In vehicle construction, die-cast aluminium components are being used increasingly due to several factors. On the one hand, near net shape parts with complex geometry are manufactured under low cycle time per unit, and on the other hand Al-parts fundamentally contribute to automotive lightweight construction owing to their high specific strength. To realize supporting structural components made from Al-cast alloy, the knowledge of material behaviour under cyclic loading is essential, which is mainly contributed by microstructural influences and inhomogeneous structure caused by the manufacturing process. Their formation is strongly driven by process parameters and component design. To examine the fatigue strength of a housing made from the die casting alloy AlSi9Cu3, samples are retrieved from the component, and tested following a one-step Wöhler fatigue test. The main focus concerning the fatigue testing lies on investigating the influence of porosity and cast skin. Based on the preliminary examination, samples are taken from areas of the housing with different pore size and pore distribution. The results show a reduction of fatigue strength due to increased porosity but no effect is caused by the cast skin. A second focal point is to determine the optimisation potential of the examined housing structure. Therefore the distribution of damage under operating load is calculated and critical areas get shape optimised. In a second optimisation cycle, a topology optimisation considering the available design space as well as constraints conditional to manufacturing and mounting is carried out. Viewed in terms of lightweight construction and the supporting function of the housing in the complete chassis, a maximisation of stiffness and reduction of weight compared to the former structure is defined as the objective function. The obtained structure can be seen as a design proposal for novel housing solutions.