An individual cylinder air-fuel ratio estimation of estimating an air-fuel ratio of an individual cylinder is performed on a sensed value of an air-fuel ratio sensor set in an exhaust gas collection part of an engine, and an individual cylinder air-fuel ratio control of controlling the air-fuel ratio of the individual cylinder is performed in such a way that a variation in the air-fuel ratio between the cylinders becomes small on the basis of an estimated air-fuel ratio of the individual cylinder. Further, it is determined whether or not a misfire of the engine is caused and when it is determined that the misfire of the engine is caused, the individual cylinder air-fuel ratio estimation and the individual cylinder air-fuel ratio control are stopped and an individual cylinder correction value by the individual cylinder air-fuel ratio control is reset. In this way, it is possible to avoid the individual cylinder air-fuel ratio control from being performed continuously as usual in a state where the air-fuel ratio of the individual cylinder cannot be controlled correctly due to the effect of the misfire.

Methods and systems are provided for regulating a flow of fuel vapors from a fuel tank to an engine during an engine start. In one example, a method may comprise prior to a cold start of an engine: sealing a fuel tank from an evaporative emissions control system and an air intake of the engine, operating a fuel pump of the fuel tank to generate vapors in the fuel tank, and in response to fuel vapor levels in the fuel tank reaching a threshold, initiating cylinder combustion and flowing fuel vapors from the fuel tank to an intake manifold of the engine. The method may further comprise providing liquid fuel to the engine to initiate cylinder combustion.

An engine control system is a system configured to selectively switch between first fuel and second fuel and perform an operation control of a single engine, including: a sensor configured to detect an oxygen concentration of an exhaust gas that is exhausted from the engine; and a control device configured to perform an air-fuel ratio feedback control such that an air-fuel ratio becomes a target air-fuel ratio based on an output signal of the sensor, wherein the control device calculates a correction coefficient of an air-fuel ratio feedback control during an operation with the second fuel, and further stores a fuel composition correction coefficient that is a value in a predetermined range and corrects a difference between the calculated correction coefficient and a targeted correction coefficient arising from a change in composition of the second fuel.

Systems and methods for improving emissions of an internal combustion engine are presented. In one example, engine crankshaft acceleration is a basis for estimating engine air-fuel ratio during engine starting when output of an oxygen sensor may be unavailable. An actual engine air-fuel ratio may be adjusted in response to the estimated engine air-fuel ratio.

Methods and systems are provided for regulating a flow of fuel vapors from a fuel tank to an engine during an engine start. In one example, a method may comprise prior to a cold start of an engine: sealing a fuel tank from an evaporative emissions control system and an air intake of the engine, operating a fuel pump of the fuel tank to generate vapors in the fuel tank, and in response to fuel vapor levels in the fuel tank reaching a threshold, initiating cylinder combustion and flowing fuel vapors from the fuel tank to an intake manifold of the engine. The method may further comprise providing liquid fuel to the engine to initiate cylinder combustion.

An engine device includes a main throttle valve disposed at a portion where an outlet of a supercharger and an inlet of an intercooler are coupled to each other, an exhaust bypass flow path configured to couple an outlet of an exhaust manifold to an exhaust outlet of the supercharger, an exhaust bypass valve disposed in the exhaust bypass flow path, an air supply bypass flow path configured to bypass a compressor of the supercharger, and an air supply bypass valve disposed in the air supply bypass flow path. Within a low load range of a load on the engine device, when the load is lower than a predetermined load, feedback control is performed on the main throttle valve, and when the load is higher than the predetermined load, map control based on a data table is performed on the main throttle valve.

A control apparatus for an internal combustion engine is configured to: calculate measured data of MFB using an output signal of an in-cylinder pressure sensor after performing a first low-pass filtering; execute engine control based on the measured value of a specified fraction combustion point that is calculated based on the measured data of MFB; and prohibit the engine control when the first correlation index value is less than a first determination value and a first correlation degree is lower than a first degree.

Systems and methods for improving emissions of an internal combustion engine are presented. In one example, engine crankshaft acceleration is a basis for estimating engine air-fuel ratio during engine starting when output of an oxygen sensor may be unavailable. An actual engine air-fuel ratio may be adjusted in response to the estimated engine air-fuel ratio.

A control apparatus for an internal combustion engine is configured to: calculate measured data of MFB in synchrony with crank angle based on in-cylinder pressure detected by an in-cylinder pressure sensor; execute engine control based on a measured value of a specified fraction combustion point that is calculated based on the measured data of MFB; calculate a first correlation index value for MFB and a second correlation index value for dMFB/d; and suspend the engine control when the first correlation index value is less than a first determination value and the second correlation index value is greater than or equal to a second determination value.