Method for fuel injector characterization

A method of operating a fuel injection system for a motor vehicle, the method comprising:

• operating a fuel injector to perform a fuel injection, the fuel injector being in fluid communication with a fuel rail;
• sampling a rail pressure in the fuel rail during the fuel injection;
• regulating the rail pressure at a desired injection pressure, Pinj, to the fuel injector;
• after the desired injection pressure, Pinj, is reached, switching off a high pressure pump and closing a pressure regulator;
• measuring an overall leakage on variations of the rail pressure across an engine cycle for the motor vehicle and between two engine positions of an internal combustion engine for the motor vehicle;
• energizing the injector with an energization-time, ETinj, after an inherent cylinder top-dead-center, TDC, to not produce a torque;
• calculating an injection effect on the rail pressure, DPinj;
• calculating an actual injected quantity, Qinj, as a function of DPinj and Pinj;
• collecting a characterization point as a function of Qinj, Pinj and ETinj into memory of an electronic control unit;
• and
• determining if a new target pressure is requested, wherein if the new target pressure is requested, the rail pressure is regulated at the new target pressure, and wherein if the new target pressure is not requested, the current rail pressure is utilized to measure overall leakages of the rail pressure.

A method of operating a fuel injection system for a motor vehicle, the method comprising:

• operating a fuel injector to perform a fuel injection, the fuel injector being in fluid communication with a fuel rail;
• sampling a rail pressure in the fuel rail during the fuel injection;
• regulating the rail pressure at a desired injection pressure, Pinj, to the fuel injector;
• after the desired injection pressure, Pinj, is reached, switching off a high pressure pump and closing a pressure regulator;
• measuring an overall leakage on variations of the rail pressure across an engine cycle for the motor vehicle and between two engine positions of an internal combustion engine for the motor vehicle, wherein the overall leakage on the variations of the rail pressure defined as DPLEAK=Pa,LEAK−Pb,LEAK, where Pa,LEAK is measured at Θa and Pb, LEAK is measured at Θb, where Θa and Θb are two different angles of a crankshaft of the internal combustion engine;
• energizing the injector with an energization-time, ETinj, after an inherent cylinder top-dead-center, TDC, to not produce a torque;
• measuring injection and leakage effects on the rail pressure variation defined as DPINJ+LEAK=Pa,INJ−Pb,INJ, where Pa,INJ is measured at Θa and Pb,INJ is measured at Θb;
• calculating the injection effect on the rail pressure defined as DPinj=DPINJ+LEAK−DPLEAK;
• calculating an actual injected quantity, Qinj, as a function of DPinj and Pinj;
• and
• determining if a new target pressure is requested, wherein if the new target pressure is requested, the rail pressure is regulated at the new target pressure, and wherein if the new target pressure is not requested, the current rail pressure is utilized to measure overall leakages of the rail pressure.