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Wössner seem to have changed some of their piston skirt coating to red teflon. Its possibly only for steel sleeves. Anyone have any experience of these or dark coating lately? Especially in Alusil block?
They can modify their stock designs to fit 928 or do new design on order. Compression height change is largest change needed depending on what rods are used. As always, question is will skirt coating work on Alusil.
They can modify their stock designs to fit 928 or do new design on order. Compression height change is largest change needed depending on what rods are used. As always, question is will skirt coating work on Alusil.
Greg's experience says that not even established players in the market can.
Personally, I've had zero success with spray on coated pistons, in 928 engines.
Zero.
Nada.
I've also disassembled several super low mileage/super low hours 928 engines with spray on coated engines.
Every single one of these engines failed, almost instantly, from the spray on coating being "torn off" and the aluminum piston galling the Alusil bore.
That whole "silicon" part of Alusil is a very abrasive surface!
And, as I've mentioned, in another thread, even Porsche has had issues with the Ferroprinted pistons in the later model street 911 engines, even with the much less abrasiveness of the "new" Alusil bores.
As much as I hope that someone comes up with a viable alternative to the iron/tin coating that Porsche uses for the pistons in these bores, I'm really tired of wasting my own time/money trying different coatings.
Someone else is going to have to give this a try and prove, over a period of many miles, that anything else is viable.
I'd also want a written warranty, covering the cost of repairing a damaged engine, from any company who "thinks" their piston would work.
BTW...A discussion with Wossner regarding why they have offerings for almost everything but 928's would be necessary.
A 928 piston, because of the connecting rod offset, is subjected to a completely different set of loads than a 944 piston, which has a perfectly centered connecting rod, which greatly reduces that "side" loading of the piston.
NOTE THIS: I'm not saying that Wossner's red Teflon coating will not work...I have zero idea if it will.
I just became exhausted, many years ago, being the whipping post of trying all the different coatings that people swore would work, while also being the guy that was sent multiple engines with coated pistons which ran for minutes....not thousands of hours.
When Mahle USA's "printed" coating fell off (200 miles) and they refused to do anything, I was done with "spray on" anything.
Time for some other soul to spend multiple thousands of dollars building a 928 engine, only to have to start over spending more thousands of dollars.....Not to mention the hundreds of hours!
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
All these issues have me considering sleeving a 928 engine as a more prudent course of action with the lack of oversized pistons.
I just wish Mahle Germany could be bothered to make a run of pistons for the transaxle cars. But with such a small market there is no money in it for them
09-21-2023, 01:51 PM
Wossner piston red skirt coating
