An internal combustion engine for a vehicle provides variable displacement by selectively driving one or more engine crankshafts mounted within a single unitary engine block. In several embodiments the crankshafts are connected to a common output shaft wit...

A free-piston engine that comprises a pair of parallel side-by-side combustion cylinders, a free-floating combustion piston mounted in each of said combustion cylinders for reciprocating linear motion therein, responsive to successive combustion events wit...