The SCR catalytic converter of the Passat BlueTDI together with the additive AdBlue selectively converts nitrogen oxides (NOx) in the exhaust stream into nitrogen and water. This is in addition to an oxidation catalytic converter and diesel particulate filter which are also used to reduce the entire range of emissions. AdBlue is carried in an auxiliary tank. It is sprayed into the exhaust stream by a module downstream of the diesel particulate filter and oxidations catalytic converter. The fluid is metered according to the exhaust mass flow rate. Engine management ensures precise control based on information from the NOx sensor.
