Reducing Agent Injector -N474-
WARNING: This page is about a different car, the 2010 Audi Q7, 2009 Audi Q7, 2008 Audi Q7, and 2007 Audi Q7. However, it is still accessible from the selected car via links, so may be relevant.
The injection of the reductant works similarly to the injection of fuel. The SCR dosing valve injects the reductant into the exhaust gas flow upstream of the SCR catalyst. The amount of reductant that is injected is determined by the opening time of the SCR dosing valve. This opening time depends on the temperature of the exhaust gas stream upstream of the SCR catalyst, the exhaust gas flow rate and the engine's NOx emissions.