Methods and systems are provided for a bore. In one example, a system includes a bore portion for receiving a reciprocating piston, the bore portion having first and second ends between which the piston travels in an axial direction. The bore portion comprises a plurality of recesses, axially spaced apart, and formed in a piston facing surface of the bore portion at a plurality of axial positions, with at least one recess being provided at each axial position. Widths of the plurality of recesses decrease in the axial direction away from a mid-stroke position toward the first and second ends, and depths of the plurality of recesses increase in the axial direction away from the mid-stroke position toward the first and second ends.

An insert for an engine block and systems, assemblies, components, and methods thereof can comprise a ring-shaped body having an inner surface and an outer surface opposite the inner surface. The inner surface can having one or more sealing grooves adapted to receive and retain respective sealing rings. A maximum outer diameter of the ring-shaped body can be defined by the outer surface and can be greater than a height of the ring-shaped body in a longitudinal direction of the ring-shaped body.

An insert for an engine block and systems, assemblies, components, and methods thereof can comprise a ring-shaped body having an inner surface and an outer surface opposite the inner surface. The inner surface can having one or more sealing grooves adapted to receive and retain respective sealing rings. A maximum outer diameter of the ring-shaped body can be defined by the outer surface and can be greater than a height of the ring-shaped body in a longitudinal direction of the ring-shaped body.

A combustion chamber is defined by a cylinder block, a cylinder head, and a piston. The cylinder block includes a block body that has a cylinder inner wall covered by a coat layer. The coat layer includes: a heat-shielding layer that covers an upper end of the cylinder inner wall, a piston ring not slidingly contacting the upper end; a heat-insulating layer arranged on a back side of the heat-shielding layer; and a heat diffusion layer arranged between the heat-insulating layer and the heat-shielding layer. Regarding thermal conductivity, the heat-insulating layer is lower than the block body, the heat-shielding layer is lower than the block body and the heat-insulating layer, and the heat diffusion layer is higher than the heat-insulating layer and the heat-shielding layer. The heat diffusion layer includes a side end edge and an extending portion, each of which abuts the block body.

A combustion chamber is defined by a cylinder block, a cylinder head, and a piston. The cylinder block includes a block body that has a cylinder inner wall covered by a coat layer. The coat layer includes: a heat-shielding layer that covers an upper end of the cylinder inner wall, a piston ring not slidingly contacting the upper end; a heat-insulating layer arranged on a back side of the heat-shielding layer; and a heat diffusion layer arranged between the heat-insulating layer and the heat-shielding layer. Regarding thermal conductivity, the heat-insulating layer is lower than the block body, the heat-shielding layer is lower than the block body and the heat-insulating layer, and the heat diffusion layer is higher than the heat-insulating layer and the heat-shielding layer. The heat diffusion layer includes a side end edge and an extending portion, each of which abuts the block body.

An object of the present invention is to provide a cylinder liner for insert casting that can improve the joining strength between a cylinder liner and a cylinder block by reducing voids generated between the cylinder liner and the cylinder block. The above-described problem can be solved when the molten metal running index YI defined by the following Formula (1) is from 2.2 to 14.5.
Molten metal running index YI=[area ratio S.sub.t (%) of top portions of protrusions×molten metal infiltration volume V (mm.sup.3)/surface area A (mm.sup.2) of cylinder liner base]/average surface-to-surface distance P.sub.av between top portions of protrusions (mm)  (1).

In a sliding structure for an internal combustion, a cylinder has recesses in a stroke center region. Piston rings have inclined surfaces on an outer circumferential surface, and a lubricating oil flows between the inner wall surface and the outer circumferential surface that relatively move via the inclined surfaces. At any RPM equal to or greater than at idle, a center friction coefficient at the stroke center region through which the piston rings pass at the highest speed is less than a center friction coefficient when no recesses are formed in the stroke center region. Contrarily, at the RPM, an outside friction coefficient when the piston rings pass through a region outside the stroke center region is less than an outside friction coefficient when the recesses are formed in the outside region. As a result, further improved low fuel efficiency is achieved for the dimple liner technique.

A method for processing an inner wall of a cylinder of an internal combustion engine includes providing a cylinder and processing an inner wall of the cylinder. The cylinder extends along a cylinder axis. The inner wall of the cylinder is processed in such a manner that at least one first structural region and one second structural region are formed along the cylinder axis. A geometry of the first structural region differs in design from a geometry of the second structural region.

A method for processing an inner wall of a cylinder of an internal combustion engine includes providing a cylinder and processing an inner wall of the cylinder. The cylinder extends along a cylinder axis. The inner wall of the cylinder is processed in such a manner that at least one first structural region and one second structural region are formed along the cylinder axis. A geometry of the first structural region differs in design from a geometry of the second structural region.

A piston pump includes a frame, a housing configured to be coupled to the frame via a fastener, an annular liner defining a chamber configured to receive a piston of the piston pump, and an annular liner lock flange circumferentially surrounding the annular liner. The annular liner lock flange includes a radially-extending portion configured to be positioned within a respective counterbore of the frame and a respective counterbore of the housing while the housing is coupled to the frame via the fastener to block relative movement between the liner lock flange, the frame, and the housing.