Are piston coatings going to save you from a bad tune, and if not, what’s the point? MAHLE Motorsports engineer Eric Grilliot answers these questions and more during a Performance Industry Trade Show visit.
Discussed are how different coatings can look identical to the naked eye but will often have different purposes and intents between manufacturers and also locations on the piston. Top Fuel piston coating vs OEM vs racing and even street applications are touched on along with why different areas of the piston might be focused on, or in the case of Top Fuel Drag Racing why it is beneficial to simply coat the entire piston.
MAHLE prefer a hard-anodized coating over Nickel Plating, and interesting the method and thickness is the same regardless of the application, it is more the locations where the coating is placed that become important particularly when it comes to managing heat in a modern piston design which seels the rings much closer to the crown.
The 3 main areas pistons are coated are the crown, ring groove and the piston skirt, and Eric explains what the coatings specifically help with in relation to the ring groove and skirt, including in relation to oil film. Machining requirements are also covered and interestingly in the case of MAHLE pistons there are no extra calculations required, the specs that come with the piston off the shelf are what the machinist should work too as the coating is accounted for in the original piston design rather than an afterthought.
There are many more topics packed into this interview including how piston coatings are not black magic that will save you from a bad tune but how they will buy your engine a little more time, how the heat management properties can give you a slightly bigger tuning window and why that doesn’t also translate to tighter tolerances. Micro welding is also explained along with the damage it can cause to your bores and if the coating should last the life of the piston.
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