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To meet the most stringent emissions standards such as Super Ultra Low Emission Vehicle (SULEV) in California, substrates with high cell densities and ultra thin foils are needed, mounted in a close-coupled position. A new substrate design has been developed incorporating increased thermal and mechanical load in association with reduced thermal mass and improved heat transfer due to higher cell density. This paper describes the development of the new design using finite element calculation and practical test results from component and engine test benches.

In order to achieve SULEV emission legislation the overall efficiency of the exhaust gas aftertreatment system has to be increased. Beside engine-out emissions and air/fuel ratio control especially during cold start and during transient driving conditions the catalyst has to be optimized regarding cold start and efficiency under warmed-up conditions. The paper will show emission test results of different catalyst designs (various cell-densities and foil thicknesses, cone-shape catalysts and electrically heated catalysts) measured on a dynamic engine test bench. With an optimized SULEV catalyst system emission tests in a close-coupled position of a mid-size passenger car will be presented.