A method for predicting a future camshaft position includes approximating a regulating circuit or a part of a regulating circuit that includes at least an adjusting device by a transfer function, and ascertaining a future camshaft position on the basis of the transfer function. An engine control unit is also provided.

Various embodiments include a method for detecting deviations occurring in the valve drive of an internal combustion engine comprising: measuring dynamic pressure oscillations of intake air in an air intake tract of respective internal combustion engine during operation; calculating an inlet valve stroke phase difference and/or an outlet valve stroke phase difference based on the measured dynamic pressure oscillation; calculating a valve stroke phase deviation value with respect to a valve stroke phase reference value based on the calculated phase difference; and calculating a first valve drive deviation value based on the valve stroke phase deviation value.

Various embodiments include a method for identifying valve stroke phase differences during operation comprising: measuring dynamic pressure oscillations in the air intake tract; generating a corresponding signal; acquiring a crankshaft phase angle; acquiring the phase position and the amplitude of a signal frequency of the oscillations based on the pressure oscillation using discrete Fourier transformation; acquiring a line of an equal phase position and of equal amplitude of the signal frequency reflecting the inlet and the outlet stroke phase difference using reference lines; acquiring a common intersection point of a line of equal phase position and a line of equal amplitude by projection into a common plane; and determining the stroke phase differences and from the common intersection point.

Various embodiments include a method for identifying an inlet and an outlet valve stroke phase difference comprising: measuring pressure oscillations during operation; generating a corresponding signal; determining a corresponding crankshaft phase angle; applying a discrete Fourier transformation to the pressure signal to determine amplitudes of selected frequencies in relation to the crankshaft phase angle; determining lines of equal amplitudes of the frequencies based on the amplitudes depending on the phase differences using reference lines; determining an intersection of the lines by projection into a common plane; and determining the inlet valve stroke phase difference and the outlet valve stroke phase difference from the determined common intersection point of the lines of equal amplitudes of the selected signal frequencies.

A variable valve system including a crank angle sensor that measures a rotation angle of a crankshaft, a cam angle sensor that measures a rotation angle of a camshaft coupled to the crankshaft and which opens and closes valves, and a controller that controls the internal combustion engine. At least one of the crank angle sensor or the cam angle sensor is configured as an absolute angle sensor that measures an absolute rotation angle and outputs a voltage signal corresponding to this rotation angle. The controller is configured to perform a correction operation that corrects a rotation angle value calculated based on the voltage signal.

A method of determining a condition of a component (e.g., valves) of an engine having a manifold air pressure sensor during a cold test includes providing pressurized air to an intake of the engine. The method includes rotating a crankshaft of the engine. The method includes measuring pressures with the manifold air pressure sensor as a function of crankshaft rotational position. The method includes comparing the pressures with a predetermined baseline. The method includes indicating a condition of the component based on the comparison of the pressures with the baseline.

Methods and systems are provided for diagnosing a cylinder valve deactivation mechanism in an engine system having cam-actuated valves. Movement of a latch pin of the deactivation mechanism is inferred from an induction current generated by a solenoid coupled to the latch pin, and the inferred movement is used to diagnose operation of cylinder valve deactivation mechanism. The inferred movement and a profile of the induction current is also used to estimate camshaft and crankshaft timing for improved cylinder fuel delivery in the absence of a camshaft sensor.

A method for ascertaining a valve position of a valve of an internal combustion engine having a multiplicity of valves. The method includes illuminating a combustion chamber of the internal combustion engine, detecting light emerging from the illuminated combustion chamber on a side, averted from the combustion chamber, of the valve for ascertainment, and determining the valve position of the valve for ascertainment by way of the detected light.

A method of determining a sliding camshaft actuator pin position based on engine crankshaft angle includes commanding a sliding camshaft actuator to perform a valve step shift, and monitoring an actuator's pin position during the valve step shift command. At least one crank angle is measured when the actuator pin position reaches or exceeds at least one predetermined pin position threshold and at least one remedial action is performed when the actuator pin position does not correlate to the at least one measured crank angle.

Methods and systems are described for an engine with a cam torque actuated variable cam timing phaser. Phaser positioning control is improved by reducing inaccuracies resulting from inadvertent spool valve and/or phaser movement when the spool valve is commanded between regions. In addition, improved spool valve mapping is used to render phaser commands more consistent and robust.