Subject: rotary engine in Mustang II
From: rotaryeng
Date: 9/22/2014, 10:38 AM
To: AA-1-Me


   You need to shorten the intake  runners to 18" to 20" engines for
   more power
   with a 2.85:1 PSRU. Take off RPM  will be 6500 to 7500 engine RPM.

     Also you will need my cooling  book.

   Shield the lower left motor mount  bushing  with ss from the 1500 F
     exhaust pipe.

     Paul Lamar

     Jake, thanks for the pics. It is sad to see such potential
     in a project  go unfinished. Let's hope you get a good deal on the FWF
     package, and   get another rotary in the air.

     Steve Carlisle

   Thanks for the info,  what is your cooling book?
   How would you shorten the intake runners with the air intake on the
   right side like it is?  How much power difference would there be?  I
   was planning on wrapping the exhaust pipes and will plan on a sheild
   for the motor mount.

   Jake

   The plenum is unnecessarily large. Move it to the top of the engine
   something like this.
   You will save weight too :)

   This is a P port but an optimized  side port will work too only
   about 50 HP less.

   With the intake runners as long as they are now you will be about
   165 to 180 HP. You should
   get 200 HP with an optimized side port engine, 2.85:1 PSRU and 18"
   runners at 6500 to
   7500 take off RPM. With a P-port you would get 250 HP.

   There are now better mufflers than that shown in these pictures and
   3D's.

   http://www.rotaryeng.net/cooling.html

   I also sell the book direct for cash  $30 + $5 shipping in the US.
   More shipping
   over seas.

   Paul Lamar

HI Jake,
With all respect to Paul's opinion on what you should do, I would like to share my opinion.  Paul is correct that you will get more power from shorter intake runners.  But the difference in power is not nearly worth the vast amount of work it would take you at this point to accomplish the change.  It would require changes to the cowl, building a new plenum, relocating the injectors and throttle body, changing the cold air intake system, and possibly building a new engine mount.  It is much better to be flying an airplane with adequate power (while not as much as its potential) than it is to spend years not flying.
Paul is also correct that the engine mount needs shielding. However, I would discourage you from wrapping the exhaust.  I used to do it but don't anymore.  The problem is the high duty cycle and extra hot rotary exhaust.  First problem is that there is no wrapping material that will hold up for very long. Standard exhaust wrap with  start coming apart on the first or second flight.  The really expensive stuff wont last much past 100 hrs.  It stinks as it burns. It is a pain in the arss whenever you have to do maintenance or inspections of your exhaust system (and you will want to be inspecting it frequently).
Further, it retains the heat in the pipe.  That makes it oxidize away much faster.  Also, because the metal is running at a significantly higher temperature the metal will warp and fatigue much faster.  Welds in particular will not last long. Trust me, I learned all this the hard way.  You see a lot of pictures of installations with pretty exhaust wrap, but those are the 'before' pictures, taken before putting a ton of hours on the plane or race car.
Wrapping works fine for a street vehicle, and in race cars they just replace it after every other race.  You don't want it in your airplane.
Ceramic coatings are better.  They prevent oxidation and allow inspection.  They do still raise the operating temperature of the metal and they don't last forever.  In my opinion they are not worth the hassle and expense but not an unreasonable choice.
The shielding you use need not be exclusively stainless steel.  If closer than about 1" to the exhaust pipe it should probably be steel, but aluminum works fine further away, especially if there is decent air flow in the area.  At that point you are just fighting radiant heat.  In fact, you will find that a layer of aluminum foil bonded to the inside of your cowl on the hot side of the engine is indespensable in keeping the fiberglass from getting too hot.
Good Luck,
David Leonard
Turbo Rotary RV-6

 To add to what Dave said wrapped exhaust can and has  caused a crash. Also make sure the flanges
are correctly welded to the exhaust pipe. The RX8 engine is less critical as the exhaust
is 100 to 200 F cooler.

Paul Lamar

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