the pipe at right angles to the axis of the plume. The light source is an incandescent lamp operated at a constant voltage of not less than 15 percent of the manufacturer's specified voltage. The lamp output is collimated to a beam with a diameter which does not exceed 0.4 exhaust pipe diameters. The angle of divergence of the collimated beam shall be within 4° included angle. A light detector, directly opposed to the light source, measures the amount of light blocked by the smoke in the exhaust. The detector sensitivity is restricted to the visual range and comparable to that of the human eye. A collimating tube with apertures equal to the beam diameter is attached to the detector. It restricts the viewing angle of the detector to within 16° included angle. An amplified signal corresponding to the amount of light blocked is recorded continuously on a remote recorder. An air curtain across the light source and detector window assemblies may be used to minimize deposition of smoke particles on those surfaces provided that it does not measurably affect the opacity of the plume. The meter consists of two units, an optical unit and a remote control unit. Light extinction meters employing substantially identical measurement principles and producing substantially equivalent results but which employ other electronic and optical techniques for zeroing, spanning, and calibration than those described, are deemed to be acceptable substitutes.

(3) Recorder-a continuous recorder, with variable chart speed over a minimal range of 0.5 to 8.0 inches per minute (or equivalent) shall be used for continuously recording the transient conditions of exhaust gas opacity and engine r.p.m. The recorder scale for opacity shall be linear and calibrated to read from 0 to 100 percent opacity full scale. The opacity trace shall have a resolution within 1 percent opacity. The recorder scale for engine r.p.m. shall be linear and calibrated in units to facilitate chart reading. The r.p.m. trace shall have a resolution within 30 r.p.m. Any means other than a strip chart recorder may be used provided it produces a permanent visual record of the data which is of equal or better quality as that described above.

(4) The recorder used with the smokemeter shall be capable of fullscale deflection in 0.5 second or less. The smokemeter-recorder combination may be damped so that signals with a frequency higher than 10 cycles per second are attenuated. A separate low-pass electronic filter with the following performance characteristics may be installed between the smokemeter and the recorder to achieve the high-frequency attenuation.

(i) 3 decibel point-10 cycles per second.

(ii) Insertion loss-zero ±0.5 decibels. (iii) Selectivity-12 decibels per octave above 10 cycles per second.

(iv) Attenuation-27 decibels down at 40 cycles per second minimum.

(c) Assembling equipment. (1) The optical unit of the smokemeter shall be mounted radially to the exhaust pipe so that the measurement will be made at right angles to the axis of the exhaust plume. The distance from the optical unit to the exhaust pipe outlet shall be 1.0 to 1.5 pipe diameters but never less than 4 inches. The full flow of the exhaust stream shall be contained within and be approximately centered about the light path of the unit in order for the test to be valid.

(2) Power shall be supplied to the control unit of the smokemeter in time to allow at least 15 minutes for stabilization prior to its use.

§ 85.125 Information to be recorded.

The following information shall be recorded with respect to each test: (a) Test number.

(b) Date and time of day.
(c) Instrument operator.
(d) Engine operator.

(a) The smokemeter shall be checked according to the following procedure prior to each test:

(1) The optical surfaces of the optical section shall be checked to verify that they are clean and free of foreign material and fingerprints. They shall be cleaned if necessary; a fresh cotton swab and alcohol is useful for this purpose.

(2) The zero control shall be adjusted under conditions of "no smoke" to give a recorder trace of zero.

(3) Calibrated neutral density filters having approximately 20 percent and 40 percent opacity shall be employed to check the linearity of the instrument. The filter(s) is inserted in the light path perpendicular to the axis of the beam and adjacent to the opening from which the beam of light from the light source emanates, and the recorder response is noted. Deviations in excess of 1 percent opacity will necessitate corrective action.

(b) The instruments for measuring and recording engine rpm; air inlet restrictions; exhaust system back pressure etc., which are used in the tests prescribed herein shall be calibrated from time to time using techniques in accordance with good technical practice.

§ 85.127 Test run.

(a) The temperature of the air supplied to the engine shall be between 68° F. and 86° F. The observed barometric pressure shall be between 28.5 inches and 31 inches Hg. Higher air temperature or lower barometric pressure may be used, if desired, but no allowance will be made for possible increased smoke emissions because of such conditions.

(b) The governor and fuel system shall have been adjusted previously to limit engine performance at the levels specified by the engine manufacturer for maximum brake horsepower and maximum torque. These specifications shall be supplied with the data submitted under § 85.51.

(c) The following steps shall be taken for each test:

(1) Start cooling system.

(2) Starting with a warmed engine, determine by experimentation the dynamometer inertia and dynamometer load required to perform the accelerations in the dynamometer cycle for smoke emission tests (§ 85.122(a) (2)). In a manner appropriate for the dynamometer and controls being used, arrange to conduct the acceleration mode. Turn engine off or leave it on, as desired.

(3) Install smokemeter optical unit and connect it to the recorder. Connect the engine rpm sensing device to the recorder.

(4) Turn on purge air to the optical unit of the smokemeter, if such air is used.

(5) Check and record zero and span settings of the smokemeter recorder at a chart speed of approximately 1 inch per minute. (The optical unit may be retracted from its position about the exhaust stream, if desired.)

(6) Start the engine, if necessary, and precondition it by operating it for 10 minutes at maximum rated horsepower.

(7) Proceed with the sequence of smoke emission measurements on the engine dynamometer as described in § 85.122.

(10) Check zero and reset if necessary and check span of the smokemeter recorder. If either zero or span drift is in excess of 3 percent opacity, the test results shall be invalidated.

§ 85.128 Chart reading.

(a) The following procedure shall be employed in reading the smokemeter recorder chart.

(1) Divide the chart into consecutive 2-second intervals starting with the beginning of each of the two accelerations and the lugging mode and determine the average smoke reading during each 2second interval.

(a) Average the 45 readings in § 85.128 (a) (2) and designate the value as “a”.

(b) Average the 15 readings in § 85.128 (a) (3) and designate the value as "b". § 85.130 Test engines.

(a) The engines for which certification is requested by a manufacturer under section 206 of the Act shall be divided into engine families on the basis of engine design features. These features include: Combustion cycle (2 cycle and 4 cycle) cylinder configuration and dimensions; and method of air aspiration (natural, turbocharged, and

supercharged).

(b) Emission data engines: Two engines of each family shall be run for smoke emission data as prescribed in § 85.132(b). Within each engine family, the engines that feature the highest fuel feed per stroke, primarily at the speed of maximum torque and secondarily at rated speed, will be selected.

(c) Durability data engines:

(1) One engine from each family shall be tested for lifetime smoke emission data as prescribed in § 85.132(c). Within each family, the engine which features the highest fuel feed per stroke, primarily at rated speed and secondarily at the speed of maximum torque, will be selected for durability testing.

(2) Whenever a manufacturer's total latest full calendar year sales in the United States of engines subject to this part represents less than 5 percent of all domestic sales of engines subject to this subpart, such manufacturer shall not be required to test more than four engines for durability data. These four engines will be selected from the several families of engines in order of expected sales volume and will represent as many families as possible and shall include at least one engine using each combustion cycle and one engine using each method of air aspiration included in the manufacturer's expected production.

§ 85.131 Test conditions. (a) Maintenance:

(1) A complete record of all pertinent maintenance performed on the test engines shall be supplied with the application for certification.

(2) Maintenance on the durability engines may be performed only as a result of part failure or gross engine malfunction with the following exceptions:

(i) Only one major engine tuneup may be performed, at approximately 500 hours of dynamometer operation.

(ii) Normal lubrication services (engine and transmission oil change and oil, fuel, and air filter servicing) will be allowed at recommended intervals.

(b) Complete dynamometer - exhaust emission tests (see §§ 85.120 through 85.129) shall be run before and after any engine maintenance which can be expected to affect emissions.

§ 85.132 Durability testing and emission

measurements.

(a) Durability testing shall be simulated by operation of an engine on a dynamometer.

(b) Emission data engines: Each engine shall be operated on a dynamometer for 125 hours with the dynamometer and engine adjusted so that the engine is operating at 95-100 percent of rated speed and at 95-100 percent of maximum rated horsepower. The results of all exhaust smoke tests conducted after 125 hours of operation will be supplied with the application for certification to establish the low-use emission level of each engine.

(c) Durability data engines: Each engine shall be operated on a dynamometer for 1,000 hours with the dynamometer and engine adjusted so that the engine is operating at 95-100 percent of rated speed and at 95-100 percent of maximum rated horsepower. Exhaust smoke measurements shall be made at least every 125 hours of operation. The results shall be supplied with the application for certification and shall be used to establish the deterioration factors (see § 85.133). § 85.133 Compliance with emission

standards.

(a) The emission standards in the regulations in this part apply to the lifetime emission of equipped engines. Prior to certification, lifetime emissions can be obtained by projection of test data to

lifetime normal service. Lifetime normal service or its equivalent is taken to be 2,000 hours of prescribed dynamometer operation.

(b) It is expected that the opacity of exhaust emissions will change with use of the engine. It is assumed that emissions corresponding to 1,000 hours of prescribed dynamometer operation is the average emission of engines over their lifetime.

(c) The basic procedure for determining compliance with exhaust smoke emission standards in diesel-powered engines, is as follows:

A=

(1) Emission deterioration factors for the acceleration mode (designated as "A") and the lugging mode (designated as "B") will be established separately for each durability data engine. They shall be determined from the emission results "a" and "b," respectively, of the durability data engines.

(i) All smoke test "a" and "b" results will be plotted separately as functions of hours of operation and the two best fit straight lines will be drawn through these data points.

(ii) The deterioration factors will be calculated as follows:

(2) The "percent opacity" values to compare with the standards will be the opacity values "a" and "b" of each emission data engine multiplied by the respective factors A and B of subparagraph (1) of this paragraph. Provided that in the event that there is no durability data engine for a family of emission data

engines (as might occur in the durability data engine selection process) the deterioration factor for an engine having the same combustion cycle and the same method of air aspiration and most nearly the same fuel feed per stroke shall be used in calculating emissions for such family of emission data engines.