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To meet LEV/ULEV - requirements, a considerable amount of development work was necessary to ensure suitable efficiency and durability of catalyst systems [1, 2, 3]. In addition to active emission reduction systems like the Electrically Heated Catalyst (EHC), Exhaust Gas Ignition (EGI) and the burner, passive systems like the HC-trap and Closed-Coupled Catalysts (CCC) are practical solutions to fulfill tighter emission requirements [4, 5, 6, 7]. Depending on the application, thermo-mechanical stresses, vibrations and efficiency degradation through aging increases with the reduction of the distance between the engine and the catalytic converter. Therefore, the test procedures which were suitable for converters which were to be placed in underfloor positions, needed to be modified according to the load spectra acting on close-coupled catalysts. This paper describes a new test strategy used during the development and design verification phase of catalytic converter systems.

From SAE-Papers and several publications, the easy, effective function and management of an EHC-System is well known. The direction of the development is now to reduce the electrical energy consumption and to show the mechanical durability of the heating structure. This paper shows that it is possible to minimize the energy consumption and that the required service life can be in principle achieved with the introduction of these developments. The physical characteristics such as mass, geometrical surface area, cell density and electrical resistance of the EHC construction could be optimized to save energy. This, in conjunction with the operating parameters of the engine, the controlling of the secondary air and the catalyst configuration, will enable the goals to be met. The design of the converter, the physical characteristics and the results of the tests are shown with the Porsche 944 S2 and 968 applications.