FIELD: mechanical engineering. SUBSTANCE: proposed contains working cylinder with two opposite pistons furnished with discharge and scavenging ports and fuel air ports. Mechanism converting reciprocating motion of pistons into rotation of crankshaft includes bellcranks hinge connected with each pistons and connected by articulated joints with eccentric supports secured in crankcase. Bellcranks are connected with crankshaft by connecting rods. One of pistons is made two-stepped with two-side crowns of different diameter-hot crown from side of working volume, and rear cold crown of larger diameter forming space with end face wall of cylinder connected with scavenging and bypass channels and connected with mixing system and with atmosphere through intake port. Fuel-air mixture scavenging channel is connected with fuel-air ports of cylinder and with bypass channels. Other piston is also provided with two-side crowns, hot one arranged from side of working volume, and rear one forming space with end face wall of cylinder, connected by scavenging channel with air ports of cylinder and through intake port, with atmosphere. Spark plug and bypass valve are arranged in working space of cylinder. Engine has bypass valve control mechanism including camshaft with variable profile cam installed for travel along shaft. Opening of bypass valve is provided by cam through rocker. To change bypass valve opening phase angle, cam is shifted along axis of camshaft by engine power control mechanism lever. Camshaft is coupled with crankshaft by drive, gear ratio n= 1. Power control mechanism is coupled with compression ratio changer. Invention makes it possible to increase engine power output at constant mass- dimension characteristics at reduction of production and service expenses, improved reliability, reduced consumption of fuel and discharge of toxic matter into atmosphere. EFFECT: increased power output of engine.
