Direct fuel injection internal combustion engine

A direct fuel injection internal combustion engine comprises a combustion chamber (1), a fuel injection valve (11) and a spark plug (12). The combustion chamber (1) has a piston (4, 104) including an outer cavity (16, 116) located in a top surface of the piston (4, 104) and an inner cavity (17, 117) located in the outer cavity (16, 116). The outer and inner cavities are substantially axially symmetrical about the reciprocation axis (14, 114) of the piston (4, 104). The fuel injection valve (11) is arranged adjacent the reciprocation axis (14, 114) of the piston (4, 104) to inject a fuel stream directly into the combustion chamber (1). The spark plug (12) is arranged adjacent the reciprocation axis (14, 114) of the piston (4, 104) to ignite a fuel-air mixture inside the combustion chamber (1). The direct fuel injection internal combustion engine further comprises a control unit (13) configured to vary at least one of frequency and start timings of the fuel injection valve (11) based on an engine operating condition.