Thermal coatings

[Shannen Durphey]

Header wraps are not used for noise reasons in most cases.  The idea as I
understand it is to reduce heat loss early on in the exhaust system.  This helps
exhaust gases maintain velocity through the collector and (if included) exhaust
pipes.  Header wraps seem to work well for mild street systems with 3" exhaust
pipes.  True that the header does seem effectively smaller, but the idea is to
consider the system that it's a part of.  The same idea applies to cat back
systems, IMO.  Once the converter heats up exhaust gases the pipes after the
converter seem effectively smaller.  One thing I have noticed about cat back
systems is they generally do not reduce the diameter of the pipes after the
muffler.  If the muffler is far enough away from the convertor as to be a major
source for energy loss, I would expect that the pipes after the muffler should
be reduced in size.

Some points to remember.  Header wraps and coatings applied to the outside of a
hot pipe reduce the life of the pipe.  Yhis has been observed time and time
again, and is even discussed in the DIY archives.  As Bruce pointed out, the
only "real" way to apply coatings is to the inside of the pipes, and few people
take the time to do that.

Shannen

Arnaud Westenberg wrote:

> 
> > I have seen "header wraps", so someone must believe that it is
> > worthwhile to keep the heat in the headers.
> 
> I've seen/used them too, but mostly for noise reasons (in my case that is)
> 
> ___
> 
> Arnaud
> 
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