Paul,

     I have run this by Tracy and I wandered what you thought of this.
This
     is a 4 port 13b in a Cozy III. I was intending to take the intake
duct
     to a NACA scoop on the lower left cowling ram air style. The
controller
     is a RWS EC2. The actual ducting will be rigid fiberglass with
inline
     filter. I am looking for 160 to 180 HP. Good idea? Bad Idea? Start
over
     with a dynamic chamber and long runners?

     I would greatly appreciate your comments.

     Steve Denny

     Windsor, Colorado


     BTW Sorry, apparently I can only send one pic at a time so here
come
     2 e-mails

     ------------------------------------------------------

     That is the way to do it if you don't have graphic scaling
programs.
     Anything over about two meg is too big to send.

     Any Y in the pipes causes a discontinuity. In effect what you wind
     up with is several short pipes resonating in series. This, in
     theory, narrows the torque peak but moves it way up in the RPM
band. Perhaps higher
     than 11,000 RPM. That of course does nothing for you. This is an
over
     simplification of course so unless you dyno this engine no telling
what
     is going to happen.

     I WILL say you will not get as much HP at 7500 RPM or 6500 RPM as
     you would  get if you had just four long pipes of the right length,
a plenum
     and this throttle  body.

     You want the torque peaks in the 5500 to 6500 range. That yields
the
     best cruise  BSFC and the best power in the 6500 to 7500 RPM range
for aircraft
     use. You get that with the pipe lengths in the 25 to 28 inch long
range. These
     numbers are also somewhat dependent on the inside diameter of the
pipes. A
     smaller dia. pipe moves the torque peak down. Larger pipe dia.
moves it up.

     Matt put it very succinctly awhile back but I lost the message.
     Do you remember that Matt? Can you upload it again?

     BTW NACA ducts are not recommended by NACA engineers for carb air.
     You need a true ram air scoop.

     Paul Lamar ...No rotor no motor.



Steve,
I can't see into the TB throat very well, but it appears there is a step
just past the butterfly.  If that's the case I would try to get that
smoothed out as much as possible to promote good airflow.  Just an
observation.

Mark St.




Thanks to all for your input.
 I am prepared to start over if there is any doubt that I will not get
the 160 HP to 180 HP @ 6,500 RPM that I am looking for. I think that I
am hearing some doubt. If I really clean up the inside and provide all
the air it wants is there any chance I will be happy with it?
Also this airplane was setup for a carburetor originally. Since I could
not get a return line to the fuel tanks or the header tank I found a
dead end regulator from Marren Fuel Injection that requires no return
(it is clearly seen in the photos). Is there any reason to be concerned
with this setup?

Thanks,
Steve

160 HP should not be a problem.