Ed,
Is there any consensus at this time as to
which alloy (304 or 409) is the most
durable for our hot breathed 13B rotarys
??
--
Kelly Troyer
"Dyke Delta"_13B ROTARY Engine
"RWS"_RD1C/EC2/EM2
"Mistral"_Backplate/Oil Manifold
Kelly,
I'm not Ed but I
did sleep at a Holiday Inn Express!!
Alloys to use for
Rotary engine exhaust in order of decreasing desirability (and
cost)
1.)
Inconel
2.) 321
Stainless
3.) 304
Stainless
4.) 409
Stainless
5.) Mild
steel
Basically 409 is a
low chromium stainless designed for the automotive market, specifically for
exhaust tubing. It does not polish well and will develop a protective coating
of rust. It will live just fine, but will be less attractive.
If you move up in
cost you get a higher chromium and nickel content and therefore a higher temp
resistance and creep resistance. This means you can make everything lighter
and thinner. Of course it becomes much more important to properly design the
manifold for expansion/thermal cycling loads the thinner it gets. So you
will have to put a lot of slip joints and metal bellows in it to seal it up if
it is a turbo installation. So.....how much do you want to spend to save 5 lbs
or have a polished tail pipe is the question.
Mild steel will
work fine if it is thick enough. Especially if you coat it with ceramic. I
suppose you could also coat the 409 stainless with ceramic if you want a nice
finish, but it might be less expensive to just use 304 at that
point.
Monty