Patent ID: 7690337

Claim:
An internal combustion engine comprising: a crankshaft rotatable about a crankshaft axis of the engine; 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; 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 during a single rotation of the crankshaft; two crossover expansion valve ports, each of the two crossover expansion valve ports seating a corresponding crossover expansion valve; a crossover passage interconnecting the compression and expansion cylinders, the crossover passage including a crossover compression (XovrC) valve and at least one of the two crossover expansion (XovrE) valves, the crossover passage defining a pressure chamber between the crossover compression (XovrC) valve and the least one of the two crossover expansion (XovrE) valves; a cylinder head closing an end of the expansion cylinder and including the two crossover expansion valve ports; and two ignition sources disposed in the expansion cylinder, each of the two ignition sources including an ignition source center, the two ignition sources operable to ignites an air/fuel mixture to establish a flame front of burning gases in the expansion cylinder; wherein, for each of the two ignition source centers, a distance from the respective ignition source center to a nearest peripheral edge of the two crossover expansion valve ports is greater than a distance from a center of the expansion cylinder to a nearest peripheral edge of the two crossover expansion valve ports.