RECOMMENDED PRACTICE
for
DETERMINATION OF EVAPORATIVE EMISSIONS
from
LIGHT DUTY VEHICLES
APRIL 1976
9
OFFICE OF MOBILE SOURCE AIR POLLUTION CONTROL
ANN ARBOR, MICHIGAN
-------
Recommended Practice
for
Determination,of Evaporative Emissions
from
Light Duty Vehicles
April, 1976
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Table of Contents
Section
105 Introduction; structure of subpart. 1
106 Equipment requiredj overview. 1
107 Sampling and analytical system, evaporative 1
emissions.
108 Dynamometer. 3
109 Exhaust Gas sampling system. 4
110 Reserved 1
111 Exhaust Gas analytical system. 7
112 Reserved 9
113 Fuel specifications. 9
114 Analytical gases. 12
115 EPA Urban Dynamometer Driving Schedule. 13
116 .Calibrations, frequency and overview. 15
117 Evaporative ejnissipn enclosure calibrations. 16
118 Dynamometer calibration. ^
119 Constant volume sampler calibration. 21
120 Reserved 30
121 Hydrocarbon analyzer calibration. 30
122 Carbon monoxide analyzer calibration. 31
123 Oxides of nitrogen analyzer calibration. 32
124 Carbon dioxide analyzer calibration. 34
125 Reserved 35
126 Calibration of other equipment. 35
127 Test procedures, overview. 35
128 Transmissions. 36
129 Road load power and inertia weight 37
determination.
130 Test sequence, general requirements. 39
131 Vehicle preparation. 39
132 Vehicle Precprid.itionJ^ng. 39
133 Diurnal breaching loss test. 41
134 Running loss tpest. 43
135 Dynamometer procedure. 43
136 Engine starting and restarting. 45
137 Dynamometer test runs. 46
138 pot soak t;est. 49
139 . Reserved 50
140 Exhaust sample analysis. 50
141 Reserved ' 50
142 Records required. , 50
143 Calculations; evaporative emissions. 52
144 Calculations; exhaus^ emissions. 53
145 Reserved 58
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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 evaporative
emission tests on light duty vehicles and light duty trucks.
(b) Three topics are addressed in this Recommended Practice. Sections
106 through 115 set forth specifications and equipment requirements;
sections 116 through 126 discuss calibration methods and frequency;
test procedures and data requirements are listed (in approximately order
of performance) in sections 127 through 145.
106 EQUIPMENT REQUIRED; OVERVIEW. .
(a) This Recommended Practice contains procedures for both exhaust
and evaporative emissions tests on diesel or gasoline fueled light duty
vehicles and light duty trucks. Certain items of equipment are not
necessary for a particular test, e.g., evaporative enclosure when test-
ing 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 standard.) Section 107 specifies the
necessary equipment.
(2) Exhaust emission tests. All vehicles subject to this Recommended
Practice are tested for exhaust emissions. Diesel and gasoline fueled
vehicles are tested identically with the exception of hydrocarbon measure-
ments; diesel vehicles require a heated hydrocarbon detector, section
109. All gasoline fueled vehicles are either tested for evaporative
emissions or undergo a diurnal heat build, diesel vehicles are excluded
from this requirement. Equipment necessary and specifications appear in
sections 108 through 114.
(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 section 113. Analytical gases are specified in section 114. The
EPA Urban Dynamometer Driving Schedule for use in exhaust testing is
specified in section 115 and Appendix I of the Federal Register.
107 SAMPLING AND ANALYTICAL SYSTEM, EVAPORATIVE EMISSIONS.
(a) Component description (evaporative emissions sampling system).
The following components will be used in evaporative emissions sampling
systems for testing under this Recommended Practice.
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(1) Evaporative emission measurement enclosure. The enclosure
shall be readily scalable, rectangular in shape, with space for personnel
access to all sides of the vehicle. When sealed, the enclosure shall be
gas tight in accordance with section 117. Interior surfaces must be
impermeable to hydrocarbons. One surface should be of flexible, im-
permeable material to allow for minor volume changes, resulting from
temperature changes. Wall design should promote maximum dissipation of
heat, and if artificial cooling is used, interior surface temperatures
shall not be less than 68°F(20°C).
(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. Instrument
bypass flow may be returned to the enclosure. The FID shall have a
response time to 90% of final reading of less than 1.5 s, and be capable
of meeting performance requirements expressed as a function of C , ;
where C , is the specific enclosure hydrocarbon level, in ppm, corre-
sponding to the evaporative emission standard:
(i) Stability of the analyzer shall be better than 0.01 C , ppm
at both zero and C , + 5 ppm over a 15 minute period on all ranges
j S t Cl
used;
(ii) Repeatability of the analyzer, expressed as one standard
deviation, shall be better than 0.005 C , ppm at both zero and C , + 5
11 « SLU Std —
ppm on all ranges used.
(3) Evaporative emission hydrocarbon data recording system.
The electrical output of the FID shall be recorded at least 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 record shall show 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.
Tank f.uel 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 temperature controller
must be capable of controlling the fuel tank temperature during the
diurnal soak to within + 3°F (1.7°C) of the following equation:
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F = T + 0.4 t
o
or for SI units:
C = T + (2/9)t
o
Where:
F = Temperature in °F
C = Temperature in °C
t = Time since start of test in minutes
T = Initial temperature
(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. Two ambient
temperature sensors, connected to provide one average output, shall be
located in the enclosure. These sensors shall be located at the approxi-
mate vertical centerline of each side wall extending 4 inches (nominally)
into the enclosure at a height of 3 + 0.5 ft (0.9 + 0.2 m). 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 the approximate ,
mid-volume of the fuel. Vehicles furnished for testing at Federal
certification facilities Shall be equipped with iron-constantan Type J thermo-
couples 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 with a total
capacity of 200 to 600 cfm shall be used to mix the contents of the
enclosure during evaporative emission testing. No portion of the air
stream shall be directed towards the vehicle. 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 129.
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109 EXHAUST GAS SAMPLING SYSTEM.
(a) (1) General. The exhaust gas sampline system is designed to
measure the true mass emissions of vehicle exhaust. In the CVS concept
of measuring mass emissions, two conditions must be satisfied; the total
volume of the mixture of exhaust and dilution air must be measured, and
a continuously proportioned sample of volume must be collected for
analysis. Mass emissions are determined from the sample concentration
and totalized flow over the test period.
(2) Positive Displacement Pump. The Positive Displacement Pump-
Constant Volume Sampler (PDP-CVS), Figure 1 satisfies the first condition
by metering at a constant temperature and pressure through the pump.
The total volume is measured by counting the revolutions made by the
calibrated positive displacement pump. The proportional sample is
achieved by sampling at a constant flow rate.
(3) Critical Flow Venturi. The operation of the Critical Flow
Venturi-Constant Volume Sampler (CFV-CVS), Figure 2, is based upon the
principles of fluid dynamics associated with critical flow. Proportional
sampling throughout temperature excursions is maintained by use of a
small CFV in the sample line. The variable mixture flow rate is main-
tained at sonic velocity, which is directly proportional to the square
root of the gas temperature, and is computed continuously . Since the
pressure and temperature are the same at both venturi inlets, the sample
volume is proportional to the total volume.
(4) Diesel sampling. Diesel vehicles require a heated flame
ionization detector (HFID) for hydrocarbon analysis. The sample must be
taken as close as practical to the mixing point of the dilution air and
exhaust sample. The HFID, by design, draws its sample at a constant
flow rate. Unless compensation for varying flow is made the HFID must
be used with a constant flow system to insure a representative sample.
(5) Other systems. Other sampling systems may be used if shown to
yield equivalent results (e.g., a heat exchanger with the CFV-CVS; an
electronic flow integrator without a heat exchanger, with the PDP-CVS;
or, for diesel HC measurements, an electronic flow compensator with the
CFV-CVS).
(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:
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AMBIENT AIR
INLET
*
TO
DILUTION AIR
SAMPLE BAG
HC SPAN GAS »»-£x3—i
ZERO AIR
•FOR DIESEL HC ANALYSIS ONLY
TO
EXHAUST
SAMPLE BAG
POSITIVE DISPLACEMENT
PUMP
VEHICLE
| EXHAUST
INLET
MANOMETER
REVOLUTION
COUNTER
PICKUP
DISCHARGE
(SEE FIG. 3 FOR SYMBOL LEGEND)
FIGURE 1—EXHAUST GAS SAMPLING SYSTEM (PDP-CVS)
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VEHICLE
EXHAUST
INLET
AMBIENT AIR
INLET
SAMPLING VENTURI
TO
DILUTION AIR
SAMPLE BAG
TO
EXHAUST
SAMPLE BAG
CYCLONIC
SEPARATOR
PRECISION SENSOR
SNUBBER
ABSOLUTE PRESSURE TRANSDUCER
CVS COMPRESSOR UNIT
CVS SAMPLER UNIT
(SEE FIG. 3 FOR SYMBOL LEGEND)
FIGURE 2—EXHAUST GAS SAMPLING SYSTEM (CFV-CVS)
CRITICAL
FLOW
VENTURI
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(c) Component description, CFV-CVS. The CFV-CVS, Figure 2
consists of a dilution air filter and mixing assembly, cyclone particu-
late 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
variations measured during a dynamometer driving cycle with no connection
to the tailpipe(s). (Sampling systems capable of maintaining the
static pressure to within + 1 inch of water (0.25 kPa) will be used if
there is a need for this closer tolerance.)
(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
virtually 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 RESERVED.
Ill 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:
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X
FOR DIESEL HC ANALYSIS
SEE FIG. 1
OPEN TO ATMOSPHERE
(z)
R
FLOW CONTROL VALVE
SELECTOR VALVE
PARTICIPATE FILTER
PUMP
FLOWMETER
PRESSURE GAUGE
RECORDER
TEMPERATURE SENSOR
TO OUTSIDE VENT
FIGURE
3 EXHAUST GAS ANALYTICAL SYSTEM
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(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 122 and 144.
(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 C0? 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 122.
(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 par-
ticulate 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.
112 RESERVED.
113 FUEL SPECIFICATIONS.
(a) Gasoline.
(1) Gasoline having the following specifications shall be used
in exhaust and evaporative emission testing.
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Item ASTM Leaded Unleaded
Octane, research, minimum D2699 -100-=- -^ 96
Pb. (organic), grams/U.S. gallon 1.4 —• 0.00-0.05
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 r 0.10 0.10
Phosphorus, grams/U.S. gallon, maximum 0.01 0.005
RVP ' , psi —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 (5) (5)
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.
(2) Gasoline representative of commercial gasoline which will be
generally available through retail outlets shall be used in service
accumulation. For leaded gasoline the minimum lead content shall be
1.4 grams per U*S. gallon. The octane rating of the gasoline used shall
be no higher than 4.0 research octane numbers above the minimum recom-
mended by the vehicle manufacturer. The Reid Vapor Pressure of the
gasoline used shall be characteristic of the motor fuel used during
the season in which the service accumulation takes place.
(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
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diesel fuel may contain nonmetallic additives as follows: Centane
improver, metal deactivator, antioxidant, dehazer, antirust, pour
depressant, dye, and dispersant.
(2) Diesel fuel meeting the following specifications, or sub-
stantially 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.
Item . ASTM' Type 1-D Type 2-D
Cetane :—— D613 48-54--—r 42-52
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 (1)
Paraffins, Naphtenes, Olefins (2) (2)
Flashpoint, °F (minimum)-D93 120 130
Viscosity, Centistokes D445 1.6-2.0 2.0-3.2
Minimum
2
Remainder
(3) Diesel fuel meeting the following specifications, or substan-
tially equivalent specifications shall be used in service accumulation.
The grade of diesel fuel recommended by the engine manufacturer,
commercially designated as "Type 1-D" or "Type 2-D", shall be used.
Item ASTM Type 1-D Type 2-D
Cetane- D613 48-54 42-55
Distillation range D86
IBP, °F 330-390 340-410
10 percent point, °F 370-430 400-470
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 33-40
Total Sulfur, percent D129 or D2622-0.05-0. 20 0.2-0.5
Flashpoint, °F (minimum) D93 120 130
Viscosity, Centistokes D445 1.6-2.0 2.0-3.2
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(4) Other petroleum distillation fuel specifications:
(i) Other petroleum distillate fuels may be used for testing and
service accumulation 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.
(5) The specification range of the fuels to be used under para-
graphs (b)(2), (b)(3), and (b)(4) of this section shall be reported.
114 ANALYTICAL GASES.
(a) Analyzer gases.
(1) Gases for the CO and CO- 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
NOx, with a maximum NO- concentration of 5 percent of the nominal
value, using nitrogen as the diluent.
(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. Other FID fuels may be used
if shown to yield equivalent results.
(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 should be known to within + 2 percent of
the true values.
114A ANALYTICAL GASES
(This section under consideration for future applications)
(a) Analyzer gases.
(1) Gases for the CO and CO- analyzers shall be single blends of
CO and CO- respectively using nitrogen as the diluent.
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(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
NOx with a maximum NO- concentration of 5 percent of the nominal value
using nitrogen as the diluent.
(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. Other FID fuels may be used
if shown to yield equivalent results.
(5) The allowable zero gas (air or nitrogen) impurity concentra-
tions 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 artifical "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 other gas standards which have been approved.
(c) Span gases shall be accurate to within 2 percent of true
concentration, where true concentration refers to NBS gas standards,
or other gas standards which have been approved.
115 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 137 is
defined by upper and lower limits. The upper limit is 2 mph (3.2
km/h) higher than the highest point on the trace within 1 second of
the given time. The lower limit is 2 mph (3.2 km/h) 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 occurrences. 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 km/h).
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-C
a
a.
a-
£
FIGURE
^
is -
Is -*•
ALLOWABLE
RANGE
t
TIME
4a—DRIVERS TRACE, ALLOWABLE RANGE
a
E
ALLOWABLE
RANGE
TIME
FIGURE
4b—DRIVERS TRACE, ALLOWABLE RANGE
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(c) Figure 4 shows the range of acceptable speed tolerances for
typical points. Figure 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.
116 CALIBRATIONS, FREQUENCY AND OVERVIEW.
(a) Calibrations shall be performed as specified in sections 117
through 126.
(b) At least yearly or after any maintenance which could alter
background emission levels, enclosure background emission measurements
shall be performed.
(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 119).
(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.
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117 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 any repair which can affect the enclosure background emissions,
the enclosure shall be checked to determine that it does not contain
materials which will themselves emit hydrocarbons.
Proceed 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).
(4) Seal enclosure and measure background hydrocarbon concentration,
temperature, and barometric pressure. These are the initial readings
Cur,., T. and P . for the enclosure background determination.
HLi i iil
(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
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 checktaccording 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.
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(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).
(4) Seal enclosure and measure background hydrocarbon concentration,
temperature and barometric pressure. These are the initial readings
CTI_., T. and ?„. for the enclosure calibration.
rtCl 1 Bl
(5) Inject into the enclosure 4g (nominal value) 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 paragraph
(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, tempera-
ture and pressure according to the following equation:
-17-
-------
_ p p r p
= k V x 10 HCf Bf - HCi Bi
Where:
M^ = hydrocarbon mass change, g
C = hydrocarbon concentration as ppm carbon
HL
33 '
V = enclosure volume, ft (m ), as measured in
(b)(l) above
P = barometric pressure, in. Hg(kPa)
D
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.
118 DYNAMOMETER CALIBRATION. - .
(a) The dynamometer shall be calibrated at least once each month
or performance verified at least once each week 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 km/h).. One method for
determining dynamometer frictional power absorption at 50.0 mph (80.5
km/h) 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 inertia of the free (rear) roll may be neglected in the
case of dynamometers with paired rolls.
(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.
-18-
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(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. In addition other vehicle mass categories may be calibrated,
if desired.
(4) Drive the dynamometer up to 50.0 mph (80.5 km/h).
(5) Record indicated road power.
(6) Drive the dynamometer up to 60.0 mph (96.9 km/h).
(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 km/h) to 45 mph (72.4 km/h).
(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 km/h) versus
road load power at 50 mph (80.5 km/h) as shown in Figure 5.
(b) The performance check consists of conducting a dynamometer
coastdown at one or more inertia-horsepower settings and comparing the
coastdown time to that recorded during the last calibration. If the
coastdown 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:
= (1/2) (W/32.2) (Vx2 - V22)/550t
Where:
HP, = Power, horsepower (kilowatts)
W = Equivalent inertia, Ib (Kg)
V1 = Initial Velocity, ft/s (m/s)
(55 mph = 88.5 km/h = 80.67 ft/s = 24.58 m/s)
V. = Final Velocity, ft/s (m/s)
(45 mph = 72.4 km/h = 66 ft/s = 20.11 m/s)
-19-
-------
30.0
20.0
i
N>
O
I
? O
10.0
10.0
20.0
I
30.0 ..
40.0
ROAD LOAD HORSEPOWER AT 50 mph.
FIGURE 5—ROAD LOAD HORSEPOWER, ACTUAL VS. INDICATED
-------
t = elapsed time for rolls to coast from 55 mph
to 45 mph (88.5 to 72.4 km/h)
(Expressions in parenthesis are for SI units.). When the coastdovm is
from 55 to 45 mph (88.5 to 72.4 km/h) the above equation reduces to:
HP - 0.06073 (W/t)
for SI units, H?d = 0.09984 (W/t)
119 CVS CALIBRATION.
The CVS (Constant Volume Sampler) is calibrated using an accurate
flowmeter and restrictor valve. Measurements of various parameters are
made and related to flow through the unit. Procedures used 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 para-
graph (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 therefore reflect
the absolute pressure differentials. Secondly, temperature stability
must be maintained during the calibration. The laminar flowmeter is
-21-
-------
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. For the system indicated, the following data with
given accuracy are required:
CALIBRATION DATA MEASUREMENTS
PARAMETER
SYM
UNITS
TOLERANCES
Barometric pressure
(corrected)
Ambient temperature
Air temperature into LFE
Pressure depression
upstream of LFE
Pressure drop across the
LFE matrix
Air temperature at CVS
pump inlet
Pressure depression at
CVS pump inlet
ETI
EPI
EDP
PTI
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)
op (oc)
in. H20 (kPa)
in. H20 (kPa)
op (oc)
in. Fluid (kPa)
in. Fluid (kPa)
°F (°C)
Revs
+.01 in. Hg (+.034 kPa)
+.5°F (+.28°C)
+.25°F (+.14°C)
+.05 in. H20 (+.012 kPa)
+.005 in. H00 (+.001 kPa)
2. ~~" .
+.5°F (+.28°C)
+.05 in. Fluid (+.022 kPa)
+.05 in. Fluid (+.022 kPa)
+.5°F (+.28°C)
+ 1 Rev.
+.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.
-22-
-------
EPI
VARIABLE FLOW
RESTRICTOR
ETI
TEMPERATURE
INDICATOR
SURGE
CONTROL
VALVE
MANOMETER
FIGURE 6—PDP-CVS CALIBRATION CONFIGURATION
-------
(6) Reset the restrictor valve to a more restricted condition in
an increment of pump inlet depression (about 4" HLO (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 manu-
facturer'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.
_ (£s_ x ^£ 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 = Absolute pump inlet pressure, in. Hg (kPa)
P = P - PPI (SP.GR./13.57)
for SI units, P = P_ - PPI
P °
Where:
PR = barometric pressure, in. Hg (kPa)
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:
-24-
-------
X
o
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)
6 = P + PPO (SP. GR. /13.57)
for SI units, Pg = PR + PPO
Where:
PPO = Pressure head at pump outlet, in. fluid (kPa)
(iv) A linear least squares fit is performed to generate the
calibration equations which have the forms:
V = D - M(X )
o o o'
n = A - B(AP )
P
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:
Q8
-25-
-------
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.
(2) The manufacturer's recommended procedure shall be followed for
calibrating electronic portions of the CFV.
(3) Measurements necessary for flow calibration are as follows:
CALIBRATION DATA MEASUREMENTS
PARAMETER
SYM UNITS
TOLERANCES
Barometric
Pressure
(corrected)
"Air temper-
ature,
flowmeter
"Pressure
depression
upstream
of LFE
"Pressure drop
across LFE
matrix
"Air flow
"CFV inlet
depression
"Temperature
at venturi
inlet
"Specific
gravity of
manometer
fluid
(1.75 oil)
in. Hg (kPa)
ETI
EPI
EDP
QS
PPI
in. H20 (kPa)
in. H20 (kPa)
3 3
ft /min. (m /min,)
in. fluid (kPa)
+.01 in. Hg (+.034 kPa)
+.25°F (+.:
+.05 in. H,0 (+.012 kPa)
£, ~~~
+.005 in. H20 (+.001 kPa)
+.5%
+.05 in. fluid (+.022 kPa)
+.5"F (+.28°C)
Sp. Gr.
(4) 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.
(5) Set the variable flow restrictor to the open position, start
the blower and allow the system to stabilize. Record data from all
instruments.
-26-
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CVS DUCT
I
N>
ETI
SAMPLER DUCT
SURGE CONTROL
VALVE
VARIABLE FLOW
RESTRICTOR
MANOMETER
FIGURE
7 CFV-CVS CALIBRATION CONFIGURATION
-------
(6) Vary the flow restrictor and make at least 8 readings across
the critical flow range of the venturi.
(7) 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 manu-
facturer's prescribed method.
(ii) Calculate values of the calibration coefficient for each test
point:
K =^s
v
p
V
Where:
Q = Flow rate in standard cubic feet per minute,
S 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 = PD - 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. v
(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.
(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
-28-
-------
OPERATING
RANGE
i
l-o
Kv
INLET DEPRESSION ("H2O)
FIGURE 8—SONIC FLOW CHOKING
-------
that has been Injected into the system. (Verification can also be
accomplished by constant flow metering using critical flow orifice
devices.)
(1) Obtain a small cylinder that has been charged with pure
propane or carbon monoxide gas (caution—carbon monoxide is poisonous).
(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).
(4) The calculations of section 144 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.
120 RESERVED
121 HYDROCARBON ANALYZER CALIBRATION.
The FID hydrocarbon analyzer shall receive the following initial
and periodic calibration. The HFID shall be operated to a set point +
lp°F (+ 5.5°C) between 300 and 390°F (149 and 199°C).
(a) Initial and periodic optimization of detector response. Prior
to it;s introduction into service and at least annually thereafter the
FID hydrocarbon analyzer shall be adjusted for optimum hydrocarbon
response. Alternate methods yielding equivalent results may be used,.
(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
equal to approximately 90% of the most common operating range.
-30-
-------
(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 Che 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 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. Additional calibration points may be generated.
122 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 in-
troduction into service and annually thereafter the NDIR carbon monpxide
analyzer shall be checked for response to water vapor and CO-:
(1) Follow the manufacturer's instructions for instrument startup
and operation. Adjust the analyzer to optimize performance on the most
sensitive range.
(2) Zero the carbon monoxide analyzer with either zero grade air
or zero grade nitrogen.
(3) Bubble a mixture of 3% CO- in N_ through water at room tempera-
ture 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 conditioning 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.
-31-
-------
(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 equation which represents
the data to within 2% of each test point shall be used to determine
concentration.
123 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
N0~ to NO converter efficiency. Figure 9 is a reference for the fol-
lowing 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.
(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 N0» 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 + 02 mixture.
-32-
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FLOW CONTROL
SOLENOID VALVE
O2 OR AIR
SUPPLY
D
OZONATOR
ANALYZER
INLET
CONNECTOR
NQ/N2
SUPPLY
(SEE FIG 3 FOR SYMBOL LEGEND)
FIGURE 9—NOx CONVERTER EFFICIENCY DETECTOR
-33-
-------
(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 4- Oj 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 + a ~ H x 100
: - fi + a - bl
• • ~" I -«- * i I
L c-dJ
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:
(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 N_
calibration gases with nominal concentrations of 50 and 100% of that
range. Additional calibration points may be generated.
124 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.
-34-
-------
(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. Additional calibration points may be
generated. 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 represents the data to within 2% of
each test point shall be used to determine concentration.
125 RESERVED
126 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.
127 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 emis-
sion test.
(b) The exhaust emission test is designed to determine hydrocarbon,
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 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 representative 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
-35-
-------
(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 new motor
vehicle shall be functioning during all procedures in this Recommended
Practice.
128 TRANSMISSIONS.
(a) All test conditions shall be run with automatic and automatic
stick shift transmissions in "Drive" (highest gear); manual transmissions
shall be run in highest gear, except as noted. Automatic stick-shift
transmissions may be shifted as manual transmissions if requested 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 136 and 137.
(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 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 (24.14 km/h), 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
-36-
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at 15 mph (24.14 km/h), from second to third gear at 25 mph (40.23
km/h), and, if so equipped, from third to fourth gear at 40 mph (64.37
km/h). Fifth gear, if so equipped, may be used at the manufacturer's
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.
129 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)
Tin t-o 1 19S - - -
1 1 ?fi 1-n 1 17 ^
1 176 t-n 1 ft?**
1 fi?fi f-n 1 87 S
1 ft7fi t-o ? 17S - -
7 1 jf. t-n 7 •*T
-------
(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
km/h), 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 Hh 5 mm Hg
(+ 0.7 kPa).
(C) The road load power shall be determined according to the
procedure outlined in section 118 and adjusted according to the fol-
lowing 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 km/h). 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 118 and adjusted according to the fol-
lowing if applicable.
(3) Where it is expected that more than 33 percent of the vehicles
in an engine family will be equipped with air conditioning, the road
load power listed above or as determined in paragraph (b)(2) of this
section shall be increased by 10 percent for testing all test vehicles
representing such an engine family if those vehicles are intended to be
offered with air conditioning in production.
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130 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 (30°C). The
vehicle shall be approximately level during all phases of the test
sequence to prevent abnormal fuel distribution.
131 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.
132 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 fuel
tank(s) drain(s) and filled to the prescribed "tank fuel volume" with
the specified test fuel, section 111. For the above operations the
evaporative emission control system shall neither be abnormally purged
nor abnormally loaded.
(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 115 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 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)
-39-
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FUEL DRAIN ft FILL
I
1 HOUR MAX.
DYNO PRECONDITIONING
i
5 MIN. MAX.
COLD SOAK PARKING
I
FUELING
• DRAIN
• 40% FILL
i
DIURNAL HEAT BUILD
• HEAT FUEL-1 HOUR
• 60-84 °F
EVAP. TEST
NOT REQ
I
I
I
I
I
DIURNAL
ENCLOSURE
TEST
COLD START EXHAUST TEST
EVAP. TEST
NOT
PERFORMED
HC RUNNING
LOSSES-AS REQ
>12--36 HOURS
(no mew. for
diesels)
-1 HOUR
•10 MIN.
HOT START EXHAUST TEST
7 MIN. MAX.
HOT SOAK
ENCLOSURE
TEST
FIGURE 10 TEST SEQUENCE
-40-
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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 130 and
Figure 10.)
(c) Vehicles to be tested for evaporative emissions shall be
processed in accordance with procedures in sections 133 through 138.
Vehicles to be tested for exhaust emissions only shall be processed
according to sections 133 through 137.
133 DIURNAL BREATHING LOSS TEST.
(a)(1) Following vehicle preparation and vehicle preconditioning
procedures described in sectio 131 and section 132 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
start 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 113, to the prescribed "tank fuel volume,"
defined in the Federal Register. The temperature of the fuel prior to
its delivery to the fuel tank shall be between 50 and 60°F (10 and
16°C). The fuel tank cap(s) is not installed until the diurnal heat
build begins.
(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,
-41-
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the heat source shall be properly positioned with respect to the fuel
tank(s) and/or connected to the temperature controller.
(g) The temperature recording system shall be started.
(h) The fuel may be artifically heated to the starting diurnal
temperature.
(i) When the fuel temperature recording system reaches at least
58°F (14°C), immediately:
(1) Install fuel tank cap(s).
(2) Turn off purge blowers, if not already off at this time.
(3) Close and seal enclosure doors.
(j) When the fuel temperature recording system reaches 60 + 2°F
(16+1.1°C), immediately:
(1) Analyze enclosure atmosphere for hydrocarbons and record.
This is the initial (time = 0 minutes) hydrocarbon concentration, C ,
section 143.
(2) Start diurnal heat build and record time. This commences the
60+2 minute test period.
(k) The fuel shall be heated in such a way that its temperature
change conforms to the following function to within + 3°F (+ 1.6°C):
F = T + 0.4t
for S? units, C = T + (2/9)t
o
Where:
F = fuel temperature, °F
C = fuel temperature, °C
t = time since beginning of test, minutes.
T = initial temperature
After 60+2 minutes of heating, the fuel temperature rise shall be 24 +
1°F (+ 0.5°C).
(1) The FID hydrocarbon analyzer shall be zeroed and spanned
immediately prior to the end of the diurnal test.
(m) The end of the diurnal breathing loss test occurs 60+2
minutes after the heat build begins, paragraph (J)(2). Analyze the
enclosure atmosphere for hydrocarbons and record. This is the final
(time = 60 minutes) hydrocarbon concentration, HCf, section 143. The
time (or elapsed time) of this analysis shall recorded.
-42-
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(n) The heat source shall be turned off and the enclosure doors
unsealed and opened.
(o) 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.
(p) For vehicles with multiple tanks, the largest tank shall be
designated as the primary tank and shall be heated in accordance with
the procedures described in paragraph (k) of this section. All other
tanks shall be designated as auxiliary tanks and shall undergo a similar
heat build such that the fuel temperature shall be within 3°F (1.6°C) of
the primary tank.
134 RUNNING LOSS TEST.
(a) If an engineering analysis or vehicle inspection indicates the
possibility of evaporative emissions during vehicle operation, evapora-
tive 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 135 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 sections 135
through 137.
(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.
135 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 132 and section 133 and a "hot" start test fol-
-43-
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lowing the "cold" start test 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 hydro-
carbons (except diesel hydrocarbons which are analyzed continuously),
carbon monoxide, carbon dioxide, and oxides of nitrogen. A parallel
sample of the dilution air is similarly analyzed for hydrocarbon, carbon
monoxide, carbon dioxide, 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 approp-
riate 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 case of vehicles
with rear engine compartments (or if special designs make the above
impractical), the cooling fan shall be placed in a position to provide
sufficient air to maintain vehicle cooling. The fan capacity shall
normally not exceed 5,300 cfm (2.50 m /s). If, however, the manu—
facturer 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 at test points, provided an emission sample is not taken, for
the purpose of finding the minimum throttle action to maintain the
proper speed-time relationship, or to permit sampling system adjust-
ments.
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 a gauge pressure
of 45 psi (310 kPa) 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 mph (48 km/h) using a non-test vehicle or as
recommended by the dynamometer manufacturer.
-44-
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(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. Dynamo-
meters using automatic control of preselectable power settings may be
set anytime prior to the beginning of the emissions test.
136 ENGINE STARTING AND RESTARTING.
Ca) 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.
C2) Choke operation:
(i) Vehicles equipped with automatic chokes shall be operated
according to 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.
(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 20-
second-idle period shall begin when the engine starts. 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.
(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 137, 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 tailpipe during the
diagnostic period.
-45-
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(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. The
reason for the malfunction Cif determined) and the corrective action
taken shall be reported.
Cd) 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.
(2) If the engine stalls during some 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 128.
(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. The reason for the
malfunction (if determined) and the corrective action taken shall be
reported.
137 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
-46-
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"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 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.
-47-
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(10) Operate the vehicle according to the dynamometer driving
schedule (section 115).
(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 140.
(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 140.
(14) Immediately after the end of the sample period turn off the
cooling fan and close the engine compartment cover.
(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(si and
drive vehicle from dynamometer.
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(20) The constant volume sampler may be turned off, if desired.
(21) Vehicles to be tested for evaporative emissions will proceed
according to section 138. For all others this completes the test sequence.
138 HOT SOAK TEST.
The hot soak evaporative emission test shall be conducted immedi-
ately 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 the vehicle entrance of the enclosure.
(e) The vehicle's engine must be stopped before any part of the
vehicle enters the enclosure. The vehicle may be pushed or coasted into
the enclosure.
(f) The test vehicle windows and luggage compartments shall be
opened, if not already open.
(g) The temperature recording system shall be started and the time
of engine shut off shall be noted on the evaporative emission hydrocarbon
data recording system.
(h) The enclosure doors shall be closed and sealed within two
minutes of engine shutdown and within seven 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 143.
(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.
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(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 rp, for use in calculating evapora-
tive losses, see section 143. This operation completes the evaporative
emission measurement procedure.
139 RESERVED
140 EXHAUST SAMPLE ANALYSIS.
The following sequence of operations shall be performed in con-
junction 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
75 to 100 percent of full scale. If gain has shifted significantly on
the analyzers, check the calibrations. Show actual concentrations 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.
(f) For diesel vehicles, continuously record (integrate electronically
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).
141 RESERVED
142 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.
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(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 km/h) and drive
wheel tire-pressure, as applicable.
(g) Indicated road load power absorption at 50 mph (80 km/h) and
dynamometer serial number. As an alternative to recording the dynamo-
meter 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 calibra-
tion 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.
(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 continuously
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 122 and
section 144) 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.
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(o) Temperature set point of the heated sample line and heated
hydrocarbon detector temperature control system (for diesel vehicles
only).
143 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:
"HC
= k V x 10
n
-4
CHCf PBf ~ CHCi PBi
T T
f i
Where:
M.,r = hydrocarbon mass, g.
C = hydrocarbon concentration as ppm carbon.
HC
3 3
V = net enclosure volume, ft Im ) as determined by
subtracting 50 ft (1.42 m ) (volume of vehicle
with trunk and windows open) from the enclosure
volume. A manufacturer may use the measured-volume
of the vehicle (instead of the nominal 50 ft ),
provided the measured volume is determined and used
for all vehicles tested by that manufacturer.
?„ = barometric pressure, in. Hg (kPa).
D
T = enclosure ambient temperature, R (K).
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.
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144 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 = CO.43 Y ^ + 0.57 Y- + Y )/7.5
win ct ht 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"
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 JHC cone
(2) Oxides of nitrogen mass:
NOx = V . X Density .„ X K_, X (NOx /1,000,000)
mass mix J N0_ H cone '
(3) Carbon monoxide mass:
CO = V . X Density.. X (CO /I,000,000)
mass mix 'CO cone
(4) Carbon dioxide mass:
C00 = V . X Densitynri X (C00 /100)
2mass mix CO- 2conc
(c) Meaning of symbols:
(1) ^mass ^ Hydrocarbon emissions, in grams per test
phase.
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Density = 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-
cone
haust sample corrected for background, in ppm carbon
equivalent, i.e., equivalent propane X 3.
HC = HC - HC, (1-1/DF)
cone e d
Where:
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) NOx = 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
cone
dilute exhaust sample corrected for background, in ppm.
NOx = NOx - NOx, (1-1/DF)
cone e d
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.
o
Density = Density of carbon monoxide is 32.97 g/ft
(1.164 feg/m it at 68°F C20°C) and 760 mm Hg (101.3
kPa) pressure.
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Where:
Where:
CO = Carbon monoxide concentration of the dilute
ROTlf*
aust sample corrected for background, water vapor,
and C0» extraction, in ppm.
CO = CO - CO, (1-1/DF)
cone e d
CO = Carbon monoxide concentration of the dilute
exhaust 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 C00 '- 0.000323 R) CO
e 2e 'em
CO = Carbon monoxide concentration of the dilute
exnaust 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 142(n)).
CO
Carbon monoxide concentration of the dilution
air corrected for water vapor extraction, in ppm.
CO ,= (1-0.000323 R) CO,
d dm
Where:
CO, = Carbon monoxide concentration of the dilution
air sample as measured, in ppm.
NOTE: If a CO instrument which meets the criteria specified in
section 111 is used and the conditioning column has been deleted, CO
can be substituted directly for CO and CO, can be substituted direc?ly
for CO,.
d
dm
(4) C09 = Carbon dioxide emissions, in grams per test
_ ^nicis s
phase.
3
DensityCO- = Density of carbon dioxide is 51.85 g/ft
(1.843 kgfm ), at 68°F (2Q°C) and 760 mm Hg (101.3
kPa) pressure.
C0_ = Carbon dioxide concentration of the dilute
^COTIC
exnaust sample corrected for background, in percent.
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(5) DF = .13.47[CO2 + (HCe + C0g) 10~4]
KU i= Humidity correction factor.
Kg = I/I1-0.0047 (H-75)]
for SI units = I/[1-0.0329 (H-10.711J
Where:
H = Absolute humidity in grains (grams) of water
per pound (kilogram) of dry air.
H = [(43.478) R X ?,]/[?„ - (P, X R /100)]
a a is da
for SI units, H = [(6.211) R X ?,]/[?„ - (P. X R /100)]
cl u ii Q Si
R = Relative humidity of the ambient air, in percent.
cl
P, = Saturated vapor pressure, in mm Hg (kPa) at
the ambient dry bulb temperature.
P_ = Barometric pressure, in mm Hg (kPa).
a
V . = Total dilute exhaust volume in cubic feet per
test phase corrected to standard conditions (528 R
(293 K) and 760 mm Hg (101.3 kPa)).
For PDP-CVS, V , is:
mix
Vmix = V x N(P -P.)(528 R)
o a H
(760 mm Hg) (T )
for SI units, V . = V x N(PD - P.) (293.15 K)
mix o B 4
Where:
(101.325 kPa) (T )
P
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.
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P = Barometric pressure, in mm Hg (kPa).
a
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, R0Q •
(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%;
P =762 mm Hg;° P =22.225 mm Hg; P,=70 mm Hg; T =570 R; HC =105.8 ppm,
carbon equivalent; NOx =11.2 ppm; CO =306.6 ppm; C02 =1.45%; HC,=12.1
ppm; NOx =0.8 ppm; CO® =15.3 ppm. em e
Then:
V = (0.29344) (10,485) (762-70) (528)/(760)C570)=
2595.0 ft per test phase.
H = (43.478) (48.2) (22.225)/[762-C22.225 x 48.2/100)]
= 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~A] = 9.116
HC = 105.8-12.1(1-1/9.116) = 95.03 ppm
cone r
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
IHclSS .
grams per test phase.
CO = 293.4-15.1 (1-1/9.116) = 280.0 ppm
cone *v
CO = (2595) (32.97) (280/1,000,000) « 23.96 grams per
mass • ' or
test phase.
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(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 * / v
NOx =1.27 grams per test phase
mass & r v
CO =5.98 grams per test phase . .
mass .
(3) For the "transient" portion of the hot start test assume that
similar calculations resulted in the following;
i
HC = 0.51 grams per test phase
mass . • ,
NOx = 1.38 grams per test phase
mass 6 v . v
CO =5.01 grams per test phase
mass e> r r
(4) Weighted mass emission results:
HC = [(0.43) (4.027) + (0.57)(0.51) + 0.62]/7.5 = 0.352
wm , . . ,
grams per vehicle mile.
NOx = [(0.43) (1.389) + (0.57) (1.38) + 1.27J/7.5 = 0.354
wm , . , . ,
grams per vehicle mile.
C°wm = [(0'43) <23-96) + (0-57) (5.01) + 5.98J/7.5 =2.55
grams per vehicle mile.
145 RESERVED
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