United States Air and Radiation EPA420-R-02-025
Environmental Protection October 2002
Agency
vxEPA Study of Exhaust
Emissions from Idling
Heavy-Duty Diesel
Trucks and Commercially
Available Idle-Reducing
Devices
> Printed on Recycled Paper
-------
EPA420-R-02-025
October 2002
of
Han Lim
Certification and Compliance Division
Office of Transportation and Air Quality
U.S. Environmental Protection Agency
NOTICE
This technical report does not necessarily represent final EPA decisions or positions.
It is intended to present technical analysis of issues using data that are currently available.
The purpose in the release of such reports is to facilitate the exchange of
technical information and to inform the public of technical developments which
may form the basis for a final EPA decision, position, or regulatory action.
-------
ABSTRACT
Heavy duty diesel truck idling contributes significantly to
energy consumption in the United States. President
Bush's May 2001 National Energy Policy tasks the U.S.
Environmental Protection Agency (EPA) and the U.S.
Department of Transportation (DOT) to reduce truck
idling. Consequently, the EPA initiated a study that
would quantify long duration idling emissions and fuel
consumption rates.
The idling study was conducted over a two year period at
the U.S. Army's Aberdeen Test Center (ATC). A short
introductory study with five tests was done in June 2001
and a larger study with 37 tests in May 2002. In the
larger study, EPA worked with Oak Ridge National
Laboratory (ORNL) and Rowan University with funding
from the New Jersey Department of Transportation
(NJDOT).
In total, ATC performed 42 tests on nine class-8 trucks
(model years ranging from 1980's to 2001). Two of those
trucks were equipped with 11 hp diesel auxiliary power
units (APU's), and one was equipped with a diesel direct
fired heater (DFH). The APU powers electrical
accessories, heating, and air conditioning, whereas a
DFH heats the cab in lieu of truck idling. All tests were
run in a climate controlled chamber, where the trucks
idled at high and low RPMs in the following
environments: 90°F with air conditioning on, 0°F with the
heater on, and 65°F with no accessories on. ATC test
technicians adjusted the air conditioning or heater to
maintain a target cab temperature of 70°F. Each idling
test was run for approximately three hours.
EPA's ROVER (Realtime On-road Vehicle Emissions
Reporter) and ORNL laboratory emissions instruments
were simultaneously used for measuring fuel
consumption rates, HC (hydrocarbons), NOx (nitrogen
oxides), CO (carbon monoxide), CO2(carbon dioxide), O2
(oxygen), and PM (particulate matter) (ORNL only)
during the May 2002 test runs. Only the ROVER was
used during June 2001. The test data showed that,
based on the data obtained from this study: (a) on
average, a typical 1980s-2001 model year idling truck
emits 144 g/hr of NOx and 8224 g/hr CO2 and consumes
about 0.82 gal/hr of diesel fuel; (b) there is good test
repeatability when measuring idling emissions; and (c)
use of an APU can reduce idling fuel consumption by
50% to 80% and reduce NOx by 89% to 94% whereas
use of a DFH can reduce fuel consumption by 94% to
96% and reduce NOx by 99%.
INTRODUCTION
In May 2001, President Bush issued the National Energy
Policy directing EPA and DOT to work with the trucking
industry to establish a program to reduce emissions and
fuel consumption from long-haul trucks. Responding to
this directive, EPA initiated a comprehensive program
aimed at reducing idling. This includes organizing
workshops, issuing grants, implementing demonstration
projects, and most importantly, closely examining idling
fuel consumption and exhaust emissions.
EPA ran a two-phase test program. Phase 1 consisted
of a small sample of trucks and one APU, which was
completed in June 2001. The results of this phase
prompted EPA to develop a more comprehensive test
program (Phase 2), completed in May 2002.
Certain stakeholders reviewed and commented on the
May 2002 test protocol and actual field tests, including
the American Trucking Association (ATA), Rowan
University, and the 21st Century Truck Partnership (a
government-industry partnership). The phase 2 test
program was funded by the New Jersey Department of
Transportation (NJDOT) using the DOT Congestion
Mitigation and Air Quality (CMAQ) funds. The final test
protocol that was used for the May 2002 testing
incorporated comments from the above mentioned
organizations, as well as ATC and ORNL.
Long haul truck drivers idle their engines during their rest
periods to provide heat or air conditioning for the sleeper
compartment, keep the engine warm during cold
weather, and to maintain adequate battery voltage while
using electrical appliances such as a microwave oven or
television set. Other reasons cited by truck drivers for
idling include safety (i.e., keeping the windows closed,
thereby needing cooling or heating) and habit (i.e.,
protecting the engine by not turning it off).
The precise number of long-duration idling trucks is not
known. Estimating the potential number of idling trucks
requires examining several sources. The U.S. Census
Page 1 of 10
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Bureau, Vehicle Inventory and Use Survey (VIUS)
(1997), estimates that approximately 500,000 heavy duty
trucks (> 26,001 Ibs) travel more than 500 miles as their
average daily trip length. Driving this distance may
require an eight hour rest period, and during this rest
period truck drivers may idle their engines.
The uncertainty on idling trucks extends to the hours and
number of days over a year spent idling. Some reports
indicate 6-8 hours per day over 250-300 days per year.
Since DOT mandates a rest period of 8 hours after a
maximum of 10 hours of driving, it is possible to conclude
idling times of 1,500-2,400 hours per year.
While exact numbers, hours, and days are currently
unavailable, the objective of the test program was to
better understand the fuel consumption and exhaust
emissions associated with idling trucks under different
weather and accessory loads.
METHODOLOGY
To measure actual emissions from a truck's tailpipe, EPA
used the EPA-developed ROVER (Realtime, On-
highway Vehicle Emissions Reporter) system. ROVER
allows mass emissions data to be obtained
simultaneously with vehicle/engine parameter data from
the truck's diagnostic port along with vehicle location and
speed data using an integrated global positioning system
(GPS). Other instruments can also be used by
communicating through auxiliary analog channels or
serial ports.
Initially, ATC was directed to perform a 6 hour idling test
to determine the point when the pollutants reach steady
state conditions. Initial tests showed steady state
emissions at 3 hours. Therefore, every subsequent test
was run for 3 hours. Once the data were collected, EPA
staff analyzed the data and evaluated the baseline idling
emissions for these nine trucks, two APU's, and one
DFH.
Truck Selection
Trucks of various ages that represent highway trucks
from the 1980's to present day were obtained for testing.
ATC used class-8 trucks that were available at the
Aberdeen Test Proving Grounds and commercially
available truck rentals such as Ryder that ranged from
mid-1980's to 2001. Various model year trucks were
selected including three representing the model years
near the pivotal highway diesel engine standards change
years 1997 (5.0 g/bhp»hr NOx standard) to 1998 (4.0
g/bhp'hr NOx standard). Table 1 below shows the
descriptions of each truck. The grey blocks in Table 1
represent trucks and APU tested in June 2001, the white
blocks represent trucks, APU, and DFH tested in May
2002.
Table 1: Truck and Engine Identification
Truck and Engine
1985 Volvo White**
1990 Volvo NTC-400
1992 Ford*
1992 Caterpillar 3406B
Rated HP and
engine
displacement
Additional Truck
Information as available
400@2100rpm Engine* 11611170, date
855 CID (14.0 L) of mfr. 12/90
425 @ 2000 rpm
890 CID (14.6 L)
Engine Family
NCT0893FPB9
Serial No. 3ZJ23694
1995 International 470 @ 2100 rpm Engine Family:
(Navistar) 1995 774 CID (12.7 L) SDD12.EJDARA
Detroit Diesel S60 approx. age: 650,000miles
1997 International
(Navistar)
Caterpillar 3406
1997
1998 Freightliner
1997 Cummins
1999 Volvo
1999 Detroit Diesel S60
1999KenworthT8
1998 Caterpillar 3
2000 Volvo 2000 I
Diesel Series 60
2001 Freightliner
2000 Detroit Diesel
Series 60
410 @ 1800 rpm
890 CID (14.6 L)
370/435® 1800
rpm
470 @ 2100 rpm
774 CID (12.7 L)
Engine Family:
VCP893EZDARX
Serial No. 6TS09138
Engine Family:
VCE855FJDARA
Serial No. 11861993
Engine Family:
XDDXH12.7EGL
Serial No. 06RO-547668
1800 rpm Engine Family:
ID (14.6 L) WCPXH0893r
! 2100 rpm Engine Family
3 (12.7 L) YDDXH12.7EGL
4V4NC9RH31N'
500 @ 2100 rpm
774 CID (12.7 L)
Engine Family
YDDXH12.7EGL
Serial No. 06R0612467
Idle Reducing Devices:
1995 Pony Pack APU
Kubota Z200
2000 Pony Pack APU:
Kubota Z482
1990'sEspar Diesel
Direct Fired Heater
Model D1LC
11 @ 3600 rpm
29.23 CID
(0.482 L)
Engine Family
YKBXL.719KCB
Serial # YC4323
NOTES: Grey blocks represent June 2001; elsewhere May 2002
Only truck without a sleeper cab nor ECM data port
No ECM (engine control module diagnostic port) available
The horsepower ratings are obtained from the engine label (advertised hp)
Each truck was equipped with a sleeper cab (except as
noted in Table 1) air conditioning and heating.
Trucks were not subjected to any special maintenance
procedures (e.g., oil changes, tune-ups, etc.). All trucks
were tested as received or as rented, including the
standard diesel fuel (standard filling station fuel) that all
trucks were equipped with.
Test Conditions / Scenarios / Variables
All tests were run in a climate controlled chamber,
approximately 40 ft x 40 ft x 24 ft, where the trucks were
Page 2 of 10
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idled at high and low RPMs in the following
environments: 90°F with air conditioning operating, 0°F
with the heater operating, and 65°F with no accessories
operating. Table 2 shows all the test scenarios for phase
1 (June 2001) and phase 2 (May 2002).
Table 2: Test Matrix
JUNE 2001 TEST SCENARIOS
1985 Volvo White -1 test
1995 International - 1 test
1999Kenworth-1 test
2000 Volvo - 1 test
1995APU-1 test
A/C On
Chamber
Temp=90°F
750 RPM
600 RPM
600 RPM
1000 RPM
Heater On
Chamber
Temp=0°F
3600 RPM |
No Accessory
Chamber
Temp=65°F
MAY 2002 TEST SCENARIOS
1992 Ford -6 tests
1997 International
6 tests
1998 Freightliner - 8 tests*
1999 Volvo -6 tests plus 2
repeats**
2001 Freightliner- 6 tests
2000 APU - 2 tests
1997DFH-1 test
600 RPM
1200 RPM
700 RPM
11 00 RPM
600 RPM
800 RPM*
1000 RPM*
1200 RPM
600 RPM
1200 RPM
600 RPM
1200 RPM
3600 RPM
600 RPM
1200 RPM
700 RPM
11 00 RPM
600 RPM
1200 RPM
600 RPM
1200 RPM
600 RPM
1200 RPM
3600 RPM
High Heat
600 RPM
1200 RPM
700 RPM
11 00 RPM
600 RPM
1200 RPM
600 RPM x3**
1200 RPM
600 RPM
1200 RPM
NOTES: Total number of tests = 42
A/C = air conditioning; none = no accessories active
* Performed additional tests at the intermediate speed to examine emissions/
fuel consumption rates with varying engine RPM.
** Performed two repeat tests at 600 RPM with no accessories active to
assure good test to test repeatability
The APU tests were run with the air conditioning
operating and heater on in the 90°F and 0°F
environments, respectively. However, the DFH test was
run only in the 0°F environment. ATC test technicians
adjusted the air conditioning or heater to maintain a
target cab temperature of 70°F. EPA staff developed a
test matrix to examine the following primary test
variables: engine RPM, truck age, and accessory load.
The engine RPM was usually dialed in via electronic
onboard controls in the truck cab, except for the 1985
Volvo White truck which did not have the electronic
control feature. The 1985 Volvo truck was only tested at
one rpm. Most trucks were capable of idling from 600 to
1200 rpm. The RPM was set at one value throughout a
three hour test.
Test Equipment
ATC staff used the EPA-developed ROVER system
which is comprised of an IBM PC based data acquisition
system running EPA developed software, a Snap-On™
gas analyzer, an optional Horiba MEXA-120 zirconia
NOx sensor, and specially designed exhaust gas
flowmeter modules of various sizes.
ROVER is used to measure fuel consumption rate, HC,
CO, CO2, and NOx emissions. In the Snap-On MT3505
analyzer, non-dispersive infrared technology is used to
measure HC, CO, and CO2, whereas an electrochemical
sensor is used to measure NOx and O2. Generally, the
electrochemical and zirconia based NOx measurements
showed good comparability, however during the second
phase of this testing program, there was a zero-drift error
in the electrochemical sensor which could not be readily
rectified. Hence, only the Horiba NOx results are
presented. Furthermore, a zirconia NOx instrument
such as the Horiba MEXA-120 was appropriate for the
experiments in this study. SAE Paper 2001-01-3619
contains information that shows a zirconia NOx
instrument has a 4 to 1500 ppm linear calibration at ± 5%
measured point accuracy versus primary standards
(Schenk et al, 2001). The appropriate gas flowmeter
module was attached to the exhaust pipe of the
specimen truck.
Since the Pony Pack™ engine was equipped with a
smaller diameter exhaust pipe than the main engine, a
smaller flowmeter was used. The appropriate flowmeter
module also provided the gas sample to the gas analyzer
and temperature and pressure measurements needed
for mass determinations. Fuel consumption rate was
determined by carbon balance. Systems checks were
performed before and after a set of tests by the zero and
span gas method using calibration gases. The flowmeter
was calibrated using a laminar flow element. The
ROVER instruments were placed near the driver's seat
during idling tests (see Figure 1). The flowmeter module
mounting was different for various exhaust pipe
configurations. Figure 2 shows the typical horizontal
mounting of the flowmeter, which replaced the normal
tailpipe on a class-8 truck. ATC technicians adapted to
various configurations by making support jigs specific to
an exhaust pipe orientation or exhaust pipe size (i.e.,
smaller flowmeter for Pony Pack™ engine). Since this
idling study was a joint effort with ORNL, ORNL staff
measured the same pollutants with a separate sampling
line that was connected to their own instrumentation.
Page 3 of 10
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Figure 1: ROVER system installed on the passenger seat
ELBOW
ROVER FLOW PIPE
EXHAUST
MUf-HLER
EXHAUST
GAS PIPE
ROVER SAMPLE
LINE
Figure 2: Mounting of ROVER flow pipe / sampling lines
Note: Figure is NOT to scale.
Although PM measurements were obtained by ORNL
staff, only the ROVER test data will be presented, with
the focus on fuel consumption rates and NOx and CO2
emissions. ORNL staff will present their PM results in
their own SAE paper. ORNL PM data are not presented
in this paper.
Test Procedure
For the five tests performed during the June 2001 runs,
an initial 10 to 15 minute 'warm-up' drive was performed
before the idling test began. An ATC driver drove the
truck on the highway at about 55 miles per hour, then
parked the truck in the climate chamber with the ROVER
system fully attached. The ROVER data acquisition
program was started once the truck was in motion. The
test technician noted when the idling portion of the test
began. The chamber technician ensured that the test
chamber maintained a steady temperature of 90°F, 0°F,
or 65°F, then shut the chamber doors and began the
idling test. For safety, the ATC technicians ran flexible
exhaust hoses from the flowmeters to ports available in
the test chamber to remove unwanted exhaust gases.
The same procedure was used for the May 2002 tests,
except the warm up drive portion was not done. EPA
staff determined from the June 2001 data that the drive
portion did not appear to affect the emissions or fuel
consumption data.
During the idling tests, the ATC technicians performed
routine instrumentation checks every 30 minutes to
ensure the highest quality data even under the relatively
low exhaust flow rate under idle conditions. This was
performed by temporarily applying no-flow conditions to
the flowmeter module transducers while recording their
outputs. Each pollutant and the volume flow rate during
these half-hourly checks show up as zeros or close to
zero in the ROVER data files.
All tests for the first phase were performed over a three
day period, where two climate controlled chambers were
used to test two trucks per day. The order of the tests
was randomized to minimize bias in the data collection
(i.e., a 1990's truck was tested on the same day as a
1980's truck; two 1990's trucks were not tested the same
day). Tests for the second phase were run in a single
climate controlled chamber over a three week period.
Similar to phase 1, the order of tests was randomized to
the extent practicable.
Data Post-processing and Analysis
The ROVER portable emissions measurement system
has the capability to create a text file with columns of
data for time, HC, CO, CO2, NOx, engine speed, fuel
consumption rate, etc. The data from each test were
sampled every second (1 Hz). The ROVER data text
files were imported into Microsoft Excel™ for data
analysis.
RESULTS AND DISCUSSION
Idling emissions data were collected for nine class-8
heavy duty diesel trucks, two APU Pony Pack™ engines,
and one Espar™ DFH. The first part of this section will
discuss sample calculations that show how the
emissions and emissions reductions were obtained; the
second part will discuss the data analyses of the June
2001 testing; the third part will discuss the data analyses
of the May 2002 testing.
Sample Calculations
Determining the masses for the pollutants was important
for determining the tons of emissions. The ROVER
program was set up to determine mass emissions in real
time. The gas concentrations in parts per million (ppm)
Page 4 of 10
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or percentage (%) for the various pollutants, CO, CO2,
NOx, and HC, the measured exhaust gas flow rate, and
the gas analyzer transport and response time delays are
used. Table 3 shows the densities and other constants
used for performing various mass and fuel consumption
rate calculations in real time.
where:
B = Density of CO2 = 51.81 g/ft3
V = Volume Flow Rate = 259.813 ft3/min
C = CO2 concentration = 1.51%
F = water condensation in the sample line factor = 1.01
dt = delta time = 1 second
Table 3: Constants used in Emissions Calculations
Density
(g/ft3)
CO
32.97
CO,
51.81
HC
16.33
NOx
54.16
O,
37.18
Density of diesel fuel = 3212 g/gal;
Weight fraction of C in diesel fuel = _
= 0.869 from the relation CH, nn
12.011
[12.011 +(1.80-1.008)]
Mass of C in 1 gal. of diesel fuel = 3212 g/gal -0.869 = 2791 g
C/gal
An example record from the ROVER data file is shown in
Table 4.
Table 4: Sample excerpt from a ROVER Excel Data File
gmeLoad %
FUEL RATE G/H
ENGINE
OILTEM
Ann_dP ("I
Ann_dP ("H2O)H 3.734
Exh_Temp (F) 223.202
Amb_P(""-N i^-v^
Exh_dP ^
Chamber_T (F)
_L
AnalyCorFac 1.015
Vmix(scfm)
el(mph/s
id Grade
ib Rate(f
Altitude(l
Latitude(
' ngitude(d
Satellites
PDOP
T_Heading(d
0.332
NO
TEI
Lambda_
Lambda(
A/F
Values in the white blocks are used in the sample calculation.
For illustration purposes, sample calculations are
provided below:
Mass of C02 = [B • V • C • dt] / F
Plugging in the values shown above, yields a mass of
CO2 value equal to 3.342 g = 3342 mg, as shown in
Table 4.
Also, using the relation 0.273 grams of C in 1 gram of
CO2 yields the following:
[3.342 g C02 • (0.273 g C/1 g CO2)] / [(2791 g C/1 gal)] =
0.332 mgal = instantaneous milligallons in 1 second.
To determine the gallons per hour fuel consumption rate,
a half hour's worth of instantaneous milligallon numbers
(not shown in Table 4) are summed up and calculated to
yield 1.25 gal/hr.
Data Analyses of June 2001 Tests
As mentioned earlier, the ATC technicians performed
routine instrumentation checks every 30 minutes by
zeroing the gas analyzer, the MEXA-120, and by
checking the zero of the exhaust flowmeter module
transducers to detect any drifts in the emission
measurement system.
The HC and CO data showed low level emissions that
are typical of diesel engines. Although HC and CO data
were collected, these data were not relevant to this
study, and therefore detailed analyses of HC and CO are
not presented in this paper. NOx showed some
dynamics during the first few hours of idling, then
reached steady state. Therefore, the NOx data were
used as the criteria for determining steady state
conditions.
In the idling tests, NOx emissions typically exhibited the
behavior seen in Figure 3. After about three hours of
idling, the emissions reach a steady state condition.
When the Kenworth truck was tested the first day, ATC
staff ran the test for six hours. It appeared that a three
hour idle test would be adequate for determining the
steady state emission rates from an idling truck.
CO2 remains at a fairly constant steady state condition
throughout an idling test. However, some tests involving
no accessory loads and heater loads showed an initial
high CO2 value in the same manner as the NOx curve in
Figure 3 and then reached steady state in about 3 hours.
This phenomenon is perhaps due to a 'cold engine
Page 5 of 10
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1999 Kenworth Truck Idling Test
Engine Speed: 600 RPB] • Air Conditioning On
35 -,
30
25
Instrumentation '''zero' checfjs
1,6 2 2.5
Time (hours)
Table 5: Emission Data Summary for 2001 Test Runs
Figure 3: NOx versus time for 1999 Kenworth Truck
starting' scenario where the increased work initially
needed to pump the cold engine oil would result in a
higher initial CO2 and then a leveling off (steady state
pattern) overtime as the engine warms up.
For illustration purposes, Figure 4 shows the detailed
steady state NOx patterns for the last hour of the idle
test. The emission data (in average grams/hour) for the
1999 Kenworth Truck Idling Test
30 -; T
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! : ! ' I . :'. ', . -'"i •
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\ . Flucbjaiionfe :
4 i ; : I i
i : j i j
3 3.1 3.2 3.3 3.4 3.5 3.8 3.7 3.8 3.9 4
Time (hours)
Figure 4: Details/close-up of Figure 3
five trucks are presented in Table 5. As mentioned
before, the averaged values were calculated over a
steady state portion of the idling data file, typically the
last hour or half hour of the idling test.
In Phase 1, the idle speeds were not adjusted for any of
the tests, except for the 2000 Volvo. The 2000 Volvo
truck has a feature that will shut down the engine if the
on-board controls detect that the engine is idling at less
than 1000 rpm; therefore, the 2000 Volvo was manually
set to idle at 1000 rpm. The idle speed data were
obtained either automatically via diagnostic tool port or a
direct reading of the dashboard tachometer.
1985 Volvo
White
1999
Kenworth
1995
International
2000 Volvo
1995 Pony
Pack Engine
Idling
RPM
750
600
600
1000
3600
NOx
g/hr
19.80
81.40
84.54
112.50
10.13
CO2
g/hr
4830
4650
4256
8078
2199
NOx*
tons/yr
0.05
0.22
0.22
0.30
0.03
CO2*
tons/yr
12.78
12.30
11.26
21.37
5.82
gal/
hr
0.49
0.46
0.42
0.80
0.22
* These figures were calculated assuming a truck idles at 2400 hrs/year per
truck (using the assumptions described in the Introduction section, 8 hr/day,
300 days/yr)
The engine idle speed had a significant effect on the fuel
consumption rate, and consequently, CO2 emissions.
The 2000 Volvo truck, which was run at 1000 rpm,
produced nearly twice the CO2 and nearly double the fuel
consumption rate compared to a truck run at 600 or 750
rpm. This result is not surprising, considering that if an
engine is idling at a faster speed, fuel will be injected into
the engine many more times per second, which will lead
to a higher fuel consumption rate.
The Pony Pack™ engine is a commercially available
idling reduction technology used in thousands of heavy
duty diesel trucks in the United States. The Pony Pack™
is a 2-cylinder Kubota™ diesel engine, model Z-200 that
practically replaces the main engine's functions during
idling periods. It powers the air conditioning, heating,
and electrical accessories. The emission data in Table 5
show that there are significant reductions in fuel
consumption and emissions when compared to the 1995
International Truck with 1995 Detroit Diesel engine or the
other engines tested for this study. There is about an
88% reduction in NOx and 50% reduction in CO2. When
the Pony Pack™ engine emissions are compared to
other engines, the reductions can be higher. For
example, if a Pony Pack™ is used for idling instead of
the stock 2000 Volvo engine, EPA staff estimates a 73%
reduction in CO2 and 90% reduction in NOx could be
achieved.
Data Analyses of May 2002 Tests
The May 2002 tests were run in a similar manner to that
of the June 2001 tests, except more trucks and idle
reducing devices were tested with other variables
including heating loads, air conditioning loads, and
various RPMs. The following table shows a summary of
the test results from the May 2002 tests:
Page 6 of 10
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Table 6: Test Results from May 2002
Table 6 (continued):
1992 Ford Truck with 1992 Caterpillar Engine NCT0893FPB9:
Test*
21
22
9
10
11
12
RPM
600
1200
600
1200
600
1200
chmbr. temp (°F)
0
0
65
65
90
90
NOX (g/hr)
76.64
63.99
69.41
55.76
75.50
69.32
C02(g/hr)
5965
11404
4653
11342
6040
14711
gal/hr
0.60
1.15
0.46
1.13
0.60
1.47
1998 Freightliner Truck with 1997 Cummins Engine VCE855FJDARA:
20
13
14
15
16
17
18
1200
600
800
1000
1200
600
1200
0
65
65
65
65
90
90
328.59
154.49
164.29
163.13
199.05
174.68
251.42
12599
5348
7335
9452
12433
6813
16577
1.26
0.53
0.73
0.94
1.26
0.68
1.65
2001 Freightliner Truck with 2000 Detroit Diesel Engine YDDXH12.7EGL:
Test*
30
29
23
24
25
26
RPM
600
1200
600
1200
600
1200
chmbr. temp (°F)
0
0
65
65
90
90
NOX (g/hr)
136.23
193.57
77.69
135.31
94.36
186.95
C02(g/hr)
6848
10460
4392
9787
4787
12090
gal/hr
0.69
1.07
0.44
0.98
0.48
1.21
1997 International Truck with 1997 Caterpillar Engine VCP893EZDARX:
34
33
31
32
36
37
700
1100
700
1100
700
1100
0
0
65
65
90
90
137.02
196.76
146.01
214.62
174.17
267.27
7099
10232
5596
10043
7262
13575
0.71
1.02
0.55
0.99
0.72
1.34
1999 Volvo Truck with 1999 Detroit Diesel Engine XDDXH12.7EGL:
Test*
6
7
1
2
4
3
5
8
RPM
600
1200
600
600
600
1200
600
1200
chmbr.
temp (°F)
0
0
65
65
65
65
90
90
NOX
(g/hr)
54.83
170.28
80.98
86.64
83.24
240.98
104.58
288.42
CO2
(g/hr)
5878
10877
4102
3968
3915
9251
5042
11679
gal/hr
0.61
1.17
0.41
0.40
0.39
0.92
0.50
1.16
2000 Pony Pack APU Engine YKBXL.719KCB (for 2001 Freightliner Truck):
28
27
3600
3600
0
90
7.27
10.01
2053
2353
0.20
0.23
Espar Direct Fired Heater Model D1LC (for 1997 International Truck):
38
NOTES: "C
"RPM" = En
Tests for the
these were
Test with 1 9
problems (e
Tests 1, 2, £
test instrum
N/A
30
0.21
402
0.04
Jhmbr. temp" = Chamber Temperature
gine idling RPM set during a three hour test
: 1997 International truck were run at 700 and 1 100 RPMs since
he high and low engine speeds available.
98 Freightliner at 0 °F was omitted due to instrumentation
xcessive freezing on the sample line).
nd 4 are repeat tests intended to demonstrate repeatability of
sntation (outlined in double lines in this table).
The test numbers denote the sequence in which the tests
were run. Test instrumentation issues were worked out
early in the testing by running triplicate identical tests to
assure good test repeatability as can be seen with test
numbers 1, 2, and 4 (see double lined entries in Table 6).
For tests 1, 2, and 4, the standard deviations for NOx,
CO2, and fuel consumption were 4.85 g/hr, 96 g/hr, and
0.01 gal/hr, respectively. The coefficients of variation
(standard deviation divided by the mean) for NOx, CO2,
and fuel consumption were 0.06, 0.02, and 0.025. These
values indicate low variability and good test repeatability.
Several tests on the 1998 Freightliner truck showed a
good linear relationship between fuel consumption rate
and engine rpm. Upon analyzing the data at the various
rpm, EPA staff concluded that running tests on a high
and low rpm would be adequate to predict intermediate
fuel consumption rates at intermediate rpm's. Figure 5
shows a graphical representation of the 1998 Freightliner
truck data shown in Table 6. An R2 value of 0.99 shows
a strong linear relationship. All tests in Figure 5 were run
without any accessories active (at 65°F). Different
accessories produced different NOx emission patterns
during the idling tests. Tests with no accessories active
or heater active showed flat line responses as shown in
Figure 6.
Page 7 of 10
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1998 Freightliner Truck with Cummins Engine
Fuel Consumption veraus Engine RPM
(based on ROVER data)
JS (,-,
v; n?
C
•5 fi->^
U4
U 2
'jl^---—'
n^--"""^ ;_
i;_ i
**•**
; •--"-""
*-" . - ; -
: : ^p
.^;"i" i : i
. /- - - R2-s;o.ig6§; - i- - -
J'l. ; :' /..i
5 I rff] ~w 75;. ( «» ,' ew [« »:i \ mi ; -i^ tiK- n«r. ( ia» ,' ':?i?
- Engine RPM - -
•'.
,,
OM (mHHgram
iMjine Load f>
Sample Plot of Truck 1
•W^ : " XXf*1 1>M
••"!
•u-uv ''' ^ •» '-' ' -u* ''' •J''1 '- '^r
rk : ¥-1— *•
ENGINE LOAD-'
dllng at 1200 RPM
. RPMJ
'\
i
1;
i :
with AC
J
T*
On
, in-in
,f^^;i 1SOO
&
• im a
fl
¥t"'"<
-^ t E. ; i^ : T -v. ? ? T. ; t
Test Time (hours)
Figure 5: Linear relation between gal/hr and rpm
Figure 7: Example Plot of Air Conditioning Test
,s>S
i-S
If"
Sample Plot of Truck Idling at 825 RPM
with No Accessories Active
__.,_^___^__^£M.,,_^___;_,_4,=.™-_
; , N0)t i ! 1 :
, ENGINE LOAD i i
:sM^!yft!4MSs^^^ta^Ri!ft«^l^*siS3s&^^
Test Time (hours)
~™
_J |
; 300 it;
«„
NOx Data organized by RPM
Engine RPM
Figure 6: Example Plot with No Accessories Active
Figure 8: NOx data sorted by RPM for 2002 Tests
Air conditioning tests, however, showed cyclical patterns,
which is caused by the engine fan and the air conditioner
electromagnetic clutch engaging during the tests (see
Figure 7). Furthermore, Figure 7 shows that the engine
rpm, engine load, and NOx emissions are affected by the
air conditioner compressor load. The NOx, rpm, and
load spikes and peaks appear to occur at the same time.
These spikes and peaks produce an additive effect on
the NOx emission rates. As discussed in the June 2001
data section, higher rpm's will produce higher emissions
and fuel consumption rates as evidenced in the data
presented in Table 6.
Figure 8 shows all of the average NOx data in grams per
hour for the 2002 tests. Note that there is a general
trend where NOx increases with chamber temperature
and RPM. The data in Figure 8 are also presented in
Table 6. The occasional low NOx values are from the
1992 Ford Truck with a Caterpillar engine. This truck
appears to have the lowest NOx values and seems least
affected by engine RPM or ambient temperature or
accessories active.
Clearly, air conditioning tests will produce higher NOx
values, especially with the additive cyclical NOx emission
patterns and higher engine load from the air conditioner
compressor.
The matrix of tests run during 2002 showed a wide range
of fuel consumption and emissions results by varying
engine age, engine rpm, and ambient temperature
(accessories on or off). Table 7 summarizes the high,
low, and average values.
Page 8 of 10
-------
Table 7: High, Low, and Average Emissions and Fuel
Consumption Rates for 2002 Test Data
NOx (g/hr)
C02 (g/hr)
gal/hr
ARITHMETIC MEAN FOR ALL TESTS
High Value
LowValue
Average Value
Standard Deviation
Coefficient of Variation
Low RPM avg. (600 - 800 rpm)
High RPM avg. (1000 - 1200 rpm)
329
55
144
72
0.5
114
190
16,578
3,915
8,224
3571
0.43
5805
11815
1.65
0.39
0.82
0.40
0.43
0.58
1.18
WEIGHTED AVERAGE VALUES (60% High RPM, 40% Low RPM):
Weighted Average Value:
160
9411
0.94
WEIGHTED AVERAGE VALUES (70% High RPM, 30% Low RPM):
Weighted Average Value:
167
10012
1.00
As it turns out, the average fuel consumption rate is the
same as the highest rate obtained from the 2001 testing.
The average NOx of 144 g/hr, however is somewhat
higher than the 112 g/hr obtained from the 2001 testing,
which seems reasonable considering tests at higher
rpms such as 1200 rpm were performed. One should
keep in mind that the average values in Table 7 are
calculated with over 30 unique test scenarios that span
extreme ambient temperatures, engine rpms, and
parasitic loads (A/C and heating), which would explain
the coefficients of variation in the 0.4 to 0.5 range.
It is general practice to idle the engine at 1000 rpm or
higher when heavy accessory loads are present.
Truckers can reasonably be expected to operate their
heaters on days when the temperature drops below 50°F
and to operate their air conditioning on days when
temperatures exceed 70°F. National Oceanic and
Atmospheric Administration (NOAA) temperature data
indicate that these temperature ranges can be expected
to occur nationwide between four and nine months of the
year (NOAA, 2000). Operation of accessory loads
would occur during these months.
With that said, for illustration purposes only, weighted
average values were calculated in addition to the overall
arithmetic mean values, to reflect use of accessory
loads. Table 7 shows that with the high rpm tests
weighted at 60% and low rpm tests weighted at 40%, the
weighted average NOx value is 160 g/hr. If the high rpm
weighting factor is increased to 70% high rpm, with a
30% low rpm, the weighted NOx is 167 g/hr. These are
only example weighted averages. However, EPA staff
conservatively estimate that on average, an idling class-8
truck can emit 144 g/hr of NOx based on the data
collected in this study.
Emissions and Fuel Consumption Reductions Achievable
by Using Idle Reducing Devices
Several types of technologies exist that will effectively
reduce long-duration idling. EPA maintains a list of idle
reduction technologies that can be accessed at the
following website: http://www.epa.gov/otaq/retrofit/
idlingtech.htm. EPA makes no claims as to the
effectiveness or operation of these products, and the list
is for informational purposes only. Two idle technologies
were selected to determine the emissions associated
with these products, and their potential emission
reductions when compared to baseline idling emissions
from the test vehicles. One technology, an auxiliary
power unit by Pony Pack, Inc. has the ability to provide
heat, air conditioning, and electrical power. The other
technology is a direct fired heater by Espar, Inc., which
provides heat only. These two products were selected
for their ability to provide air conditioning and/or heat.
While other similar products exist on EPA's list of
technologies, these two were selected arbitrarily.
The following discussion compares the idle reduction
device to the truck to which that device is attached. For
the direct fired heater (DFH), NOx emission rates and
fuel consumption rates from the 1997 International Truck
with Caterpillar engine are compared to the DFH. With
the DFH producing 0.21 g/hr of NOx and the Caterpillar
engine emitting 137 to 197 g/hr (700 to 1100 rpm,
respectively at a chamber temperature of 0°F with the
main engine heater on), a 99% reduction in NOx appears
to be achievable. Similarly, Table 8 shows percent
reductions achievable from a DFH or an APU.
The data from the May 2002 testing shows results
comparable to those obtained in June 2001. The 1995
APU was capable of reducing NOx by 88% and CO2 by
50%, whereas a 2000 APU was capable of reducing NOx
by 89 to 96% and CO2 by 52 to 81 %.
Although the data obtained from June 2001 provided a
glimpse of the idling data characteristics, EPA staff
based their data analyses and emissions estimates on
the May 2002 data, which provided a more
comprehensive and consistent set of data.
Nevertheless, the data from 2001 and 2002 are
comparable.
Page 9 of 10
-------
Table 8: Percent Reductions Achievable with the Use of
an Idle Reducing Device
1997 International Truck with Caterpillar Engine with the truck
heater on
Truck @ 700 rpm
Truck @ 1 1 00 rpm
DFH
Percent Reduction
gal/hr
0.71
1.02
0.04
94-96%
NOx (g/hr)
137
197
0.21
99%
C02 (g/hr)
7100
10232
402
94-96%
2001 Freightliner Truck with Detroit Diesel Engine with the truck
heater on
Truck @ 600 rpm
Truck @ 1 200 rpm
APU w/ heater on
Percent Reduction
gal/hr
0.69
1.07
0.20
71-81%
NOx (g/hr)
136
194
7.3
94-96%
C02 (g/hr)
6848
10640
2053
71-81%
2001 Freightliner Truck with Detroit Diesel Engine with the truck air
conditioninq on
Truck @ 600 rpm
Truck @ 1 200 rpm
APU w/ AC on
Percent Reduction
gal/hr
0.48
1.21
0.23
52-80%
NOx (g/hr)
95
174
10.0
89-94%
C02 (g/hr)
4787
12090
2353
52-80%
Using the data in Tables 7 and 8 it is possible, with some
assumptions about the idling characteristics of the fleet,
to make estimates of the idling emissions of the nation's
truck fleet. As an example, if the fleet consists of
500,000 trucks and those trucks idle 8 hours per day,
300 days per year while consuming 0.8 gal of fuel per
hour then those trucks produce 10.9 million tons of CO2
per year (21.7 tons/year per truck) and 190,476 tons of
NOX per year (0.38 tons/year per truck). Under this
example, those trucks would consume 960 million
gallons of diesel fuel while idling.
CONCLUSION
The purpose of EPA's idling test program was to closely
examine long-duration idling emissions on a diverse
group of heavy duty trucks under various engine speeds,
ambient temperatures, and accessory loads. Prior to this
test program, long-duration idling tests had not been
conducted. EPA and other organizations and institutions
have examined idling for brief periods of time, but these
tests did not reflect the more realistic long-duration idling
periods.
Based on the emissions and fuel consumption data
generated from this study, the test data showed that (a)
on average, a class-8 truck could emit 144 g/hr of NOX
and 8224 g/hr of CO2, and could consume about 0.82
gal/hr of diesel fuel and (b) the use of idle reduction
technologies can reduce fuel consumption and emissions
significantly.
The idling test program supports EPA's continued
commitment in working with the trucking industry and its
stakeholders to reduce idling. To date, EPA has
organized workshops, funded demonstration projects,
and created a grant program to assist trucking
companies. Future plans include identifying idling
emissions within mobile models and inventories, and
creating incentives for states to reduce idling.
REFERENCES
Avallone, Eugene A. and Theodore Baumeister III, Marks'
Standard Handbook for Mechanical Engineers Ninth Edition,
McGraw-Hill Publishers, 1987
Brodrick, C.J. et al, Potential Benefits of Utilizing Fuel Cell
Auxiliary Power Units in Lieu of Heavy Duty Truck Engine
Idling, Institute of Transportation Studies, University of
California- Davis, 2001.
National Archives and Records Administration (NARA), Code
of Federal Regulations Title 40 Part 86: Control of Emissions
from New and In-Use Highway Vehicles and Engines, Office of
the Federal Register, July 2001.
National Energy Policy Development Group, National Energy
Policy, President of the United States of America, May 2001.
National Oceanic and Atmospheric Administration, National
Climate Data Center, U.S. Climatological Averages and
Normals, Normal Daily Maximum and Minimum Temperatures,
Degrees F (1971 - 2000); Calculated by month (January -
December) for major metropolitan areas, 2000.
Schenk, Charles R., Joseph F. McDonald, and Christopher A.
Laroo, High Efficiency NOx and PM Exhaust Emission Control
For Heavy Duty On-Highway Engines - Part Two. SAE Paper
Number: 2001-01-3619, Society of Automotive Engineers
International, 2001.
Stodolsky, Frank, Linda Gaines et al, Analysis of Technology
Options to Reduce Fuel Consumption of Idling Trucks, Center
for Transportation Research, Argonne National Laboratory,
Paper No. ANL/ESD-43, 2000.
U.S. Census Bureau, VIUS 1997, Vehicle Inventory and Use
Survey, Department of Commerce, Washington, D.C. 1997.
U.S. Environmental Protection Agency, Office of Transportation
and Air Quality Web site; URL address: www.epa.qov/otaq
Page 10 of 10
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