3 Ways Modern Piston Rings Increase Performance

• Despite its small size, a piston ring (and the gap within it) is crucial to an engine&#;s overall function, especially in terms of oil distribution and crankcase pressure.
• MAHLE Motorsport North America was established in and has positioned itself as a leading supplier of forged pistons and rings in premiere motorsport series worldwide.
• MAHLE Motorsport modern piston ring sets are more durable, more efficient, and lower weight than its competition, yielding more reliable performance across various engine demands and operating temperatures.

Since the advent of the car, enthusiasts have been hunting for ways to improve performance. Today, the ever-swelling aftermarket industry is proof enough that this trend is more prevalent than ever. While off-the-shelf methods to unlock power (i.e. intake, exhaust, or software) will likely prevail as preferred upgrades, there have long been tactics that die-hard engine builders have utilized to extract every ounce of performance from their motors. Here, the quantifiable gains that commonplace upgrades afford become blurry, but for good reason: there isn&#;t a one-size-fits-all solution for power. As it is with most things, the devil is in the details.

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While more commonplace mods offer visual and performance lifts simultaneously, the more nuanced upgrades are most often hidden under the skin. Case in point, a typical enthusiast will choose a set of coilovers over a spherical control arm bushing, even if both offer tangible benefits. But the enthusiast we&#;re talking about today isn&#;t concerned with the &#;this or that&#; equation &#; it&#;s the car that opts for both.

AN HONEST ASSESSMENT

When engine builders have exhausted (no pun intended) all the engine performance options available, the only option is to consider how the car is going to be used. An exacting vantage point at this stage will allow a builder to make meaningful adjustments to the engine to extract maximum performance. For example, fitting a set of forged pistons could offer tighter cylinder-to-wall clearances and improved temperature stability, or strength for more detonation resistance. But there&#;s one component that offers its own set of benefits that is often overlooked: piston rings.

WHAT YOU NEED TO KNOW

At the core, a piston ring is like an open-ended &#;bracelet&#; for your piston. As the engine approaches its normal operating temperature, the gap in the piston ring will lessen as a consequence of the material absorbing heat. Here, its main function is to seal the combustion chamber to minimize gas loss to the crankcase. Tangentially, a piston ring will also ensure adequate oil exists in two crucial areas: 1.) between the piston and the cylinder wall and 2.) recirculated oil from the cylinder wall into the sump.

Ring gap is the available space between both ends of the piston ring at ambient temperature. This space can be adjusted so that it approaches full &#;closure&#; once the engine reaches its optimum operating temperature. In general, the smallest gap provides the best seal for combustion and prevents excessive blow-by. The result of this is more performance and reduced emissions. It is critical to observe the fitted gap at the operating temperature because, as aforementioned, the ring material will expand as heat builds. A gap that is too narrow is arguably more detrimental; at operating temperature, the ends of the ring may collide which can lead to ring deformation, bore scoring, or more severe engine damage.

Aftermarket performance manufacturers, like MAHLE Motorsport, will offer piston ring sets with predetermined gaps based on the engine&#;s application and performance use. 

IMPROVING THE STANDARD

MAHLE Motorsport pioneered the use of piston ring simulation and computer development tools to engineer rings that unlock horsepower by successfully minimizing friction &#; the bane to any forward propulsion. These tools, along with modern advancements in construction materials and coating technology, have led to another breakthrough: the &#;thin ring&#; piston ring set.

We spoke to Joseph Maylish at MAHLE Motorsport to gather expert insight on their latest technological innovation and three ways it leads to more performance, whether from increased efficiency or reduced friction:

Joseph Maylish, Marketing Manager at MAHLE Motorsport: Amongst older schools of thought, there are still strong beliefs that a 1/16&#;, 1/16&#;, and 3/16&#; ring pack is better than MAHLE&#;s 1.0, 1.0, and 2.0mm new &#;thin&#; rings. Few argue against the ability of thinner rings to free up horsepower in the right application, but the concerns are usually based on longevity and value: will these rings last, and are they worth it?

MORE DURABLE

Our modern ring pack is much more than just &#;thin&#;. The advancement of material and coating technology, particularly the widespread use of high-strength steel, creates a ring that is far more durable than any cast or ductile option. Granted, you can apply these advanced materials to any size ring, but that won&#;t overcome the cross-sectional area differences which allow the thinner rings to be lighter and more conformable. 

This means you can design for less radial tension to achieve the same or better sealing of combustion gases. Furthermore, less tension throughout all four strokes of the engine results in less wear on the face of the rings and less wear on the cylinder walls. Steel is also a better conductor of heat and can withstand longer durations of high-temperature operation without concern for the rings &#;losing tension&#;.

Contact us to discuss your requirements of Piston Ring Factory. Our experienced sales team can help you identify the options that best suit your needs.

LIGHTER + MORE EFFICIENT

The performance industry is driven by the continued evolution towards lighter, faster, and stronger components; piston rings are no exception. A 1.0mm compression ring can be up to 50% less mass compared to a 1/16&#; ring. That mass reduction has a 1:1 benefit: a 50% reduction in the inertia force exerted on that ring. In turn, sustained operation at higher RPM is smoother because of reduced ring flutter and with it, a more reliable seal between the ring and piston groove itself.

OPTIMIZED SEALING

What is often overlooked, is that the engine bore will never be perfectly cylindrical while in operation. The magnitude of this distortion may be difficult to perceive and is often measured in microns, but it is well within the range to allow cylinder pressure to escape the combustion space. When we add in distortion from mechanical loading and deformation, the conditions are only worsened. Older ring designs simply rely on brute force (tension) to overcome these challenges. 

The modern, more conformable rings are a cost-effective way to increase sealing, reduce friction, and ultimately provide a durable increase in horsepower and torque that engine builders and racers alike will agree is a win-win combination.

We want to thank Joseph Maylish of MAHLE Motorsport for his time and sharing his knowledge about their piston ring offerings. If you&#;re interested in learning more about MAHLE or its engine products, visit the company&#;s website for more information.

Gallery

Related

Before returning the rod set that we balanced, we offered to replace the rings, but the customer said they didn't need rings. We assumed that to mean he was replacing the rings with sets of his own. Instead he planned on reusing the old rings.

We always remove the piston rings and recommend to replace them. Also, we are very inclined to remove rings because the VW TDI has a tendency to have a ring-sticking issue. We make sure that the clearances are proper before returning pistons to service. The following pictures are typical as to what we see when removing rings.

Here is typical wear for a top ring:

The close edge of the ring break isn't clear, but you can see the amount of ledge that has occurred from the ring hammering in the ring land. There is a small ledge on the outside of the ring.

This is the same top ring as viewed from the edge.

A new ring is convex and the cylinder wall touches in the middle of the ring. That is a very unusual design, but seems to work very well for the Goetze rings that VW uses as OEM and we rebuild with.

Unfortunately, when trying to reinstall the rings, it is very likely that the ring will not seat well. We have had some who reinstalled used rings and complained about oil usage. Sometimes, after as much as 10,000 miles, the rings may eventually break in, but that is a risk that we don't like to contend with.

The next ring is the Second Compression ring.

As compared to the top ring, note that there is no ridge in the #2 ring from the same piston ring set. This ring is in very good shape, however, rings are replaced in sets.

Next is the spring behind the oil control ring.

This part of the spring has been flattened out and thinned. If the spring continues to wear, it can break, reducing the compression of the oil control ring against the cylinder walls.

Here is the #1 reason we are most often replacing rings.This stretched out ring is an annealed top ring.

The top ring is cast iron with a chrome plating toward the cylinder wall. The top ring can become so soft that it can be stretched out straight. A new ring could not be stretched like this, but would break if stretched more than a two-inch gap from the ends of the ring. This annealing happens when the ring receives regular over-heating, for example, from excessive high speed runs, continuous heavy acceleration, long hill climbs, over-fueling or uncontrolled fueling from nozzles, a sticking thermostat or a regular low water condition.

These situations will cause the cast iron to anneal, which is to remove the temper of the ring. This is a softening the structure of the ring, reducing it's springiness. That will increase blow-by and oil usage. The ALH and AHU pistons in particular, have an issue with the top ring placement that causes more heat to affect the top ring. Some of the alternative pistons, like the ARL or BHW have a ring land that is much further from the top of the piston that protects the top compression ring from excessive heating

The Goetze rings add about $100 to the cost of an engine overhaul. If you choose to leave the old rings in, you risk increased oil usage and possibly the chance that the rings will not seat. The risk is an rebuilt engine that burns oil.

Cylinder bores need to be honed in order to reestablish seating for rings. I personally would not take the risk, nor would I chance warranty repairs by returning used piston rings to duty that are questionable in any way. The rings we removed from those pistons last week were exactly that... Doubtful.

We got an angry call today from one of our customers, who told me in so many words, he never asked me to remove his piston rings from his piston. I'm wondering why he sent the piston. We always clean and prepare pistons for return to service, which includes removing the old rings, carbon removal and inspection for damage.Before returning the rod set that we balanced, we offered to replace the rings, but the customer said they didn't need rings. We assumed that to mean he was replacing the rings with sets of his own. Instead he planned on reusing the old rings.We always remove the piston rings and recommend to replace them. Also, we are very inclined to remove rings because the VW TDI has a tendency to have a ring-sticking issue. We make sure that the clearances are proper before returning pistons to service. The following pictures are typical as to what we see when removing rings.Here is typical wear for a top ring:The close edge of the ring break isn't clear, but you can see the amount of ledge that has occurred from the ring hammering in the ring land. There is a small ledge on the outside of the ring.This is the same top ring as viewed from the edge.A new ring is convex and the cylinder wall touches in the middle of the ring. That is a very unusual design, but seems to work very well for the Goetze rings that VW uses as OEM and we rebuild with.Unfortunately, when trying to reinstall the rings, it is very likely that the ring will not seat well. We have had some who reinstalled used rings and complained about oil usage. Sometimes, after as much as 10,000 miles, the rings may eventually break in, but that is a risk that we don't like to contend with.The next ring is the Second Compression ring.As compared to the top ring, note that there is no ridge in the #2 ring from the same piston ring set. This ring is in very good shape, however, rings are replaced in sets.Next is the spring behind the oil control ring.This part of the spring has been flattened out and thinned. If the spring continues to wear, it can break, reducing the compression of the oil control ring against the cylinder walls.Here is the #1 reason we are most often replacing rings.This stretched out ring is an annealed top ring.The top ring is cast iron with a chrome plating toward the cylinder wall. The top ring can become so soft that it can be stretched out straight. A new ring could not be stretched like this, but would break if stretched more than a two-inch gap from the ends of the ring. This annealing happens when the ring receives regular over-heating, for example, from excessive high speed runs, continuous heavy acceleration, long hill climbs, over-fueling or uncontrolled fueling from nozzles, a sticking thermostat or a regular low water condition.These situations will cause the cast iron to anneal, which is to remove the temper of the ring. This is a softening the structure of the ring, reducing it's springiness. That will increase blow-by and oil usage. The ALH and AHU pistons in particular, have an issue with the top ring placement that causes more heat to affect the top ring. Some of the alternative pistons, like the ARL or BHW have a ring land that is much further from the top of the piston that protects the top compression ring from excessive heatingThe Goetze rings add about $100 to the cost of an engine overhaul. If you choose to leave the old rings in, you risk increased oil usage and possibly the chance that the rings will not seat. The risk is an rebuilt engine that burns oil.Cylinder bores need to be honed in order to reestablish seating for rings. I personally would not take the risk, nor would I chance warranty repairs by returning used piston rings to duty that are questionable in any way. The rings we removed from those pistons last week were exactly that... Doubtful.

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