Piston rings and their functions.

A piston ring is a seal that surrounds the piston as it moves inside an engine's cylinder wall. Piston rings serve three basic functions: provide a gas-tight seal between the combustion chamber and the crankcase; transfer heat from the piston to cooled cylinder wall; and control oil consumption.

Usually, there are three piston rings for each piston: 

01. The top ring is the top compression ring acts as the primary seal between the piston and the cylinder wall.

 

02. The middle ring acts as a secondary seal between the piston & cylinder wall to help transfer heat to the cylinder wall and assure that no gas escapes from combustion chamber .

03. The bottom the oil control ring is the final ring made up of two smaller rings with a sort of spring separating them. This spring presses the ring against the cylinder wall to protect extra oil consumption.