In an upstream portion from a valve connecting surface that is formed in an opening of an intake port to a combustion chamber, an upper wall surface of the intake port continues from an upstream side end of the valve connecting surface and extends substantially straight and diagonally with respect to a ceiling surface on the intake port side. In addition, a cross-sectional shape of the portion in the intake port in a direction perpendicular to an axial direction of the intake port is a flat shape with an axis in a transverse direction being a long axis.

An outboard motor includes a cylinder block, a cylinder head unit, a delivery pipe, a plurality of injectors, a fuel pump, and a fuel pipe. The cylinder block includes a plurality of cylinders. The cylinder head unit is connected to the cylinder block. The delivery pipe is attached to the cylinder head unit. The injectors are attached to the delivery pipe. The fuel pump is attached to the cylinder head unit. The fuel pipe is attached to the delivery pipe and the fuel pump. A first attachment direction of attaching the fuel pump to the cylinder head unit is parallel or substantially parallel to a second attachment direction of attaching the fuel pipe to the delivery pipe.

An object is to improve the combustion condition in an internal combustion engine equipped with a supercharger and performing diesel combustion using fuel having a relatively high self-ignition temperature in an operation state in which the engine load is increased or decreased. A control apparatus performs first injection during the compression stroke, causes spray guide combustion to occur, and starts to perform second injection at such a second injection time that combustion of injected fuel is started by flame generated by the spray guide combustion, thereby causing self-ignition and diffusion combustion of fuel to occur. During a response delay period in changing the boost pressure when changing the engine load of the internal combustion engine to a target engine load, the ratio of the quantity of fuel injected by the first injection to the total fuel injection quantity in one combustion cycle is made higher than the ratio of the quantity of fuel injected in the first injection to the total fuel injection quantity in one combustion cycle during the time when the engine load is equal to the target engine load and the actual boost pressure is equal to a target boost pressure corresponding to the target engine load.

An engine system capable of controlling an intake air flow includes a combustion chamber, an ignition plug, an intake air flow control valve, and a controller. The controller performs, in at least a part of an operating range, SPCCI combustion in which after jump-spark ignition combustion of a portion of a mixture gas inside the combustion chamber by a jump-spark ignition of the ignition plug, compression ignition combustion of the remaining mixture gas is carried out by a self-ignition. The controller strengthens, at least in a part of the operating range of SPCCI combustion, the intake air flow inside the combustion chamber by controlling the intake air flow control valve. The controller controls, in a middle-load range of the operating range where SPCCI combustion is performed, the intake air flow control valve so that the intake air flow becomes weaker than in a high-load range and a low-load range.

An engine control apparatus includes an ignition control section and an injection control section. When partial compression ignition combustion is carried out, the ignition control section causes an ignition plug to carry out: main ignition in which a spark is generated in a late period of a compression stroke or an initial period of an expansion stroke to initiate the SI combustion; and preceding ignition in which the spark is generated at earlier timing than the main ignition. Also, when the partial compression ignition combustion is carried out, the injection control section causes the injector to inject fuel at such timing that the fuel exists in a cylinder at an earlier time point than the preceding ignition. Energy of the preceding ignition is set to be higher when an engine speed is high than when the engine speed is low.

Methods and systems are provided for a pre-chamber. In one example, a pre-chamber comprises a plurality of slots fluidly coupling it to a primary combustion chamber. The plurality of slots comprising a plurality of corresponding flaps configured to direct gases through the plurality of slots.

A combustion chamber structure for an internal combustion engine includes a recessed portion formed in a pent roof of a cylinder head on an upstream side of a tumble flow with respect to a spark plug.

Methods and systems are provided for a prechamber. In one example, a system includes a plurality of openings angularly arranged in a prechamber wall. The plurality of openings is oriented to receive and expel fluids in clockwise or counterclockwise directions.

Methods and systems are provided for a prechamber. In one example, a system includes a plurality of openings angularly arranged in a prechamber wall. The plurality of openings is oriented to receive and expel fluids in clockwise or counterclockwise directions.

An engine is provided, which includes a combustion chamber defined by a crown surface of a piston, an inner wall surface of a cylinder in which the piston is slidably accommodated, and a pentroof-type ceiling surface formed in a cylinder head and formed with an intake port and an exhaust port. The crown surface includes an exhaust-side bottom part, an intake-side bottom part, an exhaust-side sloped surface rising toward a center part of the crown surface from the exhaust-side bottom part, an intake-side sloped surface rising toward the center part from the intake-side bottom part, and a flat surface provided continuously between upper ends of the exhaust-side and intake-side sloped surfaces, and extending perpendicularly to a cylinder axial direction in the center part of the crown surface. A surface area of the flat surface is larger than a surface area of the exhaust-side sloped surface.