I can't for the life of me figure out why the port opening has to be so
much larger than the inlet tube. It may be the duration of the open inlet
they are looking for.
Do you know what sort of power they found with the 13B stock PP?
Any how for those interested, I've settled on a 44mm inlet straight
tube with a late opening and late closing - same a stock PP IO 86 BTDC and
75 BBDC.
I can buy 41mm and 44mm tube and have opted for the 44mm ID inlet tube,
only 2.35sq" area.
George ( down under)
I have heard that the 13B Pport has over 330 HP around 10,500 RPM. The
port size at the rotor is just a result of late closing for operation at the
high RPM. It reduces velocity and hurts lower RPM power. Same with the side
port. Increasing bowl volume slows velocity and move peak power up the RPM
band. Where rules allow, side port people fill in part of the bowl with epoxy
to keep velocity high after extending the closing line. We are not
allowed to add material at all.
Lynn E. Hanover
Ah Ha - now you tell me Lynn, adding material sounds like something
I've heard before with people playing with metering the flow of the side
ports. I don't however think I will achieve 165hp, 125 would be
nice.
My motto "Aim High - Accept Less"
George (down under)
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