Patent ID: 8360017

Claim:
An engine, comprising: a crankshaft rotatable about a crankshaft axis; a compression piston slidably received within a compression cylinder and operatively connected to the crankshaft such that the compression piston is operable to reciprocate through an intake stroke and a compression stroke during a single rotation of the crankshaft; an expansion (power) piston slidably received within an expansion cylinder and operatively connected to the crankshaft such that the expansion piston is operable to reciprocate through an expansion stroke and an exhaust stroke during a single rotation of the crankshaft; at least two crossover passages interconnecting the compression and expansion cylinders, each of the at least two crossover passages including a crossover compression (XovrC) valve and a crossover expansion (XovrE) valve operable to define a pressure chamber therebetween; and an electronic control unit (ECU) that controls actuation of the crossover compression (XovrC) valves and the crossover expansion (XovrE) valves to selectively utilize the at least two crossover passages; wherein the compression cylinder is operable at part-load to intake a charge of air and compress said charge into at least one but less than all of the at least two crossover passages during a single rotation of the crankshaft.