INTAKE PORT FUEL INJECTION ENGINE

In a semi-direct injection engine for injecting fuel from a fuel injection valve arranged in an intake port, toward a combustion chamber while an intake valve is open, a piston 30 has first and second cavities 32 and 33 formed in a top surface thereof and located on exhaust and intake valve sides, respectively, and a protuberance 34 protruding upward from the top surface to separate the first and second cavities 32 and 33 from each other. The protuberance 34 is arranged such that the first cavity 32 is smaller than the second cavity 33 and that an electrode 6a of a spark plug 6 arranged in the combustion chamber faces the second cavity 33.