OT: Thermal coatings

[Arnaud Westenberg]

Hi all,

Sorry if this is way off topic, but I'd realy like to hear some _not so 
humble_ opinions of you guys about thermal coatings.

They seem to be able to coat nearly everything so I'll list some of the 
possibilities and my questions/opinions about them.

First, piston, valves and combustion chamber. Obviously less heat loss 
and lower part temperatures, but also higher compression end-temperature 
and perhaps reduced VE. Does the higher flame speed make up for the 
increase of compression end-temperature and therefore reduce the 
probability of detonation? I assume, (yeah I know) that average temp in 
the combustion chamber will be higher hence reduced VE, or is this a 
faulty assumption and does temperature simply vary more over a single 
cycle? If it's true is this (over)compensated by the increased thermal 
efficiency? All webvertisements would make one believe so.

Second, exhaust headers. Disregarding turbocharged engines, I see little 
gain here. Less heat transfer would result in higher gas velocity but 
also higher BP, meaning you simply have installed a smaller diameter 
pipe?? Some webvertisements say less friction at the pipe walls hence 
better laminar flow. This must be a joke right? The exhaust flow is a 
fully developed turbulent flow isn't it?

Third, the intake. Now here I can see some gains. If one coated the 
inside of an intake there would be less heat transfer to the intake 
charge, wich is obviously a good thing. However, I haven't seen websites 
advertising thermal coatings on an intake, though I haven't specifically 
searched for them. Isn't this used?

Thanks,

Arnaud

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