A FUEL INJECTION SYSTEM FOR A SPARK-IGNITION INTERNAL COMBUSTION ENGINE AND RELATIVE CONTROL METHOD

A fuel injection system (1) for a spark-ignition internal combustion engine having a number of cylinders (11), where a plurality of respective main combustion chambers (MC) are defined; a number of first injectors (2) and spark plugs (13) coupled to the cylinders (11); a number of combustion pre-chambers (PC), each obtained in the area of a respective spark plug (13); a number of extraction ducts (17; 28), which originate from a respective cylinder (11) to extract the gas mixture present inside the respective main combustion chamber (MC); a reserve (18), where the gases extracted by the extraction ducts (17; 28) are mixed with the quantity of fuel needed to obtain a combustion under stoichiometric conditions inside the combustion pre-chambers (PC); and a number of second injectors (27), each coupled to a respective combustion pre-chamber (PC), into which it injects the gas-and-fuel mixture coming from the reserve (18).