A method for decelerating an expansion piston of an engine is presented. The engine includes an expansion piston slidably received within an expansion cylinder and operatively connected to a crankshaft such that the expansion piston reciprocates through an expansion stroke and an exhaust stroke of a four stroke cycle during a single rotation of the crankshaft. A compression piston is slidably received within a compression cylinder and operatively connected to the crankshaft such that the compression piston reciprocates through an intake stroke and a compression stroke of the same four stroke cycle during the same rotation of the crankshaft. The method includes accelerating the expansion piston during the expansion stroke from the expansion piston's top dead center position, and decelerating the expansion piston during at least a portion of the expansion stroke crank angle interval between 0 degrees and 60 degrees after top dead center.
Salvatore C. Scuderi; David P. Branyon