The point of the wrap is to keep the heat in the exhaust gas to get a faster velocity. This will have the effect that it causes the pipes to get/stay hotter aswell. Even if the pipe is ceramic coated you can retain even more heat in the gas by wrapping the pipe.

From my understanding of metalurgy (and I admit it's not great) the wrap would not be determental to the strength of the headers as instead of the headers going through several heat cycles everytime the engine is making power the heat in the headers would be more constant, though admittedly hotter. Also it would be cooling down a lot slower so the headers would not harden as much due to quench (I suspect this would be a minimal, if any, effect), though as I say, I'm just guessing here.

yes but the point is with wrap, you have increase the risk of running hotter in some spots where you've wrapped more than other spots, probably causing more wear on the metal due to the temp differences

So what about differences in the thickness of the coating? You can be guaranteed that there will be some and also you can be guaranteed that the bends are not the same thickness as the rest of the pipe, so that explanation doesn't really fly with me.

It just sounds more like the usual stories rather than being based on any real fact.

Word of Advice

when putting th VHT paint coat on to the heat wrap fabric, the wrab becomes stiff and a little brittle. try not to rub it up against anything if your installing the manifold back onto the car. especially if your installing a new motor with the manifold already installed from the top.

Lesson learnt for me!

[QUOTE=foxey]So what about differences in the thickness of the coating? You can be guaranteed that there will be some and also you can be guaranteed that the bends are not the same thickness as the rest of the pipe, so that explanation doesn't really fly with me.

It just sounds more like the usual stories rather than being based on any real fact.[/QUOTE]

no it most probably wouldnt, agreed. But regarding coating - we might be talking microns.. with wrap - depending how much times u wrap it over - we're talking millimetres thick differences. has to account for something.
Dunno this is all speculation - id like the proof too.

I heat wrapped a set of headers on my SR20DE Pulsar (can't remember the header brand but cost about $550 at the time and looked failry decent quality) with Thermotec bandage mainly to protect the other componenets in the engine bay as the heat shied was removed.
After about 9 months I started hearing some noises and had them inspected. Returned to the workshop to find that all the welds had crystalised and cracked with the heat and they pulled out the headers in over 12 pieces!
They replaced them with another identical set which I didn't wrap and they have been on for 7 years now.

Guess quality does matter, but the increase in heat will ultimately effect all metals to some degree.

in my opinion if no factory performance car has one then i'm not putting one on mine either, and i've never seen/heard of any factory car being heat wrapped. not even something like a veyron with 4 turbo's gets it

[QUOTE=trusti rex]in my opinion if no factory performance car has one then i'm not putting one on mine either, and i've never seen/heard of any factory car being heat wrapped. not even something like a veyron with 4 turbo's gets it[/QUOTE]

Guess the Lambo engineers shouldn't have ceramic coated the exhaust on the Reventon or the McLaren F1 doesn't need the gold lining in the engine bay for heat issues...

[QUOTE=Kato]Guess the Lambo engineers shouldn't have ceramic coated the exhaust on the Reventon or the McLaren F1 doesn't need the gold lining in the engine bay for heat issues...[/QUOTE]


heat wrapping does not equal ceramic coating. coating has been proven to work and like you say, is used by some factories, wrapping has not. easy!

[QUOTE=trusti rex]heat wrapping does not equal ceramic coating. coating has been proven to work and like you say, is used by some factories, wrapping has not. easy![/QUOTE]

Ok so why do so many race teams use it to increase performance? It is after all an insulating layer the same as ceramic coating. Ceramic coating is better (why it is used in exotics), but it doesn't detract from the performance gains of heat wrapping.