Volkswagen has introduced a twin dosing system in its new TDI Evo engines to improve the efficiency of the SCR exhaust gas treatment process. This involves the use of two SCR catalysts, which reduces NO
x levels by around 80 % compared with the previous generation of the respective models. The first close-coupled SCR catalyst is located between the turbocharger, the diesel oxidation catalytic converter, and the flexible connection to the silencer pipe. This arrangement means that the necessary exhaust gas temperatures of 220 to 350 °C can be achieved quickly after a cold start. The second SCR catalytic converter is further away from the engine and the temperature can be as much as 100 °C lower, which still allows the system to achieve very high conversion rates. In addition, a blocking catalytic converter downstream of the SCR system prevents excess ammonia slip. The new system will be used for the first time in the Passat 2.0 TDI Evo with the 110 kW engine. The Golf 8 will be fitted with a similar system.