Section 1033.230 - Grouping locomotives into engine families(a) Divide your product line into engine families of locomotives that are expected to have similar emission characteristics throughout the useful life. Your engine family is limited to a single model year. Freshly manufactured locomotives may not be included in the same engine family as remanufactured locomotives, except as allowed by paragraph (f) of this section. Paragraphs (b) and (c) of this section specify default criteria for dividing locomotives into engine families. Paragraphs (d) and (e) of this section allow you deviate from these defaults in certain circumstances.(b) This paragraph (b) applies for all locomotives other than Tier 0 locomotives. Group locomotives in the same engine family if they are the same in all the following aspects:(1) The combustion cycle (e.g., diesel cycle).(2) The type of engine cooling employed and procedure(s) employed to maintain engine temperature within desired limits (thermostat, on-off radiator fan(s), radiator shutters, etc.).(3) The nominal bore and stroke dimensions.(4) The approximate intake and exhaust event timing and duration (valve or port).(5) The location of the intake and exhaust valves (or ports).(6) The size of the intake and exhaust valves (or ports).(7) The overall injection or ignition timing characteristics (i.e., the deviation of the timing curves from the optimal fuel economy timing curve must be similar in degree).(8) The combustion chamber configuration and the surface-to-volume ratio of the combustion chamber when the piston is at top dead center position, using nominal combustion chamber dimensions.(9) The location of the piston rings on the piston.(10) The method of air aspiration (turbocharged, supercharged, naturally aspirated, Roots blown).(11) The general performance characteristics of the turbocharger or supercharger (e.g., approximate boost pressure, approximate response time, approximate size relative to engine displacement).(12) The type of air inlet cooler (air-to-air, air-to-liquid, approximate degree to which inlet air is cooled).(13) The intake manifold induction port size and configuration.(14) The type of fuel and fuel system configuration.(15) The configuration of the fuel injectors and approximate injection pressure.(16) The type of fuel injection system controls (i.e., mechanical or electronic).(17) The type of smoke control system.(18) The exhaust manifold port size and configuration.(19) The type of exhaust aftertreatment system (oxidation catalyst, particulate trap), and characteristics of the aftertreatment system (catalyst loading, converter size vs. engine size).(c) Group Tier 0 locomotives in the same engine family if they are the same in all the following aspects: (1) The combustion cycle (e.g., diesel cycle).(2) The type of engine cooling employed and procedure(s) employed to maintain engine temperature within desired limits (thermostat, on-off radiator fan(s), radiator shutters, etc.).(3) The approximate bore and stroke dimensions.(4) The approximate location of the intake and exhaust valves (or ports).(5) The combustion chamber general configuration and the approximate surface-to-volume ratio of the combustion chamber when the piston is at top dead center position, using nominal combustion chamber dimensions.(6) The method of air aspiration (turbocharged, supercharged, naturally aspirated, Roots blown).(7) The type of air inlet cooler (air-to-air, air-to-liquid, approximate degree to which inlet air is cooled).(8) The type of fuel and general fuel system configuration.(9) The general configuration of the fuel injectors and approximate injection pressure.(10) The type of fuel injection system control (electronic or mechanical).(d) You may subdivide a group of locomotives that is identical under paragraph (b) or (c) of this section into different engine families if you show the expected emission characteristics are different during the useful life. This allowance also covers locomotives for which only calculated emission rates differ, such as locomotives with and without energy-saving design features. For the purposes of determining whether an engine family is a small engine family in § 1033.405(a)(2) , we will consider the number of locomotives that could have been classed together under paragraph (b) or (c) of this section, instead of the number of locomotives that are included in a subdivision allowed by this paragraph (d).(e) In unusual circumstances, you may group locomotives that are not identical with respect to the things listed in paragraph (b) or (c) of this section in the same engine family if you show that their emission characteristics during the useful life will be similar.(f) During the first six calendar years after a new tier of standards becomes applicable, remanufactured engines/locomotives may be included in the same engine family as freshly manufactured locomotives, provided the same engines and emission controls are used for locomotive models included in the engine family. 73 FR 37197 , June 30, 2008, as amended at 73 FR 59190 , Oct. 8, 2008