Abstract: An internal combustion engine which operates under Otto cycle during starting, idle and low load operations and which operates on a diesel cycle during high load operations. A first combustion chamber is formed in the head of an internal combustion engine and is smaller in diameter than the second combustion chamber formed by the containing surfaces of the piston and cylinder below the head. An air swirl is created in the second chamber through the intake valve, and as the piston reaches top dead center, the swirl is transferred to the first combustion chamber. Ignition means is provided in the first combustion chamber. A fuel injector is provided in the first combustion chamber and directs fuel against the direction of the swirling air for forming a stratified fuel charge around the ignition means for operating the engine on the Ott cycle during start, idle and low load operation.