The center-center dimension between the Renesis end ports is 10.5" so if
   your main canister is limited to 8.5" long you have some creative piping
   to consider.  Perhaps centering the main canister to the center port
   with the end ports coming in at an angle yet still tangential is an
   option.  Paul included a 3D layout earlier in the discussion where the
   front end port elbowed into the end of the collector canister.  That may
   be an option for you too.  Perhaps Paul can provide further guidance on
   this as I am new to the tangential design.  I find it intriguing and
   possibly having potential for some non-aviation uses.

   Some of the systems I've described are really more of a tangential
   header manifold than a muffler.  I'm contemplating designs for a Mazda
   RX-8 race system which will include piping toward the rear of the car
   fitted with several stainless scrubble-packed lightweight racing
   mufflers available from Burns Stainless etc..  The car will still be
   quite loud even with these, though not nearly as much as most aviation
   applications.  In a few event locations there are specific sound
   controls that must be adhered to so any additional damping that can be
   provided at the exhaust manifold is welcomed, but not paramount for my
   intended application.

   Mark Sipe

   Those Burns Stainless mufflers are just what we are looking for.
   a 2 1/2" inlet is  3 1/2" in diameter and 17.1 inches long and
   weighs just
   2.7 pounds. Cost $216.75. What a bargain. I don't know the SS
   alloy but it could be 321. I'll bet they will make them
   in Inconel if you ask as they are now selling Inconel
   tubing.

   www.burnsstainless.com <http://www.burnsstainless.com>

   Paul Lamar ...No rotor no motor.

I have one of those Bruns Mufflers.  The "ceramic" packing lasted about
an hour before it turned to glass beads, and that was with the turbo
softening the exhaust.  I am still using the SS housing, but I am not
sure if it does anything.  It has lasted for 70 hrs. with only minimal
deterioration.  I think it is polished 304 SS.

The muffler will probably last longer on a car where the exhaust has
time to cool off

While Burn's sell Inconel pipe, the largest diameter is 1.5" or
something.  I once called and asked them for a custom bend of a 321 pipe
in 3 inch diameter (because the website says to ask about custom
stuff).  They practically laughed at me.  They seem only interested in
large custom orders, if that.

I just ordered a brand new Flowmaster Hushmaster II muffler from e-bay
for $125.  They are streamlined and Tracy says his has held up very well
and has a minimal effect on power.