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Date:         Mon, 21 Jul 2008 22:53:36 -0500
Reply-To:     John Rodgers <inua@CHARTER.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         John Rodgers <inua@CHARTER.NET>
Subject:      Re: The DEEP, DARK secret of fiberglass exhaust wrap discovered
Comments: To: Chris S <szpejankowski@GMAIL.COM>
In-Reply-To:  <5ebe10a0807211924r7a7a3bf5w3ad678f7c1b8ab42@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

There is always a price to be paid when a change from the engineered design is made.And trying to deal with heat is a biggie! For exhaust systems in cars I'm not sure there is a good alternative to letting it all hang out in the breeze to utilize the moving air to carry away the heat.It's a bit like the problem that NASA had when trying to solve the re-entry problem of over heating the skin of the early space vehicles and the space shuttle. In the case they solved it by applying an ablative material on the nose and leading edges of things to dissipate the heat. Ablative materials are sacrificial materials that burn away and are not retained.They absorb heat, gasify then carry the heat with them as the gas dissipates.

With header pipes, collectors, and exhaust pipes they get really hot - I have seen them red hot at night on a hard run - and anything that keeps the heat in is going to help destroy them - shortens the life considerable. And any moisture that wicks it's way in - that just speeds the destruction.

John Rodgers 88 GL Driver

Chris S wrote: > Well, I bought some exhaust wrap, but not to wrap my exhaust, mind you. I > needed to shield some not-so-hot parts from the hotter-than-H parts. I've > read reports of exhaust headers rusting very quickly after application of > fiberglass exhaust wrap. Why? The stuff soaks up water like a sponge and > holds it. Yes, I just tested it. So you can imagine what happens over > night when the dew point drops, no? Yes. The doom of all bare steel, > moisture, gets sucked up against the headers. > > It seems that sealing it against moisture would be the correct way to apply > the stuff, which can be done by applying the appropriate and expensive > sealant. > > No problem for stainless steel headers, right? Maybe not so, since the wrap > causes the temperature of the headers go up, which may be too much of heat > stress for the metal to handle. And that might be another DEEP, DARK secret > in itself. > > Chris S. > > >


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