We have devised a scheme for the energy-generating unit based on the internal combustion engine 1Ch 6.8/5.4 with a spark ignition and a two-stage system for the recovery of heat from the exhaust gases. The basic elements for the first and second stages of the heat recovery system have been selected. A first stage involves a rotary piston expansion machine while a second stage employs the fuel conversion.We have studied effective parameters for the engine 1Ch 6.8/5.4 with a system of the deep two-stage recovery of heat from exhaust gases under different modes of operation. The dependences were established for change in the specific effective fuel consumption on the power of the energy-generating installation using only the conversion of fuel and in a combination with the expansion machine.The dependences have been derived for the operational parameters of a rotary piston engine on consumption of a working body. We have determined temperatures of the working bodies in a reactor and the heat capacity of exhaust gases depending on the load on the engine, as well as the necessary amount of energy to convert ethanol into synthesis gas. The dependences have been obtained of the degree of ethanol conversion on the reaction temperature and the mass flow rate through the reactor. We have established the dependence of specific heat of the chemical reaction on the degree of conversion.It was established that when reaching full conversion in line with the reaction of decomposition the entire liquid ethanol is completely converted into combustible synthesis gas, whose main components are hydrogen, carbon monoxide, and methane. The estimated specific lower combustion heat of the synthesis gas is 28.79 MJ/kg. Obtaining 1 kg of synthesis gas requires 4.0 MJ of thermal energy.It was determined that under condition of applying the conversion of fuel and, accordingly, the addition of synthesis gas, the specific effective ethanol flow rate, depending on the mode of engine operation, decreases by up to 12 %. The amount of energy that needs to be used in the reactor for obtaining synthesis gas is 50…65 % of the heat released with the exhaust gases under a given mode of operation.It has been established that the application of a rotary-piston expansion machine that acts as the first stage in the recovery of heat from exhaust gases has made it possible to gain an increase in the capacity of the energy-generating unit of 27 %.It has been found that the use of two stages of heat recovery leads to a decrease in the specific effective fuel consumption by 29 %