An internal combustion engine control device 110 includes a mass flux calculation unit F2, an opening area calculation unit F3, an effective opening area calculation unit F4, and a passing gas flow rate calculation unit F5. The mass flux calculation unit F2 calculates a mass flux MF of gas passing through a throttle valve 125 based on an upstream gas temperature Tu, an upstream gas pressure Pu, and a downstream gas pressure Pd of the throttle valve 125. The opening area calculation unit F3 calculates an opening area A of the throttle valve 125 based on an opening degree θ of the throttle valve 125. The effective opening area calculation unit F4 calculates an effective opening area EA of the throttle valve 125 based on the upstream gas pressure Pu, the downstream gas pressure Pd, the opening degree θ, and the opening area A. The passing gas flow rate calculation unit F5 calculates a gas flow rate GF passing through the throttle valve 125 based on the mass flux MF and the effective opening area EA.

Methods and systems are provided for reducing a spark plug soot load and a combustion chamber soot load by controlling spark plug timing while injecting water or washer fluid. In one example, water or washer fluid is injected during a torque reduction while advancing spark timing so as to provide at least a portion of the torque reduction while opportunistically cleaning soot from the spark plug and combustion chamber. By reducing spark plug soot load, misfire occurrence is reduced, while pre-ignition occurrence is reduced by decarbonizing the combustion chamber.

Methods and systems are provided for reducing a spark plug soot load and a combustion chamber soot load by controlling spark plug timing while injecting water or washer fluid. In one example, water or washer fluid is injected during a torque reduction while advancing spark timing so as to provide at least a portion of the torque reduction while opportunistically cleaning soot from the spark plug and combustion chamber. By reducing spark plug soot load, misfire occurrence is reduced, while pre-ignition occurrence is reduced by decarbonizing the combustion chamber.

A control device for an internal combustion engine is provided. The internal combustion engine includes a cylinder, an in-cylinder pressure sensor, a fuel injection valve, and an alcohol concentration sensor. The control device includes an electronic control unit. The electronic control unit is configured to: carry out learning of fuel properties with the fuel injected from the fuel injection valve as a target; calculate a combustion speed parameter, showing a combustion speed, within the cylinder, of the fuel that is a learning target of the fuel properties, on a basis of the in-cylinder pressure; and determine that water is included in the fuel when the capacitance of the fuel detected by the alcohol concentration sensor is larger than a preset first threshold, and when the combustion speed of the fuel within the cylinder is smaller than a preset second threshold.

Methods and systems include determining a cylinder air-fuel ratio imbalance in a multi-cylinder engine. In one example, the method may include sequentially firing an engine cylinder to provide an expected air-fuel deviation and learning cylinder air-fuel ratio imbalance based on an error between an actual air-fuel ratio deviation from a maximum lean air-fuel ratio relative to an expected air-fuel deviation during a deceleration fuel shut-off event.

Methods and systems include determining a cylinder air-fuel ratio imbalance in a multi-cylinder engine. In one example, the method may include sequentially firing an engine cylinder to provide an expected air-fuel deviation and learning cylinder air-fuel ratio imbalance based on an error between an actual air-fuel ratio deviation from a maximum lean air-fuel ratio relative to an expected air-fuel deviation during a deceleration fuel shut-off event.

Systems and methods for operating an engine with deactivating and non-deactivating valves are presented. In one example, a position of one or more volumetric efficiency control devices is changed in response to a request to deactivate one or more engine cylinders while at the same time the engine central throttle is adjusted. Spark timing may also be adjusted if engine air flow deviates from a desired engine air flow.

Systems and methods for operating an engine with deactivating and non-deactivating valves are presented. In one example, a position of one or more volumetric efficiency control devices is changed in response to a request to deactivate one or more engine cylinders while at the same time the engine central throttle is adjusted. Spark timing may also be adjusted if engine air flow deviates from a desired engine air flow.

Systems and methods for operating an engine with a plurality of deactivating valves for deactivating engine cylinders are presented. In one example, a plurality of different cylinder operating modes may be available to operate the engine. Engine fuel consumption in each of the plurality of different cylinder operating modes is estimated and the engine may be operated in the cylinder mode that provides greatest fuel efficiency.

Systems and methods for operating an engine with a plurality of deactivating valves for deactivating engine cylinders are presented. In one example, a plurality of different cylinder operating modes may be available to operate the engine. Engine fuel consumption in each of the plurality of different cylinder operating modes is estimated and the engine may be operated in the cylinder mode that provides greatest fuel efficiency.