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

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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

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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.

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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.

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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

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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

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      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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Official Business
Penalty for Private Use $300

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