76-26 AW
Exhaust Emissions and Fuel Economy of a
Diesel-Powered Citroen Sedan
August 1976
Technology Assessment and Evaluation Branch
Emission Control Technology Division
Office of Mobile Source Air Pollution Control
Environmental Protection Agency
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Background
The Environmental Protection Agency is interested in the feasibility of
using the Diesel engine as a powerplant for light-duty vehicles. When
compared to the Otto cycle engine, the Diesel engine generally exhibits
lower fuel consumption and lower exhaust emissions. On the other hand,
the Diesel engine typically has a lower power-to-weight ratio, is noisier,
and has objectionable exhaust odors.
Generally, when a new Diesel-powered vehicle is developed, the EPA is
interested in obtaining a prototype version of the vehicle for an evalua-
tion of exhaust emissions and fuel economy. Such evaluations may be
brief, consisting of characterization of fuel economy and HC, CO and NOx
emissions. At other times, more extensive tests may be carried out to
quantify odor, smoke and particulate emissions.
The Citroen Company of France is intending to enter a Diesel-powered car
in the U.S market. Before attempting new vehicle certification, Citroen
requested a test program at the EPA Ann Arbor, Michigan, laboratory to
establish correlation between the Citroen laboratory and the EPA laboratory.
This report summarizes the exhaust emissions and fuel economy measured
during the correlation program at the EPA laboratory. The conclusions
from the EPA evaluation test can be considered to be quantitatively
valid for the specific test vehicle used, however, it is reasonable to
extrapolate the results from the EPA test to other similar vehicles in a
directional or qualitative manner, i.e., to suggest that similar results
are likely to be achieved on similar vehicles.
Test Vehicle Description
The vehicle supplied for the test program is a 1976 Citroen Pallas CX
sedan. The engine is a four-cylinder Diesel with a prechamber type of
combustion chamber. The engine Is mounted transversely, and drives the
front wheels through a four-speed manual transmission.
The vehicle was tested at an inertia weight of 3500 Ibs. A compilation
of pertinent vehicle statistics is given on the Vehicle Information
sheet at the end of this report.
Test Program
Exhaust emission and fuel economy tests were conducted in accordance
with the 1975 Federal Test Procedure ('75 FTP) for light-duty Diesel
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vehicles (Federal Register, June 30, 1975, Vol. 40 No. 126, Part III).
Testing included the '75 FTP, the EPA Highway Fuel Economy Test (HFET),
measurement of steady state emissions, and acceleration time from 0-60
mph.
Test Results
Exhaust emissions and fuel economy of the Citroen Diesel are summarized
in the following tables.
•75 FTP
Mass emissions in
grams per mile
(grams per kilometer)
HC CO NOx Fuel Economy
(Fuel Consumption)
Average of 0.40 1.8 1.54 24.9 miles/gal.
2 tests (0.25) (1.1) (0.96) (9.5 liters/100km)
Average of
2 tests
HFET
Mass emissions in
grams per mile
(grams per kilometer)
HC
0.16
(0.10)
CO
0.7
(0.5)
NOx
1.46
(0.91)
Fuel Economy
(Fuel Consumption)
32.1 miles/gal.
(7.4 liters/lOOkm)
Combining the '75 FTP and HFET using weighting factors of .45 and .55
respectively (and averaging harmonically), yields a combined fuel economy
of 27.7 miles/gal.
Figure 1 shows the combined city/highway fuel economy of the Citroen
Diesel relative to EPA Certification data for 1976 model vehicles.
Diesel-powered passenger cars were not included in the calculation of
the sales-weighted fuel economy. The combined city/highway fuel economy
of the Peugeot 504 and Mercedes 240D are indicated as separate data
points. The Peugeot and Mercedes are the only Diesel-powered vehicles
in the 3500 Ib. inercia class certified for 1976.
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Tables I-III following the text of this report contain individual test
data for the '75 FTP, HFET and steady state tests.
The acceleration time from 0-60 mph (average of A runs) is 26.0 seconds.
For comparison, the acceleration time from 0-60 mph for a Mercedes 240D
is approximately 23 seconds.
Conclusions
1. The Citroen Diesel demonstrated exhaust emissions below the levels
required by the 1977 Federal emission standards. The emissions of the
Citroen are similar to those of other Diesel-powered passenger cars
tested by EPA. It should be noted that the Citroen had accumulated only
130 miles at the conclusion of the test program. Further testing would
be required to verify that the exhaust emissions do not exceed allowable
levels as mileage is accumulated. Federal regulations require that new
vehicles meet applicable emission standards for 50,000 miles.
2. The fuel economy of the Citroen Diesel is average for Diesel-powered
passenger cars in the 3500 Ib. weight class. The fuel economy is superior
to vehicles powered by spark-ignition engines, of the same weight class.
3. The acceleration capabilities of the Citroen Diesel are similar to
other Diesel-powered vehicles in its weight class.
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45
40
City/Hwy
Combined
en
Q.
O
C
O
(J
OJ
3
35
30
15
10
o—1976 Peugeot 504
0^-Citroen Diesel
o—1976 Mercedes 240D
1976 Certification Data
Sales Weighted Average
Range of 1976
Certification
Data (excluding
Vehicles)
u -
2000 2500 3000 3500 4000 4500
Inertia Weight, pounds
Figure 1: Fuel Economy Comparison
5000 5500
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5
Table I
1975 Federal Test Procedure
mass emissions in
grains per mile
(grams per kilometer)
miles/gal
Test //
77-2837
77-2845
Average
EC
0.40
(0.25)
0.39
(0.24)
0.40
(0.25)
CO
1.7
(1.1)
1.8
(1.1)
1.8
(1.1)
co2
396.
(246.)
416.
(259.)
406
(253.)
NO
X
1.46
(0.91)
1.61
(1.00)
1.54
(0.96)
(liters/K
25.5
(9.2)
24.2
(9.7)
24.9
(9.5)
Table 11
Highway Fuel Economy Test
mass emissions in
grams per mile
(grams per kilometer)
miles/gal
Test I
77-2839
77-2841
Average
HC
0.16
(0.10)
0.16
(0.10)
0.16
(0.10)
CO
0.7
(0.5)
0.7
(0.5)
0.7
(0.5)
co2
317.
(197.)
314.
(195.)
316.
(196.)
NO
X
1.44
(0.90)
1.48
(0.92)
1.46
(0.91)
(liters/1
31.9
(7.4)
32.2
(7.3)
32.1
(7.4)
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Table III
HC
idle(300 sees) 0.63 gms
15 (24 kph) 0.71
(0.44)
30 mph(48kph) 0.35
(0.22)
45 mph(72kph) 0.23
(0.14)
60 mph(97kph) 0.13
(0.08)
Steady State
Mass emissions In
grams per mile
(grams per kilometer)
miles/gal.
CO
1.6 gms
3.7
(2.3)
2.0
(1.2)
1.0
(0.6)
0.6
(0.4)
co2
142. gms
475.
(295.)
390.
(242.)
370.
(230.)
345.
(214.)
NO (1
X
0.46 gms
1.43
(0.89)
1.58
(0.98)
1.85
(1.15)
1.56
(0.97)
Iters/lOOtan
21.1
(11.1)
25.9
(9.1)
27.4
(8.6)
29.4
(8.0)
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TEST VEHICLE DESCRIPTION
Chassis model year/make - 1976 Citroen Pallas ex
Emission control system - Engine Modifications
Engine
type 4 stroke,Diesel Cycle, 1-4,ohv
bore x stroke 3.66 x 3.62 in./93 x 92 mm
displacement . 153 cu in./2500cc
compression ratio .... 22.3: 1
maximum power 7.5 bhp
fuel metering mechanical fuel injection
fuel requirement . . . # 2 Diesel
Drive Train
transmission type 4 speed manual
Chassis
type ..... . Front engine, front wheel drive
tire size ' 185 R x 14
inertia weight 3500 Ibs.
passenger capacity 4
Emission Control System
basic type Engine modifications
durability accumulated on system . 120 mi/200 km
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