Finally!
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Skirt coating is permanent... something like the stock piston's anti-friction coating, it is not a wear in coating and it is meant to be on the piston for as long as it is in use. I don't know the specs on the effective thickness of the coating but it is obviously quite thin.
As I understand it from my reading dome coating is a ceramic heat shield which helps prevent localized hot spots by distributing the heat from combustion more evenly. This coating also helps keep the temperature of the piston and subsequently the attached wrist pin down as it is oil cooled and lubricated by a jet of oil from beneath the piston directed at the underside of the piston.
As I understand it from my reading dome coating is a ceramic heat shield which helps prevent localized hot spots by distributing the heat from combustion more evenly. This coating also helps keep the temperature of the piston and subsequently the attached wrist pin down as it is oil cooled and lubricated by a jet of oil from beneath the piston directed at the underside of the piston.
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So out of shear curiosity if you remove "coated" pistons from a high-mileage motor
is the black coating on the skirts gone and the light-grey (or whatever it is) on the piston crowns gone ? I'm wondering if that part is just for sex appeal. Of course, the true protection is still there, just transparent and looking like any other piston.
Lastly, are factory coated pistons black on the sides or is that just marketing since the owner of the car never sees the pistons going into the motor?
.
Lastly, are factory coated pistons black on the sides or is that just marketing since the owner of the car never sees the pistons going into the motor?
.
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factory pistons do have a coating on the sides, see my post at the bottom of this thread for pic
It was worn off pretty good in that picture but the set of pistons I took out of a normal driven motor with 155k miles had most of the coating in tact.
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Stock pistons are coated on the sides in patches... I have a set of stock 1.8T rods & pistons from a AWM... just like the piston Phil posted a pic of they have patches rather than a fully coated skirt.
As far as the dome goes, that will likely be covered in carbon so it will no longer be pretty and grey.
I'm not sure how thick an anti-friction coating needs to be to be effective in reducing friction between say the piston skirt and the cylinder bore.
So what kind of tea do you get at Peets?
As far as the dome goes, that will likely be covered in carbon so it will no longer be pretty and grey.
I'm not sure how thick an anti-friction coating needs to be to be effective in reducing friction between say the piston skirt and the cylinder bore.
So what kind of tea do you get at Peets?
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We used Mahle Coatings on everything especially friction coating. My machinist didnt like ceramic
coatings as he said he had had 2 instances where the coating flaked and destroyed the turbine wheel which screwed up a lot. He said that anything that was sprayed on and not absorbed could do this. He said that while it was not something that happened often at all (these were only 2 cases he knew of) that if it were his money he would just machine half a point from the compression ratio and let them go into the world the way J&E made them. We did cryo freeze all the internal engine parts, but only used the Mahle friction coatings which Dawes Motorsport of Porsche racing fame did for me. I know a guy who also ceramic coated his combustion chambers and exhaust valve ports thru the head. He also lost a turbo in grand fashion, he had been warned about doing the ports in ceramic, but ignored it and apparently paid for it. At the time we thought it a faulty turbo.
While it may not happen often, do you want it to happen to you, when you can do the same thing by tuning correctly and keeping the static compression down. BTW running some solvent thru the system will clean valve and CC deposits to the point you can avoid pre-ignition detonation.
While it may not happen often, do you want it to happen to you, when you can do the same thing by tuning correctly and keeping the static compression down. BTW running some solvent thru the system will clean valve and CC deposits to the point you can avoid pre-ignition detonation.
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