(g) Analyzer Tuning-Gain-Detector number.

(h) Identify zero traces, steadystate traces, calibration traces, and start and finish of each test.

(i) Record sample cell pressure. (j) Ambient temperature (i.e. air in front of radiator).

§ 85.80 Calibration and instrument checks.

(a) Calibrate following assembly, and repeat every 30 days thereafter. Use the same flow rate as when sampling exhaust. Adjust to the same pressure setting on the manometer as observed during sampling. Proceed as follows: (1) Clean cells and tune analyzers. (2) Zero on nitrogen. Check each cylinder of N2 for contamination with hydrocarbons. Set the instrument gain to give the desired range. Normal operating ranges are as follows:

Low Range Hydro- 0-1,750 ppm hexane. carbon Analyzer.

High Range Hydro- 0-10,000 ppm. hexcarbon Analyzer. CO Analyzer.

CO2

Analyzer --

ane. 0-12% CO. 0-16% CO2.

Minimum use temperature of the cylinders should be 70° F.

(4) Compare values with previous curves. Any significant change reflects some problem in the system. Locate and correct problem, and recalibrate. Use best judgment in selecting curve for data reduction.

(5) Check response of hydrocarbon analyzer to 100% CO2. If response is greater than 0.5% full scale, refill filter cells with 100% CO2 and recheck. Note any remaining response on chart. If response still exceeds 0.5%, replace detector.

(6) Check response of hydrocarbon analyzers to air saturated with water at ambient temperature. Record ambient temperature. If the low range instrument response exceeds 5% of full scale with saturated air at 75° F., replace the detector. If the high range response exceeds 0.5% of full scale, check detector on low range instrument, then reject if response exceeds 5% of full scale at 75° F.

(b) Daily instrument check: Allow a minimum of 2 hours warmup for infrared analyzers. (Power is normally left on continuously; but, when instruments are not in use, chopper motor is turned off.) The following should be done before each series of tests:

(1) Zero on clean nitrogen introduced at analyzer inlet. Obtain a stable zero on the amplifier meter and recorder. Recheck after test.

(2) Introduce normalizing gas and set gain to match calibration curve. In order to avoid a correction for sample cell pressure, normalize and calibrate at the same cell pressure determined in § 85.78 (e) (4). Normalizing or span gases: See § 85.80 (a) (3) for allowable variation. Low Range Hydrocarbon Analyzer.

1,500-1,700 ppm hex

ane

or

propane equivalent for the instrument.

5,000 ppm hexane or propane equivalent for the instrument. 10% CO in N.. 12 to 16% CO2 in N

(a) The car and device are allowed to stand long enough to reach ambient temperature (at least 12 hours). The vehicle is to be stored prior to the test in such a manner that precipitation (e.g., rain or dew) does not occur on the vehicle and the minimum ambient temperature in the vicinity of the engine during the soak period is 60° F. During the run the ambient temperature should be between 68° and 86° F.

(b) The following steps shall then be taken for each test. (Special procedures may be required for certain cars: for example, those equipped with dual exhaust systems. These problems must be handled on an individual basis, and a procedure agreed to by the Surgeon General established.)

(1) Place car on dynamometer without starting engine.

(2) Clean condensate

change filter thimbles.

traps and

(3) Purge entire sampling system by allowing air to enter at probe.

(4) Purge the instruments with nitrogen. Turn on chart drive and adjust the zero. Check span.

(5) Stop the nitrogen purge and switch the analyzers to the exhaust sampling train. Adjust each flow rate. Note and record the sample system pressures on chart.

(6) Insert the sampling line at least 2 feet into the tailpipe. If this is not possible, a tailpipe extension should be used. Break connection to train.

(7) With car hood up, start the cooling fan.

(8) Start the car. After the engine has run 20 seconds, connect sample line to train.

(9) Run 7 seven-mode cycles.

(10) Change glass wool in coarse filter during idle following cycle 2.

(11) Record manifold vacuum during 50 m.p.h. cruise.

(12) Record on the dynamometer data sheet the engine idle r.p.m.: In drive range for automatics, in neutral for manuals.

(13) Remove probe from exhaust and determine air response (hangup). As a guide, the hydrocarbon concentration should drop to 5% of scale in 10 seconds and 2-4% of scale in 2-3 minutes. If it does not, the test is questionable.

(14) Record nitrogen zero, and check span. If zero and span drift is in excess of 3% of the span concentration during the run, the results are questionable. § 85.82 Chart reading.

The recorder response for measuring exhaust gas concentrations will always lag the engine's operation because of a variable exhaust system delay and a fixed sample system delay. Therefore, the concentrations for each mode will not be located on the charts at a point corresponding to the exact time of the mode. For each warmup cycle to be evaluated, proceed as follows:

(a) Determine whether the cycle was driven in accordance with the specified cycle timing by observing either chart pips, speed trace, manifold vacuum trace, or concentration traces. Deviation by more than 2 seconds from the specified time for each mode will make the data of questionable value.

(b) Time correlate the hydrocarbon, carbon monoxide, and carbon dioxide charts. Use all clues available to determine the location on the chart of concentrations corresponding to each mode. Use judgment in recognizing and compensating for trace abnormalities.

(c) Locate on each chart the last three (3) seconds before HC, CO and CO2 concentration changes indicate the beginning of the 0-25 acceleration. From this last three (3) second period determine the integrated or time average concentration for the idle concentration.

(d) Mark off the 11.5 seconds following the point located in step c. Inte

grate or time average the concentrations in this interval for the 0-25 acceleration concentrations.

(e) Locate the last three (3) seconds before concentration changes indicate the beginning of the 30-15 deceleration. Integrate or time average the concentrations for the cruise 30 values.

(f) Locate chart scale reading (ordinate) where peak width equals eleven (11) seconds for 30-15 deceleration. Integrate or time average the concentrations between the intersections of this scale reading with the curve for the 3015 deceleration values.

(g) Locate the last three (3) seconds before concentration changes associated with the beginning of the 15-30 acceleration and integrate or time average the concentrations for the cruise 15 value.

(h) From the initiation of the 15-30 (50) acceleration located in step g, measure 12.5 seconds forward in time and evaluate the integrated or time average concentration for the 15-30 value.

(i) Locate chart scale reading where peak width equals 25 seconds for the 5020 deceleration mode. Integrate or time average the concentrations between the intersections of this scale reading with the curve for the 50-20 deceleration values. The "time average concentrations" equal the sum of the concentration values for each second of time divided by the number of seconds. The concentration at any second is determined by:

(1) Reading recorder deflection. (2) Subtracting water plus CO2 response.

(3) Referring to the calibration curve to determine concentration. (A table corresponding to the calibration curve is a useful aid.)

Integration of the area under the curves has been found to be an acceptable approximation of the more rigorous "time average concentration" method.

(j) Record data for the first four warmup cycles and the sixth and seventh hot cycles.

NOTE: The time correlation of the various chart traces is emphasized. The peak spanning method of locating the deceleration modes is appropriate only for the hydrocarbon traces. Corresponding CO and CO, values should be located by time correlation.

The final reported tests results are derived through the following steps:

(a) Exhaust gas concentrations shall be adjusted to a dry exhaust volume containing 15 percent by volume of carbon dioxide plus carbon monoxide.

(b) Determine composite hydrocarbon and carbon monoxide concentrations for the first four seven-mode warmup cycles.

(c) Determine composite hydrocarbon and carbon monoxide concentrations for the sixth and seventh (hot) cycles.

(d) Combine (b) and (c) according to the formula 0.35(b) and 0.65 (c).

Example: The following example illustrates the calculation of reported values from raw data. The raw concentrations used in the warmup portion of the example represent the average mode concentrations for the first four cycles.

Since hydrocarbons, carbon monoxide, and carbon dioxide are all measured with the same moisture content, no moisture correction is required to convert the results to s dry basis. The correction factor

15

co+co,

is applied to the measured concentrations of hydrocarbons and carbon monoxide for each load mode and the idle mode. For the deceleration modes the measured concentrations are multiplied by

15

6HC+CO+CO,

(HC expressed as % hexane). This modification is necessary to compensate for the large percentage of carbon atoms which remain in organic form during these modes. (Special treatment will be necessary for cases involving fuel shutoff during deceleration in accordance with a substantially equivalent procedure agreed to by the Surgeon General.)

By a similar procedure the hot portion of the test yields composite values of 680 and 2.21. The reported overall composite values

are:

0.35 (697) +0.65 (680)=686 ppm HC. 0.35 (2.27) +0.65 (2.21)=2.24% CO.

1 The average concentration for each mode for the first four warmup cycles is determined, and then the CO plus CO, correction factor is applied to this average for each mode.

1

§ 85.84 Test vehicles.

(a) Emission data vehicles. (1) Four vehicles of each engine displacement will be run for emission data. Where an engine displacement projected sales volume represents less than one half of one percent of the last full model year's total United States sales of all vehicles subject to this part, then a total of two vehicles would be required for that displacement. Each manufacturer, however, must accumulate data on a minimum of four vehicles to qualify for certification.

(2) Vehicles shall be selected so as to be equipped as nearly as possible with transmission and carburetors in proportion to the manufacturer's percentages thereof sold in the United States during latest full model year for which sales statistics are available.

(3) An engine and transmission combination need not be tested in more than one car model except that where the weight, power train, or other characteristics of any car model may reasonably be expected to increase emissions, the engine and transmission combination shall also be tested in such model.

(b) Durability data vehicles. The durability data vehicles shall comprise a minimum of 4 and a maximum of 10, the number being determined by selection of those combinations of engine displacement and transmission options (automatic and manual) which represent at least 70 percent of the manufacturer's total sales in the United States during the latest full model year for which sales statistics are available, selected in order of sales volume: Provided, however, That when such manufacturer's total latest full model year sales in the United States represent less than 10 percent of all domestic sales of vehicles subject to this part, the number of durability data vehicles will be determined by the number of engine displacement and transmission options comprising at least 50 percent of domestic sales by the manufacturer during such model year, but in no event shall there be less than 4 vehicles unless a lesser number is agreed to by the Surgeon General as meeting the objectives of this procedure.