A numerical study of the flow in the exhaust port geometry of a Scania heavy-duty diesel engine is performed using the large eddy simulation (LES) and an unsteady Reynolds-Averaged Navier–Stokes (URANS) simulation approach. The calculations are performed at fixed valve positions and stationary boundary conditions to mimic the setup of an air flow bench experiment, which is commonly used to acquire input data for one-dimensional engine simulations. The numerical results are validated against available experimental data. The complex three-dimensional (3D) flow structures generated in the flow field are qualitatively assessed through visualization and analyzed by statistical means. For low valve lifts, the major source of kinetic energy losses occurs in the proximity of the valve. Flow separation occurs immediately downstream of the valve seat. Strong helical flow structures are observed in the exhaust manifold, which are caused due an interaction of the exhaust port streams in the port geometry.