In 1D/3D coupled calculations the advantages of both tools can be combined. Simulations of entire engines including locally resolved 3D phenomena are executed simultaneously. In such simulation programs, the boundary conditions change interactively during the entire calculation process.

In this way, the results of one code are fed into the other code as input. The method can be used, for example, to optimize exhaust gas recirculation in the intake manifold for a uniform exhaust/air mixture. If a phenomenological combustion model is also used in the cycle simulation, the effect on combustion behavior and emissions can be studied.