An engine system for a vessel propulsion device includes an engine including an intake amount adjusting unit and an ignition plug, and configured to generate a drive force for the vessel propulsion device. The engine system includes an ignition timing control unit, a knocking detecting unit, a knocking retard control unit that retards the ignition timing of the ignition plug by a unit retard amount when the knocking detecting unit detects knocking, an abnormality judging unit that, when a state where the knocking detecting unit detects knocking at intervals within a predetermined time continues, judges that an abnormality has occurred based on a continued state of knocking detection, and an intake amount limiting unit that limits the intake amount of the engine based on judgment of an abnormality made by the abnormality judging unit.

A method for ignition control in a combustion chamber of an internal combustion engine by means of acquiring an electric signal relating to ionizing currents emitted in said combustion chamber, comprising a step of detecting a substantially stepped trend of said electric signal and a consequent step of inhibiting a corrective action of an ignition advance and/or of a fuel injection limitation curve in the combustion chamber.

The control device (50) operates to: calculate the ignition timing of each cylinder (101) of an engine (100) based on whether or not knocking is occurring; set, as a reference ignition timing, the ignition timing of any of the cylinders (101) for which the ignition timing is on the advanced angle side relative to the most retarded angle ignition timing on the most retarded angle side and on the retarded angle side relative to the most advanced angle ignition timing on the most advanced angle side; set an allowable timing difference range that is a range of an allowable timing difference with reference to the reference ignition timing; and when determining that the ignition timing of a cylinder (101) falls outside the allowable timing difference range, correct the ignition timing so that the timing difference with respect to the reference ignition timing falls within the allowable timing difference range.

A method for ignition control in a combustion chamber of an internal combustion engine by means of acquiring an electric signal relating to ionizing currents emitted in said combustion chamber, comprising a step of detecting a substantially stepped trend of said electric signal and a consequent step of inhibiting a corrective action of an ignition advance and/or of a fuel injection limitation curve in the combustion chamber.

Methods and systems are provided for determining engine knock sensor degradation. In one example, a method may include sending an excitation signal to an actuator to generate vibrations in the absence of engine combustion, and determining engine knock sensor degradation by comparing the knock sensor output with the excitation signal.

Methods and systems are provided for rationalizing an engine knock sensor. In one example, a method may include, responsive to an indication of an engine knock event, correlating an output of the engine knock sensor with an output of an on-board microphone to determine degradation of the engine knock sensor. By rationalizing the engine knock sensor against another on-board sensor (e.g., the on-board microphone), diagnostic fidelity may be increased.

Methods and systems are provided for rationalizing an engine knock sensor. In one example, a method may include, responsive to an indication of an engine knock event, correlating an output of the engine knock sensor with an output of an on-board microphone to determine degradation of the engine knock sensor. By rationalizing the engine knock sensor against another on-board sensor (e.g., the on-board microphone), diagnostic fidelity may be increased.

A method for monitoring an operation of an internal combustion engine includes the steps of: detecting, during the operation of the internal combustion engine, an acoustic signal, at least partially, during a closing process of a gas exchange valve of the internal combustion engine; evaluating, based on the acoustic signal which is detected, at least one functional state of the internal combustion engine; and selecting the at least one functional state of the internal combustion engine from a group consisting of a state of the gas exchange valve and a state of a structure-borne noise sensor used to detect the acoustic signal.

An ignition timing control apparatus for an internal combustion engine includes an electronic control unit configured to i) perform determination as to whether knocking has occurred in the engine; ii) update a first learning value and a second learning value such that the ignition timing is retarded when determining that knocking has occurred; and iii) derive, as a required ignition timing, a timing obtained by retarding a base ignition timing based on the first and second learning values. The electronic control unit is configured to update the second learning value within a range in which an update amount of the second learning value within a prescribed period set in advance does not exceed a prescribed amount, when updating the second learning value.

Methods and systems are provided for diagnosing a knock sensor of an engine system by actively inducing knock in an engine cylinder. A laser ignition device is operated in an engine cylinder located closest to the knock sensor while the engine is at rest and with the cylinder parked with an intake valve and an exhaust valve closed to generate and trap heat in the cylinder. Spark timing is advanced in the cylinder on the subsequent restart, which in combination with the trapped heat induces knock, and elicits a response from a functional knock sensor.