REFLECTOR:Re: Exhaust system

[Jim Sower]

<... You are putting on the same exhaust system that you have already proven is unsafe
....>
The short answer is no.  This is the part I was a little reluctant to share, absent a
direct question, but it appears I can't get out of it so I might as well get into it
.... :o(

When the airplane came my way it had kind of raggedy looking steel exhaust.  Last year
at annual I found cracks so I replaced it with SS unit.  Flange just barely did fit
and pipe end fouled the exhaust nipple in the lower cowl so I had to bend it.  Bending
SS pipes is not a trivial matter.  Anyway, this year I got snatched up short at Rough
River about flying around (nearly) full rich because CHTs went up way too high if I
leaned the engine, so I redid most of the baffling and sealed everything up including
the exhaust pipes near the nipples.  CHTs were still way high, so I inspected the
pipes and wrapped them with exhaust tape (the asbestos looking stuff you get at hot
rod shops) so I wouldn't be pre-heating the cooling air so much in the plenum.  It
worked marginally and I then solved my CHT problem for the most part another way
(that's irrelevant so I needn't share :o).

Anyway, taping the pipes is going to make them retain a lot of the heat that used to
conduct out into the plenum, so the pipes will be a good bit hotter than without wraps
and will not live so long.  Figured I'd pull the wrap at annual MINIMUM and check for
cracks and hints of cracks.  Stuff was only on there less than 10 hrs when pipe broke
off, and there were other nearly and minor cracks on the part of the pipe that
remained.  The pipe on there now is a steel unit that I am going to exchange with
Valerie for the SS unit when she gets one in.  I will then be able to do a good
comparison of CHTs with and without wraps.  If they aren't dramatically beneficial I
will pull the wrap off the port side pipe.  If they are, I will downdraft the f%*^($
airplane.

So now you've heard "... the rest of the story ..." :o)  ... Jim S.

KeithHallsten wrote:

> Jim,
>
> I'm happy to hear that your recent exhaust failure didn't result in a more
> serious incident, but. . .
>
> You are putting on the same exhaust system that you have already proven is
> unsafe?!?!  Say it isn't so!  It seems to me you should be doing some
> serious thinking about designing a more reliable exhaust system.  You might
> start with talking to Clint Anderson at Custom Aircraft Parts (see
> http://www.customaircraft.com/).  He built a custom exhaust for my IO-540
> that I believe will be much less prone to shedding the tailpipe through the
> prop than the Velocity exhaust, for about the same price.  The life you save
> may be you own!
>
> Keith