A valve actuation system for an internal combustion engine is disclosed. The engine has a first set of cylinders having a first set of exhaust valves and a second set of cylinders having a second set of exhaust valves. The valve actuation system for the exhaust valves includes one or more first cams having a compression-release lobe and a main exhaust lobe adapted to transfer valve actuation motion to the first set of exhaust valves, and one or more second cams having an early exhaust valve opening (EEVO) lobe and a main exhaust lobe adapted to transfer valve actuation motion to the second set of exhaust valves. The valve actuation system may provide any combination of (i) main exhaust valve actuation with or without compression release actuation with (ii) main exhaust valve actuation with or without EEVO for the two sets of cylinders.

A control apparatus for an engine is provided. The control apparatus includes an intake control valve controller for fully closing, when an engine stop request is issued, an intake control valve for adjusting a flow rate of intake air passing through an intake passage of the engine, an engine speed increase controller for increasing an engine speed to reach a target speed after the intake control valve is fully closed by the intake control valve controller, and a fuel injection stopper for stopping a fuel injection after the engine speed is increased by the engine speed increase controller.

A fuel estimation apparatus includes a combustion characteristic acquisition portion and a mixing ratio estimation portion. The combustion characteristic acquisition portion acquiring a combustion characteristic value indicating a physical amount relating to a combustion of an internal combustion engine acquires the combustion characteristic values of the combustions executed in different combustion conditions. The mixing ratio estimation portion estimates the mixing ratios of various components included in a fuel, based on the combustion characteristic values acquired by the combustion characteristic acquisition portion.

Systems and methods for operating an engine with deactivating and non-deactivating valves are presented. In one example, a position of an engine air intake throttle is adjusted during cylinder deactivation to control intake manifold pressure for cylinder reactivation. Closing of the throttle may be timed based on an actual total number of cylinder induction events expected to provide a desired engine intake manifold pressure.

A controller, in shifting the state of the EGR system from the EGR operating state to the EGR non-operating state at the time of performing the deceleration of the vehicle, calculates a provisional EGR ratio that is a provisional value of the current EGR ratio, estimates the provisional EGR ratio as the actual EGR ratio when a fore-and-aft differential pressure of the EGR valve is equal to or more than a predetermined value, performs correction to make the provisional EGR ratio smaller, and estimates the corrected provisional EGR ratio as the actual EGR ratio when the fore-and-aft differential pressure of the EGR valve is less than the predetermined value.

A vehicle control system for an internal combustion engine having a fuel injection valve for injecting fuel directly into a combustion chamber includes a controller configured to perform a fuel cut-off when a predetermined fuel cut-off condition is met during travel of the vehicle to thereby stop fuel injection from the fuel injection valve. The controller is configured to resume the fuel injection from the fuel injection valve when a predetermined fuel cut-off recovery condition is met during the fuel cut-off. The controller is configured, upon elapse of a predetermined time that is required for a wall temperature of the combustion chamber to rise after resuming the fuel injection from the fuel injection valve, to perform a rich spike that temporarily increases the fuel injection amount from the fuel injection valve.

Methods and systems are provided to determine air-fuel imbalance of cylinders in a variable displacement engine. In one example, the method may include during a cylinder deactivation event, sequentially deactivating each cylinder of a cylinder group including two or more cylinders and estimating a lambda deviation for each cylinder following the sequential deactivation of each cylinder of the cylinder group; and learning an air error for each cylinder based on the estimated lambda deviation.

A variable displacement controller for deactivating one or more cylinder assemblies of a vehicle engine can include a processor for performing various operations and the operations can include: receiving data indicative of a requested torque and vehicle speed, determining a torque variable timer threshold value based on the received data indicative of requested torque and vehicle speed, initiating a timer, comparing the timer value to the variable timer threshold value, and selectively activating/deactivating at least one of the engine cylinder assemblies based on the comparison between the timer value and the variable timer threshold value. At least one of the engine cylinder assemblies is activated if the timer value is less than the variable timer threshold value, and at least one of the engine cylinder assemblies is deactivated if the timer value is greater than or equal to the variable timer threshold value.

An abnormality diagnosis system of an air-fuel ratio sensor acquires a blowby gas flow ratio showing a ratio of the flow of blowby gas to the flow of gas to a combustion chamber and an output current of an air-fuel ratio sensor during fuel cut control in which an internal combustion engine stops the feed of fuel to the combustion chamber and at a plurality of points of time of different flows of blowby gas passing through a blowby gas passage and flowing to the downstream side of a throttle valve in the intake passage, calculate an output current of the air-fuel ratio sensor corresponding to a blowby gas flow ratio smaller than the blowby gas flow ratios acquired at the plurality of points of time, based on the acquired blowby gas flow ratio and output current, and judge the air-fuel ratio sensor for abnormality based on the calculated output current.

A control device for an internal combustion engine of a vehicle has a controller that controls a fuel injection valve of the internal combustion engine arranged to directly inject a fuel into a combustion chamber, and a pressure regulator of the internal combustion engine arranged to vary a pressure of the fuel supplied to the fuel injection valve. The controller performs a fuel cut that stops the fuel injection of the fuel injection valve when a predetermined fuel cut condition is satisfied during a traveling of the vehicle. The controller restarts the fuel injection of the fuel injection valve when a predetermined fuel cut recovery condition is satisfied during the fuel cut.