United States
Environmental Protection
Agency
Atmospheric Sciences Research
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S3-84-104 Dec. 1984
Project Summary
Characterization of Heavy-Duty
Motor Vehicle Emissions Under
Transient Driving Conditions
Mary Ann Warner-Selph and Harry E. Dietzmann
The objective of this program was to
characterize heavy-duty diesel truck
and bus emissions produced during
transient driving cycles. In the initial
phase of the program an improved road-
load simulation method was developed
for use in operating large trucks on a
chassis dynamometer. This method
was used in testing vehicles on the
chassis dynamometer in the latter parts
of the program. The second phase of
testing involved operation of six vehicles
on the chassis dynamometer (over the
chassis version of the heavy-duty trans-
ient cycle), removal of the engine and
testing of the engines (over the heavy-
duty engine transient cycle). Chassis
emisisons were then compared to en-
gine emissions. Additionally, chassis
tests were conducted over a range of
dynamometer inertia settings for two of
the six vehicles for the purpose of
comparison with engine emissions.
Baseline emissions were also measured
on six buses, five single-axle tractors,
and 17 dual-axle tractors over the chassis
version of the transient cycle. Regulated
emissions and several unregulated emis-
sions were measured on baseline tests.
Unregulated emissions included partic-
ulate, aldehydes and ketones, phenols,
DOAS odor, various elements, nitro-
pyrenes, and Ames mutagenic re-
sponse.
This Project Summary was developed
by EPA's Atmospheric Sciences Re-
search Laboratory, Research Triangle
Park, NC, to announce key findings of
the research project that is fully docu-
mented in a separate report of the same
title (see Project Report ordering
information at back).
Introduction
This project was divided into three
tasks. The objective of the first task of
testing was to determine the appropriate
amount of power to be absorbed by a
chassis dynamometer to simulate on-
road driving conditions. The work per-
formed in the first task involved three
vehicles, a city bus, a single-axle truck
tractor, and a tandem-axle truck tractor.
Coastdowns were conducted on the road
for each vehicle under essentially ideal
weather conditions (primarily no wind)
and with zero road grade. Coastdowns
were also conducted on the chassis
dynamometer with the single-axle tractor
and the bus. Results of these determina-
tions, along with data reported in the
literature, were used to determine the
power to be absorbed by a chassis
dynamometer.
The objectives of the second task were
to determine repeatability of HC, CO, COZ,
NO,, and particulate emissions in chassis
cycle and engine cycle tests and whether
there is correlation between engine cycle
and chassis cycle emissions. This task
involved five sets of tests with four
vehicles over a chassis version of the
transient cycle for heavy-duty vehicles
and with their respective engines over
the 1984 transient test for heavy-duty
engines.
The test vehicles included a city bus
powered by a 1 982 Detroit Diesel 6V-71,
two dual-axle tractors, one with a 1980
Cummins Formula 350 and one with a
1980 Detroit Diesel 8V-92TA, and a
single-axle tractor equipped with a 1979
IHC DT-466. Two additional vehicles
underwent two sets of chassis and engine
-------
tests. These vehicles were also tested at
several different inertia settings over the
chassis transient cycle to determine the
effect of inertia on emissions. Regulated
emissions (HC, CO, C02, and NOX) and
participate were measured for all chassis
and engine transient tests. The city bus
was tested using a DF-1 Emissions Test
Fuel (EM-400-F) and the three tractors
were tested with a DF-2 Certification Fuel
(EM-528-F).
The objective of the third task was to
measure HC, CO, C02, NOX, paniculate
and several unregulated emissions during
chassis testing of four single-axle trac-
tors, fifteen dual-axle tractors, and five
buses. Each vehicle was operated over a
minimum of two duplicate transient cy-
cles. The buses were tested with a DF-1
Emissions Test Fuel (EM-455-F), and the
tractors were tested with a DF-2 Certi-
fication Fuel(EM-528-F).The unregulated
emissions that were measured included
aldehydes and ketones, DOAS odor,
various elements, and organic solubles.
In addition, Ames bioassay and nitro-
pyrene analyses were performed on the
organic soluble samples.
Procedures
Dynamometers and CVS
Systems
Transient engine testing was performed
in accord with the 1984 Transient test for
Heavy-Duty Diesel Engines. The proce-
dure specifies transient engine operation
over variable speed and load, the magni-
tude of the load depending on the power
output capability of the test engine. The
cycle requires relatively rapid dynamom-
eter control, that is, the capability to load
the engine one moment and motor it the
next. The system used in this program
consisted of a GE 200 hp motoring/250
hp absorbing dynamometer coupled to a
Midwest 500 hp eddy current (absorbing)
dynamometer, with a suitable control
system fabricated in-house.
Engine transient testing of Engine 2-1
was conducted using a double-dilution
constant volume sampler (CVS) with the
main dilution tunnel flow set at 1100
CFM. Engines 2-2, 2-3, and 2-4 were
operated with a main dilution flow of
1900 CFM. This provided a dilution ratio
of roughly 4:1 in the primary tunnel and
12:1 in the secondary tunnel. Secondary
tunnel sample flowrates were about 1
CFM for all engine transient tests.
Chassis transient operation was con-
ducted in general accord with the EPA
Recommended Practice for determining
exhaust emissions via the chassis version
of the Transient Cycle. Vehicle testing
was performed on a tandem drive dyna-
mometer equipped with two air-gap 350
hp eddy current power absorbers and
with inertia wheels directly connected to
each set of rolls. A speed vs load curve,
simulating road-load horsepower, was
programmed into the system using a load
control circuit.
A single dilution CVS with maximum
capacity of 12,000 cfm was used with
vehicles tested on the chassis dynamom-
eter. The CVS was set at flow rates
ranging from 4000 to 9000 cfm, depend-
ing on engine horsepower and ambient
temperature.
Driving Cycles
Vehicle testing involved vehicle opera-
tion over three different driving cycles:
the 1984 Transient FTP for Heavy-Duty
Diesel Engines, the "Recommended Prac-
tice for Determining Exhaust Emissions
from Heavy-Duty Vehicles Under Trans-
ient Conditions," and the New York Bus
Cycle.
The 1984 engine transient cycle is
described in the Federal Register by
percent of maximum torque and percent
of rated speed for each one-second
interval, for a test cycle of 1199 seconds
duration. This 20-minute transient cycle
is composed of four five-minute seg-
ments. The four segments are described
as follows:
Engine Transient Cycle
Segment Time, sec
New York Non-Freeway 297
(NYNF)
Los Angeles Non-Freeway 300
(LANF)
Los Angeles Freeway (LAP) 305
New York Non-Freeway 297
(NYNF)
The chassis transient test is composed
of a cold-start cycle followed by a 20-
minute soak period and then a hot-start
cycle. On the day preceding testing the
vehicle is propped by driving through the
chassis transient test. The vehicle is then
allowed to stand overnight prior to the
cold-start. The transient cycle is com-
posed of four segments which are des-
cribed as follows:
Chassis Transient Cycle
Segment Time, sec
New York Non-Freeway
(NYNF)
254
Los Angeles Non-Freeway 267
(LANF)
Los Angeles Freeway (LAP) 285
New York Non-Freeway 254
(NYNF)
One chassis transient cycle is a total of
1060 seconds, or approximately 18 min-
utes. Although engine and chassis trans-
ient cycles are quite similar in most
respects, differences in cycle lengths
exist because of inherent differences in
the chassis and engine test procedures.
Another driving cycle used in testing of
buses in Task 3 was the New York Bus
Cycle. This experimental driving cycle
was developed from a CAPE-21 study of
several buses during in-service operation.
Of the 1191 seconds duration of the
cycle, 394 seconds are idle. The distance
covered by the test is 2.90 miles and the
maximum speed called for by the cycle is
36 mph.
Unregulated Emissions
Phenols
Phenols were sampled by bubbling
dilute exhaust at 0.8 ftVmin through
glass impingers containing a chilled
aqueous solution of 1 N potassium hydrox-
ide. The samples were acidified, extracted
with ether, and concentrated. Samples
were analyzed on a gas chromatograph
equipped with a flame ionization detector.
This procedure analyzes for phenol, sali-
cylaldehyde, m-cresol/p-cresol, p-ethyl-
phenol/2-isopropylphenol/2,3-xylenol/
3,5-xylenol/2,4,6-trimethylphenol, 2,3,5-
trimethylphenol, and 2,3,5,6-tetramethyl-
phenol.
Aldehydes and Ketones
Two variations of the 2,4-dinitrophenyl-
hydrazme (DNPH) method were used in
the analysis of aldehydes and ketones.
The first method involved sampling dilute
exhaust at 4 lit/min through an aqueous
2N HCI scrubber solution of DNPH. The
samples were filtered, extracted with
pentane, and analyzed on an HPLC. The
compounds measured were formalde-
hyde, acetaldehyde, acrolein, propional-
dehyde, acetone, crotonaldehyde, isobu-
tyraldehyde, methylethylketone, benzal-
dehyde, and hexanaldehyde. This pro-
cedure was used for Vehicles 3-1 through
3-7.
An improved version of the 2,4-DNPH
method was used to analyze samples
from Vehicles 3-8 to 3-24. Dilute exhaust
was bubbled through a solution of DNPH
in acetonitrile spiked with 1N perchloric
-------
acid. A portion of the sample was analyzed
by direct injection into an HPLC. The
same aldehydes and ketones were meas-
ured with this method as with the original
procedure, however, isobutyraldehyde
and methylethylketone elute at the same
retention time.
DOAS Odor
Dilute exhaust was sampled at approx-
imately 2.8 lit/min for odorants using
stainless steel traps packed with Chromo-
sorb 102. Two traps were positioned in
series for each sample taken. Samples
were eluted from the traps with cyclo-
hexane and a portion of each sample was
analyzed on the Diesel Odor Analysis
System (DOAS), a liquid chromatograph.
Elements
Paniculate samples were collected on
47 mm Pallflex filters. The particulate
from these filters was analyzed for several
elements at EPA-RTP using a Siemens
Model MRS-3 high resolutionx-rayfluor-
escence multispectrometer.
Solvent Extraction of Particulate
Filters
Particulate was also sampled on 20x20
inch Pallflex filters. These filters were
Soxhlet extracted with methylene chlor-
ide for 8 hours at 4 cycles/hour and the
resulting extractables were analyzed for
nitropyrenes and for mutagenic activity
(Ames Bioassay).
Nitropyrenes
Nitropyrenes were measured using a
method developed by the EPA in which
the samples were analyzed on a liquid
chromatograph coupled to a fluorescence
detector. Each organic extractable sample
was dissolved in a 50:50 mixture of
methylene chloride/methanol prior to
analysis. The liquid chromatograph is
equipped with four columns, two contain-
ing reduction catalyst, and two packed
with Zorbax ODS. The catalyst columns
remove oxidative compounds from the
solvent and convert nitropyrenes to the
highly fluorescent aminopyrenes. The
Zorbax ODS columns separate the com-
pounds in the sample. This procedure
analyzes for 1-nitropyrene and three
dinitropyrenes: 1,3-, 1,6-, and 1,8-dinitro-
pyrene.
Ames Bioassay
Organic extractables were analyzed for
mutagenic activity by the S. typhimurium
mutagenicity test (Ames test), in tester
strains TA1538, TA98, and TA100. The
samples were analyzed in triplicate for
mutagenic activity in the presence and
absence of the S9 external metabolic
activation system, Aroclor-induced rat
liver homogenate.
Results
The first task of vehicle testing involved
operation of six vehicles over the chassis
transient cycle, removal of the respective
engines, and subsequent engine opera-
tion over the engine transient cycle. The
emissions results from these tests are
summarized in Tables 1 and 2 in g/km
and g/kg fuel. Engine emissions in g/km
were calculated based on an engine cycle
equivalent distance of 10.3 km. This
value was determined by the EPA in
1978. Hydrocarbons (HC), carbon mon-
oxide (CO), oxides of nitrogen (NO,), and
particulate were measured and are re-
ported as composite values weighted 1 /7
cold-start and 6/7 hot-start. Vehicle 3-23
was inadvertently tested at 80 percent of
standard horsepower. All other vehicles
were tested at standard horsepower. HC
chassis emissions, in g/km, generally
exceeded engine emissions by 10 to 30
percent with the exception of Vehicle 2-1,
in which chassis HC was lower than
engine HC by 16 percent. Vehicle 3-23
emitted the highest level of chassis and
engine HC while Vehicle 2-4 produced
the lowest levels. Vehicle 2-1 had rela-
tively high chassis CO emissions, 21
g/km compared to the other vehicles, 2 to
6 g/km. NOX emissions from Vehicles 2-
2, 2-3, 2-4, and 3-24 chassis and engine
tests agreed within 11 percent. However,
NOX produced by Vehicle 2-1 during
chassis tests exceeded engine NOX by 65
percent while NOX from vehicle 3-23
chassis tests were 38 percent lower than
engine NO*. Vehicle 3-24 produced the
highest NOX levels of the six vehicles.
Particulate emissions from chassis tests
were generally higher th-n particulate
produced during engine testing (by 18 to
28 percent). Vehicle 2-3 produced nearly
equivalent amounts of particulate in
chassis and engine tests. Particulate
emissions from chassis tests of Vehicle
2-1 were double the amount of particulate
emissions from engine tests.
Engine and chassis emissions are also
reported on a fuel specific basis, in g/kg
fuel. The general trends observed be-
tween engine and chassis emissions
in g/km are similar. However, in about
half the measurements, the agreement
between engine and chassis emissions
improved when using fuel specific units
for reporting emissions.
Two of the six vehicles that were tested
over chassis and engine cycles were also
tested at several inertia weights over the
chassis transient cycle. Chassis transient
Table 1. Comparison of Emissions from Chassis and Engine Tests from Several Vehicles
Composite Emission Rate, g/km
Vehicle
Number
Vehicle
Description
HC
CO
NO,
Part.
Chassis Engine" Chassis Engine' Chassis Engine" Chassis Engine'
2-1 BusDD6V-71
2-2 Dual-Axle Cummins
Form. 350
2-3 Dual-Axle DD8V-92TA
2-4 Single-Axle IHC
DT-466
3-23 Single-Axle
Cummins NTC-300
3-24 Dual-Axle DD8V-92TA
1.74
2.06
1.72
1.15
3.16
1.62
2.08
1.88
1.34
1.00
2.80
1.36
21.4
5.56
2.24
2.82
3.70
4.67
5.92
4.39
4.33
2.62
5.55
6.66
108
14.3
13.4
891
8.99
17.6
6.56
13.7
15.1
8.31
14.6
187
1.28
0.97
0.87
0.78
1 19
1.35
0.63
0.82
0.89
0.64
093
1.14
"Engine transient emission rate based on an engine equivalent distance of 10.3 km.
-------
Table 2. Comparison of Fuel Specific Emissions from Chassis and Engine Transient Tests from
Several Vehicles (g/kg fuel)
Composite Emission Rate, g/kg fuel
Vehicle
Number
2-1
2-2
2-3
2-4
3-23
3-24
HC
Chassis
4.23
4.69
3.81
3.69
9.60
3.18
Engine
7.25
4.83
2.97
3.63
7.26
2.71
CO
Chassis
51.9
12.7
4.97
8.89
11.2
9.17
Engine
20.5
11.3
9.50
9.47
14.4
13.3
NO,
Chassis
26.4
32.7
29.8
281
27.2
34.4
Engine
22.8
34.6
33.2
30.1
37.9
372
Paniculate
Chassis
3.10
2.21
1.93
2.50
3.59
2.64
Engine
2.21
2.12
1.94
2.30
2.42
2.28
testing is usually conducted at 70 percent
of GVW. Vehicle 3-23, a single-axle
tractor, was tested at 61%, 70%, 80%,
and 93% of GVW. Vehicle 3-24, a dual-
axle tractor, was operated at 55%, 70%,
86%, and 97% of GVW. Emissions results
from these tests and from engine tests
are reported in Tables 3 and 4 in g/km
and in g/kg fuel, respectively. Vehicle 3-
23 C02 and NOX increased with increasing
inertia when measured in g/km. On a
fuel specific basis, however, C02 was
constant while NO* increased with in-
ertia. HC and particulate were not affected
by variations in inertia. For the dual-axle
tractor. Vehicle 3-24, CO, C02, and NOX
emissions (in g/km) increased as inertia
weight was added. On a fuel specific
basis, C02 remained constant and CO and
NOX increased. Similar to Vehicle 3-23,
HC and particulate did not vary with
inertia weight with the exception of fuel
specific HC, which decreased with in-
creased inertia.
There was no single inertia setting at
which chassis emissions were equivalent
to engine emissions. For some emissions,
chassis and engine emissions were never
equivalent. This occurred with Vehicle 3-
23. Chassis particulate emissions were
higher and CO, COj, and NOX emissions
were lower than engine emissions. For
Vehicle 3-24, chassis HC wfls greater
than engine HC and chassis CO and NOX
(in g/kg fuel) were lower than engine
emissions at all inertia settings.
Baseline emissions were measured on
six buses, five single-axle tractors, and 17
dual-axle tractors over a minimum of two
chassis transient cycles. Five of the six
buses were also tested over two cycles of
the New York Bus Cycle. Average baseline
emissions (in g/km and g/kg fuel) are
given in Table 5 for each vehicle type and
for buses tested over the Bus Cycle. As a
group, single-axle tractors produced rel-
atively high HC levels and relatively low
NO. and particulate. Dual-axle tractors
emitted relatively high C02 and NOX and
low HC and CO. Buses tested over the
Table 3. Comparison of Engine and Chassis Emissions from Vehicles 3-23 and 3-24 Measured at Several Inertia Settings (g/km)
Vehicle
Number
3-23"
3-24
Vehicle Description
Single-axle 1981
Cummins NTC-300
Dual-axle 1980
DD8V-92TA
Engine Emissions, g/km" Percent
HC CO COi NO," Part. of GVW
2.80 5.55 1211 14.6 0.93 61%
70%
80%
93%
1.36 6.66 1583 18.7 1.14 55%
70%
86%
97%
Chassis Emissions, g/km
HC
3.33
3.16
3.54
3 14
1 71
1.62
1.65
1.66
CO
3.79
3.70
4.15
4.20
3.36
4.67
5.81
7.62
C02
1006
1036
1110
1152
1416
1609
1775
1847
/V0xb
8.37
8.99
10.4
10.8
14.4
17.6
19.8
21.5
Part.
1.22
1.19
1.31
1.26
1.14
1.35
1.26
1 41
* Engine emission rates are based on a 10.3 km engine test cycle.
"NO, from bag measurement.
"Vehicle 3-23 chassis emissions were measured at 80 percent of standard horsepower.
Table 4. Comparison of Composite Fuel Specific Engine and Chassis Emissions from Vehicles 3-23 and 3-24 Measured at Several Inertia Settings
(g/kg fuel)
Vehicle
Number
3-23"
3-24
Vehicle Description
Single-axle 1981
Cummins NTC-300
Dual-axle 1980
DD8V-92TA
Engine Emissions, g/kg fuel Percent
HC CO C02 NO," Part. of GVW
7.26 14.4 3136 379 2.42 61%
70%
80%
93%
2.71 13.3 3153 37.2 2.28 55%
70%
86%
97%
Chassis Emissions,
HC
10.4
9.60
10.0
8.55
3.83
3.18
2.93
2.82
CO
11.8
11.2
11.7
11.4
7.50
9.17
10.4
13.0
C02
3128
3130
3128
3134
3156
3155
3154
3150
g/kg fuel
NO,"
26. 1
27.2
30.0
29.6
32.1
34.4
35.2
36.7
Part.
3.80
3.59
3.68
3.44
2.53
2.64
2.24
2.41
"NO, from bag measurement.
^Vehicle 3-23 chassis emissions were measured at 80 percent of standard horsepower.
-------
chassis transient cycle produced relative-
ly high CO and particulate and low HC
compared to single- and dual-axle trac-
tors. Bus CO emissions were 4 to 6 times
higher than tractor CO emissions and bus
particulate was double that of tractor
particulate emissions.
Bus emissions from the New York Bus
Cycle generally exceeded chassis trans-
ient cycle emissions with the exception of
fuel specific C02 and NO,. The greatest
difference between driving cycles was for
Table 5.
Summary of Baseline Emissions from Single-Axle Tractors, Dual-Axle Tractors, and
Buses Over the Chassis Version of the Transient Cycle and of Buses Over the New
York Bus Cycle
Emission Rate, g/km
Emission Rate, g/kg fuel
HC
CO COi
NO,
Part.
HC
. CO
CO2
NO,
Part.
Single-Axle Tractors
Average
Std. Dev.
Coef. of Var. (%)
1.94
0.86
44
3
1
.75
.26
34
1056
70
7
9.37
0.81
9
1.07
0.28
26
5.75
2.50
44
11.1
3.5
32
3144
12
<0.5
28.1
3.6
13
3.19
0.73
23
Dual-Axle Tractors
Average
Std. Dev.
Coef. of Var. (%)
Average
Std. Dev,
Coef. of Var. (%)
Average
Std. Dev.
Coef. of Var. (%)
1.74 7.19
0.48 4.58
28 64
1.71 27.4
0.10 16.6
6 61
2.23 48.0
0.32 28.6
14 60
1464
106
7
17.0
2.9
17
1.47
0.55
37
3.74
1.04
28
15.3
9.2
60
3142
16
1
35.5
5.4
15
3.15
1.10
35
Buses
1233 12.4
37 3.0
3 24
2.46 4.23 67.4 3045 30.7 6.04
1.45 030 40.7 64 7.4 3.56
59 7 60 2 24 59
Buses Over New York Bus Cycle
1488 15.2 3.89 4.51 95.9 3000 30.7 7.74
32 3.1 2.30 0.76 55.5 86 7.0 4.40
2 20 69 17 58 3 23 57
Table 6. Summary of Unregulated Emissions from Single-Axle Tractors, Dual-Axle Tractors,
and Buses Over the Chassis Transient Cycle
Emission
Total Aldehydes and
Ketones, mg/km°
Phenols, mg/km0
DOAS odor
LCA, mg/km
LCO, mg/km
Phosphorus, mg/kma
Sulfur, mg/kma
1 -nitropyrene, ug/km*
Ames bioassay, revertants/km
TA1538+S9
-S9
TA98 +S9
-S9
TA100 +S9
-S9
Single-Axle
Tractors
451
NDC
253
130
1
19
5
440
208
438
359
414
560
Dual-Axle
Tractors
238
ND
340
204
2
28
8
277
262
304
345
343
434
Buses
381
ND
895
101
3
9
ND
127
47
128
63
285
196
fAverage included only those vehicles analyzed with improvedDNPH method.
"Negligible phenol levels measured.
CND = Not Detected.
''Most common elements detected were phosphorus and sulfur.
"No dinitropyrenes detected above 1fjg/km.
CO and particulate emissions.
Unregulated emissions were measured
for 24 of the baseline test vehicles.
Aldehydes and ketones, phenols, and
odor were sampled over one cold-start
and three hot-starts. Elemental composi-
tion and soluble organic fractions (for
nitropyrene and Ames bioassay) were
determined on filters sampled during one
cold-start and filters sampled over one
hot-start. Unregulated emissions results
are summarized in Table 6. The emissions
represent composite values weighted
1 /I cold-start and 6/7 hot-start.
As a group, single-axle tractors pro-
duced higher than average total alde-
hydes and ketones and relatively high
Ames response. They also emitted lower
than average LCA odor and phosphorus
relative to all vehicle types. Dual-axle
tractors produced relatively high LCO
odor, sulfur, and 1 -nitropyrene levels and
low levels of aldehydes and ketones.
Buses tended to produce higher than
average LCA odor and phosphorus and
relatively low amounts of 1-nitropyrene
and low Ames response.
Recommendations
Results reported in this study have
provided an important step forward in
understanding the relationship between
engine and chassis testing, as well as
providing a significant data base for the
characterization of heavy-duty trucks and
buses for gaseous, particulate and un-
regulated emissions. Upon completion of
this program, it was apparent many areas
of investigation remain, before the know-
ledge of heavy-duty truck and bus emis-
sions approach that of the automobile.
Several of the areas suggested for addi-
tional research are briefly described by
various vehicle categories.
City Buses
Engine versus chassis comparisons of
a city bus showed virtually no agreement
of gaseous or particulate emissions.
Additional work is recommended to in-
clude engine versus chassis comparisons
on a different bus with the same engine
model. This study should include the
engine bus transient cycle (a cycle not
available at the time of this study) as well
as several inertia weights during chassis
testing.
Additional buses should be included
that would expand the data base to
include the DD 6V-92TA and Cummins
V-903 engines, and other engines repre-
senting significant fractions of the bus
population. These evaluations should
-------
include both chassis and engine testing
for these engines. Consideration should
be also given to developing a different bus
cycle, if it is felt that the current cycle is
not representative of real life bus opera-
tion.
Dual-Axle Diesel Truck Tractors
This program generated a substantial
amount of emissions characterization from
a variety of dual-axle tractors. These
vehicles basically represent engine pro-
duction from 1979-1981. Although most
of the major engine models were included
in this study, there will undoubtedly be
new models introduced each year. In
order to keep current on in-use emissions
characterization of heavy-duty vehicles, it
is suggested that EPA continue a limited
amount of characterization to include
new technology engines that will be built
to meet the particulate standards.
Several factors influence the gaseous
and particulate emissions from a given
engine in a dual-axle truck. The influence
of inertia weight on emissions was in-
vestigated in this study, but this was only
a first step in understanding the relation-
ship between chassis and engine emis-
sion results. For example, how much
does the transmission and gear-train
affect emissions, do the tires influence
emissions results, do assumptions in
frontal area significantly affect emissions
from dual-axle tractor. Many of the ques-
tions could be answered by obtaining two
vehicles with identical engines, but dif-
ferent drive trains, tires, etc.; testing
the vehicles over the chassis cycle; then
removing the engine and testing them
over the engine transient cycle. Upon
completion, the engines would be
switched from their original chassis and
the chassis testing repeated. This would
provide information to determine if as-
sumptions made during chassis testing
significantly affect emissions as well as
expand the data base for engine chassis
comparisons. In addition, hot-start eval-
uations would be conducted at several
horsepower settings and inertia weights
to further assess the effects of these
parameters.
Single-Axle Diesel Truck
Tractors
Results of two engine-chassis compar-
isons were obtained in this study. In one
case (IHC DT-466B), good agreement was
observed, but in the other case
{Cummins NTC-300), virtually no agree-
ment between chassis and engine emis-
sions was observed. In the case where
good agreement was observed, the engine
power to vehicle weight appeared to be
more "normally" matched for a single-
axle truck tractor. In the case of the
second engine with virtually no agree-
ment in emission results, the Cummins
NTC-300 engine had a relatively high
power to vehicle weight ratio. Several of
the single-axle tractors had engines with
relatively high power to vehicle weight
ratios. The Cummins NTC-300 engine in
a dual-axle tractor would probably provide
a better agreement of chassis and engine
emission results. If it is felt that a
significant fraction of the single-axle,
truck tractor population is in this category,
then additional work would be warranted.
This work could be similar to that des-
cribed earlier, with a given engine model
(e.g., Cummins NTC-300) being used in
both single- and dual-axle tractors for
chassis testing. This engine would also
be tested over the engine transient cycle.
The chassis tests should include various
horsepower settings to simulate different
frontal areas and different inertia weights
to simulate different loadings.
Additional emissions characterization
is also in order for single-axle tractors to
include engines that were not available
for this study and possibly include Class
VI diesel vehicles. As the technology for
developing low particulate heavy-duty
diesel engines becomes available, it is
suggested that EPA continue the char-
acterization study at a low-level of effort.
Heavy-Duty Gasoline Vehicles
In-house studies in progress at EPA in
Research Triangle Park are addressing
heavy-duty gasoline vehicles requiring
inertia up to about 19,000 Ibs. A signif-
icant portion of the heavy-duty gasoline
vehicles are above 19,000 Ibs and will not
be included in that study. Only a limited
amount of chassis testing on heavy-duty
gasoline vehicles has been conducted
using the transient cycle; and even less
data exists on engine versus chassis
comparisons. In general, heavy-duty gaso-
line chassis tests have not included
unregulated emissions characterization.
The virtual lack of emissions data in the
heavy-duty gasoline vehicle category
suggest that additional work in this area
may be justified. Some vehicle categories
that would be good candidates would
include school buses, large box vans and
soft drink and beer delivery trucks.
•&U. S. GOVERNMENT PRINTING OFFICE: 1985/559-111/10751
-------
M. A. Warner-Selph andH. E. Dietzmann are with Southwest Research Institute,
San Antonio, TX 78284.
F. M. Black is the EPA Project Officer (see below).
The complete report, entitled "Characterization of Heavy-Duty Motor Vehicle
Emissions Under Transient Driving Conditions," (Order No. PB 85-124 154;
Cost: $16.00, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, v'A 22161
Telephone: 703-487-4650
• The EPA Project Officer can be contacted at:
Atmospheric Sciences Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
BULK RATE
POSTAGE & FEES PAID
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PERMIT No G-35
Official Business
Penalty for Private Use $300
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