How Can You Select the Correct Piston Ring?

While the function of piston rings is obvious, that being cylinder sealing and oil control, another central function is carrying heat from the piston to the cylinder wall through direct contact. Since piston rings are made thinner for friction reduction, efficiency, and more power, heat transfer between the piston and cylinder walls has become more critical and more difficult on pistons. For high-performance engines, piston ring selection is particularly important and depends on how your engine will be used.

There are three basic piston rings types: cast, hypereutectic, and forged piston rings. Cast pistons are usually considered old-school and served most cars and trucks back in the day. Hypereutectic pistons, on the other hand, are of the high silicon cast variety and are often chosen for their hardness and low price points. Lastly, forged pistons are very rugged and have the ability to withstand a lot of abuse; thus, they are the only choice for high-performance applications. The downside, however, is that forged pistons require greater piston-to-cylinder wall clearances since they employ aggressive expansion rates. As such, they are often noisy on a cold-start, but the noise dissipates as the engine warms.

Ring width is also a major consideration when deciding what piston ring your engine necessitates, and this is determined by the way your engine will be used. If you use your engine for racing or conducting a fuel economy challenge, thinner piston rings are optimal as they create less friction and consume less energy. Conventional piston ring dimensions are wider, making them appropriate for weekend cruisers and daily commuters. Standard ring packages used to include 5/64-inch top compression and secondary rings, alongside a 3/16-inch oil ring package. These dimensions apply to a ring’s thickness.

Over time, automotive engineers realized that thinner piston rings would reduce internal friction and improve efficiency. That being said, factory engines came equipped with a 1.5mm/1.5mm/3.0mm piston ring package beginning in the 1980s. With thinner piston rings, the amount of radial tension needed to seal the ring against the cylinder wall is greatly reduced. As the total surface area of the ring touching the cylinder wall is reduced, radial tension is also mitigated to produce the same amount of load as the ring.

For performance applications, choosing the proper piston configuration and compression ratio, along with selecting an optimized ring package, is paramount, and this begins with picking the right ring material. For instance, carbon steel piston rings can handle higher operating temperatures without losing temper. In contrast, cast iron piston rings are more fragile and tend to necessitate replacement with time. Moreover, for excessive amounts of compression, steel piston rings have better tolerances. Other ring materials include chrome-faced, steel nitride, and hardened ductile iron piston ring options.

Cogent Sourcing is an online distributor of aviation parts, all of which have been sourced from top global manufacturers that we trust. Our inventory is stocked with new, used, obsolete, and hard-to-find items that are ready for immediate procurement at any time. Some of the products we carry include top-request piston ring options, those of which you can request a comprehensive quote on at your earliest convenience. We only ask that you include as much information as possible in your quote request so that we can tailor a sourcing solution that keeps your needs in mind. Kickoff the purchasing process today and see how Cogent Purchasing can serve as your strategic parts distributor. For additional questions, call or email us whenever you like; we are available 24/7x365!


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