Subject: CARB VS FI
From: Rotary Engine
Date: 4/13/2006, 2:24 PM
To: AAme



    > >
    > > >> Tracy's new fly by wire throttle.
    > > >> I guess it could be done so he did it :)
    > > >> --
    > > >> Paul Lamar ...No rotor no motor.
    > > >
    > > >
    > > >
    > > > Paul
    > > >
    > > >
    > > > This is the throttle from the RV-8?. With a P-port manifold to
    > > > could it be used between the compressor and the intercooler?
    > > >
    > > > Hmm .....combined with his electronic mixture control and an
    > > > electric C/S prop, the control panel real estate area for these
    > > > three item becomes very small. Game like. Failure mode with
    > > > the E-throttle would be st be W.O.T. I
    > > > presume.
    > > >
    > > >
    > > > I have a central control stick in my design now with arm
    > > > rests built into the sides of the plane. Just a thought
    > > > and perhaps only an experiment. I would like to mount an
    > > > auxiliary electronic side joy stick coupled to the
    > > > auto pilot servos so the plane in that mode would be
    > > > Fly-By-Wire in a sense.
    > > >
    > > > Touching the manual control stick would disengage the
    > > > auto pilot and/or side joy stick reverting back to
    > > > manual inputs to the cables.
    > > >
    > > > Doug in Japan.
    > > >
    > > >
    > > > Yep the RX8 throttle is fly by wire. I have never been
    > > > able to get it to open more than 80%. I guess the air is too
    > > > hot around here.
    > > ; >
    > > > As I said recently what you really NEED in an airplane
    > > > is two magnetos and a carb :) In other words KISS.
    > > >
    > > > BTW where in the world are you? I thought you were on your
   way to
    > > > Placerville. Call me from Lancaster if you need help.
    > > >
    > > > Paul Lamar ...No rotor no motor.
    > >
    > >
    > > Paul,
    > >
    > > Yea I got the part about magnetos and carb loud and clear:)
    > > Magnetos still have some advantages for me, carbs not.
    > >
    > >
    > > I'm still in Japan. I had to delay my departure date a week
    > > for various reasons. I'll be seeing Tom Webber on the 18th
    > > and working on the plane on the 19th and 20th. Flying soon
    > > afterwards I hope.
    > >
    > > Doug
    > >
    > >
    > > ---------------------------
    > >
    > >
    > > Hi Paul: The advantage of FI over the carb has to do with carb ice
    > > and
    > > even distribution of mixture. In terms of BSFC the carb can be as
    > > good
    > > as FI. When FI was first introduced on outboard motors the FI
    > > units had
    > > worse BSFC than the carb engines. This was mainly due to lack of
    > > the O2
    > > sensing which was not included because of water in the exhaust.
   The
    > > best BSFC in the carb engines was achieved with one carb per
   cylinder.
    > >
    > > Bob Y
    > >
    > > Compared to a total electrical system failure providing carb heat
    > > is a piece of cake :) EFI and electronic ignition suck down
    > > a lot of amps. If you are flying 500 to 900 mile over water legs
    > > and you lose the electrical system you are not going to
    > > make it on the back up battery alone. There ar e places in
    > > Alaska where it is 500 miles between suitable landing
    > > sites.
    > >
    > > Totally dual electrical systems are expensive and heavy.
    > >
    > > Paul Lamar ...No rotor no motor.
    >
    > The p port carb engines I have seen all have the carb mounted too
    > high for most aircraft. Are there design options that mount the carb
    > lower? Jerry
    >
    > Sure you could come out and down past the exhaust
    > system with some rather long intake tubes.
    >
    >
    > --
    > Paul Lamar ...No rotor no motor.


   No matter what system you run (carb or FI) it does not matter where
   the butterfly resides when at WOT if the throttle is in the intake
   tube.  You could mount a side draft carb next to the block and use
   any length tubing needed to tune for max power.  As soon as you
   stick a butterfly or slide in the airflow you will no longer get
   organ pipe tuning.  If you want to tune for cruise you must have the
   throttle as part of the intake plenum rather than a part of the
   intake tube.

   Ken Powell
   Bryant, Arkansas
   501-847-4721
   C150 / RV-4 under construction


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