76-9 AW
Exhaust Emissions and Fuel Economy
from a Light-Duty Diesel Vehicle
Running on Diesel Fuel
and Wide Boiling Range Fuel
December 1975
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 U.S. Environmental Protection Agency is currently interested in
the feasibility of using the Diesel engine as a powerplant for light-
duty vehicles. Because Diesel-powered vehicles can be run on different
grades of commercial Diesel fuels, an EPA test program was set up to
measure the exhaust emissions from a light-duty Diesel vehicle when run
on two common Diesel fuels.
The two fuels used in the program were #1 and #2 Diesel fuel. Both
fuels meet the EPA specifications for EPA Diesel test fuel. In addition,
a third fuel developed by Texaco, Inc. was tested. This fuel, referred
to as 100-600 fuel, was developed..by Texaco to optimize what they call
the Vehicle-Fuel-Refinery System. Essentially, they have attempted to
maximize the miles of transportation that can be obtained from a barrel
of crude oil. The 100-600 fuel is intended for use in a vehicle equipped
with a Texaco controlled combustion system. However, a light-duty
Diesel engine can also run on this fuel. Some specifications for each
fuel are given in Table IV.
It was expected that the fuel cetane number would have the greatest
effect on exhaust emissions, and that fuel consumption would be proportional
to API gravity. The cetane number is an indication of the ignition
quality of Diesel fuel. API gravity is an inverse function of the
specific gravity.
Low cetane fuels are associated with high emissions of hydrocarbons
(HC) and oxides of nitrogen (NOx). Engine combustion noise may also be
high. Fuels with a high cetane number should cause lower HC and NOx
emissions, lower engine noise, and improved starting. However, if an
engine starts and runs well on a given fuel, increasing the cetane
number of the fuel may not appreciably improve starting, emissions, or
engine noise levels. The magnitude of the cetane effect is influenced
by engine configuration.
Fuel consumption can be expected to be proportional to API gravity
because a fuel with a high API gravity contains less energy per gallon
than a fuel with a low API gravity.
The conclusions from the EPA evaluation test reported here can be
considered to be quantitatively valid only for the specific test car
used. However, it is reasonable to extrapolate the results from this
test to other vehicles in a directional or qualitative manner, i.e., to
suggest that similar results are likely to be achieved on other similar
vehicles.
Tierney, Johnson and Crawford, "Energy Conservation, Optimization
of Vehicle-Fuel-Refinery System," SAE paper 750673.
Broering and Holtman, "Effect of Di<
and Performance," SAE paper 740692.
2
Broering and Holtman, "Effect of Diesel Fuel Properties on Emissions
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Test Vehicle Description
The vehicle used in the test program was a Nissan 220C 4-door sedan
powered by a four cylinder, 132.1 cu in./2165 cc Diesel engine with an
output of 70 bhp/52.2 kW. . The engine operates on a four-stroke cycle
and has a prechamber type of combustion chamber. Engine and chassis
statistics are listed on the test vehicle description sheet at the end
of the report.
Test Program
Exhaust emissions and fuel economy were measured in accordance with
the 1975 Federal Test Procedure ('75 FTP) for light-duty Diesel vehicles,
and over the EPA Highway Cycle. Due to an equipment malfunction, hydro-
carbon emissions were not measured using a heated flame ionization
detector and heated sample line, although CVS measurements of hydrocarbon
emissions were made. However, when Diesel exhaust is collected in
sample bags (as it is in the CVS procedure), a portion of the heavier
hydrocarbon molecules will condense on the walls of the sample bags.
Consequently, measurement of hydrocarbon emissions based on the contents
of the CVS sample bag will result in lower apparent hydrocarbon emissions
than are actually emitted from the test vehicle. Thus in this report,
the CVS measured hydrocarbon emissions indicate only relative changes in
emission levels and not absolute emission values.
Six emission and fuel economy tests were run on the test vehicle,
two tests on each of the three test fuels.
Test Results
The exhaust emissions for each of the three test fuels are summarized
in the following tables:
#2 Diesel fuel
#1 Diesel fuel
100-600 fuel
'75 FTP Composite Mass Emissions
grams per mile
(grams per kilometer)
CV§
HC
0.22
(0.14)
0.19
(0,12)
0.44
(0.27)
CO
1.43
(0.89)
1.50
(0.93)
1.94
(1.21)
NOx
1.53
(0.95)
1.42
(0.88)
1.46
(0.91)
Fuel Economy
(Fuel Consumption)
27.0 miles/gal.
(8.7 liters/100 km)
26.7 miles/gal.
(8.8 liters/100 km)
25.3 miles/gal.
(9.3 liters/100 km)
HC data are cold FID bag data which are approximately one half the
value of hot FID continuous measurements used in the standard FTP
for Diesel-powered light duty vehicles.
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EPA Highway Cycle
Mass Emissions in
grams per mile
(grams per kilometer)
CV§ Fuel Economy
HC CC) NOx (Fuel Consumption)
#2 Diesel fuel 0.07 0.75 1.27 33.6 miles/gal.
(0.04) (0.47) (0.79) (7..0 liters/100 km)
#1 Diesel fuel 0.10 0.88 1.28 33.2 miles/gal.
(0.06) (0.55) (0.80) (7.1 liters/100 km)
100-600 fuel 0.22 1.38 1.26 32.4 miles/gal.
(0.14) (0.86) (0.78) (7.3 liters/100 km)
*
HC data are cold FID bag data which are approximately one half
the value of hot FID continuous measurements used in the standard
FTP for Diesel-powered light duty vehicles.
Both Diesel fuels produced about the same exhaust emissions and
fuel economy. Differences were within nprmal test variability.
The relatively low cetane 100-600 fuel produced higher emissions
of HC and CO than either Diesel fuel. HC emissions increased 36% during
the '75 FTP and 84% over the Highway Cycle. NOx emissions were slightly
lower for the 100-600 fuel during the '75 FTP when compared to #2
Diesel fuel.
Fuel consumption was proportional to API gravity, with #2 Diesel
giving the lowest fuel consumption and the 100-600 fuel giving the
highest fuel consumption.
The test vehicle started and idled well on both Diesel fuels,
but the 100-600 fuel caused hard starting and poor idle quality. Engine
combustion noise was high for the 100^-600 fuel.
Conclusions
There was very litttle difference in emissions and fuel economy
when running on either #1 or #2 Diesel fuel. The differences measured
were within normal test variability. The 100-600 fuel caused increased
emissions of HC and CO, a reduction in fuel economy, and no change in
oxides of nitrogen emissions.
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As expected, HC emissions increased with decreasing cetane number.
However, NOx emissions did not increase with decreasing cetane number.
NOx emissions from the low cetane 100-600 fuel were lower than NOx
emissions from the higher cetane #2 Diesel.
It is possible that the test vehicle could be optimized to improve
exhaust emissions and fuel economy when running on the 100-600 fuel.
However, the data indicate that some deterioration in exhaust emissions
and fuel economy can be expected if the 100-600 fuel was to be substituted
for the types of Diesel fuel currently being used in light-duty Diesels.
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Table I
1975 Federal Test Procedure
Mass Emissions in
grams per mile
(grams per kilometer)
Test #
HC
CO
CO,
NOx
mpg (liters/100 km)
#2 Diesel fuel
16-1786
16-1788
Average
#1 Diesel fuel
15-1784
15-1785
Average
100-600 fuel
15-1815
16-1787
Average
0.21
(0.13)
0.22
(0.14)
0.22
(0.14)
0.19
(0.12)
0.18
(0.11)
0.19
(0.12)
0.42
(0.26)
0.45
(0.28)
0.44
(0.27)
1.43
(0.89)
1.43
(0.89)
1.43
(0.89)
1.51
(0.94)
1.48
(0.92)
1.50
(0,93)
1.88
(1.17)
2.00
(1.24)
1.94
(1.21)
T
379.
(236.)
370.
(230.)
375.
(233.)
359.
(223.)
363.
(226.)
361.
(224.)
371.
(231.)
374.
(232.)
373.
(232.)
1.53
(0.95)
1.53
(0.95)
1.53
(0.95)
1.40
(0.87)
1.44
(0.90)
1.42
(0.88)
1.47
(0.91)
1.44
(0.90)
1.46
(0.91)
26.7
(8.8)
27.3
(8.6)
27.0
(8.7)
26.8
(8.8)
26.5
(8.9)
26.7
(8.8)
25.4
(9.3)
25.2
(9.3)
25.3
(9.3)
HC data are cold FID bag data which are approximately one half
the value of hot FID continuous measurements used in the standard
FTP for Diesel-powered light duty vehicles.
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Test //
#2 Diesel fuel
16-1786
16-1788
Average
# 1 Diesel fuel
15-1784
15-1785
Average
100-600 fuel
15-1815
16-1787
Average
HC
Table II
EPA Highway Cycle
Mass Emissions in
grains per mile
(grams per kilometer)
CO
CO,
NOx
mpg (liters/100 km)
0.07
(0.04)
0.07
(0.04)
0.07
(0.04)
0.09
(0.06)
0.10
(0.06)
0.10
(0.06)
0.21
(0.13)
0.22
(0.14)
0.22
(0.14)
0.78
(0.48)
0.71
(0.44)
0.75
(0.47)
0.86
(0.53)
0.89
(0.55)
0.88
(0.55)
1.34
(0.83)
1.41
(0.88)
1.38
(0.86)
— r
302.
(188.)
302.
(188.)
289.
(180.)
292.
(181.)
291.
(181.)
295.
(183,)
287.
(178.)
291.
(181.)
1.33
(0.83)
1.20
(0.75)
1.27
(0.79)
1.27
(0.79)
1.28
(0.80)
1,28
(0.80)
1.30
(0.81)
1.22
(0.76)
1.26
(0.78)
33.6
(7.0)
33.6
(7.0)
33.3
(7.1)
33.1
(7.1)
33.2
(7.1)
32.0
(7.4)
32.8
(7.2)
32.4
(7.3)
HC data are cold FID bag data which are approximately one half the value
of hot Flp continuous measurements used in the standard FTP for Diesel-
powered light duty vehicles.
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Table III
Individual Bag Emissions in Grains per Mile
Test Number
HC
CO
Cold Transient
C00 NOx MPG
A Bag 2: Stabilized
HC CO CO,, NOx MPG
*Bag 3: Hot Transient
HC CO CO,, NOx MPG
#2 Diesel Fuel
16-1786
16-1788
//I Diesel Fuel
15-1784
15-1785
100-600 Fuel
15-1815
16-1787
0.20
0.21
0.21
0.19
0.83
0.87
1.42
1.43
1.60
1.48
1.75
1.77
— x-
411.
392.
407.
391.
396.
402.
1.68
1.60
1.51
1.51
1.57
1.54
24.6
25.8
23.6
24.6
23.7
23.4
0.22
0.24
0.18
0.17
0.32
0.35
1.54
1.56
1.57
1.58
2.07
2.21
— f
374.
369.
348.
367.
370.
374.
1.55
1.56
1.38
1.48
1.46
1.44
27.0
27.3
27.7
26.2
25.5
25.2
0.18
0.19
0.17
0.18
0.31
0.31
1.23
1.20
1.32
1.31
1.63
1.77
— f
364.
354.
344.
336.
354.
352.
1.41
1.41
1.33
1.31
1.41
1.36
27.8
28.6
28.0
2ff.7
26.6
26.8
HC data are cold FID bag data which are approximately one half the value of hot FID
continuous measurements used in the standard FTP for Diesel-powered duty vehicles.
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Table IV
Fuel Specifications
#1 Diesel
#2 Diesel
100-600
Gravity, API
Cetane Number
Sulfur % (wt.)
% Carbon
% Hydrogen
Distillation, °F ASTM
IBP
10%
20%
30%
40%
50%
60%
70%
80%
90%
EP
42.5
46.0 (approx.)
.076
85.9
13.8
325
363
382
395
408
421
435
452
471
501
538
35.0
45.5 (approx.)
0.27
86.0
13.3
352
396
422
442
463
484
502
522
545
573
580
46.1
34.8
86.3
13.7
121
225
283
334
379
421
461
491
532
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TEST VEHICLE DESCRIPTION
Chassis model year/make - 1973 Nissan 220C
Emission control system - None
Engine
type 4 stroke, Diesel, 1-4, ohv, indirect injection
bore x stroke 3.47 x 3.90 in./88.1 x 99.1 mm
displacement 133 cu in./2170 cc
compression ratio . 22:1
maximum power @ rpm 70 bhp @ 4000 rpm/52.2 kW @ 4000 rpm
fuel metering Fuel injection, mechanical
fuel requirement #2 Diesel fuel .
Drive Train
transmission type 4 speed manual
final drive ratio 3.91:1 (approximate)
Chassis
type Front engine, rear wheel drive \
tire size* ....... '. '.'.'.'. 175 SR x 14
curb weight 300° lbs/1415 kg
inertia weight 350° lbs
passenger capacity . ^
durability accumulated 6800 miles/11000 km
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