Engine blocks and methods of forming engine blocks are disclosed. The engine block may include a cast aluminum body and a plurality of cast-in liners. Each cast-in liner may include (a) an outer layer of 2xxx-series aluminum molecularly bonded to the cast aluminum body and (b) an inner layer directly contacting the outer layer and forming at least a portion of an engine bore. The inner layer may be a wear-resistant coating, such as a steel coating. The method may include extruding an elongated 2xxx-series aluminum extrusion having an inner cavity bounded by an inner surface and applying a wear-resistant coating to the inner surface. The extrusion may be sectioned into a plurality of cylinder liners and the cylinder liners may be into an aluminum engine block such that each cast-in liner forms at least a portion of an inner surface of an engine bore in the engine block.

In a spark ignition engine, a thermal insulation thin layer is formed over a wall surface, facing an inside of a combustion chamber, of a base material forming the combustion chamber, and for a thermal conductivity [W/(m.Math.K)], a thermal diffusivity [mm.sup.2/s], and a thickness L [m] of the thermal insulation thin layer, L16.7 and L207.4().sup.0.5 are satisfied. With such a configuration, a heat loss Q_total escaping from gas in a cylinder to the wall of the combustion chamber over all strokes can be reduced, and the thermal efficiency can be improved without inducing degradation of knocking due to an increase in an amount of heating Q_intake of the gas in the cylinder during an intake stroke.

A cylinder liner assembly is disclosed for use with an engine. The cylinder liner assembly may include a liner having a hollow generally cylindrical body extending from a top end to a bottom end along a longitudinal axis, and an internal annular cuff ring groove formed at the top end of the liner. An internal surface of the internal cuff ring groove may include a metal spray coating having a thermal conductivity that is less than a thermal conductivity of a base material of the liner to act as a thermal insulating layer. A cuff ring may be disposed within the internal cuff ring groove at the top end of the liner in contact with the metal spray coating. A seal may be disposed around an outer circumferential surface of the liner approximately in axial alignment with an internal axial end of the internal cuff ring groove.

A method for improving combustion in a combustion chamber of an internal combustion engine, a heat retaining element, and an internal combustion engine are provided. The internal combustion engine includes a main combustion chamber arranged between a head and a reciprocating piston, and a heat retaining element provided between the head and the main combustion chamber. The heat retaining element is a self-supporting structure coupled to the head that is configured to reduce heat transfer from the main combustion chamber into the engine head. The heat retaining element includes a head-facing portion substantially corresponding in shape to a portion of the head facing the main combustion chamber. The heat retaining element is provided such that a gap is provided between the head-facing portion of the heat retaining element and the portion of the head facing the main combustion chamber.