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       12  c

   The Rotec/Ellison carb is quite expensive at over $300 as I recall.
   If you have a lathe and a mill you can make your own
   side draft 2 barrel car using a low cost Holly float bowl.

   This is designed to work with a two rotor P-port and slide
   throttle.

   Here are some 3D's.

   A  marine outboard engine has a self contained ignition
   system. It does not require a battery or  alternator or voltage regulator.

   One or more of these devices that can fail and cause the engine to stop if you
   are using an EFI and automotive the ignition. The TTC has given
   us trouble for that reason. If the battery gets low the EFI and
   the ignition fail to work.

   A certified aircraft engine does not need these to parts to keep
   running as the magneto is self contained ignition and of course most
   use carburetors or mechanical injection.


   Paul Lamar

       The Rotec is in the $750.00 dollar range right now.  I just got a quote a couple months back.
       Kay C Caldwell :)


       Wow that is amazing.

       Another advantage of the home made Holley is its low
       profile so it will fit under the cowl.


       I was working with a two barrel Holley
       on my RV4 just before I got involved with the TTC project.

       I cut it down but I would still need a bump on the cowl.
       The intake runners need to be about 18 to 20 inches long to get
       low fuel burn.


       Paul Lamar

   Is that your rv4 Paul? I really like that engine mount desing. So if you shorten the intake runner length enough for the carb to clear the cowl lines, you loose efficiency? Would it be possible to shorten the length and change the diameter to get the efficiency back?  Also if your running a turbo is the runner length as critical? Sorry for the 1000 questions.
   Thanks, Jacob Sturges


   Yep. it is now. Mike Wills  built  and designed the motor mount.
   It is kind of tricky getting the motor mount tube inside the exhaust.
   I think he did it all by trial and error as those were the days
   before Solid Works and Rhino.

   The criteria for an aircraft MM is to deal with the prop torque.
   Lycoming relies on the crankcase for handling that.

   It is about 600 foot pounds.

   Since the rotary is not designed for that I recommend using the PSRU
   adapter plate to handle that directly.


   To get a slide throttle in there you will need a fatter cowl.

   Paul Lamar

Jacob, intake and exhaust design and tuning is a delicate balance. Shorter and larger cross section enhance high RPM torque, thus HP. Longer runners with smaller cross section enhanc lower RPM torque. Best BSFC is at max torque.
In the late '60s, the big block Chevy road race engines used two different length intake stacks. Partly packaging but also widened the torque curve.
It is not about maintaining a specified runner volume. You need to choose the RPM you will run the engine. PSRU ratio will have a bearing on this.
You could use a rotary engine to replace a turbine hot section and use the PSRU backwards to spin the compressor fans to 18,000 RPM. Takeoff and climb performance would suck. You and your plane would need to be able to fly at say FL400 and you would need a turbocharger as large as the rotary engine to turbonormalize for that mission.
You determine the flight mission parameters first and work from there. Engine design and tuning is derived from that.

Dale Davies


Dale add your add your questions or comments  at the end of the thread. Not the begging.
I going to enforce that rule. If people don't do that it will not be forwarded.
My ISP changed the rules.

Paul Lamar

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