Too low oil pressure?

[jrwilson]

I'm running Rotella T5 (15-W40) in my car and I've noticed that when it gets nice and warmed up on a summer day the oil pressure will drop to .5 bar when it's at idle.

I'm wondering if I maybe need to go to a 20-W50 instead to get that pressure up.

[PeteKz]

As long as it jumps up as soon as you get above idle, that's fine. Old rule of thumb is 10psi per 1000 RPM. If it jumps to more than 20psi by 2000RPM, and climbs above that, I wouldn't worry about it. How hot is the oil temp when at .5bar/idle?

[jrwilson]

Originally Posted by PeteKz

How hot is the oil temp when at .5bar/idle?

About 150 or so.

My engine runs cold for some reason.

[dannobee]

Does yours have the updated cam line oil restrictors? Look for the groove in the middle. If no groove, they should be updated.

https://www.pelicanparts.com/More_Info/90110536102.htm?pn=901-105-361-02-OEM

[jrwilson]

The engine was rebuilt last year and they put the Carrera tensioners in, I can't imagine they'd skip updating the oil restrictors. I'll take a look though, thanks!

[RSTarga]

Many experienced mechanics don't like the oil restrictors.

[proporsche]

Originally Posted by RSTarga

Many experienced mechanics don't like the oil restrictors.

^^yup this^^^^^^

Ivan

JR: get yourself mineral oil 20W50 and you will be fine

[Schulisco]

Originally Posted by RSTarga

Many experienced mechanics don't like the oil restrictors.

Can you tell us why?

Thomas

[fanaudical]

The thought (as I understand it) is that the oil restrictors essentially reduce the oil flow to the cams and rockers.

[boyt911sc]

Originally Posted by fanaudical

The thought (as I understand it) is that the oil restrictors essentially reduce the oil flow to the cams and rockers.

I did some investigation about this subject and confirmed about the reduced flow of oil to the cams and rockers. Documented and verified.

Tony

[stownsen914]

Yes, well I guess restrictors would indeed do that!

To answer the OP's question about oil, switching to 20w50 isn't bad idea given your observation.

[Dpmulvan]

Originally Posted by Schulisco

Can you tell us why?

Thomas

They trust the engineers designed it that way for a reason, same goes for higher volume piston squirters et.

[Schulisco]

In general I also trust the engineers what they originally intended and how they designed it. But I'm also open to technical meaningful improvements to make things even better. And that's exactly what Porsche did for decades with these engines...

Here is a discussion started back in 2006 in the engine rebuild forum here and continued last year, with some interesting postings there, with statements among others from Henry Schmidt...

https://forums.pelicanparts.com/911-engine-rebuilding-forum/310463-cam-oil-line-restrictor-adapter-3.html

Also our host, Wayne Dempsey wrote in his book "How to Rebuild and Modify Porsche 911 Engines 1965-1989" in chapter 4 in section ""Performance upgrades" some things about the restrictors.
Summarized:

Initially the oil lines to the chain tensioners were connected with the well-known 90110536100. In 1991, the intermediate piece with the smaller passage was installed for the first time on the 964 Turbo, part number 90110536101 / 90110536102 (recognizable from the outside by a groove of the hexagon)

Reason: Foaming engine oil in the crankcase (due to the backflow from the camshaft housings)!!!

Apparently the PCA first came up with the idea of installing these new 90110536102 in older engines: The new spacers reduce the amount of oil that is pumped to the camshafts and from there flows unused back into the crankcase
This also reduces the amount of oil in the crankcase itself! Reason: This prevents the oil from foaming there due to the rotating crankshaft, with the effect that the oil pump also sucks in less air (foam contains air!), thus ensuring more constant filling of the oil tank and thus a stable oil circuit

Welcome side effects:
-Higher oil pressure throughout the engine
-More stable oil film in the bearings
-Higher oil pressure in the chain tensioners
-Better piston crown cooling

All in all: only advantages!

And so I replaced last summer the original two 90110536100 on my 1981 SC by two 90110536102 with reduced diameter holes (less than 3mm/~1/10 inch). The old ones are more than 5mms/0.2inch iirc. BTW: I had some trouble with the threads - I couldn't screw them in by hand because they blocked after half turn and they're made of steel and you screw them in an aluminium case... so I had to recut them to make them fit and then I could wrench them in easily by hand ...

Preliminary remark: I never saw the oil warn light when engine was hot, even on high summer temperatures! But when the engine was hot on a hot summer day the pressure on idle was pretty low...
My experiences in short: I can report significantly higher oil pressures, not only when engine is cold, but also when engine is hot!

Before installation the engine reached ~4bars with 20W50 mineral oil when running cold, but when warm far less than 1bar when running hot on idle on hot summer days as said. Oil preussre climbed little less than 1bar per 1000rpm as expected up to a little more than 3bars also on hot summer days...this made my concern... I also know my engine is old...

After installation of them I experienced a far better oil pressure when engine is warm, especially on high ambient summer temperatures above 30°C/86°F it keeps roughly 1 bar on idle and increases the pressure exemplary as designed with 1bar per 1000rpm up to more than 4bar on high revs as well. So I'm pretty happy with it now. Oil still the same 20W50, it wasn't replaced...

Also I can report that the engine indeed now runs cooler which I lead back to a better piston cooling due to spraying more oil especially on lower rpms to the their bottom and therefore the whole engine runs cooler now: The temperature gauge now climbs a little over 80°C / a bit over the white box of the oil temperature gauge, no matter if I cruise or wait at the traffic lights, but no more than 9 o'clock position on an inspired drive, before it climbed above 9 o'clock up to 10...

So there is no need for that much of oil on the camshafts as originally designed to be. There will still plenty of oil afterwards!

What I also expericed: The oil tank doesn't drain that much oil than before on WOT....the fluctuations are far less than before. A complete drain of it (in the gauge) I've never seen since...

I cannot recommend enough the usage of the new oil restrictors on all aircooled 911's with hydraulic chain tensioners, especially on high mileages (as mine is), because this ensures the oil to make it's job of lubricating and cooling where it is needed to be. Tuned and race engines are different, no question. But here the named pelican thread above also dicusses drilled restrictors to enhance the new ones a bit to get a good compromise for these engines as well.

Thomas

[HarryD]

Originally Posted by Schulisco

In general I also trust the engineers what they originally intended and how they designed it. But I'm also open to technical meaningful improvements to make things even better. And that's exactly what Porsche did for decades with these engines...

Here is a discussion started back in 2006 in the engine rebuild forum here and continued last year, with some interesting postings there, with statements among others from Henry Schmidt...

https://forums.pelicanparts.com/911-engine-rebuilding-forum/310463-cam-oil-line-restrictor-adapter-3.html

Also our host, Wayne Dempsey wrote in his book "How to Rebuild and Modify Porsche 911 Engines 1965-1989" in chapter 4 in section ""Performance upgrades" some things about the restrictors.
Summarized:

Initially the oil lines to the chain tensioners were connected with the well-known 90110536100. In 1991, the intermediate piece with the smaller passage was installed for the first time on the 964 Turbo, part number 90110536101 / 90110536102 (recognizable from the outside by a groove of the hexagon)

Reason: Foaming engine oil in the crankcase (due to the backflow from the camshaft housings)!!!

Apparently the PCA first came up with the idea of installing these new 90110536102 in older engines: The new spacers reduce the amount of oil that is pumped to the camshafts and from there flows unused back into the crankcase
This also reduces the amount of oil in the crankcase itself! Reason: This prevents the oil from foaming there due to the rotating crankshaft, with the effect that the oil pump also sucks in less air (foam contains air!), thus ensuring more constant filling of the oil tank and thus a stable oil circuit

Welcome side effects:
-Higher oil pressure throughout the engine
-More stable oil film in the bearings
-Higher oil pressure in the chain tensioners
-Better piston crown cooling

All in all: only advantages!

And so I replaced last summer the original two 90110536100 on my 1981 SC by two 90110536102 with reduced diameter holes (less than 3mm/~1/10 inch). The old ones are more than 5mms/0.2inch iirc. BTW: I had some trouble with the threads - I couldn't screw them in by hand because they blocked after half turn and they're made of steel and you screw them in an aluminium case... so I had to recut them to make them fit and then I could wrench them in easily by hand ...

Preliminary remark: I never saw the oil warn light when engine was hot, even on high summer temperatures! But when the engine was hot on a hot summer day the pressure on idle was pretty low...
My experiences in short: I can report significantly higher oil pressures, not only when engine is cold, but also when engine is hot!

Before installation the engine reached ~4bars with 20W50 mineral oil when running cold, but when warm far less than 1bar when running hot on idle on hot summer days as said. Oil preussre climbed little less than 1bar per 1000rpm as expected up to a little more than 3bars also on hot summer days...this made my concern... I also know my engine is old...

After installation of them I experienced a far better oil pressure when engine is warm, especially on high ambient summer temperatures above 30°C/86°F it keeps roughly 1 bar on idle and increases the pressure exemplary as designed with 1bar per 1000rpm up to more than 4bar on high revs as well. So I'm pretty happy with it now. Oil still the same 20W50, it wasn't replaced...

Also I can report that the engine indeed now runs cooler which I lead back to a better piston cooling due to spraying more oil especially on lower rpms to the their bottom and therefore the whole engine runs cooler now: The temperature gauge now climbs a little over 80°C / a bit over the white box of the oil temperature gauge, no matter if I cruise or wait at the traffic lights, but no more than 9 o'clock position on an inspired drive, before it climbed above 9 o'clock up to 10...

So there is no need for that much of oil on the camshafts as originally designed to be. There will still plenty of oil afterwards!

What I also expericed: The oil tank doesn't drain that much oil than before on WOT....the fluctuations are far less than before. A complete drain of it (in the gauge) I've never seen since...

I cannot recommend enough the usage of the new oil restrictors on all aircooled 911's with hydraulic chain tensioners, especially on high mileages (as mine is), because this ensures the oil to make it's job of lubricating and cooling where it is needed to be. Tuned and race engines are different, no question. But here the named pelican thread above also dicusses drilled restrictors to enhance the new ones a bit to get a good compromise for these engines as well.

Thomas

Interesting. My question has always been: “Why do I want to reduce cooling oil flow to the hottest part of my engine?”

I wonder if the oil pumps in cars later than mine actually pumped a greater volume of oil than the earlier one so while the flow to heads was reduced, the flow is still close to the original. I have never received an answer.

[pmax]

Originally Posted by jrwilson

I'm running Rotella T5 (15-W40) in my car and I've noticed that when it gets nice and warmed up on a summer day the oil pressure will drop to .5 bar when it's at idle.

I'm wondering if I maybe need to go to a 20-W50 instead to get that pressure up.

How old is that diesel oil ?

[930cabman]

Originally Posted by RSTarga

Many experienced mechanics don't like the oil restrictors.

They have done extensive testing and determined the oil restrictors are unnecessary.

What do the boys in Stuttgart know anyways?

[jrwilson]

I've since done an oil change with a different 20w50 oil and now it's at a nice 1bar even when hot.

[HarryD]

Originally Posted by jrwilson

I've since done an oil change with a different 20w50 oil and now it's at a nice 1bar even when hot.

What did you use?

[pmax]

When and how did the diesel oil misconception begin ?

[jrwilson]

Originally Posted by HarryD

What did you use?

Penn Grade 20w50.