Acceptable oil pressure

[signman]

Looking for acceptable oil pressure for a 1980 911sc at idle of 900 rpm and at running temperature
of 180 degrees. I'm running 20/50 Brad Penn oil.
Thanks

[RSTarga]

I would check it at 3 or 4k RPM. At 900 RPM you are not going to get a good reading.

[mb911]

10psi per 1000rpm

[signman]

Thanks! Will check at 4000 rpm.
Is10 psi the same as 10 bar?
Do you know anything about upgrading oil pressure spring/thermostat spring and pistons? I don't know if it applies to a 3.0 liter sc engine or how effective this would be.

[mb911]

1 bar is approx 14 psi

[signman]

Appreciate the info.
Thanks

[jrwilson]

Basically 1 bar per 1000RPM.

[Zuffenwerker]

Can’t tell much at idle from the factory gauge. Hook up an oil pressure gauge to the engine if you want to know exactly what it is at idle. As MB said 10psi per thousand rpm is what you need

[pampadori]

I had always heard 1 bar per 1000 rpm on a fully up to temp oil.
Then I reread my owners manual and noticed it suggested pressure to be 4 bar at 5,000 rpm fully up to temp.
To get oil up to temp, you're gonna need to go drive for 20 min.

[manbridge 74]

The above is from the factory service manual. It assumes you have the correct sending unit and gauge. I have found the VDO gauges to quite accurate but never a bad idea to double check with a separate gauge.

[Ian Comerford]

Originally Posted by jrwilson

Basically 1 bar per 1000RPM.

This is similar to what I think I know, although I can’t recall where it came from. I was told a long time ago to look for 3 bar at 3k revs and 4 bar at 4k. I don’t think it works over 4, nor under where the pressure usually exceeds the Rev relationship

[mb911]

Originally Posted by Ian Comerford

This is similar to what I think I know, although I can’t recall where it came from. I was told a long time ago to look for 3 bar at 3k revs and 4 bar at 4k. I don’t think it works over 4, nor under where the pressure usually exceeds the Rev relationship

Well again a bar is truely equal to 14.5 psi. My 2.4 s runs a true 10psi or above per 1000. This has been the same results on all previous 911 based engines I have had

[pampadori]

This is from the 1982 911sc manual.

"Oil pressure in the engine is shown in bar. With the engine at operating temperature (194° f) and the engine speed of 5000 RPM the oil pressure should be about 4 bar.
A drop in oil pressure at high temperatures is normal. at idle speed with the engine oil hot it is normal for the red control light to light up."

[lateapex911]

I'm sure zee Germans have their reasons but watching that needle under 1 at idle, considering the now super higher cost of these motors makes me hate the idea of sitting at lights! I mean does anybody else look at that thing and say, "C'mon man, just get over the 1 mark, at least!" LOL

[jrwilson]

I'm happy it's above zero. Try driving a '69 Corvette with a 52-year-old mechanical oil gauge that's gummed up and reads zero at idle. Nearly had a heart attack on the drive home from buying it.

[917_Langheck]

Looks like about 1.7 bar in my '84 3.2 at 180° and 900 RPM and around 4.2 bar at 3k rpm (20w50 Valvoline VR1)

[Zuffenwerker]

Originally Posted by manbridge 74

The above is from the factory service manual. It assumes you have the correct sending unit and gauge. I have found the VDO gauges to quite accurate but never a bad idea to double check with a separate gauge.

This is a good point there are 2 different sending units available depending on what gauge you have and they could easily be overlooked. Read the range on the sending unit and make sure it matches your gauge.

[Coblue]

Does altitude have any effect on how much a 'bar' is?

[pampadori]

You will get huge swings depending on oil temp and oil viscosity.
Run 10w30 and you could be a full bar lower than 20w50.
Pressure at 150° could be much higher than at 190° as well.

My latest fear now that temps are down below freezing is causing new oil leaks.
Running too high pressure (either by running 20w50 in colder weather or by revving the motor higher than you should with cold oil) can cause oil seals to leak. The rear main seal behind the flywheel for example has pressure behind it.
I think about this ever winter when I don't want to waste my summer oil and drain it when it only has a couple thousand miles on it. Do you waste $70 worth of oil or risk leaks that require engine-out to repair?

[lateapex911]

Thats one thing that my M3 does that I really like: The tach has a variable redline. It moves higher as the oil temp warms to normal operating temp