QUOTE(nditiz1 @ Jun 6 2022, 09:49 AM)
I would like pressures to be 1bar:1k when hot, temp>210f
Oil pressures are affected by several things but trying to use oil temperature to control them is counter productive
911 / 914 engines are sort of an odd animal because they are air cooled first and foremost. This has a lot of downstream consequences for things like oil temperatures and oil pressure.
First things first:
Do you know anything about the bearings and/or clearances of your 2.4L engine?
If Ollie's is to be believed, they (and other 911 engine builders) seem to want to run early mag case engines on the loose side. I believe this is for two reasons:
1) a loose engine makes more HP.
2) a loose engine is less likely to spin a bearing early in it's life (when the builder and/or machinist is on the hook!)
I went though this with my own 2.4L build and trying to get bearing clearance at .0025". Several sources seemed to be pretty happy with .0035" or even .0004" which is where I started with a fresh line bore (in spec but toward high side), aftermarket bearings, and a standard crank that was in spec (but at small end). I ended up spending another $2k+ to get the crank reground and to go to Porsche OEM bearings to get the clearance where I wanted them. How many folks would have just accepted that and put it together at .0035 - 0.004" to avoid the extra costs? The effect on oil pressure would be predictable.
Do you know what oil pump is in it? Early magnesium pumps have more internal pump bypass loss than later 4 rib aluminum pumps?
Do you know if the oil pressure bypass modifications were done and/or are you now using the right oil pressure relief springs / pistons that would be required with the oil bypass modification?
See where this is going. None of these things that affect oil pressure are dependent on temperature.
Second:
911 / 914 engines are an an magnesium (2.4L 911) or aluminum case (914 / later 930 & 3.x 911's) supporting a steel crank shaft. There are vastly different thermal expansions between those materials.
The bottom line being that unlike a cast iron block supporting a steel crank, you'll lose oil pressure faster as temps increase. Bearing clearance is opening up as things warm. All this is accounted for by design but expecting pressure to not drop a little as things get warm is not a realistic expectation.
So if you're getting 3 bar at 4k (or even 35 psi) when things are hot, I wouldn't be freaked out. If you have 3 bar at 6K, I'm slightly more concerned.
1 bar = 14.5 psi. So you're targeting a 45% increase in pressure over the standard rule of thumb? What if anything did you do to the pump and/or bearing clearances to have this expectation? That puts you at 87 psi at 6,000 rpm. Do you know what pressure your oil pressure relief valves are set at?
For reference, my Miata (cast iron block / steel crank) spun 7200 RPM at about 60 psi and went 228k miles without a rebuild - finally the body rotted out before the engine gave out. Food for thought.