VW Doubles Up on SCR
Although you might think that after the exceedingly expensive diesel contretemps Volkswagen would be done with compression-ignition engines, that’s not at all the case, at least in Europe. But this time they’re really going after the nitrogen oxides in the exhaust gas: They are fitting the 2.0 TDI Evo engine that is currently used in the Euro Passat and which will be used in the next-gen Golf with two selective catalytic reduction (SCR) systems.
There is one SCR catalyst that is located between the turbocharger, diesel oxidation catalytic converter and connector to the silencer pipe. Then there is a second, located in the underbody of the system.
This allows two doses of AdBlue, the fluid that is injected into the exhaust gas ahead of an SCR catalytic converter to address the nitrogen oxides that are produced by combustion. The fluid is evaporated and becomes ammonia (NH3), which, on the inside of the converter, reacts with the coating and transforms the nitrogen oxides into water and plain, old nitrogen.
In the new setup, they get two cracks at this.
According to Volkswagen, the dual system reduces NOx levels by about 80 percent compared to the previous generation of SCR exhaust gas treatment systems.
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