Search Results

The present paper shows the catalytic behaviour of different metal supported catalysts in fresh and aged conditions. Based on the same substrate dimensions as in the Carrera 2/4 series converter, cell densities of 200, 300, and 400 cpsi were compared. Additionally, two converter types with special foil structures were investigated which claim to create turbulence effects. Benefits in weight and pressure drop were found with decreasing cell density. These effects can be explained by the constant wall thickness which is independent of the cell density for metal supports. The catalytic performance after ageing does not vary a lot as far as HC and CO are concerned. Regarding NOx, a disadvantage occurs with smaller cell numbers. This is also true for the turbulence variant with 200 cpsi. The differences in light-off behaviour are discussed supported by data from so-called FTP double-split tests and additional modal analysis.

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.