I believe Mazda
uses some Inconel hardware on the 93+ 13Brew engines…………found this out the
hard and expensive way.
Marc
From: Rotary motors in
aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of David
Leonard
Sent: Saturday, January 25, 2014 8:14 PM
To:
Rotary motors in aircraft
Subject: [FlyRotary] Re: Exhaust Leak at
Turbo Outlet Flange
Bummer! Glad you are safe.
I use the stock steel nuts. Locknuts might be an
improvement but not if there is any non-steel component. I did loose one
of those nuts once without to-do. Not sure how long it was gone.
The other 2 held everything together.
Be very careful with what gaskets you choose. I found
some nice-looking aftermarket turbo manifold gaskets for about $20 while the
stock versions are about $90 each, so I installed one. It lasted about
30 hours until it disintegrated. The resulting exhaust leak burned
through a coolant line and I dead sticked onto a local airport (departing
from a formation routine at an airshow!.. complete with a cloud of
steam).
Sigh, the stock ones are nothing but stainless steel
layer, not some sort of fiber stuff in the after market
ones.
On another occasion I was using some very nice and
expensive exhaust clamps that were steel but I didnt notice that part of the
block holding the nuts was aluminum. About 50 hrs in something caused
the alumimum to get too hot, which created an exhaust leak, which accelerated
the process. It burned a hole in the cowl and splatered molten aluminum
everywhere - some of it is still around.
Another time I was using some fancy exhaust
wrap. It slowly disintigrated over the course of 100+ hours and was
generally an annoyance.
I tried a flowmaster hushpower muffler but melted most
of the stuffing out of it on the first flight. Luckily it melted pretty
cleanly and didnt clog the exhaust.
Moral of the story.. as if it didn't take me long
enough to beat this through my skull.. NOTHING that is not made of
steel or better goes into any part of the exhaust system. Particularly
gaskets and nuts.
Guess I should have passed that one along sooner.
Glad you got back safely. Good job.
On Sat, Jan 25, 2014 at 5:14 PM, <downing.j@sbcglobal.net> wrote:
I had the nuts
come loose on my turbo manifold on the block, I'm using with out
the turbo, so I drilled the nuts and secured them with wire.
JohnD
Thanks for keeping us all informed , helps us all to make
sure we look for often simple overlooked areas.
Renises 13 b rv7
Sent from my
iPad
During the 8th
flight of my RV8 with 13B Turbo, I experienced an exhaust leak at the
turbo exhaust flange. I mistakenly used brass exhaust nuts which are
twice as tall as regular nuts. They work great on most engines. I should
have know better, as the temperature at the turbo outlet, under the
insulation is much higher.
The brass nuts
softened and deformed into a flange face at the washer! Once the tension
was gone, the heat & vibration did the
rest.
The exhaust gasket
blew where the gap was widest, at the top.
The escaping heat
burned thru the insulating jacket and the stick on reflective
aluminum. Then the fiberglass cowl charred, I smelled
that!
I was close to my
destination, and high, so I was able to pull off the power, put down the
nosed and get on the ground without
incident.
I'm disassembling
it now, looks like I need 4 high temperature lock nuts and a TO-4
exhaust flange gasket. I should review and improve the insulation over the
turbine housing. Also I need to repair the charred area of the cowl, which
might be in the form of an aluminum access
hatch.