How Do Engine Piston Rings Actually Work – What Causes Them To Fail

How Do Engine Piston Rings Actually Work - What Causes Them To Fail
How Do Engine Piston Rings Actually Work - What Causes Them To Fail

In everyday vehicles the engine piston rings have, the most important job, of sealing the combustion chamber.

So, one of the most prominent materials, used in making engine piston rings is cast iron.

This is because it contains graphite, which itself acts as a lubricant, between the rings and the cylinder.

Some engine piston rings even have alloys and coatings, to increase functionality for specific applications.

Most engine piston rings used today, include three different ring types, the compression ring, wiper ring, and oil ring.

How Do Engine Piston Rings Actually Work - What Causes Them To Fail
How Do Engine Piston Rings Actually Work – What Causes Them To Fail

The life span of engine piston rings entirely depends on:

  • The piston ring type
  • The size of the engine
  • And the operating conditions

How Do Engine Piston Ring Actually Work:

The Top Grove Holds, The Compression Ring

The main function is to, seal any kind of leakage inside the combustion chamber, during the combustion process. The pressurized gases travel through the gap; between the cylinder wall and the piston and into the piston ring groove.

Compression Ring
Compression Ring

During the combustion process, the force of high-pressure gases; presses the piston ring against the cylinder wall. This pressure pushing the piston ring, is proportional to the combustion gas pressure.

The Second Grove Holds, The Wiper Ring (sometimes called the scraper ring)

They have a tapered face construction, and are used to further seal the combustion chamber. As the name suggests, they assist in wiping the cylinder wall clean; of any excess oil and impurities. So, if gases were able to pass by the compression ring; these gases will be blocked by the wiper ring.

The Third Grove Holds, The Oil Rings

The main function of the oil ring is, to scrape any excess oil, from the walls of the cylinder. As a result, the majority of the wiped oil, is directed into the crankcase, back to the oil sump.

Oil Rings
Oil Rings

These oil rings come, spring fitted at the back, to provide an additional push for wiping the cylinder.

Rings Have Four Basic Jobs To Do:

Sealing Engine Compression

Piston rings maintain the compression, between the piston and the cylinder wall. Piston rings seal the cylinder; so that combustion gas, does not leak between the piston and the cylinder. If combustion gas leaks, the engine cannot output sufficient power, increasing fuel consumption.

Lubricating Oil Film Control

Piston rings usually make, a necessary lubricating oil film to preventing scuffing. But, enough so they move smoothly, with little friction between metal and metal. Finally, piston rings automatically adjust the amount of oil needed, for proper operation.

Proper Heat Transfer

Consequently, piston rings transfer heat from the piston crown to the cylinder.

Proper Heat Transfer
Proper Heat Transfer

So, if heat accumulates inside the piston, the engine may be damaged. For that reason, it is necessary to release the heat build-up.

Piston Support

Piston rings prevent the piston from, knocking on the cylinder wall. If the piston contacts the cylinder walls, piston scuffing is a possibility. Piston rings support the piston during travel, to allow for smooth up and down motion.

Ring Failure

The combustion chamber exerts, tremendous pressure on the piston rings. If the combustion pressure is higher than the usual, it may affect the ring performance.

Oil Consumption Going Past Piston Rings
Oil Consumption Going Past Piston Rings

This can be due to detonation and pinging. As a result, of a leaky injector or when the fuel is mixed with dirty air.

Contaminated fuel or the wrong grade of engine oil, will also affect the performance of the rings.

Engine oil quality, bad combustion process, wrong fuel timing, worn cylinders; are the normal cause of piston ring wear. Sticky rings due to carbon or sludge deposit, and breaking or crack on the ring can result due to wear.

Narrow Groove Rings

The narrower the ring, the more fragile they become. As piston rings are made narrower, the strength needs to increase. For this reason, a performance build using narrow rings means; that you need the strongest material. Steel-based rings are 20-percent stronger, than ductile iron rings; making them the ideal choice for narrow rings. Ductile iron rings are very strong and forgiving.

Horsepower is not the only benefit of a narrow steel ring. Because, the ring is so narrow, it reduces friction, and can conform to the cylinder wall better.

Narrow Groove Engine Piston Rings
Narrow Groove Engine Piston Rings

So, the engine is more efficient and seals better. This means less oil blow by and less emissions. Steel rings last longer, but, they do take longer to break in.


So, piston rings must deal with an assortment of issues. Bad gas (detonation and pinging), dirty air and fuel, and contaminated oil; all reduce the life of piston rings. Maintaining the filters on your engine and regular oil changes; make a big difference in how long the rings last. Finally, once the rings have worn down, their ability to seal the combustion gases will become apparent.

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