RECOMMENDED PRACTICE
for
DETERMINATION OF EVAPORATIVE EMISSIONS
from
LIGHT DUTY VEHICLES
sszz
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF AIR AND WASTE MANAGEMENT
MOBILE SOURCE AIR POLLUTION CONTROL
OCTOBER 1975
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420R75104
Recommended Practice
for Determining
Exhaust and Evaporative Emissions
from Light Duty Vehicles and Trucks
October, 1975
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Table of Contents
Section
105 Introduction; structure of subpart 1
106 Equipment required; overview 1
107 Sampling and analytical system, evaporative
emissions 2
108 Dynamometer 2
109 Exhaust Gas sampling system 2
110 Exhaust Gas analytical system 5
111 Fuel specifications 6
112 Analytical gases 8
113 EPA Urban Dynamometer Driving Schedule. . . .9
114 Calibrations, frequency and overview. . 9
115 Evaporative emission enclosure calibrations. .10
116 Dynamometer calibration 13
117 Constant volume samper calibration 14
118 Hydrocarbon analyzer calibration 21
119 Carbon monoxide analyzer calibration 22
120 Oxides of nitrogen analyzer calibration. . . .23
121 Carbon dioxide analyzer calibration 25
122 Calibration of other equipment 25
123 Test procedures, overview 25
124 Transmissions 26
125 Road load power and inertia weight
determination 27
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126 Test sequence, general requirements 29
127 Vehicle preparation 29
128 Vehicle preconditioning. . . 29
129 Diurnal breathing loss test 30
130 Running loss test 32
131 Dynamometer procedure. . . 32
132 Engine starting and restarting 3;3
133 Dynamometer test runs 35
134 Hot soak test 37
135 Exhaust sample analysis 38
136 Records required 39
137 Calculations; evaporative emissions 40
138 Calculations; exhaust emissions 41
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105 Introduction, structure of Recommended Practice
(a) This Recommended Practice describes the equipment required
and the procedures to follow in order to perform exhaust and evapora-
tive emission tests on light duty vehicles and light duty trucks.
(b) Three topics are addressed in this Recommended Practice.
Sections 106 through 113 set forth specifications and equipment re-
quirements; sections 114 through 122 discuss calibration methods and
frequency; test procedures and data requirements are listed (in
approximately chronological order) in sections 123 through 139.
(c) References to the Federal Register pertain to Part 86 Volume
40, No. 126.
106 Equipment required; overview.
(a) This section contains procedures for both exhaust and
evaporative emissions tests on gasoline or diesel fueled light duty
vehicles and light duty trucks. Certain items of equipment are not
necessary for a particular test, e.g., evaporative enclosure when
testing diesel vehicles. Equipment required and specifications are as
follows:
(1) Evaporative emission tests, gasoline fueled vehicles. The
evaporative emission test is closely related to and connected with the
exhaust emission test. All vehicles tested for evaporative emissions
must be tested for exhaust emissions. (Diesel vehicles are excluded
from the evaporative emission test.) Section 107 specifies the necessary
equipment.
(2) Exhaust emission tests. Diesel and gasoline fueled vehicles
are tested identically with the exception of hydrocarbon measurements;
diesel vehicles require a heated hydrocarbon detector, section 109.
All gasoline fueled vehicles are either tested for evaporative emis-
sions or undergo a diurnal heat build, diesel vehicles are excluded
from this requirement. Equipment necessary and specifications appear
in sections 108 through 112.
(3) Fuel, analytical gas, and driving schedule specifications.
Fuel specifications for exhaust and evaporative emission testing and
for mileage accumulation for gasoline and diesel fueled vehicles are
specified in 111. Analytical gases are specified in 112. The EPA
Urban Dynamometer Driving Schedule for use in exhaust testing is
specified in 113 and Appendix I of the Federal Register.
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107 Sampling and analytical system, evaporative
emissions.
(a) Component description (evaporative emissions sampling
system). The following components will be used in evaporative emis-
sions sampling systems for testing under this Recommended Practice.
(1) Evaporative emission measurement enclosure. The enclosure
shall be large enough to accommodate the largest vehicle to be tested,
with space for personnel access to all sides of the vehicle. The
enclosure door must allow entry of the maximum size vehicle. When
sealed, the enclosure shall be gas tight. Interior surfaces must be
impermeable to hydrocarbons. One surface should be of flexible, impermeable
material to allow for minor volume changes, resulting from temperature
changes. To maximize dissipation of heat, wall materials should be of
minimum thermal resistance.
(2) Evaporative emission hydrocarbon analyzers. A hydrocarbon
analyzer utilizing the hydrogen flame ionization principle (FID) shall
be used to monitor the atmosphere within the enclosure. The FID
shall have a minimum full scale measuring sensitivity of 5 ppm propane
with a stability of + 1% of range, a reproducibility of + 1% of range
and a response to 90% of final reading within 1.5 s. Sufficient
ranges will be available, such that any reading will fall within the
upper 80% of the range in use.
(3) Evaporative emission hydrocarbon data recording system.
The electrical output of the FID shall be recorded at the initiation
and termination of each diurnal or hot soak. The recording may be by
means of a strip chart potentiometric recorder, by use of an on-line
computer system or other suitable means. In any case, the recording
system must have operational characteristics (signal to noise ratio,
speed of response, etc.) equivalent to or better than those of the
signal source being recorded, and must provide a permanent record of
results. The recording system must provide a positive indication of
the initiation and completion of each diurnal or hot soak along with
the time elapsed between initiation and completion of each soak.
(4) Tank fuel heating system. The tank fuel heating system
shall consist of a heat source and a temperature controller. A
typical heat source is a 2000 w heating pad. Other sources may be
used as required by circumstances. The temperature controller may be
manual, such as a variable voltage transformer, or may be automated.
The heating system must not cause hot spots on the tank wetted surface
which could cause local overheating of the fuel. Heat must not be
applied to the vapor in the tank above the liquid fuel. The tempera-
ture controller must be capable of controlling the fuel tank temperature
during the diurnal soak to within + 2°F (1.1°C) of the following
equation:
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F = 60 + 0.4 t
or for SI units:
C = 15.556 + 2/9 t
Where:
F = Temperature in °F
C = Temperature in °C
t = Time since start of test in minutes
(5) Temperature recording system. Strip chart recorder(s)
or automatic data processor shall be used to record enclosure ambient
and vehicle fuel tank temperature during the evaporative emissions
test. The temperature recorder or data processor shall record each
temperature at least once every minute. The recording system shall be
capable of resolving time to + 15s and capable of resolving temperature
to + 0.75°F (0.42°C). The temperature recording system (recorder and
sensor) shall have an accuracy of + 2°F (1.1°C). The recorder (data
processor) shall have a time accuracy of + 15s and a precision of +
15s. The ambient temperature sensor shall be located in the enclosure,
within 6 inches (15 cm) of the geometric center of the ceiling and
between 6 and 12 in. (15 and 30 cm) below the ceiling surface. The
vehicle fuel tank temperature sensor shall be located in the fuel tank
so as to measure the temperature of the prescribed test fuel at its
approximate mid-volume of the fuel. Vehicles furnished for testing
shall be equipped with copper-constantan Type T thermocouples for
measurement of fuel tank temperature.
(6) Purge blower. One or more portable or fixed blowers
shall be used to purge the enclosure. The blowers shall have sufficient
flow capacity to reduce the enclosure hydrocarbon concentration from
the test level to the ambient level between tests. Actual flow capacity
will depend upon the time available between tests.
(7) Mixing blower. One or more small blowers or fans shall be
used to mix the contents of the enclosure during evaporative emission
testing. Maintenance of uniform concentrations throughout the enclosure
is important to the accuracy of the test.
108 Dynamometer.
The dynamometer shall have a power absorbtion unit for simulation
of road load power and flywheels or other means of simulating the
inertia weight as specified in section 125.
109 Exhaust gas sampling system.
(a) (1) Schematic drawings. Figure 1 is a schematic drawing of
the Positive Displacement Pump - Constant Volume Sampler (PDP-CVS) and
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Figure 2 is a schematic drawing of the Critical Flow Venturi - Constant
Volume Sampler (CFV-CVS). These are two suggested exhaust gas sampling
systems.
(2) Since various configurations can produce equivalent results,
exact conformance with either drawing is not required. Additional
components such as instruments, valves, solenoids, pumps, and switches
may be used to provide additional information and coordinate the
functions of the component systems.
(3) Other Systems. Other sampling systems may be used if
shown to yield equivalent results.
(b) Component description, PDP-CVS. The PDP-CVS, Figure 1,
consists of a dilution air filter and mixing assembly, heat exchanger,
positive displacement pump, sampling system, and associated valves,
pressure and temperature sensors.
The PDP-CVS shall conform to the following requirements:
(1) Static pressure variations at the tailpipe(s) of the vehicle
shall remain within + 5 inches of water (1.2 kPa) of the static pressure
variations measured during a dynamometer driving cycle with no connection
to the tailpipe(s).
(2) The gas mixture temperature, measured at a point immediately
ahead of the positive displacement pump, shall be within + 10°F (5.6°C)
of the designed operating temperature at the start of the test. The
gas mixture temperature variation from its value at the start of the
test shall be limited to + 10°F (5.6°C) during the entire test. The
temperature measuring system shall have an accuracy and precision of +
2°F (1.1°C).
(3) The pressure gauges shall have an accuracy and precision of
+ 3 mm Hg (0.4 kPa).
(4) The flow capacity of the CVS shall be large enough to eliminate
water condensation in the system (300 to 350 cfm, 0.142 to 0.165 m /s,
is sufficient for most vehicles).
(5) Sample collection bags for dilution air and exhaust samples
shall be of sufficient size so as not to impede sample flow.
(c) Component description, CFV-CVS. The CFV-CVS, Figure 2
consists of a dilution air filter and mixing assembly, cyclone particulate
separator, sampling venturi, critical flow venturi, sampling system,
and assorted valves, pressure and temperature sensors.
The CFV-CVS shall conform to the following requirements:
(1) Static pressure variations at the tailpipe(s) of the vehicle
shall remain within + 5 inches of water (1.2 kPa) of the static pressure
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AMBIENT AIR
INLET
TO
DILUTION AIR
SAMPLE BAG
TO
EXHAUST
SAMPLE BAG
POSITIVE DISPLACEMENT
PUMP
VEHICLE
[ EXHAUST
INLET
FOR DIESEL HC ANALYSIS ONLY
MANOMETER
REVOLUTION
COUNTER
PICKUP
DISCHARGE
(SEE FIG. B78-3 FOR SYMBOL LEGEND)
Figure 1 —EXHAUST GAS SAMPLING SYSTEM (PDP-CVS)
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VEHICLE
EXHAUST
INLET
+
SAMPLING VENTURI
CYCLONIC
SEPARATOR
PRECISION SENSOR
TO
DILUTION AIR
SAMPLE BAG
TO
EXHAUST
SAMPLE BAG
SNUBBER
ABSOLUTE PRESSURE TRANSDUCER
CRITICAL
FLOW
VENTURI
CVS COMPRESSOR UNIT
CVS SAMPLER UNIT
(SEE FIG. 3 FOR SYMBOL LEGEND)
Figure 2 —EXHAUST GAS SAMPLING SYSTEM (CFV-CVS)
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variations measured during a dynamometer driving cycle with no connection
to the tailpipe(s).
(2) The temperature measuring system shall have an accuracy and
precision of + 2°F (1.1°C) and a response time of 0.100 s to 62.5% of
a temperature change.
(3) The pressure measuring system shall have an accuracy and
precision of + 3 mm Hg (0.4 kPa).
(4) The flow capacity of the CVS shall be large enough to
eliminate water condensation in the system (300 to 350 cfm, 0.142 to
0.165 m /s, is sufficient for most vehicles). .'
(5) Sample collection bags for dilution air and exhaust samples
shall be of sufficient size so as not to impede sample flow.
110 Exhaust gas analytical system.
(a) Schematic drawings. Figure 3 is a schematic drawing of the
exhaust gas analytical system. The schematic of the hydrocarbon
analysis train for diesel fueled vehicles is shown as part of Figure
1. Since various configurations can produce accurate results, exact
conformance with either drawing is not required. Additional components
such as instruments, valves, solenoids, pumps and switches may be used
to provide additional information and coordinate the functions of the
component systems.
(b) Major component description. The analytical system, Figure
3, consists of a flame ionization detector (FID) for the determination
of hydrocarbons, nondispersive infrared analyzers (NDIR) for the
determination of carbon monoxide and carbon dioxide and a chemiluminescence
analyzer (CL) for the determination of oxides of nitrogen. A heated
flame ionization detector (HFID) is used for the continous determination
of hydrocarbons from diesel fueled vehicles, Figure 1.
The exhaust gas analytical system shall conform to the following
requirements:
(1) The chemiluminescence analyzer requires that the nitrogen
dioxide present in the sample be converted to nitric oxide before
analysis. Other types of analyzers may be used if shown to yield
equivalent results.
(2) The carbon monoxide (NDIR) analyzer may require a sample
conditioning column containing CaSO,, or indicating silica gel to
remove water vapor and containing ascarite to remove carbon dioxide
from the CO analysis stream.
(i) If CO instruments which are essentially free of C0« and
water vapor interference are used, the use of the conditioning column
may be deleted, see sections 119-and 138.
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TO
SAMPLE
BAG
FOR DIESEL HC ANALYSIS
SEE FIG. B78-1
OPEN TO ATMOSPHERE
T V7 co
-[NM fciM 0 SPAN
1^VI ^ GASES
I O
GAS
T CO2
-IX] O SPAN
GASES
*
©
PR]
§
FLOW CONTROL VALVE
SELECTOR VALVE
PARTICULATE FILTER
PUMP
FLOWMETER
PRESSURE GAUGE
RECORDER
TEMPERATURE SENSOR
LOW CO
CO2
NOx
TO OUTSIDE VENT
FIGURE 3 EXHAUST GAS ANALYTICAL SYSTEM
AIR
-O OR
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(ii) A CO instrument will be considered to be essentially free
of CO. and water vapor interference if its response to a mixture of 3
percent CO,, in N_ which has been bubbled through water at room tempera-
ture produces an equivalent CO response, as measured on the most
sensitive CO range, which is less than 1 percent of full scale CO
concentration on ranges above 300 ppm full scale or less than 3 ppm on
ranges below 300 ppm full scale, see section 119.
(3) For diesel fueled vehicles a continuous sample shall be
measured using a heated analyzer train as shown in Figure 1. The
train shall include a heated continuous sampling line, a heated
particulate filter and a heated hydrocarbon instrument (HFID) complete
with heated pump, filter and flow control system.
(i) The response time of this instrument shall be less than 1.5
seconds for 90 percent of full-scale response.
(ii) Sample transport time from sampling point to inlet of
instrument shall be less than 4 seconds.
(iii) The sample line and filter shall be heated to a set point
+ 10°F (+ 5.6°C) between 300 and 390°F (149 and 199°C).
(c) Other analyzers and equipment. Other types of analyzers and
equipment may be used if shown to yield equivalent results.
Ill Fuel Specifications.
(a) Gasoline.
Gasoline having the following specifications or substantially
equivalent specifications shall be used in exhaust and evaporative
testing.
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Item ASTM Leaded Unleaded
Designation
Octane, research, minimum D2699 1'OOr 96
Pb. (organic), grams/U.S. gallon 1.4 0.00-0.5
Distillation range:
IBP , °F D86 75-95 75-95
10 percent point, °F D86 120-135 120-135
50 percent point, °F D86 200-230 200-230
90 percent point, °F D86 300-325 300-325
EP, °F (maximum) D86 415 415
Sulphur, weight percent,
maximum—' D1266 0.10 .10
Phosphorus, grams/U.S. gallon, maximum .01 .005
RVP ' , pounds D323 8.7-9.2 8.7-9.2
Hydrocarbon composition
Olefins, percent, maximum D1319 -10 10
Aeromatics, percent,
maximum D1319 35 35
Saturates D1319 Remainder Remainder
Minimum.
2
For testing at altitudes above 1,219 meters (4,000 feet) the
specified range is 75-105.
3
For testing which is unrelated to evaporative emission
control, the specified range is 8.0-9.2.
4
For testing at altitudes above 1,219 meters (4,000 feet)
the specified range is 7.9-9.2.
(3) The specification range of the gasoline to be used under
paragraph (a)(2) of this section shall be reported.
(b) Diesel fuel.
(1) The diesel fuels employed for testing shall be clean and
bright, with pour and cloud points adequate for operability. The
diesel fuel may contain nonmetallic additives as follows: Centane
improver, metal deactivator, antioxidant, dehazer, antirust, pour
depresent, dye, and dispersant.
(2) Diesel fuel meeting the following specifications, or substantially
equivalent specifications shall be used in exhaust emissions testing.
The grade of diesel fuel recommended by the engine manufacturer commercially
designated as "Type 1-D" or "Type 2-D", shall be used.
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Item ASTM test Method No. Type 1-D Type 2-D
Cetane D613 48-54 42-50
Distillation range D86
IBP, °F 330-390 340-400
10 percent point, °F 370-430 400-460
50 percent point, °F 410-480 470-540
90 percent point, °F 460-520 550-610
EP, °F 500-560 580-660
Gravity, °API D287 40-44 33-37
Total Sulfur, percent D129 or D2622 0.05-0.20 0.2-0.5
Hydrocarbon composition D1319
Aromatics, percent 8-15 27(min.)
Paraffins, Naphthenes, Olefins Remainder Remainder
Flashpoint °F (minimum) D93 120 130
Viscosity, Centistokes D445 1.6-2.0 2.0-3.2
(3) Other petroleum distillation fuel specifications:
(i) Other petroleum distillate fuels may be used for testing provided
they are commercially available, and
(ii) Information is provided to show that only the designated
fuel would be used in customer service, and
(iii) Use of a fuel listed under paragraphs (b)(2) and (b)(3) of
this section would have a detrimental effect on emissions or durability.
(4) The specification range of the fuels to be used under
paragraphs (b) (2) and (b) (3) of this section shall be reported.
112 Analytical gases.
(a) Analyzer gases.
(1) Gases for the CO and C02 analyzers shall be single blends of
CO and CO,, respectively using nitrogen as the diluent.
(2) Gases for the hydrocarbon analyzer shall be single blends of
propane using air as the diluent.
(3) Gases for NOx analyzer shall be single blends of NO named as
rith a maximum NO,, concent]
using nitrogen as the diluent.
NOx with a maximum NO,, concentration of 5 percent of the nominal value
(4) Fuel for the evaporative emission enclosure FID shall be a
blend of 60 percent helium and 40 percent hydrogen containing less
than 1 ppm equivalent carbon response.
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(5) The allowable zero gas (air or nitrogen) impurity concentrations
shall not exceed 1 ppm equivalent carbon response, 1 ppm carbon monoxide,
0.04 percent (400 ppm) carbon dioxide and 0.1 ppm nitric oxide.
(6) "Zero grade air" includes artificial "air" consisting of a
blend of nitrogen and oxygen with oxygen concentrations between 18 and
21 mole percent.
(b) Calibration gases shall be traceable to within 1 percent of
NBS gas standards, or EPA gas standards or other approved gas standards.
(c) Span gases shall be accurate to within 2 percent of true
concentration, where true concentration refers to NBS gas standards,
EPA gas standards or other approved gas standards.
113 EPA Urban Dynamometer Driving Schedule.
(a) The dynamometer driving schedule is listed in Appendix I of
the Federal Register. The driving schedule is defined by a smooth
trace drawn through the specified speed vs. time relationships. It
consists of a non-repetitive series of idle, acceleration, cruise, and
deceleration modes of various time sequences and rates.
(b) The speed tolerance at any given time on the dynamometer
driving schedule prescribed in Appendix I or as printed on a driver's
aid chart, when conducted to meet the requirements of section 133 is
defined by upper and lower limits. The upper limit is 2 mph (3.2 kph)
higher than the highest point on the trace within 1 second of the
given time. The lower limit is 2 mph (3.2 kph) lower than the lowest
point on the trace within 1 second of the given time. Speed variations
greater than the tolerances (such as may occur during gear changes)
are acceptable provided they occur for less than 2 seconds on any
occasion. Speeds lower than those prescribed are acceptable provided
the vehicle is operated at maximum available power during such occur-
rences. When conducted to meet the requirements of section 128 the
speed tolerance shall be as specified above, except that the upper and
lower limits shall be 4 mph (6.4 kph).
(c) Figure 4 shows the range of acceptable speed tolerances for
typical points. Figures 4(a) is typical of portions of the speed
curve which are increasing or decreasing throughout the two second
time interval. Figure 4(b) is typical of portions of the speed curve
which include a maximum or minimum value.
114 Calibrations, frequency and overview.
(a) Calibrations shall be performed as specified in section 115
through 122.
(b) At least yearly or after any maintenance, enclosure background
emission measurements shall be performed.
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_c
a
CN
a-
E
^
Is -"-
Is -*•
ALLOWABLE
RANGE
t
TIME
FIGURE 4a -DRIVERS TRACE, ALLOWABLE RANGE
ALLOWABLE
RANGE
TIME
FIGURE 4b —DRIVERS TRACE, ALLOWABLE RANGE
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(c) At least monthly or after any maintenance which could alter
calibration, the following calibrations and checks shall be performed:
(1) Calibrate the hydrocarbon analyzers (both evaporative and
exhaust instruments), carbon dioxide analyzer, carbon monoxide analyzer,
oxides of nitrogen analyzer.
(2) Calibrate the dynamometer. If the dynamometer receives a
weekly performance check (and remains within calibration) the monthly
calibration need not be performed.
(3) Perform a hydrocarbon retention check and calibration on
the evaporative emission enclosure.
(d) At least weekly or after any maintenance which could alter
calibration, the following calibrations and checks shall be performed:
(1) Check the oxides of nitrogen converter efficiency, and
(2) Perform a CVS system verification, and
(3) Run a performance check on the dynamometer. This check may
be omitted if the dynamometer has been calibrated within the preceding
month.
(e) The CVS positive displacement pump or Critical Flow Venturi
shall be calibrated following initial installation, major maintenance
or as necessary when indicated by the CVS system verification (described
in section 117).
(f) Sample conditioning columns, if used in the CO analyzer
train, should be checked at a frequency consistent with observed
column life or when the indicator of the column packing begins to show
deterioration.
115 Evaporative emission enclosure calibrations.
The calibration of the evaporative emission enclosure consists of
three parts: Initial and periodic determination of enclosure background
emissions; initial determination of enclosure internal volume; and
periodic hydrocarbon retention check and calibration.
(a) Initial and periodic determination of enclosure background
emissions. Prior to its introduction into service, annually thereafter,
and after repair, the enclosure shall be checked to determine that it
does not contain materials which will themselves emit hydrocarbons.
Proceed as follows:
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(1) Zero and span (calibrate if required) the hydrocarbon analyzer.
(2) Purge the enclosure until a stable background hydrocarbon
reading is obtained.
(3) Turn on the mixing blower (if not already on).
(4) Seal enclosure and measure background hydrocarbon concentration,
temperature and barometric pressure. These are the initial readings
C..n., T. and PD. for the enclosure background determination.
riCi i Hi
(5) Allow the enclosure to stand undisturbed without sampling
for four hours.
(6) Measure the hydrocarbon concentration on the same FID. This
is the final concentration, C „,-. Also measure final temperature and
, . HL.I
barometric pressure.
(7) Calculate the mass change of hydrocarbons in the enclosure
according to the equations in paragraph (d). The enclosure background
emissions shall not be greater than 0.4g for the 4 hours.
(b) Initial determination of enclosure internal volume. Prior
to its introduction into service the enclosure internal volume shall
be determined by the following procedure.
(1) Carefully measure the internal length, width and height of
the enclosure, accounting for irregularities (such as braces) and
calculate the internal volume.
(2) Perform an enclosure calibration check according to paragraph
(c) steps (1) through (7).
(3) If the calculated mass does not agree within 2% of the
injected propane mass, then corrective action is required.
(c) Hydrocarbon retention check and calibration. The hydrocarbon
retention check provides a check upon the calculated volume and also
measures the leak rate. Prior to its introduction into service and at
least monthly thereafter the enclosure leak rate shall be determined
as follows:
(1) Zero and span (calibrate if required) the hydrocarbon
analyzer.
(2) Purge the enclosure until a stable background hydrocarbon
reading is obtained.
(3) Turn on the mixing blower (if not already on).
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(4) Seal enclosure and measure background hydrocarbon concentra-
tion, temperature and barometric pressure. These are the initial
readings Cu_., T. and P . for the enclosure calibration.
HCi x Bi
(5) Inject into the enclosure a measured quantity, (at least
15g) of pure propane. The propane may be measured by volume flow or
by mass measurement. The method used to measure the propane shall
have an accuracy and precision of + 0.5% of the measured value.
(6) After a minimum of five minutes of mixing, analyze the
enclosure atmosphere for hydrocarbon content, also record temperature
and pressure. These measurements are the final readings for the
enclosure calibration as well as the initial readings for the retention
check.
(7) To verify the enclosure calibration calculate the mass of
propane using the measurements taken in steps (4) and (6). See para-
graph (d). This quantity must be within + 2% of that measured in step
5 above.
(8) Allow the enclosure to remain sealed for a minimum of four
hours without sampling and with the mixing blower operating. After
four hours analyze the enclosure atmosphere for hydrocarbon content;
record temperature and barometric pressure. These are the final
readings for the hydrocarbon retention check.
(9) Calculate, using the equations in paragraph (d) and the
readings taken in (6) and (8), the hydrocarbon mass change. It must
be less than +0.4 g or the enclosure cannot be used.
(d) Calculations. The calculation of net hydrocarbon mass
change is used to determine enclosure background and leak rate. It is
also used to check the enclosure volume measurements. The mass change
is calculated from the initial and final readings of hydrocarbon
concentration, temperature and pressure according to the following
equation:
= k V x 10
n
-4
•• p p p
'HCf Bf - UHCi Bi
Tf T.
Where:
VL,C = hydrocarbon mass change, g
C = hydrocarbon concentration as ppm carbon
3 3
V = net enclosure volume, ft (m ), as measured in
n (b)(l) above
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P - barometric pressure, in. Hg(kPa)
B
T = enclosure ambient temperature, R(K)
k = 3.05
for SI units, k = 17.60
i = indicates initial reading
f = indicates final reading
NOTE: Hydrocarbon concentration is stated in ppm carbon, that
is, ppm propane x3. Expressions in parenthesis are for SI units.
116 Dynamometer calibration.
(a) The dynamometer shall be calibrated at least once each month
or performance verified at least once each x^eek and then calibrated as
required. The calibration shall consist of the manufacturer's recom-
mended calibration procedure plus a determination of the dynamometer
frictional power absorption at 50.0 mph (80.5 kph). One method for
determining dynamometer frictional power absorption at 50.0 mph (80.5
kph) is described below, other methods may be used if shown to yield
equivalent results. The measured absorbed road power includes the
dynamometer friction as well as the power absorbed by the power absorption
unit. The dynamometer is driven above the test speed range. The
device used to drive the dynamometer is then disengaged from the
dynamometer and the roll(s) is (are) allowed to coast down. The
kinetic energy of the system is dissipated by the dynamometer. This
method neglects the variations in roll bearing friction due to the
drive axle weight of the vehicle. The difference in coastdown time of
the free (rear) roll relative to the drive (front) roll may be neglected
in the case of dynamometers with paired rolls.
These procedures shall be followed:
(1) Devise a method to determine the speed of the drive roll if
it is not already measured. A fifth wheel, revolution pickup, or
other suitable means may be used.
(2) Place a vehicle on the dynamometer or devise another method
of driving the dynamometer.
(3) Engage the inertial flywheel or other inertial simulation
system for the most common vehicle mass category for which the dynamo-
meter is used.
(4) Drive the dynamometer up to 50.0 mph (80.5 kph).
(5) Record indicated road power.
(6) Drive the dynamometer up to 60.0 mph (96.9 kph).
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(7) Disengage the device used to drive the dynamometer.
(8) Record the time for the dynamometer drive roll to coastdown
from 55.0 mph (88.5 kph) to 45 mph (72.4 kph). '
(9) Adjust the power absorption unit to a different level.
(10) Repeat steps 4 to 9 above sufficient times to cover the
range of road power used.
(11) Calculate absorbed road power (HP,). See paragraph (c).
(12) Plot indicated road load power at 50 mph (80.5 kph) versus
road load power at 50 mph (80.5 kph) as shown in Figure 5.
(b) The performance check consists of conducting a dynamometer
coast-down at one inertia-horsepower setting and comparing the coast-
down time to that recorded during the last calibration. If the coast-
down times differ by more than 1 s, a new calibration is required.
(c) Calculations. The road load power actually absorbed by the
dynamometer is calculated from the following equation:
HPd = (1/2) (W/32.2) (Vx2 - V22)/550t
Where:
HP = Power, horsepower, (kilowatts)
W = Equivalent inertia, Ib (Kg)
V = Initial Velocity, ft/s (m/s)
(55 mph = 88.5 kph = 80.67 ft/s = 24.58 m/s)
V = Final Velocity, ft/s (m/s)
(45 mph = 72.4 kph = 66 ft/s = 20.11 m/s)
t = elapsed time for rolls to coast from 55 mph
to 45 mph (88.5 kph to 72.4 kph)
(Expressions in parenthesis are for SI units.). When the coast down
is from 55 to 45 mph (88.5 to 72.4 kph) the above equation reduces to:
HP = 0.06073 (W/t)
for SI units, HP, = 0.09984 (W/t)
d
117 CVS calibration.
The CVS (Constant Volume Sampler) is calibrated using an accurate
flowmeter and restrictor valve. Measurements of various parameters
-14-
-------
UJ
5 £
z o
— i
30.0
20.0
10.0
10.0
20.0
30.0
40.0
ROAD LOAD HORSEPOWER AT 50 mph.
FIGURE 5 —ROAD LOAD HORSEPOWER, ACTUAL VS. INDICATED
-------
are made and related to flow through the unit. Procedures used by EPA
for both PDF (Positive Displacement Pump) and CFV (Critical Flow
Venturi) are outlined below. Other procedures yielding equivalent
results may be used.
After the calibration curve has been obtained, verification of
the entire system can be performed by injecting a known mass of gas
into the system and comparing the mass indicated by the system to the
true mass injected. An indicated error does not necessarily mean that
the calibration is wrong, since other factors can influence the accuracy
of the system, e.g. analyzer calibration. A verification procedure is
found in paragraph (c).
(a) PDF calibration.
(1) The following calibration procedure outlines the equipment,
the test configuration, and the various parameters which must be
measured to establish the flow rate of the constant volume sampler
pump. All the parameters related to the pump are simultaneously
measured with the parameters related to a flowmeter which is connected
in series with the pump. The calculated flow rate ft /min. (at pump
inlet absolute pressure and temperature) can then be plotted versus a
correlation function which is the value of a specific combination of
pump parameters. The linear equation which relates the pump flow and
the correlation function is then determined. In the event that a CVS
has a multiple speed drive, a calibration for each range used must be
performed.
(2) This calibration procedure is based on the measurement of
the absolute values of the pump and flowmeter parameters that relate
the flow rate at each point. Three conditions must be maintained to
assure the accuracy and integrity of the calibration curve. First,
the pump pressures should be measured at taps on the pump rather than
at the external piping on the pump inlet and outlet. Pressure taps
that are mounted at the top center and bottom center of the pump drive
headplate are exposed to the actual pump cavity pressures, and there-
fore reflect the absolute pressure differentials. Secondly, tempera-
ture stability must be maintained during the calibration. The laminar
flowmeter is sensitive to inlet temperature oscillations which cause
the data points to be scattered. Gradual changes (+ 2°F (1.1°C)) in
temperature are acceptable as long as they occur over a period of
several minutes. Finally, all connections between the flowmeter and
the CVS pump must be absolutely void of any leakage.
(3) During an exhaust emission test the measurement of these
same pump parameters enables the user to calculate the flow rate from
the calibration equation.
(4) Connect a system as shown in Figure 6. Although particular
types of equipment are shown, other configurations that yield equivalent
results may be used.
-15-
-------
CALIBRATION DATA MEASUREMENTS
PARAMETER
SYM
UNITS
TOLERANCES
oBarometric pressure
(corrected)
oAmbient temperature
?!
°Air temperature into LFE ETI
"Pressure depression
upstream of LFE EPI
°Pressure drop across the
LFE matrix EDP
°Air temperature at CVS
pump inlet PTI
°Pressure depression at
CVS pump inlet PPI
°Specific gravity of manometer
fluid (1.75 oil) Sp. Gr.
^Pressure head at CVS
pump outlet PPO
°Air temperature at CVS
pump outlet (optional) PTO
°Pump revolutions during
test period N
°Elapsed time for test
period t
in. Hg (kPa)
°F (°C)
°F (°C)
in. H20 (kPa)
in. H20 (kPa)
°F (°C)
in. Fluid (kPa)
in. Fluid (kPa)
°F (°C)
Revs
+.01 in. Hg (+.034 kPa)
+.5°F (+.28°C)
+.1°F (+.056°C)
+.05 in. H_0 (+.012 kPa)
~" Z
+.005 in. H20 (+.001 kPa)
+.5°F (+.28°C)
+.05 in. Fluid (+0.22 kPa)
+.05 in. Fluid (+.022 kPa)
+.5°F (+.28°C)
+ .05 s
(5) After the system has been connected as shown in Figure 6, set
the variable restrictor in the wide open position and run the CVS pump
for twenty minutes. Record the calibration data.
(6) Reset the restrictor valve to a more restricted condition in
an increment of pump inlet depression (about 4" H?0 (1.0 kPa) that
will yield a minimum of six data points for the total calibration.
Allow the system to stabilize for 3 minutes and repeat the data
acquisition.
(7) Data analysis:
(i) The air flow rate, Qs, at each test point is calculated in
standard cubic feet per minute from the flowmeter data using the
manufacturer's prescribed method.
(ii) The air flow rate is then converted to pump flow, V , in
cubic feet per revolution at absolute pump inlet temperature and
pressure.
-16-
-------
VARIABLE FLOW
RESTRICTOR
TEMPERATURE
INDICATOR
ETI
SURGE
CONTROL
VALVE
MANOMETER
Figure
— PDP-CVS CALIBRATION CONFIGURATION
-------
= 2ix _£x 29.92
o " n 528 P
P
Where:
3 3
V = Pump flow, ft / revolution (m /revolution) at T , P
o P P
Qs = Meter air flow rate in standard cubic feet per
minute, standard conditions are 68°F, 29.92 in. Hg
(20°C, 101.3 kPa).
n = Pump speed in revolutons per minute.
T = Pump inlet temperature, R(K)
p = PTI + 460
for SI units, T = PTI + 273
P
P = Absolute pump inlet pressure, in. Hg (kPa)
P = P - PPI (SP.GR./13.57)
for SI units, P = P - PPI
p B
Where:
P = barometric pressure, in. Hg (kPa)
B
PPI = Pump inlet depression, in. fluid (kPa)
SP. GR. = Specific gravity of manometer fluid relative to water.
(iii) The correlation function at each test point is then
calculated from the calibration data:
Where:
X = correlation function.
o
AP = The pressure differential from pump inlet to pump
P outlet, in. Hg (kPa)
= P - P
e p
P = Absolute pump outlet pressure, in. Hg (kPa)
8 = P + PPO (SP. GR./13.57)
for SI units, P = P_ + PPO
e D
Where:
PPO = Pressure head at pump outlet, in. fluid (kPa)
-17-
-------
(iv) A linear least squares fit is performed to generate the
calibration equations which have the forms:
V = D - M(X )
8 - A°- B(AP°)
D , M, A, and B are the slope-intercept constants describing the
lines.
(8) A CVS system that has multiple speeds should be calibrated
on each speed used. The calibration curves generated for the ranges
will be approximately parallel and the intercept values, D , will
increase as the pump flow range decreases.
(9) If the calibration has been performed carefully, the calculated
values from the equation will be within +0.50% of the measured value
of V . Values of M will vary from one pump to another, but values of
D for pumps of the same make, model, and range should agree within +
3% of each other. Particulate influx from use will cause the pump
slip to decrease as reflected by lower values for M. Calibrations
should be performed at pump start-up and after major maintenance to
assure the stability of the pump slip rate. Analysis of mass injection
data will also reflect pump slip stability.
(b) CFV calibration.
(1) Calibration of the Critical Flow Venturi (CFV) is based upon
the flow equation for a critical venturi. Gas flow is a function of
inlet pressure and temperature:
Where:
Q = Flow
K = Calibration coefficient
P = Absolute pressure
T = Absolute temperature
The calibration procedure described below establishes the value of
the calibration coefficient at measured values of pressure, temperature
and air flow.
(1) The manufacturers recommended procedure shall be followed
for calibrating electronic portions of the CFV.
(2) Measurements necessary for flow calibration are as follows:
-18-
-------
CALIBRATION DATA MEASUREMENTS
PARAMETER
SYM
UNITS
TOLERANCES
0Barometric Pressure
(corrected)
°Air temperature,
flowmeter
°Pressure depression
upstream of LFE
°Pressure drop across
LFE matrix
°Air flow
°CFV inlet depression
°Temperature at venturi
inlet T
•y
°Specific gravity of manometer
B
ETI
EPI
EDP
in. Hg (kPa)
°F (8C)
in. H20 (kPa)
in. H20 (kPa)
f t/min. (m/min.)
in. fluid (kPa)
°F (°C)
+.01 in. Hg (+.034 kPa)
+ .1°F (+.056°C)
+.05 in. H20 (+.012 kPa)
+.005 in. H.O (+.001 kPa)
+.5%
+.05 in. fluid (+.022 kPa)
+.5°F (+.28°C)
fluid (1.75 oil)
Sp. Gr.
(3) Set up equipment as shown in Figure 7 and check for leaks.
Any leaks between the flow measuring device and the critical flow
venturi will seriously affect the accuracy of the calibration.
(4) Set the variable flow restrictor to the open position, start
the blower and allow the system to stabilize. Record data from all
instruments.
(5) Vary the flow restrictor and make at least 8 readings
across the critical flow range of the venturi.
(6) Data analysis. The data recorded during the calibration are
to be used in the following calculations:
(i) The air flow rate, Qs, at each test point is calculated in
standard cubic feet per minute from the flow meter data using the
manufacturer's prescribed method.
(ii) Calculate values of the calibration coefficient for each
test point:
K =
v
-19-
-------
CVS DUCT
SAMPLER DUCT
SURGE CONTROL
VALVE
VARIABLE FLOW
RESTRICTOR
jgjgggB&gsfijL ^
ETI
MANOMETER
FIGURE 7 CFV-CVS CALIBRATION CONFIGURATION
-------
Where:
Q = Flow rate in standard cubic feet per minute,
8 standard conditions are 68°F, 29.92 in. Hg
(20°C, 101.3 kPa).
T = Temperature at venturi inlet, R(K).
P = Pressure at venturi inlet, mm Hg (kPa)
V = P - PPI (SP. GR./13.57).
for SI units P = P_ - PPI
v B
Where:
PPI = Venturi inlet pressure depression, in. fluid (kPa).
SP. GR. = Specific gravity of manometer fluid, relative
to water.
(iii) Plot K as a function of venturi inlet pressure. For
sonic flow K will have a relatively constant value. As pressure
decreases (vacuum increases) the venturi becomes unchecked and K
decreases. See Figure 8.
(iv) For a minimum of 8 points in the critical region calculate
an average K and the standard deviation.
(v) If the standard deviation exceeds 0.3% of the average K
take corrective action. v
(c) CVS System Verification.
The following "gravimetric" technique can be used to verify that
the CVS and analytical instruments can accurately measure a mass of
gas that has been injected into the system. (Verification can also be
accomplished by constant flow metering using critical flow orfice
devices.)
(1) Obtain a small cylinder that has been charged with pure
propane or carbon monoxide gas (caution—carbon monoxide is poison-
ous) .
(2) Determine a reference cylinder weight to the nearest 0.01
grams.
(3) Operate the CVS in the normal manner and release a quantity
of pure propane or carbon monoxide into the system during the sampling
period (approximately 5 minutes).
-20-
-------
OPERATING
RANGE
Kv
INLET DEPRESSION (WH2O)
FIGURE 8 —SONIC FLOW CHOKING
-------
(4) The calculations of section 138 are performed in the normal
way except, in the case of propane. The.density of propane (17.30
g/ft /carbon atom (0.6109 kg/m /carbon atom)) is used in place of the
density of exhaust hydrocarbons. In the case of carbon monoxide, the
density of 32.97 g/ft (1.164 kg/m ) is used.
(5) The gravimetric mass is subtracted from the CVS measured
mass and then divided by the gravimetric mass to determine the percent
accuracy of the system.
(6) The cause for any discrepancy greater than +2% must be found
and corrected.
118 Hydrocarbon analyzer calibration.
The FID hydrocarbon analyzer shall receive the following initial
and periodic calibration (The HFID shall be operated to a set point +
10°F (+ 5.5°C) between 300 and 390°F (149 and 199°C). ~
(a) Initial and periodic optimization of detector response.
Prior to its introduction into service and annually thereafter the FID
hydrocarbon analyzer shall be adjusted for optimum hydrocarbon response:
(1) Follow the manufacturer's instructions for instrument
startup and basic operating adjustment using the appropriate fuel and
zero grade air.
(2) Optimize on the most common operating range. Introduce into
the analyzer, a propane in air mixture with a propane concentration
equal to approximately 90% of the most common operating range.
(3) Select an operating fuel flow rate that will give near
maximum response and least variation in response with minor fuel flow
variations.
(4) To determine the optimum air flow, use the fuel flow setting
determined above and vary air flow.
(5) After the optimum flow rates have been determined, they are
recorded for future reference.
(b) Initial and periodic determination of oxygen effect. Prior
to its introduction into service and at least annually thereafter the
FID hydrocarbon analyzer shall be checked to determine the effect of
oxygen in the sample upon instrument response:
(1) Zero the analyzer on nitrogen (N~) zero gas; check the zero
by using zero grade air; differences in zero reading of more than 2%
will require corrective action.
-21-
-------
(2) The following blends of propane shall be used to determine
the effect of oxygen (P2> in the sample.
Propane in N-
Propane in 9.5 to 10.5% 0-, balance N
Propane in zero grade air
The volume concentration of propane in the mixtures should be
equal to approximately 90% of the most common operating range. The
zero shall be checafter each mixture is measured. If the zero has
changed, the measurement shall be repeated.
(3) If the response to propane in air differs by more than 3%
from the response to propane in the 10% 0-/90% N~ mixture, or differs
by more than 5% from the response to propane in N.; corrective action
will be required.
(4) If the response to propane in N. differs by more than 2%
from the response to propane in 10% 0^/90% N»; corrective action will
be required.
(c) Initial and periodic calibration. Prior to its introduction
into service and monthly thereafter the FID hydrocarbon analyzer shall
be calibrated on all normally used instrument ranges. Use the same
flow rate as when analyzing samples.
(1) Adjust analyzer to optimize performance.
(2) Zero the hydrocarbon analyzer with zero grade air.
(3) Calibrate on each normally used operating range with propane
in air calibration gases having nominal concentrations of 50 and 100%
of that range.
119 Carbon monoxide analyzer calibration.
The NDIR carbon monoxide analyzer shall receive the following
initial and periodic calibrations:
(a) Initial and periodic interference check. Prior to its
introduction into service and annually thereafter the NDIR carbon
monoxide analyzer shall be checked for response to water vapor and
(1) Follow the manufacturer's instructions for instrument
startup and operation. Adjust the analyzer to optimize performance on
the most sensitive range.
-22-
-------
(2) Zero the carbon monoxide analyzer with either zero grade air
or zero grade nitrogen.
(3) Bubble a mixture of 3% CCL in N_ through water at room
temperature and record analyzer response.
(4) An analyzer response of more than 1% of full scale for
ranges above 300 ppm full scale or of more than 3 ppm on ranges below
300 ppm full scale will require corrective action. (Use of condition-
ing columns is one form of corrective action which may be taken.)
(b) Initial and periodic calibration. Prior to its introduction
into service and monthly thereafter the NDIR carbon monoxide analyzer
shall be calibrated.
(1) Adjust the analyzer to optimize performance.
(2) Zero the carbon monoxide analyzer with either zero grade air
or zero grade nitrogen.
(3) Calibrate on each normally used operating range with carbon
monoxide in N_ calibration gases having nominal concentrations of 15,
30, 45, 60, 75 and 90% of that range. For each range calibrated, if
the deviation from a least-squares best-fit straight line is 2% or
less of the value at each data point, concentration values may be
calculated by use of a single calibration factor for that range. If
the deviation exceeds 2% at any point, the best-fit non-linear equa-
tion which represents the data to within 2% of each test point shall
be used to determine concentration.
120 Oxides of nitrogen analyzer calibration.
The Chemiluminescent oxides of nitrogen analyzer shall receive
the following initial and periodic calibration.
(a) Prior to its introduction into service and weekly thereafter
the chemiluminescent oxides of nitrogen analyzer shall be checked for
NO- to NO converter efficiency. Figure 9 is a reference for the
following steps:
(1) Follow the manufacturer's instructions for instrument
startup and operation. Adjust the analyzer to optimize performance.
(2) Zero the oxides of nitrogen analyzer with zero grade air or
zero grade nitrogen.
(3) Connect the outlet of the NOx generator to the sample inlet
of the oxides of nitrogen analyzer which has been set to the most
common operating range.
-23-
-------
FLOW CONTROL
SOLENOID VALVE
O2 OR AIR
SUPPLY
D
] 1 5 V.A.C.
J
OZONATOR
ANALYZER
INLET
CONNECTOR
NO/N2 I L
SUPPLY ' '
(SEE FIG. 3 l FOR SYMBOL LEGEND)
Figure 9 —NOx CONVERTER EFFICIENCY DETECTOR
-------
(4) Introduce into the NOx generator analyzer-system an NO in
nitrogen (N_) mixture with a NO concentration equal to approximately
80% of the most common operating range. The NO- content of the gas
mixture shall be less than 5% of the NO concentration.
(5) With the oxides of nitrogen analyzer in the NO mode, record
the concentration of NO indicated by the analyzer.
(6) Turn on the NOx generator 0- (or air) supply and adjust the
0» (or air) flow rate so that the NO indicated by the analyzer is
about 10% less than indicated in step 5. Record the concentration of
NO in this NO + 0_ mixture.
(7) Switch the NOx generator to the generation mode and adjust
the generation rate so that the NO measured on the analyzer is 20% of
that measured in step 5. There must be at least 10% unreacted NO at
this point. Record the concentration of residual NO.
(8) Switch the oxides of nitrogen analyzer to the NOx mode and
measure total NOx. Record this value.
(9) Switch off the NOx generation but maintain gas flow through
the system. The oxides of nitrogen analyzer will indicate the NOx in
the NO + 0_ mixture. Record this value.
(10) Turn off the NOx generator 0- (or air) supply. The analyzer
will now indicate the NOx in the original NO in N« mixture. This
value should be no more than 5% above the value indicated in step 4.
(11) Calculate the efficiency of the NOx converter by substituting
the concentrations obtained into the following equation:
% Eff . = 1 4- -- x 10°
. = (
where a = concentration obtained in step 8
b = concentration obtained in step 9
c = concentration obtained in step 6
d = concentration obtained in step 7
If converter efficiency is not greater than 90% corrective action will
be required.
(b) Initial and periodic calibration. Prior to its introduction
into service and monthly thereafter the chemiluminescent oxides of
nitrogen analyzer shall be calibrated on all normally used instrument
ranges. Use the same flow rate as when analyzing samples. Proceed as
follows:
-24-
-------
(1) Adjust analyzer to optimize performance.
(2) Zero the oxides of nitrogen analyzer with zero grade air or
zero grade nitrogen.
: (3) Calibrate on each normally used operating range with NO in
N9 calibration gases with nominal concentrations of 50 and 100% of
tfiat range.
121 Carbon dioxide analyzer calibration.
Prior to its introduction into service and monthly thereafter the
NDIR carbon dioxide analyzer shall be calibrated:
(a) Follow the manufacturer's instructions for instrument
startup and operation. Adjust the analyzer to optimize performance.
(b) Zero the carbon dioxide analyzer with either zero grade air
or zero grade nitrogen.
(c) Calibrate on each normally used operating range with carbon
dioxide in N» calibration gases with nominal concentrations of 15, 30,
45, 60, 75 and 90% of that range. For each range calibrated, if the
deviation from a least-squares best-fit straight line is 2% or less of
the value at each data point, concentration values may be calculated
by use of a single calibration factor for that range. If the deviation
exceeds 2% at any point, the best-fit non-linear equation which repre-
sents the data to within 2% of each test point shall be used to deter-
mine concentration.
122 Calibration of other equipment.
Other test equipment used for testing shall be calibrated as
often as required by the manufacturer or as necessary according to
good practice.
123 Test procedures, overview.
(a) The overall test consists of prescribed sequences of fueling,
parking and operating conditions. Vehicles are either tested for only
exhaust emissions or are tested for exhaust and evaporative emissions.
The evaporative portion of the test procedure occurs before and after
the exhaust emission test, and, in some cases, during the exhaust
emission test.
(b) The exhaust emission test is designed to determine hydro-
carbon, carbon monoxide, and oxides of nitrogen mass emissions while
simulating an average trip in an urban area of 7.5 miles (12.1 km).
The test consists of engine startups and vehicle operation on a chassis
dynamometer, through a specified driving schedule. A proportional part
of the diluted exhaust emissions is collected continuously for subsequent
-25-
-------
analysis, using a constant volume (variable dilution) sampler.
(Diesel dilute exhaust is continuously analyzed for hydrocarbons using
a heated sample line and analyzer).
(c) The evaporative emission test (gasoline fueled vehicles
only) is designed to determine hydrocarbon evaporative emissions as a
consequence of diurnal temperature fluctuation, urban driving, and hot
soaks during parking. It is associated with a series of events repre-
sentative of a motor vehicle's operation, which result in hydrocarbon
vapor losses. The test procedure is designed to measure:
(1) Diurnal breathing losses resulting from daily temperature
changes, measured by the enclosure technique;
(2) Running losses from suspected sources (if indicated by
engineering analysis or vehicle inspection) resulting from a simulated
trip on a chassis dynamometer, measured by carbon traps; and
(3) Hot soak losses which result when the vehicle is parked and
the hot engine is turned off, measured by the enclosure technique.
(d) Except in cases of component malfunction or failure, all
emission control systems installed on or incorporated in a motor
vehicle shall be functioning during all procedures in this section.
124 Transmissions.
(a) All test conditions shall be run with automatic and automatic
stick shift transmissions in "Drive" (highest gear); manual transmis-
sions shall be run in highest gear, except as noted. Automatic stick-
shift transmissions may be shifted as manual transmissions if specified
by the manufacturer.
(b) Cars equipped with free-wheeling or overdrive units shall be
tested with these units locked out of operation.
(c) Idle modes shall be run with automatic transmissions in
"Drive" and the wheels braked, manual transmissions shall be in gear
with the clutch disengaged; except first idle, see sections 132 and
133.
(d) The vehicle shall be driven with minimum accelerator pedal
movement to maintain the desired speed.
(e) Acceleration modes shall be driven smoothly. Automatic
transmissions shall shift automatically through the normal sequence of
gears; manual transmissions shall be shifted as recommended by the
manufacturer with the operator releasing the accelerator pedal during
each shift and accomplishing the shift with minimum time. If the
vehicle cannot accelerate at the specified rate, the vehicle shall be
-26-
-------
operated with the accelerator pedal fully depressed until the vehicle
speed reaches the value prescribed for that time in the driving schedule.
(f) The deceleration modes shall be run in gear using brakes or
accelerator pedal as necessary to maintain the desired speed. Manual
transmission vehicles shall have the clutch engaged and shall not
change gears from the previous mode. For those modes which decelerate
to zero, manual transmission clutches shall be depressed when the
speed drops below 15 mph (24 kph), when engine roughness is evident,
or when engine stalling is imminent.
(g) Manual transmissions will be down shifted at the beginning
of or during a power mode if recommended by the manufacturer or if the
engine obviously is lugging.
(h) If shift speeds are not recommended by the manufacturer,
manual transmission vehicles shall be shifted from first to second
gear at 15 mph (24 kph), from second to third gear at 25 mph (40 kph),
and, if so equipped, from third to fourth gear at 40 mph (64 kph).
Fifth gear, if so equipped, may be used at the manufacturers option.
(i) If a four- or five- speed manual transmission has a first
gear ratio in excess of 5:1, follow the procedure for three- or four-
speed vehicles as if the first gear did not exist.
125 Road load power and inertia weight determination.
(a) Flywheels, electrical or other means of simulating inertia
as shown in the following table shall be used. If the equivalent
inertia specified is not available on the dynamometer being used, the
next higher equivalent inertia (not to exceed 250 Ibs) available shall
be used.
Loaded vehicle weight
(pounds)
Up to 1,125
T 1 9ft f n 1 17S -
^ ^7fi t-« ^ fi")ci
i f.'jf. *-n 1 875
1 Q7fi f-n O IOC
9 i jc. 4-0 o •37';_ _
? "376 fr> 9 fi?5 - -
2 626 f-n 2 875
2 876 t-n "} 250
•} 251 f-n "} 75(1
1 751 t-n L 250
A OS! «-n /. -jK.n
A 751 t-n 5 250
S 2 SI f-n S 7 SO
Equivalent Road load
inertia power at
weight 50 mph
(pounds) (horsepower)
1,000
1,250
1,500
1,750
2,000
2,250
2,500
2,750
3,000
3,500
4,000
4,500
5,000
5,500
s snn
5.9
6.5
7.1
7.7
8.3
8.8
9.4
£.9
10.3
11.2
12.0
12.7
13.4
13.9
1 A. L
-27-
-------
(b) Power absorption unit adjustment.
(1) The power absorption unit shall be adjusted to reproduce
road load power at 50 mph true speed. The indicated road load power
setting shall take into account the dynamometer friction. The relation-
ship between road load (absorbed) power and indicated road load power
for a particular dynamometer shall be determined by the procedure
outlined in section 116 or other suitable means.
(2) The road load power listed in the table above shall be used
or the vehicle manufacturer may determine the road load power by an
alternate procedure or the vehicle manufacturer may determine the road
load power by the following procedure and request its use:
(i) Gasoline fueled vehicles.
(A) Measuring the absolute manifold pressure of a representative
vehicle, of the same equivalent inertia weight class, when operated on
a level road under balanced wind conditions at a true speed of 50 mph
(80 kph), and
(B) Noting the dynamometer indicated road load horsepower
setting required to reproduce that manifold pressure when the same
vehicle is operated on the dynamometer at a true speed of 50 mph. The
tests on the road and on the dynamometer shall be performed with the
same vehicle ambient absolute pressure (usually barometric), i.e.,
within +5 mm Hg (+0.7 kPa).
(C) The road load power shall be determined according to the
procedure outlined in section 116 and adjusted according to the
following if applicable.
(ii) Diesel vehicles.
(A) Measuring the fuel flow rate of a representative vehicle of
the same equivalent inertia weight class, when operated on a level
road under balanced wind conditions at a true speed of 50 mph, and
(B) Noting the dynamometer indicated road load horsepower
setting required to reproduce that fuel flow rate when the same vehicle
is operated on the dynamometer at a true speed of 50 mph (80 kph). The
tests on the road and on the dynamometer shall be performed with the
same vehicle ambient absolute pressure (usually barometric), i.e.
within +5 mm Hg (+0.7 kPa).
(C) The road load power shall be determined according to the
procedure outlined in section 116 and adjusted according to the
following if applicable.
-28-
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126 Test,sequence, general requirements.
The test sequence shown in Figure 10 shows the steps encountered
as the test vehicle undergoes the procedures subsequently described to
determine conformity with the standards set forth. Ambient temperature
levels encountered by the test vehicle throughout the test sequence
shall not be less than 68°F.. (20°C) nor more than 86°F (3Q8C). The
vehicle shall be approximately level during all phases of the test
sequence to prevent abnormal fuel distribution.
127 Vehicle preparation.
(a) For gasoline fueled vehicles prepare the fuel tank(s) for
recording the temperature of the prescribed test fuel at the approximate
mid volume of the fuel.
(b) Provide additional fittings and adapters, as required, to
accommodate a fuel drain at the lowest point possible in the tank(s)
as installed on the vehicle.
128 Vehicle preconditioning.
*.
(a) The vehicle shall be moved to the test area and the following
operations performed:
(1) The fuel tank(s) shall be drained through the provided -
fueled tank(s) drain(s) and filled in the normal fashion to contain
approximately 2 gallons (7.57 liters) of the specified test fuel,
section 111 (for diesel powered vehicles the tank shall be filled to
the prescribed "tank fuel volume". When additional preconditioning,
as described in (a)(3) is to be performed, additional fuel may be
added up to the prescribed "tank fuel volume". For the above operations
the evaporative emission control system shall neither be abnormally
purged nor abnormally loaded.
NOTE: "Tank fuel volume" means the volume of fuel in the fuel
tank prescribed to be 40% of nominal tank capacity rounded to the
nearest tenth of U.S. gallon.
(2) Within one hour of being fueled the vehicle shall be placed,
either by being driven or pushed, on a dynamometer and operated through
one Urban Dynamometer Driving Schedule test procedure, see section 113 and
Appendix I of the Federal Register. A gasoline fueled test vehicle
may not be used to set dynamometer horsepower.
(3) For those unusual circumstances where additional precondi-
tioning is desired to insure that the evaporative emission control
system is stabilized, such preconditioning shall consist of an initial
one hour minimum soak and, one, two or three driving cycles of the.
UDDS, as described in (a)(2), each followed by a soak of at least one
-29-
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DYNO PRECONDITIONING
«HEAT FUKL-1 HOUR
•60-84°F
DIURNAL
ENCLOSURE
TEST
1 HOUR MAX.
5 MIN. MAX.
12-36 HOURS
(no max. for
diesels)
0-1 HOUR
*~1
COLD START EXHAUST TEST g
EVAP TEST NOT
PERFORMED
HC RUNNING 1
LOSSES-AS REQ |
1
HOT START EXHAUST TEST
HOT SOAK
ENCLOSURE
TEST
10-MIN.
5 MIN. MAX.
Figure 10 TEST SEQUENCE
-------
hour with engine off, engine compartment cover closed and cooling fan
off. The vehicle may be driven off the dynamometer following each
UDDS for the soak period.
(b) Within five minutes of completion of preconditioning the
vehicle shall be driven off the dynamometer and parked. The vehicle
shall be stored for not less than 12 hours nor for more than 36 hours
(except diesel fueled vehicles which have no maximum time limitation)
prior to the cold start exhaust test. (Gasoline fueled vehicles
undergo a one hour diurnal heat build prior to the cold start exhaust
test. A wait of up to one hour is permitted between the end of the
diurnal heat build and the beginning of the cold start exhaust test.
See section 126 and Figure 10.)
(c) Vehicles to be tested for evaporative emissions shall be
processed in accordance with procedures in sections 129 through 134.
Vehicles to be tested for exhaust emissions only shall be processed
according to sections 129 through 133.
129 Diurnal breathing loss test.
(a)(1) Following vehicle preparation and vehicle preconditioning
procedures described in section 127 and section 128, the test vehicle
shall be allowed to soak for a period of not less than 12 or more than
36 hours prior to the exhaust emission test. The diurnal test shall
take place not less than 10 or more than 35 hours after the end of the
preconditioning procedure. The start of the exhaust test shall follow
the end of the diurnal test within one hour.
(2) Gasoline fueled vehicles to be tested for exhaust emissions
only, shall undergo the diurnal heat build. Since no evaporative
measurements are necessary, an evaporative enclosure is not required.
(b) The evaporative emission enclosure shall be purged for
several minutes immediately prior to the test.
NOTE: If at anytime the hydrocarbon concentration exceeds 15,000
ppm C the enclosure should be immediately purged. This concentration
provides a 4:1 safety factor against the lean flammability limit.
(c) The FID hydrocarbon analyzer shall be zeroed and spanned
immediately prior to the test.
(d) If not already on, the evaporative enclosure mixing fan
shall be turned on at this time.
(e) Immediately prior to the diurnal breathing loss test, the
fuel tank(s) of the prepared vehicle shall be drained and recharged
with the specified test fuel, section 111, to the prescribed "tank,
fuel volume". The temperature of the fuel prior to its delivery to
the fuel tank shall be between 50 and 60°F (10 and 16°C).
-30-
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(f) The test vehicle, with the engine shut off, shall be moved
into the evaporative emission enclosure,.the test vehicle windows and
luggage compartments shall be opened, the fuel tank temperature sensor
shall be connected to the temperature recording system, and, if required,
the heat source shall be properly positioned with respect to the fuel
tank(s) and/or connected to the temperature controller.
(g) The enclosure doors shall be closed and sealed.
(h) The temperature recording system shall be started.
(i) When the fuel temperature recording system reaches 60 + 1°F
(16+0.5°C), immediately:
(1) Analyze enclosure atmosphere for hydrocarbons and record.
This is the initial (time = 0 minutes) hydrocarbon concentration,'
C r., section 137. : ;
(2) Start diurnal heat build and record time. This commences
the 60+2 minute test period.
(j) The fuel shall be heated in such a way that its temperature
change conforms to the following function to within + 2°F (+ 1.1°C):
F = 60 + 0.4t
for SI units, C = 15.556 + 2/9t
Where:
F = fuel temperature, °F
C = fuel temperature, °C
t = time since beginning of test, minutes.
After 60+2 minutes of heating, the fuel temperature shall be 84 +
1°F (29 +~0.5°C).
(k) The FID hydrocarbon analyzer shall be zeroed and spanned
immediately prior to the end of the diurnal test.
(1) The end of the diurnal breathing loss test occurs 60+2
minutes after the heat build begins, subparagraph (i)(2). Analyze the
enclosure atmosphere for hydrocarbons and record. This is the final
(time = 60 minutes) hydrocarbon concentration, C f, section 137.
The time (or elapsed time) of this analysis shall be recorded.
(m) The heat source shall be turned off and the enclosure doors
unsealed and opened.
(n) The heat source shall be moved away from the vehicle, if
required, and/or disconnected from the temperature controller, the
fuel tank temperature sensor shall be disconnected from the temperature
recording system, the test vehicle windows and luggage compartments
may be closed and the test vehicle, with the engine shut off, shall be
removed from the evaporative emission enclosure.
-31-
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130 Running loss test.
(a) If an engineering analysis or vehicle inspection indicate
the possibility of evaporative emissions during vehicle operation,
evaporative emission running loss measurements shall be made during
the cold transient and stabilized portion of the exhaust emission
test. Since running loss measurements cannot be made in the enclosure,
the equipment described in the Federal Register shall be used to
collect these emissions.
(1) The procedure in section 131 shall be followed.
(2) Prior to the initiation of the cold start exhaust emission
test, the vapor loss measurement system shall be connected to all
suspected sources of running loss evaporative emissions.
(3) The cold start transient and stabilized exhaust emission
test portions shall be conducted according to the procedures of section
131 through section 133.
(4) Within one minute after the end of the stabilized exhaust
emission test, the vapor loss measurement system shall be disconnected
from the vehicle and the inlets and outlets sealed.
(5) Within one hour from the end of the running loss measurement,
weigh the vapor collection traps.
131 Dynamometer procedure.
(a) The dynamometer run consists of two tests, a "cold" start
test after a minimum 12-hour and a maximum 36 hour soak according to
the provisions of section 128 and section 129 and a "hot" start test
following the "cold" start by 10 minutes. Engine startup (with all
accessories turned off), operation over the driving schedule, and
engine shutdown make a complete cold start test. Engine startup and
operation over the first 505 seconds of the driving schedule complete
the hot start test. The exhaust emissions are diluted with ambient
air and a continuously proportional sample is collected for analysis
during each phase. The composite samples collected in bags are analyzed
for hydrocarbons (except diesel hydrocarbons which are analyzed contin-
uously) , carbon monoxide, carbon dioxide, and oxides of nitrogen. A
parallel sample of the dilution air is similarly analyzed for hydrocarbon,
carbon monoxide, and oxides of nitrogen.
(b) During dynamometer operation, a fixed speed cooling fan
shall be positioned so as to direct cooling air to the vehicle in an
appropriate manner with the engine compartment cover open. In the
case of vehicles with front engine compartments, the fan shall be
squarely positioned within 12 inches of the vehicle. In the ease of
vehicles with rear engine compartments (or if special designs make the
above impractical), the cooling fan shall be placed in a position to
-32-
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provide sufficient air to maintain vehicle cooling. The fan capacity
shall normally not exceed 5,300 cfm (2.50 m /s). If, however, the
manufacturer can show that during field operation the vehicle receives
additional cooling, and that such additional cooling is needed to
provide a representative test, the fan capacity may be increased or
additional fans used.
(c) The vehicle speed as measured from the dynamometer rolls
shall be used.
-- (d) Practice runs over the prescribed driving schedule may be
performed for the purpose of finding the minimum throttle action to
maintain the proper speed-time relationship, or to permit sampling
system adjustments.
NOTE: When using two-roll dynamometers a truer speed-time trace
may be obtained by minimizing the rocking of the vehicle in the rolls.
The rocking of the vehicle changes the tire rolling radius on each
roll. This rocking may be minimized by restraining the vehicle
horizontally (or nearly so) by using a cable and winch.
(e) The drive wheel tires may be inflated up to 45 psig (310
kPag) in order to prevent tire damage. The drive wheel tire pressure
shall be reported with the test results.
(f) If the dynamometer has not been operated during the 2 hour
period immediately preceding the test it shall be warmed up for 15
minutes by operating at 30 raph (48 kph) using a non-test vehicle or as
recommended by the dynamometer manufacturer.
(g) If the dynamometer horsepower must be adjusted manually, it
shall be set within 1 hour prior to the exhaust emissions test phase.
The test vehicle shall not be used to make this adjustment. Dynamometers
using automatic control of preselectable power settings may be set
anytime prior to the beginning of the emissions test.
132 Engine starting and restarting.
(a) Gasoline fueled vehicles. Paragraph (a) applies to gasoline
fueled vehicles.
(1) The engine shall be started according to the manufacturer's
recommended starting procedures. The initial 20 second idle period
shall begin when the engine starts.
(2) Choke operation:
(i) Vehicles equipped with automatic chokes shall be operated
according to the instructions in the manufacturer's operating instructions
or owner's manual including choke setting and "kick-down" from cold
fast idle. The transmission shall be placed in gear 15 seconds after
the engine is started. If necessary, braking may be employed to keep
the drive wheels from turning.
-33-
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(ii) Vehicles equipped with manual chokes shall be operated
according to the manufacturer's operating instructions or owners
manual.
(3) The operator may use the choke, accelerator pedal, etc.
where necessary to keep the engine running.
(4) If the manufacturer's operating instructions or owner's
manual does not specify a warm engine starting procedure, the engine
(automatic and manual choke engines) shall be started by depressing
the accelerator pedal about half way and cranking the engine until it
starts.
(b) Diesel fueled vehicles. The engine shall be started according
^to. the manufacturer's recommended starting procedures. The initial
2O-second-idle period shall begin when the engine starts. The trans-
mission shall be placed in gear 15 seconds after the engine is started.
If necessary, braking may be employed to keep the drive wheels from
turning.
(c) If the vehicle does not start after 10 seconds of cranking,
cranking shall cease and the reason for failure to start shall be
determined. The gas flow measuring device (or revolution counter) on
the constant volume sampler (and the hydrocarbon integrator when
testing diesel vehicles, see section 133, Dynamometer test runs) shall
be turned off and the sample selector valves placed in the "standby"
position during this diagnostic period. In addition, either the CVS
should be turned off or the exhaust tube disconnected from the tail-
pipe during the diagnostic period.
(1) If failure to start is an operational error, the vehicle
shall be rescheduled for testing from a cold start. If failure to
start is caused by vehicle malfunction, corrective action of less than
30 minutes duration may be taken and the test continued. The sampling
system shall be reactivated at the same time cranking is started.
When the engine starts, the driving schedule timing sequence shall
begin. If failure to start is caused by vehicle malfunction and the
vehicle cannot be started, the test shall be voided, the vehicle
removed from the dynamometer, corrective action taken, and the vehicle
rescheduled for test.
(d) If the engine "false starts", the operator shall repeat the
recommended starting procedure (such as resetting the choke, etc.)
(e) Stalling:
(1) If the engine stalls during an idle period, the engine shall
be restarted immediately and the test continued. If the engine cannot
be started soon enough to allow the vehicle to follow the next accelera-
tion as prescribed, the driving schedule indicator shall be stopped.
When the vehicle restarts, the driving schedule indicator shall be
reactivated.
-34-
-------
(2) If the engine stalls during soine operating mode other than
idle, the driving schedule indicator shall be stopped, the vehicle
shall then be restarted and accelerated to the speed required at that
point in the driving schedule and the test continued. During acceleration
to this point, shifting shall be performed in accordance with section
124.
(3) If the vehicle will not restart within 1 minute, the test
shall be voided, the vehicle removed from the dynamometer, corrective
action taken, and the vehicle rescheduled for test.
133 Dynamometer test runs.
(a) The vehicle shall be allowed to stand with the engine ,.,,
turned off for a period of not less than 12 hours or more than 36'
hours before the cold start exhaust emission test. The cold start
exhaust test shall follow the diurnal breathing loss test by^not more
than 1 hour. The vehicle shall be stored prior to the emission test;.
in such a manner that precipitation (e.g. rain or dew) does not occur
on the vehicle. The complete dynamometer test consists of a cold
start drive of 7.5 miles (12.1 km) and simulates a hot start drive of
7.5 miles (12.1 km). The vehicle is allowed to stand on the dynamometer
during the 10 minute time period between the cold and hot start tests;
The cold start test is divided into two periods. The first period,
representing the cold start "transient" phase, terminates at the end '
of the deceleration which is scheduled to occur at 505 seconds of the
driving schedule. The second period, representing the "stabilized"
phase, consists of the remainder of the driving schedule including
engine shutdown. The hot start test similarly consists of two periods.
The period, representing the hot start "transient" phase, terminates
at the same point in the driving schedule as the first period of the
cold start test. The second period of the hot start test, "stabilized"
phase, is assumed to be identical to the second period of the cold
start test. Therefore, the hot start test terminates after the first
period (505 seconds) is run.
(b) The following steps shall be taken for each test:
(1) Place drive wheels of vehicle on dynamometer without starting
engine.
(2) Open the vehicle engine compartment cover and position the
cooling fan.
(3) With the sample selector valves in the "standby" position
connect evacuated sample collection bags to the two dilute exhaust and
two dilution air sample collection systems.
(4) Start the Constant Volume Sampler (if not already on), the
sample pumps, the temperature recorder, the vehicle cooling fan and
the heated hydrocarbon analysis recorder (diesel only). (The heat
-35-
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exchanger of the constant volume sampler, if used, diesel hydrocarbon
analyzer continuous sample line and filter (if applicable) should be
preheated to their respective operating temperatures before the test
begins.)
(5) Adjust the sample flow rates to the desired flow rate
(minimum of 10 cfh, 0.28 m /hr) and set the gas flow measuring devices
to zero.
NOTE: CFV-CVS sample flowrate is fixed by the venturi design.
(6) Attach the flexible exhaust tube to the vehicle tailpipe(s).
(7) Start the gas flow measuring device, position the sample
selector valves to direct the sample flow into the "transient" exhaust
sample bag and the "transient" dilution air sample bag, (turn on the
diesel hydrocarbon analyzer system integrator and mark the recorder
chart, if applicable) and start cranking the engine.
(8) Fifteen seconds after the engine starts, place the transmission
in gear.
(9) Twenty seconds after the engine starts, begin the initial
vehicle acceleration of the driving schedule.
(10) Operate the vehicle according to the dynamometer driving
schedule, section 113.
(11) At the end of the deceleration which is scheduled to occur
at 505 seconds, simultaneously switch the sample flows from the "transient"
bags to the "stabilized" bags, switch off gas flow measuring device
No. 1 (and the diesel hydrocarbon integrator No. 1, mark the diesel
hydrocarbon recorder chart) and start gas flow measuring device No. 2
(and diesel hydrocarbon integrator No. 2). As soon as possible, and
in no case longer than 20 minutes after the end of this portion of the
test, transfer the "transient" exhaust and dilution air sample bags,
to the analytical system and process the samples according to section
135. ;
(12) Turn the engine off 2 seconds after the end of-the last
deceleration (at 1,369 seconds).
(13) Five seconds after the engine stops running, simultaneously
turn off gas flow measuring device No. 2 (and the diesel hydrocarbon
integrator No. 2, mark the hydrocarbon recorder chart, if applicable)
and position the sample selector valves to the "standby" position. As
soon as possible, and in no case longer than 20 minutes after the end
of this portion of the test, transfer the "stabilized" exhaust and
dilution air sample bags, to the analytical system and process the
samples according to section 135.
(14) Immediately after the end of the sample period turn off the
cooling fan and close the engine compartment cover.
-36-
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(15) Turn off the CVS or disconnect the exhaust tube.from the
tailpipe of the vehicle.
(16) Repeat the steps in paragraph (b) (2) through (10) of this
section for the hot start test, except only one evacuated sample bag
is required for sampling exhaust gas and one for dilution air. The
step in paragraph (b) (7) of this section shall begin between 9 and 11
minutes after the end of the sample period for the cold start test.
(17) At the end of the deceleration which is scheduled to occur
at 505 seconds, simultaneously turn off gas flow measuring device No.
1 (and diesel hydrocarbon integrator No. 1, mark the diesel hydrocarbon
recorder chart, if applicable) and position the sample selector valve
to the "standby" position. (Engine shutdown is not part of the hot
start test sample period.)
(18) As soon as possible, and in no case longer than 20 minutes
after the end of this portion of the test transfer the hot start
"transient" exhaust and dilution air sample bags, to the analytical
system and process the samples according to section 135.
(19) Disconnect the exhaust tube from the vehicle tailpipe(s)
and drive vehicle from dynamometer.
(20) The constant volume sampler may be turned off, if desired.
(21) Vehicles to be tested for evaporative emissions will proceed
according to section 134. For all others this completes the test
sequence.
134 Hot soak test.
The hot soak evaporative emission test shall be conducted im-
mediately following the hot transient exhaust emission test.
. (a) Prior to the completion of the hot start transient exhaust
emission sampling period, the evaporative emission enclosure shall be
purged for several minutes.
(b) The FID hydrocarbon analyzer shall be zeroed and spanned
immediately prior to the test.
(c) If not already on, the evaporative enclosure mixing fan
shall be turned on at this time.
(d) Upon completion of the hot transient exhaust emission
sampling period, the vehicle engine compartment cover shall be closed,
the cooling fan shall be moved, the vehicle shall be disconnected from
the dynamometer and exhaust sampling system and then driven at minimum
throttle to within 10 feet (3.3 m) of the vehicle entrance to the
enclosure.
-37-
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(e) The test vehicle windows and luggage compartments shall be
opened.
(f) The temperature recording system shall be started.
(g) The vehicle's engine shall be shutoff and the vehicle shall
be pushed into the enclosure. The time" of engine shutoff shall be
noted on the evaporative emission hydrocarbon data recording system.
(h) The enclosure doors shall be closed and sealed within one
minute of engine shutdown and within five minutes after the end of the
exhaust test.
(i) The 60+0.5 minute hot soak begins when the enclosure doors
are sealed. The enclosure atmosphere shall be analyzed and recorded.
This is the initial (time = 0 minutes) hydrocarbon concentration,
C.,.,., for use in calculating evaporative losses, see section 137.
nCl
(j) The test vehicle shall be permitted to soak for a period..of
at least one hour in the enclosure.
(k) The FID hydrocarbon analyzer shall be zeroed and spanned
immediately prior to the end of the test.
(1) At the end of the 60 + 0.5 minute test period, again analyze
the enclosure atmosphere and record time. This is the final (time =
60 minutes) hydrocarbon concentration, C rf, for use in calculating
evaporative losses, see section 137. This operation completes the
evaporative emission measurement procedure.
135 Exhaust sample analysis.
The following sequence of operations shall be performed in conjunction
with each series of measurements:
(a) Zero the analyzers and obtain a stable zero reading.
Recheck after tests.
(b) Introduce span gases and set instrument gains. In order to
avoid corrections, span and calibrate at the same flow rates used to
analyze the test sample. Span gases should have concentrations equal
to approximately 80 percent of full scale. If gain has shifted signifi-
cantly on the analyzers, check the calibrations. Show actual concentra-
tions on chart.
(c) Check zeros; repeat the procedure in paragraphs (a) and (b)
of this section if required.
(d) Check flowrates and pressures.
(e) Measure HC, CO, C0_ and NOx concentrations of samples.
-38-
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(f) For diesel vehicles, continuously record (integrate electron-
ically if desired) dilute hydrocarbon emission levels during test.
Background samples are collected in sample bags and analyzed as above.
(g) Check zero and span points. If difference is greater than
2% of full scale, repeat the procedure in paragraphs (a) through (f).
136 Records required.
The following information shall be recorded with respect to each
test:
(a) Test number.
(b) System or device tested (brief description).
(c) Date and time of day for each part of the test schedule.
(d) Instrument operator.
(e) Driver or operator.
(f) Vehicle: Make - Vehicle identification number - Model
year - Transmission type - Odometer reading - Engine displacement -
Engine family - Evap. family - Idle rpm - Fuel system (fuel injection,
nominal fuel tank(s) capacity, fuel tank(s) location, number of carburetors,
number of carburetor barrels) - Inertia loading - Actual curb weight
recorded at 0 miles - Actual road load at 50 mph (80 kph) and drive
wheel tire pressure, as applicable.
(g) Indicated road load power absorption at 50 mph (80 kph) and
dynamometer serial number. As an alternative to recording the dynamometer
serial number, a reference to a vehicle test cell number may be used,
provided the test cell records show the pertinent information.
(h) All pertinent instrument information such as tuning -
gain - serial number - detector number - range. As an alternative, a
reference to a vehicle test cell number may be used, provided test
cell calibration records show the pertinent instrument information.
(i) Recorder charts: Identify zero, span, exhaust gas, and
dilution air sample traces.
(j) Test cell barometric pressure, ambient temperature and
humidity.
NOTE: A central laboratory barometer may be used; provided that
individual test cell barometric pressures are shown to be within +0.1
percent of the barometric pressure at the central barometer location.
(k) Fuel temperatures, as prescribed.
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(1) Pressure of the mixture of exhaust and dilution air entering
the CVS metering device, the pressure increase across the device, and
the temperature at the inlet. The temperature may be recorded con-
tinuously or digitally to determine temperature variations.
(m) The number of revolutions of the positive displacement pump
accumulated during each test phase while exhaust samples are being
collected. The number of standard cubic feet metered by a critical
flow venturi during each test phase would be the equivalent record for
a CFV-CVS.
(n) The humidity of the dilution air.
NOTE: If conditioning columns are not used (see section 119 and
section 138) this measurement can be deleted. If the conditioning
columns are used and the dilution air is taken from the test cell, the
ambient humidity can be used for this measurement.
(o) Temperature set point of the heated sample line and heated
hydrocarbon detector temperature control system (for diesel vehicles
only).
137 Calculations; evaporative emissions.
The calculation of the net hydrocarbon mass change in the enclosure
is used to determine the diurnal and hot soak mass emissions. The
mass is calculated from initial and final hydrocarbon concentrations
in ppm carbon, initial and final enclosure ambient temperatures,
initial and final barometric pressures, and net enclosure volume using
the following equation:
= k V x 10
n
-4
CHCf
Bf CHCi PBi
Tf T.
Where:
= hydrocarbon mass, g.
C = hydrocarbon concentration as ppm carbon.
3 3
V = net enclosure volume, ft fm ) as determined by
subtracting 50 ft (1.42 m ) (volume of vehicle
with trunk and windows open) from the enclosure
volume.
PB = barometric pressure, in. Hg (kPa).
T = enclosure ambient temperature, R (K).
-40-
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k = .208 (12 + H/C)
for SI units, k = 1.2 (12 + H/C).
Where:
H/C = Hydrogen-carbon ratio.
H/C =2.33 for diurnal emissions.
H/C =2.2 for hot soak emissions.
i = indicates initial reading.
f = indicates final reading.
138 Calculations; exhaust emissions.
The final reported test results shall be computed by use of the
following formula:
(a) For light duty vehicles and light duty trucks:
Y = (0.43 Y + 0.57 Y, + Y )/7.5
wm ct nt s
Where:
Y = Weighted mass emissions of each pollutant, i.e.,
HC, CO, or NOx, in grams per vehicle mile.
Y =* Mass emissions as calculated from the "transient"
ct
phase of the cold start test, in grams per test
phase.
Y =•= Mass emissions as calculated from the "transient"
phase of the hot start test, in grams per test
phase.
Y = Mass emissions as calculated from the "stabilized"
phase of the cold start test, in grams per test
phase.
(b) The mass of each pollutant for each phase of both the cold
start test and the hot start test is determined from the following:
(1) Hydrocarbon mass:
HC * V . X Density.,., X (HC /1,000,000)
mass mix 7HC cone '
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(2) Oxides of nitrogen mass:
N0xmass = Vmix X DenSlty N02 X ^ X (N°Xconc /
(3) Carbon monoxide mass:
CO - V , ' X Density.,^ X (O) 71,000,000)
mass mix CO cone
(4) Carbon dioxide mass:
C00 - V . X Density.. X (CO. /100)
2mass mix •'CO- 2conc
(c) Meaning of symbols:
(1) HC - Hydrocarbon emissions, in grams per test
, mass
phase.
3
DensityHf, =»Density of hydrocarbons is 16.33 g/ft
(.5767 kg/m ), assuming an average carbon to hydrogen
ratio of 1:1.85, at 68°F (20°C) and 760 mm Hg (101.3
kPa) pressure.
HC » Hydrocarbon concentration of the dilute ex
haust sample corrected for background, in ppm carbon
equivalent, i.e., equivalent propane X 3.
Where:
HCconc ' HCe - HCd
HC == Hydrocarbon concentration of the dilute exhaust
sample or, for diesel, average hydrocarbon concentration
of the dilute exhaust sample as calculated from the
integrated HC traces, in ppm carbon equivalent.
HC, » Hydrocarbon concentration of the dilution air
as measured, in ppm carbon equivalent.
(2) N^x - Oxides of nitrogen emissions, in grams per
test phase.
Density =•= Density of oxides of nitrogen is 54.16
3 2 3
g/ft (1.913 kg/m ), assuming they are in the form of
nitrogen dioxide, at 68°F (20°C) and 760 mm Hg (101.3
kPa) pressure.
NOx » Oxides of nitrogen concentration of the
dilute exhaust sample corrected for background, in ppm.
NOx = NOx - NOx, (1-1/DF)
cone e d
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Where:
NOx - Oxides of nitrogen concentration of the dilute
exhaust sample as measured, in ppm.
NOx, * Oxides of nitrogen concentration of the dilute
air as measured, in ppm.
(3) CO » Carbon monoxide emissions, in grams per test
mass
phase.
3
Densityro ^-Density of carbon monoxide is 32.97 g/ft
(1.164 Kg/in ), at 68°F (20°C) and 760 mm Hg (101.3
kPa) pressure.
CO = Carbon monoxide concentration of the dilute
£OC1C
exhaust sample corrected for background, water vapor,
and CO- extraction, in ppm.
Where:
Where:
Where:
CO
cone
C°e ~ C°d
CO = Carbon monoxide concentration of the dilute
exnaust sample volume corrected for water vapor and
carbon dioxide extraction, in ppm. The calculation
assumes the carbon to hydrogen ratio of the fuel is
1:1.85.
CO
(1-0.01925 CO- - 0.000323 R) CO
2e em
CO =* Carbon monoxide concentration of the dilute
fm
aust sample as measured, in ppm.
CO- » Carbon dioxide concentration of the dilute
exnaust sample, in percent.
R = Relative humidity of the dilution air, in per
cent (see section 136.
CO, - Carbon monoxide concentration of the dilution
air corrected for water vapor extraction, in ppm.
CO, = (1-0.000323 R) CO,
d dm
CO, = Carbon monoxide concentration of the dilution
air sample as measured, in ppm.
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NOTE: If a CO instrument which meets the criteria specified in
section 110 is used and the conditioning column has been deleted, CO
can be substituted directly for CO and C0dm can be substituted
directly for CO..
(4) C0_ * Carbon dioxide emissions, in grams per test
v ' , 2mass
phase.
3
DensityCO- 5 Density of carbon dioxide is 51.85 g/ft
(1.843 kg/m ), at 68°F (20°C) and 760 mm Hg (101.3
kPa) pressure.
CO- = Carbon dioxide concentration of the dilute
i f* on c*
exhaust sample corrected for background, in percent.
C°2conc •' C°2e ' C°2d
Where:
CO • = Carbon dioxide concentration of the dilution
air as measured, in percent.
(5) DF = 13.4/[CO. + (HC + CO ) 10~4]
/e e e
K^ .=* Humidity correction factor.
Kg - 1/[1-0.0047 (H-75)]
for SI units - 1/[1-0.033 (H-10.7)]
Where:
H = Absolute humidity in grains (grams) of water
per pound (kilogram) of dry air.
H - [(43.478) R X P,]/[P_ - (P. X R /100)]
a a B da
for SI units, H - [(6.0266) R X P. ]/[?.. - (P, X R /100) ]
3, Q. jj Cl 3.
RE = Relative humidity of the ambient air, in percent.
P. » Saturated vapor pressure, in mm Hg (kPa) at
the ambient dry bulb temperature.
PB = Barometric pressure, in mm Hg (kPa).
V . = Total dilute exhaust volume in cubic feet per
test phase correctd to standard conditions (528 R
(293 K) and 760 mm Hg (101.3 kPa)).
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For PDP-CVS, Vmlx is:
Vmix - V x N(P -P,)(528 R)
O B ^
(760 mm Hg) (T )
for SI units, Vmix - VQ x.N(Pg - P4)\(293.15 K)
(101.3 kPa) (T )
P
Where:
V = Volume of gas pumped by the positive displacement pump,
in cubic feet (m ) per revolution. This volume is
dependent on the pressure differential across the
positive displacement pump.
N = Number of revolutions of the positive displacement pump
during the test phase while samples are being collected.
P_ = Barometric pressure, in mm Hg (kPa).
D
P, = Pressure depression below atmospheric measured at the
inlet to the positive displacement pump, in mm Hg
(kPa).
T = Average temperature of dilute exhaust entering positive
" displacement pump during test, R(K).
(d) Example calculation of mass values of exhaust emissions
using positive displacement pump:
(1) For the "transient" phase of the cold start test assume the
following: V "0.29344 ft /revolution; N=10,485; R=48.0%; R =48.2%;
Pfi=762 mm Hg;° Pd=22.225 mm Hg; P4=70 mm Hg; T =570 R; HCe=105.8
ppm, carbon equivalent; NOx =11.2 ppm; CO =306\6 ppm; C0_ =1.43%;
HCd=12.1 ppm; N0xd=0.8 ppm;6 C0)dm=15.3 ppm?
Then:
V . = (0.29344)^(10,485) (762-70) (528)/(760)(570)=
mix 2595.0 ft per test phase.
H = (43.478) (48.2) (22.225)/[762-(22.225 x 48.2/100)]
KJJ = 1/[1-0.0047(62-75)] = 0.9424
C0g = [1-0.01925 (1.43)-0.000323 (48)] 306.0 = 293.4 ppm
C0d = [1-0.000323 (48)] 15.3 = 15.1 ppm
DF = 13.4/[1.43 + (105.8 + 293.4) x 10~4] = 9.116
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HC - 105.8-12.1(1-1.9.116) - 95.03 ppm
cone
HC -• (2595) (16.33) (95.03/1,000,000) - 4.027 grams
mass per test phase.
NOx * 11.2-0.8 (1-1/9.116) - 10.49 ppm
cone
NOx - (2595) (54.16) (10.49/1,000,000) (0.9424) » 1.389
mass .
grams per test phase.
CO - 293.4-15.1 (1-1/9.116) - 280.0 ppm
cone
CO - (2595) (32.97) (280/1,000,000) * 23.96 grams per
mass
test phase.
(2) For the stabilized portion of the cold start test assume
that similar calculations resulted in the following:
HC = 0.62 grams per test phase
mass e> f t-
NOx = 1.27 grams per test phase
mass
CO =5.98 'grams per test phase
mass
i
(3) For the "transient" portion of the hot start test assume
that similar calculations resulted in the following:
HC = 0.51 grams per test phase
or r-
NOx =1.38 grams per test phase
uiciss
C0m = 5.01 grams per test phase
UlclSS
(4) Weighted mass emission results:
HCwm * K°-43) (4.027) + (
grams per vehicle mile. %•&•• -••• '-9-~1-5
N°Xwm " t(0'43) d-389) + (0.57) (1.38) + 1.27]/7.5 = 0.354
grams per vehicle mile.
C°wm = [(0.43) (23.96) + (0.57) (5.01) + 5.98J/7.5 = 2.55
grams per vehicle mile.
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