Method for auto-ignition operation and computer readable storage device for use with an internal combustion engine

A method for operating an internal combustion engine provided with at least one cylinder and operable in compression ignition mode, said engine comprising a fuel injector, through which fuel is injected into a combustion chamber, for each cylinder, a fuel injection control unit that controls fuel injection quantity per combustion cycle injected through each fuel injector, a piston in the engine cylinder whose compression action causes a mixture of air and fuel within the combustion chamber to be ignited during compression ignition mode, at least one inlet valve for admitting gas which includes fresh air into said cylinder, at least one exhaust valve for exhausting combusted gases from said cylinder, at least one sensor for measuring an engine operation parameter, the method comprising:

• adjusting opening and closing timings of the inlet valve and the exhaust valve so that the piston moving within the cylinder performs an intake phase, a compression phase, an expansion phase, an exhaust phase and an exhaust retaining phase;
• and during the exhaust retaining phase of the compression ignition:
• closing the exhaust valve before top dead center during an exhaust stroke of the piston and opening the intake valve after top dead center during an induction stroke of the piston;
• controlling the fuel injection control unit so as to perform a first fuel injection before top dead center of the piston stroke, which fuel reacts with excess oxygen from the previous combustion, and
• controlling the fuel injection control unit so as to perform at least one further fuel injection in the interval after top dead center of the piston stroke and before top dead center of a subsequent piston compression stroke.