Abstract: Methods and apparatus for operating an internal combustion engine are provided. The engine has an engine block defining a cylinder accommodating a reciprocating piston coupled to rotate a crankshaft, a fuel injector for injecting fuel inside the cylinder, and a crank position sensor positioned proximal to the crankshaft. A method includes commanding the fuel injector to perform a test fuel injection with a predetermined energizing time and using the crank position sensor to determine a crankshaft acceleration signal during the test fuel injection. The crankshaft acceleration signal is filtered and a value of an amplitude of a fundamental frequency component of the filtered crankshaft acceleration signal is determined. A correction factor of the predetermined energizing time is determined based on a difference between the determined value of the amplitude and a preset value thereof. The correction factor is used to correct an energizing time of subsequent fuel injections.

Abstract: A method for adjusting an oxygen sensor measurement within an exhaust gas feedstream output from an internal combustion engine based on humidity includes monitoring relative humidity of ambient air obtained from a humidity sensor. Specific humidity at the oxygen sensor is modeled based on the relative humidity. The oxygen sensor measurement is adjusted based on the modeled specific humidity at the oxygen sensor.

Abstract: A method is provided to diagnose a fault in a fuel injection system of an internal combustion engine. The method includes, but is not limited to commanding an injection pulse for injecting a test quantity of fuel into an engine cylinder, determining the torque released to an engine crankshaft due to the injection pulse, calculating the difference between this released torque and an expected value for the torque, and of detecting a fault in the fuel injection system if the difference exceeds a threshold.

Abstract: A method for adjusting an oxygen sensor measurement within an exhaust gas feedstream output from an internal combustion engine based on humidity includes monitoring relative humidity of ambient air obtained from a humidity sensor. Specific humidity at the oxygen sensor is modeled based on the relative humidity. The oxygen sensor measurement is adjusted based on the modeled specific humidity at the oxygen sensor.

Abstract: A method is provided that includes, but is not limited to acquiring the crankshaft speed signal while one fuel injector is energized for a determined period of time (ET) in which all the other fuel injectors are de-energized, processing the acquired crankshaft speed signal so as to obtain signals or data (A) representative of the amplitude of a predetermined harmonic component of the crankshaft speed signal, and calculating the power (RMS/MS) of said harmonic component, and assuming the calculated power value (C) as an estimation of the quantity of fuel actually injected by the energized injector in said predetermined period of time (ET).

Abstract: A method is provided to diagnose a fault in a fuel injection system of an internal combustion engine. The method includes, but is not limited to commanding an injection pulse for injecting a test quantity of fuel into an engine cylinder, determining the torque released to an engine crankshaft due to the injection pulse, calculating the difference between this released torque and an expected value for the torque, and of detecting a fault in the fuel injection system if the difference exceeds a threshold.

Abstract: A method is provided for correcting the cylinder unbalancing in an internal combustion engine.

Abstract: A method is provided for the determination of the actual quantity of fuel injected in an internal combustion engine, in particular a Diesel engine. The engine includes, but is not limited to an inlet line and an exhaust line, at least one cylinder and at least an injector for each of the cylinders. The method includes, but is not limited to, during a fuel cut-off state of the engine, at least an injection into one of the cylinders of a nominal fuel test quantity and, in correlation to the test injection, a determination of the air flow quantity MAF at the inlet of the engine, a determination of the parameter ? in the exhaust line of the engine, and a calculation of the actual quantity of fuel Qfuel injected in the test injection using the Electronic Control Unit of the engine.

Abstract: A method is provided that includes, but is not limited to acquiring the crankshaft speed signal while one fuel injector is energized for a determined period of time (ET) in which all the other fuel injectors are de-energized, processing the acquired crankshaft speed signal so as to obtain signals or data (A) representative of the amplitude of a predetermined harmonic component of the crankshaft speed signal, and calculating the power (RMS/MS) of said harmonic component, and assuming the calculated power value (C) as an estimation of the quantity of fuel actually injected by the energized injector in said predetermined period of time (ET).