A method and apparatus for carrying out combustion in an internal combustion engine of the stratified charge type is disclosed. The piston and cylinder are shaped in a manner to define a variable volume space and a main combustion chamber residing as a cavity in the top face of the piston, the cavity being in communication with the variable volume space. The cylinder has an intake port oriented to induce a swirl motion to air inducted into the variable volume space.
A shock wave chamber is defined with walls projecting from the cylinder head into the main combustion chamber when the piston in its top dead center position. The shock wave chamber (or intermediate chamber) has openings to permit circulatory transfer motion of the air to enter and exit from the central bottom thereof. The intermediate chamber is adapted to receive a plasma sonic jet directed axially downwardly therethrough to penetrate the exit opening of said intermediate chamber. Fuel injection is timed to introduce a spray of fuel to said intermediate chamber to be ignited by said plasma sonic torch passing therethrough to promote a flaming jet which extends into said main combustion chamber for completion of combustion.