External or integrated water-cooled exhaust manifolds are mentioned to be favourable for the overall engine behaviour on diesel and gasoline engines. To validate this potential, an analytical study has been conducted. A diesel and a gasoline engine model were built-up in GT-SUITE to assess the influence of water-cooled exhaust manifolds at full load. These engine models have been combined with VeLoDyna tool from IAV for vehicle simulation considering heat fluxes between engine and vehicle cooling systemto show the potential of the different designs in a driving cycle, including the catalyst heating up phase.