76-6 AW
Exhaust Emissions from a
Diesel-Powered Volkswagen Rabbit
October 1975
Technology Assessment and Evaluation Branch
Emission Control Technology Division
Office of Mobile Source Air Pollution Control
Environmental Protection Agency
-------
Background
The Emission Control Technology Division of the Environmental
Protection Agency is responsible for keeping abreast of new developments
in automotive emission control. This responsibility includes testing of
prototype vehicles that incorporate new developments in control technology
and power systems.
Volkswagenwerk A.G. has developed a small Diesel engine for
installation in the VW Rabbit. This engine potentially offers low
exhaust emissions and high fuel economy. A prototype Diesel-powered
Rabbit was made available to the EPA for an evaluation of its emission
and fuel economy performance.
Test Vehicle Description
The prototype Diesel engine is installed in a 1975 Volkswagen
Rabbit sedan. The engine is a 4-stroke, overhead cam design, with a
displacement of 1500 cc. Rather than designing a new engine, VW has
Dieselized an existing 1500 cc gasoline, engine. The Diesel engine is
built on a block which is almost identical to the 1500 cc gasoline
block. According to VW, the only modification made to the gasoline
block is a small change in a coolant passageway. The same main bearings
are used for both the Diesel and gasoline engines.
The cylinder head has been redesigned to accomodate a prechamber.
The combustion chamber is a modified Ricardo Comet Mark V type. An
external toothed belt drives both the camshaft and the fuel pump.
Glowplugs are used as a starting aid, and are operated by the ignition
key.
The Diesel engine weighs 6 Ibs. more than the 1500 cc gasoline
engine. The total weight of the Diesel Rabbit is 34 Ibs. more than the
weight of the gasoline Rabbit. This is due to modifications necessary
for installation of the Diesel engine (larger battery, etc.).
The power output of the Diesel engine is approximately the same as
that of an 1100 cc gasoline engine which is produced by VW for the
European market. The performance of the Diesel Rabbit is comparable to
that of the 1100 cc Rabbit.
Engine and vehicle statistics can be found in the vehicle description
sheet in the appendix.
-------
Figure 1: Volkswagen Rabbit Sedan.
Test Program
Exhaust emissions and fuel economy were measured in accordance with
the 1975 Federal Test Procedure ('75 FTP) for light-duty Diesel-powered
vehicles and the EPA Highway Driving Cycle. Sulfate emissions were
measured over the EPA Sulfate Cycle. The fuel used for the sulfate
testing was #2 Diesel fuel containing 0.21 wt. % sulfur. A description
of the procedure used for measuring sulfate emissions is given in the
appendix.
When the test vehicle was delivered to the EPA laboratory, it had
accumulated 2500 miles. Four emissions tests were run on the vehicle,
two using the tank fuel and two using #2 Diesel fuel. The tank fuel was
a European Diesel fuel that was in the vehicle when it was delivered.
Due to an instrument malfunction, hydrocarbon emissions were not measured
during these initial tests.
After the first four tests were completed, the Rabbit was returned
to VW for several weeks. When the vehicle returned to the EPA, it had
accumulated another 2000 miles.
Four more emission and fuel economy tests were run. Two tests were
run on #2 Diesel fuel and two on //I Diesel fuel.
In addition, 0-60 mph acceleration time was measured.
-------
Figure 2: Close-up of the engine installation. Note the
belt drive for the fuel pump and camshaft.
-------
Test Results
The Diesel-powered Rabbit demonstrated the following exhaust
emission levels:
'75 FTP Composite Mass Emissions
grams per mile
(grams per kilometer)
Fuel Economy
HC_ CO . NOx (Fuel Consumption)
#2 Diesel Fuel 0.19 0.98 1.19 37.2 mpg
avg. of 4 tests (0.12) (0.61) (0.74) (6.3 liters/100 km)
#1 Diesel Fuel 0.11 0.74 1.12 36.3 mpg
avg. of 2 tests (0.06) (0.46) (0.70) (6.5 liters/100 km)
VW type 2D Fuel 0.69 1.19 39.4 mpg
avg. of 2 tests (0.43) (0.74) (6.0 liters/100 km)
Emissions and fuel economy measured over the EPA Highway Driving
Cycle are presented in the following table:
EPA Highway Cycle
grams per mile
(grams per kilometer)
Fuel Economy
HC C0_ NOx (Fuel Consumption)
#2 Diesel Fuel 0.07 0.46 0.96 48.2 mpg
avg. of 4 tests (0.05) (0.29) (0.60) (4.9 liters/100 km)
#1 Diesel Fuel 0.05 0.47 0.88 48.4 mpg
avg. of 2 tests (0.03) (0.29) (0.55) (4.9 liters/100 km)
VW type 2D Fuel 0.38 0.97 50.3 mpg
avg. of 2 tests (0.24) (0.60) (4.7 liters/100 km)
If the harmonic mean of the '75 FTP (urban) and highway fuel economies
is calculated using weighting factors of 55% for the urban cycle and
45% for the highway cycle, then the combined fuel economy is:
#2 Diesel Fuel: 41.5 mpg (5.7 fc/100 km)
#1 Diesel Fuel: 40.9 mpg (5.8 A/100 km)
VW type 2D Fuel: 43.7 mpg (5.4 £/100 km)
-------
The 55/45 weighting factors have been determined to be typical of
passenger car operation in the U.S. by the Department of Transportation.
A factor contributing to the higher fuel economy when using the VW
fuel may be that the injection timing is optimized for the VW fuel.
Sulfate emissions measured over the EPA sulfate cycle are presented
in Table V. Emissions of SO, are in milligrams per mile. The percent
of fuel sulfur that is converted to SO, is also shown in Table V.
Based on an average of two runs, the acceleration time from 0-60
mph is 16.5 seconds.
Conclusions
The exhaust emissions from the Diesel Rabbit are well below the
emission standards for the 1977 model year. HC and CO emissions are
within the standards for the 1978 model year, but NOx emissions are
about three times the 0.4 gm/mi level required for 1978.
The fuel economy of the Diesel Rabbit is considerably better than
any other vehicle in its weight class. The combined urban/highway fuel
economy is 26% higher than the best fuel economy achieved in the 2250
Ib. inertia weight class during 1976 certification of light-duty vehicles,
and is 52% higher than the average combined fuel economy for the 2250
Ib. weight class.
The 0-60 mph acceleration time of 16.5 seconds is quicker than any
other Diesel-powered car tested by the EPA. EPA engineering personnel
who drove the car judged its driveability and performance to be fully
adequate for all normal driving situations.
-------
Test #
Volkswagen Fuel
16-1631
16-1649
Average
EPA #2 Diesel Fuel
16-1897
15-1898
Average
EPA #2 Diesel Fuel
16-1955
15-1956
Average
EPA #1 Diesel Fuel
16-2265
15-2264
Average
6
Table I
1975 Federal Test Procedure
Mass Emissions in
Grams per Mile
(Grams per Kilometer)
HC
0.18
(0.11)
0.20
(0.12)
0.19
(0.12)
0.12
(0.07)
0.10
(0.06)
0.11
(0.06)
2500
CO
0.70
(0.44)
0.68
(0.42)
0.69
(0.43)
0.95
(0.59)
1.04
(0.65)
1.00
(0.62)
4500
0.90
(0.56)
1.02
(0.63)
0.96
(0.60)
0.74
(0.46)
0.73
(0.45)
0.74
(0.46)
mi./4000
CO 9
259.
(161.)
255.
(158.)
257.
(160.)
272.
(169.)
260.
(162.)
266.
(166.) .
mi./7200
282.
(175.)
275.
(171.)
279.
(173.)
268.
(167.)
277.
(172.)
273.
(170.)
km
NOx
1.22
(0.76)
1.15
(0.71)
1.19
(0.74)
1.18
(0.73)
1.15
(0.71)
1.17
(0.72)
km
1.22
(0.76)
1.22
(0.76)
1.22
(0.76)
1.09
(0.68)
1.14
(0.71)
1.12
(0.70)
75 FTP
npg(l/100 km)
39.1
(6.0)
39.7
(5.9)
39.4
(6.0)
37.2
(6.3)
38.9
(6.0)
38.1
(6.2)
35.9
(6.6)
36.7
(6.4)
36.3
(6.5)
36.0
(6.5)
36.6
(6.4)
36.3
(6.5)
Highway
mpg(l/100 km)
50.8
(4.6)
49.7
(4.7)
50.3
(4.7)
48.7
(4.8)
48.8
(4.8)
48-8
(4.8)
46.5
(5.1)
48.7
(4.8)
47.6
(5.0)
48.3
(4.9)
48.4
(4.9)
48.4
(4.9)
-------
Test //
Volkswagen Fuel
16-1631
16-1649
Average
EPA #2 Diesel Fuel
16-1897
15-1898
Average
EPA #2 Diesel Fuel
16-1955
15-1956
Average
EPA #1 Diesel Fuel
16-2265
15-2264
Average
HC
0.06
(0.04)
0.08
(0.05)
0.07
(0.05)
0.05
(0.03)
0.05
(0.03)
7
Table II
EPA Highway Cycle
Mass Emissions in
Grains per Mile
(Grams per Kilometer)
2500 mi./4000 km
CO C02
0.39 200.
(0.24) (124.)
0.37 204.
(0.23) (127.)
0.38 202.
(0.24) (126.)
0.50 208.
(0.31) (129.)
0.50 208.
(0.31) (129.)
0.50 208.
(0.31) (129.)
4500 mi./7200 km
0.41 218.
(0.25) (135.)
0.43 208.
(0.27) (129.)
0.42 213.
(0.26) (132.)
0.45 210.
(0.28) (131.)
0.48 209.
(0.30) (130.)
0.47 210.
(0.29) (131.)
NOx
0.97
(0.60)
0.97
(0.60)
0.97
(0.60)
0.91
(0.57)
0.95
(0.59)
0.93
(0.58)
1.04
(0.65)
0.95
(0.59)
1.00
(0.62)
0.85
(0.53)
0.90
(0.56)
0.88
(0.55)
mpg(1/lOQ km)
50.8
(4.6)
49.7
(4.7)
50.3
(4.7)
48.7
(4.8)
48.8
(4.8)
48.8
(4.8)
46.5
(5.1)
48.7
(4.8)
47.6
(5.0)
48.3
(4.9)
48.4
(4.9)
48.4
(4.9)
-------
EPA #2 Diesel Fuel
Table III
Steady State Mass Emissions in
Grams per Mile
(Grams per Kilometer)
Test //
Idle
15-1644
15 mph/24 kph
15-1645
HC
CO
NOx
mpg(1/100 km)
2nd gear
30 mph/48 kph 4th gear
15-1646
45 mph/72 kph 4th gear
15-1647
60 mph/97 kph 4th gear
15-1648
1.76 gms 106. gms 0.54 gms
1.67 221. 0.80
(1.04) (137.) (0.50)
0.51
(0.32)
0.43
(0.27)
0.50
(0.31)
154.
(96.)
180.
(112.)
214.
(133.)
0.66
(0.41)
0.95
(0.59)
0.97
(0.60)
45.4
(5.2)
65.7
(3.6)
56.0
(4.2)
47.3
(5.0)
-------
Table IV
VW Rabbit Diesel
Individual Bag Emissions in
Grams per Mile
Test //
Volkswagen Fuel
16-1631
16-1649
EPA #2 Diesel Fuel
16-1897
15-1898
EPA #2 Diesel Fuel
16-1955
15-1956
EPA //I Diesel Fuel
16-2265
15-2264
Bag 1: Cold Transient Bag 2: Stabilized' Bag 3: Hot Transient
HC CO CO? NOx mpg HC CO CO7 NOx mpj>L HC CO C02 NOx mpg Weighted 75 mpg
2500 Miles
0.77 252. 1.29
0.73 256. 1.19
1.14 299. 1.35 33.8
1.20 257. 1.17 39.2
4500 Miles
0.93 1.00 303. 1.24 33.3 0.72 0.97 285. 1.26 35.5 0.44 0.70 260. 1.14 39.0
3.27 1.10 299. 1.23 33.8 0.66 1.14 273. 1.25 36.9 0.48 0.74 259. 1.14 39.1
0.75 293. 1.16
0.73 277. 1.16
0.89 269. 1.10 37.6
1.04 286. 1.18 35.3
0.53 246. 1.13
0.55 238. 1.07
0.69 230. 0.98 44.0
0.73 246. 1.08 41.1
37.2
38.9
35.9
36.7
0.73 C.77 280. 1.08 34.5 0.39 0.79 273. 1.15 35.4 0.33 0.62 250. 0.98 38.7 36.0
0.47 0.83 305. 1.18 33.2 0.37 0.75 273. 1.16 37.1 0.31 0.61 263. 1.07 38.5 36.6
-------
10
Table V
EPA Sulfate Cycle
Mass Emissions and
Fuel Economy
Gaseous
Emissions
grams per mile
CO
0.58
0.58
0.56
0.58
0.56
0.58
0.59
0.58
NOx
1.02
0.99
0.98
1.00
1.03
1.04
0.96
0.96
Fuel
Economy
mpg
46.5
45.7
46.2
44.0
46.9
45.3
47.0
46.2
Sulfates
Emissions
milligrams per mile
10.12
9.19
10.29
10.84
9.31
8.68
8.39
8.49
% Conversion
of S to SO,
2.60
2.32
2.63
2.64
2.41
2.17
2.18
2.17
-------
Appendix
-------
VW Diesel Rabbit
Procedure used to Measure Sulfate Emissions
1. The fuel was drained from the test vehicle. The vehicle was re-
fueled with #2 Diesel fuel containing 0.21 wt. % sulfur. This fuel was
used throughout the sulfate testing.
2. The vehicle was driven over one LA-4 cycle with the test fuel in
preparation for the test series.
3. The following sequence of test cycles was used to measure sulfate
emissions.
a) Cold start '75 FTP
b) Two hot start sulfate cycles
c) One EPA Highway Driving Cycle
d) Two hot start sulfate cycles.
This sequence was run on two consecutive days.
4. The barium chloranilate procedure was used to determine the con-
centration of sulfates in the exhaust.
-------
TEST VEHICLE DESCRIPTION
Chassis model year/make - 1975 VW Rabbit Sedan
Emission control system - Engine Modifications
Engine
type .. 4 stroke, Diesel, 1-4, ohc, indirect injection
bore x stroke 3.012 x 3.149 in./76.5 x 80.0 mm
displacement . . 90 cu in./1475 cc
compression ratio . . 23.5:1
maximum power @ .rpm 48 net hp @ 5000 rpm/36 kW @ 5000 rpm
fuel metering Bosch fuel injection, mechanical
fuel requirement #2 Diesel
Drive Train
transmission type ........ 4 speed manual
final drive ratio . . 4.22:1
Chassis
unibody, transversely-mounted front engine,
type . front wheel drive
tire size • 155 R x 13
curb weight 1950 lbs/885 kg
inertia weight . 2250 Ibs
passenger capacity ^
durability accumulated on system . 4500 mi./7200 km
------- |