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

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                                                                    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.

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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
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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
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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)
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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
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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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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)


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v; n?
C
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- Engine RPM - -
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OM (mHHgram
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Sample Plot of Truck 1
•W^ : " XXf*1 1>M

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•u-uv ''' ^ •» '-' ' -u* ''' •J''1 '- '^r
	 rk 	 : 	 ¥-1— *•
ENGINE LOAD-'
dllng at 1200 RPM


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'\
i
	 1; 	
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T* 	

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	 , in-in
,f^^;i 1SOO


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	 • im a
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	 ¥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)


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_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

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  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

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 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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