Abstract: A method for increasing the power output in an engine, pump, or similar device, which includes a cylinder, inside which is a lever piston pivoted to make a reciprocating motion and a rotating piston mounted eccentrically in a bearing to make a rotating motion, as well as an inlet opening opening into the work chamber of the cylinder and an exhaust opening leading out of the exhaust chamber of the cylinder. At least the rotating piston is hollow or manufactured from a material lighter than the pressurized medium used in the device. The lever piston too can be hollow or manufactured from a material lighter than the medium used.