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Hi guys-- I've followed the posts about different types of oil and have a question about what is a normal oil pressure reading. My car-- on cold start-- maxes out at 5 (bar?) at idle until warm. When warm, it may drop to 4 or 3.5 on idle, never lower. And any time I step on the gas at all, bounces back up to the max 5.
Completely normal. Your owner's manual says 3.5 bar at 5000 rpm. Warm idle pressure would be checked after oil and coolant are fully up to temps, oil around 210 F. Many see warm idle oil pressure of 1.5 to 2 bars. Higher mileage cars would be lower around 1 to 1.5 bars. As long as the pressure never drops below 1 when idling and you are seeing numbers above 3.5 at higher rpms you are good to go.
3.5 bar of hot idle oil pressure is seemingly very high, but remember we are dealing with a sending unit and gauge that aren't exactly dead on nuts accurate.
Both my 2005 S cars are the same - 3.5 bar at idle and 5 bar at anything higher than idle. Ice seen it come down a little from 5 on a summer highway trip when it was 110 degrees and we were running about 85 F.
You're good. I think as long as you show 1 (10 psi) for every 1000 rpms you're good. Low pressure is an issue. High pressure is ok because there's a check valve that will bypass excess.
I beliieve high pressure was an issue in early air cooled cars because it would bypass flow to the cooler if it was too high.
OP, when your car is stone cold, turn it on to accessory mode only, don't let the engine turn over. After you've done that, check to see if your oil pressure gauge reads anything above 0. In the event it does, replace your oil pressure sending unit because it's likely that it is faulty. You could also try cleaning the contacts but I personally never had any luck with that.
High pressure is ok because there's a check valve that will bypass excess.
Odd, I can't find the oil pressure relief valve for 997.2 base and S. It exists for the 997.1, 997.2 turbo GT3 RS etc.... but not the base and S. I could not find it in my PET diagrams for my 2009 C2S nor Pelican's part catalog.
So... how is pressure regulated in a 997.2 base and S?
See here for Pelican's part system for 997 oil relief valves:
Odd, I can't find the oil pressure relief valve for 997.2 base and S. It exists for the 997.1, 997.2 turbo GT3 RS etc.... but not the base and S. I could not find it in my PET diagrams for my 2009 C2S nor Pelican's part catalog.
So... how is pressure regulated in a 997.2 base and S?
See here for Pelican's part system for 997 oil relief valves:
997.2 is a regulated pump in the sump (actually not a sump because it is a part of the block). It is an analog control unit. Pressure is based on several different things. The proportional control valve that bypasses flow to lower the pressure to the desired amount basically insures that the pressure is as high as it needs to be always. I have read that Porsche also shifts the teeth on the pump so excess power is not lost via over driving the bypass back to the "sump" chamber, although the schematic doesn't diagram this as well.
The gauges on the 997.2 dash are computer controlled and, IMHO, generally lie to you. I can't say this is the same in the 997.1.
As an aside ... Since pressure is finely regulated, take a step back to the oil. Flow is what we are looking for more than pressure. Flow is a function of pressure and viscosity. Porsche has carefully controlled the pressure electronically in the 997.2. I for one don't care to start adjusting viscosity. I know that does not pertain to the 997.1 system. But the 997.2 is a significantly different animal.
I think I found how the 997.2 base and S control oil pressure.... it is called "Solenoid Valve" and is part #17 in the diagram 948 107 113 01. Other parts sites call this "Magnetic Valve" http://www.motorsab.com/es/producto/...a-magnetica/96
The way I understand these types of circulation systems, is that you have a pump, a sensor, and a regulator. The pump supplies more flow and or pressure than is required, the sensor measure pressure (in this case), and the regulator/control valve bleeds off excess pressure thus keeping an adequate pressure for whatever system. (Mass flow controllers regulate flow and not pressure.)
These systems have three variables: Pressure, fluid viscosity, and pipe diameter. Pressure is supplied by a pump. The result of these three items is flow. Change one and keep the others constant, flow changes. So, increasing pressure from the pump will increase flow and with a pump that spins with RPMs, more RPMs equal more pressure and therefore more flow. The regulator valve will control the pressure to not exceed a particular threshold.
If anything I just wrote is correct, then increasing the viscosity of your oil would decrease flow. If the system was designed to require a minimum particular flow, this would be completely fine if the system was "over designed" to allow for various viscosity values thus making a higher viscosity oil fine up to whatever design criterion spec'd for the system.
Anywho........ I was curious as to how this engine regulated pressure (or flow) and I think I found it with this part. Odd is it not called a "pressure relief valve" like on the other models. Assuming of course I have identified the correct part.
Bruce ... I believe you've got this pretty much right. I am attaching a few shots of pages from the Porsche Service Information 2009 Technik Introduction, All 911 Carrera Models (pages 20 to 23). This is a book I believe you would appreciate. Hopefully, if you can read these shots, your answer is there.
Sorry ... system crashes are frustrating. Don't seem to be able to load the photos. Maybe they will show up. Maybe they won't. By the time I can try again I'll bet this post goes to page 2 so I won't be able to access it at all. Order the book. It's good.
We have 5 oil pumps ... 4 extraction and a demand controlled pressure pump. The pressure pump is mapped for rpm and operating state (rpm, load, temp, anticipated rpm). It is located in the oil pan area (sump chamber) and is crankshaft driven via a chain. The DME controls the pump. There is a lot more in the book.
Bruce ... I believe you've got this pretty much right. I am attaching a few shots of pages from the Porsche Service Information 2009 Technik Introduction, All 911 Carrera Models (pages 20 to 23). ...
06-02-2015, 11:23 AM
Oil Pressure
