System for estimating auxiliary-injected fueling quantities

A method of estimating an auxiliary-injected fuel quantity injected into an internal combustion engine having a fuel injector responsive to an injector on-time signal to inject fuel into the engine, wherein the injector on-time signal includes separate main-injection and auxiliary-injection on-times, a fuel collection unit supplying fuel to the fuel injector, and a fuel pump supplying pressurized fuel to the fuel collection unit, the method comprising the steps of:

• disabling the fuel pump prior to fuel injection by the fuel injector;
• determining a first pressure corresponding to fuel pressure within the fuel collection unit after stabilization of the fuel pressure therein following the disabling step and prior to the fuel injection;
• determining a second pressure corresponding to fuel pressure within the fuel collection unit after the fuel injection;
• enabling the fuel pump to resume fuel pumping following determination of the second pressure;
• repeating the disabling step, both determining steps and the enabling step to determine the first and second pressures for a number of different engine operating conditions;
• determining an auxiliary-injected fuel quantity model as a function of the first and second pressures and the injector on-time signal for each of the number of different engine operating conditions;
• and
• estimating the auxiliary-injected fuel quantity according to the auxiliary-injected fuel quantity model.

System for minimizing post-injected fueling variations in an internal combustion engine, comprising:

• a number of fuel injectors each responsive to one of a corresponding number of injector on-time signals to supply fuel to the engine, each of the injector on-time signals having separate main-injection and post-injection on-times;
• a fuel collection unit supplying fuel to each of the number of fuel injectors;
• a fuel pump supplying pressurized fuel to the fuel collection unit;
• a pressure sensor in fluid communication with the fuel collection unit and producing a pressure signal indicative of fuel pressure therein;
• and
• a control circuit periodically disabling the fuel pump prior to fuel injection, and enabling the fuel pump to resume fuel pumping following fuel injection, by a selected one of the number of fuel injectors, the control circuit responsive to the pressure signal to determine a first pressure in the fuel collection unit after stabilization of the fuel pressure therein following disablement of the fuel pump and prior to fuel injection by the selected one of the number of fuel injectors, and to determine a second pressure in the fuel collection unit after fuel injection by the selected one of the number of fuel injectors and prior to resuming pumping of fuel by the fuel pump, the control circuit periodically determining the first and second pressures for remaining ones of the number of fuel injectors, the control circuit adjusting one or more of the post-injection on-times as a function of the first and second pressures for each of the number of fuel injectors to minimize post-injection fueling variations between the number of fuel injectors.