Bruce:
Actually, my posts we kinda generic in nature and I really only responded
to Alan's post. In any case, I can see your point but I have some problems
with the logic being applied by the manufacturers.
Problem #1: It seems to me that if they are having them "coated" in
ceramic coatings, doesn't that count as a "wrap"?
Problem #2: The internal ceramics keep the heat from the exhaust away from
the steel, and the external coating keeps the heat away from the engine
compartment (and being touched by humans: OUCH++) Those coatings make sense
but would seem rather thin to me by comparison of a heavy braid (maybe 1/4
inch) which would allow you to touch and hold a header even while the motor
was running.
So here's the line of logic I'm using (right or wrong):
Exhaust = temp X
A header should be designed to handle temp X normally.
A coated header handles temp X - coating heat transmission factor
ie: header sees less heat from exhaust.
A coated header with further external protective braid will restrict heat
dissipation (of course) but, in theory, it should still never get any hotter
internally than temp X at the absolute maximum and the realistic number is
that it should never get any hotter than temp X - internal coating heat
transmission factor. The heat should remain in the exhaust and not be
transferred to the header (which might bode poorly for the Cat but...). So
the net result is that the steel of the header cools down more slowly when the
motor is shut off but never gets as hot as an unprotected header.
I can not admit to any expertise or experience in this. I'm only appling
rules of thermodynamics. No matter what, if exhaust is 800 degrees (only a
number guys, I don't know what it is) then the temp of the header can never
exceed 800 degrees no matter what it was coated with, and a header
manufacturer should make their component to withstand 800 degrees to begin
with so voiding a warranty based on heat dissipation problems sounds like a
load of garbage to me. They would have to prove how the modification
"damaged" their header so that it failed, just as any auto manufacturer would
have to do the same for all these mods anyway. If anything, the slower
cooling of the header would keep the steel more plyable and flexible rather
than brittle from faster cooling.
The corrosion problem is another issue, but since I'm assuming the header
has the ceramic coating on it prior to putting on the braiding then moisture
should be irrelevant as the moisture should never be able to touch header.
Shaun
Tustin, CA
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