We ran it and flew it Matt. Mustang II. No fuel cloud with
fuel injection. The cloud is caused by the reverse flow through
a carb. The venturi cannot  tell the difference so fuel comes out
regardless of the flow direction.

      Mark Steitle is flying one as FI p-port 3 rotor.

      Paul Lamar

 Paul,
  Do p-port engines have much of a tendency for fuel stand-off? It
is a bit of a problem in piston engines especially with IR type
 intakes  because of the pressure pulse reversal when the intake
 valve closes.  A p-port does not really close the intake flow and
 stop it  momentarily. It gets redirected to the next side of the
rotor as the  apex seal passes the port. Your charts of intake
 pressure show like  a sine wave. Intake tuning does affect this but
 the amount of  pressure difference should not cause a stand off
problem.
  Dale Davies

  There is no stand off with Tracy's efi. IMHO it is a carburetor
phenomena.
 The venturi in the carb cannot tell whether the air is flowing in
  or  out so to feeds fuel into the air stream regardless.
  Paul Lamar

I don't think a carburetor p-port will have an issue with fuel
stand  off for the reasons I stated. Automotive V8s will have it
even with  a single carburetor. Even note the brown stain on the air
filter  lid? If there is a tendency to have stand off with a carb,
it will  do it with EFI also due to the pressure pulse. Throttle
body EFI  more prone to show this phenomena. Port EFI masks it as
the runner  length does not allow the fuel cloud to escape before
being injested  again. A port EFI with the injectors at the open
inlet end could  display the fuel stand off. A side port engine
should have a  slightly greater chance of it, due to the longer port
closing  between intake events.
Dale Davies

The carb p-port standoff is spectacular. This is a Weber carb.
  http://www.youtube.com/watch?v=NKJ00JsnS8A

Paul Lamar

Ok. So if you removed the Weber and installed a throttle body EFI
from say a 454 Chev, the fuel stand off should be the same. If you
extend the runners to the same length as the Weber carb tops and
then put injectors just above the pipes, the stand off should also
be similar. On the long intake of 24 to 28 inches, the stand off
should be changed. At least the RPM that it becomes prevalent, will
change due to the tuning effect. How was the Le Mans 26B engine for
stand off? Yes the youtube video is spectacular and revealing.

Dale Davies

Here is about what your are describing and there was no stand off.
We ran it with the top off the air box. I was surprised.

Paul Lamar


So Paul,

If you moved the injectors to spray in the open tubes, do you think
you would
get fuel stand off? With the Weber carb, if you mounted ram stacks
like on the
Can Am Chev engines on the throats, do you think you would see the
stand off
then. Possibly the length upstream of the fuel introduction keeps it
inside.
May increase bsfc or help it. I know if you shine a bright light
down a carb,
you can see a fog in the intake manifold.

Dale Davies

We saw a lot of stand off on the CanAm Chevy engines with and
without stacks.

I designed a ram air scoop for the roof with boundary layer bypass
on the
the Nürburgring winning 2D.. We got much better MPG.

I have not tried spraying fuel into the opening yet.

Paul Lamar


This is sort of on topic...Has anyone ever used a 'ram' air scoop on
an aircraft in
the same way they are used on automobiles?  Don't they increase the
air flow into
the intake?  Properly designed, such a scoop might increase intake
manifold
pressure in the same way that a turbo would, but perhaps not to the
same extent?

Gene Kahn

Mooney's have them. Worth 1/2 inch of Hg.


Paul Lamar