Abstract: A direct-injection spark-ignition engine operable between a stratified charge combustion mode where fuel injection is executed on a compression stroke while introducing a vertical-vortex tumble flow to an induced air drawn into a combustion chamber through an intake port, and a homogeneous combustion mode where fuel-injection early in the intake stroke produces a homogeneous air-fuel mixture, comprises a cylinder block having a cylinder, a piston movable through a stroke in the cylinder and having a centrally-formed piston bowl cavity combustion chamber in its piston head, a cylinder head mounted on the cylinder block, a centrally-located spark plug, and a fuel injector valve provided nearby the intake valve for injecting fuel directly into the combustion chamber.