Wang et al. [15] investigated numerically the sources of the total pressure losses in an exhaust port geometry. For small fixed valve lifts at room temperatures, the total pressure losses over the exhaust port were divided into sections and the major cause of the loss was identified by comparison to empirical formulas.The alternation of the flow coefficient obtained with five different exhaust port geometries under constant and pulsating inflow boundary conditions have been investigated by Bohac and Landfahrer [9]. The experimental setup was a flow bench measurement at fixed valve lifts and room temperatures, where a variation of 6% increase and 7% decrease of the flow coefficient has been observed. When averaged over different valve lifts, an increase of the flow coefficient of 0.5–2.5% was measured. Therefore, Bohac
and Landfahrer concluded that this percentage is small compared to the total engine performance and steady flow bench measurements are a valid assumption to obtain the flow coefficient used for the engine optimization. Semlitsch et al. [16] investigated the