Acceptable high RPM oil pressure

[Alan Kramer]

Is there a minimum acceptable oil pressure for an I5 turbo at 5k + RPM?
Reason I ask is that my 20vt exhibits the following oil pressure / RPM
relationship:

Hot Oil (100 C)
700 RPM / 22 psi (1.5 bar)
2000 RPM / 34 psi (2.25 bar)
3000 RPM / 45 psi (3 bar)
3500 RPM / 50 psi (3.5 bar)
4000 RPM / 58 psi (4 bar)
5000 RPM / 62 psi (4.2 bar)
6000 RPM / 63 psi (4.25 bar)

Cold Oil (25 C)
700 RPM / 85 psi (5.7 bar)

At first I suspected the pressure releif valve was cracking open early, but
considering that it opened at the correct pressure when the engine is cold,
it wouldn't make sense that oil temperature affect the spring in any way.

To experiment, I shimmed the spring with 2 copper crush washers. The cold
oil pressure went to 100 psi (6.8 bar) at idle and hot oil pressures were
essentially unchanged.  To me this proves the prv isn't opening early.

So is 4.3 bar at redline acceptable?  Sir Bentley specs out 5.3 bar at 5500
for an I-5 NA in another manual, but only gives a 2 bar at 2200 spec in the
20v manual.

P.S. All measurements were done with a calibrated mechanical gauge.

-----------------------------------
Alan Kramer
http://www.geocities.com/audikramer

'83 CGT 20vt
'86 4kcsq
'90 v8q
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