Division 2.4.2.1

The parent engine shall meet the emission requirements on the reference fuels G_R and G₂₅ or on the equivalent fuels created using admixtures of pipeline gas with other gases as specified in Appendix 1 of Annex IX in the case of CNG, on the reference fuels G_R and G₂₀ or on the equivalent fuels created using admixtures of pipeline gas with other gases as specified in Appendix 2 of Annex VI in the case of LNG, or on the reference fuels A and B in the case of LPG, as specified in Annex IX. Fine-tuning of the fuelling system is allowed between the tests. This fine-tuning will consist of a recalibration of the fuelling database, without any alteration to either the basic control strategy or the basic structure of the database. If necessary the exchange of parts that are directly related to the amount of fuel flow such as injector nozzles is allowed.