Packaging requirements to meet current and future exhaust legislations force automakers to use the given space either in the engine compartment or in underbody position as efficiently as possible. This requirement leads to substrate contours with wide ranges of different radii to fill the space with the recommended catalytic volume. Especially converters with race-track shaped substrates suffer from mechanical durability problems. They occure primarily in the region of the extreme wide radius due to erosion of the thermal expanding support mat. This is commonly known as mat erosion. A new approach to improve the durability of the substrate support system is a PatchWorkDesign support mat, which combines the advantages of an alternative fibre mat with those of the intumescent mat.