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Volkswagen reduces NOx emissions by 80% for diesel engines



Volkswagen has developed a new generation of SCR (Selective Catalytic Reduction) dual injection system, which guarantees ultra low nitric oxide (NOx) emission in diesel cars.

Real-world driving tests confirm that the new SCR technology reduces NOx emissions by 80%. The new generation SCR exhaust system is first built into the new Passat 2.0.1 TDI Evo, which now meets future Euro 6d emission standard specifications.

As of 2018, all new Volkswagen diesel cars are fitted with SCR AdBlue exhaust systems after treatment. In turn, the new generation of SCR technology is based on the principle of double spraying, with the AdBluer reagent sprayed immediately after two sets of SCR catalysts.

The AdBlue system has so far compensated for the historical shortcomings of diesel engines, but with the innovative dual-spray process the next stage of development is reached. Today's diesel engines produce less CO2 emissions than gasoline engines because diesel has a higher energy density and is much more efficient in combustion.

The double-spray process requires a second SCR catalyst mounted at the bottom of the car. Due to the longer engine distance, the exhaust gas temperature behind the second catalyst may be lower by 100 ° C. This extends the post-treatment possibilities of the exhaust – even with the exhaust gas temperature close to + 500 ° C, the system is still able to achieve a very high degree of purification. In addition, the blocking catalyst in front of the SCR system prevents excessive loss of ammonia.

Ammonia is needed to reduce nitrogen oxides in diesel engines. It is administered as an aqueous reagent (AdBlue) by means of a spray module in the exhaust system behind the SCR catalyst. Here the liquid evaporates by decomposition of the reagent which, when combined with the vapor, produces ammonia. In the SCR catalyst, ammonia (NH3) reacts with nitrogen oxides (NOx) to form water and harmless nitrogen (N2), which is a major component of the air we breathe.

The SCR coating is applied to the cellular structure of the diesel particle filter, allowing one component to perform multiple functions. The closely related arrangement means that the exhaust gas temperatures required for high purification after the cold engine can be reached faster – the required temperature range is from + 220 ° C to + 350 ° C to achieve more than 90% purification. These conditions are achieved in a number of operating situations. The cleaning efficiency above + 350 ° C is not reduced due to the double-spray system.

Volkswagen will gradually introduce new technology in all models with 2.0 TDI Evo engines. The new Golf model, soon to make its world premiere, also plans to double-spray all TDI versions of the 2.0 TDI Evo with 110 kW (150 hp) already installed in the new Passat.

1) Passat Variant 2.0 TDI Evo 110 kW / 150 PS (NEFZ) Fuel consumption in l / 100 km: 4.5 liters in urban / 3.6 liters in urban / 4 liters in combined mode. C02 emissions in combined mode are 104 g / km, Class A + efficiency.

Fuel consumption Passat Limousine 2.0 TDI Evo 110 kW / 150 PS (NEFZ): l 4.5 liters in city / 3.5 liters outside city / 3.9 liters in combined mode. C02 emissions are 101 g / km, efficiency class A +.

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