An ignition plug includes a tubular insulator, a metallic shell disposed around the outer circumference of the insulator, a center electrode disposed in an axial hole of the insulator, and a ground electrode connected to the forward end of the metallic shell and facing the center electrode. The metallic shell has a threaded portion to be engaged with an internal combustion engine. The relational expression Ss/(Sa+Sb)2.6 is satisfied, where Ss is the surface area of an outer circumferential surface of the metallic shell extending from the rear end of the threaded portion to the forward end of the threaded portion, Sa is the surface area of that portion of the metallic shell which is to be exposed to combustion gas of the internal combustion engine, and Sb is the surface area of that portion of the insulator which is to be exposed to the combustion gas.

A flow guiding device for an internal combustion engine includes a main body substantially in the shape of a surface shell of a truncated cone and/or a cylinder and a plurality of orifices in the main body. The main body is adapted to be mounted between a cylinder head body and an ignition assembly of the internal combustion engine, and wherein the orifices are adapted to guide a cooling medium between an outside volume and an inside volume of the truncated cone or cylinder.

A flow guiding device for an internal combustion engine includes a main body substantially in the shape of a surface shell of a truncated cone and/or a cylinder and a plurality of orifices in the main body. The main body is adapted to be mounted between a cylinder head body and an ignition assembly of the internal combustion engine, and wherein the orifices are adapted to guide a cooling medium between an outside volume and an inside volume of the truncated cone or cylinder.

An engine system in which blow-by gas with a specific gravity less than 1 with reference to air is generatable includes a cylinder block. The cylinder block includes a cylinder and a crank chamber which are arranged in an up/down direction, the crank chamber being positioned below the cylinder. An internal peripheral face of the cylinder block has a ventilation port that connects to a ventilation passage that connects an internal space of the crank chamber with an external space out of the cylinder block, and that is open. The ventilation port is placed above a center in the up/down direction in the crank chamber.

An engine system in which blow-by gas with a specific gravity less than 1 with reference to air is generatable includes a cylinder block. The cylinder block includes a cylinder and a crank chamber which are arranged in an up/down direction, the crank chamber being positioned below the cylinder. An internal peripheral face of the cylinder block has a ventilation port that connects to a ventilation passage that connects an internal space of the crank chamber with an external space out of the cylinder block, and that is open. The ventilation port is placed above a center in the up/down direction in the crank chamber.

An outboard motor includes an internal combustion engine. The internal combustion engine includes a cylinder head including a fuel injector including an injection portion, and an ignition including an ignition portion that provides ignition within a combustion chamber. The ignition portion is deviated in an upward-downward direction, in which a valve actuating shaft extends, with respect to the injection portion in a central region of the combustion chamber. The ignition is mounted in the cylinder head.

An outboard motor includes an internal combustion engine. The internal combustion engine includes a cylinder head including a fuel injector including an injection portion, and an ignition including an ignition portion that provides ignition within a combustion chamber. The ignition portion is deviated in an upward-downward direction, in which a valve actuating shaft extends, with respect to the injection portion in a central region of the combustion chamber. The ignition is mounted in the cylinder head.

An object of a control method to control a direct injection internal combustion engine that directly injects fuel in a cylinder is to reduce an increase in PN caused by attachment of the fuel to a fuel injection valve distal end. The control method cools the fuel before a fuel temperature when the fuel passes through an injection hole on a fuel injection valve reaches a temperature at which an amount of attached fuel to the fuel injection valve distal end increases.

An object of a control method to control a direct injection internal combustion engine that directly injects fuel in a cylinder is to reduce an increase in PN caused by attachment of the fuel to a fuel injection valve distal end. The control method cools the fuel before a fuel temperature when the fuel passes through an injection hole on a fuel injection valve reaches a temperature at which an amount of attached fuel to the fuel injection valve distal end increases.

A cooling system for an internal combustion engine is provided. The cooling system comprises: a cooling passage provided within an engine housing of the engine, the cooling passage configured to carry a bulk flow of coolant to cool the engine housing, wherein the bulk flow of coolant within the cooling passage is driven by convection or a pump; and one or more additional cooling passages provided within the engine housing, each configured to introduce a flow of coolant into the cooling passage; one or more additional cooling passage pumps configured to pump coolant within the additional cooling passages; wherein the engine housing comprises one or more high temperature regions, which are at a higher temperature than one or more low temperature regions of the engine housing; and wherein the additional cooling passages are configured to direct the introduced coolant towards the one or more high temperature regions.