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amount of NO, increases with time, the total NOx (NO+NO2) remains constant. A decay of NOx with time indicates the converter is not essentially 100 percent efficient and the cause should be determined before the instrument is used.

(iii) The converter efficiency should be checked at least once weekly and preferably once daily.

(b) HC, CO, CO2, and NOx measurements: Allow a minimum of 20 minutes warmup for the HC analyzer and 2 hours for the CO, CO2 and NO, analyzers. (Power is normally left on infrared and chemiluminescence analyzers; but when not in use, the chopper motors of the infrared analyzers are turned off and the phototube high voltage supply of the chemiluminescence analyzer is placed in the standby position.) The following sequence of operations should be performed in conjunction with each series of measurements:

(1) Zero the analyzers. Obtain a stable zero on each amplifier meter and recorder. Recheck after tests.

(2) Introduce span gases and set the CO and CO2 analyzer gains, the HC analyzer sample capillary flow rate and the NO, analyzer high voltage supply to match the calibration curves. In order to avoid corrections, span and calibrate at the same flow rates used to analyze the test samples. Span gases should have concentrations equal to approximately 80 percent of full scale. If gain has shifted significantly on the CO or CO, analyzers, check tuning. If necessary, check calibration. Recheck after test. Show actual concentrations on chart.

(3) Check zeros; repeat the procedure in subparagraphs (1) and (2) of this paragraph if required.

(4) Check flow rates and pressures.

(5) Measure HC, CO, CO2, and NOX concentrations of samples. Care should be exercised to prevent moisture from condensing in the sample collection bag.

(6) Check zero and span points.

(c) For the purposes of this section, the term “zero grade air” includes artificial “air” consisting of a blend of nitrogen and oxygen with oxygen concentrations between 18 and 21 mole percent. 8 85.85 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 before the cold start exhaust emission test, at an ambient temperature as specified in

$$ 85.73 and 85.74. The vehicle shall be stored prior to the emission tests 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 and simulates a hot start drive of 7.5 miles. The vehicle is allowed to stand on the dynamometer during the 10-minute time period between the cold and hot start tests. The cold start test is divided into two periods. The first period, representing the cold start “transient” phase, terminates at the end of the deceleration which is scheduled to occur at 505 seconds of the driving schedule. The second period, representing the “stabilized”. phase, consists of the remainder of the driving schedule including engine shutdown. The hot start test similarly consists of two periods. The first period, representing the hot start “transient” phase, terminates at the same point in the driving schedule as the first phase 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. During the tests the ambient temperature shall be between 68° F. and 86°F.

(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 start the cooling fan.

(3) With the sample solenoid valves in the “dump" position connect evacuated sample collection bags to the two dilute exhaust sample connectors and the dilution air sample line connector.

(4) Start the positive displacement pump, the sample pumps and the temperature recorder. (The heat exchanger of the constant volume sampler should be preheated to its operating temperature before the test begins.)

(5) Adjust the sample flow rates to the desired flow rate (minimum of 10 c.f.h.) and set the revolution counters to zero.

(6) Attach the flexible exhaust tube to the vehicle tailpipe(s).

(7) Simultaneously start the revolution counter for the positive displacement pump, position the sample solenoid valves to direct the sample flows into the “transient” exhaust sample bag and the

dilution air sample bag, and start crank, ing the engine.

(8) Fifteen seconds after the engine starts, place the transmission in gear.

(9) Twenty seconds after the engine starts, begin the initial vehicle acceleration of the driving schedule.

(10) Operate the vehicle according to the dynamometer driving schedule ($ 85.75).

(11) At the end of the deceleration which is scheduled to occur at 505 seconds, simultaneously switch the dilute exhaust sample flow from the “transient” bag to the "stabilized” bag, switch off revolution counter No. 1 and start counter No. 2. Immediately disconnect the “transient” sample bag, transfer to the analytical system and process according to 85.84 as soon as practical and in no case longer than 10 minutes after the end of this portion of the test.

(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 revolution counter No. 2 and position the sample solenoid valve to the “dump" position. Immediately disconnect the "stabilized” exhaust and dilution air sample bags, transfer to analytical system and process samples according to § 85.84 as soon as practicable and in no case longer than 10 minutes after the end of this portion of the dynamometer test.

(14) Immediately after the end of the sample period, disconnect the exhaust tube from the tailpipe(s), turn off the cooling fan and close the engine compartment cover.

(15) Turn off the positive displacement pump.

(16) Repeat the steps in subparagraphs (2) through (10) of this paragraph for the hot start test except only one evacuated sample bag is required for sampling exhaust gas. The step in subparagraph (7) of this paragraph shall begin 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 the No. 1 revolution counter and position the sample solenoid valve to the “dump” position. (Engine shutdown is not part of the hot start test sample period.)

(18) Immediately disconnect the "transient” exhaust and dilution air

sample bags, transfer to analytical system and process samples according to § 85.84 as soon as practicable and in no case longer than 10 minutes after the end of this portion of the dynamometer test.

(19) Disconnect the exhaust tube from the vehicle tailpipe(s) and remove vehicle from dynamometer.

(20) Turn off the positive displacement pump. $ 85.86 Chart reading.

(a) Determine the HC, CO, CO, and NOx concentrations of the dilution air and dilute exhaust sample bags from the instrument deflections or recordings making use of appropriate calibration charts.

(b) Determine the average dilute exhaust mixture temperatures from the temperature recorder trace if a recorder is used. § 85.87 Calculations (exhaust emis

sions). The final reported test results shall be computed by use of the following formulae: (a) For light duty vehicles:

Ywm= (0.43 Yet +0.57 Ynt+Ys)/7.5 where: Ywm=Weighted mass emissions of each

pollutant, i.e. HC, CO, or NOs, in

grams per vehicle mile. Yct=Mass emissions as calculated from

the “transient" phase of the cold

start test, in grams per test phase. Yht=Mass emissions as calculated from

the “transient" phase of the hot

start test, in grams per test phase. Ys=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:

HCconc
HCmass=Vmix X Densityhc X-

1,000,000
(2) Oxides of nitrogen Mass:

NOsconc

NOxmass =VmixX Densityno, X – ХКн

1,000,000 (3) Carbon monoxide Mass:

COconc
COmass=VmixX Densityco X-

1,000,000

(c) Meaning of symbols:
HCmass=Hydrocarbon emissions, in

grams per test phase. Densityhc=Density of hydrocarbons in the

exhaust gas, assuming an average carbon to hydrogen ratio of 1:1.85, in grams per cubic foot at 68° F. and 760 mm. Hg pressure (16.33 gm./

cu. ft.).
HCconc=Hydrocarbon concentration of

the dilute exhaust sample
corrected for background, in
p.p.m. carbon equivalent, i.e.

equivalent propane X 3. HCconc=HC.-HCd (1-1/DF) where: HCe=Hydrocarbon concentration of

the dilute exhaust sample as measured, in p.p.m. carbon

equivalent. HCa=Hydrocarbon concentration of

the dilution air as measured,

in p.p.m. carbon equivalent. NOsmass=Oxides of nitrogen emissions,

in grams per test phase. Densityno, =Density of oxides of nitrogen

in the exhaust gas, assuming they are in the form of nitrogen dioxide, in grams per cubic foot at 68° F. and 760 mm. Hg pressure (54.16 gm./

cu. ft.). NOI cong = Oxides of nitrogen concentra

tion of the dilute exhaust sample corrected for back

ground, in p.p.m. NOxconc=NOxe-NOxa (1-1/DP) where: NOx=Oxides of nitrogen concentra

tion of the dilute exhaust

sample as measured, in p.p.m. NOxa=Oxides of nitrogen concentra

tion of the dilution air as

measured, in p.p.m. COmass=Carbon monoxide emissions, in

grams per test phase. Densityco=Density of carbon monoxide in

grams per cubic foot at 68° F. and 760 mm. Hg pressure

(32.97 gm./cu. ft.). COconc=Carbon monoxide concentra

tion of the dilute exhaust sample corrected for background, water vapor and CO2

extraction, in p.p.m. CO conc=Co.-Cod (1-1/DF) where: CO.=Carbon monoxide concentration of

the dilute exhaust sample volume
corrected for water vapor and
carbon dioxide extraction, in p.p.m.
The calculation assumes the hy-
drogen=carbon ratio of the fuel is

1.85:1.
CO-=(1-0.01925 CO2,-0.000323 R) CO.

where: CO.m=Carbon monoxide concentration of

the dilute exhaust sample as

measured, in p.p.m. CO2. =Carbon dioxide concentration of

the dilute exhaust sample, in

mole percent. R=Relative humidity of the dilution

air, in percent. CO=Carbon monoxide concentration of

the dilution air corrected for

water vapor extraction, in p.p.m. Coa=(1-0.000323 R) COM where: CO.=Carbon monoxide concentration of

the dilution air sample as measured, in p.p.m.

13.4
DF-

CO2 + (HC. +COe) X 10-4
Vmax=Total dilute exhaust volume in

cubic feet per test phase corrected
to standard conditions (528°R

and 760 mm. Hg). Vmix=V.XN (Pp/760 mm. Hg) (528°R/Tp) where: Vo=Volume of gas pumped by the posi

tive displacement pump, in cubic cubic feet per revolution. This volume is dependent on the pressure differential across the positive dis

placement pump. N=Number of revolutions of the positive

displacement pump during the test phase while samples are being

collected. Pp=Absolute pressure of the dilute ex

haust entering the positive displacement pump, in mm. HG, i.e. barometric pressure minus the pressure depression below atmospheric of the mixture entering the positive dis

placement pump. Tp=Average temperature of dilute exhaust

entering positive displacement
pump during test while samples
are being collected, in degrees

Rankine.
Ku=Humidity correction factor.

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KE=

-=0.9424
1-0.0047 (62—75)
CO.=(1-0.01925(1.43) -0.000323 (48))

306.6=293.4 p.p.m.
COa=(1-0.000323 (48)) 15.3=15.1 p.p.m.

13.4 DF=

1.43+ (105.8+293.4) X 10+ HCconc=105.8—12.1 (1–1/9.116) =95.03 HCmass=(2595) (16.33) (95.03/1,000,000) =

4.027 grams per test phase. NOscone=11.2-0.8 (1-1/9.116)=10.49 NOxmass=(2595) (54.16) (10.49/1,000,000)

(0.9424) =1.389 grams per test phase. COconc=293.4–15.3 (1-1/9.116) =279.8 COmass=(2595) (32.97) (279.8/1,000,000) =

23.94 grams per test phase. (2) For the “stabilized” portion of the cold start test assume that similar calculations resulted in HCmass=0.62 grams per test phase; NOsmass = 1.27 grams per test phase; and COmass=5.98 grams per test phase.

(3) For the “transient” portion of the hot start test assume that similar calculations resulted in HCmess=0.51 grams per test phase; NOxmass=1.38 grams per test phase; and COmass=5.01 grams per test phase.

(4) For a 1975 light duty vehicle: HCwm=((0.43) (4.027) +(0.57) (0.51) +0.62) /

7.5=0.352 gram per vehicle mile. NOsm=((0.43) (1.389) + (0.57) (1.38) +

1.27)/7.5=0.354 gram per vehicle mile. COwm= ((0.43) (23.94) + (0.57) (5.01) +

5.98)/7.5=2.55 grams per vehicle mile. $ 85.88 Calculations (fuel evaporative

emissions). The net weights of the individual collection traps employed in $ 85.74 shall be added together to determine compliance with the fuel evaporative emission standard. & 85.89 Test vehicles.

(a) (1) The vehicles covered by the application for certification will be di vided into groupings of vehicles whose engines are expected to have similar

emission characteristics. Each group of engines with similar emission characteristics shall be defined as a separate engine family.

(2) To be classed in the same engine family, engines must be identical in all the following respects:

(i) The cylinder bore center to center dimensions.

(ii) The dimension from the centerline of the crankshaft to the centerline of the camshaft.

(iii) The dimension from the centerline of the crankshaft to the top of the cylinder block head face.

(iv) The cylinder block configuration (air-cooled or water-cooled; L-6, 90° V-8, etc.).

(v) The location of intake and exhaust valves and the valve sizes (within a 18inch range on the valve head diameter).

(vi) The method of air aspiration.
(vii) The combustion cycle.

(3) Engines identical in all the respects listed in subparagraph (2) of this paragraph may be further divided into different engine families if the Administrator determines that they may be expected to have different emission characteristics. This determination will be based upon a consideration of the following features of each engine:

(i) The bore and stroke.

(ii) The surface to volume ratio of the nominally dimensioned cylinder at the top dead center position.

(iii) The intake manifold induction port size and configuration.

(iv) The exhaust manifold port size and configuration.

(v) The intake and exhaust valve sizes.

(vi) The fuel system.

(vii) The camshaft timing and ignition timing characteristics.

(4) Where engines are of a type which cannot be divided into engine families based upon the criteria listed in subparagraphs (2) and (3) of this paragraph, the Administrator will establish families for those engines based upon the features most related to their emission characteristics.

(b) Emission data vehicles:

(1) Vehicles will be chosen to be operated and tested for emission data based upon the engine family groupings. Within each engine family, the requiremerits of this paragraph must be met.

(2) Vehicles of each engine family will be divided into engine displacement

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exhaust emission control system- engine family, an additional vehicle usevaporative emission control system com ing that combination in that family will binations. A projected sales volume will be selected so that the durability data be established for each combination for fleet shall contain at least two vehicles the model year for which certification is with each combination. The additional sought. One vehicle of each combination vehicle will be selected in the same manwill be selected in order of decreasing ner as vehicles selected under subprojected sales volume until 70 percent paragraph (1) of this paragraph. of the projected sales of a manu (3) A manufacturer may elect to opfacturer's total production of vehicles of erate and test additional vehicles to that engine family is represented, or represent any engine-system combinauntil a maximum of four vehicles is tion. The additional vehicles must be of selected. If any single combination rep the same engine displacement, transmisresents over 70 percent, then two vehicles sion type, fuel system and inertia weight of that combination will be selected. The class as the vehicle selected for that vehicle selected for each combination engine-system combination in accordwill be specified by the Administrator as ance with the provisions of subparagraph to transmission type, fuel system and in (1) of this paragraph. Notice of an inertia weight class.

tent to operate and test additional ve(3) The Administrator may select a hicles shall be given to the Administrator maximum of four additional vehicles not later than 30 days following notificawithin each engine family based upon tion of the test fleet selection. features indicating that they may have (d) For purposes of testing under the highest emission levels of the ve $ 85.91(g), the Administrator may rehicles in that engine family. In selecting quire additional emission data vehicles these vehicles, the Administrator will and durability data vehicles identical in consider such features as the emission all material respects to vehicles selected control system combination, induction in accordance with paragraphs (b) and system characteristics, ignition system (c) of this section: Provided, That the characteristics, fuel system, rated horse number of vehicles selected shall not inpower, rated torque, compression ratio, crease the size of either the emission data inertia weight class, transmission op fleet or the durability data fleet by more tions and axle ratios.

than 20 percent or one vehicle, which(4) If the vehicles selected in accord ever is greater. ance with subparagraphs (2) and (3) of (e) Any manufacturer whose projected this paragraph do not represent each sales of new motor vehicles subject to engine-system combination, then one this subpart for the model year for vehicle of each engine-system combina which certification is sought is less than tion not represented will be selected by 2,000 vehicles may request a reduction the Administrator. The vehicle selected in the number of test vehicles determined shall be of the engine displacement with in accordance with the foregoing provithe largest projected sales volume of ve sions of this section. The Administrator hicles with the control system combina may agree to such lesser number as he tion in the engine family and will be determines would meet the objectives of designated by the Administrator as to this procedure. transmission type, fuel system and inertia (f) In lieu of testing an emission data weight class.

or durability data vehicle selected under (c) Durability data vehicles:

paragraph (b) or (c) of this section, and (1) A durability data vehicle will be submitting data therefor, a manufacturer selected by the Administrator to repre may, with the prior written approval of sent each engine-system combination.

the Administrator, submit data on a The vehicle selected shall be of the en

similar vehicle for which certification gine displacement with the largest pro

has previously been obtained. jected sales volume of vehicles with that

(g) (1) Where it is expected that

more than 33 percent of an engine famcontrol system combination in that en

ily will be equipped with an optional gine family and will be designated by the

item, the full estimated weight of that Administrator as to transmission type,

item shall be included in the curb weight fuel system and inertia weight class.

computation for the entire engine fam(2) If an exhaust emission control ily. Where it is expected that 33 percent system-fuel evaporative emission control or less of the vehicles in an engine family system combination is used in only one will be equipped with an item of op

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