METHOD OF OPERATING AN INTERNAL COMBUSTION ENGINE

A method of operating an internal combustion engine, wherein the engine is operated in an injector learning mode in which an injection parameter associated with a nominal fuel quantity of a pilot injection is learned, includes performing a learning pilot injection based on a candidate value for the injection parameter to influence injection of the nominal fuel quantity and determining a parameter indicative of the actually injected fuel quantity based on the in-cylinder pressure during combustion of the learning pilot injection. The learning pilot injection is operated at an early timing such that combustion thereof complete occurs within a learning window positioned before combustion TDC and before the next combustion starts. The pressure is measured over the learning window, so that the determination of the parameter indicative of the actually injected fuel quantity takes into account essentially the entire combustion event of the learning pilot injection.