997 Oil pressure question

[w00zie]

I've always had 993's and just graduated model wise and bought a used 2006 C4S (still have my beloved 993)

I'm not sure if this is a stupid question but my only reference until now have been my 993's

In my 06 C4S, when I start the car everything seems normal, oil pressure sits at 5, and as the car warm up, the highest hits about 4, 4.5. The strange thing is when revs are increased (during acceleration or downshifting) the pressure goes does. For example if my pressure is at 4.5, when i gear down and /or accelerate, it will go to 3.5, 4.

Is this normal? The dealer told me it was ok. I'm just used to my 993, where more gas = more pressure

Car just had an oil change, and i'm only putting 94 octane in it

Only mod to the car is a tubi exhaust

Thanks in advance for any help

[beauar]

the pressure should build with increased RPM's. The reading on oil pressure should be at about 3.5 bar with normal driving. under heavy acceleration it should go to the 5 bar range to lubricate the engine. It seems weird that your oil pressure goes down when your RPM's are going up. Am i understanding this right?

[w00zie]

the pressure should build with increased RPM's. The reading on oil pressure should be at about 3.5 bar with normal driving. under heavy acceleration it should go to the 5 bar range to lubricate the engine. It seems weird that your oil pressure goes down when your RPM's are going up. Am i understanding this right?

That's correct. Doing 60MPH/100KM in 3rd it sits at about 4/4.5, the minute i hit the gas to accelerate you can see the needle going down to 3.5/4. I let off the gas, and the needle goes back up again

[NelsonMX]

the pressure should build with increased RPM's. The reading on oil pressure should be at about 3.5 bar with normal driving. under heavy acceleration it should go to the 5 bar range to lubricate the engine. It seems weird that your oil pressure goes down when your RPM's are going up. Am i understanding this right?

That's correct. Doing 60MPH/100KM in 3rd it sits at about 4/4.5, the minute i hit the gas to accelerate you can see the needle going down to 3.5/4. I let off the gas, and the needle goes back up again

The 993 workshop manual states: oil pressure approximately 6.5 bar at 5,000 RPM with oil temp at 90 degrees C. Then in the next line it states the oil pressure indicator displays 0 to 5 bar.....Essentially at 5,000 RPM your gauge should read 5 bar. But remember they say approximately.......They do not specify the reading to be taken under heavy acceleration or deceleration for that matter. On all cars I have checked in the past I just drive the car up to a steady 5,000 RPM and check the oil pressure.......This could be done in any gear, but I would never check it under heavy accel or decel as the rapid change of oil flow in the system would cause a fluctuation of pressure.....

The oil systems in theses cars are unregulated, and this is why we see the pressure change with RPM......(They do have overpressure relief by the way.....at approximately 6.5 bar)

Sorry, I just realized I was referring to the 993 and you are now the proud owner of a 997.....In any case the same still applies. You should have 5 bar at 5,000 RPM at 90 degrees C.....This is stated in the 997 shop manual. Again I would take the reading at a steady 5,000 RPM, not accel or decel.

Hope this is of some help...

Regards,

Robert

Edited July 13, 2009 by NelsonMX

[w00zie]

Thanks for the info, went out for a drive and tried it

993 is right on the ball

The 997 however is a different story. At 65 deg (or cold start/drive) it hits 5 bar @ 5000rpm

At 90 deg and steady 5000rpm it's 4.5

Again, even the slightest acceleration bring it down and when it steadies off, it goes back to 4.5.

My car is going in for the 60k maint next week so i'll get them to check it out

[155mph]

Just found this in the 997 owners manual

"With the engine warmed up and running at a speed

of 5000 rpm, the engine oil pressure should be

approx. 3.5 bar.

[RFM]

997 series 1 with M97 engine use approx. the same oil pump and pressure as the latest 996, the 997 series 2 with MA101/102 DFI engine use a "demand-controlled oil pump" depending on the input for engine speed, load, engine oil temp. etc. the oil pressure control valve possition is defined using a map in the DME. The phenomenon you describes is possible if the car is a series 2.

[t32b]

The actual numbers at any given temp/rpm/load have some variance in them between cars, so a specific citing is immaterial unless the pressure drops to the lower end of the scale. On the other hand, pressure readings that move inversely to RPM's is definitely not normal. If at all possible, I would have the car examined under warranty to see of there are any blockages or other problems. When was the oil/filter last changed? It could be (and this is really theoretical) that under high rpms some vacuum (caused by restricted flow) is affecting the reading and your actual pressure. I'd be concerned. But then again, I'm a worrier. :)

[w00zie]

The actual numbers at any given temp/rpm/load have some variance in them between cars, so a specific citing is immaterial unless the pressure drops to the lower end of the scale. On the other hand, pressure readings that move inversely to RPM's is definitely not normal. If at all possible, I would have the car examined under warranty to see of there are any blockages or other problems. When was the oil/filter last changed? It could be (and this is really theoretical) that under high rpms some vacuum (caused by restricted flow) is affecting the reading and your actual pressure. I'd be concerned. But then again, I'm a worrier. :)

Oil change was done 500 miles ago.

It's going in this Wed for it's regular maintenance, and this will be on the list of things to check

Thanks!

J

[ILIASGK74]

yesterday i pickup my 997 4s mod06

in very low speed oil pressure is about 3,5 and in all my trip of about 1000km was 5.

is this normal?

i was driving with 160km/h most.

[355bhp]

Ah! Que BELLA macchina! I think I'll have my wheels painted black too. And the oil pressure sounds fine to me. Cheers!

[w00zie]

Took car to dealer today and the verdict was the oil sending unit was defective

Hope this helps anyone else with this issue

Also, (as i've seen this posted elsewhere) I had a really bad and LOUD creak coming out of the front drivers wheel which only appeared when the car was warmed up.....REALLY ANNOYING,and made me feel like the front wheel was going to fall off...well it turns out it was the inner tie rod and control arm

My dealer was good and everything was covered under warranty, which is good, since my friend went to the other dealer in town with a similar tie rod issue and they made him pay for it as they said it was caused by normal wear and tear

J

[ianwallwork]

Keep a VERY close eye on this one. If you're getting a reduction in oil pressure under acceleration, it could mean that the engine's being starved of oil. I had the very same problem on a 996. The stealer also thought this was a faulty sender, but a new one made very little difference. The real problem was quite difficult to diagnose.

What was happening? Simply there wasn't enough oil in the sump under running conditions. It was OK with the engine off, but whilst running, the level was going dangerously low and the oil pickup was being starved of oil. How? Good question! The M96/7 engines have 3 oil pumps. The main one that picks up oil from the sump and pushes it round the engine under pressure and one in each of the cylinder heads that 'scavenge' oil from the heads and return it to the sump. It needs these scavenge pumps as gravity won't return oil to the sump from the 'outside' cylinder head when cornering (amongst other things). On my car one of these scavenge pumps had failed and oil wasn't getting back to the sump as fast as it was being pumped out of it. On the level, it was just about OK (like your car) but as soon as the oil in the pan surged under acceleration or cornering, it shifted away from the pickup and pressure was lost.

Replacement of the scavenge pump restored things immediately to normal. I've never heard of a similar failure before or since but it's possible!

Ian

[ILIASGK74]

Ah! Que BELLA macchina! I think I'll have my wheels painted black too. And the oil pressure sounds fine to me. Cheers!

thanks ! :D