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Metallic substrates for catalysts constitute a supporting technology to meet the various emission legislations world wide for passenger cars as well as for 2- and 3-wheelers. Hot tubes offer additional advantages, especially for 2- and 3-wheelers in combination with metallic substrates or as independent systems. Low thermal capacity data indicates an early light off. High thermal conductivity assists the catalyst under engine misfiring conditions. The wall thickness of the foil material used is responsible for low back pressure and high engine performance. The greater geometrical surface area of metallic substrates and hot tubes in combination with structured surfaces offers the automotive industry an opportunity to reduce catalyst volume. Simple, economical canning methods are a field of special interest in the automotive industry. These advantages combined allow metallic substrates a significant market share in automotive applications.

Metal supported catalysts, whose early development actually started in the sixties, are used today in a few isolated cases as starter catalysts, retrofit and underfloor catalysts of small dimensions. The new Porsche Carrera 4 is the first production car to use a large main catalytic converter with metal supports. This paper describes the design of this catalyst and the advantages of using the metal supports, especially the increase in power output due to the reduction of exhaust back pressure. Also benefits in catalytic performance could be determined. The major requirement in using large metal supports in production is mechanical sturdiness. In extensive vehicle, test bench and laboratory tests and according to the theoretical calculations, the support with S-design described here has met this requirement.