A method and system are provided with which it is possible to detect non-firing and untimely firing events in internal combustion and, if necessary, the temperature of the gas in the exhaust gas pipe. This is performed in general by measuring the speed of sound and determining the phase angle between the sender and receiver either arranged on different sides of the exhaust gas pipe or on the same side of the exhaust gas pipe. The receiver, depending on the measurement principle, can include one, two, or in special applications three receivers. Additionally, if necessary, it is possible to suppress the structure-borne sound influence on a speed of sound measurement with low cost and high stability.

An internal combustion engine (1) includes: an exhaust gas recirculation unit equipped with an exhaust gas recirculation control valve (9); a crank angle sensor (11) that detects an indicated mean effective pressure fluctuation rate (cPi) as an indicator of combustion stability of the internal combustion engine (1); and a controller (10) that corrects the EGR rate of the exhaust gas recirculation unit based on the combustion stability. The controller (10) is configured to: increase-correct the EGR rate by a predetermined amount when the state where the indicated mean effective pressure fluctuation rate (cPi) is lower than a threshold value continues for a predetermined number of cycles; and decrease-correct the EGR rate by a predetermined amount immediately when the indicated mean effective pressure fluctuation rate (cPi) is higher than or equal to the threshold value.

Methods and systems are provided for a vehicle engine having a pre-chamber ignition system. In one example, a method may include adjusting one or more of an air injection amount and a fuel injection amount to a pre-chamber of an engine based on an air injection offset and a fuel injection offset learned while discontinuing fueling to cylinders of the engine and reducing air flow through the engine. In this way, air and fuel may be more accurately provided to the pre-chamber, thereby decreasing an occurrence of pre-chamber misfire.

A CPU stops combustion control of Cylinder #1 in order to perform a regeneration process of a GPF and performs a regeneration process of causing an air-fuel ratio of an air-fuel mixture in Cylinders #2 to #4 to be richer. When it is determined that a misfire has occurred because a misfire rate when the regeneration process is not being performed is equal to or greater than a predetermined value, the CPU determines that an internal combustion engine has returned to a normal state based on the premise that the misfire rate when the regeneration process is not being performed decreases.

To provide a controller for internal combustion engine which suppresses that estimation of the combustion state is performed based on the angle information on which the component due to the torsional vibration is superimposed, when the torsional vibration occurs in the crankshaft. A controller for internal combustion engine determines whether a torsional vibration occurs in a crankshaft based on an angle period; calculates a gas pressure torque in burning based on a crank angle acceleration which is calculated based on the angle period; estimates a combustion state of an internal combustion engine based on the gas pressure torque in burning; and stops estimation of the combustion state, when it is determined that the torsional vibration occurred.

A straddled vehicle engine unit including an internal combustion engine and a misfire detection device. The internal combustion engine has a crankshaft, and a crank angle signal output unit that periodically outputs a crank angle signal in accordance with rotation of the crankshaft. The internal combustion engine is configured to repeat at least two kinds of strokes on a cycle of every 720-degree rotation of the crankshaft. The misfire detection device includes a crankshaft rotation speed fluctuation physical quantity acquisition unit configured to acquire a physical quantity related to an amount of fluctuation in a rotation speed of the crankshaft in one kind of stroke, out of the at least two kinds of strokes, based on the crank angle signal from the crank angle signal output unit, and a misfire determination unit configured to perform a misfire determination in response to each acquisition of the crankshaft rotation speed fluctuation physical quantity.

A system includes a reciprocating piston engine configured to output torque to drive a load. The system includes an engine speed sensor operatively coupled with the engine and configured to output an engine speed signal. The system includes an electronic control system operatively coupled with the powertrain. The electronic control system is configured to determine an engine acceleration in response to the engine speed signal, and detect a misfire of the engine in response to the engine acceleration.

A system for detecting and controlling misfire and/or AFR imbalance conditions in cylinders of an internal combustion engine having a plurality of cylinders is disclosed.

A reignition processing device for a gas engine for executing a reignition process of a cylinder during operation of a gas engine having multiple cylinders is provided with: an execution permission unit configured to, when at least one of the cylinders misfires, perform permission determination whether to execute the reignition process of the misfiring cylinder, on the basis of a damage diagnosis result based on an in-cylinder pressure of the misfiring cylinder, presence or absence of abnormality in a control device which performs combustion control and combustion diagnosis of the gas engine, an operational history related to the misfiring cylinder, and an operational state of the gas engine; and a reignition execution unit configured to execute the reignition process of the misfiring cylinder that is permitted by the permission determination to execute the reignition process.

To provide a controller for internal combustion engine which suppresses that estimation of the combustion state is performed based on the angle information on which the component due to the torsional vibration is superimposed, when the torsional vibration occurs in the crankshaft. A controller for internal combustion engine determines whether a torsional vibration occurs in a crankshaft based on an angle period; calculates a gas pressure torque in burning based on a crank angle acceleration which is calculated based on the angle period; estimates a combustion state of an internal combustion engine based on the gas pressure torque in burning; and stops estimation of the combustion state, when it is determined that the torsional vibration occurred.