Methods and systems are provided for adjusting an ignition timing of an internal combustion engine responsive to a biasing force of a pressure-reactive piston. In one example, an engine may include a pressure-reactive piston having a top wall biased away from a piston base by a pressure of gas contained within the base. An ignition timing of a combustion chamber including the piston is adjusted responsive to an estimated biasing force of the gas against the top wall.

An ignition device of an engine includes a control unit and an igniter including an ignition coil having a primary and a secondary winding. Supply and stop of a current to the primary winding are performed based on the ignition signal to generate high voltage in the secondary winding thereby to cause a spark to a spark plug provided for a cylinder of the engine. The control unit includes an engine speed variation detector that detects an engine speed variation. The control unit determines a misfire occurs in the cylinder when the engine speed variation is at or higher than a first threshold and smaller than a second threshold that is greater than the first threshold. The control unit determines an abnormality occurs in the igniter in the cylinder when the engine speed variation is at or higher than the second threshold.

Approaches for controlling dwell time in the ignition system of an internal combustion engine are provided. In one example, a method may include adjusting dwell based on engine operating conditions and further adjusting dwell in a manner proportional to existent spark plug conditions. By constantly assessing spark plug condition during operating of the internal combustion engine, premature wear of the spark plug may be prevented leading to an extension in the service life of spark plug and other ignition system components.

A control system for an internal combustion engine, which is capable of controlling fuel injection valves while causing valve-closing delay time periods, which occur with the valves actually mounted on the engine, to be reflected thereon, thereby making it possible to improve exhaust emission characteristics and fuel economy performance. The ECU of the control system performs initial value-specific control in fuel injection control and ignition timing control, such that initial value acquisition conditions are satisfied, so as to calculate the initial values of the valve-closing delay time periods when the initial value acquisition conditions are satisfied. When normal-time control is performed, the valve-opening time periods of the valves are calculated using the initial values of the valve-opening time periods, and the valves are controlled to be open over the valve-opening time periods.

A method and a controller for controlling spark timing in a cold start condition for an engine in a vehicle propulsion system. The method includes determining whether the engine is in a cold start condition, and advancing spark timing before top dead center in a combustion cycle such that combustion heat is primarily received by a surface in a combustion chamber in the engine if the engine is in a cold start condition.

Methods and systems are provided for adjusting an ignition timing of an internal combustion engine responsive to a biasing force of a pressure-reactive piston. In one example, an engine may include a pressure-reactive piston having a top wall biased away from a piston base by a pressure of gas contained within the base. An ignition timing of a combustion chamber including the piston is adjusted responsive to an estimated biasing force of the gas against the top wall.

An ignition device for an internal combustion engine includes an ignition plug including a discharge portion facing a vicinity of an exhaust port of a combustion chamber of the internal combustion engine, a drive unit configured to allow nonequilibrium plasma discharge to occur in the discharge portion by applying a drive voltage to the ignition plug, and an electronic control unit configured to allow the nonequilibrium plasma discharge to occur in the discharge portion by applying the drive voltage from the drive unit to the ignition plug in a first predetermined period when the exhaust gas control catalyst is in a warm-up state, the first predetermined period being a predetermined period after initiation of opening of an exhaust valve and a period in which a blowdown phenomenon of exhaust gas occurs.

Systems and methods are provided for varying a compression ratio in an engine having a pressure reactive piston. The pressure reactive piston may include a piston crown, and a spring positioned within the piston crown, wherein the spring includes a first ring, a second ring comprising a plurality of apertures, a rolling element positioned within each of the plurality of apertures, and a third ring. The first ring, the second ring, and the third ring of the spring may be arranged concentrically and the second ring may be positioned between the first ring and the third ring.

A control system for an internal combustion engine, which is capable of controlling fuel injection valves while causing valve-closing delay time periods, which occur with the valves actually mounted on the engine, to be reflected thereon, thereby making it possible to improve exhaust emission characteristics and fuel economy performance. The ECU of the control system performs initial value-specific control in fuel injection control and ignition timing control, such that initial value acquisition conditions are satisfied, so as to calculate the initial values of the valve-closing delay time periods when the initial value acquisition conditions are satisfied. When normal-time control is performed, the valve-opening time periods of the valves are calculated using the initial values of the valve-opening time periods, and the valves are controlled to be open over the valve-opening time periods.

An internal combustion engine system includes: an in-cylinder pressure sensor; a crank angle sensor; and a seal portion that seals a space between an outer face of a housing and a wall surface of a cylinder head. A slope that is a ratio of the amount of decrease in a heat release amount relative to the amount of increase in a crank angle is calculated in a period during an expansion stroke from a combustion end point until an opening timing of an exhaust valve. The existence or nonexistence of an abnormality in the sealing function of the seal portion is determined based on whether or not a ratio of the amount of decrease in the slope to the amount of increase in an engine speed is greater than a threshold value.