Frankly this is a lot better than I expected and it removes
one of the possible arguments for not using a P-port.

Many of the P-port neigh sayers state high fuel consumption
as one of the reasons for not using them.
It appears that if exhaust gas mixing is taking place it is compensated
for by the better breathing.

Paul Lamar

George Lendich wrote:

Paul,
I was surprised at that BSFC also - what would it be leaned ?

You may very well be correct with your assumption on the better breathing
compensating for the exhaust gas 'overlap' mix. However they may have a
little bit of housing ( inlet) shape that we don't know about, which would
help here also.

All that need to be concerned about  now is the back pressure and as , if
you say, the closer butterfly compensates for the backpressure, as Richard's
6" manifold clearly demonstrates, with resulting 1,200 rpm smooth idle.
George (down under)

There is nothing trick about the Lemans engine housing shape.
It is a more or less a large mostly round hole. You can scale the 
port diameter and timing from this drawing. 
I never understood why people could not understand that while for 
the last five years we have been talking about the Lemans geometry 
and port timing. I think I mentioned it many times until I got 
tired of mentioning it over and over again. You can also scale the 
fixed length of the runners and add the lengths from this chart 
for any RPM between 6000 and 9000.
 
The butterfly does not compensate for the exhaust back pressure HP wise.
You still need to keep the exhaust back pressure down if you want good HP.
6.5 inches is not close for the butterfly. The Power Sport engine
has the butterfly in the rotor housing. Richard's engine is not yet tuned
with long runners so the jury is still out on the quality of the idle.

Paul Lamar
 
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