Thanks, but neither of my browsers will do this. You used CFM of 1 cylinder × RPM × VE ÷ 3,456?
261 ÷ 6 × 5,000 × 100% ÷ 3,456 = 63 CFM, which puts it closer to smaller than 1" ID. I don't think the VE will ever reach 100, and certainly not above 5,000.
That diameter provides enough area for a 43-1/2" cylinder at good exhaust velocity. The problem is that the Gen-2 individual (#1 & 6) port window in the casting is much larger than that, and it's a rectangle with rounded corners, about 1-1/4" tall × 1-5/16" wide. The area is about 1.52 In^2. assuming 3/8" corner radius, but the diagonal is 1.50" long (and longer if the corner radius is smaller).
The choices include:
1. use a primary tube large enough to completely enclose the port's diagonal measurement (with 18 gauge wall: 1.60" OD - the closest size is 1-5/8"), but too large in area, or (better, more work)
2. re-form (flatten 4 sides) of a short section of 1-5/8" OD tube to match the port outline's shape, then transition its outlet down and join to a smaller primary.
IMHO masking the port anywhere near the port face is an obstruction of greater effect than raising the gas velocity for better extraction. There is a well respected maximum taper (for megaphones) of 14° which should be used to minimize flow loss (anything sharper is restrictive), which would make the primary a baffle cone tapering from 1-5/8" down to 1".
