Method and apparatus for determining a start angle for a fuel injection associated with a fuel injection signal

This invention relates generally to fuel injection control systems and, more particularly, to a control system for determining the start of fuel injection events in a multi-shot fuel injection signal for each cylinder of an engine wherein the main injection timing is preserved when the start of the injection event becomes too advanced. A fuel injection control system and method for determining a start angle for a fuel injection event based upon engine speed. A controller is coupled to a plurality of fuel injectors associated with the engine and is operable to convert a predetermined timing trim value associated with each fuel injector to an angle trim value. The controller is further operable to determine a relative injection angle value for each cylinder by adding the angle trim value to a predetermined advanced pilot timing angle value and a predetermined main shot timing angle value; to compare the relative injection angle value to a maximum allowable relative injection angle value and set the relative injection angle value to the maximum if the determined relative injection angle value exceeds the maximum allowable relative injection angle value; and to determine an absolute injection angle value for each cylinder by adding the relative injection angle value to a predetermined cylinder top-dead-center offset value associated with the fuel injector for a particular cylinder. The absolute injection angle value corresponds to the position of the cylinder piston during a particular fuel injection event.