Get Thin with Smaller, Thinner Rings
MAHLE’s New HV385 1.0mm / 1.0mm/ 2.0mm Piston Ring Package
It has been said that you can’t be too thin or too rich, but when it comes to piston rings, thin is definitely in and the best news may be that you don’t have to be rich to take advantage of this new technology. It wasn’t all that long ago that production engines came with heavy, thick, and clunky compression and oil rings that did an adequate job of sealing for approximately 50,000 miles. Thankfully, technology has not remained stagnant. What was once thought to be beyond difficult is now a reality. MAHLE’s advanced production technology is right there at that leading edge. Just a couple of decades ago, a compression and second ring thickness of 5/64 (0.078-inch) was acceptable, with an even wider oil ring of 3/16 (0.1875-inch). The problem with these thick rings is that they increase drag considerably and demand greater radial tension – the pressure pushing the ring outward – to adequately load the ring to seal and control oil against the cylinder wall.
The innovative engineers at MAHLE have created a new piston that features much thinner rings while maintaining incredibly tight tolerances. The fruit of all this effort is a new piston and ring package designed to utilize 1.0mm (0.039-inch) top and second rings. This is exactly half the thickness of ancient 5/64-inch rings. This technology also applies to the oil ring, which is now a mere 2.0mm (0.078-inch) - less than half the thickness of 3/16-inch oil rings.
There are multiple advantages to this “get-thin” approach. The most important is an enormous reduction in engine friction. A majority of the power required to spin an engine at speed results from the effort demanded to move the pistons up and down. If we single out piston friction, 70 percent of that load is created by the rings sliding across the cylinder walls. By reducing the thickness of all three rings, friction is dramatically reduced. Plus, a thinner ring offers greatly reduced contact area where it touches the cylinder wall. This means ring designers can reduce the radial load because the contact patch has been cut in half. This results in a dramatic reduction in friction – which results in improved flywheel horsepower.
Another critical advantage to thinner rings is improved ring seal. It’s acknowledged that when loaded, cylinder walls are subjected to enormous pressures, which affects concentricity and distortion of the walls. A thinner ring package has an improved chance of maintaining ring seal due to greatly increased conformability, which means more of that cylinder pressure will be used to create torque and horsepower. To these improvements in ring seal we can add the advantages of better ring materials –a 9524 carbon steel alloy base material is used, combined with MAHLE’s new HV385 coating on the top ring that is applied using their supersonic thermal spray process that offers less friction, increased durability, and greater bonding to the base material.
The use of thinner rings in nothing new. Race engine builders have understood these concepts for years. All these ideas are excellent examples of how racing technology can be directly applied to street performance engines to improve ring seal, and efficiency while enhancing durability. This 1.0mm/1.0mm/2.0mm piston and ring package is not just for a select few engines. MAHLE has committed to produce an entire line of piston and ring assemblies for a wide selection of engines including the small-block Chevy, LS series, small-block Ford, Ford Mod engines as well as the small-block Mopar and the Gen III hemi engines too. MAHLE’s latest 2015 Product Guide lists specific applications for hundreds of bore and stroke combinations.
MAHLE operates the largest piston manufacturing operation in the world and its U.S. Motorsports division is located in Fletcher, NC. For more information on these new rings and pistons, contact MAHLE at 888/ 255-1942.