Patent ID: 7637234

Claim:
A split-cycle 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; and at least one helical crossover passage interconnecting the compression and expansion cylinders, each of the at least one helical crossover passage including: a crossover compression valve and a crossover expansion valve defining a pressure chamber therebetween, a generally straight runner section in a downstream portion of the helical crossover passage, and a helical end section integrally connected to the runner section and disposed over the crossover expansion valve, the crossover expansion valve including a valve stem and head, the helical end section enclosing a funnel spiraling about the valve stem, wherein the funnel forces incoming air to rotate about the valve stem prior to entering the expansion cylinder, wherein the runner section, of a first crossover passage of the at least one crossover passage, is a tangential runner section, which directs air flow into the funnel of the helical end section of the first crossover passage in a flow path that is within plus or minus 20 degrees of parallel relative to a tangential line extending through a point in the expansion cylinder's perimeter which is closest to the valve stem corresponding to the first crossover passage.