Now you're asking really pertinent questions. All I can answer is how it pertains to my vehicles. I actually have an oil pressure readout in psi on the dashboard as part of my Driver Information Center. The Centrifuges I have seen require 1/4" size INPUT line and a larger gravity drain.
If you don't KNOW what psi you have on your running engine, you need to install an oil pressure gauge either temporarily or permanently or forget installing a centrifuge.
How much oil pressure is enough to spare to power a Centrifuge? I would think that e-mailing the supplier should be able to assist you. They are the ones who want to sell them. BITOG has an excellent article on how much oil pressure is enough:
http://www.bobistheoilguy.com/motor-oil-105/ The suppliers I have contacted state in their literature (obviously) that the more oil pressure you have, the faster the centrifuge will spin, with optimal centrifuge operation between 3-6 bar; or about 43-87 psi.
Since you mention GM V-6 or 8; I will tell you what mine is; I drive a 2003 Lesabre with the famous 3800 V-6. Manufacturer spec oil is 10W30; but the following year, 2004 GM changed their spec'd oil to 5W30.
I'm running 5W30 Amsoil full synthetic, and after the engine is fully warmed, I have 55 psi oil pressure at idle. Cruising @ 60 mph I have 60 psi. 70 mph I have 62-63 psi oil. Cold start I max out at about 70 psi oil pressure; and I'm doing all of this WITH a bypass filter installed which is fed by an AN-4 line.
I plan, in the near future, to install a centrifuge and supply it with an AN-6 line. I have ordered the Centrifuge, and I don't know yet if I'm going to fabricate (modify) an aluminum valve cover to mount it on or cut a hole above the oil level in my oil pan and weld a return fitting there.
The main drawback (in my limited experience) with a centrifuge is that manufacturers specify a rather large return line which must gravity drain back into the engine in a non-pressure location. (Mine coming) requires a 19 mm minimum return line. And of course a centrifuge requires a level mounting spot with overhead clearance for disassembly and servicing.
The benefits are obvious:
http://www.machinerylubrication.com/Read/1347/centrifuge-contaminants
If my oil pressure drops too much, ZZPerformance and Intense racing both sell kits to raise my oil pressure; it is simply a shim behind the spring to the bypass valve:
http://zzperformance.com/3800/engine/oil-volume-kit.html
http://intense-racing.com/Merchant2/merc...ode=3800_Engine
There is even a kit to adjust the oil pressure on this engine with the turn of a screw, so you can DIAL it with the engine running:
http://intense-racing.com/Merchant2/merc...ode=3800_Engine