Official S65 Bearing Specification/Clearance Wiki

[Sered]

Originally Posted by Yellow Snow

I have no factual figures from BMW, only diy measurements which don't account for tolerances.

If you have the actual BMW sizes and tolerances in documented form from BMW I would love to see them.

Without the facts, we can't get anywhere.

That's a cute Skeptic 101 book you picked up, but you're doing it wrong

You're out of your league here, why not just pipe down? Anyone who analyzes the evidence will know that something is up, period. Too many engine builders have shown independent data that checks out with one another. You ask for proof, well you have it; no one is going to print out every single piece of data for you to review. Your understanding of what 'proof' is, is flawed.

[regular guy]

Originally Posted by jcolley

Issue 73?

Yes, Issue 073. The reason I say the numbers are approximate is because the article gives specific bearing clearance but not journal size. Instead, they say the journal size matches the older TJ engine. So I scanned the photo at 1200 DPI and measured the piston size (which they do specify as 98mm) and calculated the rod journal diameter in relation to piston size. It's obviously approximate. The TJ engine is discussed in issue 033. I think I'll order issue 033 if they still sell it to get all the technical details of the TJ engine. Then we can have exact calculations. But even if I was off by 2mm on the rod journals, the journal clearance ratio ranges from 0.00350" to 0.00400" clearance per journal-inch diameter. That's still 5.5x - 6.3x the size of the S65 journal clearance ratio.

[Yellow Snow]

Originally Posted by regular guy

I'm sorry, but I'm intentionally not sharing the side clearance. These builds and tools cost a lot of money. I'm going to protect my investment to keeping it private. That's why I've only said things like "two human hairs" and "two orders of magnitude" when I describe it. I intend to keep it that way. But to put the shoe on the other foot, you tell me what's normal, then you tell me what you think is too small side clearance.

I thought the object of this excercise was to gather and share information. Why the secrecy? Is it actually you who is doing the measurements or are you quoting someone else?

Originally Posted by regular guy

You're measuring metal bearings outside of the rod and not torqued down to get your eccentricity measurements. That bearing is a spring, of course it's going to have more eccentricity when it's outside of the connecting rod bore. Yours is a completely invalid way to measure the eccentricity.

I think you understand exactly what I meant. At no stage did I say it was measured in a rod. I am well aware that it's a spring.

Measure the shell at 10mm from the parting line. The S65 is .0012" thinner there than at the 90 degrees point which is significantly more than the normal .0004" of regular shells.

This will effectively give a lot more eccentricity than a regular shell when installed in a rod no matter how you want to look at it.

If you are actually doing the measurements yourself, why can't you check it and report back

[jcolley]

Originally Posted by Yellow Snow

This will effectively give a lot more eccentricity than a regular shell when installed in a rod no matter how you want to look at it.

Not true if the radius of the rod is less at the parting line than at the 12 and 6 o'clock positions. By that I mean if the connecting rod has some ellipticality in the vertical plane as the reduction in shell thickness near the parting line, the end result could be a perfectly circular if the shell is deforming into the rod, no?

The area around the parting line on the rod may have been increased in thickness to account for the loss of material strength due to the fastener holes and the stress concentration points of the threads.

Pure supposition as I have no intention of pulling my engine out to measure it unless I see a damaged crank this weekend.

[Yellow Snow]

Originally Posted by jcolley

Not true if the radius of the rod is less at the parting line than at the 12 and 6 o'clock positions. By that I mean if the connecting rod has some ellipticality in the vertical plane as the reduction in shell thickness near the parting line, the end result could be a perfectly circular if the shell is deforming into the rod, no?

The area around the parting line on the rod may have been increased in thickness to account for the loss of material strength due to the fastener holes and the stress concentration points of the threads.

Pure supposition as I have no intention of pulling my engine out to measure it unless I see a damaged crank this weekend.

If you assemble and torque a rod together the bore should be perfectly round.

Fitting a bearing shell which tapers slightly to the part line gives the oval shape.

Measuring the shell at 10mm from the split ignores any crush distortion when fitted torqued into the rod.

If one type of bearing has a .0012" radial difference (.0024" total)at 10mm and the other has .0004" radial difference (.0008" total) it equates to more oil clearance.

It's a significant difference

[jcolley]

Originally Posted by Yellow Snow

If you assemble and torque a rod together the bore should be perfectly round.

"Should be" or "is"?

Is this from BMW engineering specification for the connecting rod or years of common practice? Have you measured a torqued rod assembly without a bearing in it to verify that?

It could have been purposely designed that the rod lower end itself was not intended to be perfectly circular and the assembly as a whole with a bearing in it was designed to be. That would have allowed for greater bearing thickness at the top and bottom shell centers and thicker rod cross section at the parting line, all while maintaining a circular specification when assembled as a whole. Maybe someone with a few rods laying around can check that theory without a bearing in it.

To assume any previously established "norms" were used by the same engineers who clearly deviated from previously established norms would be a poor assumption.

This practice is used in my line of work with rotating machines that exceed the RPM of the Cosworth mentioned above. It is impractical to attempt to manufacture a bearing casing that weighs multiple tons with perfect circularity to last for 30+ years. The bearings are then manufactured to specific dimensions to ensure that specific assembly as a whole has perfect circularity, but are not interchangeable with any other identical unit. While obviously not a direct correlation to automotive engine building, the engineering principle is the point. The assembly as a whole should be circular, although individual parts may not be.

[Yellow Snow]

Originally Posted by jcolley

"Should be" or "is"?

Is this from BMW engineering specification for the connecting rod or years of common practice? Have you measured a torqued rod assembly without a bearing in it to verify that?

It could have been purposely designed that the rod lower end itself was not intended to be perfectly circular and the assembly as a whole with a bearing in it was designed to be. That would have allowed for greater bearing thickness at the top and bottom shell centers and thicker rod cross section at the parting line, all while maintaining a circular specification when assembled as a whole. Maybe someone with a few rods laying around can check that theory without a bearing in it.

To assume any previously established "norms" were used by the same engineers who clearly deviated from previously established norms would be a poor assumption.

This practice is used in my line of work with rotating machines that exceed the RPM of the Cosworth mentioned above. It is impractical to attempt to manufacture a bearing casing that weighs multiple tons with perfect circularity to last for 30+ years. The bearings are then manufactured to specific dimensions to ensure that specific assembly as a whole has perfect circularity, but are not interchangeable with any other identical unit. While obviously not a direct correlation to automotive engine building, the engineering principle is the point. The assembly as a whole should be circular, although individual parts may not be.

Sorry I should have said 'is' round.

The rods are assembled and torqued as matching sets then machined and honed into a perfect circle.

[regular guy]

Originally Posted by Yellow Snow

I thought the object of this excercise was to gather and share information. Why the secrecy? Is it actually you who is doing the measurements or are you quoting someone else?

This is fully explained in the first page of this thread.

If you are actually doing the measurements yourself, why can't you check it and report back

This was explained a few posts up last time it was asked. The parts are not in my possession because I sold them, and I must arrange to take measurements with the new owner of the parts. We are both busy people and schedules don't always coincide. I was going to do it this weekend, but now I'm going out of town. I shouldn't have to explain any of this in the first place.

Originally Posted by Yellow Snow

Sorry I should have said 'is' round.

The rods are assembled and torqued as matching sets then machined and honed into a perfect circle.

Rods are honed to a perfect circle given the honing technology available.

[Yellow Snow]

Originally Posted by regular guy

Rods are honed to a perfect circle given the honing technology available.

I believe the BMW honing equipment is fairly good.

[510135]

This thread has turned me completely off the e90/92 M3. Coming from a somewhat troublesome n54 I was keen for a "reliable" performance platform.

I have learned a lot , thanks to all the posters!

[joe@ptech]

Great information. Thank you for posting.

[L4ces]

If I were in the market I'd be burdened with worries about the new M3/M4. I am certainly curious to hear what the bearing story is for that engine. It will be a long wait.

[PandaM3]

Originally Posted by 510135

This thread has turned me completely off the e90/92 M3. Coming from a somewhat troublesome n54 I was keen for a "reliable" performance platform.

I have learned a lot , thanks to all the posters!

I'm actually tempted to trade or sell my e90 m3 for a Lexus IS-F...

8 speed and V8 from the Lexus LS400... The confidence knowing that 200,000 miles is just breaking it in... And it has 90% of the performance of the M3

I need to go test drive one so I can decide... Replace rod bearings every 50,000 to 75,000 miles? Knowing that even with replacement (depending on the tech) there is still a chance of grenadine the engine soon after replacement... Or give up and get an IS-F

[HeartMD]

Originally Posted by PandaM3

I'm actually tempted to trade or sell my e90 m3 for a Lexus IS-F...

8 speed and V8 from the Lexus LS400... The confidence knowing that 200,000 miles is just breaking it in... And it has 90% of the performance of the M3

I need to go test drive one so I can decide... Replace rod bearings every 50,000 to 75,000 miles? Knowing that even with replacement (depending on the tech) there is still a chance of grenadine the engine soon after replacement... Or give up and get an IS-F

Not for nothing but after having followed this EXTREMELY informative thread since the begining, I truely have lost all my confidence with this car. I also agree that having to replace bearings as a possible temporary insurance policy is something that I wasnt expecting on a 75k car. I hate having to be on the constant look out for any weird/new sound or having to send in my engine oil for analysis. The thought that once the car is out of warranty and having a catastrophic engine failure with a 25k price tag is something I dont want to deal with. Looks like my dreams of longterm ownership of this car have been shattered.

[flint]

Originally Posted by HeartMD

Not for nothing but after having followed this EXTREMELY informative thread since the begining, I truely have lost all my confidence with this car. I also agree that having to replace bearings as a possible temporary insurance policy is something that I wasnt expecting on a 75k car. I hate having to be on the constant look out for any weird/new sound or having to send in my engine oil for analysis. The thought that once the car is out of warranty and having a catastrophic engine failure with a 25k price tag is something I dont want to deal with. Looks like my dreams of longterm ownership of this car have been shattered.

Starting to feel the same way...

[swamp2]

Originally Posted by regular guy

That would be fair if one of your former collegues, consultants, and confidants wasn't the former BMW-M engine designer who lead the effort to take the M10 to Formula One and was the principle designer of the S14. A guy who still consults with BMW until I last worked on a project with him two years ago. I was hoping we wouldn't have to go here in this thread...but it might be necessary.

But before you get too excited, no I haven't asked him about this issue. But I can give you enough of his design philosophy to show you the clearances he set on the engines he designed -- including the S14 (hopefully later tonight).

I assume his credentials will be unimpeachable on this topic.

Hmmm, selective expertise? BMW have completely screwed multiple generations and decades of engines with clearance ratios similar to the S65 or ones that violate the immutable "50 years of best practices" (or was it 80 years...) but now the BMW M engine designer you happen to know is unimpeachable. Give me a break.

Originally Posted by jcolley

I don't think any of the guys here stand to gain a thing by martyring the clearance issue.

Originally Posted by regular guy

I'm sorry, but I'm intentionally not sharing the side clearance. These builds and tools cost a lot of money. I'm going to protect my investment to keeping it private.

The credibility, complete lack of bias, only sharing data no conclusions, only doing this to share with the community, etc. lines are starting to rapidly evaporate here...

[swamp2]

Originally Posted by MFL

Nope, disregard facts, common sense and the pictures in this thread and many other threads. BMW is magic and omnipotent. Physics, thermal dynamics, math...Who cares, BMW made this so clearly they transcend common sense and modern science.

There has been very little discussion of physics, thermodynamics and math here.... Just a lot of rules of thumb and general principles and historical best practices.

[swamp2]

Originally Posted by regular guy

There are three things that you know for a fact:

1. There is a long standing clearance-to-journal ratio best practice rule that factory and racing engine builders alike have followed for 50+ years. This best practice clearance ratio is well documented in dozens of web sites, and recommended by Clevite, the maker of the S65 engine bearings. The S65 engine cuts that clearance ratio in half.
2. The bearing wear patterns we're seeing all match the Clevite online/interactive bearing failure diagnosis web site, example #12 "Oil Starvation / Marginal Oil Film Thickness." The main cause mentioned by Clevite for this type of failure is "too little bearing oil clearance."
3. There is also a long standing rod side clearance best practice rule that factory and racing engine builders alike have followed for quite some time. Best practice clearance ratio is well documented in dozens of web sites. The S65 engine cuts that clearance ratio by two orders of magnitude.

There are facts then there is interpretation.

What is the global failure rate due to bearing clearnance as a function of mileage for the S65?

Obviously all complex systems exhibit failures, period.

What is an acceptable failure rate of the S65 engine as a function of mileage?

Clevite is not the only acceptable source of expertise on this issue. As another member pointed out it is likely BMW and Clevite have some understanding of what BMW was trying to achieve with the clearances they specified and both parties are probably aware of the big picture, the benefits, the drawbacks and the answers to the initial questions I posed above. No one else does.

Originally Posted by regular guy

Wouldn't that depend on what base you have? You're using base-10, I was using base-2. But you're probably right and I'm probably wrong. But now you know what I really meant anyways. Thank you!

Switching to base 2 to define "2 orders of magnitude", come on give me a break, that is either a shameful lie or a shameful recovery. 2 orders of magnitude is equal to 100 (or at best when using it as a physicist would, it's somewhere between 50 and 500). A bit like the misunderstanding of "exponential" vs. "as the square of" in some previous banter. So your list of facts is clearly not 100% factual nor are the implications clear from the "facts".

[L4ces]

Originally Posted by HeartMD

Not for nothing but after having followed this EXTREMELY informative thread since the begining, I truely have lost all my confidence with this car. I also agree that having to replace bearings as a possible temporary insurance policy is something that I wasnt expecting on a 75k car. I hate having to be on the constant look out for any weird/new sound or having to send in my engine oil for analysis. The thought that once the car is out of warranty and having a catastrophic engine failure with a 25k price tag is something I dont want to deal with. Looks like my dreams of longterm ownership of this car have been shattered.

+1000

I hope the right people at BMW reads this and provide some response. I know I am reacting to this thread but, if any of this continues with other cars ... I don't know how to finish this sentence. You know how I feel.

And yesterday, after the car sat for 3 days, I started it in the morning and heard a loud weird clash. I said to myself, now I am experiencing the wtf now.

[thekurgan]

Originally Posted by PandaM3

I'm actually tempted to trade or sell my e90 m3 for a Lexus IS-F...

8 speed and V8 from the Lexus LS400... The confidence knowing that 200,000 miles is just breaking it in... And it has 90% of the performance of the M3

I need to go test drive one so I can decide... Replace rod bearings every 50,000 to 75,000 miles? Knowing that even with replacement (depending on the tech) there is still a chance of grenadine the engine soon after replacement... Or give up and get an IS-F

The V8 isn't from the LS 400. I'll say it's a nice car, but HARSH on the body and the faux exhaust tips are just .... silly. It's a girl's car with a V8.

[Ronnydashore]

Originally Posted by HeartMD

Not for nothing but after having followed this EXTREMELY informative thread since the begining, I truely have lost all my confidence with this car. I also agree that having to replace bearings as a possible temporary insurance policy is something that I wasnt expecting on a 75k car. I hate having to be on the constant look out for any weird/new sound or having to send in my engine oil for analysis. The thought that once the car is out of warranty and having a catastrophic engine failure with a 25k price tag is something I dont want to deal with. Looks like my dreams of longterm ownership of this car have been shattered.

If you are really a doctor, I am surprised you don't know how to sort through random data better. A super selective population online complaining about a catastrophic failure when 50k of these cars have been made is silliness to "lose total confidence"

So many people are basing their opinion on 3 posters on this site. BLind trust is a scary thing and I live in a city with tons of M3's and have met many with high mileage as well as spoke to my service department who has NEVER seen a bearing issue with the e9x m3.

Its not common guys, get back to reality and the fact M knows what they are doing rather than assume they are complete morons

[PandaM3]

Originally Posted by thekurgan

The V8 isn't from the LS 400. I'll say it's a nice car, but HARSH on the body and the faux exhaust tips are just .... silly. It's a girl's car with a V8.

At least it has 90% of the performance of the M3 and it will last 200,000 miles with little issue...

Name another car with at least 90% of the performance, 4 door sedan, looks properly aggressive on the race track while looking good cruising to a fancy restaurant and is completely reliable?