamber configuration wherein each cylinder
has a precombustion chamber connected to the main chamber by an
orifice. The fuel delivery system utilized was a low pressure
direct injection into both the prechamber and main chamber. The
injection rate to the prechamber was constant while that to the
main chamber was variable. The injection was electronically
controlled and air inlet was unthrottled. The fuel used was JP4.
A spark ignition system was used. In addition, the vehicle was
equipped with a PTX-4 catalytic converter.
Test Program
A hot start 1972 Federal Emission Test Procedure and a cold start
1975 FTP were performed on the vehicle. Details of these constant
volume sampling techniques are presented in the November 10, 1970,
and July 2, 1971, Federal Register. Bag samples were analyzed
using a flame ionization detector for hydrocarbon, nondispersive
infrared analyzer for carbon monoxide and carbon dioxide and a
chemiluminescent analyzer for oxides of nitrogen.
In addition to these tests, steady state cruise emissions were
collected in CVS bags at 20, 30, 40 and 50 miles per hour. These
bags were analyzed in a similar fashion to the previous tests.
A flame ionization detector with heated sample lines was used
to monitor continuous dilute hydrocarbon levels during these
cruises. Use of this instrument enables measurement of the heavy
hydrocarbons associated with the JP4 fuel used which could
otherwise condense out and be missed during bag analysis.
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2.
Results
All of the data compiled during the evaluation is presented in
the Appendix of this report. As the cold start 1975 FTP data
indicates, the vehicle emitted very low levels of carbon monoxide
(3.6 grams per mile) and oxides of nitrogen (.3 grams per mile).
The carbon monoxide level is slightly higher than that allowed
by 1975-76 Federal standards. The oxides of nitrogen level was
below the 1976 requirement. Hydrocarbon levels of the Saab were
quite high. These levels significantly exceeded current Federal
requirements.
A comparison of steady state emission levels of the Saab versus two
production vehicles is also presented in the Appendix This data
indicates an appreciable level of heavy hydrocarbon materials
due to the oil injection and JP4 fuel. Again, this data shows
very low relative carbon monoxide and oxides of nitrogen emissions.
Conclusions
While the system does exhibit very low carbon monoxide and
oxides of nitrogen levels, the excessive hydrocarbon levels
indicate that a major modification to the system would be
necessary to approach 1976 Federal emission standards. If a
modification of the system could be made, this engine configuration
could be considered as a potential low emission power source.
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APPENDIX
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Emission Data
Dynatech Saab
1972 Federal Test Procedure
Hot Start
HC* CO C02 NOx
5.6 gpm 3.3 gpm 429 gpm .3 gpm
1975 Federal Test Procedure
Cold Start
HC* CJD C02 NOx
6.4 gpm 3.6 gpm 430 gpm .3 gpm
* These hydrocarbon results were obtained using FID bag
measurement. It is assumed that the figures are about
30% low due to heavy hydrocarbon condensation.
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Emission Data
Dynatech Saab
Hot Steady State Bag Samples
20 mph ' . HC
Hot FID HC
CO
NOx
30 mph HC
Hot FID HC
CO
NOx
40 mph HC
Hot FID HC
CO
NOx
50 mph HC
'Hot FID HC
CO
NOx
Saab
6
9
1
2
4
2
4
1
2
2
1
.9
.6
.1
.3
.8
.4
.8
.1
.3
.1
.0
.1
.0
.7
.0
.2
gpm
gpm
gpm
gpm
gpm
gpm
gpm
gpm
gpm
gpm
gpm
gpm
gpm
gpm
gpm
gpm
''1971 Ford
(351 CID)
.' 1
-
2
2
1
-
2
3
;
^ 1
: -
: 2
7
1
}
4
9
.2
.9
.4
.2
.3
.1
.2
.5
.1
.2
--
.2
.0
gpm
gpm
gpm
gpm
gpm
gpm
gpm
gpm
gpm
gpm
gpm
gpm
1970 Da
(97 C
1
-
20
2
1
-
11
3
1
-
6
4
1
-
2
7
.9
.3
.5
.7
.2
.3
.6
--
.0
.2
.8
--
.3
.6
gpm
gpm
gpm
gpm
gpm
gpm
gpm
gpm
gpm
gpm
gpm
gpm
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