EPA-AA-TAEB 76-15
Exhaust Emissions and Fuel Economy
of a Diesel-Powered Postal Van
March 1976
Technology Assessment and Evaluation Branch
Emission Control Technology Division
Off Lee of Mobile Source Air Pollution Control
Environmental Protection Agency
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Background
The Environmental Protection Agency receives information about many
systems which appear to offer potential for emission reduction or fuel
economy improvement compared to conventional engines and vehicles.
EPA's Emission Control Technology Division is interested in evaluating
all such systems, because of the obvious benefits to the Nation from the
identification of systems that can reduce emissions, improve fuel economy,
or both.
If a system demonstrates the ability to improve fuel economy or
reduce exhaust emissions, EPA will attempt to schedule confirmatory
tests at the EPA Emission Laboratory at Ann Arbor, Michigan. The results
of all such test projects are set forth in a series of Technology Assess-
ment and Evaluation Reports, of which this is one.
The conclusions drawn from the EPA evaluation tests are necessarily
of limited applicability. A complete evaluation of the effectiveness of
an emission control system in achieving performance improvements on the
many different types of vehicles that are in actual use requires a much
larger sample of test vehicles than is economically feasible in the
evaluation test projects conducted by EPA. For promising systems it is
necessary that more extensive test programs be carried out.
The conclusions from the EPA evaluation test can be considered to
be quantitatively valid only for the specific test car used, however, it
is reasonable to extrapolate the results from the EPA test to other
types of vehicles in a directional or qualitative manner, i.e., to
suggest that similar results are likely to be achieved on other types of
vehicles.
At the request of the EPA, the U.S. Postal Service agreed to make
available for EPA tests a Postal Delivery Van powered by a Diesel engine.
Data obtained from the Postal Service indicated a substantial improve-
ment in fuel economy over the standard Postal Van which is powered by a
gasoline-fueled, spark ignition engine.
Based on past experience with light-duty Diesel vehicles, it was
expected that the exhaust emissions from the uncontrolled Diesel Postal
Van would probably be lower than the emissions from the comparable Otto
cycle Postal Van (controlled to 1975 Federal Emission Standards).
Test Vehicle Description
The test vehicle is a 1975 AM General Postal Delivery Van. The
vehicle has a conventional powertrain layout, with a front-mounted
engine and rear wheel drive. The steering is on the right side.
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Seating is provided only for the driver; the remainder of the interior
space is for carrying parcels. The vehicle was tested -at an inertia ;
weight of 3000 Ibs.
The engine is a 4-cylinder Perkins Diesel engine, with a cast iron
block and Perkins "H" combustion system (prechamber type). The displace-
ment of the engine is 165 cu. in. (2700cc). For cold starting at low
ambient temperatures, a measured amount of starting fluid is injected
into the intake manifold by pushing a button on the dashboard. No glow
plugs are fitted.
The transmission is a Chrysler 3-speed automatic. The final drive
ratio is 3.07:1.
Engine and vehicle characteristics are listed on the Test Vehicle
Description sheet at the end of this report.
Test Program
A series of tests were run on the Postal Van to characterize ex-
haust emissions and fuel economy. Exhaust emission tests were conducted
according to the 1975 Federal Test Procedure ('75 FTP) for light-duty
Diesel vehicles (Federal Register, October 22, 1974, Vol. 39 No. 205,
Part III). In addition to the '75 FTP, testing included the EPA Highway
Fuel Economy Test (HFET), the EPA Sulfate Cycle (SC-7), steady states,
and measurement of acceleration times.
A brief description of the sulfate test sequence is given on page
10. A more complete sulfate test description can be found in SAE publica-r
tion Number 760034 titled "Sulfuric Acid Emissions from Light Duty Vehicles".
The fuel used for the sulfate tests as well as the other emission tests
was #2 Diesel fuel containing 0.21 wt.% sulfur.
Steady state emissions and fuel economy were measured at idle, 15,
30, 45 and 60 mph. • •• .
Test Results'
The following exhaust emissions and fuel economy were measured
according to the 1975 Federal Test Procedure.
'75 FTP Mass Emissions in
grams per mile
(grams per kilometer)
Fuel Economy
HC CO NOx (Fuel Consumption)
Average of 0.30 1.30 2.41 30.1 miles/gal.
2 tests (0.19) (0.81) (1.50) (7.8 liters/lOOkm)
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The exhaust emissions are within the 1976 interim Federal Emission
Standards for light duty trucks (HC-2.0 gpm, CO-20 gpm, NOx-3.1 gpm) for
light duty trucks.
Exhaust emissions and fuel economy measured during the EPA Highway
Fuel Economy Test are presented in the following table.
EPA Highway Fuel Economy Test
Mass Emissions in
grams per mile
(grams per kilometer)
Fuel Economy
HC CO NOx (Fuel Consumption)
Average of 0.33 1.03 2.20 37.7 miles/gal.
3 tests (0.21) (0.64) (1.37) (6.2 liters/lOOkm)
Sulfuric acid emissions measured over the EPA Sulfate Cycle are
presented in Table V, along with sulfuric acid emissions measured from
other light-duty Diesel vehicles tested by EPA.
Steady state emissions and fuel economy are presented in Table IV.
It should be noted that steady state driving is not representative of
real-world driving conditions. Steady state emission tests are conducted
to give insight into the operational differences and exhaust emission
and fuel economy variations among different vehicles.
Acceleration tests gave an average time to accelerate from 0 to 60
mph of 20.6 seconds.
Conclusions
Compared to the standard 1975 Postal Van (powered by a spark
ignition, gasoline-fueled engine), the Diesel-powered Postal Van de^
monstrated lower exhaust emissions (except NOx) and higher fuel economy
with some loss in performance. The following table contains the cer-
tification results for the 1975 gasoline-engine Postal Van.
'75 FTP Mass Emissions in
grams per mile
(grams per kilometer)
Fuel Economy
HC CO NOx (Fuel Consumption)
1.1 17. 1.7 17 miles/gal.
(0.68) (10.6) (1.1) (13.8 liters/lOOkm)
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The Highway fuel economy for the gasoline vehicle was 24 miles/gal.
(9.8 liters/lOOkm). .
The gasoline-engine Postal Van was tested at an inertia weight of
2750 Ibs. Data submitted by the Post Office indicates that the gasoline-
engine vehicle accelerates from 0-55 mph in 14.5 seconds with a payload
of 700 Ibs. This contrasts with an acceleration time from 0-60 mph of
20.6 seconds for the Diesel Postal Van with only a driver (about 150
Ibs).
Sulfuric acid emissions from the Diesel Postal Van are similar to
those measured from other light-duty Diesel vehicles.
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TEST VEHICLE DESCRIPTION
Chassis model year/make - 1975 AM General Postal Van
Emission control system - None
Engine
type 4 stroke, Diesel,1-4, ohv, indirect injection
bore x stroke 3.62 x 4.00 in./92 x 101.6mm
displacement 165 cu. in./2700cc
compression ratio . 21:1
maximum power @ rpm . 70 bhp at 3600 rpm/52.2kW at 3600 rpm
fuel metering mechanical fuel injection
fuel requirement . #2 Diesel fuel
Drive Train
transmission type 3 speed automatic
final drive ratio 3.07:1
Chassis
type . . Front engine, rear wheel drive
tire size CR78 x 15 M&S
curb weight 2736 lbs/1241 kg
inertia weight 3000 Ibs.
passenger capacity . one
Emission Control System
basic type . none
durability accumulated on system. . 100 miles/161 km.
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Table I
1975 Federal Test Procedure
Mass Emissions In
grams per mile
(grams per kilometer)
miles/gallon
Test #
77-633
77-635
77-692
Average
0.30
(0.19)
0.29
(0.18)
0.30
(0.19)
HC
0.34
(0.21)
0.34
(0.21)
0.32
(0.20)
0.33
(0.21)
1.29 335. 2.41
(0.80) (208.) (1.50)
1.30 335. 2.41
(0.81) (208.) (1.50)
1.30 335. 2.41
(0.81) (208.) (1.50)
Table II
EPA Highway Driving Cycle
Mass Emissions in
grams per mile
(grams per kilometer)
CO C02 NOx
1.09 267. 2.11
(0.68) (166.) (1.31)
0.99 268. 2.21
(0.62) (167.) (1.37)
1.01 269. 2.29
(0.63) (167.) (1.42)
1.03 268. 2.20
(0.64) (167.) (1.37)
miles/gallon
(liters/100 kilometers)
37.8
(6.2)
37.7
(6.2)
37.5
(6.3)
37.7
(6.2)
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Table III
Individual Bag Emissions in
grams per mile
Bag 2: Stabilized Bag 3: Hot Transient
Test 0
77-634
77-659
A
HC
0.33
0.31
«»6 i..
CO
1.45
1.51
C02
374.
380.
NOx
2.66
2.75
MPG
27.0
26.5
HC
0.26
0.26
CO "
1.24
1.27
C02
325.
322.
NOx
2.35
2.32
MPG
31.1
31.3
HC CO C02 NOx MPG
0.36 1.28 323. 2.35 31.2
0.33 1.19 323. 2.33 31.2
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Table IV
Steady State Mass Emissions in
grams per mile
(grams per kilometer)
Idle/300 sec.
15mph/24kph
30mph/48kph
45mph/72kph
60mph/97kph
HC
0.19gms
0.10
(0.06)
0.31
(0.19)
0.23
(0.14)
0.15
(0.09)
CO
0.91gms
0.80
(0.50)
1.23
(0.76)
0.88
(0.55)
0.77
(0.48)
co2
262. gms
208.
(129.)
201.
(125.)
231.
(144.)
283.
(176.)
NOx
2.08gms
1.61
(1.00)
1.20
(0.75)
1.71
(1.06)
2.61
(1.62)
mpg (1/100
48.5
(4.9)
50.0
(4.7)
43.6
(5.4)
35.8
(6.6)
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Table V
EPA Sulfate Cycle
Sulfuric Acid Emissions in
milligrams per mile
H-SO, % Conversion of
Emissions Fuel Sulfur to SO&
10.8 1.7
10.3 1.7
10.6 1.7
8.7 1.4
Average 10.1 1.6
Comparative Data:
Volkswagen Diesel-powered Rabbit
Average of
8 tests 9.4 2.4
Diesel-powered Ford Pinto
Average of
8 tests 8.6 1.8
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10
Diesel Postal Van
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.
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