Acceptable high RPM oil pressure

[james accordino]

I think this is sky high for a street engine.  None of
my friends believe my oil pressure is so high not
running some trick pump.  I know many late model GM
cars run super low oil weights and pressures.  0-30
oil and 20lbs. =or- at idle up to about 40-50 max.  I
use 5-30 or 5-50 synth. and mine pegs on startup and
stays pegged relative to temp. and rpms.  I find
Bentley (page 17.19, vol. 1 of the 100/200) says 2.0
bar(29 psi) min at 2k rpm with 80*C(176*F).  Then says
when raising rpm pressure valve must open at 5.0-8.0
bar.  "pressure may be exceeded only slightly".  Then
another paragraph regarding the perils of high oil
pressure.  So unless you're exploring the burst
strength of your oil filter or cooler lines, your
pressures are fine.

Jim Accordino

--- Alan Kramer <ackramer at hotmail.com> wrote:
> 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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