[jsceash]

KRAM36

Also what about the 997 T being so much larger then the Plenum opening? Is this a huge issue?

The answer to the question you asked is it has some negative effect. Is it a nail in the coffin NO! Does it add to the Disturbed air Yes.

For my part my explanation of the air hitting the back of the tube is easier than trying to explain a boundary layer, molecular bonding in air molecules, or fluid shear.

Any time you go back to the drawing remember this is just a snapshot. You have to understand that it's only true at the flow speed used to graph it. Now look at the white area in the center, that is the eddy(s), I tried to explain in the "Stream post" there is a light blue area surrounding it, which is another separation area of disturbed air. If you compare these 2 areas to the Y pipe below they are larger because the air runs very tightly to the solid wedge diverter in the Y design. Because it does the flow cross section is more constant in the Y design. Also because air velocity affects the stagnant air wedge in the 997 Tube the flow cross section varies more with flow speed.

I agree with Blue2000

The effect of a physical wedge is more likely to disrupt the secondary pulsation supercharging effect of the tuned plenum than it is to help bulk flow in any way.

The flow would be very close in both systems with the Large radius T maybe even having a slight advantage for RPM below the point where the secondary tube damper opens. The second the secondary tube dampener opens, the IPD has the 997 tube hands down. Once the cylinder pulse has a secondary route the wedge no longer has to deal with the back flow.

I get a significant power and torque boost at that point.