In order to meet the requirements of future worldwide emission legislation, new improved designs of catalytic converters will be introduced for mass production. Substrates featuring high cell density combined with ultra thin walls offer significant improvements in catalytic efficiency, because of the increased geometric surface area and the reduced thermal mass. At the same time, the position of the catalytic converter within the exhaust system will be moved closer to the engine. In order to guarantee these mechanical durability of the new substrates under increased thermal and mechanical stress, new test procedures are required. This paper presents an examination of the thermal and mechanical loads relating to various engines and an evaluation of a new representative test procedure.