I think I have this figured out. I use that empty time when I first wake up and I'm still there in bed to think about Buick projects.
Last year when I turned the "Biggie" over to Jason, I suggested a changable spacer plate to go under the plenum, but my idea was to use the plate to hold a tubing elbow with an interchangable end to direct the flow to the runners. It was to be like a Hemco you could tune for different combinations or for track conditions. And it would hide under a stock bonnet to be sneaky. Jason threw out the elbow idea and kept the plate and lucky for us all he also came up with a good way to measure the flow, not pressure, the flow to each port. Instead of interchagable ends, he came up with different plates for each style plenum. This is great work.
Lisa tells me I need professional help, but I swear I see this stuff in my head. What Jason has made is not a flow restrictor or director at all but a simple plenum divider. It creates a calm air space below the plate which allows each port to draw an even amount of air from the plenum.
Think of the inside of the plenum like the inside of a pick-up bed as you go down the road. The air comes in over the top in front, flows down and hits the back producing a high pressure area. It then has to make a full turn to the front where the fresh air coming over the top creates lift pulling it off the floor. High pressure back, low pressure front. Like a big circle. The faster you go, the faster the circle goes too.
Now Jason's plate stops the air from making that big circle inside the manifold. The air turmoil now occurs above the plate and basically calm air should exist under the plate. The plate does not direct, or restrict the flow to any port. It allows each port to draw the air it needs from the stable, calmer air under the plate. This could also explain why the plate seems to make improvements from idle to full throttle. When Jason says a stock manifold will flow more air with the plate than without it, I can see that.
My idea, like the Hemco, would have just moved the high pressure flow from the back of the plenum to the center. I think it could have been better than the Hemco, but not better than Jason's simple plate.
Now if you want to test this theory with pressure probes, you will need to place them in each port, not just above and below the plate, as some have suggested. And the test would be port against port, with the plate and without. If the picture in my head is correct, you will find pressure readings support Jason's flow readings.
You have to respect a guy who can make things work.
