Ceramic coatings on pistons

[Oddmanout84]

I recently sent out a set of L28ET pistons to Swaintech for ceramic dome coating and anti friction coatings for the skirt. Yes, they're stock replacement CAST pistons, make fun of me all you want for dumping more money for coatings than the actual cost of the pistons. Couldn't see going forged for a street engine, but I wanted some extra insurance.

 

Anyway, I got a thought in my head the other day. Knowing that the ceramic coating not only insulates the piston from heat and in turn increases combustion chamber temps, could this be causing more unforeseen problems than it may solve? Namely, since my cylinder head and valves DO NOT have coatings, could the increased temps be increased and focused on my cylinder head, leading to higher coolant temps and possible detonation? I'm worrying that it was a bit dumb not to catch this before I sent my pistons out, but fortunately the engine is not back together yet and I still have time (though not the money at the moment) to get the chambers coated. I've seen threads on engines that have received these coatings and the advantages, but so far have not found much documentation on disadvantages (besides possible break-down and flaking).

 

If anyone is willing to shed some light on this, I'd be interested. That and if the coating is going to increase my combustion temps so greatly as to it being enough to completely throw off my Haltech's current tune.

[Brad-ManQ45]

Don't know about the rise in temp issue - most of it goes out the exhaust anyway, but if I were to get the tops coated, I'd make sure it is a 3 layer coating.

 

A single layer coating, which is what most everyone not in the aviation/racing business uses will flake of fairly soon.

 

It takes 3 layers with different expansion rates to keep the coatings on the piston.

 

Most expansion on the top layer and work your way down the scale closer to the piston.

 

Swain has their Gold coat that I believe is the 3 layer coating - I hope that's what you got...

[kiwi303]

As I understand it, the head and chamber (same thing isn't it?) has the water there to remove the heat, the bores have the water in the block, the pistons however only have the cooling obtained from radiation off their base and from oil splash, hence why modern turbo motors have oil squirters built in. Piston cooling via conduction to the bore via the skirts through the bore is difficult due to friction against the bore, even lubed there is still friction caused heat.

 

So the piston is the hottest part of the bore/head/piston combination, and is why most damage in a failing engine is to the piston. Coating the piston reduces heat soak into the piston, allowing the piston to cool itself better by oil splash and radiation of heat. This strengthens the piston, the chamber temps and bore temps show a minuscule increase in temperature unless the cooling system is already at it's limits. The coolant simply removes the heat so much more effectively than anything the piston has available.

 

So just coating the pistons is fine, there's no real need to do the chambers as well, just make sure your radiator isn't clogged.

[Oddmanout84]

Thanks guys. Yes, I got their Gold coat and PC-9.