The main difficulty for the one-dimensional simulation of pressure waves in the inlet and exhaust systems of Internal Combustion Engines consists in the modeling of singularities (area changes, bends, junctions, etc.). The models presented in the literature are based on the behavior of the singularity in steady flow. However the pressure losses due to the wave propagation are different from those obtained in stationary flow. The authors’ objective is to propose models with a better precision based on the non steady study of the singularities which can be found in Internal Combustion Engines. Specifically, this paper presents the investigation of the pipe wall friction factor and the sudden contraction area. The first step consists in studying the behavior of pressure waves through pipes with the Fluent CFD code. Next, a model parameterized with the Reynolds number is proposed for the pipe wall friction factor while another one with the Mach number is proposed for the sudden contraction area. These models are included in a 1-D simulation code. Finally, in order to evaluate the accuracy of the simulation program, the models are compared with experimental data. The results show a satisfactory agreement between model predictions and experimental measurements.

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