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Old 10-31-2007, 11:43 AM   #1
DJIMPREZA
Scooby Specialist
 
Member#: 1199
Join Date: Apr 2000
Location: Caracas, Venezuela
Vehicle:
1994 Supra+1K, 22b
alike, 07STI

Default STI VS WRX Short block builts. Oil pressure differences related

Two scenarios

Conditions
Ambient temp around 32 Deg Celcius, Engine at 95 deg Celcius
Idle set@900 rpms

1- Built 2007 STI engine with single AVCS using Cossworth Coated Crank and Rod bearings, Cossworth modified 10mm OIL PUMP using the same 20w50 Valvoline Racing Syn Oil

Oil pressure readings

18 psi at idle speed
75 psi max oil pressure recorded at 4K

Gauge needle is VERY STABLE on each reading. Pressure drops on some rpms according to TPS position, I guess it has something to do with AVCS.

2 Built wrx 2002 NON AVCS, EJ22 pump two shims in it, 2.5 sti short block

Oil pressure readings

45 PSI at Idle speed
95 psi mas oil pressure recorded at 3k

I have to admit that I CANNOT WITHSTAND THE LOW OIL PRESSURE ON THE STI

AND I know its normal and comon..

If I Want to raise it 20 psi on each range.. a 12mm would do it? a 12mm with an extra shim? or jus tmy cossworth 10mm with ANOTHER one Shim?

Do we have to open the oil port on the 12mm pump and put and extra shim to compensate??

Recomendations are welcome based on real data/experience

Thank you
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Old 10-31-2007, 12:37 PM   #2
mick_the_ginge
Citizen Mick
 
Member#: 27646
Join Date: Oct 2002
Chapter/Region: NWIC
Location: Portland, Oregon
Vehicle:
2003 Sleeved 2.5
Oil Dry Sump Goodness

Default

Shim = pressure. Size = flow. While the EJ22 may look better it's more than likely a 9mm pump so not flowing as much as the 10mm. I'm liek you however, I want flow and pressure. That idle pressure is high on the EJ22.

75 psi is about right for the STi. Use the 10psi per 1000 rpm. If you are only running upto 7000 rpm then 75 psi is just right.

Forgot to say, their are pictures (from me) on shimming a oil pump. Can't find the thread but I think it's in a crank related thread. Shim goes in the side of the pump, under the big screw on the side.
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Old 10-31-2007, 01:40 PM   #3
DJIMPREZA
Scooby Specialist
 
Member#: 1199
Join Date: Apr 2000
Location: Caracas, Venezuela
Vehicle:
1994 Supra+1K, 22b
alike, 07STI

Default

Yes, yes I know.. maybe I just need to add one extra shim to the sti, it is just that will it raise the idle base pressure as well? don`t think so...
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