In NA form P-ports offer the highest VE thanks to scavenging from overlap. The faster the exhaust flows out of the port the more vacuum or negative pressure it creates............sucking in more intake air/fuel mix.
Turbocharge this P-port and naturally it improves its VE like any other port, but become very sensitive to exhaust pressure.
With its huge overlap, exhaust pressure(reversion) will dilute and heat up the intake charge and allow less intake to fill the chamber decreasing its VE.
P-port also remains open as the rotors start to compress the chamber volume lowering compression and thermal efficiency.

Another issue racers have encountered at high boost levels is the the point where chamber and intake pressure will be equal regardless of port, therefore the only way to increase airflow(horsepower) is by increasing boost pressure.

Majority look at porting as a way to gain airflow but have no idea how important port timing is in the quest for hp and efficiency.

JD

Even though I think your scavenging arguments are only true for low rpms, I think we are just repeating our arguments, so I think we need to give it a rest. In any case I keep trying to build my engine for 20PSi or below for best HP. I think the PP will give me the results but we will see.

CW

Scavenging ??? it only exist in NA form.
Under boost you end up with reversion of the exhaust and that has been my argument.
As long as exhaust pressure is greater then intake pressure, reversion will always be present and it does lessen at high rpms but not go away. Intake cycle is 270 degrees !!!
Intake pressure higher then exhaust pressure happens at lower rpms before your peak torque which results in boost leak thru the exhaust.

Either way, good luck with your set up and hope you reach your goal.

JD

why bother going w/ a pp and just run 20psi or less? a stock port motor w/ more boost will blow you away and probably be more reliable. plus it would have better driveability, fuel consumption, idle, etc. not knocking your setup, i'm just wondering.