Doug, this year's crossram intake is a near carbon copy of last year's except for three minor changes. One is that the runners are about 1/2" shorter, to raise the RPM at which the intake tract tunes by about 300 RPM. The second is that there is more taper in the runner, an area increase of about 1.5% per inch, rather than last year's 1% per inch. Finally, the shape of the runners at the head is different to accomodate the different port configuration, more squarish this year as compared to perfectly round last year.
The original "steaming pile" intake was of a conventional design, with runners that were about 3" shorter than this year's or last year's manifold. It looked like a more conventional design, with all the runners entering in the center of the plenum, compared to the crossram designs of the last two years. But in order to make the design conventional, the runner length was way too short for the RPM range that I'm operating in, and so the manifold didn't tune the intake pulses effectively. I was concerned about the position of the runners and flow of the air in the plenum of the crossram design last year also. But compared to the original intake, the crossram picked up 50 foot pounds of torque and over 20 horsepower. So whatever disadvantage the runner entry in the plenum may have, it was more than offset by the benefits of the longer runners. Also of interest was the effect of a 1" plenum spacer in last year's crossram manifold. This raised the plenum volume pretty significantly, and gave more space above the point in the center of the plenum, where the runners come together. I figured for sure it would improve power output. But it had zero effect on power. Based on that result I don't think that the point of entry of the runners into the plenum is a major concern, at least in this engine.
