Flow bench designs

[Randy W.]

I have a question for flow specialist.
I am interested in the flow bench David has described in his articles and the one u have build and use using a shop vacuun.
I have been reading in a few forums that i have posted in saying it is a waste of time and wont work, but i know David and yourself have used such benches.
Can u explaine to me why they might be saying this or do they not understand?
Also can u explain to me how a sharp edge orfice works and how and how u calulate what size is needed and how u desing and calibrate a inclined manometer.
Sorry so many questions but am very interested in engine airflow and flow benches
and i consider what u and David say as gospel.
Thank u and keep up the great posts and replies.
Regards
Randy