Official S65 Bearing Specification/Clearance Wiki

[kawasaki00]

Originally Posted by swamp2

Surely you can follow the irony here...

Bearing wear is observed, a known cause of bearing wear is put forth of clearances being too tight. Some measurements support clearances tighter than one manufacturers rules of thumb and "50 years of best practices" (of course BMW has consistently violated such best practices for decades...). Of course the written rule of thumb is not provided by the actual manufacturer of theses particular bearings in this engine but from a competitor. Once there were any measurements supporting the tight clearance hypothesis it was basically "game over" and "we have a full blown and validated theory". And to many we had iron clad verification that BMW screwed up big time. Now another bearing series (revised part numbers, harder, but unknown as to a nominal size change by design), likely implemented for lead free requirements, is measured using an entire set of new bearings. The clearances come in right about at/inside the minimum Clevite specification (again who don't make any of the 8XX or 7XX series bearings in question here). It is also brought to light that we don't have a series of measurements for the older 8XX bearings done in an apples to apples fashion as what was performed on the newer bearings.

Now, here is the real kicker, you offer us the brazen assurance that DESPITE what the clearance values are measured at, bearing clearance is still guaranteed to be the problem (of course perhaps compounded by an oil that is too viscous). It obviously begs the question, purely hypothetically, what if the 8XX series bearings were to come up at the upper (larger) end of the Clevite recommended clearance? The entire cause and effect would evaporate yet you'd still be "lecturing" us that despite the actual physical measurements you are 100% confident what the problem is.

I'm not saying the bearing series are identical in size and resulting clearance. I'm not saying BMW didn't perhaps revise clearances. I'm not saying that they may have halted a premature wear problem in engines fit with the new series bearing. Lucky for all of us you can help answer these questions. However, when you are so brash as to simply discard basic measurements and cause and effect, your credibility suffers.

I understand your point, when we got together as a group at our shop without even saying what the clearances were the question was asked what is everyones opinion of these bearings. We all agreed that they are too tight. When they have that scuff just off axis there is either no oil pressure and or it is too tight.
So when I say I dont need to know wha the spec is, it is because years of experience have shown when they look like that, whatever the clearance is it needs more.
If the factory spec was .0021 and they still looked like that then I would say they need to be .0025. The number is not so much important if the bearings look good. Within reason of course.
There is a rule of thumb that is tought when starting in this profession.
It will run with it but not without it. Meaning a little extra clearance will be just fine, too tight and it will look just like every bearing on here.

[regular guy]

Originally Posted by swamp2

I don't think anyone has come anywhere close to saying or holding such an extreme belief. I certainly do not myself either. Many here have surely defended BMW saying such a gross error on the level being promulgated just doesn't make sense.

There is one person here who HAS taken this view. Now he's silent. Hmmm.

On a related note it does seem that we need some true apples to apples measurements of the 8XX bearings. Just like the 7XX ones were done. Same operator, same tools, same rods, new bearings, same temperatures, etc. Just the normal stuff one needs to make apples to apples comparisons.

Originally Posted by swamp2

I floated the (creative IMHO) idea long ago in the thread that the community chip in to fund this investigation. I heard a deafening silence from my fellow forum members. My offer is absolutely on the table to help out. Now I certainly am not going to single handedly fund your trip out here to CA but it would be nice to see some community support for this important effort.

Here's what it takes to do this. I think I've done my part, spent many hundred dollars already and probably 200 hours of my time as well. But I'm still willing to do more if others will buy in.

It only costs time and money. I'll buy one set, if I can get donations for the other. PM if interested.
Full set of virgin 088/089's (if you can still get them as discontinued): $375
Full set of 702/703's: $375
Two more sets of connecting rod bots: $230

Then to take this to the next level, after taking the measurements on virgin parts, a half set of each would be sent to Calico and WPC for coating/treatment. Then repeat the process when the parts return. Add another $300 in these expenses.

[kawasaki00]

Originally Posted by SenorFunkyPants

OK a couple of things....why would wear at the parting line point to oil starvation? As this is the point of highest clearance shouldn't this show the lowest wear - while the 6 and 12 o'clock positions with the smallest clearance show the highest? plus I thought parting line wear was usually accounted for by excess crush causing distortion?
And for the sake of argument lets say that the clearances are too tight, wouldn't a thinner oil be more likely to be squeezed out during high load on the bearings causing even more wear?
Apologies for so many questions.

Twice during the cycle the parting line sees stress, halfway down the bore and halfway back up. With oil pressure it will keep that journal centered in the bearing bore. When there is no oil pressure upon startup the journal beats that area hard because there is naturally more clearance. Althoug very small the journal gets a running start before it bangs into the parting line because there is naturally more clearance. Kind of like banging a sharpie pin around in a soup can and then something just slightly smaller than the can. The tighter it is to the can the less velocity it builds.
Kind of hard to explain so work with me if you have specific questions.
This engine does not have near the cylinder pressure as say a 335 boosted up. I honestly dont think it is a problem of the oil being squeezed out I think it is that is cant stay full of oil when cold and is partially running dry.
The way that oil flow is figured on a engineering side is that there should be sufficient flow that each rotation of the crank should displace one rod worth of oil. Meaning the total amount of oil that is inside the bearing should be flushed out and replaced with all new oil for each crank rotation.
That is a entire different discussion but just trying to get the info out there.

[catpat8000]

Originally Posted by swamp2

I floated the (creative IMHO) idea long ago in the thread that the community chip in to fund this investigation. I heard a deafening silence from my fellow forum members. My offer is absolutely on the table to help out. Now I certainly am not going to single handedly fund your trip out here to CA but it would be nice to see some community support for this important effort.

I would also volunteer to help out provided we agree ahead of time on what the exercise intends to accomplish.

edit: just saw regular_guys's post above. I'm not an engine builder and the subtleties of this effort are sometimes beyond me. Perhaps I'm not that smart either Anyway, if someone would write up the experiment/test we want to perform, and if they would identify the hypothesis we are testing and how we will test it, and if I understand that, I'll be happy to contribute $$.

Mark me down,
Pat

[SenorFunkyPants]

Originally Posted by regular guy

I'd say the biggest surprise here is for those guys who came here and claimed that BMW was infallible, smartest guys on the planet, obviously chose the bearing clearance for a reason and we're just too dumb to know what it is. And as their proof, they said BMW didn't change the bearing clearance when updating to 702/703 bearings. I wonder where they stand now?
And
There is one person here who HAS taken this view. Now he's silent. Hmmm.

Sorry are you having a poke at me or snow? Its hard to tell.

In any case:

Originally Posted by Yellow Snow

Let's be honest, if there was actually a bearing clearance problem, BMW could instruct Clevite to make the bearings a few microns thinner in 5 minutes.

was followed by

Originally Posted by regular guy

If we're being TOTALLY honest, then you already know BMW would get an instant class action lawsuit if they did what you suggest without issuing a recall on the people who didn't get the updated bearings. We already discussed this, so you should already know this.

So any further discussion that followed on this issue was based on your assertion that the bearings were the same thickness.

[L4ces]

Originally Posted by biglare

Here is the true answer!

Lol. Stupid funny!

[Yellow Snow]

Originally Posted by SenorFunkyPants

OK a couple of things....why would wear at the parting line point to oil starvation? As this is the point of highest clearance shouldn't this show the lowest wear - while the 6 and 12 o'clock positions with the smallest clearance show the highest? plus I thought parting line wear was usually accounted for by excess crush causing distortion?
And for the sake of argument lets say that the clearances are too tight, wouldn't a thinner oil be more likely to be squeezed out during high load on the bearings causing even more wear?
Apologies for so many questions.

Wasn't that the Carillo rod that had the parting line wear? I thought the OP said it was due to rod stretch distorting the bore on his supercharged motor.

[SenorFunkyPants]

Originally Posted by kawasaki00

Twice during the cycle the parting line sees stress, halfway down the bore and halfway back up. With oil pressure it will keep that journal centered in the bearing bore. When there is no oil pressure upon startup the journal beats that area hard because there is naturally more clearance. Althoug very small the journal gets a running start before it bangs into the parting line because there is naturally more clearance. Kind of like banging a sharpie pin around in a soup can and then something just slightly smaller than the can. The tighter it is to the can the less velocity it builds.

Thanks for that and I can see how that might work. The problem I have is that wear due to oil starvation at start up shouldn't be restricted to just the parting lines. If there is the possibility of metal to metal contact then that possibility surely applies to all contact areas - at the very least you would expect some scuff marks on the bottom bearing shell. The only medium wear bearing set that shows bottom bearing scuffing is RGs stroker motor.

This is a rod bearing set from a 105,000km S85 engine:



And apart from whatever malfunction is going on in cylinder 3 and 8, the bottom bearings are pristine. That after 1000s of cold starts.
A while ago I asked the Clevite guy if you could have unworn lower bearings in a tight bearing engine with this sort of mileage and his reply was that a motor with tight bearings wouldn't make even 50,000 miles.

[SenorFunkyPants]

Originally Posted by Yellow Snow

Wasn't that the Carillo rod that had the parting line wear? I thought the OP said it was due to rod stretch distorting the bore on his supercharged motor.

Yes...in this case though I was going from Clevite:
"Excessive crush - Extreme wear areas visible along the bearing surface adjacent to one or both of the parting line."

[swamp2]

Let me offer the following correction.

Originally Posted by kawasaki00

Twice during the cycle the parting line sees stress, halfway down the bore and halfway back up.

The side load perpendicular to the primary connecting rod axis as seen at the big bearing end of the rod varies roughly sinusoidally with a period of 360 degrees of crank rotation (720 degrees being a complete combustion cycle). Thus it always sees stress except precisely at TDC and BDC. The two peak side loads (and thus peak compressive stresses) occur roughly at the point when the piston is halfway through its total stroke.

This was all covered in the "terrible" M.S. Thesis I posted some time back...

And back the the question

Originally Posted by SenorFunkyPants

why would wear at the parting line point to oil starvation? As this is the point of highest clearance shouldn't this show the lowest wear - while the 6 and 12 o'clock positions with the smallest clearance show the highest? plus I thought parting line wear was usually accounted for by excess crush causing distortion?

Peak loads don't happen where they do based on clearances (unless something is really out of whack). The location of the parting line is very rarely a location of any significant load or stress. Loads are typically dominated by combustion pressure at low rpm and by inertial loads at high rpm those both typically occur at or near TDC. Bearing wear on the top bearing indicates that the combustion load is the contributing factor, not high rpm inertial loading when the piston "tries" to keep shooting up at the end of the exhaust stroke. Thus I believe low rpm starvation is consistent with this particular observed asymmetric bearing wear.

I'm not sure about excess crush but that sounds completely plausible to me.

[swamp2]

Originally Posted by regular guy

Here's what it takes to do this. I think I've done my part, spent many hundred dollars already and probably 200 hours of my time as well. But I'm still willing to do more if others will buy in.

It only costs time and money. I'll buy one set, if I can get donations for the other. PM if interested.
Full set of virgin 088/089's (if you can still get them as discontinued): $375
Full set of 702/703's: $375
Two more sets of connecting rod bots: $230

Then to take this to the next level, after taking the measurements on virgin parts, a half set of each would be sent to Calico and WPC for coating/treatment. Then repeat the process when the parts return. Add another $300 in these expenses.

Why another set of 7XX bearings?
Clearly a new set of 8XX bearings are needed. If they are available I am happy to chip in $100 toward those and the con rod bolts.

Come on folks, all of you who passionately want to know the answer here put your money where your mouth is and chip in, even $10-$20 would help and surely would give r.g. some additional motivation.

[Yellow Snow]

Originally Posted by swamp2

Let me offer the following correction.



The side load perpendicular to the primary connecting rod axis as seen at the big bearing end of the rod varies roughly sinusoidally with a period of 360 degrees of crank rotation (720 degrees being a complete combustion cycle). Thus it always sees stress except precisely at TDC and BDC. The two peak side loads (and thus peak compressive stresses) occur roughly at the point when the piston is halfway through its total stroke.

This was all covered in the "terrible" M.S. Thesis I posted some time back...

And back the the question



Peak loads don't happen where they do based on clearances (unless something is really out of whack). The location of the parting line is very rarely a location of any significant load or stress. Loads are typically dominated by combustion pressure at low rpm and by inertial loads at high rpm those both typically occur at or near TDC. Bearing wear on the top bearing indicates that the combustion load is the contributing factor, not high rpm inertial loading when the piston "tries" to keep shooting up at the end of the exhaust stroke. Thus I believe low rpm starvation is consistent with this particular observed asymmetric bearing wear.

I'm not sure about excess crush but that sounds completely plausible to me.

A couple more points:

Isn't the top bearing wear down to oil drain from top to bottom shell when parked. Then the initial cold start rotation marks the dry top shell.

Also, how could the parting line wear be down to the journal going off centre at cold start. Surely the lemon shape of the bore wouldn't allow the journal to touch the part line.

[SenorFunkyPants]

Re: the 088/9 bearing part numbers I assume that its 11247838088 & 9
Its not listed on Realoem as an M3 part but as a discontinued M5/6 part number.
Realoem doesn't show any change in rod bearing part number - it just lists the 11247841703/2 number from the start until the end of the S65 M3 production.
Maybe I've misunderstood something or Realoem is mistaken or incomplete....is there a visual difference between the two bearings that identifies them?
I'm good for a couple of $ if needed.

[jcolley]

I'll chip in for this. Who's taking the lead on organizing it?

[Gearhead999s]

Looks like GM has some rod bearing issues with some of their engines.

http://blog.caranddriver.com/maliboo...our-cylinders/

[kawasaki00]

Originally Posted by Gearhead999s

Looks like GM has some rod bearing issues with some of their engines.

http://blog.caranddriver.com/maliboo...our-cylinders/

You know we were just talking about that a couple days ago. GM along with other manufacturers have built millions of engines over how many years. All of a sudden they start kicking rods out. This is what happens when you keep tightening everything up, it is not just happeneing to BMW folks it is going on everywhere just on the down low. Just the same as all the bmws that are getting short blocks because the start stop is destroying the bottom ends.

[regular guy]

Originally Posted by swamp2

Why another set of 7XX bearings?
Clearly a new set of 8XX bearings are needed. If they are available I am happy to chip in $100 toward those and the con rod bolts.

Come on folks, all of you who passionately want to know the answer here put your money where your mouth is and chip in, even $10-$20 would help and surely would give r.g. some additional motivation.

These 70x bearings were on loan from Alekshop from his stroker build. As soon as those rods/bearings return, they are going into an engine.

[regular guy]

Originally Posted by SenorFunkyPants

Re: the 088/9 bearing part numbers I assume that its 11247838088 & 9
Its not listed on Realoem as an M3 part but as a discontinued M5/6 part number.
Realoem doesn't show any change in rod bearing part number - it just lists the 11247841703/2 number from the start until the end of the S65 M3 production.
Maybe I've misunderstood something or Realoem is mistaken or incomplete....is there a visual difference between the two bearings that identifies them?
I'm good for a couple of $ if needed.

Welcome to the thread. All of these topics have been discussed, rediscussed, and rediscussed. Photos have been included showing the differences. For convenience, this history and photos are discussed on Post #7. The removal of the old part numbers from realoem was discussed as well. In fact, we even discussed this when you and your buddy were busy pulling links from m3forum trying to trip me up and playing your little games.

Why this new (old) discovery now?

[regular guy]

Originally Posted by jcolley

I'll chip in for this. Who's taking the lead on organizing it?

Send me a PM for details.

[SenorFunkyPants]

Originally Posted by regular guy

Welcome to the thread. All of these topics have been discussed, rediscussed, and rediscussed. Photos have been included showing the differences. For convenience, this history and photos are discussed on Post #7. The removal of the old part numbers from realoem was discussed as well. In fact, we even discussed this when you and your buddy were busy pulling links from m3forum trying to trip me up and playing your little games.

Why this new (old) discovery now?

Wow a simple yes would have done.

[regular guy]

Originally Posted by SenorFunkyPants

Wow a simple yes would have done...where does all the small minded spite come from - it must really suck to be you.

Hey bud, you've played this antagonist game long enough. Instead of calling BS on every single dot and tiddle, maybe you should read the material you're calling BS on. Didn't I ask you to do that before? It was good advice then, and it's good advice now.

[regular guy]

Originally Posted by SenorFunkyPants

A while ago I asked the Clevite guy if you could have unworn lower bearings in a tight bearing engine with this sort of mileage and his reply was that a motor with tight bearings wouldn't make even 50,000 miles.

Interesting. Earlier you said that you had one and only one email with Clevite. You said you posted the entire response in this post. When did you contact Clevite a second time? And wouldn't this new Clevite response be consistent with all of the emperical evidence of tolerance stacking hypothesis presented in this thread?