Scary rod bearing thread s85

[BMRLVR]

Originally Posted by Gearhead999s

Interesting read here about bearings in Nascar V8's that run to 9600 rpm and produce 900 bhp.They are running tighter clearances now than they used to.

http://www.precisionenginetech.com/t...g-tech-part-1/

The article covered many NASCAR related product advancements that Mahle-Clevite made to their bearings as a result of R&D & FEA performed on bearings used in NASCAR race engines

They did say that their may be some power to be gained by tightening up clearances but realize that NASCAR engines don't have to last for hundreds of thousands of miles in the real world while being subjected to cold starts, stop and go traffic, constant heat cycling, RPM changes etc. A NASCAR engine is built to last no more than 1000 miles and is optimized for the operating conditions it is to be subjected to.

The article closed by stating the age old number that engine builders quote for oil clearance settings 0.001" clearance per inch of journal diameter + 0.0005" for high performance applications. It goes on to state that you can tighten up clearance from there based on your own experience/application. My own personal preference for an engine that is to be used as a high performance/street engine that has to last a while is as such:

Mains: 0.001" per inch of journal diameter + 0.0002"

Rods: 0.001" per inch of journal diameter + 0.0005"

To those interested here is the important part (IMO) of the artice cut and pasted:

GENERAL CLEARANCE RECOMMENDATIONS
Start with 0.0010″ of clearance per inch of journal diameter. For example: 2.100″ journal diameter X 0.0010 = 0.0021″ clearance. For high-performance applications, add 0.0005″. If, for example, initial clearance is determined to be 0.0021″, add 0.0005″ for a final clearance of 0.0026″. From this point, tighten clearance as your experience dictates in specific applications.

Note: Use of a dial bore gauge is always the recommended method for measuring oil clearance. Instead of measuring journal diameter and then measuring installed bearing diameter, zero the bore gauge at the actual journal diameter. When you measure bearing diameter, you’ll obtain a direct clearance reading without the need to perform math procedures, avoiding potential math mistakes.

Havel emphasizes that if clearance modification is needed, do not increase or decrease clearance by modifying housing size outside of tolerance limits. An undersized housing will over-crush the bearing and an oversized housing will reduce crush and bearing retention.

Currently, Clevite utilizes finite element analysis computer modeling to examine the elastic deflections of all bearing-related areas. EHL, or elasto-hydrodynamic lubrication, allows engineers to more accurately determine the affects of dynamic forces in relation to forces and oil clearances. This understanding of loads, metal deflection and affects on clearance has allowed a more precise view of what the bearings are subjected to, and furthers engineers’ ability to develop bearings that will function properly in high-stress dynamic racing applications.

Originally Posted by Transfer

Multi grade oil gets thicker (higher SAE viscosity) as you reach full operating temp, not thinner.

Not the case, A Multigrade Oil has VII improvers added to it to change the viscosity index of the base oil and modify the rate at which it's viscosity changes with temperature change. For example, a 5W30 multigrade oil must meet the minimum cranking viscosity @ -30 C and minimum pumping viscosity @-35 C of a SAE 5W. This same oil is also required to fall within the viscosity range of an SAE 30 oil @ + 100 C and also meet the minimum HTHS rating at 150 C to be considered a 30.

Please follow the link to view specs engine oils are required to meet according to the SAE J300 test to recieve their respective grade assignment:

http://www.tribology-abc.com/abc/viscosity.htm#SAE

Originally Posted by Longwong

Um no. Cold oil is thicker than hot oil. The first number is the viscosity rating when cold and the second when it is hot. It does not get thicker. Hence the entire reason you need to warm up the oil and engine to get the oil flowing. Its common sense. take a bottle of oil and pour it at 0 degrees and than 100 degrees and tell me which oil is thinner or less viscous may be the proper term

Good post..... To go a little further than that, seperate a litre (quart for you Americans) of oil into three equal parts, put one in the freezer for an hour, Put one in the oven on the lowest setting for an hour, and leave one at room temperature......... I am willing to bet my house on the fact that the oil that was in the freezer will have the most resistance to pour, followed by the room temperature sample, and finally the oil that was in the oven will pour like a hot dam (pardon the pun).

*Just to correct myself from a few posts up...... I mistakenly quoted axial loads on the rod journals in many places, when in fact I should have been saying radial loads. Axial Loads are going to be controlled with the thrust washer and radial loads are taken by the oil film between the journal and the bearings! I was doing the job of the parts guy here at work yesterday and when I typed up the reply I was serving customers and adding to my post over the span of a few hours. I realized my mistake while reading my post this morning and I immediately corrected it......... Quite a foolish mistake when trying to get a serious point across.

[kawasaki00]

Originally Posted by Mike Benvo

I'm no engine building engineer - but to my understanding:

1: A smaller clearance will more evenly spread the load across the surface of the bearing, and will keep pressure across the bearing more consistent

2: A smaller clearance will decrease the amount of oil that is necessary to properly lubricate between the bearing and crankshaft

Now this is given that the oil viscosity is low enough to support the thinner clearance. If the oil is too think, then it's not going to lubricate properly.

3. Having tighter clearances reduces the amount of oil pressure needed to effectively lubricate those parts.

4: Tighter clearances can increase oil temperature and also increase bearing temperature.

5: On higher HP applications there might be a slight advantage to running slightly wider clearances to prevent distortion.

I will definitely defer to the engine experts on these points. Hope this helps somewhat.

Everything you speak of is true except number 5, tighter will decrease distortion but also increases chance of spinning a bearing.

[kawasaki00]

Originally Posted by BMRLVR

The article covered many NASCAR related product advancements that Mahle-Clevite made to their bearings as a result of R&D & FEA performed on bearings used in NASCAR race engines

They did say that their may be some power to be gained by tightening up clearances but realize that NASCAR engines don't have to last for hundreds of thousands of miles in the real world while being subjected to cold starts, stop and go traffic, constant heat cycling, RPM changes etc. A NASCAR engine is built to last no more than 1000 miles and is optimized for the operating conditions it is to be subjected to.

The article closed by stating the age old number that engine builders quote for oil clearance settings 0.001" clearance per inch of journal diameter + 0.0005" for high performance applications. It goes on to state that you can tighten up clearance from there based on your own experience/application. My own personal preference for an engine that is to be used as a high performance/street engine that has to last a while is as such:

Mains: 0.001" per inch of journal diameter on the + 0.0002" and

Rods: 0.001" per inch of journal diameter on the rods + 0.0005"

To those interested here is the important part (IMO) of the artice cut and pasted:

GENERAL CLEARANCE RECOMMENDATIONS
Start with 0.0010″ of clearance per inch of journal diameter. For example: 2.100″ journal diameter X 0.0010 = 0.0021″ clearance. For high-performance applications, add 0.0005″. If, for example, initial clearance is determined to be 0.0021″, add 0.0005″ for a final clearance of 0.0026″. From this point, tighten clearance as your experience dictates in specific applications.

Note: Use of a dial bore gauge is always the recommended method for measuring oil clearance. Instead of measuring journal diameter and then measuring installed bearing diameter, zero the bore gauge at the actual journal diameter. When you measure bearing diameter, you’ll obtain a direct clearance reading without the need to perform math procedures, avoiding potential math mistakes.

Havel emphasizes that if clearance modification is needed, do not increase or decrease clearance by modifying housing size outside of tolerance limits. An undersized housing will over-crush the bearing and an oversized housing will reduce crush and bearing retention.

Currently, Clevite utilizes finite element analysis computer modeling to examine the elastic deflections of all bearing-related areas. EHL, or elasto-hydrodynamic lubrication, allows engineers to more accurately determine the affects of dynamic forces in relation to forces and oil clearances. This understanding of loads, metal deflection and affects on clearance has allowed a more precise view of what the bearings are subjected to, and furthers engineers’ ability to develop bearings that will function properly in high-stress dynamic racing applications.

The engine builders including myself from our company had a large hand in writing that article. It is a good article and most every street car engine follows those guidelines.Everything they say is pretty much true. We do not follow those guidelines because the oil is heated every time the car is started. We run less than .001 per 1 inch but not as tight as what we are talking about here. .001 for 2.080 journal.

[Longwong]

Needless to say it does seem bmw chose really tight clearences for a street car to last 150k miles wouldn't you say?

With all of this great information, the question remains-what do we do? Practically speaking for us guys who cannot tear down the engine.

Running thinner oil sounds like an option but it also sounds there is plenty of downside, especially if you drive the car hard into high rpms.

to me from what I read, honestly the best advice I could take from this is from break-in and beyond you really benefit buy driving the crap out of the car and keeping revs high and engine oil as warm as possible to keep lubrication at its most. My car at 51k was hammered for 50k miles and runs like new.

Any other practical advice we can do given we know this information now?

[HeartMD]

Damn all this talk about engines blowing up is making me way to paranoid. For the last couple of days Ive been constantly thinking about my engine giving and avoiding reving it about 7.5k. Its taken alot of enjoyment away from the driving experience. Basically we are driving on borrowed time so to speak.

[s65e90]

Originally Posted by HeartMD

Damn all this talk about engines blowing up is making me way to paranoid. For the last couple of days Ive been constantly thinking about my engine giving and avoiding reving it about 7.5k. Its taken alot of enjoyment away from the driving experience. Basically we are driving on borrowed time so to speak.

No you're not. You are simply buying into the hype of a very small issue.

[e92zero]

I have a couple genuine questions for the experts here. Don't laugh if i sound stupid or way out.

1.) wouldn't the bearing naturally 'wears' to the right clearance? or bearings has a 'factory' coating outer layers on them to start with?
2.) since no one seem to make any undersized bearings, can't we take the worn but not too badly worn bearings and coat them to obtain the right thickness we need?

[regular guy]

I've see a lot of theories to explain why some of these engines fail and others don't. Let me add my own theory to the list, which I believe is mostly supported by the evidence I've seen. Along the way, I'll try to explain why I don't think people should fear like their engine is a ticking time bomb.

If we only consider stock engines and ignore highly modified engines (such as supercharged engines), then you'll notice most of them have failed very early in life. Most of the ones I've seen listed, and the one local engine I inspected with main bearing failure, all had these failures very early in life. They usually failed within the first 20,000 - 25,000 miles. I believe the root causes are found in the small anomalies that can happen during the manufacturing process. So to understand this a little better, let's look at some of those anomalies.

1. Crank/rod journals machined a little too big, but still within proper spec. Though we don't know the exact spec tolerance, we think the tolerance for the journal is about +/- 0.00025 inch.
2. Connecting rod big end machined a little too small, but still within proper spec. Again, the tolerance of the connecting rod big-end is probably about +/- 0.00025 inch.
3. Bearing size too small, but still within proper spec. According to Kawasaki00, this spec for Mahle-Clevite bearings is +/- 0.0003 inch.
4. Machine error while boring the main caps. This error is mentioned in the Mahle-Clevite white paper as machine alignment error. In the industry, this process is commonly referred to as "align boring" the main caps. All of the main caps are fully assembled and torqued (in this case, the engine bed plate), then the boring tool simultaneously machines the bore diameter of all of the main caps to the same exact specification. Even a fraction of a degree tilt error in the boring tool or engine jig will cause excessive pressure on one or more of the main bearings once the engine is assembled and running.

It is my belief that most engines are machined quite well and don't have any of these manufacturing anomalies listed above, and your engine will live a long and happy life. If your engine has only one of these issues (except #4), then your engine will probably not have any issues until later in life. You only need to worry if you have any two of these issues in combination, or issue #4. If your engine has any two of these issues in combination, or issue #4, then your engine will probably fail within the first 50,000 miles of operation. That's well within warranty and you will get a replacement motor, and so no need to panic and worry about sitting on a ticking time bomb. The evidence is purely circumstantial, but it does seem to fit the theory. The engines that do fail, all seem to fail very early in life. BTW, issue #4 is probably a death sentence for the engine. I have seen one of these S65 failures with this problem. The owner took his car to the dealership with an engine failure; BMW disassembled the engine; and told him the crank caps were out of alignment, and that caused his engine failure. So this can actually happen.

You'll notice that running an engine with any two of these anomalies in combination is the same thing as running these coated bearings without adding extra clearance. Any two of these in combination will reduce your clearance by 25-50% -- which is the same as adding coated bearings without extra clearance.

Unfortunately you can't add extra clearance without removing your crank; and you can't remove your crank without completely disassembling your engine. Technically you probably could remove the crank, but you would need to disassemble the engine to put it back and seal the bed plate. In the meantime, just be wise and prudent during cold starts and have your oil analyzed regularly.

I hope this helps.

[aussiem3]

According to BMW documentation - "Engine block with bedplate construction"
it says ... "The lower crankcase (bedplate) is also constructed using die-cast aluminium. Due to the extreme forces, grey cast iron inlays are used to reinforce the bedplate construction. These also limit crankshaft bearing clearances over a greater temperature range and thus have a positive effect on the oil flow rate.

These inlays they are talking about, do they contribute to this bearing issue at all?

[BMRLVR]

Originally Posted by kawasaki00

The engine builders including myself from our company had a large hand in writing that article. It is a good article and most every street car engine follows those guidelines.Everything they say is pretty much true. We do not follow those guidelines because the oil is heated every time the car is started. We run less than .001 per 1 inch but not as tight as what we are talking about here. .001 for 2.080 journal.

What kind of engines are you running?

Originally Posted by e92zero

I have a couple genuine questions for the experts here. Don't laugh if i sound stupid or way out.

1.) wouldn't the bearing naturally 'wears' to the right clearance? or bearings has a 'factory' coating outer layers on them to start with?
2.) since no one seem to make any undersized bearings, can't we take the worn but not too badly worn bearings and coat them to obtain the right thickness we need?

1) A bearing will wear the top layer of lead/tin off and make it's own clearance if it is marginally tight.

2) No it would not be advisable to coat worn bearings!

Originally Posted by regular guy

I've see a lot of theories to explain why some of these engines fail and others don't. Let me add my own theory to the list, which I believe is mostly supported by the evidence I've seen. Along the way, I'll try to explain why I don't think people should fear like their engine is a ticking time bomb.

If we only consider stock engines and ignore highly modified engines (such as supercharged engines), then you'll notice most of them have failed very early in life. Most of the ones I've seen listed, and the one local engine I inspected with main bearing failure, all had these failures very early in life. They usually failed within the first 20,000 - 25,000 miles. I believe the root causes are found in the small anomalies that can happen during the manufacturing process. So to understand this a little better, let's look at some of those anomalies.

1. Crank/rod journals machined a little too big, but still within proper spec. Though we don't know the exact spec tolerance, we think the tolerance for the journal is about +/- 0.00025 inch.
2. Connecting rod big end machined a little too small, but still within proper spec. Again, the tolerance of the connecting rod big-end is probably about +/- 0.00025 inch.
3. Bearing size too small, but still within proper spec. According to Kawasaki00, this spec for Mahle-Clevite bearings is +/- 0.0003 inch.
4. Machine error while boring the main caps. This error is mentioned in the Mahle-Clevite white paper as machine alignment error. In the industry, this process is commonly referred to as "align boring" the main caps. All of the main caps are fully assembled and torqued (in this case, the engine bed plate), then the boring tool simultaneously machines the bore diameter of all of the main caps to the same exact specification. Even a fraction of a degree tilt error in the boring tool or engine jig will cause excessive pressure on one or more of the main bearings once the engine is assembled and running.

It is my belief that most engines are machined quite well and don't have any of these manufacturing anomalies listed above, and your engine will live a long and happy life. If your engine has only one of these issues (except #4), then your engine will probably not have any issues until later in life. You only need to worry if you have any two of these issues in combination, or issue #4. If your engine has any two of these issues in combination, or issue #4, then your engine will probably fail within the first 50,000 miles of operation. That's well within warranty and you will get a replacement motor, and so no need to panic and worry about sitting on a ticking time bomb. The evidence is purely circumstantial, but it does seem to fit the theory. The engines that do fail, all seem to fail very early in life. BTW, issue #4 is probably a death sentence for the engine. I have seen one of these S65 failures with this problem. The owner took his car to the dealership with an engine failure; BMW disassembled the engine; and told him the crank caps were out of alignment, and that caused his engine failure. So this can actually happen.

You'll notice that running an engine with any two of these anomalies in combination is the same thing as running these coated bearings without adding extra clearance. Any two of these in combination will reduce your clearance by 25-50% -- which is the same as adding coated bearings without extra clearance.

Unfortunately you can't add extra clearance without removing your crank; and you can't remove your crank without completely disassembling your engine. Technically you probably could remove the crank, but you would need to disassemble the engine to put it back and seal the bed plate. In the meantime, just be wise and prudent during cold starts and have your oil analyzed regularly.

I hope this helps.

All good points, as for the part I bolded, I gave the same opinion in another thread some time ago stating that if the engine does not fail early in life it will most likely be OK.

When running clearances of 0.001" there is definitely no room for production variances what so ever and that is the main thing that scares me about the factory bearing clearances on the S65.......... You may get one that is perfectly within spec and will last forever, or, You may get one that there is a journal or bearing cap that is out a quarter to a half a thou and now you have an engine that has 25-50% less oil clearance, the engine, as a result of this could be a ticking time bomb!

Originally Posted by aussiem3

According to BMW documentation - "Engine block with bedplate construction"
it says ... "The lower crankcase (bedplate) is also constructed using die-cast aluminium. Due to the extreme forces, grey cast iron inlays are used to reinforce the bedplate construction. These also limit crankshaft bearing clearances over a greater temperature range and thus have a positive effect on the oil flow rate.

These inlays they are talking about, do they contribute to this bearing issue at all?

I don't think they are causing the issue, they were put in there to keep the rate of expansion of the bearing bores in check and in line with the crank journals' rate of expansion.

[kawasaki00]

Originally Posted by BMRLVR

What kind of engines are you running?

Sprint Cup Nascar Engines

[///M Power-Belgium]

Originally Posted by Mike Benvo

My pleasure. We recognize the importance of keeping RPM's low when the engine is cold. We believe that the factory 6,500 RPM limit on cold start is way too aggressive and could induce premature wear or damage on engine internals.

So for that reason we suggest the cold start rev limit reduction to those that use our performance software.

Better safe than sorry!

100 % agreed Mike !

[s65e90]

funny that only the bedplate is mentioned now.

Early on there were failures that I think were related to the bedplate misaligngmnet allowing bearings to spin (think 4g63 and something like crankwalk allowing lateral movement and in turn wiping out bearings)

[VCMpower]

Thank you for easing the stress of so many, as some folks will not even rev over 7k now for worry.

Originally Posted by regular guy

I've see a lot of theories to explain why some of these engines fail and others don't. Let me add my own theory to the list, which I believe is mostly supported by the evidence I've seen. Along the way, I'll try to explain why I don't think people should fear like their engine is a ticking time bomb.

If we only consider stock engines and ignore highly modified engines (such as supercharged engines), then you'll notice most of them have failed very early in life. Most of the ones I've seen listed, and the one local engine I inspected with main bearing failure, all had these failures very early in life. They usually failed within the first 20,000 - 25,000 miles. I believe the root causes are found in the small anomalies that can happen during the manufacturing process. So to understand this a little better, let's look at some of those anomalies.

1. Crank/rod journals machined a little too big, but still within proper spec. Though we don't know the exact spec tolerance, we think the tolerance for the journal is about +/- 0.00025 inch.
2. Connecting rod big end machined a little too small, but still within proper spec. Again, the tolerance of the connecting rod big-end is probably about +/- 0.00025 inch.
3. Bearing size too small, but still within proper spec. According to Kawasaki00, this spec for Mahle-Clevite bearings is +/- 0.0003 inch.
4. Machine error while boring the main caps. This error is mentioned in the Mahle-Clevite white paper as machine alignment error. In the industry, this process is commonly referred to as "align boring" the main caps. All of the main caps are fully assembled and torqued (in this case, the engine bed plate), then the boring tool simultaneously machines the bore diameter of all of the main caps to the same exact specification. Even a fraction of a degree tilt error in the boring tool or engine jig will cause excessive pressure on one or more of the main bearings once the engine is assembled and running.

It is my belief that most engines are machined quite well and don't have any of these manufacturing anomalies listed above, and your engine will live a long and happy life. If your engine has only one of these issues (except #4), then your engine will probably not have any issues until later in life. You only need to worry if you have any two of these issues in combination, or issue #4. If your engine has any two of these issues in combination, or issue #4, then your engine will probably fail within the first 50,000 miles of operation. That's well within warranty and you will get a replacement motor, and so no need to panic and worry about sitting on a ticking time bomb. The evidence is purely circumstantial, but it does seem to fit the theory. The engines that do fail, all seem to fail very early in life. BTW, issue #4 is probably a death sentence for the engine. I have seen one of these S65 failures with this problem. The owner took his car to the dealership with an engine failure; BMW disassembled the engine; and told him the crank caps were out of alignment, and that caused his engine failure. So this can actually happen.

You'll notice that running an engine with any two of these anomalies in combination is the same thing as running these coated bearings without adding extra clearance. Any two of these in combination will reduce your clearance by 25-50% -- which is the same as adding coated bearings without extra clearance.

Unfortunately you can't add extra clearance without removing your crank; and you can't remove your crank without completely disassembling your engine. Technically you probably could remove the crank, but you would need to disassemble the engine to put it back and seal the bed plate. In the meantime, just be wise and prudent during cold starts and have your oil analyzed regularly.

I hope this helps.

[VCMpower]

If your bearings are worn through the tin/alloy coating and copper is showing, it is replacement time. Ideally this will not happen.

Originally Posted by e92zero

I have a couple genuine questions for the experts here. Don't laugh if i sound stupid or way out.

1.) wouldn't the bearing naturally 'wears' to the right clearance? or bearings has a 'factory' coating outer layers on them to start with?
2.) since no one seem to make any undersized bearings, can't we take the worn but not too badly worn bearings and coat them to obtain the right thickness we need?

[BMRLVR]

Here is a bearing failure analysis guide...... Unfortunately the photos are not in colour

http://www.wilmink.nl/Clevite/Clevit..._tech_info.pdf

[BPMSport]

^^ This is great info. Thanks!

[mdosu]

very good info here. Thanks guys, I'll have my oil analyzed at every oil change going forward.

[BMRLVR]

Originally Posted by kawasaki00

Sprint Cup Nascar Engines

Awesome...... Good to have an engine builder from a professional racing series chime in here! Also nice to see that you too agree with the S65 oil clearances being too tight.

[aussiem3]

Originally Posted by BMRLVR

Awesome...... Good to have an engine builder from a professional racing series chime in here! Also nice to see that you too agree with the S65 oil clearances being too tight.

Surely during the early life of the S85 is bearing issue would have come to the fore and also at some point in time during the extensive engine testing BMW undertakes before production. Given all this I am surprised the S65 ended up having the same issue. May be, BMW thought given the percentage of the engines that suffer this failure it was not worth changing the design probably given the cost factor.

It's just like someone's body, and you look all well in outside appearance, and one fine day you visit the doctor and you're diagnosed with terminal cancer and you have three months to live. This sucks.

[L4ces]

I hope BMW reads these forums. I wonder how could the ignore us? HELLO, you out there?

[GIdriver]

Originally Posted by aussiem3

Surely during the early life of the S85 is bearing issue would have come to the fore and also at some point in time during the extensive engine testing BMW undertakes before production. Given all this I am surprised the S65 ended up having the same issue. May be, BMW thought given the percentage of the engines that suffer this failure it was not worth changing the design probably given the cost factor.

It's just like someone's body, and you look all well in outside appearance, and one fine day you visit the doctor and you're diagnosed with terminal cancer and you have three months to live. This sucks.

...so now we have to start "screening" our cars for cancer by analyzing the engine's oil, unless you want to be more aggressive and do an "exploratory surgery" and open the engine...