Jeff N.

No love in the archives. There is one post re this but no conclusion.

Situation: About 10 to 15 minutes into a track session, I notice a slight drop in the oil pressure during hard acceleration. Typical pressure on the factory gauge is just a tick over 4 bar and during hard accel it drops to just a tick under 4 bar.

My (paranoid internal) voice suggests to me this could be worn main or rod bearings but wanted to get some opinions from experienced builders. Trying hard to avoid becoming a member of the I Spun the #2 Bearing Club.

Here's some additional details.

- 86 turbo, stock turbo running 15psi with a MBC and tial wastegate
- 187k on the motor
- PO did a light rebuild at 140k including rings, rod bearings and refreshed the head, installed an oil pan baffle
- car has been updated to a one piece OPRV.
- car has a second oil cooler installed, series setup with 10AN lines
- running Mobil 1 15w-50 synthetic
- oil temps are about 210 or 220 (pan measured)
- car runs strong, have some slight oil consumption but it's mostly via a worn turbo bearing
- startup cold oil pressure is about 4.5 bar
- hot off track oil pressure is about 2 bar

Hoping not to re-open the Mobil One Sucks discussion. So, if you're thinking the oil is the problem, helpful data would be your experience with switching oil brands and the resultant OP changes.

Thanks in advance!

Jeff

Bri Bro

I used Mobile one several years ago and noticed right off that my oil pressure was reduced after about 10 minutes on the track. Switched oil and no more problem.

carreracoupe997

Joe Gibbs Racing Oil...SP4 is what I use but they have many others including synthetic. You will be sooooooooooooo happy.

jb-kix

had the same problem ,car is in the shop now,they found that the pickup tube seal was bulging out and sucking alittle air.im in arlington wash.what track do you go to id like to check it out.

333pg333

Apparently Mobil have finally relented and re introduced some oils with ZDDP but you should check what yours has in it. Personally....ahh forget it...

mikey_audiogeek

Jeff, might pay to check your oil pressure with a mechanical gauge as well.

Jeff N.

Mikey - yes, that's been a thought.

JB - PM for some details...easier to talk offline on that. Interesting on the oil pickup...

Re suggestions to change the oil, I appreciate that. However, how would an oil change impact a pressure change on accel? I can see how an oil change might impact total pressure at a selected temp but have a harder time seeing how an oil change would impact a drop of pressure on accel.

Again, here's what's happening - at slight accel, i have a bit over 4 bar. At full boost, i have a bit less than 4 bar. It's repeatable.

mikey_audiogeek

Jeff, my car has similar symptoms, haven't followed my own advice yet

the oil pickup tube seal is good thinking!

Mike

Chris White

A slight drop in oil pressure during acceleration is fairly normal.
Don’t worry about it.

Jeff N.

Thx Chris. Any idea why this occurs? I can only speculate this is due the loading on the crank and rods changing bearing clearances somewhat....can't be great but ???

What to you consider the "minimum" threshold for oil pressure when driven on the track? After a fair amount of archive reading, seems like the consensus is about 4bar.

BTW, I still am looking to get a backup OP gauge in the car....as you can tell, still a bit oil pressure paranoid after all I have been through.

Thanks!

Chris White

Lots of possible reasons – change in clearance, movement of crank against thrust bearing, gremlins….

Porsche’s guide line is pretty good - 1 bar per 1k RPM minimum. This makes sense for lower RPM but once you get over 3 bar (45 psi) it doesn’t really matter. The important thing to watch is the change in max warm pressure – this will tell you how hot your oil is getting. I have seen cars that typically ran 4 bar warm drop to 3 bar or a little less when ‘hot’ after a 30 minute session. Oil was way too hot.

A ‘real’ oil pressure gauge is a good idea. The stock sender / gauge is known to be a little odd – especially with 20 year old wires!

sebastian944

I thought when warm dropping oil pressure to 3 bar was normal at idle? when warm my oil pressure some times dips to 2.5 to 3 at idle.. but when revving it's always 1 bar above each 1k rpm.

Chris White

I meant 3 bar at higher RPM and load - not 3 bar at idle. 3 bar at idle is good!