I've seen info on this in snippets in various threads over time, but
why not lets start from scratch?
No gauges at the moment, and a ballpark setting will do for now.
(Freshly rebuilt machine, with new/different/adjustable OPV.
Vibratory pump... Ulka EAX5.
What is the exact procedure, and how does one determine the correct volume
for the desired pressure result?
The Ubiquitous Ulka pump graph:
Indicates a certain maximum volume from the pump total.
With blind basket in portafilter, all the flow out of the OPV bypass = the total volume?
How does one determine the desirable volume?
How does one know how that translates to what goes through the brew group?
What about the portion that gets bled off through the OPV?
A million other questions, but best to let someone who knows the answer reply
than going on and on.