A method includes receiving a signal indicative of a change in an air-fuel ratio (AFR) for a mixture of air and fuel entering a first combustion chamber of a combustion engine, advancing firing timing of the first combustion chamber, receiving, from a knock sensor, a knock signal indicating that the combustion engine has begun to knock, determining a knock margin of the first combustion chamber based on when the combustion engine begins to knock, and storing the knock margin as associated with the knock timing and the AFR.

In a spark-ignition internal combustion engine having multiple cylinders, successive segment time periods assigned to the individual cylinders during working strokes thereof, and subsequently irregular running values are determined from the segment time periods. In a predefined speed range of the engine, the irregular running values of the cylinders are compared with a predefined threshold, and suspected auto-ignition for a first cylinder is detected if the irregular running value of a second cylinder located before the first cylinder in terms of timing of the ignition sequence undershoots the threshold. Fuel to the first cylinder suspected of auto-ignition is interrupted for a predefined number of cycles, and the fuel interruption influence on the irregular running values of the second cylinder during the cycles is detected. The suspected auto-ignition of the first cylinder is either confirmed or rejected based on the irregular running values occurring at the second cylinder.

A drive train abnormality determination device for a straddled vehicle that includes a drive train having a rotator. The drive train abnormality determination device includes an angle signal output unit that periodically outputs an angle signal in accordance with rotation of the rotator, a rotator rotation speed fluctuation physical quantity acquisition unit that acquires a quantity related to a fluctuation in a rotation speed of the rotator, based on the angle signal from the angle signal output unit, a rough road determination unit that determines whether a distribution state or pattern satisfies a predetermined rough road condition, a continuity determination unit that determines whether the rough road condition is continuously satisfied, and a drive train abnormality determination unit that determines, responsive to a determination by the continuity determination unit that the rough road condition is continuously satisfied, that the drive train has an abnormality in its functioning.

The control apparatus operates an engine water temperature adjustment apparatus so that the temperature of cooling water that passes through an engine head enters a first temperature region in a lean mode, and operates the engine water temperature adjustment apparatus so that the temperature of the cooling water enters a second temperature region that is lower than the first temperature region in a stoichiometric mode. When knocking is detected after switching is started from the stoichiometric mode to the lean mode, the control apparatus performs any one of a first operation to operate a variable valve apparatus so as to retard the closing timing of an intake valve, a second operation to operate an oil jet apparatus so as to increase an oil jet amount, and a third operation to operate an EGR apparatus so as to increase an EGR amount.

A misfire detecting system for an engine of a vehicle that detects a misfire of the engine is provided. The system includes a sensor configured to detect a wheel speed of the vehicle, a load adjustment device configured to adjust a load of the engine, and a processor. The processor determines whether a wheel slip has occurred by examining whether a change rate of the wheel speed is equal to or greater than a determination reference value, when determining whether the wheel slip has occurred, limits a determination of the misfire of the engine by adjusting the determination reference value higher or lower based on corresponding increases or decreases in a requested load, by applying the adjusted determination reference value, determines that wheel slip has occurred, and based on the wheel slip determination, determines that the misfire has occurred.

A CPU substitutes a difference between a crank-side speed that is a rotation speed of a crankshaft and a downstream-side speed that is a speed of a portion, opposite from the crankshaft, in a damper into a differential speed. The CPU calculates a torsion angle through a process of integrating the differential speed. The CPU calculates a torsion speed component that is a speed component of the crankshaft due to torsion of the damper based on a process of integrating a value obtained by multiplying the torsion angle by an elastic modulus, and calculates a time that is a variable indicating a speed of the crankshaft, used to determine a misfire, based on the torsion speed component. The CPU subtracts a value obtained by subtracting an output value of the integrating process, applied to a finite response low-pass filter process, from the output value.

A CPU substitutes a difference between a crank-side speed that is a rotation speed of a crankshaft and a downstream-side speed that is a speed of a portion, opposite from the crankshaft, in a damper into a differential speed. The CPU calculates a torsion speed component that is a speed component of the crankshaft due to torsion of the damper based on a physical model of which an input is the differential speed, and calculates a time that is a variable indicating a speed of the crankshaft, used to determine a misfire, based on the torsion speed component. The CPU delays acquisition time of the downstream-side speed used to calculate the differential speed, with respect to acquisition time of the crank-side speed according to the rotation speed of the crankshaft.

A method for avoiding pre-ignitions during the operation of an internal combustion engine includes measuring a noise level of a combustion process using an acceleration sensor. An amplitude an amplitude of the measured noise level is measured to detect pre-ignitions. If, in the analysis, the measured noise level of a combustion cycle exceeds a limiting value n times, a safety operating mode of the internal combustion engine for reducing an effecting compression in the combustion chamber is activated. The safety operating mode is maintained if exceeding of the amplitude limiting value is also detected in subsequent combustion cycles of the internal combustion engine.

A control apparatus for an internal combustion engine, includes circuitry. The circuitry is configured to control a ratio of an amount of low octane number fuel to be supplied to a cylinder to a total amount of the low octane number fuel and a high octane number fuel to be supplied to the cylinder in order to control an overall octane number of fuel to be supplied to the cylinder. The high octane number fuel has a second octane number higher than a first octane number of the low octane number fuel. The circuitry is configured to calculate a maximum octane number of the fuel to be supplied into the cylinder. The circuitry is configured to restrict a power generated by the internal combustion engine based on the maximum octane number.

A split cycle internal combustion engine comprising a compression cylinder accommodating a compression piston; a combustion cylinder accommodating a combustion piston; a crossover passage between the compression cylinder and the combustion cylinder arranged to provide working fluid to the combustion cylinder; a controller arranged to determine a peak temperature of combustion in the combustion cylinder based on a received indication of a peak temperature of combustion in the combustion cylinder; and a coolant system arranged to regulate a temperature of the working fluid supplied to the combustion cylinder; wherein, in response to determining that the peak temperature of combustion exceeds a selected threshold, the controller is configured to control the coolant system to regulate the temperature of the working fluid supplied to the combustion cylinder so that a peak temperature of combustion in the combustion cylinder is less than the selected threshold.