mikey_audiogeek

Dunno if this is relevant, but aluminium oxide (alumina) is technically a ceramic. I've seen parts made with "a ceramic metal matrix comprising 2 ceramic layers bonded to a thin metal substrate" which is marketing speak for... anodized aluminium.

http://www.harmanaudio.com/all_about_audio/Cmmd.pdf

Could any of the "coatings" on the pistons (visible or not) be anodizing?

Mike

Kpoeltl

Wossner supplies pistons with 2 different coatings (or with no coating). One coating is a simple anti-friction coating and that is what typically is supplied for engines with steel liners. If the bore that the pistons are to run in are Alusil, then Wossner applies a special coating called Molycote D88 which is actually a coating that was developed by Dow Corning specifically for Alusil bore applications. The standard anti-friction coating is gray-ish in color and the Alusil coating (molycote D88) is more of a bronze/goldish color. The Alusil coating (molycote D88) must be on the skirts in order to run successfully in Alusil bores. There is no need to coat the top of the piston as far as the Alusil bore is concerned. Some of my engine building customers order the pistons uncoated (when they are installing in steel liners) and have the piston skirts coated locally which explains some color differences that have been noticed on Wossner pistons.

mikey_audiogeek

That's good info. Thanks Karl!

boost feen

Does the semi slipper design of the Alusil piston along with the coating mean that the piston skirt is actually being kept from contacting the bore because of thermal activity. As in if there was no coating on the Alusil piston skirt they would expand too much and contact the cylinder wall?

V2Rocket

...where can the Molykote D88 treatment be done? Is it something a specialist would do or can it be applied by the user?