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BMW S54 Rod Bearing Oil Pressures #4579656
11/20/17 01:36 AM
11/20/17 01:36 AM
Joined: Nov 2017
Posts: 4
South Africa
SlipperySimon Offline OP
SlipperySimon  Offline OP
Joined: Nov 2017
Posts: 4
South Africa
Greetings all! This is my first post.. I've been following this BITOG forum for many years as a guest...a tremendous wealth of knowledge on this forum! I've been searching the forums for over an hour and haven't come across anyone that's answered this issue adequately, and I'm thinking that this could be a solution for all S54 owners:

As the engine-builder's rule of thumb goes, one should have around 10 psi oil pressure per 1000RPM for standard bearing widths.

As we are all too familiar with, our rod bearings are narrower than the typical rod bearing found in cars.

One can then safely assume then that there's no way our bearings should be experiencing anything under 10psi/1000RPM, and, if anything, should be set to at least 12-14psi/1000RPM.

After taking a look at the TIS documents on checking oil pressure on the S54, it is clearly stipulated that there should be minimum 0.7bar (10.1 psi) at idle speed at operating temperature. It then goes to say that the pressure is then regulated to a constant 4bar (58 psi). This pressure is regulated by a sprung piston situated in the oil pump which limits the output pressure to a maximum of 4bar (58psi), (experts please step in and correct me if I'm wrong here).

At this point it becomes apparent that the bearings are under-lubricated at RPMs over 4800RPM (using a conservative guideline that 12psi are required per 1000RPM)

This makes me think that a far simpler solution to eliminate the rod bearing issues would be to remove the oil pump pressure regulator, or at least modify the existing setup to maintain higher oil pressures at the higher rpm.

1. Does anyone have experience with this or considered this?

2. Why would BMW fit a pressure regulator to the oil pump in the first place?

I just find it really bizarre how this could have been overlooked by the engineers in Germany, as this is the 101 of engine building, and I must be missing something...

Re: BMW S54 Rod Bearing Oil Pressures [Re: SlipperySimon] #4579661
11/20/17 02:32 AM
11/20/17 02:32 AM
Joined: Aug 2006
Posts: 9,801
Central Washington
Colt45ws Offline
Colt45ws  Offline
Joined: Aug 2006
Posts: 9,801
Central Washington
To increase the pressure, just fit a heavier spring into the pressure regulator. This may or may not be easy depending on its location. You may also be able to 'space' the stock spring tighter with something behind it so it puts more force on the valve, but you have to make sure the valve can still reach its full open position before you bind the coils of the spring.
You need to regulate the pressure to prevent the pump from being damaged by high pressure. Its a positive displacement type pump, which means every rotation it outputs X ccs of fluid. If the oil is cold, there will be quite a lot of resistance to flow through the oil galleries. The pump will keep pumping the same amount fluid in on every rotation increasing the pressure until something gives.

Last edited by Colt45ws; 11/20/17 02:34 AM.

-Colton
2002 Ford Crown Vic PI 207k, Ex-Kootenai County, ID Unit #42
Down for engine swap
2003 Ford Crown Vic PI 75k
Castrol EDGE HM 5W30, Fram XG2
Re: BMW S54 Rod Bearing Oil Pressures [Re: SlipperySimon] #4579699
11/20/17 05:45 AM
11/20/17 05:45 AM
Joined: Feb 2014
Posts: 593
Margate England
Claud Offline
Claud  Offline
Joined: Feb 2014
Posts: 593
Margate England
I would hazard a guess that if BMW think 4 bar is fine then it probably is.
Oil flow is just as important as just pressure. The oil at the bearings need to be constantly replaced to keep the bearing cooled.
If you plug the relief valve my money is on the filter bursting from a cold start, maybe with the oil pump drive breaking as a covering bet.

Claud.

Re: BMW S54 Rod Bearing Oil Pressures [Re: Claud] #4579700
11/20/17 05:49 AM
11/20/17 05:49 AM
Joined: Dec 2002
Posts: 40,845
'Stralia
Shannow Online content
Shannow  Online Content
Joined: Dec 2002
Posts: 40,845
'Stralia
Originally Posted By: Claud
I would hazard a guess that if BMW think 4 bar is fine then it probably is.
Oil flow is just as important as just pressure. The oil at the bearings need to be constantly replaced to keep the bearing cooled.


The temperature in the big end is DUE to the viscous friction in the bearing and the oil.

Heat flow is OUT of the bearing, and into both the con-rod and crankshaft at high RPM.

There has to be enough oil available to replenish the side leakage ...

Re: BMW S54 Rod Bearing Oil Pressures [Re: Shannow] #4579720
11/20/17 06:34 AM
11/20/17 06:34 AM
Joined: Feb 2014
Posts: 593
Margate England
Claud Offline
Claud  Offline
Joined: Feb 2014
Posts: 593
Margate England
Originally Posted By: Shannow
Originally Posted By: Claud
I would hazard a guess that if BMW think 4 bar is fine then it probably is.
Oil flow is just as important as just pressure. The oil at the bearings need to be constantly replaced to keep the bearing cooled.


The temperature in the big end is DUE to the viscous friction in the bearing and the oil.

Heat flow is OUT of the bearing, and into both the con-rod and crankshaft at high RPM.

There has to be enough oil available to replenish the side leakage ...


Absolutely, the hot oil needs to be replaced before it breaks down.

Claud.

Re: BMW S54 Rod Bearing Oil Pressures [Re: SlipperySimon] #4579725
11/20/17 06:43 AM
11/20/17 06:43 AM
Joined: Aug 2008
Posts: 18,326
Ontario, Canada
StevieC Offline
StevieC  Offline
Joined: Aug 2008
Posts: 18,326
Ontario, Canada
welcome to BITOG Simon


'18 Highlander - AMSOIL SS 0w20 / ATF / Severe Gear
'06 Santa Fe - 535,000km AMSOIL SS 0w30 / ATF (R.I.P)
Re: BMW S54 Rod Bearing Oil Pressures [Re: SlipperySimon] #4579917
11/20/17 11:08 AM
11/20/17 11:08 AM
Joined: Apr 2008
Posts: 37,095
Ontario, Canada
OVERKILL Offline
OVERKILL  Offline
Joined: Apr 2008
Posts: 37,095
Ontario, Canada
IIRC, the 10psi "rule" applies to the Small Block Chevrolet and is not some universal guideline.

The oil pressure relief spec pressure simply means that the bypass cracks at that point, it doesn't mean that's the maximum pressure you are going to see. It is very possible; probable even, to observe pressures significantly higher than the relief as the pump over-drives the relief circuit and continues to build pressure in the rest of the system.


2018 RAM 1500 Big Horn EcoDiesel
2016 Grand Cherokee SRT
Re: BMW S54 Rod Bearing Oil Pressures [Re: SlipperySimon] #4579932
11/20/17 11:19 AM
11/20/17 11:19 AM
Joined: Sep 2015
Posts: 5,846
Kalifornia Kollective
BrocLuno Offline
BrocLuno  Offline
Joined: Sep 2015
Posts: 5,846
Kalifornia Kollective
+1 smile

And, yes and no. Most USA V8's have somewhat similar bearing sizes, so it has become a rule of thumb for USA engines. But all bets are off on bearings with other sizes and different clearances...

I'd just run a good high HTHS oil in the appropriate grade and keep it clean. If you want to do track days, think about loosening the clearances by a few thou and be done with it laugh

Last edited by BrocLuno; 11/20/17 11:19 AM.

Formerly in marine engineering. In an earlier life I owned my own petroleum tank truck, and hauled for the majors and independent's.
Re: BMW S54 Rod Bearing Oil Pressures [Re: SlipperySimon] #4580006
11/20/17 12:30 PM
11/20/17 12:30 PM
Joined: Sep 2004
Posts: 7,518
Marshfield , MA
andyd Offline
andyd  Offline
Joined: Sep 2004
Posts: 7,518
Marshfield , MA
The displacement 3.2L is the same as the the M30 in my '83 533i that puts out only 160 hp. The trouble is that oil needs to changed more often. These cars are victims of poor care and hard usage. Most have a tender cooling system that contributes to overheats.Replacing plastic parts before 100K is advisable. Having a tank split open at full hoon will often result in a major overheat. Something about the new stuff being more bio degradable in the waste stream.


'16 Camry LE STP synth 0w20 and STP filter. the Fridge

1994 Ranger ,the Rat, 5w30 dino, STP filter

'16 Camry SE, Valvoline HM 0w20 and OEM filter
Thick oil is better grin2
Re: BMW S54 Rod Bearing Oil Pressures [Re: SlipperySimon] #4580012
11/20/17 12:34 PM
11/20/17 12:34 PM
Joined: Sep 2015
Posts: 5,846
Kalifornia Kollective
BrocLuno Offline
BrocLuno  Offline
Joined: Sep 2015
Posts: 5,846
Kalifornia Kollective
More biodegradable yes, but it starts as soon as they roll off the line ... frown


Formerly in marine engineering. In an earlier life I owned my own petroleum tank truck, and hauled for the majors and independent's.
Re: BMW S54 Rod Bearing Oil Pressures [Re: SlipperySimon] #4580029
11/20/17 12:47 PM
11/20/17 12:47 PM
Joined: May 2009
Posts: 12,186
N.H, U.S.A.
ARCOgraphite Offline
ARCOgraphite  Offline
Joined: May 2009
Posts: 12,186
N.H, U.S.A.
Worry more about HTHS rating of your Oil.
Mains pressure just puts oil into the bearings and provides little bearing cooling as there should be minimal heat transfer due to windage in this situation.


2014 Nissan Rogue S CVT, OC#9 41392mi-QSUD10W30 + M110A CHAMP Filter; 2017 Subaru Crosstrek CVT OC#2 ?? mi-SOA/Idemitsu 0w20 + SOA Filter
Re: BMW S54 Rod Bearing Oil Pressures [Re: BrocLuno] #4580143
11/20/17 03:37 PM
11/20/17 03:37 PM
Joined: Dec 2002
Posts: 40,845
'Stralia
Shannow Online content
Shannow  Online Content
Joined: Dec 2002
Posts: 40,845
'Stralia
Originally Posted By: BrocLuno
+1 smile

And, yes and no. Most USA V8's have somewhat similar bearing sizes, so it has become a rule of thumb for USA engines. But all bets are off on bearings with other sizes and different clearances...

I'd just run a good high HTHS oil in the appropriate grade and keep it clean. If you want to do track days, think about loosening the clearances by a few thou and be done with it laugh


Reinforcing this...tTry to find an oil that has a high HTHS for it's grade, and drop back on Kinematic viscosity a little.

For example I'd use
https://www.redlineoil.com/Content/files/tech/15W50_MO_PROD_INFO.pdf

over either
https://www.mobil.com/english-gb/passenger-vehicle-lube/pds/glxxmobil-1-extended-life-10w60
https://msdspds.castrol.com/bpglis/FusionPDS.nsf/Files/B97CA7A6D4E6B82580257F8E006DA735/$File/BPXE-A9VFNF.pdf

As you get the same protection (HTHS) with about 15% lower KV, which means less pressure loss along the oil galleries and the feed port through the main to big end transfer port...a little bit, but in the right direction.

Also, being highly additised, when the oil film IS in distress, there's additives to help out.

Re: BMW S54 Rod Bearing Oil Pressures [Re: SlipperySimon] #4580184
11/20/17 04:31 PM
11/20/17 04:31 PM
Joined: Apr 2016
Posts: 1,530
Oregon
1JZ_E46 Offline
1JZ_E46  Offline
Joined: Apr 2016
Posts: 1,530
Oregon
I was told by someone with lots of knowledge on the S54 (has a 900 horsepower one in his race car - big turbo, nitrous) that the rod bearing issues are due to low-RPM, daily driving. S54 bearings seem to live long lives at the track in high-RPM high-oil pressure use. FWIW, he has stock bearings in his car with no issues.


2007 X5 4.8i: M1 HM 10W-30
2016 Countryman S: EDGE 0W-30
Re: BMW S54 Rod Bearing Oil Pressures [Re: SlipperySimon] #4580245
11/20/17 05:46 PM
11/20/17 05:46 PM
Joined: Dec 2011
Posts: 4,738
North Carolina
rooflessVW Offline
rooflessVW  Offline
Joined: Dec 2011
Posts: 4,738
North Carolina
The rod bearing "issues" in the S54 and S85 are, in my opinion, due to people driving with their foot to the floor while the engine is cold. If the people that daily drove and short tripped them did so with 0W-40 in the sump, they'd probably be fine.


"Zed's dead baby, Zed's dead."
Re: BMW S54 Rod Bearing Oil Pressures [Re: rooflessVW] #4581318
11/21/17 08:04 PM
11/21/17 08:04 PM
Joined: Dec 2009
Posts: 25,355
Regina, Saskatchewan, Canada
Garak Offline
Garak  Offline
Joined: Dec 2009
Posts: 25,355
Regina, Saskatchewan, Canada
You mean people buy a car like this and don't drive it as more than a grocery getter? wink Yes, I understand the irony, given that my G37 rarely sees above 60 mph.


Plain, simple Garak.

2008 Infiniti G37 - Shell ROTELLA T6 Multi-Vehicle 5w-30, NAPA Gold 7356
1984 F-150 4.9L - Quaker State GB 10w-30, Wix 51515
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