71-28
A Report on the Exhaust Emissions from a
Turbocharged Volkswagen
May 1971
John C. Thomson
Bureau of Mobile Sourjce Pollution Control
Office of Air Programs '
ENVIRONMENTAL PROTECTION AGENCY
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Background
An evaluation of turbocharging and its effect on emissions
was conducted on a 1971 Volkswagen supplied by the Schwitzer
Division of the Wallace Murray Corporation.
Device Tested
The test vehicle was equipped with a turbocharger retrofit
package that consisted of a new exhaust system, a revised
heater system and minor changes to fuel, oil and vacuum
lines. The turbocharger was driven by the hot exhaust
gases in front of a muffler and intake air was ducted from
the standard air filter to the turbocharger and then to the
inlet of the carburetor. An electric fuel pump was installed
to give the additional pressure required during high boost
operation.
Test Program
The Volkswagen was initially received with the air correction
jet in the carburetor plugged and a high idle CO concentration
of about 2.5 percent CO. After the first test, the carburetor
was adjusted to give a 0.6 percent CO reading at idle and
the stock air correction jet was reinstalled. After running
tests on the turbocharged vehicle, the complete kit was
removed and the same vehicle was tested without the turbo-
charger with idle CO set at 0.6 percent. At the completion
of this test, the Schwitzer representative requested
additional tests on the VW using an idle CO of 2.4 percent.
This was a standard production Beetle using a four-speed
manual transmission. The engine is a four cylinder air-
cooled opposed cylinder with 96 cubic inch displacement.
There were no internal modifications to the engine or drive
train and all emission controls appeared to be operating.
In order to evaluate the emission performance of the turbo-
charged engine and to compare its results against the
standard engine, two different emission tests were used.
In Table I and Table II data is shown using the 1972 Federal
emission test procedure. This test uses a closed cycle
exhaust sampling system (Constant Volume Sampler) that
collects all the exhaust continuously and samples a small
portion. A non-repetitive driving schedule is used that
is designed to closely duplicate average vehicle driving
patterns. This test will be used for certification of 1972
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and later model year automobiles and is completely described
in the Federal Registers of November 10, 1970, February 21,
1971, and March 20, 1971.
The second test used is the 1970 Federal test procedure.
This is the 7-mode open driving cycle made up of seven
repeats of the 7-mode cycle. For this procedure exhaust
emissions are measured directly from the tailpipe and a
composite result is computed in grams per mile based on
concentrations of pollutants and vehicle weight. These
results are reported in Table III.
In addition to the emission tests a standard performance
test was run to compare the vehicle with and without the
turbocharger with lean idle. This is a full throttle
acceleration test and the results are averages of two runs
in opposite directions on the same day.
Results
A summary of the 1972 emission tests is reported in Table I.
This data is an average of two or more tests taken under
identical conditions. The complete test results are reported
in Table II. Also reported in Table II are results taken
from two similar Volkswagens in our fleet of surveillance
cars. This data indicates that the results from the Volks-
wagen supplied by Schwitzer in stock condition closely
compares with other Volkswagens we have tested. These
results indicate the ability of the turbocharger kit to
maintain emission levels when the system is properly adjusted.
This kit actually showed a slight reduction although whether
this is due to the turbocharger or slight differences in
carburetor adjustment is unknown.
In Table III, the 1970 test results are reported for this
car. The only test on the turbocharged version was as
received with a very rich idle setting and a plugged air
correction jet in the carburetor. This was the only test
run under this condition and the carburetor was returned to
stock condition before running any additional tests.
Table IV compares road performance of the turbocharged kit
to the performance of the stock vehicle using the same
carburetor settings. This shows the dramatic effect that
the turbocharger has on the high speed performance reducing
the 50-80 m.p.h. time from 30 to 20 seconds.
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Conclusions
1. The turbocharger installation has no adverse effect on
emissions when properly installed and adjusted.
2. Emission results on the turbocharged vehicle with
performance optimized were above present standards.
After proper adjustment this vehicle would meet 1972-
1974 emission standards.
3. A considerable improvement in performance with turbo-
charger was found when comparing turbocharged and stock
vehicle..
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Table I
Emission Test Summary, Supercharged Volkswagen
1972 Federal Test Procedure Averages
Turbocharged
(Lean Idle)
No Turbocharger
(Lean Idle)
No Turbocharger
(Rich Idle)
1973 Standards
HC*
3.0
3.5
3.8
3.4
CO
36
41
54
39
CO? NOX
417 2.3
402 2.5
390 2.2
3.0
* All results in grams per mile.
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Table II
1972 Federal Test Procedure Emissions Summary
HC CO CO2 NOx
Turbocharged 3.1 40 456 2.8
(Lean Idle) 3.2 40 411 2.2
2.6 29 383 2.0
No Turbocharger 3.1 39 411 2.4
(Lean Idle) 3.0 41 408 2.5
4.3 42 397 2.6
No Turbocharger 4.1 56 398 2.0
(Rich Idle) 3.6 51 382 2.3
1969 Volkswagen
(Surveillance Car) 4.2 42 331 1.2
1970 Volkswagen
(Surveillance Car) 1.9 30 366 2.0
All results reported in grams per vehicle mile.
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Table III
1970 Federal Test Procedyre Emissions Summary
Turbocharged (Rich
Idle & Modified jets)
No Turbocharger
(Lean Idle)
No Turbocharger
(Rich Idle)
Federal Standards
for 1970 - 1971
HC
2.3
1.6
2.2
2.2
CO
42
18
28
23
NOx
1.8
2.0
1.8
* All results reported in grams per vehicle mile.
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Table IV
Road Performance Data
Turbocharged (Lean Idle)
20-50 m.p.h. 8.7 sec.
0-60 m.p.h. 14.0 sec.
50-80 m.p.h. 26.8 sec. (4th gear only)
19.9 sec. (3rd & 4th gear)
No Turbo-charger' (Lean Idle)
20-50 m.p.h. 10.2 sec.
0-60 m.p.h. 16.4 sec.
50-80 m.p.h. 33.3 sec. (4thgear only)
29.8 sec. (3rd & 4th gear)
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