In a case where an internal combustion engine is executing an all-cylinder operation to operate all cylinders, an air-fuel ratio estimation part of an ECU 1 estimates an air-fuel ratio of each of the cylinders by using a first observer. On the other hand, in a case where the internal combustion engine is executing a cylinder-cut operation to rest a part of the cylinders and to operate other of the cylinders, the air-fuel ratio estimation part does not estimate the air-fuel ratio of each of the cylinders by using the first observer.

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.

Engine controllers and control schemes are provided for managing engine state transitions requiring increased compressor pressure ratios in turbocharged engines operating in a cylinder output level modulation mode (e.g., skip fire, multi-level skip fire, or firing level modulation modes). In some circumstances, turbo lag can be mitigated by initially transitioning the engine to an intermediate effective firing density that is higher than both the initial and target effective firing density to increase the flow of gases through the engine and the turbocharger while maintaining a compressor ratio the same as or close to the initial compressor pressure ratio. After reaching a point where the desired torque is actually generated at the intermediate effective firing density, the operational effective firing density is gradually reduced to the target effective firing density while increasing the operational compressor pressure ratio to the target compressor ratio.

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.

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.

A gas feeding arrangement for feeding gas from an internal combustion engine cylinder chamber to a gas tank includes a feeding conduit assembly and a dedicated feeding valve. The feeding valve is adapted to assume an open condition in which it provides for gas transport in a direction from the cylinder chamber towards the gas tank, via the feeding conduit assembly. The gas feeding arrangement includes a one-way valve adapted to prevent gas transport from the gas tank to the cylinder chamber, via the feeding conduit assembly.

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 control apparatus is applied to an internal combustion engine that is capable of implementing reduced-cylinder operation and all-cylinder operation. When the internal combustion engine is stopped during implementation of reduced-cylinder operation, and then the internal combustion engine is restarted in reduced-cylinder operation with the same cylinders as idling cylinders, the initial crank angle when cranking starts is controlled so that the position of the piston of at least one among the idling cylinders is in the vicinity of its top dead center.

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.