The catalytic converter selectively converts nitrogen oxide in the exhaust gases into nitrogen and water. To do this, it uses a synthetically produced aqueous urea solution, carried in an auxiliary tank. The substance, containing 32.5 per cent urea, is added continuously to the exhaust tract, upstream of the Selective Catalytic Reduction (SCR) catalytic converter. It is metered according to the mass flow rate of the exhaust gas and is regulated by the engine management system, which receives information from the NOx sensor.
