The SCRi system works in three steps. First, the exhaust gas passes through an oxidation catalyst to eliminate HC and CO emissions and at the same time oxidize NO to NO₂. Second, urea (AdBlue) is injected into the exhaust stream and routed into a second module, consisting of a PM-METALIT followed by a turbulent SCR catalyst. In the coated PM-METALIT, the injected urea is converted to ammonia, while at the same time fine particles are continuously filtered and oxidized. Emitec’s PM-METALIT does not need periodic active regeneration and ash removal maintenance.

Finally, the filtered exhaust gas and the reducing agent pass simultaneously over an efficient and compact SCR catalyst, which uses a combination of Emitec’s turbulent longitudinal and perforated foils, making it possible to reduce the catalyst volume by approximately one-third and fit it together with the PM-METALIT in a compact housing.

Diesel passenger cars from several OEMs are being fitted with the SCRi system in both the US and Europe.