Division 1.2.1 Exhaust emissions type-approval of an engine running on CNG and laid out for operation on either the range of H-gases or on the range of L-gases.F1

The parent engine shall be tested on the relevant reference fuel, as specified in Annex IX, for the relevant range. The fuels are G _R (fuel 1) and G ₂₃ (fuel 3) for the H-range of gases and G ₂₅ (fuel 2) and G ₂₃ (fuel 3) for the L-range of gases. The parent engine shall meet the requirements of this Regulation without any readjustment to the fuelling between the two tests. One adaptation run over one WHTC hot cycle without measurement is permitted after the change of the fuel. After the adaptation run the engine shall be cooled down in accordance with paragraph 7.6.1 of Annex 4 to UNECE Regulation No 49.