This paper presents the results of the analysis of field of flow velocity through an air filter used in a diesel engine inlet system performed in order to obtain equal flow through the filtering insert. The analysis of flow was performed with the use of Phoenics digital code, which makes it possible to solve the system of equations of weight and velocity and takes into account the effects of turbulence. The calculations used k-e turbulence model for low Reynold’s number. The digital calculations were performed for various streams of air mass flowing through the filter and characteristics of engines currently used in passenger vehicles manufactures by European and Japanese manufacturers. This paper presents standardized distributions of average velocity values and kinetic energy of turbulence in longitudinal section during the flow of air through the analyzed air filter and for various configurations of the flow system. The conducted tests made it possible to identify an optimum configuration for the flow system characterized by the most balanced profiles of velocity.