PISTON RINGS

A piston ring is a split ring that fits into a groove on the outer diameter of a piston in a reciprocating engine such as an internal combustion engine or steam engine.

The three main functions of piston rings in reciprocating engines are :

1. Sealing the combustion chamber so that there is minimal loss of gases to the crankcase.
2. Improving heat transfer from the piston to the cylinder wall.
3. Regulating engine oil consumption by scraping oil from the cylinder walls back to the sump.^[1]

The gap in the piston ring compresses to a few thousandths of an inch when inside the cylinder bore. Piston rings are a major factor in identifying if an engine is two stroke or four stroke. Three piston rings suggest that it is a four-stroke engine while two piston rings suggest that it is a two-stroke engine. Most piston rings are made of a very hard and somewhat brittle cast iron.