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.