A gasoline compression ignition engine is operated in two modes. In a one mode of operation the engine is operated with a firing fraction of one, corresponding to all of the cylinders being active, working cylinders. In a second skip fire mode of operation a firing fraction of less than one may be used under conditions, such as a low load condition, to improve efficiency. The skip fire mode of operation may also be selected in part based on other considerations, such as maintaining an exhaust temperature conducive for efficient catalytic converter operation or limiting cylinder output variability.

An asymmetry cylinder de-activation (CDA) engine provided with a first, a second, a third and a fourth cylinder of which CDA apparatuses are mounted thereto respectively may include a crankshaft connected with pistons of each cylinder through a first, a second, a third and a fourth cranking journal respectively, and a controller configured to control operations of the CDA apparatuses, in which phase differences between cranking journals according to firing order may include 90±10 degrees and 270±10 degrees.

A method of operating a gasoline engine having a first subset of cylinders and a second subset of cylinders includes providing a flow of compressed air from a single-sequential compressor to the engine, selectively deactivating the first subset of cylinders, and igniting gasoline mixed with the compressed air in the second subset of cylinders. The single-sequential compressor includes a dual sided impeller having a first blade arrangement in fluid communication with a first air inlet, and an opposing second blade arrangement in fluid communication with a second air inlet. Additionally, deactivating the first subset of cylinders includes sealing the first subset of cylinders such that the flow of compressed air is provided only to the second subset of cylinders.

An internal combustion engine includes cylinders that are divided into a first cylinder group and a second cylinder group, a cylinder reduction mechanism that holds intake valves and exhaust valves of the first cylinder group in closed states so as to establish a reduced-cylinder state. When the engine is stopped in the reduced-cylinder state, the electronic control unit provided in the engine starts the engine by ignition, by executing fuel injection and ignition in an expansion-stroke cylinder. When the first cylinder group includes an exhaust-stroke cylinder, the engine is started by ignition through fuel injection and ignition in the expansion-stroke cylinder, after a piston is moved in a reverse direction through fuel injection and ignition in the exhaust-stroke cylinder. When the first cylinder group does not include the exhaust-stroke cylinder, the engine is started by ignition, through fuel injection and ignition in the expansion-stroke cylinder and an intake-stroke cylinder.

A torque request module determines a torque request for an engine based on a driver input. A cylinder control module determines a target fraction of a total number of cylinders of the engine to be activated based on the torque request. An air fuel imbalance (AFIM) module selectively commands that the cylinder control module set the target fraction based on a predetermined fraction of the total number of cylinders of the engine to be activated. The cylinder control module further: sets the target fraction based on the predetermined fraction in response to the command; and activates and deactivates opening of intake and exhaust valves of the cylinders of the engine based on the target fraction. The AFIM module further, while the target firing fraction is set based on the predetermined fraction, selectively diagnoses the presence of an AFIM fault based on samples of a signal from an oxygen sensor.

Systems and methods for operating an engine with an oil pump that supplies engine oil to various oil consumers in an engine are presented. In one example, a displacement of a variable displacement engine oil pump is adjusted to provide sufficient oil pressure throughout the engine, but low enough to conserve fuel.

Systems and methods for operating an engine with deactivating and non-deactivating valves are presented. In one example, estimates of engine fuel consumption for operating the engine with a plurality of cylinder modes or patterns while a transmission is engaged in different gears are determined and are used as a basis for deactivating engine cylinders.

Systems and methods for operating an engine with deactivating and non-deactivating valves are presented. In one example, mode changes between deactivating cylinders is based on an amount of time a valve is deactivated, and the longer the valve is deactivated the sooner cylinder valves may be deactivated. If the amount of time the valve is deactivated is short, the time that valves may be deactivated may be delayed.

Systems and methods for operating an engine with deactivating and non-deactivating valves are presented. In one example, fuel supplied to cylinders being reactivated is supplied by direct fuel injectors even though the engine is operating in a region (e.g., speed and torque) where under conditions where cylinders are not being reactivated the engine injects fuel solely via port fuel injectors.

Systems and methods for operating an engine with deactivating valves are presented. In one example, deactivated valves may be reactivated to increase a rate of camshaft phase indexing relative to engine crankshaft position. However, if a desired rate of camshaft indexing is low, the engine cylinders may remain deactivated based on the low rate of desired camshaft indexing.