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Future requirements of the legislative body in the USA and Europe, towards the reduction of exhaust emissions of motor vehicles, forces the automobile industry to improve its technology continually. An electrically heated catalyst, abbreviated EHC, offers a very high potential for exhaust gas reduction in the cold start phase of the engine. A team of German automobile manufacturers is therefore developing a complete EHC System and laying down specifications which will enable the supply industry to undertake goal-orientated development of following components. The complete system comprises the components: heated catalyst, electricity supplier, electronic control, cables, plug and socket connections, secondary air system and their respective functions. In the following, the possible variations of the EHC system are explained and the components presented.

The present paper describes the results of a joint development program focussing on a system approach to meet the EURO IV emission standards for an upper class passenger car equipped with a newly developed high displacement gasoline engine. Based on the well known catalyst systems of recent V6- and V8-engines for the EURO III emission standards with a combination of close coupled catalysts and underfloor catalysts, the specific boundary conditions of an engine with an even larger engine displacement had to be considered. These boundary conditions consist of the space requirements in the engine compartment, the power/torque requirements and the cost requirements for the complete aftertreatment system. Theoretical studies and computer modeling showed essential improvements in catalyst performance by introducing thin wall substrates with low thermal inertia as well as high cell densities with increased geometric surface area.