Nearly 25 years BEFORE Nicholas Otto invented the spark ignited internal combustion engine (the type of engine most cars use), an English Engineer by the name of John Ramsbottom invented the piston ring in , and he did it for steam engines. So, before we had cars or gasoline, the industrial revolution brought us steam locomotives. Prior to Mr. Ramsbottom’s stroke of genius, steam engine pistons featured grooves packed with hemp or cotton to improve sealing. Of course, this didn’t work that well, which led to John Ramsbottom’s invention of the metallic, split ring design in . Over the next decade, he continued to refine his design, and eventually a steam engine could go 4,000 miles before needing to replace the piston rings. That was a significant improvement in performance and durability. 170 years later, the piston ring is still evolving and enabling greater engine performance and durability.
Goto Dongya to know more.
Interestingly, Britain is not only the birthplace of the piston ring, but it is also the home of several of advancements in piston ring design. English engine manufacturer D. Napier & Son is often credited for the invention of Keystone style top ring and eponymous Napier style rings. Both developments took place during the ’s, and these designs are commonly used today in diesel and gasoline engines respectively.
If that wasn’t enough, the UK is also home of the most advanced piston rings, which are found in Formula 1 engines. With over 50% thermal efficiency, today’s F1 engines are the most efficient combustion engines ever built (rivaling combined cycle gas turbines). That’s nearly double the efficiency of a regular petrol engine and 50% better than a turbo diesel. The folks at Mercedes AMG made some videos about this achievement, which can be found on YouTube.
One of the reasons for the incredible efficiency of these engines lies in the fact that piston rings account for nearly 40% of all engine friction. That makes piston rings the number 1 source of friction in an engine, so the best way to improve engine performance and durability goes right back to Mr. Ramsbottom’s invention - the piston ring. The evolution of piston ring materials and coatings has allowed for innovation in piston ring sizes and designs. Today’s piston rings are dramatically thinner, lighter and stronger than your Grandfather’s piston rings.
For decades, cast iron was the material of choice for piston rings. However, the low hardness of grey cast iron, up to 22 Rockwell C, allowed for higher wear, which shorten engine life. The advent of hard Chrome plating allowed cast rings to achieve a face hardness of 72Rockwell C. These hard chrome rings lasted much longer, but were much tougher to break-in. This led to rougher cylinder bore finishes and many lubrication “tricks” that enabled the hard chrome faced rings to break-in.
By the ’s Plasma Moly rings appeared, which replaced the hard chrome face with a softer, porous moly face coating. The much softer Moly coating, 80 on the Rockwell B scale, did not require the rougher cylinder bore finishes or lubrication “tricks” to achieve proper break-in. However, the sprayed on “Moly” coating was susceptible to flaking in higher horsepower applications. Also, the cast iron or ductile iron base ring could only be so thin before they became too brittle.
As such, steel rings that feature PVD(chemically bonded) face coatings were developed in the early ’s, which allowed for thinner piston rings with greater strength than the iron forefathers.
With the advent of better piston ring materials and coatings, the potential performance of piston rings skyrocketed!
Because of the instant reduction in friction and increase in durability, professional racing teams quickly adopted the thinner, steel piston rings.
Here’s some real-world proof of that statement. Between my Dad’s 20 years in NASCAR as a driver and my 15 years working for NASCAR teams, I’ve seen the evolution of piston rings firsthand. Back in , the state-of-the-art piston ring package in NASCAR was an .043, .043, 3mm Ductile Moly set, and those rings lasted one 500-mile race. It was typical for the engine to be down 5 to 8 HP after that one race. Today’s NASCAR engines use .5mm , .6mm, 2mm PVD coated steel rings that last over 1,500 race miles without losing a single horsepower!
It’s not just racing engines that take advantage of thin ring technology. OEMs around the world have embraced the efficiency of thinner piston rings. A Chevy V8 used a 5/64, 5/64, 3/16cast iron ring package. 50 years later, turbocharged, direct injection engines making twice the horsepower per cubic inch of that old Chevy utilize 1.2, 1.0, 2.0mm steel rings.
More efficient piston rings increase horsepower, reduce engine temperature (both water temperature and oil temperature) and extends motor oil life. All of which means engine life and performance increase. I think John Ramsbottom would be proud to see today’s piston rings.
If you are looking for more details, kindly visit piston ring manufacturer.
If asked what you wanted for piston rings in your engine build, would you know how to answer? Piston rings have the most important job in your engine. We will get arguments on this one because there really are no unimportant parts in your engine. However, what makes piston rings so important is what they do.
The humble, hard-working piston ring dates back to when a man named John Ramsbottom demonstrated the friction-reducing value of piston rings along with the sealing and cooling benefits. Piston rings improved efficiency. In those days, it was more about steam engines and less about internal combustion.
Piston rings provide cylinder and combustion chamber sealing, which keeps heat energy contained where it belongs, above the piston. Any heat energy that escapes past the piston rings is lost power—period. Heat energy contained above the piston goes to work making power at the crankshaft. Piston rings also carry destructive heat into the water jacket via the cylinder wall to control heat and prevent piston meltdown.
What people want most from piston rings is cylinder sealing along with low tension to achieve less friction and better efficiency. It is challenging to get both. We live in an age of skinny, low-tension compression rings—sometimes as narrow as 0.023-inch, or 0.6mm. This works if you have perfectly honed cylinder walls. If you don’t, rings tend to distort and you’re not going to get optimum cylinder sealing.
Proper ring selection means understanding ring function, material, piston design, and bore dynamics. Pistons, rings, and cylinder bores must have a perfect marriage to function properly. Proper engine break-in is critical to endurance and reliable ring function. The type of piston ring you choose depends on how you intend to use your engine. Mild street performance engines call for a more “vanilla” ring package than supercharged, turbocharged, or nitrous-fed engines. Racing engines demand a much tougher ring package on par with what’s used for supercharged, turbocharged, or nitrous engines.
Which ring you choose boils down to how much heat and force you intend to impose on them. If your engine is bone stock as delivered from the factory, you’re probably not going to want to hear this. A box-stock engine is equipped with ductile iron and cast-iron piston rings. This means your rings are not going to like a supercharger or that occasional nitrous blast because stock ductile and cast-iron rings can’t always stand the heat and pressure associated with forced induction or squeeze.
If you’re opting for nitrous or forced induction, you’re going to need a top compression ring capable of withstanding the heat and pressure associated with these elements. This calls for high-end materials according to Ed Law at Total Seal. Ed suggests an AP Stainless top ring with PVD (Physical Vapor Deposition) for forced-induction and nitrous applications.
Total Seal’s high-performance piston ring sets include an AP Steel top ring that has been coated using PVD-applied C-33 chromium nitride anti-friction coating for greater efficiency. The C-33 coating is easy on cylinder walls while the steel top ring still has the ability to handle extreme pressures. Napier secondary rings and three-piece stainless oil control rings come standard with the AP Stainless Steel Ring Set.
As a rule, pistons and rings are generally sold in sets unless you’re reusing old pistons or are choosing a different type of ring than the manufacturer provides. Manufacturers such as Federal-Mogul Speed Pro from Summit Racing Equipment sell pistons and rings as sets for your convenience. This makes piston and ring selection a no-brainer for the average enthusiast. Just look at what the manufacturer suggests for the type of driving you intend to do and refine your decision from there.
An important consideration as to how well the piston rings seal is the hone of the engine block. Your machine shop should have a PAT gauge to accurately measure the final hone’s surface roughness. Total Seal says typical values (measured in microinches) for general performance applications should be around RPK 8-12, RK 20-30, and RVK 30-50. Is your local machine shop capable of this caliber of work? Not all of them are. If a machine shop can finish late-model Ford or GM stockers with their thin rings to maintain original emissions compliance and factory tolerances, the answer is likely affirmative. Confirm this when you drop the block and pistons off. CHP
Photos by Jim Smart
For more information, please visit Piston Ring Factory.