Exhaust port coating?

[ATAl]

First a little background: This is for a 4age 20 valve turbo engine.

And my question:
Would a heat resistant coating (probably some sort of ceramic?) on the inside of the exhaust ports be a good idea or a bad idea on this engine?

Good:
Keeps the heat / energy in the exhaust, therefore more energy to drive the turbo.
Keeps the same heat out of the head and coolant, keeping everything cooler.

Possibly bad (just guessing about this):
Some of the coating stuff could flake off and go thru the turbo.
This may cook the exhaust valves.
The head may warp because of the exhaust side being cooler than designed for.

Anyone tried this before or got any comments?

[atmosports]

Yes have tried this before, can't really give any details of gains/losses(legal reasons) but needless to say there are plenty of other things I'd spend money on first as I'm pretty sure in the end we removed the coating completely & bead blasted the area with some coarse bead.

Use the same coatings as inside an turbo exhaust manifold the really high temp stuff, that generally only comes in one or two colours usually black. If it's applied correctly it should take ages before it comes off.Also just think of all the carbon & shit that is also going through your turbo.

If your gonna coat anything in an engine speaking for experience do the pistons & possibly bearings if you've got a decent coatings specialist to work with. I've worked with a guy up here on numerous stuff to perfect it for what we are doing & needless to say I've seen bearings out of a race motor after 2 seasons that are like new, when previously they were throw away after 3 meetings. But in saying that we did an awful lot of work on getting the properties we wanted in the coatings & then worked out how to apply them to get them to stick & also to get them smotth enough & thin enough for what we wanted.

[Mr Revhead]

coating the bearings? new one on me.

got any info on the web?

[atmosports]

It's a teflon based coating we used on the bearings, as in Main/Big end bearings & could do it to cam bearings etc. Needless to say we waste a few sets of bearing getting what we required initial we regards to the coating staying on, getting the coating thick/thin enough & constant thickness to be able to get the clearances etc. Don't know if there is any info on the web. Probably not as good as a DLC type coating but cheaper & obtainable here(well for me anyway), i would believe the coating we used to be similar to the teflon coating they use on piston skirts but I know there are some differences to get it to do what you need for bearings.

[Mr Revhead]

very interesting.
i can see cam bearing surfaces being a good use for it, as most toyotas dont have bearings in them and i often see an otherwise good head ruinde by scoring