[jsceash]

I'll try a different way.

Have you ever gone fishing in a trout stream and watched a bend in the stream with a back eddy. The water spins backward and slows as it gets away from the current the speed up as it comes back around. A portion of the stream flows back continuously. It really obvious if there is a can or foam cup floating in it. That is what happens in the long radius flat back Porsche Plenum.

Now imagine the same stream and same bend if someone built a concrete barrier in the outside radius. The water would glide past at a faster speed or equal to the rest of the stream current. The IPD and or Pedro's Plenum.

Pedro's video is a bit of truth a bit of exaggeration. It exploits the defect in the stock plenum. The dead space becomes larger as the velocity of air is increased it is a principle in air flow called a "Boundary air layer". "Turbulent boundary air" is proportional to the air velocity so the turbulent area increases as the air velocity increase. Pedro uses a vacuum to blow air in the plenum which creates a higher velocity than the NA motor can produce but it is fast enough to exaggerate the flow problem. I've been trying to explain all day that turbulent air is like a plug reducing flow. The second type of boundary air layer is "Laminar Boundary air" its the drag created from the air friction with surface of the pipe. This is proportional to the square root of the velocity so it increases slowly as the velocity increases so it has little effect in the application. The big thing you see this affect is golf balls put dimples in the surface you can defeat the effect. Pedro uses a Teflon insert which has a low friction coefficient. IPD used of epoxy coat them but now the shot peen the inside so it like the dimples on a golf ball either way they negate the effect at the air flow speeds for the application