Possible cure for #2 bearing failure - Page 2 - Rennlist - Porsche Discussion Forums

Notices
924/931/944/951/968 Forum
Sponsored by:
Sponsored by:

Possible cure for #2 bearing failure

Old 01-08-2019, 04:40 PM
  #16  
Otto Mechanic
Rennlist Member
 
Otto Mechanic's Avatar
 
Join Date: Jan 2015
Location: Paso Robles, CA (Under the lift)
Posts: 2,615
Default

Originally Posted by V2Rocket View Post
lots of fixes to try. dry sump certainly addresses many of them for the $$$$
For my own part, this seems the most likely "fix" and the one I plan to pursue first. I've been looking seriously at the Accusump system, though I've also heard the 3L 16V motor I have in the S2 is less prone to this problem?

Last edited by Otto Mechanic; 01-08-2019 at 05:29 PM.
Otto Mechanic is offline  
Old 01-08-2019, 05:44 PM
  #17  
V2Rocket
Rainman
Rennlist Member
 
V2Rocket's Avatar
 
Join Date: Jan 2007
Location: Rancho Cucamonga, CA
Posts: 42,162
Default

Not sure the Accusump would do very much except maybe hold the system oil pressure up once a bearing has spun, which might get you a little closer to home as long as the pressure reserve lasts?
V2Rocket is offline  
Old 01-08-2019, 06:03 PM
  #18  
Otto Mechanic
Rennlist Member
 
Otto Mechanic's Avatar
 
Join Date: Jan 2015
Location: Paso Robles, CA (Under the lift)
Posts: 2,615
Default

Originally Posted by V2Rocket View Post
Not sure the Accusump would do very much except maybe hold the system oil pressure up once a bearing has spun, which might get you a little closer to home as long as the pressure reserve lasts?
As I understand the Accusump, it preserves oil pressure during brief periods of pump starvation, like the ones that might happen in a long turn at high Gs? I admit that's an opinion not founded in personal experience, but it's my understanding of how and why the system works to defend against this #2 oiling problem?

Last edited by Otto Mechanic; 01-08-2019 at 10:54 PM. Reason: Punctuation
Otto Mechanic is offline  
Old 01-08-2019, 06:05 PM
  #19  
H.F.B.
User
 
H.F.B.'s Avatar
 
Join Date: Jul 2013
Location: Germany
Posts: 324
Default

Flat out for 24 hours, no #2 bearing issues

Flat out for 24 hours :-)
H.F.B. is offline  
Old 01-08-2019, 06:40 PM
  #20  
aussie944cab
User
 
Join Date: Mar 2016
Posts: 109
Default

Another theory is that air is more inclined to go round corners (being lighter than the oil) and this causes aerated oil going to no. bearing, as explained in this article
https://newhillgarage.com/2013/06/25...tem-explained/
aussie944cab is offline  
Old 01-08-2019, 06:51 PM
  #21  
mrgreenjeans
User
 
mrgreenjeans's Avatar
 
Join Date: Dec 2012
Location: Marco Island , FL --- Red River Valley, midwest
Posts: 1,261
Default

Originally Posted by V2Rocket View Post
lots of potential issues...
- oil pump starvation during long turns
- insufficient oil drain-back from the heads (serious problem on 928s)
- too many 90-degree turns in the oil galley after oil filter (filtered oil has a straight shot at #1 main and whats left goes to the other mains)
- OPRV bypass potentially allowing air bubbles into the pump feed
- AOS "return path" with potentially still air-entrained oil is right next to the pump pickup.

lots of fixes to try. dry sump certainly addresses many of them for the $$$$
- sump baffles
- slight vac in crank case (dedicated vac pump or dry sump scavenge)
- add external oil lines to feed the main galley more evenly after the filter?
- direct AOS drain away from pump pickup.

biggest first steps, IMO after breaking down a number of "failed" engines...
- better oil cooling
- better oil (xW50 minimum, not that 0Wx pisswater that Odurandina recommends)
THIS .....

Reread the bottom paragraph and apply to your own situation.

( own a number of 944 and 951 2.5 liter engine Porsches and have never had a bearing issue. Ever.
On track or on the street. Pulled one set at 80,000 miles and after nearly 5,000 miles of track events at WOT, the #2 looked new. It is all about the oil, it remaining clean, and it's cooling if you want the 'insurance' )

I have used Mobil 1 - 20/50 and 15/50 synthetic and Racing oil since new on several, and used it since purchase on the rest. All have their original engines, one with 180,000 miles. On the track cars, added cooling is the answer to lowering oil temps further
mrgreenjeans is offline  
Old 01-08-2019, 07:10 PM
  #22  
Otto Mechanic
Rennlist Member
 
Otto Mechanic's Avatar
 
Join Date: Jan 2015
Location: Paso Robles, CA (Under the lift)
Posts: 2,615
Default

Originally Posted by H.F.B. View Post
Flat out for 24 hours, no #2 bearing issuesFlat out for 24 hours :-)
Which is consistent with my understanding the 3L 16V motor used in the S2 and 968 (S3) doesn't suffer from the #2 oiling problem experienced by earlier designs?
Otto Mechanic is offline  
Old 01-08-2019, 07:20 PM
  #23  
V2Rocket
Rainman
Rennlist Member
 
V2Rocket's Avatar
 
Join Date: Jan 2007
Location: Rancho Cucamonga, CA
Posts: 42,162
Default

Re: Nardo...
https://en.wikipedia.org/wiki/Nard%C3%B2_Ring
In the cars/motorcycle ring the lanes are banked at such a degree that a driver in the outer most lane doesn't need to turn the wheel while driving at speeds of up to 240 km/h (149 mph). In essence, at the so-called neutral speed which is different for the four lanes, one can drive as if in a straight lane.
Nothing really different about the 3.0 oiling system vs the 2.5.
They got those breathing ports between up/down cylinders which might help a little but is more useful for "pumping losses".
They got the updated oil pan "scrapers" but earlier models had those too.
V2Rocket is offline  
Old 01-08-2019, 07:58 PM
  #24  
T&T Racing
Addict
Rennlist Member
 
T&T Racing's Avatar
 
Join Date: Jan 2012
Location: New York & Indiana
Posts: 552
Default

Originally Posted by Otto Mechanic View Post
For my own part, this seems the most likely "fix" and the one I plan to pursue first. I've been looking seriously at the Accusump system, though I've also heard the 3L 16V motor I have in the S2 is less prone to this problem?
Accumsump works only when the oil pressure drops below a certain pressure and the trigger pressure has to last long enough to activate the low pressure switch. The starvation of #2 rod bearing,and possible transient low oil pressure probably not detected by low pressure switch of Accumsump.

Save your money or take the savings and do an upgrade to that benefits you and the car's performance
T&T Racing is offline  
Old 01-08-2019, 08:06 PM
  #25  
Otto Mechanic
Rennlist Member
 
Otto Mechanic's Avatar
 
Join Date: Jan 2015
Location: Paso Robles, CA (Under the lift)
Posts: 2,615
Default

Originally Posted by T&T Racing View Post
Save your money or take the savings and do an upgrade to that benefits you and the car's performance
I'm always fond of saving money (that's why I race old cars )

I'm certainly open to sage advice on the subject?
Otto Mechanic is offline  
Old 01-08-2019, 11:30 PM
  #26  
Nowanker
User
 
Join Date: Sep 2017
Location: Sunny Morgan Hill
Posts: 51
Default

My deductions, after lots of research way back in the day:
The root cause of the failure is air in the oil, with too many 90* turns in the circuit squeezing the air out unevenly, affecting #2 first.
Baffled oil pan and air-oil separator...
One shop was using an external oil manifold, with individual branches to each main. I never actually saw it, but they swore by it.
3 liter blocks do have a different oil galley design, with the main bearing feeds not intersecting the galley straight on, but slightly offset, effectively increasing the cross section of the passage at that spot.
944 oil pumps are massively over capacity.... my pressure relief stuck shut once, and I watched the gauge go all the way around and back to 60 before the oil cooler blew up.
I used to run an Accusump on my race car for insurance. I suffered cracked oil pickups 2 seasons in a row, with corresponding bearing damage. Noticed ever-so-slightly lower oil pressure at hot idle, but above idle, oil pressure was as always.
It will pump foamy air just fine... the Accusump would never know to discharge so I ditched it as useless.

951 and 944s: what's your race car solution?
Nowanker is offline  
Old 01-08-2019, 11:42 PM
  #27  
Nowanker
User
 
Join Date: Sep 2017
Location: Sunny Morgan Hill
Posts: 51
Default

Originally Posted by aussie944cab View Post
Another theory is that air is more inclined to go round corners (being lighter than the oil) and this causes aerated oil going to no. bearing, as explained in this article
https://newhillgarage.com/2013/06/25...tem-explained/
^^This article pretty much exactly echoes my aerated oil/tortured oil pathways theory.
With the exception of the source of the air in the first place... uncovered oil pickup seems more logical.
It still amazes me that the oil can even find its way back to the oil pan on a road course.
Nowanker is offline  
Old 01-09-2019, 01:40 AM
  #28  
Otto Mechanic
Rennlist Member
 
Otto Mechanic's Avatar
 
Join Date: Jan 2015
Location: Paso Robles, CA (Under the lift)
Posts: 2,615
Default

Originally Posted by T&T Racing View Post
Accumsump works only when the oil pressure drops below a certain pressure and the trigger pressure has to last long enough to activate the low pressure switch. The starvation of #2 rod bearing,and possible transient low oil pressure probably not detected by low pressure switch of Accumsump.

Save your money or take the savings and do an upgrade to that benefits you and the car's performance
I can't say this brings me joy. I'd honestly hoped there was a reasonably priced solution to this problem, maybe I was a bit overly optimistic.

I'll continue the search. Are there other dry sump systems you think superior and might fix this?

Best Regards,
Otto Mechanic is offline  
Old 01-09-2019, 02:23 AM
  #29  
Otto Mechanic
Rennlist Member
 
Otto Mechanic's Avatar
 
Join Date: Jan 2015
Location: Paso Robles, CA (Under the lift)
Posts: 2,615
Default

I'm sort of thinking this subject should be cross posted to the 928 forum? Anyone know how to do that?
Otto Mechanic is offline  
Old 01-09-2019, 10:35 AM
  #30  
951and944S
Super User
 
951and944S's Avatar
 
Join Date: Dec 2001
Location: New Orleans/Baton Rouge
Posts: 3,239
Default

Originally Posted by Nowanker View Post

951 and 944s: what's your race car solution?
Well, contributions to these kind of threads are so scattered around the 944/951/968 that I can't find even my own posts but being as this thread is aptly named, I think I'll go over some of the ideas I have have here in this one spot.

My own interest was piqued because I am building a new race engine with substantially more $$ investment than the prior cars/engines we race, so I wanted to personally separate the myth from reality.

Currently though, we race an 8V 944 (since it seems to be an opinion that this is the main contributing factor) at a cornering G level equal to any other 944 being raced, with 1)excessive oil cooler, 2)baffled oil pan, 3)Michael Mount coated race bearing 4)SwepCo 20/50 with anti foaming agent.

Brutal rpms and cornering at the front of the class pack of every session, never lost a rod bearing in 10 years.

Not enough time to get into long winded detail of each separate aspect at the moment, but I will be back.

T



951and944S is offline  

Thread Tools
Search this Thread

Contact Us About Us Advertising Cookie Policy Privacy Statement Terms of Service

© 2018 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: