Section 86.096-24 - Test vehicles and engines(a)General. This paragraph applies to the grouping of vehicles or engines into families.(1) The vehicles or engines covered by an application for certification will be divided into groupings of engines which are expected to have similar emission characteristics throughout their useful life. Each group of engines with similar emission characteristics is defined as a separate engine family.(2) To be classed in the same engine family, engines must be identical in all the respects listed in paragraphs (a)(2) (i) through (x) of this section. (i) The cylinder bore center-to-center dimensions.(iv) The cylinder block configuration (air-cooled or water-cooled: L-6, 90 deg., V-8, and so forth).(v) The location of the intake and exhaust valves (or ports).(vi) The method of air aspiration.(vii) The combustion cycle.(viii) Catalytic converter characteristics.(ix) Thermal reactor characteristics.(x) Type of air inlet cooler (for example, intercoolers and after-coolers) for diesel heavy-duty engines.(3)(i) Engines identical in all the respects listed in paragraph (a)(2) of this section 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 features of each engine listed in paragraphs (a)(3)(i) (A) through (G) of this section.(B) The surface-to-volume ratio of the nominally dimensioned cylinder at the top dead center positions.(C) The intake manifold induction port sizes and configuration.(D) The exhaust manifold port size and configuration.(E) The intake and exhaust valve sizes.(G) The camshaft timing and ignition or injection timing characteristics.(ii) Light-duty trucks and heavy-duty engines produced in different model years and distinguishable in the respects listed in paragraph (a)(2) of this section are treated as belonging to a single engine family if the Administrator requires it, after determining that the engines may be expected to have similar emission deterioration characteristics.(4) Where engines are of a type which cannot be divided into engine families based upon the criteria listed in paragraphs (a)(2) and (3) of this section, the Administrator establishes families for those engines based upon those features most related to their emission characteristics. Engines that are eligible to be included in the same engine family based on the criteria in paragraphs (a)(2) and (a)(3)(i) of this section may be further divided into different engine families if the manufacturer determines that they may be expected to have different emission characteristics. This determination will be based upon a consideration of the features of each engine listed in paragraphs (a)(4) (i) through (iii) of this section.(i) The dimension from the center line of the crankshaft to the center line of the camshaft.(ii) The dimension from the center line of the crankshaft to the top of the cylinder block head face.(iii) The size of the intake and exhaust valves (or ports).(12) Those vehicles covered by an application for certification which are equipped with gasoline-fueled or methanol-fueled heavy-duty engines will be divided into groupings of vehicles on the basis of physical features which are expected to affect evaporative emissions. Each group of vehicles with similar features must be defined as a separate evaporative emission family.(13) For gasoline-fueled or methanol-fueled heavy-duty vehicles to be classified in the same evaporative emission family, vehicles must be identical with respect to the items listed in paragraphs (a)(13) (i) and (ii) of this section. (i) Method of fuel/air metering (that is, carburetion versus fuel injection).(ii) Carburetor bowl fuel volume, within a 10 cc range.(14) For vehicles equipped with gasoline-fueled or methanol-fueled heavy-duty engines to be classified in the same evaporative emission control system, vehicles must be identical with respect to the items listed in paragraphs (a)(14) (i) through (ix) of this section.(i) Method of vapor storage.(iv) Vapor storage working capacity, within a 20g range.(v) Number of storage devices.(vi) Method of purging stored vapors.(viii) Liquid fuel hose material.(ix) Vapor storage material.(15) Where vehicles equipped with gasoline-fueled or methanol-fueled heavy-duty engines are types which cannot be divided into evaporative emission family-control system combinations based on the criteria listed above, the Administrator establishes evaporative emission family-control system combinations for those vehicles based on features most related to their evaporative emission characteristics.(b)Emission data.(2)Otto-cycle heavy-duty emission data engines. This paragraph applies to Otto-cycle heavy-duty emission data engines.(iii) The Administrator selects a maximum of two engines within each engine family based upon features indicating that they may have the highest emission levels of the engines in the engine family in accordance with the criteria described in paragraphs (b)(2)(iii) (A) and (B) of this section.(A) The Administrator selects one emission data engine first based on the largest displacement within the engine family. Then from those within the largest displacement the Administrator selects, in the order listed, the engine with the highest fuel flow at the speed of maximum rated torque, with the most advanced spark timing, with no EGR or lowest EGR flow, and with no air pump or with the lowest actual flow air pump.(B) The Administrator selects one additional engine from within each engine family. The engine selected is the engine expected to exhibit the highest emissions of those engines remaining in the engine family. If all engines within the engine family are similar, the Administrator may waive the requirements of this paragraph.(iv) If the engines selected in accordance with paragraph (b)(2)(iii) of this section do not represent each engine displacement-exhaust emission control system combination, then the Administrator selects one engine of each engine displacement-exhaust emission control system combination not represented.(v) Within an engine family/displacement/control system combination, the manufacturer may alter any emission data engine (or other engine including current or previous model year emission data engines and development engines provided they meet the emission data engines' protocol) to represent more than one selection under paragraph (b)(2)(iii) of this section.(3)Diesel heavy-duty emission data engines. This paragraph applies to diesel-cycle heavy-duty emission data engines.(i) Engines will be chosen to be run for emission data based upon engine family groupings. Within each engine family, the requirements of paragraphs (b)(3) (i) through (iv) of this section must be met.(ii) Engines of each engine family will be divided into groups based upon their exhaust emission control systems. One engine of each engine system combination must be run for smoke emission data and gaseous emission data. Either the complete gaseous emission test or the complete smoke test may be conducted first. Within each combination, the engine that features the highest fuel feed per stroke, primarily at the speed of maximum rated torque and secondarily at rated speed, will usually be selected. If there are military engines with higher fuel rates than other engines in the same engine system combinations, then one military engine is also selected. The engine with the highest fuel feed per stroke is usually the one selected.(iii) The Administrator may select a maximum of one additional engine within each engine-system combination based upon features indicating that it may have the highest emission levels of the engines of that combination. In selecting this engine, the Administrator will consider such features as the injection system, fuel system, compression ratio, rated speed, rated horsepower, peak torque speed, and peak torque.(iv) Within an engine family control system combination, the manufacturer may alter any emission data engine (or other engine including current or previous model year emission data engines and development engines provided they meet the emission data engines' protocol) to represent more than one selection under paragraphs (b)(3) (ii) and (iii) of this section.(c)Durability data.(3)Heavy-duty engines. This paragraph applies to engines, subsystems, or components used to establish exhaust emission deterioration factors for heavy-duty engines. (i) The manufacturer must select the engines, subsystems, or components to be used to determine exhaust emission deterioration factors for each engine-family control system combination. Whether engines, subsystems, or components are used, they must be selected so that their emission deterioration characteristics may be expected to represent those of in-use engines, based on good engineering judgment.(e)(2) Any manufacturer may request to certify engine families with combined total sales of fewer than 10,000 light-duty vehicles, light-duty trucks, heavy-duty vehicles, and heavy-duty engines utilizing the procedures contained in § 86.094-14 for emission data vehicle selection and determination of deterioration factors. The deterioration factors are applied only to entire engine families.58 FR 58417, Nov. 1, 1993, as amended at 75 FR 22979 , Apr. 30, 2010; 79 FR 23691 , Apr. 28, 2014