SPARK IGNITION INTERNAL COMBUSTION ENGINE

An internal combustion engine with controlled ignition comprises a cylinder, a relative piston, and a head between which a combustion chamber is operationally defined. The cylinder and the piston define a first prismatic coupling. The engine also comprises a pre-chamber made directly inside the combustion chamber, and a male element stably connected to an upper surface of the piston to penetrate the pre-chamber at least in one portion of the relative motion of the piston in the cylinder. A spark plug is arranged to look out into the pre-chamber.