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