Even the most respectable names in the aftermarket arena often meet resistance when launching new products. May that be due to hard-headedness, complete naivete, or just flat-out resistance to change, certain engine builders find any excuse to shun the world’s latest and greatest automotive advancements. Hell, even the modern piston ring somehow gets frowned upon.
“Thinner and stronger piston rings that have been independently tested and proven to work? Ha. Sounds like a recipe for a big-ass oil leak and compression conniptions to me.”
We get why a lot of old-school engine builders and racers would remain resistant to the idea of using a slimmer piston ring set. You want something stout down there, to make that seal tighter than a packed cooler during tailgating season, right? Well technically that is correct… but only if it’s 1965 and you were re-ringing your GTO’s Tri-Power V8.
Thanks to the inevitable progression of man-made materials and their correlation to both the overall performance and design of the pistons that pump within our automobiles, companies like MAHLE Motorsport have been able to turn something as unassuming as a piston ring into a game-changer for us gearheads.
Recently, EPARTRADE held a webinar where SiriusXM’s Ch 90 “Late Shift” show host, Brad Gillie, interviewed Joe Maylish, Mahle Motorsport Program Manager, and Application Engineer, George Wright, on the benefits of stuffing slimmer Mahle piston, rings into each cylinder. For when superior race engineering requirements task you with developing the piston ring design of the future, you had better deliver the damn goods!
While the top compression ring’s occupation is to keep that compression chamber completely sealed off and at maximum pressure, the secondary ring acts as a buffer between oil and compression, with an 80- to 90-pecent focus on the compression side as opposed to oil leak prevention. Meanwhile, the lower oil ring is the first line of defense when it comes to oil control and allowing adequate amounts of lubricant to coat the piston walls. Naturally, even and reliable contact with the cylinder wall plays a vital role in each of these rings’ ability to perform its task.
Harder, Stronger, and Lasting Longer
MAHLE credits much of its piston ring’s slimmer design and unrivaled fortitude to professional race teams. Extreme temps, cylinder pressure levels, and high-RPM operations require only the best, and race teams were getting sick of piston rings failing after just a few hot laps. For as arcane as it may sound, even they too were still relying on piston ring designs pulled from the dark ages.
Once these advancements were developed and proven to perform on a reliable level across the board, auto manufacturers quickly got in on the action, with many of them ringing their pistons with these slender piston rings. This was followed shortly thereafter by this piston ring design being made available to the aftermarket community for DIY jobs and personal builds.
However, to construct a piston ring that is just as strong as it is slender, Mahle had to find the right material. So Maylish says the company’s engineers turned toward a chrome silicon steel hybrid material called “SAE 9254” for its chief material of choice. A full 35-percent stronger than traditional cast-iron piston rings, and unrivaled in regard to its resistance to fatigue, this alloy is easily conformable, performance-packed, flexible, and tougher than all hell.
Speaking of archaic engineering, did you know that the first 1/16-inch compression ring design was put into use way back in 1965? Talk about a dated design! It’s not like the grey-steel and iron 1.5 mm alternative is that much newer either, as it emerged in 1982 during the first stint of the Reagan Era!
In contrast, MAHLE’s 1 mm design came about in 2016, at a time when computer-aided design programming and advancements in material composition development had reached heights neither of the first two ring designs or their creators could fathom. The 1.0mm ring is only .039-inch thick. The wafer-thin design appears to be little more than a wisp of metal when placed beside the much thicker 1/16-inch (.0625 inch) rings of old.
Maylish says that what Mahle’s engineers discovered, was that because 9254 steel is just as flexible as it is strong, it can reduce ring cross sections, along with radial wall thickness and axial height, with zero loss in fortitude. That makes this steel material and the piston ring design that it spawned vastly superior to cast iron, high-strength ductile iron, and even gas-nitrided steel variants.
Microscopic distortions within the bore of a cylinder can wreak havoc on your compression and performance, hence the flexibility of Mahle’s piston ring design being so crucial. Mahle’s engineers say that anything south of 2,000 horsepower can safely benefit from this thinner piston ring design!
The Good Ol’ Ring Toss
MAHLE Motorsport knew that it had to go beyond just space-age steel and a superior, much thinner piston ring design. So to finish things off, Mahle concocted its own custom cocktail for coating the faces of each piston ring, which it refers to as its proprietary “HV385 Thermal Spray.” Scuff resistant, with excellent bonding strength and low friction coefficient ratings, this magical elixir adds a final layer of armor to each piston ring for fast, reliable break-in and sealing advantages.
Speaking of break-in periods, George Wright, the Applications Engineer from MAHLE, says that these thinner piston rings break in extremely quickly. That being said, Mahle does still recommend following its suggested break-in procedures for optimum results. Apparently, this methodology is very similar to traditional break-in procedures, but with a far tighter seal being the end result.
Naturally, reducing parasitic loss and producing power remains a top concern when it comes to engine internals. Having a design that can consistently create real-world power and still do its job as a vital core component within a motor truly is the best of both worlds.
That’s why, in 2019, EngineLabs conducted its own independent test of Mahle’s piston ring sets. During this experiment, we pitted these slim metal slivers against thicker, more conventional designs and documented our findings. The result? A consistent bump of 9 horsepower and 15 lb-ft of torque!
Mahle explains that the reason for this bump in power is due to its lighter weight and superior design. The fact that a thicker piston ring can cause the ring pack to extend into the wrist-pin bore doesn’t help much either. For to keep the oil ring from allowing seepage along the barrel of the piston, a spacer must be implemented, which just adds additional mass. Furthermore, certain applications can take a thinner piston ring, and allow its unused real estate to provide a deeper valve pocket to be formed, which results in greater clearance levels from the wrist pin.
A Thinner Piston Ring Pack Has Far-Reaching Implications
When it comes to MAHLE’s latest line of pistons, those slimmer piston rings sure have made a massive impact on the design and reformation of its lineup. For instance, the thinner ring allows materials from certain areas to be removed and then repurposed in other areas for additional strength, or allows their removal entirely. The result is a far stronger and lighter forged piston. How much lighter? Try 29 grams, on average, versus Mahle’s previous forged piston design.
According to Maylish and Wright, PowerPak Piston Sets offer an affordable, readily available upgrade package for a slew of applications. Naturally, there are a ton of different piston designs and power configurations to choose from, as each application is uniquely conformed around the project at hand, as well as its intended purpose. That’s why, for custom piston applications, it is best to contact MAHLE via email at motorsport.tech@mahle.com for a bit of guidance on getting the right piston and ring package.
Mahle’s determination to help engine builders, race shops, OEs, and engine rebuilding businesses benefit from its devout interest in producing the best parts possible is both commendable and impressive.
Now as for the piston rings themselves, it’s safe to say that these advancements in piston ring design have already revolutionized the automotive arena. And while the new alloys and coatings may be widely recognized for their hardness and higher tensile strength, their ability to provide greater flexibility when applied to a cylinder wall is irrefutably important. For it is here that heat dissipation improves dramatically, and with that comes higher yield strengths, greater resistance to fatigue, and you got it, more power.
And while there are even thinner rings out there, the cost associated with that reduction in thickness is exponential. That makes the 1 mm piston ring design by MAHLE Motorsport the ideal balance between cost value and performance.
