Zero Fuel Calibration

Zero fuel calibration is an algorithm used to detect deviations in individual fuel injector performance from nominal. In an overrun decel fuel shut off condition, fuel rail pressure is set to 30, 000 kPa (4, 351 psi) and small injections are made from a single fuel injector. The observed acceleration in crankshaft speed is detected and a regression line generated to predict the fueling required to achieve the expected acceleration. If the calculated fueling required to generate the expected acceleration in crankshaft speed falls outside the allowable control limits for the system, an addition routine is called to very precisely learn the adjustment to fuel injector energizing time required to achieve expected acceleration. This information is then used to adjust all injections on that fuel injector for a correct fuel delivery. If the absolute energizing time observed for the test injection to yield the expected acceleration exceeds minimum or maximum limits, a DTC sets.