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.

Scott, all my test are static, have not had the airplane in the air yet.  My
prop is a Ivo prop magnum three blade ground adjustable.  Not sure what the
pitch is, I have tried it at many different pitches.    It was originally a
76", however I cut it down to 68" with the hopes it would help.  My kitbuilt
Bush Caddy is a big STOL aircraft, about equivalent to a Cessna 180.  I hope
the now 68" prop will work for my application.  My PSRU is Tracy's 2.87, at
the time (years ago) that was the only PSRU recommended for my set-up.

Bob Forbes

The 2.85:1 is better than the 2.12:1

Sounds like you need a lot more power Bob. My C182 has 230 HP.
What you need is a p-port or turbo.  Turbo it if you don't want to take it
apart and do a p-port.

The 182 engine is 470 cubic inches the RX8 engine is only 160 cubic inches.
One reason you have to run it 3 times faster.

 A bad intake on a 2 rotor is lucky to make 160 HP at 6000 RPM.

The RPM will increase slightly when the speed reaches about 60 MPH when the
prop blades come out of the stall conditions.

Copy Tracys' shoe box. Tracy claimed 200 HP with a 2.85:1 However I think
some internal porting was done by Bruce T.
Never the less it should be 185 to 190 HP at least.

You could also try removing one blade on the prop.

Paul Lamar


I tried the prop in a two blade configuration after I cut it down to 68",
made no difference.  My Bush Caddy has a factory engine rating range of
180hp-250hp.  That's why I would like a least 200 HP. I plan on putting it
on floats someday.

Bob

What is the EGT at max static RPM?
You may have a mixture problem.
You won't get much power if the mixture map is set wrong.

Get a wide band mixture monitor and mount it about 2 or 3 feet along
the exhaust pipe. They are sensitive to too much heat.

Try upping the fuel pressure.

Paul Lamar

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