Abstract: Apparatus having fuel combustion cylinders for urging the rods of pistons operating therein through power strokes, and fluid pressure pistons, also operating in cooperating cylinders, which are correspondingly urged during said power strokes through movement causing the production of a pressure fluid which is thereafter utilized, on demand, to do work. In the transmission of said movement-producing forces of said fuel-powered apparatus input to said pressure fluid output, a linkage mechanism is advantageously utilized to provide a pressure pattern in the pressure fluid which starts at an optimum low value and progressively builds up. This effectively reverses the pressure pattern of the combustion fuel which consists of a rapid-expansion gas having an initial maximum value and, due to expansion, progressively diminishes in value.