Abstract: The efficiency of a multi-cylinder engine is optimized by coupling the volume change in each cylinder to a common coordinate under conditions such that, at each point in the engine's cycle, the energy necessary to produce a differential volume change is reduced substantially to zero. Each cylinder is coupled to the common coordinate through a cam or through a variable-length connecting rod. The same efficiency optimization may be achieved with various combinations of cylinders in a two-cycle engine, a four-cycle engine, or a multi-cylinder compressor.

Abstract: A conservative force coupled to the piston of a reciprocating-piston engine, refrigerator, or compressor acts to counter the pressure force on the piston that arises from the change of volume of the working substance accompanying a change in the piston position. As a result, the efficiency of the engine, refrigerator, or compressor is improved to approach the theoretical thermodynamic limit of the underlying process.

Abstract: The efficiency of a multi-cylinder engine is optimized by coupling the volume change in each cylinder to a common coordinate under conditions such that, at each point in the engine's cycle, the energy necessary to produce a differential volume change is reduced substantially to zero. Each cylinder is coupled to the common coordinate through a cam or through a variable-length connecting rod. The same efficiency optimization may be achieved with various combinations of cylinders in a two-cycle engine, a four-cycle engine, or a multi-cylinder compressor.