Tightening environmental requirements and rising fuel prices are forcing developers to look for ways to improve the efficiency of vehicle engines. The use of a combined power plant with more than one energy source is the most efficient. Therefore, there is a need to improve the efficiency of pneumatic hybrid power plants by utilizing thermal energy emitted into the atmosphere with exhaust gases and energy removed from the cooling system of an internal combustion engine. One of the possible systems for using the heat of an internal combustion engine exhaust gases is the combined power pneumatic with separate gas flows which is a piston pneumatic motor with internal heat supply. The pneumatic motor with internal heat supply is based on the PD-10U (ПД-10У) two-stroke starting engine, from which the standard fuel and ignition systems were dismantled. A crankshaft driven pneumatic valve is mounted on the cylinder head. During the research work the polynomial equation was obtained. It allows to assess qualitatively and quantitatively the influence on the effective power, generated by the pneumatic engine, of the compressed air supply system adjusting parameters, cylinder walls temperatures, as well as the temperatures of exhaust gases, entering the cylinder from internal combustion engine