In an internal combustion engine, a breather chamber can be formed without increasing the number of component parts. The internal combustion engine (1) comprises an engine block (30) defining a cylinder (2); a case member (19) fastened to a lower part of the engine block to define a crank chamber (4) jointly with the engine block; and a bearing member (50) fastened to the engine block in the crank chamber to rotatably support a crankshaft; wherein the engine block is provided with a central recess (134) formed in a part thereof to which the bearing member is fastened, a blow-by gas inlet passage (112, 116, 121) communicating the central recess with the crank chamber, and a blow-by gas return passage (122, 118) forming a part of a passage communicating the central recess with an intake device, the central recess and the bearing member jointly defining a central breather chamber.

A marine outboard motor is provided with an internal combustion engine comprising an engine block defining at least one cylinder, an air intake configured to deliver a flow of air to the at least one cylinder; and an air intake duct forming part of an air intake path for delivering the flow of air to the air intake. The engine further includes a flow sensing arrangement located in the air intake duct and comprising a flow meter configured to generate a signal indicative of a flow rate of the flow of air through the air intake duct, and a bluff body located in the air intake duct upstream of the flow meter, wherein the flow meter is a vortex shedding flow meter.

In some embodiments, a fuel rail for a two-stroke internal combustion engine includes a fuel rail body, a fuel inlet component integrated within the fuel rail body as a one-piece component and in fluidic contact with a fuel line, one or more fuel exit ports in fluidic contact with a cylinder of a combustion engine, and one or more fasteners adapted to secure the fuel rail body to a cylinder wall of the cylinder of the combustion engine

Methods and systems are provided for operating a cylinder of an engine including a pre-chamber ignition system. In one example, a method may include determining amounts of pre-chamber gases in the cylinder prior to combustion, and adjusting an amount of fuel injected into the cylinder based on the amounts of pre-chamber gases in the cylinder. In this way, cylinder fueling may be compensated for additional air and/or fuel from the pre-chamber gases, which may increase an accuracy of the cylinder fueling and increase cylinder efficiency.

An upper oil pan assembly is attached to the lower portion of a cylinder block. An opening is formed on a side wall of the upper oil pan assembly. The variable compression ratio mechanism changes a top dead center position of a piston in accordance with the rotational position of a control shaft to thereby change the compression ratio. The control shaft is rotationally driven by an actuator. At least a portion of the actuator is fixed to a main bearing cap in a state in which at least a portion thereof is positioned on the outer side of an upper oil pan assembly.

An internal combustion engine with a turbocharger according to an embodiment includes a cylinder block internally including a plurality of cylinders, a cylinder head disposed on top of the cylinder block, and internally including a plurality of exhaust flow passages through which exhaust air discharged from each of the plurality of cylinders flows, and the turbocharger including a rotational shaft, a turbine wheel, and a compressor wheel, the turbine wheel being disposed at one end of the rotational shaft, the compressor wheel being disposed at the other end of the rotational shaft. At least the turbine wheel of the turbocharger is arranged inside the cylinder head. The cylinder head internally includes a plurality of scroll passages for introducing the exhaust air flowing through the plurality of exhaust flow passages to the turbine wheel, the plurality of scroll passages including a first scroll passage for introducing the exhaust air from a first range in a circumferential direction of the turbine wheel to the turbine wheel, and a second scroll passage for introducing the exhaust air from a second range, which is different from the first range in the circumferential direction of the turbine wheel, to the turbine wheel.

An internal combustion engine has a plurality of cylinders and transmission arranged adjoining the engine. If designating an average height of a combustion chamber in a region inside from a virtual cylindrical surface passing through center of a valve body of an intake valve and extending in a circumferential direction of each cylinder when a piston is at top dead center, as center height, and designating average of a height of the combustion chamber in a region outside from the virtual cylindrical surface when the piston is at top dead center, as peripheral height, the combustion chambers form a center height of a transmission side cylinder positioned most to the transmission side among the plurality of cylinders is higher than center heights of usual cylinders including one cylinder other than the transmission side cylinder and a peripheral height at the transmission side cylinder lower than peripheral heights of usual cylinders.

Methods and systems are provided for operating a cylinder of an engine including a pre-chamber ignition system. In one example, a method may include determining amounts of pre-chamber gases in the cylinder prior to combustion, and adjusting an amount of fuel injected into the cylinder based on the amounts of pre-chamber gases in the cylinder. In this way, cylinder fueling may be compensated for additional air and/or fuel from the pre-chamber gases, which may increase an accuracy of the cylinder fueling and increase cylinder efficiency.

An upper oil pan assembly is attached to the lower portion of a cylinder block. An opening is formed on a side wall of the upper oil pan assembly. The variable compression ratio mechanism changes a top dead center position of a piston in accordance with the rotational position of a control shaft to thereby change the compression ratio. The control shaft is rotationally driven by an actuator. At least a portion of the actuator is fixed to a main bearing cap in a state in which at least a portion thereof is positioned on the outer side of an upper oil pan assembly.

A crankcase includes: a main body portion aligned with a drive motor in a direction perpendicular to a motor drive shaft; and an extended portion continuous with the main body portion and located lateral to a motor housing, the extended portion receiving insertion of one end of the motor drive shaft. A power transmission mechanism that transmits power from the motor drive shaft to an input shaft is located partly in a first region defined by the main body portion and partly in a second region defined by the extended portion and communicating with the first region.