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As I read it,
Method A & C blocked off 3 of 4 venturii
Method B & D blocked off 2 of 4 venturii


Yep.
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What were the typical test pressure drops?


I was pulling 10"-9" for single-bore tests and 4"-3" for 2-bore tests... until I tried the 1.50+" venturi configurations. I couldn't even get a solid 3" reading and had to back it down to a 2.5"...

It was like that scene in "Jaws" when they finally see the Great White up close for the first time and somebody says "We're gonna need a bigger boat." At that point I was really thinking I needed a bigger flow bench.