The results of experimental research of influence of gasdynamic unsteady on flow characteristics and heat transfer characteristics of the release process in piston engine presented in the article. The experimental investigations were carried out on full-sized model of combustion engine. The experimental unit and research methods are described. Graphs instantaneous velocity and the local heat flow in the gas-air ducts from the angle of the crankshaft, and flow characteristics of the engine are presented in the article. The data obtained at various frequencies of rotation of a cranked shaft. It is established that for exhaust tract of piston engine the nonstationarity leads to a significant reduction of heat transfer, which can take up to 2.5 times.