Abstract: An internal combustion engine has a turbocharger inlet flange mounted to the outlet flange of the exhaust manifold of the engine. The exhaust gas flow out of the manifold is through two ports having a centrally located guide wall directing flow from the manifold out the flange into the turbocharger inlet. The two ports are trapezoidal in shape with a short common dividing wall which, for each port, blends at a short radius into two diverging straight walls, one at each end of the common wall, and which blend from their ends into the outer wall of the port, resulting in trapezoidal port shape. The inlet flange of the turbocharger casing has ports matching and in registry with the two ports of the exhaust manifold flange.