Abstract: Method and apparatus for providing a stratified charge of air and a fuel-rich, fuel-air mixture to each combustion chamber of an internal combustion engine having more than one combustion section by providing alternate sources of intake air at the intake of each combustion chamber, establishing a fuel-rich, fuel-air mixture in one alternate source and switching between the alternate sources during induction of a charge of fuel and air in one of the combustion sections in response to a cyclic pressure change in another combustion section such that the charge passing into each combustion chamber will be stratified into portions of air and a fuel-rich, fuel-air mixture.