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Crowning Glory – Coatings Make Great Pistons Even Better

Sponsored by JE Pistons

Piston crown coating is a surprisingly affordable way to increase engine efficiency, horsepower and durability.

It’s often said the internal combustion engines, which hold a special love/hate place in our heart, are basically air pumps, and while that’s a useful mental model when considering many aspects of how they operate, it’s more accurate to say they run on heat. Heat, in the form of burning fuel, is what does the work, creating the pressure to move pistons down the bore. But the dirty little secret for all piston engines is how little of the actual heat energy contained in the fuel gets turned into useful work – a powerplant engineered and tuned to extract maximum efficiency out of every drop of gasoline burned will still throw away at least half of the potential energy, and somewhat ironically, “high performance” engines designed for maximum power output with no regard to how much fuel is required will lose as much as 75 percent.

In an ideal world, all the lost heat would stay in the combustion chamber, but in practice, half of the wasted energy goes straight out the exhaust port, while the other half ends up being passed through the cylinder head, the walls of the cylinder and through the top of the piston. The most critical phase of the combustion cycle occurs when the piston is up near top dead center – temperature and pressure are at their peak, and only a sliver of the cylinder bore is exposed to it, while the combustion chamber in the cylinder head and the piston crown are taking the brunt of that hot abuse.

Thermal barrier coatings are a practical and affordable way to increase the efficiency and durability of almost any engine build.

This heat is the enemy of longevity, especially in racing applications where high horsepower and lean mixtures can anneal (soften) the crown material to the point that it loses integrity. Ceramic crown coatings can greatly help combat this damaging heat, and JE’s Nick DiBlasi, was happy to give us the full details.

There are three ways heat can move from one place to another – convection, conduction and radiation. Convection is what happens when air, water or another intermediate liquid or gas carries it from the source to a cooler spot. Conduction is heat moving directly through a solid. And radiation is the heating of an object via infrared light, like the sun shining down on you.

All three are in play to some extent when heat travels into and through a piston, with hot gas swirling in the combustion chamber and radiated heat being absorbed by the piston crown, which then moves via conduction outward and eventually into the rings, oil or cylinder walls.

When an uncoated piston is exposed to the extreme heat of combustion, that heat can anneal or soften the crown. Ceramic coatings help reduce that effect.

“Ceramic coating, when applied to the tops of pistons, acts as a reflector of heat minimizing its absorption into the piston,” DiBlasi explains. Reflected heat gets less of a chance to warm up the piston in the first place, providing a first line of defense.

“In addition to the reflection, ceramic properties limit its conductivity of temperatures in general,” he continues. “Heat has to make its way through the coating, then through junction between the coating material and the piston top, and even though it’s very thin, the coating provides a worthwhile amount of thermal insulation to reduce how much of what is absorbed then continues into the body of the piston itself.”

When turbochargers, superchargers, or nitrous are involved, combustion temperatures skyrocket. Ceramic coating helps to extend piston life in these environments.

Speaking of thin, just how much material is added during the coating process? Per DiBlasi, “Ceramic coating is typically applied at .0005˝ to get the maximum results for piston applications.” To give you an idea of scale, human hair ranges from 0.006˝ to .002˝, copy paper mics out at around 0.004˝, and normal aluminum foil is just under 0.008˝ thick. Coatings add an insignificant amount of height to the top of the piston, so JE’s thermal coating is compatible with pretty much any piston dome or dish shape, as well as features like gas porting. DiBlasi says, “Since the ceramic crown coating is only .0005˝ we do not have to adjust any design characteristics when adding it.”

Fortunately, unlike some custom piston upgrades or options, ceramic crown coat is appropriate for all kinds of applications. “One of the great benefits of ceramic coating is that it is so universal,” DiBlasi explains. “We have huge success using this in all types of applications. We apply it on pistons for forced induction, nitrous oxide and naturally aspirated applications regularly, and have tested it on all fuel types. In order to ensure compatibility with whatever customers might throw at it, we have done extensive work creating ‘worst case’ scenarios in an attempt to make the crown coating formula fail so it won’t cause a problem for the end user. We go through a rigorous testing process to ensure we are getting maximum adhesion and benefits.”

Because ceramic crown coating is thinner than a human hair, it can be applied to any piston without requiring any changes to the crown or combustion chamber design.

Overall ceramic crown coating is good insurance for the racer pushing the edge, especially in the forced induction and nitrous realms. In naturally aspirated environments, the additional heat reflected into the chamber can even improve exhaust scavenging that returns real world horsepower!

This article was sponsored by JE Pistons.  For more information, please visit our website at www.jepistons.com

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