In the twin dosing process, AdBlue is injected by two SCR catalysts that are arranged in series, enabling a significant reduction of NOX emissions. The system will be premiered in the new Passat 2.0 TDI Evo.
The twin dosing process in the Volkswagen 2.0 TDI Evo
Volkswagen
In order to improve the SCR exhaust gas treatment of diesel engines, Volkswagen is now using twin dosing in its new TDI Evo engines. The system uses two SCR catalysts. The first SCR catalyst is located near the engine, between the turbocharger, the diesel oxidation catalytic converter and the flexible connecting piece to the silencer pipe. It's here where the required exhaust gas temperatures between 220°C and 350°C can be achieved quickly after a cold start.
A second SCR catalyst increases the conversion rate
Above this mark, e.g. when driving at high speeds on the motorway or when the vehicle is fully loaded, the engine reaches temperatures above 500°C. This is where the second SCR catalyst comes into play, which has a greater distance to the engine. This leads to temperatures that are as much as 100°C lower, enabling the system to achieve very high conversion rates. A blocking catalytic converter downstream of the SCR system prevents excess ammonia slip.
According to Volkswagen, the NOX emissions of the twin dosing process are 80 percent lower compared to models of the previous generation. The system is used in the new Passat 2.0 TDI Evo with 110 kW (150 HP). Twin dosing will also be used similarly in all of the new Volkswagen Golf 8's TDI engines.