Proposal to restrict the application of CO2 specific emission limits only to NMHC and CO emissions (back-to-back comparison of NOx and PM to apply under the regulation in any case). The proposal also aligns the text where applicable with the intent of paragraph 2.3.15.: “R49 original emission limits” means the emission limits as defined in Regulation No. 49 to which the original engine system was approved."

During the June 2016 GRPE session, AEGPL raised concerns regarding the back-to-back approach for the simplified test of retrofitted dual-fuel engines because, in some cases, the hydrocarbons (HC) and/or carbon monoxide (CO) emission values of the original diesel engine are far below the emission limit (see GRPE-73 session report, para. 28). AEGPL proposed a solution in document GRPE-73-07. However the Netherlands is concerned that:

1. The emission performance of the selected diesel engine is not known (above or below the emission limit and how far from the limit);
2. Non-methane hydrocarbons (NMHC) emission cannot be disregarded because NMHC is an important air quality regulated pollutant emission; and
3. The diesel emissions of CO and HC could be far below the emission limit and hence a factor of two would not be sufficient while increasing this factor is problematic.

Contracting Parties and stakeholders have discussed a solution, presented in this proposal, to compare measured emissions of a retrofitted dual-fuel engine with the brake specific emission limits using a CO2 specific emissions approach. This proposal would amend the draft regulation pending before WP.29 (document WP.29/2016/110).