Patent ID: 7954462

Claim:
An engine comprising: a crankshaft rotatable about a crankshaft axis; a power piston slidably received within a power cylinder and operatively connected to the crankshaft such that the power piston reciprocates through an expansion stroke and an exhaust stroke during a single rotation of the crankshaft and such that the ratio of the volume in the power cylinder when the power piston is at its bottom dead center (BDC) position to the volume in the power cylinder when the power piston is at its top dead center (TDC) position is 26 to 1 or greater; 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 during a single rotation of the crankshaft; a gas passage interconnecting the compression and power cylinders, the gas passage including an inlet valve and an outlet valve defining a pressure chamber therebetween; and an air reservoir connected by a reservoir passage to the pressure chamber at a location between the inlet valve and the outlet valve, the reservoir passage being selectively operable to receive compressed air from the compression cylinder to the air reservoir, and to deliver compressed air from the air reservoir to the power cylinder; wherein the engine is operable in a pre-compressed air power (PAP) mode, wherein in the PAP mode: the power cylinder receives a first charge of compressed air from the air reservoir during a first expansion stroke of the power piston; said first charge of compressed air is mixed with fuel during said first expansion stroke; and combustion of the fuel is initiated in the power cylinder during said first expansion stroke.