[YellowChicken]

Question from a FLAT4 new owner: I notice that the max boost I can get is 0.8b while the oil pressure jumps to the red zone with more than 4b... Is this what is expected for a 718S? I'm really concerned about these figures... Thanks for your feedback.
Cheers

 

[jimmuller]

The oil pressure is always higher when the engine is cold. Let it warm before rev'ing up so high. Even when warm the oil pressure may go up to the red zone at high rev's. Oil pressure depends on only two things, rpm's and oil temperature. It's okay as long as you aren't running up there all the time.

The boost gauge will rarely show much more than 0 most of the time. If you depress the accelerator very much at low rpm's, especially in a higher gear, you can see it climb. Unless you hold your foot down it relaxes pretty quickly. The boost isn't so much rpm-dependent as raw acceleration-dependent.

 

[YellowChicken]

The oil pressure is always higher when the engine is cold. Let it warm before rev'ing up so high. Even when warm the oil pressure may go up to the red zone at high rev's. Oil pressure depends on only two things, rpm's and oil temperature. It's okay as long as you aren't running up there all the time.

The boost gauge will rarely show much more than 0 most of the time. If you depress the accelerator very much at low rpm's, especially in a higher gear, you can see it climb. Unless you hold your foot down it relaxes pretty quickly. The boost isn't so much rpm-dependent as raw acceleration-dependent.

Thanks for your reply. Sorry, I think my questions were not clear, let me clarify them. I'm talking about the max (instant) oil pressure upon high acceleration. The pressure gauge goes into the red section above 4.7 b (> 68 psi). I found it surprising. On track the oil pressure would be quite often (always) in the red zone, I don't remember similar thing with my five previous NA Porsches...
Even more surprising to me, is the (instant) boost pressure upon max acceleration (and, of course, with a warm engine - I would definitely do not do this with a cold engine). Porsche indicates that CS's max boost pressure is 1-1.1 b (14.5-16 psi). Mine goes up to 0.8 b (11,6 psi) at best. I was accordingly wondering if some power was missing and would be interested in knowing what other owners of CS (or BS) read as max boost pressure (and max oil pressure) with the foot down (on the gas pedal )

Cheers

 

[YellowChicken]

Answering my question myself ? . I found this video

showing that boost pressure oscillates between 0,7-0,9 b which is consistent with my own experience. Now regarding the oil pressure it goes up to 4.4-4.5 but never enters into the red zone while it does with me. May be different oil specs...

 

[HooosierDaddy]

Answering my question myself ? . I found this video

showing that boost pressure oscillates between 0,7-0,9 b which is consistent with my own experience. Now regarding the oil pressure it goes up to 4.4-4.5 but never enters into the red zone while it does with me. May be different oil specs...

I'm getting the same boost pressures.

I did notice when I bought my car the oil pressure was consistently high and my boost pressure never showed much until the car was pushed. I bought my car from a non-Porsche dealer and wasn't confident that they used the proper spec fluids. I took the car in for oil and filter change and noticed instantly the lower oil pressure and boost gauge is more active. Not seeing any more boost but i definitely see the gauge showing boost sooner than it previously did.

 

[reiver]

Living in Phoenix area I was concerned with the 0/40 weight and our serious summer temps so called Jack at Stuttgart SW for a chat. He said it took a bit to wrap his brain around (Porsche shop owner 45 years) but he recommends the 0/40 and not the also listed 5/40...due to the internal oil gallery layout and size....designed a bit restrictive for that weight of oil so any heavier blend will raise oil pressures....is this your issue I've no idea...

 

[sobiloff]

He said it took a bit to wrap his brain around (Porsche shop owner 45 years) but he recommends the 0/40 and not the also listed 5/40...due to the internal oil gallery layout and size....designed a bit restrictive for that weight of oil so any heavier blend will raise oil pressures....is this your issue I've no idea...

I don't agree with that reasoning. Both oils are 40-weight at operating temperature, so the only time they behave differently is when the engine oil isn't up to temp yet. That W difference between them is small (250 cP), and most oils rapidly shear out of the 0W and become 5W (or even 10W) during their service life anyway.

I'd instead remind that different brands of 40-weight oil have different viscosities at operating temperature (the range is 12.5 to 16.3 cSt), and even the same oil at the start of its service life will have a different viscosity than at the end of that service interval. That may be what is responsible for the different oil pressures folks are seeing. (No one's said what oil they're actually using, though, so I can't say for certain whether this is the root cause of the differences we're discussing, or not.)

As for the boost pressure, the ECU limits the amount of boost needed to produce a certain power output. If you're at lower altitudes the turbo won't need to produce as much boost to create the desired power; at higher altitudes it'll need to create more boost to reach that same power output. So, I wouldn't worry too much about not seeing the maximum boost pressure.

 

[jimmuller]

I took the car in for oil and filter change and noticed instantly the lower oil pressure and boost gauge is more active. Not seeing any more boost but i definitely see the gauge showing boost sooner than it previously did.

I have a hard time believing that new oil made the turbo boost come on sooner or more often. You sure you aren't driving differently?

 

[HooosierDaddy]

I have a hard time believing that new oil made the turbo boost come on sooner or more often. You sure you aren't driving differently?

Placebo effect? It's possible!

My car was serviced at an independent shop prior to purchase and I can only conclude that they used the wrong kind of oil. Reason for my hypothesis is that my car made the same knocking and clattering that all the porsche's do after they've sat for a while... except it didn't go away until I was 30 minutes into driving and it did it at every start where the engine was able to cool down. That is not normal and I'm only left to believe that they used too heavy of a weight of oil. Could that affect the spooling of the turbo? I will say that I notice ZERO difference in performance, only that my gages are more active. Same boost levels and lower max oil PSI.

 

[roundtail]

and most oils rapidly shear out of the 0W and become 5W (or even 10W) during their service life anyway.

Wait a minute. I thought shearing referred to polymer shearing that resulted in lower viscosity at temperature. Is that not correct? What you’re saying is that the base viscosity is rising as a result, if I read that right.

 

[phroenips]

Wait a minute. I thought shearing referred to polymer shearing that resulted in lower viscosity at temperature. Is that not correct? What you’re saying is that the base viscosity is rising as a result, if I read that right.

My understanding is the same as yours. Shearing effectively reduces the viscosity over time.

 

[sobiloff]

@roundtail and @phroenips: Time and heat are the primary enemies of the pour point depressants that determine the winter rating of an oil. Oils get hammered at both ends when in service—their base components get thinned, dropping them out of grade, and their PPDs get damaged and they don't maintain their W rating. Apologies for my confusing word choice above.