amount of NO increases with time, the total NOx (NO+NO) 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 NO、 measurements: Allow a minimum of 20 minutes warmup for the HC analyzer and 2 hours for the CO, CO2 and NOx 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 NOx 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 CO2 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. § 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 cranking the engine.

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

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

(10) Operate the vehicle according to the dynamometer driving schedule

(§ 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, CO2 and NO 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

sions).

(exhaust emis

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 Yht+Ys)/7.5

where:

Ywm wm

Weighted mass emissions of each pollutant, i.e. HC, CO, or NOx, in grams per vehicle mile.

Yet 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:

NOx,

e

Oxides of nitrogen concentration of the dilute exhaust sample as measured, in p.p.m. NOxd =Oxides of nitrogen concentration 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.).

COcone Carbon monoxide concentration of the dilute exhaust sample corrected for background, water vapor and CO2 extraction, in p.p.m.

CO conc=CO-COɑ (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 hydrogen carbon ratio of the fuel is

1.85:1.

CO. (1-0.01925 CO2, -0.000323 R) Com

CO2 + (HC.+COe) X 10+

Vmix Total dilute exhaust volume in cubic feet per test phase corrected to standard conditions (528°R and 760 mm. Hg).

Vmix VoXN (Pp/760 mm. Hg) (528°R/Tp) where:

V. Volume of gas pumped by the positive displacement pump, in cubic cubic feet 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 being collected.

are

=

NOx conc=11.2-0.8 (1-1/9.116)=10.49 NO mass (2595) (54.16) (10.49/1,000,000) (0.9424)=1.389 grams per test phase. CO conc=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; NO mass-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 HCmass-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. NOxwm=((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. Calculations (fuel evaporative

§ 85.88

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 divided into groupings of vehicles whose engines are expected to have similar

66-088-72-17

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 inch 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 requirements of this paragraph must be met.

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

exhaust emission control systemevaporative emission control system combinations. A projected sales volume will be established for each combination for the model year for which certification is sought. One vehicle of each combination will be selected in order of decreasing projected sales volume until 70 percent of the projected sales of a manufacturer's total production of vehicles of that engine family is represented, or until a maximum of four vehicles is selected. If any single combination represents over 70 percent, then two vehicles of that combination will be selected. The vehicle selected for each combination will be specified by the Administrator as to transmission type, fuel system and inertia weight class.

(3) The Administrator may select a maximum of four additional vehicles within each engine family based upon features indicating that they may have the highest emission levels of the vehicles in that engine family. In selecting these vehicles, the Administrator will consider such features as the emission control system combination, induction system characteristics, ignition system characteristics, fuel system, rated horsepower, rated torque, compression ratio, inertia weight class, transmission options and axle ratios.

(4) If the vehicles selected in accordance with subparagraphs (2) and (3) of this paragraph do not represent each engine-system combination, then one vehicle of each engine-system combination not represented will be selected by the Administrator. The vehicle selected shall be of the engine displacement with the largest projected sales volume of vehicles with the control system combination in the engine family and will be designated by the Administrator as to transmission type, fuel system and inertia weight class.

(c) Durability data vehicles:

(1) A durability data vehicle will be selected by the Administrator to represent each engine-system combination. The vehicle selected shall be of the engine displacement with the largest projected sales volume of vehicles with that control system combination in that engine family and will be designated by the Administrator as to transmission type, fuel system and inertia weight class.

(2) If an exhaust emission control system-fuel evaporative emission control system combination is used in only one

engine family, an additional vehicle using that combination in that family will be selected so that the durability data fleet shall contain at least two vehicles with each combination. The additional vehicle will be selected in the same manner as vehicles selected under subparagraph (1) of this paragraph.

(3) A manufacturer may elect to operate and test additional vehicles to represent any engine-system combination. The additional vehicles must be of the same engine displacement, transmission type, fuel system and inertia weight class as the vehicle selected for that engine-system combination in accordance with the provisions of subparagraph (1) of this paragraph. Notice of an intent to operate and test additional vehicles shall be given to the Administrator not later than 30 days following notification of the test fleet selection.

(d) For purposes of testing under § 85.91(g), the Administrator may require additional emission data vehicles and durability data vehicles identical in all material respects to vehicles selected in accordance with paragraphs (b) and (c) of this section: Provided, That the number of vehicles selected shall not increase the size of either the emission data fleet or the durability data fleet by more than 20 percent or one vehicle, whichever is greater.

(e) Any manufacturer whose projected sales of new motor vehicles subject to this subpart for the model year for which certification is sought is less than 2,000 vehicles may request a reduction in the number of test vehicles determined in accordance with the foregoing provisions of this section. The Administrator may agree to such lesser number as he determines would meet the objectives of this procedure.

(f) In lieu of testing an emission data or durability data vehicle selected under paragraph (b) or (c) of this section, and submitting data therefor, a manufacturer may, with the prior written approval of the Administrator, submit data on a similar vehicle for which certification has previously been obtained.

(g) (1) Where it is expected that more than 33 percent of an engine family will be equipped with an optional item, the full estimated weight of that item shall be included in the curb weight computation for the entire engine family. Where it is expected that 33 percent or less of the vehicles in an engine family will be equipped with an item of op