Engine Operation 26 UENR4490-01 Exhaust gases and an atomized mist of ammonia and carbon dioxide enter the SCR reaction chamber. Together with the SCR catalyst inside the chamber, the mixture undergoes a chemical reaction that produces nitrogen gas and water vapor. There is an oxidation catalyst after the SCR catalyst. The oxidation catalyst reacts with the excess ammonia to produce oxides of nitrogen and water vapor. Refer to Systems Operation, Testing and Adjusting, “DEF Dosing Control System” for more information on the DEF system.
i05833115 Clean Emissions Module (Diesel Oxidation Catalyst (DOC), Diesel Particulate Filter (DPF) and Selective Catalytic Reduction (SCR) System) To meet current emissions legislation requirements, a small amount of certain chemical compounds that are emitted by the engine must not be allowed to enter the atmosphere.