The Best Piston Rings for Nitrous/Boost and How to Gap Them
Everybody loves nitrous and boost. They’re proven ways to significantly increase your engine’s power potential. But simply screwing a couple turbos or a nitrous plate to an engine that wasn’t prepared for the job is a recipe for disaster. In the video below, Lake Speed Jr. from Total Seal Piston Rings talks about the best piston rings for nitrous, and nitrous ring gap. He also points out the best piston rings for boost and the piston ring gap for boost is based on the same concept.
What Are the Best Piston Rings for Nitrous?
Under about a 200hp shot of nitrous, a common ductile moly ring will be acceptable. In more extreme applications, Total Seal recommends a steel ring. This means either a stainless ring or in severe situations, rings made from M2 tool steel. Why? The answer is in the ring material’s ability to handle heat. Ductile moly rings are basically cast iron with a moly coating. The moly coating is relatively soft and porous, which makes for easy break-in and long life in less severe situations, but can be problematic as nitrous is added to the equation. When nitrous is added to the combustion chamber, it creates a very fast burning, hot flame. Great for making power, but also great for making heat and potentially a small amount of detonation. Under these extreme conditions, that moly coating on the ring can actually start to flake off, potentially causing the ring to crack and break.
Steel rings, however, are not subject to this issue. First, the steel material is better suited to the rigors of a nitrous engine. It has better heat handling capabilities and is less prone to breaking like an iron ring. Total Seal steel rings also have a PVD (physical vapor deposition) coating that will not flake off or separate from the ring like the moly coating.
What Are the Best Piston Rings for Boost?
The best turbo piston ring and supercharger piston ring will also be a steel ring. The concept is very much the same. As you add boost, you’re adding temperature as well as cylinder pressure. As boost levels increase, this becomes more critical.
Piston Ring Gap for Nitrous and Boost
The same temperature issue that applies to piston ring material selection also applies to ring gap. As power levels increase, so does heat. As temperatures increase, piston rings expand. The ring gap allows for this expansion and, obviously, the more gap there is, the more the ring can grow as combustion temps increase.
What happens when you run out of gap? This is known as “butting” a ring and, as Lake Speed Jr. puts it in the above video, it makes for a “bad, bad day.” When the ring can no longer grow, it begins to force itself out into the cylinder wall. This can cause scuffing or, even worse, can break the piston.
Nitrous Ring Gap Chart and Ring Gap Chart for Boost
As a general rule for baseline ring gap, shoot for a gap of .005” per inch of bore size with a minimum of .015” total on the oil rails. As noted above, this gap needs to increase as nitrous and boost are added. How much? Fortunately, you don’t need a nitrous ring gap calculator or a ring gap calculator for boost. Instead, this chart from Total Seal shows you how to figure out the perfect ring gap for nitrous and boosted applications.
Check out all the Total Seal rings available from Speedway Motors. Need the right tools to help you gap your rings? Speedway Motors offers piston ring filer tools and other piston ring files to precisely file and gap your rings.