Cylinder (engine)

The piston rings do not actually touch the cylinder walls, instead they ride on a thin layer of lubricating oil.

The cylinder casting can include other features such as valve ports and mounting feet.

This wear is minimized by the thin oil film which coats the cylinder walls and also by a layer of glaze which naturally forms as the engine is run-in.

The wet liners are formed separately from the main casting so that liquid coolant is free to flow around their outsides.

The advantage of wet liners is better cooling and a more even temperature distribution; however, this design reduces the rigidity of the engine.