Re: Exhaust/Manifold wrap - Question

["David R Johnson" <johnsnd@xxxxxxxxxxx>]

On Jan 13,  5:04pm, Jess Liao wrote:

> Any down side effect for wrapping the manifold?
> I know that exhaust temperature will increase, I wonder if the increase
> is significant to cause cat converter to over heat? Any other effect
> to the engine?

A word of warning for anyone using this kind of wrap.  I have heard reports of
it resulting in engine fires.  Nothing has ever been proven since the fire
destroys the evidence, but this is the experience of at least 2 Camaro owners
that I know through another mailing list.

The problem is that the wrap readily absorbs oil and transmission fluid.  While
oil is normally not that easy to burn, it seems that when it is distributed
within the fibers of the wrap it can be ignited with sufficient heat, which of
course is provided by the headers (I'm guessing this works rather like flour
explosions in bakeries).  One list member showed the potential risk by soaking
some wrap in oil and wrapping it round a steel tube, which he then heated with
a blowtorch to simulate the indirect heat of the exhaust.  The wrap
spontaneously ignited rather quickly.

Of course this is not a very controlled test, but combined with two suspected
car fires it was enough to convince many of the danger.  These experiences
occured using tubular headers I believe, and it is possible that a thicker cast
manifold would reduce the risk somewhat.  However, a safer option (and more
pricey of course) is to have a high temperature ceramic coating applied.
 Although if you are going this far you might as well get coated headers.  Cast
iron manifolds heat up the engine bay much less than tubular headers, and so
typically people do not worry about wrapping or coating them.  I would not
expect much of a performance gain in any case unless your underhood temp is
high enough to cause detonation, altough I suppose a hotter manifold might
result in improved exhaust gas scavenging.  Certainly the claims you are
quoting are hard to swallow and sound like typical sales BS.

> Actually, when I picked up the box of wrap, I just wanted to wrap the
> exaust near right rear brake caliper...

This seems like a very good idea.  I'm assuming the heat in the exhaust this
far back would not pose much of a risk.

Hope this helps.  All IMHO of course!

Dave J.
1982 GTV6

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