A control system for a compression ignition engine is provided, which includes a combustion chamber, a throttle valve, an injector, an ignition plug, a sensor, and a controller. A changing module of the controller outputs a signal to the throttle valve so that an air amount increases more than before a demand of changing from a first mode to a second mode, and outputs to the injector a signal to increase a fuel amount according to the air amount increase so that an air-fuel ratio of mixture gas becomes at or substantially at a stoichiometric air-fuel ratio, and outputs to the ignition plug a signal to retard an ignition timing so that an engine torque increase caused by the fuel amount increase is reduced. The changing module reduces the retarding of the ignition timing when the ignition timing is determined to have reached a retard limit.

A method of estimating antiknock properties of a multi-fuel injection internal combustion engine includes: acquiring a first antiknock property-correlated parameter value while only a first fuel having a low octane rating is injected in a first load range; estimating a first antiknock property of the first fuel based on the first antiknock property-correlated parameter value; acquiring a second antiknock property-correlated parameter value while the first fuel and a second fuel which has a high octane rating higher than the low octane rating are injected in a second load range higher than the first load range; and estimating a second antiknock property of the second fuel based on the second antiknock property-correlated parameter value and the first antiknock property of the first fuel.

A method of operating an internal combustion engine of a vehicle is provided to maintain cylinder balance. A first operating mode corresponding to a steady state operation of the internal combustion engine is differentiated from a second operating mode corresponding to a transient operation of the internal combustion engine based upon a first operating parameter of the internal combustion engine. In the first operating mode, a first control strategy provides cylinder balance. In the second operating mode, a second control strategy, different than the first control strategy, provides cylinder balance. The second control strategy utilizes a dynamic factor based upon a second operating parameter of the internal combustion engine.

The present invention relates to a method of controlling a positive-ignition internal combustion engine, in which the ignition advance is controlled (CON) by means of an estimation (EST) of the distribution of the knock measurements (MEAS). This estimation (EST) makes it possible to determine, for these measurements (MEAS), a confidence interval (q.sub.min, q.sub.max) of a predetermined quantile of the distribution of the knock measurements (MEAS).

A method of operating an internal combustion engine of a vehicle is provided to maintain cylinder balance. A first operating mode corresponding to a steady state operation of the internal combustion engine is differentiated from a second operating mode corresponding to a transient operation of the internal combustion engine based upon a first operating parameter of the internal combustion engine. In the first operating mode, a first control strategy provides cylinder balance. In the second operating mode, a second control strategy, different than the first control strategy, provides cylinder balance. The second control strategy utilizes a dynamic factor based upon a second operating parameter of the internal combustion engine.

When the air fuel ratio dither control is carried out, an air fuel ratio of a mixture in each of one or more lean cylinders and one or more rich cylinders is controlled in a feedback manner based on an average value of a detected value of an air fuel ratio sensor, so that an average value of an air fuel ratio of exhaust gas flowing into the three-way catalyst becomes a predetermined target exhaust gas air fuel ratio. At this time, the air fuel ratio dither control is carried out, by setting at least a cylinder with the highest gas impingement intensity in a cylinder group of an internal combustion engine as the one or more lean cylinders.

When executing a Local-learning, an air-fuel ratio detecting time is corrected so that a dispersion of detection values of an air-fuel ratio sensor becomes a maximum value in one cycle of an engine. While executing a cylinder-by-cylinder air-fuel ratio control, a Global-learning is executed. In the Global-learning, the air-fuel ratio detecting time is corrected based on a relationship between a variation in estimated air fuel ratio of each cylinder and a variation in fuel quantity correction value of each cylinder. In the Global-learning, a computer computes a correlation coefficient between the variation in estimated air-fuel ratio and the variation in fuel quantity correction value of the cylinder for each case where the cylinder assumed to correspond to the estimated air fuel ratio is hypothetically varied in multiple ways. Then, the air-fuel ratio detecting time is corrected so that this correlation coefficient becomes a maximum value.

An engine includes a plurality of combustion cylinders configured to burn a fuel to power the engine, and a plurality of fuel injectors. Each of the fuel injectors is arranged to distribute fuel delivered from a fuel tank to one of the plurality of combustion cylinders. The engine also includes a controller programmed to adjust a fuel trim signal gain based on sensing exhaust flow downstream of the combustion cylinders. The controller is also programmed to monitor a cumulative misfire count for each of the plurality of combustion cylinders. The controller is further programmed to issue a prognosis message identifying a state of health of at least one of the plurality of fuel injectors in response to a fuel trim signal gain exceeding an adjustment threshold and a cumulative misfire count greater than a misfire threshold.

An air fuel ratio control apparatus controls an air fuel ratio of an internal combustion engine. The apparatus includes an upstream sensor measuring the air fuel ratio of exhaust gas in an exhaust passage at an upstream side of a purification catalyst; a downstream sensor measuring the air fuel ratio of the exhaust gas in the exhaust passage at a downstream side of the purification catalyst; and a control unit that adjusts an amount of fuel supplied to the internal combustion engine, thereby controlling the air fuel ratio measured at the upstream sensor to be a target air fuel ratio. The control unit performs a calibration control where a calibration value corresponding to the air fuel ratio deviation is added to or subtracted from the target air fuel ratio such that the air fuel ratio deviation approaches zero.

A fuel vapor processing apparatus includes an adsorbent canister, a vapor path connecting the adsorbent canister to a fuel tank, and a flow control valve disposed in the vapor path. The flow control valve is kept closed while a movement distance of a valve body from a predetermined initial position toward a valve opening direction is less than a predetermined distance. A control unit comprising part of the apparatus is configured to set a valve opening speed of the flow control valve to a first speed under a condition where the movement distance of the valve body is less than the predetermined distance, and to set the valve opening speed of the flow control valve to a second speed lower than the first speed under a condition where the movement distance of the valve body is greater than the predetermined distance.