A method is provided for controlling an internal combustion engine including at least one first cylinder and at least one second cylinder with respective reciprocating pistons, each of the first and second cylinders being arranged to receive air from a fresh air intake arrangement, to receive fuel, and to provide repetitive combustions by means of the received air and fuel, the method including receiving in the first cylinder air from the fresh air intake arrangement, expelling from the first cylinder gases in the form of the air received in the first cylinder or gases including at least a portion of the air received in the first cylinder, guiding to the second cylinder gases expelled from the first cylinder, injecting fuel into the second cylinder so as to provide repetitive combustions with air in the gases guided from the first cylinder to the second cylinder, and, while guiding to the second cylinder gases expelled from the first cylinder, throttling or inhibiting the supply to the second cylinder of air from the fresh air intake arrangement, wherein guiding to the second cylinder gases expelled from the first cylinder includes guiding to the second cylinder all gases expelled from the first cylinder.

The present disclosure relates to an engine in which compression and expansion is performed in the same cylinder. Also disclosed is a microprocessor for controlling the state of various valves in the cylinderincluding an intake valve, a transfer valve, and an exhaust valveto cause a compression or expansion to occur. A compression tank is provided for receiving, via the transfer valve, compressed air, which may be retrieved during an expansion (combustion) cycle. Compressed air for from multiple consecutive compressions may be stored in the tank and retrieved later, including for multiple consecutive expansions. Compression and expansion are not required to occur in any fixed or predetermined pattern and the microprocessor may evaluate vehicle sensors to determine a power demand, and cause compression or expansion to occur depending on the given power demand.

A reciprocating, internal combustion engine is capable of two modes of operation. The engine comprises three cylinders of substantially equal diameter. Each cylinder is provided with a piston. During operation, all pistons are synchronized and move in phase with one another. Valves are configured to selectively close paths between the second cylinder and two combustion chambers. Further valves are provided to selectively seal intake and exhaust channels leading to the two combustion chambers. A high efficiency combustion mode is achieved by increasing an expansion ratio through intake and compression of the fuel mixture in one cylinder and expansion in two cylinders. A high power combustion mode is achieved by compression and intake of the fuel mixture in two cylinders and expansion in one cylinder.

Methods and systems are provided for an engine configured to deactivate at least some cylinders. In one example, an engine system may comprise a first group of cylinders having a first compression ratio and a second group of cylinders having a second compression ratio greater than the first.

Systems and methods for operating an engine that includes cylinders that may be deactivated are presented. In one example, intake and exhaust valves of a cylinder may be operated according to valve operation for a conventional four stroke cycle. The same valves may be operated differently during a four stroke cycle to provide air charge and exhaust charge to active cylinders during a different four stroke cycle.

Methods and systems are provided for a variable displacement engine. In one example, a method may include flowing charge air from a deactivated cylinder to an adjacent firing cylinder.

Methods and systems are provided for cooling an engine by operating an electrically driven intake air compressor. In one example, in response to a determination, based on a measured or inferred engine temperature, that the engine temperature is greater than a threshold temperature, employing the vehicle's electrically driven intake air compressor to route air through a charge air cooler and engine cylinders, while engine spins unfueled. In this way the engine temperature may be reduced even under conditions not normally amenable to engine cooling, such as at idle-stops or when an engine coolant system is degraded.

A variety of methods and arrangements are described for controlling transitions between firing fractions during skip fire or other dynamic firing level modulation operation of an engine. In general, actuator first transition strategies are described in which an actuator position (e.g., cam phase, TCC slip, etc.) is changed to, or close to a target position before a corresponding firing fraction change is implemented. When the actuator change associated with a desired firing fraction change is relatively large, the firing fraction change is divided into a series of two or more firing fraction change steps. A number of intermediate target selection schemes are described as well.

A variety of methods and arrangements are described for controlling transitions between firing fractions during skip fire or other dynamic firing level modulation operation of an engine. In general, actuator first transition strategies are described in which an actuator position (e.g., cam phase, TCC slip, etc.) is changed to, or close to a target position before a corresponding firing fraction change is implemented. When the actuator change associated with a desired firing fraction change is relatively large, the firing fraction change is divided into a series of two or more firing fraction change steps. A number of intermediate target selection schemes are described as well.

Systems and methods for operating an engine that includes cylinders that may be deactivated are presented. In one example, intake and exhaust valves of a cylinder may be operated according to valve operation for a conventional four stroke cycle. The same valves may be operated differently during a four stroke cycle to provide air charge and exhaust charge to active cylinders during a different four stroke cycle.