This email is to address Scott Gettings wanting to know if anyone
  else has a set-up like his Renesis 6 port.  I have the same set-up
  as Scott, and I'm using only the four yellow injectors and have the
  two red ones blocked off, as per Tracy's direction.


  However Scott, I cannot get over 5900 rpm. The engine rpm does not
  increase after half throttle.  I checked to make sure the throttle
  body was opening all the way, and it is. I also removed my muffler
  and replace it with a straight pipe thinking there might be an
  restriction, not the case, made no difference in rpm.  I chopped my
  three blade 76" prop down to 68" and still no change in rpm. I'm
  also using part of the original six port intake, with no runner
  length. Now the only thing I can think of is the engine cannot get
  enough air.  Looks like I have no choice but to completely redo my
  intake or try installing a super charger to force more air in. Not
  sure if that will work or not. I'm using Tracy's EC3, EM2, & 2.87
  PSRU.

  Bob Forbes


  The intake configuration and pipe length are critical for the HP.

  The prop runs into a brick wall when the tips get close to Mach One.
  What is your gear box ratio? Sounds like 2.2:1.   A 3.12:1 would
  work better with the rotary.

  When the prop torque requirements meets the torque out of the gear
  box the prop  and engine of course will stop increasing in RPM.

  You can move peak torque around with intake pipe length. You need
  roughly 18 to 20 inches of intake pipe length. The longer the pipe
  length the lower the torque peak RPM.

  A p-port engine will increase the max torque at any pipe lenght.

  So too will NOS :-) This is probably the cheapest and quickest.
  Makes up for a lot of intake configuration errors :-)

  A turbo charger is more economical than a super charger as it uses
  the otherwise waste energy in the exhaust to super charge the
  engine.

  Paul Lamar

  Bob please read this section of the web site.

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

  Paul Lamar


  Thanks for Bobs output. Questions I have include what is  the prop
  pitch and the  throttle body diameter? Is this static or in-flight
  RPM? I agree the gear ratio maybe also an issue.

  I also have built a short and compact intake system (sounds like
  yours) with possible nitrous back up for take off if necessary.  I
  will test the entire engine system  mounted in an airboat prior to
  flight, which should give me some good data for this pusher
  configuration.

  Thanks!

  Scott Gettings.

  Attached are a few pictures of my short intake manifold. I certainly
  realize this may not result and anywhere near Optimal horsepower, but
  it was simple to build. The throttlebody is 2 7/8 inches inside
  diameter.   Although shorter, it is still much less restrictive than
  the stock intake manifold system. It can also receive ram air from
  the cowl intake. If this does not produce enough power in testing, I
  will convert to the over-the-top runners configuration.

Of course, this is not an endorsement of this solution compared to the
longer runners, as Paul has an incredible depth of experience in this area.

Scott Gettings


Scott,

Your intake set-up is identical to mine, (photo's attached).  I'm using the
factory throttle body that came with the RX 8 engine, and 3 1/2" intake
hose(photos). I can't imagine it not getting enough air.

Thanks,
Bob Forbes


Read up on Organ pipes Bob. Tuned pipe intakes can exhibit 120% vloumetric
efficiency.  It sounds like you did not read http://www.rotaryeng.net/intake.html :-)

It takes HP to suck air into an engine. Six tubes of the same area are much worse
than 2 tubes because of the internal  skin friction increase.

 An intake sys is only as good as the smallest pipe diameter in the train of pipes.


Paul Lamar

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