Jerry,

After much discussion with Lynn Hanover on P-Port timing, I finally built my own degree wheel and set it up to test the different timings.
See attached.

Your  IC 82.55mm (from centre) and your IO 44.45mm (from centre)
appear to be exactly the same as the Mazda Factory PP i.e.  IO 86 degree BTDC and IC 75 degree ABDC. - which gives one some piece of mind when wondering if
the numbers are correct, regardless of who was the expert to calculate it.

Interestingly our mate Lynn Hanover's racing PP is IO  110 degrees BTDC ( opens earlier) and IC 85 degrees ABDC ( closes a good 10 degrees later) - a much
bigger (Racing) P-Port.

Before I made my degree wheel I made a guess of what I thought might be OK and came to a conclusion of IC 70 degrees ABDC and IO of 90 degrees BTDC (or BDC) -
which is about 5 degrees off your's and Mazda' calculations. Not too bad I thought!

What I don't know ( and I've asked Lynn, if he knows) is the critical degree where the Intake compression pressure overcomes ( and restricts) the intake flow.
I figure if we knew that and backed it off 5 degrees we would be at optimum Volumetric Efficiency for the P-Port.

We still have some overlap so the intake charge will be diluted to some degree, but don't know if it will effect the idle.

Does anyone know how well the factory PP Idles?

George (down under)

 
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