Improving the design and thermodynamic cycle of reciprocating engines remains an urgent task for the economy and energy. A review of modern research on this topic is made. This article presents data on the effect of the exhaust manifold configuration on gas dynamics and heat transfer of flows in the cylinder and exhaust system. The study was carried out on the basis of numerical simulation using the CFD method. Modernization of the design of the exhaust system consisted in the use of channels with cross sections in the form of a circle, square and triangle. The data on the boundary conditions, the design scheme, the geometric dimensions of the elements of the exhaust system and the configuration of the profiled channels are given. The article compares velocity fields, isolines of equal velocities, velocity vector tangents and heat transfer coefficients for different designs of the reciprocating engine exhaust system. It has been established that the profiling of the exhaust manifold does not actually affect the gas dynamics of the flow in the cylinder and the channel in the engine block head. It is shown that the flow structure in the exhaust system changes after the profiled channel. There is a decrease in the intensity of heat transfer in the exhaust manifold with profiled channels up to 12% compared to the base configuration. The simulation data are confirmed by the results of experimental studies. The data obtained can be useful for clarifying approaches to the modernization of the exhaust system of reciprocating engines, and they also expand the theoretical knowledge base about gas dynamics and heat transfer of stationary flows in a hydraulic system of complex configuration. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.