Patent ID: 7954461

Claim:
An engine comprising: a crankshaft, rotating about a crankshaft axis of the engine; an expansion piston slidably received within an expansion cylinder and operatively connected to the 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 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; and a crossover passage interconnecting the compression and expansion cylinders, the crossover passage including an inlet valve and a crossover valve defining a pressure chamber therebetween; characterized in that the ratio of cylinder volumes from bottom dead center (BDC) to top dead center (TDC) for either one of the expansion cylinder and compression cylinder being 40 to 1 or greater; and the engine comprises a fuel injection system operable to add fuel to the exit end of the crossover passage.