Mäntärenkaat

Mäntärenkaat, often translated as piston rings, are metal rings that fit into the grooves on the outer side of a piston in an internal combustion engine. Their primary functions are to form a seal between the piston and the cylinder wall, control oil consumption, and transfer heat from the piston to the cylinder wall.

There are typically two or three rings per piston. The top ring, known as the compression ring, is designed to seal the combustion gases, preventing them from escaping into the crankcase. The second ring, often also a compression ring or a scraper ring, helps to further seal the combustion chamber and also scrapes excess oil from the cylinder wall. The lowest ring, the oil control ring, is designed to scrape excess oil from the cylinder wall and return it to the crankcase, preventing it from entering the combustion chamber where it would be burned.

Mäntärenkaat are usually made from cast iron, steel, or a combination of materials, often with special coatings to improve wear resistance and reduce friction. The precise design and material of the rings are crucial for engine performance, fuel efficiency, and emissions control. Worn or damaged mäntärenkaat can lead to symptoms such as reduced engine power, increased oil consumption, blue smoke from the exhaust, and poor compression.