RECOMMENDED HEAVY DUTY GASOLINE
INSTRUMENTATION AND TEST PROCEDURES
To the User: This recommended practice reflects
the experience of industury and government to date.
This practice is subject to change as new data
are gathered and experience is obtained.
Environmental Protection Agency
Office of Air and Waste Management
Office of Mobile Source Air Pollution.Control
Emission Control Technology Division
Standards Development and Support Branch '
July 11, 1975
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I. Test sequence and dynamometer equipment.
A. (1) The following nine-mode cycle shall be followed in dynamometer
operation tests of gasoline-fueled heavy duty engines.
Sequence
No . Mode
Observed
Torque
(% of max.
observed)
Time in
Mode-sees.
Cumulative
Time-sees.
Weighting
Factors
1
2
3
4
5
6
7
8
9
Idle
Cruise
PTA
Cruise
PTD
Cruise
FL
Cruise
CT
Idle
25
55
25
10
25
90
25
CT
60
60
60
60
60
60
60
60
60
60
120
180
240
300
360
420
480
540
0.232
.077
.147
.077
.057
.077
.113
.077
.143
(2) The engine dynamometer should be operated at a constant
speed of 2,000 r.p.m. +_ 100 r.p.m. (Speed deviations,
should not exceed 200 r.p.m. during the first four seconds
of each mode.)
(3) The idle operating mode shall be carried out at the
manufacturers recommended engine speed. Arrive at the
last idle mode by closing the throttle and unloading the
dynamometer or by actuating a clutch mechanism. The CT
operating mode should be carried out at the same engine
speed as in paragraph A. (2) of this section.
B. The following equipment should be used for dynamometer tests.
(1) An engine dynamometer capable of maintaining constant
speed +_ 100 r.p.m. from full throttle to closed throttle
motoring.
(2) A chassis-type single pipe exhaust system shall be used.
Standard or specially fabricated "Y" pipes may be used
for "V" type engines, however the probe location shall
conform to III-C-1 and this location is to be at least
three feet downstream of the "Y" intersection.
(3) A radiator typical of that used with the engine -in a
vehicle, or other means of engine cooling which will
maintain the engine operating temperatures at approxi-
mately the'same temperature as would, the radiator, shall
be used to maintain engine cooling during sustained
operation on the dynamometer. >i
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II. Dynamometer procedures.
An initial 5-minute idle, one warmup cycle, and one hot cycle
constitute a complete dynamometer run. Idle modes may be run at
the beginning and end of each test, thus eliminating the need to
change speed between cycles.
III. Instrumentation
A. Schematic Drawing.
(1) Fig. IIIA-1 is a schematic drawing of the exhaust gas
sampling and analytical system which shall be used for
testing under the regulations in the subpart. All
components or parts of components that are wetted by the
sample or corrosive calibration gases should be either
chemically clean stainless steel or teflon. Use of
hydrocarbon derivatives such as Buna-N for packings,
seals, diaphrams or any other device that may come in
contact with the sample or span gas is not recommended.
The use of "gauge savers or protectors" with nonreactive
diaphrams is permissable and recommended.
B. System Components.
The following is a list of components shown in Fig. IIIA-
1 by numeric identifier. Pressure ranges and accuracies when
given are suggested values. Any component indicated as being
heated means maintaining that component at 125°C; +10°C, -5°C
(257°F;
(1) Filters.
(a) Fl - Particulate filter.
(b) F2 - Particulate filter.
(c) F3 - Heated particulate filter.
(2) Flowmeters FL 1 and FL 2 to indicate sample flow rates
through the CO and CO- analyzers.
(3) Gauges (0-15" H_0) Gl and G2 to measure input pressure to
CO and CO analyzers and any unwanted changes in down-
stream restrictions.
(4) Pressure gauges.
(a) PI - bypass pressure (0-20 psig).
(b) P2, P3, P4, and P5 - sample 'or span pressure at
inlet to flow control values (0-10 psig).
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Vent to
Atmotphere
Legend'
Spin and Span and
Zero Gasea Zero Gait* '
Fig. Ill A-l
Heavy Duty Exhaust Gal
Sampling and Analytical Train
Paniculate niter
Flowmeterj-
Backpressure Regulator wllh
Internal Control Loop Shown
Preiaure Regulator with
Internal Control Loop Shown
Ball Valv* or Equivalent
(Oarhand Log Indlcataa Common Port)
Flow Control or Naadl* Valv*
Plug Valv* or Equivalent
(Center Port ta Common)
"*
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(5) Refrigerator or ice bath water traps (Temperature: 0-3
°C, 32-37°F) REF1 and REF2 to remove water vapor from the
sample. May include suitable method for draining trap.
(6) Regulators.
(a) Rl, R3, R4, and R6 - line pressure regulators to
control span pressure at inlet to flow control
valves (0-10 psig + 2" H90).
(b) R2 and R5 - back pressure regulators to control
sample pressure at inlet to flow control valves (0-
10 psig + 2" H20).
(7) Valves.
(a) VI, V7, V8, and VIA - selector valves to select zero
or calibration gases.
(b) V2 - Optional heated selector valve to purge sample
probe.
(c) V3 and V5 - Selector valves to select sample or span
gases.
(d) VA, V6, and V15 - flow control valves.
(e) V9 and V13 - heated selector valve to select sample
or span gases.
(f) V10 and V12 - heated flow control valves.
(g) Vll - Selector valve to select NOx or bypass mode in
the chemiluminescence analyzer.
(8) Pump - sample transfer pump to transport sample to
analyzers (1.5 CFM at free flow).
C. Component Description (exhaust gas sampling).
fi
The following components are recommended for the exhaust
gas sampling system.
(1) Sampling probe. The sample probe shall be closed end,-'
stainless steel, multi-hole probe 1/4 inch outside diameter
extending at least 80% across the exhaust pipe. There
shall be a minimum of 3 ports in probe covering approxi-
mately equal areas of the duct and oriented such that
they face into the exhaust stre'am. The orifices should
be sized such that each port has; ^approximately the same
flow. The probe shall be located approximately'\three to
nine feet downstream from the exhaust manifold outlet
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flange or turbocharger exit flange and this position must
be downstream of any exhaust emission control device(s)
(catalyst, etc.).
(2) Sample transfer. The exhaust gas sample shall be transferred
to the analytical instruments through a heated filter and
heated line by a hot pump. The heated line shall be of
stainless steel or teflon construction and have an I.D.
between .18 and .32 inches. The sample line wall temperature
must be maintained at 125° +10°C, -5°C (257°F, +18°F, -9°F)
with a maximum line length of 50 ft. The sample pump
shall be located as close as practical to the sample
probe and the wetted surfaces of the pump must be heated.
The pump must be capable of transporting the sample from
the probe to the analyzers in 5 seconds or less. The
filter must also be heated.
D. Component Description (exhaust gas analysis system).
(1) Total hydrocarbon measurement (HC). The determination of
hydrocarbon concentrations is to be ascertained by a
heated flame ionization detector (FID). See the Appendix
for general design specifications.
.(2) Oxides of Nitrogen Measurement (NOx). The concentration
of Oxides of Nitrogen (NO + NO = NOx) is to be determined
by a chemiluminescence analyzer in the (NOx) mode. This
requires the (N09) in the sample to be converted to (NO)
by the converter before analyzing the sample in the
reaction chamber. See the Appendix for general design
specifications.
(3) Carbon Monoxide Measurement (CO). The carbon monoxide
concentration is to be determined by an NDIR analyzer.
See the Appendix for general design specifications. If
the turn down ratio of the analyzer is not great enough
for the desired application, a combination of two or more
separate instruments, two or more separate cells with one
amplifier, or a multi-cell analyzer may be used. Accomplish
this by adding a selector valve between flowmeter FL2 and
gauge G2 (see Fig. IIIA-1). All cell flow paths must be
parallel and must have a gauge G2 immediately upstream of
all detector cells. Vent all detector cells to atmospheric
pressure as shown in Fig. IIIA-1. If the cells are in
series optically as in some dual cell arrangements, the
cell not in use must be. continuously purged with nitrogen
. (N9) when analyzing a' sample. Furthermore the purge
pressure at G2 should be approximately the same, as the
sample pressure at G2 although the flow rate may be
somewhat lower. v . '
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(4) Carbon Dioxide Measurement (CCO. The carbon dioxide
concentration is to be determined by an NDIR analyzer.
See the Appendix for general design specifications.
E. Venting. The method of disposing of the sample is not specified.
However, caution must be used in routing of the vent lines:
(1) Venting of the instruments, especially the NDIR analyzers,
must be such that the analyzer vent does not see a back
pressure caused by the proximity of other vents.
(2) Pressure relief vents provided by some manufacturers of
regulators and located in the bonnet of the regulator
should be vented to the atmosphere.
IV. Information.
The following information, as applicable, should be recorded
for each test.
A. Engine Description.
(1) Engine identification numbers.
(2) Date of manufacture.
(3) Number of hours of operation accumulated on engine.
(4) Engine family.
(5) Engine displacement.
(6) Curb idle r.p.m.
(7) Warm-up fast idle r.p.m.
(8) Governed speed.
(9) Maximum horsepower and torque.
(10) Maximum horsepower and torque speeds.
(11) Fuel consumption at maximum power and torque.
(12) Number of carburetors.
(13) Number of carburetor venturies.
(14) Maximum torque at 2000 r.p.m.
(15) Fuel consumption at maximum torque at 2000 r.p.m.
(16) Maximum air flow at 2000 r.p.m.
B. Test data.
(1) Test number.
(2) Instrument operator.
(3) Engine operator.
(4) Date and time of day.
(5) Fuel identification, including H/C tatio.
(6) Ambient temperature in dynamometer testing room.
' • '
•i
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(7) Engine intake air temperature and humidity for each mode.
Air temperature and humidity measurement should be made
within 18 inches of the inlet for engine intake air.
Temperature and humidity measurement devices must respond
to 90% of a step change between 30 and 120 seconds.
(8) Barometric pressure.
(9) Observed engine torque for each mode.
(10) Intake air flow for each mode.
(11) Fuel flow and temperature for each mode.
(12) Sample line temperature. Line temperature shall be taken
at a minimum of three locations, two of which should be
the sample probe outlet and instrumentation inlet.
(13) Sample line residence time (Refer to section VI).
(14) Date of most recent analytical assembly calibration.
(15) All pertinent instrument information such as tuning-gain-
serial numbers-detector number-range.
(16) Recorder chart. Identify for each test mode: zero
traces for each range used-calibration or span traces for
each range used - emission concentration traces and
associated analyzer range(s) - start and finish of each
test.
(17) Record chart speed of recorder and date of last speed
calibration. The minimum chart speed allowed is 3 inches
per minute.
(18) Record engine torque and engine r.p.m. continuously on
the same chart.
(19) All chart recorders (analyzers, torque, r.p.m., etc.)
should be provided with automatic markers which indicate
one second intervals. Preprinted chart paper (one second
intervals) may be used in lieu of the automatic markers
provided the correct chart speed is used.
V. Calibration and instrument checks.
A. Calibrate the analytical assembly including re'corder chart
speeds at least once every 30 days. Use the same flow rate
and chart speed as when analyzing samples.
(1) Perform.a pressure leak check pef section :VI.
1 \
(2) Adjust analyzers to optimize per-f-ormance. See the
Appendix. '»' • '
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(3) Zero the hydrocarbon analyzer with zero grade air and the
carbon monoxide, carbon dioxide, and oxides of nitrogen
analyzers with zero grade nitrogen. The allowable zero
gas impurity concentrations should not exceed 0.1 p.p.m.
equivalent carbon response, 1 p.p.m. carbon monoxide, 400
p.p.m. carbon dioxide, and 0.1 p.p.m. nitric oxide.
(4) Calibration gas concentrations shall be determined within
+ 1.0% of the absolute value.
(5) Set the CO and C09 analyzer gains to give the desired
range. Select desired attenuation scale of the HC
analyzer and adjust the electronic gain control to give
the desired full scale range. Select the desired scale
of the NOx analyzer and adjust the phototube high voltage
supply or amplifier gain to give the desired range.
Normally, zero and gain adjustment should be performed on
the lowest anticipated range.
(6) Calibrate the HC analyzer per the Appendix.
(7) Calibrate the CO analyzer with carbon monoxide (nitrogen
diluent) gases and the CO^ analyzer with carbon dioxide
(nitrogen diluent) gases Raving nominal concentrations of
20, 30, 40, 50, 60, 70, 80, and 90 percent of full scale
of each range used.
(8) Calibrate the NOx analyzer per the Appendix.
(9) Check NOx converter efficiency per the Appendix.
(10) Compare values obtained on all analyzers with previous
calibration curves. Any significant change reflects some
problem in the system.
B. Verification and instrument checks should be performed in
accordance with section VI on in-use systems.
C. For the purposes of this section, the term "zero grade air"
includes artificial "air" consisting of a blend of nitrogen
and oxygen with oxygen concentrations between 20.0- and 22.0-
mole percent.
D. Calibrate the dynamometer test stand and othei; instruments for
measurement of power output and the fuel flow measurement
instrumentation at least once every 180 days.
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VI. Sampling procedures.
A. HC, CO, C0? and NOx measurements. Allow a minimum of 2 hours
warmup for the CO, C02, HC, and NOx analyzers. (Power is
normally left on for the infrared, chemiluminescence, and FID
analyzers; but when not in use, the chopper motors of the
infrared analyzers are turned off and the phototube high
voltage supply of the chemiluminescence analyzer is placed in
the standby position. Also, leaving the flame and the oven
"on" in the FID leads to a more stable response.) The following
sequence of operations should be performed in conjunction with
each series of measurements:
(1) Replace or clean filters.
(2) After the filter(s) have been replaced or cleaned, check
the sampling system for any leaks that could dilute the
exhaust gas. If during the test, the filters are replaced
or cleaned, a leak check must be performed after the test
is completed. This post test leak check must be performed
after hangup checks are made. The pressure side leak
check may be borrowed from the 30 day check of the system.
Check sample system leakage in the following manner:
(a) Vacuum Side
(A) Cap the probe or sample line at the probe
fitting.
(B) Measure the flow at the discharge of the pump.
(C) If the measured flow exceeds 2.0 cc/min, effect
repairs to the system.
(b) Pressure Side
(A) Vent the inlet of the pump to the atmosphere.
(B) Cap the sample line at the point the line
connects to the analysis train.
(C) Measure the flow at the inlet to the pump.
(D) If the measured flow exceeds 10.0 cc/min,
effect repairs to the system.
(E) All other pressure fittings may be checked by
using the bubble-check method. Various com-
mercial preparations are available for this
purpose. Fitting leakage should b$ cprrected.
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(3) Introduce the zero grade gases at the same flow rates
used to analyze the test samples and zero the analyzers
on the lowest anticipated range that may be used during
the test. Record a stable zero for each anticipated
range that may be used during the test prior to the test.
Record these zero values for each analyzer.
(4) Introduce span gases to the instruments under the same
flow conditions as were used for the zero gases. Adjust
the instrument gains on the lowest range to be used to
give the desired value. Span-gases should have a con-
centration greater than 65% of full-scale for each range
used. A significant shift in gain setting indicates an
instrument or system problem. If necessary, recheck
calibration and span-gas concentration-label. Record the
response to the span-gas and the span-gas concentration
for each anticipated range that may be used during the
test prior to the test. Record these values for each
analyzer.
(5) Recheck zeros; repeat the procedure in subparagraphs (3)
and (4) of this paragraph, if required.
(6) Check sample line temperature and sample residence time.
To check sample residence time:
(a) Introduce HC span gas into sampling system at sample
inlet and simultaneously start timer.
(b) When HC instrument indication is 15 percent of full-
scale, stop timer.
(c) If elapsed time is more than 5.0 seconds, make
necessary adjustments.
(d) Repeat (a) through (c) with CO, C0_, and NOx instru-
ments and span gases.
(7) Sample residence-time may be used from previous tests if
all of the following conditions are met:
(a) The same size and type of pump is used.
(b) The sample line I.D. is the same and. the length is
equal to or shorter than the tested line.
(c) The sample line temperature is -the same (+ 5°C,
9°F).
'
(d) Pressure gauges PI, P2, P3,;,P4, and P5 read the same
pressure (+ 15% of original value). y '•«
S
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cs) Check instrument flow rates and pressures.
(9) Operate the engine in accordance with section VII.
Measure HC, CO, C0_, and NOx volume concentration in the
exhaust sample. Record data specified in section IV.
Should the emission volume concentration exceed 95% of
full-scale value for non linear instruments (100% of
full-scale value for linear instruments) or respond less
than 20% of full-scale value, (for all instruments) the
next higher or lower analyzer range should be used per
the Appendix. Note: the lower limit (20% of full-scale)
does not apply when the full-scale value is 120 ppm (or
ppm C) or less. Should the fuel flow instrument read
below 20% of full-scale value, a smaller flow measurement
unit must be used unless the option in the Appendix is
desired.
(10) Each range that may be used during a test must have the
zero and span responses recorded prior to the execution
of that test. Only the range(s) used to measure the
emissions during a test are required to have their zero
and span recorded after the completion of the test. If
the difference between the span-gas response and the
zero-gas response has changed more than +2.0 percent,
the test should be rerun after instrument maintenance.
In addition the test should be rerun if the zero response
changes more than +6.0 percent of full scale. If the
zero response has changed less than +_ 2.0 percent, the
pre-test zero response is to be used. However if the
response change is between +2.0 and +6.0 percent of
full scale, a zero response correction based on an
interpolation which is linear with time is acceptable.
B. Sample system contamination.
(1) Care shall be taken to avoid loading of the sampling
system with raw fuel discharged during engine starting.
(2) When the sample probe is in the exhaust stream and sampling
is riot in process, a back purge with air or an inert gas
may be necessary to protect the probe and sample line
from particulate buildup which could affect hydrocarbon
readings. Check sample line for contamination before and
after each test. Use the following procedure to check ' .
the sample line:
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(a) With the HC analyzer calibrated on the lowest range
to be used for the test, and the sample line at the
required temperature, check the sample-line hangup
at least 45 minutes prior to the start of the test
sequences. Introduce an HC zero-gas into the sample
probe. If the instrument reading increases from the
calibrated-zero reading by more than 5.0 percent of
full-scale, the sample-line shall be purged or
cleaned as required to bring the instrument reading
within limits.
(b) Within 10 minutes after the completion of the post-
test zero and span check of the analyzers, check the
sample-line hangup. Remove the probe from exhaust
pipe. Turn the engine off. Introduce an HC zero-
gas into the sample probe. If the instrument reading
increases from the calibrated-zero reading by more
than 5.0 percent of full scale, rerun the test.
VII. Dynamometer test run.
A. (1) Mount test engine on the engine dynamometer.
(2) Install instrumentation and sample probe as required.
B. Precondition the engine by the following steps.
(1) The engine should be turned off and allowed to stand for
a minimum of 5 hours.
NOTE: The engine is not required to be installed in a
test cell to meet this requirement. The engine may be in
transit to another laboratory.
(2) The engine should be started and operated at:
(a) Zero load at.the manufacturer's warm-up fast idle
speed for 1 minute.
(b) A torque load equivalent to 10 + 3 percent of the
most recent determination of maximum torque for 4
minutes.
(c) A torque load equivalent to 55 + 5 percent of the
most recent determination of maximum torque for 35
minutes.
(3) Check the manufacturer's specifications as required.
This check should be performed within 10 minutes.
!>•»
(4) Determine the maximum torque of the engine at t|ie speed
specified in section I.
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(a) After the engine has reached the speed specified in
section I, run the engine at wide open throttle.
Record the high and low torque reading during the
second minute of operation at wide open throttle.
Do not operate the engine at wide open throttle for
more than 3 minutes. The average of the recorded
high and low .torque readings is the maximum torque
value for the test.
(b) Calculate the torque corresponding to 10, 25, 55,
and 90 percent of the maximum torque value determined.
(5) Determine the analyzer ranges required for each mode to
meet the range specifications of section VI. The engine
must not be operated for more than 5 minutes.
(6) The engine shall be turned off and allowed to stand for
at least 1 hour, but not more than 2 hours, at an ambient
temperature of 25°C + 5°C (77°F + 9°F).
(7) Should it be determined that the test must be rerun, and
if the time requirements of section VII.B(6) have not
been exceeded, then only the preconditioning specified in
that section need be performed prior to continuing with
the test.
C. The following steps should be taken for each test:
(1) Maintain dynamometer test cell temperature ambient
temperature at 25°C + 5°C (77°F + 9°F).
(2) Observe sampling procedures in section VI. Zero and span
emission analyzers.
(3) Start cooling system.
(4) Start engine and idle at manufacturer's warm-up fast idle
specification for 5 minutes.
(5) Release 'the choke-idle-stop (if necessary) and return the
engine throttle control to the curb idle position, start
sample flow and recorders, and begin test sequence of
section I.
(6) Check analyzer and spans as required for section VI.
(7) The calculated-torque values from section VII are used as
the control parameters for the test sequence of section
I. During the test the observed\torque value for each
mode should not deviate more than +2.0 percent of maximum
torque from the calculated-torque value. ', '<
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(8) Perform test sequence of section I. Repeat this sequence
until a total of two consecutive test sequences have been
completed.
VIII. .Chart reading.
The exhaust gas analyzer recorder response always lags the
engine's operation because of a variable exhaust system delay and a
fixed sample system delay. Therefore, the analyzer responses for
each mode may not be located on the charts at a point corresponding
to the exact time of the mode. A computer or any other automatic
data processing device may be used as long as the system meets the
requirements under this subpart. For each warmup or hot cycle to
be evaluated, proceed as follows:
A. Determine whether the cycle was run in accordance with the
procedure specified in section I by observing either chart
pipe, speed trace, torque trace, or concentration traces. The
test should be invalidated if there is a deviation by more
than: (1) two seconds from the specified time for the CT
mode, or (2) 4^ 2 percent of maximum torque during each mode
excluding the first 10 seconds of each mode, or (3) 200
r.p.m. during the first 4 seconds of each mode, or 100 r.p.m.
during the remainder of each mode.
B.. Time correlate the hydrocarbon, carbon monoxide, carbon dioxide,
and nitric oxide charts. Determine the location on the chart
of analyzer response corresponding to each mode. Determine
and compensate for trace abnormalities.
C. Determine concentrations.
(1) For all modes except the CT mode, locate the last 10
seconds for each of these modes. Integrate the chart
reading to determine the percent of full-scale deflection
of the C0_, CO, HC, and NOx analyzers during this 10
seconds.
(2) For all CT modes, locate the last 50 seconds for each of
these modes. Integrate the chart reading to determine
the percent of full-scale deflection of the CO , CO, HC,
and NOx analyzers during this 50 seconds.
(3) If the excursion from a straight line (other than instrument
noise) during these specified time intervals is less than
1 percent of full scale, a simple average may be used to
determine analyzer deflection.
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(4) For each mode, determine the concentration of the CO
CO, HC, and NOx during the time interval specified from
the percent of full scale analyzer deflection, span gas
response, range correction factor, linearity curves, and
other calibration data.
IX. Calculations
The final reported test results should be derived through the
following steps.
A. Determine the exhaust species volume concentration for each
mode of each test"»sequence as described in section I as
required by specific instructions in section VIII.
B. Convert the measured hydrocarbon (HC) volume concentration to
dry basis per the following:
wet-concentrations
x dry-concentrations
where:
(;DCQ2 DCO\ 2Y /DCO2 DCO WHC \ / \
'•——. + —- 1+ —. ( — + — -t- —•— ] 1 1 + . 25 J
/ /^"^ \ f \ f
DCO
DCO
WHC
K
Y
atomic hydrogen/carbon ratio
CO volume concentration in exhaust, ppm (dry)
CO volume concentration in exhaust, % (dry)
HC volume concentration in exhaust, ppm C (wet)
Water - gas equilibrium constant =3.5
H20 volume concentration of intake air, % (See the Appendix)
fuel-air ratio (actual) /fuel-air ratio (stoichiometric)
(See the Appendix)
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C. Multiply the dry nitric oxide volume concentrations by the
following humidity correction factor:
K/M«V = 0.6272 +. 0.00629H - 0.0000176H2
(NO)
A
H = humidity of the inlet-air in grains of water per pound of dry
air (See the Appendix).
D. Compute the dry (f/a) as follows:
,,, N 4.77 \" + 4 j (f/a)stoich
(f/a) = —
DCO \ / DHC \ e* / _ DHC \ .75
dry concentration = wet concentration/K^
K = water-gas equilibrium constant = 3.5
X = DC02/102+DCO/106+DHC/10^
Compare the calculated dry (f/a) to the measured fuel and air
flow. For a valid test the emission calculated (f/a) -must agree within
10% of the measured (f/a) for each mode (idle\ and CT mode excepted).
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E. Calculate the mass emissions of each species in grams per
hour for each mode as follows:
4 f
10
1) HC.grams/hr = Wur =
DCO DHC_
1Q4 2 IO4
M W
MCO 4 Wf
2) C
2 IO4/
DKNO „
2 IO4
3) NOx grams/hr = WNQX = +Q ^-
104 2 IO4
where
o< = atomic hydrogen/carbon ratio
DCO = CO volume concentration in exhaust, ppm (dry)
DCO? = C02 volume concentration in exhaust, % (dry)
DHC = HC volume carbon concentration in exhaust, ppm C (dry)
DKNO = NO volume concentration in exhaust, in ppm (dry and humidity
corrected)
M = Molecular weight of the carbon
t>
(M + o< M ) = mean molecular weight of the fuel/carbon atom
Mpn = Molecular weight of CO
\s\)
M = Molecular weight of hydrogen
M^ = Molecular weight of nitrogen dioxide (N0«)
W = Mass rate of CO in exhaust, grams/hr,
CO
Wf = Mass flow rate of fuel used in the engine, grams/hr
= (453.59)x(Wf Ibs/hr)
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Wu/, = Mass rate of HC in exhaust, grams/hr '
HL
W = Mass rate of NO in exhaust, grams/hr
F. Weight the mass values of BHP, W , W , W , and W for
each mode by multiplying the modal mass values by the appropriate
modal weighting factor prescribed by section I.
G. Calculate the brake specific emission for each test sequence by
summing the weighted values (BHP, W, Wn, and W ) from each
i c t i rlL» \j\J rJUX
mode as follows:
weighted W
BSHC(i) =
2! weighted BHP
£ weighted W
BSCO(i) = T-ii-s-Jls.
£ weighted W
BSNOx(i) =
weighted BHP
(i) = Test sequence number (i = 1, 2)
H. Calculate the brake specific fuel consumption (BSFC) from the
non-weighted BHP and Wf values for each mode (except the idle
and CT modes) as follows:
W
•BSFC =
Corrected BHP
Wf . = Fuel flow in Ib/hr
where:
BARO = Barometric pressure (in Hg A)
T = Temperature of inlet air, °F
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I. Calculate the weighted brake specific fuel consumption (WBSFC)
for each test sequence by summing the weighted values (W,. and
corrected BHP) from each mode as follows:
I, weighted Wf
WBSFC(i) =
T weighted corrected BHP
Wf = Fuel flow in Ib/hr
(i) = Test sequence number (i = 1, 2)
J. Calculate the brake specific emissions and fuel consumption
for the complete test as follows:
BSHC(T) =0.35 BSHC(l) + 0.65 BSHC(2)
BSCO(T) =0.35 BSCO(l) + 0.65 BSCO(2)
BSNOx(T) = 0.35 BSNOx(l) + 0.65 BSNOx(2)
WBSFC(T) = 0.35 WBSFC(l) + 0.65 WBSFC(2)
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