The sump is normally needs to be emptied (or rather, circulated) every every 7 to 12 minutes at maximum power.
On a 100 hp 2 liter OHC engine, 1.35 Imp Gallons per hour per 1000 rpm is common, and on a 3.5 quart/3.6 liter sump, at 5200 rpm, thats about a sump every 7 minutes. A hard core 300 hp engine reving to 7000 rpm and a dry sump, needs a 2.2 Imp gal per hour per 1000 rpm. That is around 2 Imp gallons or 9 quarts or 9.1 litre system is scavanged every 8 minutes.
A big block V8 may like up to 8 US gals per hour per 1000 rpm, enough to empty even a big 15 quart sump every 12 minutes.
A turbo engine likes to have only 50 to 60 psi, and the specs for a Biturbo are little different to a 4cyl OHC engine. The general rule is somewhere between to two for flow rate.
6 to 10 liters per hour per 1000 rpm.
Never go for a higher than 60 psi base pressure, or it will most certainly go above 90 psi when cold.
The real issue is that the oil pimp specs should never be changed, becasue they are based on the clearances used on the engine. Going wide requires up to twice the oil flow. Changing the gauze of the oil sump scavange filter can reduce the life of the engine, but increase the oil flow 75%. Moving the gause closer to the sump than 10 mm (3/8") can cause the oil pressure to go up, and the flow rate to go down. Even an oil spec change can cause funny issues.
On an old 'common' Ford, any oil flow issue is funny. Old Fords are like dimes, everyones had one. On a Biturbo, its enough to make you cry.
I just wish the whole beauty of these wild Italian cars had the quality of the Japanse IHI turbos that flanked it. The Itallian engineers have set up everything just so, and I'd look for additional factory service help on the net.
