Document ID: chunk:federal_register_of_legislation:F2023L00129:reg:20:p20
Version: federal_register_of_legislation:F2023L00129
Segment Type: reg
Provision Reference: reg 20 (pt 20/29)
Character Range: 273967–276809

traps requiring special additives in the fuel to ensure the regeneration process), the decision to include it in the same family shall be based on technical elements provided by the manufacturer. These elements shall indicate that the expected emission level of the equipped engine complies with the same limit value as the non-equipped engine.
 When an engine has been certified with an after-treatment system, whether as parent engine or as member of a family, whose parent engine is equipped with the same after-treatment system, then this engine, when equipped without after-treatment system, shall not be added to the same engine family.
5.2.4. Choice of the parent engine
5.2.4.1. Compression ignition engines
 Once the engine family has been agreed by the Type Approval Authority, the parent engine of the family shall be selected using the primary criterion of the highest fuel delivery per stroke at the declared maximum torque speed. In the event that two or more engines share this primary criterion, the parent engine shall be selected using the secondary criterion of highest fuel delivery per stroke at rated speed.
5.2.4.2. Positive ignition engines
 Once the engine family has been agreed by the Type Approval Authority, the parent engine of the family shall be selected using the primary criterion of the largest displacement. In the event that two or more engines share this primary criterion, the parent engine shall be selected using the secondary criterion in the following order of priority:
(a) The highest fuel delivery per stroke at the speed of declared rated power;
(b) The most advanced spark timing;
(c) The lowest EGR rate.
5.2.4.3. Remarks on the choice of the parent engine
 The Type Approval Authority may conclude that the worst-case emission of the family can best be characterized by testing additional engines. In this case, the engine manufacturer shall submit the appropriate information to determine the engines within the family likely to have the highest emissions level.
 If engines within the family incorporate other features which may be considered to affect exhaust emissions, these features shall also be identified and taken into account in the selection of the parent engine.
 If engines within the family meet the same emission values over different useful life periods, this shall be taken into account in the selection of the parent engine.
6. Test conditions
6.1. Laboratory test conditions
 The absolute temperature (Ta) of the engine intake air expressed in Kelvin, and the dry atmospheric pressure (ps), expressed in kPa shall be measured and the parameter fa shall be determined according to the following provisions. In multi-cylinder engines having distinct groups of intake manifolds, such as in a "Vee" engine configuration, the average temperature of the distinct groups shall be