It is known that more than 80% of global energy is produced by internal combustion engines. Therefore, the improvement of working cycles and modernization of systems and components of piston and combined internal combustion engines with the aim of improving their technical and economic indicators is one of the urgent tasks in the global energy sector. Research in this area was undertaken mainly by means of numerical simulations or experimentally under static conditions. The data about the gas exchange processes in unsteady conditions is very limited and rather controversial. This work aims to obtain additional, clarifying information about the gas dynamics and the local heat transfer in the air-gas tract of internal combustion engines and to find ways of improving the processes. The results of mathematical modeling and experimental studies of the gas exchange processes in the intake and exhaust tracts of piston engines with and without supercharging are presented in the article. Experimental studies were conducted on full-scale models of the single-cylinder engine. The calculated and experimental dependences of the change of instantaneous velocity and pressure of the gas flow in the air-gas tracts on the rotation angle of the crank shaft are presented in the article. Transverse profiling of the channels is proposed as a way to improve gas exchange processes in the inlet and exhaust pipes of internal combustion engines. A method of reducing pulsations of pressure and gas flow velocity (on average 2-fold) in the intake pipe of the combined internal combustion engine is proposed in the article.