Disclosed is an active chamber engine including a cylinder fed with compressed air, a piston, a cylinder head which includes an intake duct, an intake orifice, an intake valve, wherein the volume of the cylinder is divided into an included active chamber and an expansion chamber and the torque and the speed of the engine are controlled by the opening and closing of the intake valve characterized in that the intake valve moves in the direction opposite to the flow direction of the pressurized gas stream in its opening direction and is held closed on a seat by a return spring in its closing position, and that the axial forces acting on the intake valve resulting from the pressure in the intake duct and in the cylinder are permanently balanced.