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      02-10-2015, 10:56 PM   #2201
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Quote:
Originally Posted by swartzentruber View Post
Not RG, but I'll take a stab. I'm sure wearing to the point of failure is a function of several things, not just simply clearance. My suspicion is that wear to the point of failure is somewhat highly correlated to how much time your engine spends at the upper RPM range, with maybe a few other things like cold starts, oil change intervals having lesser secondary effects, along with the clearance. A 3 sigma deviation with a lot of higher rpm driving would probably fail fairly quickly in life (i.e. 30k miles or less). However, it would be rather difficult to know for a higher mileage failure if you were a super conservative 3 sigma or an average 2 sigma or a really bad 1 sigma.
Good points.

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RG, do you have any way of differentiating your clearance ranges on these 12 engines for pre-2011 leaded bearings vs the 2011+ lead free bearings?
I might have been able to ask for clearance specs at the same time, but I didn't want to get too greedy when asking a favor. Even though BMW makes a one-size-fits-all rod bearings, this particular shop does sift through and measures parts to find those that best fit that particular crank. So it might not have been helpful in getting the data I think you're asking for.

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If would be interesting to see if the deviations from standard are better or worse for the two types, particularly since BMW switched suppliers.
Ah, All of these would have been measured during the 702/703 bearing time frame. You bring up a good point however. I wonder if they have data on stock engine builds going all the 088/089 days. I can ask, but it might cost me a steak dinner.

Quote:
SFP's data (I know, your favorite guy) suggests a trend of the 2011+ engines to fail earlier, and this could easily be explained if the lead free bearings had a slightly wider spread (more variation), which would suggest a higher proportion of 3 sigmas and more tendency to fail earlier.
It could also be explained in the two other ways: 1) The newer bearings are 3.8 times harder than the previous lead/copper bearings. 2) The newer bearings aren't embeddable like the older lead/copper bearings. So when particles enter the journal areas, they would tend to cause more damage than the more embeddable lead/copper bearings.

Quote:
By the way RG, nice work and welcome back (this coming from somewhat of a former RG critic). I think this data collection does move the conversation forward.
Thank you very much!

EDIT: When I re-read your comments, I wonder if you're thinking we measured rod clearance. We didn't. We only measured bearing journal size. If we could also measure 96 connecting rod bearings installed, that could add another dimension to this data. Maybe it will be worth that steak dinner to see if I can get this data, even if it's only for 702/703 bearings.

Last edited by regular guy; 02-10-2015 at 11:21 PM..
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      02-12-2015, 08:21 PM   #2202
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Originally Posted by regular guy View Post
Basically, tolerance stacking goes like this. Each crankshaft, rods, and bearings have a +/- tolerance associated with them. The parts chosen at random during manufacturing can be +sized, or -sized. We're most interested in those combinations which create a dangerously small oil journal clearance and lead to early engine failure.

Let's say you take a crankshaft with a +deviation journal but still within factory spec, and mate it to a connecting rod and bearing with a -deviation but still within factory spec. This combination potentially creates a dangerously small oil journal clearance and is what we're calling "tolerance stack up" for the purpose of this thread.

I was very intrigued by bone stock motors blowing while others survive for no apparent reason. I first started this thread to bring attention to the journal clearance issue. But as the thread progressed, the tolerance stack up theory came up as a possible explanation for these blown motor. Seeing a 3% 3-sigma deviation could be just a coincidence, or it could also be significant evidence that this is a likely cause of these blown motors.
Thank you for the explanation. Your definition matched my assumption. That leads me to some follow up questions:

Given that tolerances are likely to similarly vary on every engine in every car, and therefore that there are likely to be situations in every car in which a "+deviation journal but still within factory spec" will "mate . . . to a connecting rod and bearing with a -deviation but still within factory spec," why is it only the S65 (or, perhaps the S54, S65, and S85) that have this problem?

Is it because the target clearances (around which there are normal +/- variances) are already insufficient on the S65 (and possibly the S54 and S85), such that the design leaves no room (pun intended) for situations in which extreme +variances on the journal coincide with extreme -variances on the rod and bearing?

These are genuine questions, not rhetorical.
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      02-12-2015, 09:55 PM   #2203
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Quote:
Originally Posted by Hujan View Post
Thank you for the explanation. Your definition matched my assumption. That leads me to some follow up questions:

Given that tolerances are likely to similarly vary on every engine in every car, and therefore that there are likely to be situations in every car in which a "+deviation journal but still within factory spec" will "mate . . . to a connecting rod and bearing with a -deviation but still within factory spec," why is it only the S65 (or, perhaps the S54, S65, and S85) that have this problem?
You correctly answer your own question below.

Quote:
Is it because the target clearances (around which there are normal +/- variances) are already insufficient on the S65 (and possibly the S54 and S85), such that the design leaves no room (pun intended) for situations in which extreme +variances on the journal coincide with extreme -variances on the rod and bearing?

These are genuine questions, not rhetorical.
Yes you nailed it with your understanding. Look at the front page, post-1, at the section "BMW ///M Engines (Rod Bearings)." Look at the "Ratio(SAE)" column. In that table, you will see how the S65 clearance to journal ratio is smaller than all the other BMW ///M engines. Then look at the Ferrari engine for comparison. Even after the new 702/703 bearings came online, this ratio still matched the smallest clearance ratio of all other ///M engines. Some people suspect it's not only clearance, but clearance + the high RPMs that is the real problem with the S65. If that's the case, then look at the "RPM-Clr Ratio" column of that table. It's a made-up metric, but it still conveys relevant information. If RPM really is a factor, then the bigger the number, the worse it is on your engine. So compare the S65 to the Ferrari, and you can see the the difference in the two design philosophies.
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      02-12-2015, 11:18 PM   #2204
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Originally Posted by regular guy View Post
You correctly answer your own question below.



Yes you nailed it with your understanding. Look at the front page, post-1, at the section "BMW ///M Engines (Rod Bearings)." Look at the "Ratio(SAE)" column. In that table, you will see how the S65 clearance to journal ratio is smaller than all the other BMW ///M engines. Then look at the Ferrari engine for comparison. Even after the new 702/703 bearings came online, this ratio still matched the smallest clearance ratio of all other ///M engines. Some people suspect it's not only clearance, but clearance + the high RPMs that is the real problem with the S65. If that's the case, then look at the "RPM-Clr Ratio" column of that table. It's a made-up metric, but it still conveys relevant information. If RPM really is a factor, then the bigger the number, the worse it is on your engine. So compare the S65 to the Ferrari, and you can see the the difference in the two design philosophies.
Thank you. I'll admit I don't understand the full implications of those numbers, but certainly the differences are pretty stark between the other vehicles and the E9x M3s, particularly for those built through 2010.

So is it just a matter of BMW screwing the pooch on their design? This is not unfathomable. (See 991 GT3 engine fires.) But if it does come down to a design defect, it is somewhat surprising that they never acknowledged the defect and initiated a recall. (Although I suppose they judged the cost of replacing failed engines to be less than the cost of doing a widespread recall.)
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      02-13-2015, 06:06 AM   #2205
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Most recalls are safety related. If people were dying in E9xM3s when the engines let go, there might be a recall. Even then, BMW would balance the cost of litigating cases and paying off the victims' families against the cost of recalling all cars and replacing all rod bearings or rods or cranks. Instead, BMW is doing as little as possible, and replacing engines only when it cannot avoid doing so. This is obviously the cheapest approach.
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      02-13-2015, 06:22 PM   #2206
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Originally Posted by pbonsalb View Post
Most recalls are safety related. If people were dying in E9xM3s when the engines let go, there might be a recall. Even then, BMW would balance the cost of litigating cases and paying off the victims' families against the cost of recalling all cars and replacing all rod bearings or rods or cranks. Instead, BMW is doing as little as possible, and replacing engines only when it cannot avoid doing so. This is obviously the cheapest approach.
That would be playing with fire. Google "Ford Pinto memo" and see what happens when car companies put a priority on economics when it comes to safety-related defects with their cars.
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      02-13-2015, 08:40 PM   #2207
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Quote:
Originally Posted by Hujan
Quote:
Originally Posted by pbonsalb View Post
Most recalls are safety related. If people were dying in E9xM3s when the engines let go, there might be a recall. Even then, BMW would balance the cost of litigating cases and paying off the victims' families against the cost of recalling all cars and replacing all rod bearings or rods or cranks. Instead, BMW is doing as little as possible, and replacing engines only when it cannot avoid doing so. This is obviously the cheapest approach.
That would be playing with fire. Google "Ford Pinto memo" and see what happens when car companies put a priority on economics when it comes to safety-related defects with their cars.
Yup.. That's a crazy story. Unbelievable what they did there. Fortunately (although it still can be a serious safety issue), an engine blowing on the road is far from a car exploding when rear ended...
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      02-13-2015, 09:33 PM   #2208
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Ford Pintos in the 70s was not the last time car makers adopted this approach, unfortunately. The internet, however, has made covering up and hiding stuff much harder.
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      02-14-2015, 05:24 PM   #2209
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Welcome back RG. I've taken a long break from the forum myself as well. There was some crazy stuff happening with moderation (IMHO) and the whole S55 under rating debate.

Anyway, thanks for the additional data. More data always helps. However, some criticisms as well:
  1. 100% of your observed journal sizes fall within 3σ, there is not 3% of the data outside of 3σ, period. As with any normal distribution, by definition, about 0.2% of all data (both high and low sides will be outside of +/- 3σ. This is far less than one observation out of about 100 and thus no observations are outside of 3σ.
  2. Tolerance stacking is a completely universal phenomena for every dimension of every assembly in every industry. The mere observation of and even quantification of the amount of tolerance stacking present simply IS NOT evidence that tolerance stacking is the cause of failures. The reason for this should be obvious. There is no yardstick/metric (that we have) by which to measure the effect of tolerance stacking. A metric would be something like an observation correlating engine lifetime vs. measured bearing clearance, where clearances are known before the engine is put into use. No one has ANY sort of data along these lines for the S65. Yes we can surely say that with no clearances (or perhaps just enough to allow rotation) an engine will fail almost immediately. We also know that with somewhere in the range of .001 in/in clearance (in of clearance per in of journal size) can result in an extremely long engine life, say perhaps 300k-500k mi or even more. But in this case we have nothing in between that identifies the strength of the effect or an obvious cut off point of the effect. So for this reason along with point #1 above, your 3% of engines failing based on being 3σ "out" claim is both incorrect and is not justifiable. Furthermore, even if your observation about the statistics were correct, the conclusion does not follow. I've also not seen any evidence whatsoever that the to date failure rate is anywhere close to 3%. It has not been updated in some time, but back in early 2014, I made the most careful calculation I've seen, taking into account forum ownership rates, actual empirical observed failures and other factors to conclude a failure rate of about 0.1% - 0.5%. Link to that post here.
  3. In short we are left with very little additional proof of cause. There is nothing here that moves this argument beyond speculation. The updated *nominal* journal sizes here result in a 0.83 thousandths of an in/in which still resides within/above the prior identified minimum Clevite spec of 0.75 thousandths of an in/in. And certainly it does not make sense to "cherry pick" the tight end result of the spread in clearances to say the S65 clearance is less than the minimum Clevite spec (the tight end is in fact less than the Clevite minimum). Why can't we do so? That spec is based on NOMINAL DIMENSIONS, with the obvious understanding that tolerance stacking always exists! Some additional data that would be great would be an empirical observation that the standard deviation of BMWs journal sizes are significantly larger than an industry norm (and I highly doubt they are, my guess is that they are smaller).
  4. I'm still of the belief that BMW knew exactly what clearance they wanted, fully understood the tradeoffs with engine longevity vs. range of clearances they would obtain from their and their suppliers individual part tolerances and then chose the values for other benefits they offer, along the lines of NVH, high rpm capability, efficiency, etc. Now could they have chosen a nominal clearance and a tolerance for that clearance that would definitively result in significantly fewer low mileage failures? Perhaps, but there is nothing more than speculation to support that presently. Until there are some (more than a couple...) builds with fully blueprinted specs known for clearances and those engines are monitored for wear or lifetime, we'll continue to be mostly in the dark and speculating.
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      02-14-2015, 09:41 PM   #2210
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Helloa all just replaced my rod bearing at 65k miles. I have a 2009 m3

The findings were right in line with normal wear and tear.

I drive my car very hard and I am the third owner.

Tell me what you think of the pics
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      02-15-2015, 03:14 AM   #2211
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Originally Posted by swamp2 View Post
[.....]
Good insights as ever...Welcome back.
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      02-15-2015, 10:17 AM   #2212
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Quote:
Originally Posted by swamp2 View Post
Welcome back RG. I've taken a long break from the forum myself as well. There was some crazy stuff happening with moderation (IMHO) and the whole S55 under rating debate.
[*]In short we are left with very little additional proof of cause. There is nothing here that moves this argument beyond speculation. The updated *nominal* journal sizes here result in a 0.83 thousandths of an in/in which still resides within/above the prior identified minimum Clevite spec of 0.75 thousandths of an in/in. And certainly it does not make sense to "cherry pick" the tight end result of the spread in clearances to say the S65 clearance is less than the minimum Clevite spec (the tight end is in fact less than the Clevite minimum). Why can't we do so? That spec is based on NOMINAL DIMENSIONS, with the obvious understanding that tolerance stacking always exists! Some additional data that would be great would be an empirical observation that the standard deviation of BMWs journal sizes are significantly larger than an industry norm (and I highly doubt they are, my guess is that they are smaller).[*]I'm still of the belief that BMW knew exactly what clearance they wanted, fully understood the tradeoffs with engine longevity vs. range of clearances they would obtain from their and their suppliers individual part tolerances and then chose the values for other benefits they offer, along the lines of NVH, high rpm capability, efficiency, etc. Now could they have chosen a nominal clearance and a tolerance for that clearance that would definitively result in significantly fewer low mileage failures? Perhaps, but there is nothing more than speculation to support that presently. Until there are some (more than a couple...) builds with fully blueprinted specs known for clearances and those engines are monitored for wear or lifetime, we'll continue to be mostly in the dark and speculating.[/LIST]
It is less than the minimum clevite spec. .75 would be .0014 clearance. I have measured myself quite a few that were .0012-3. Even going off the clevite spec it is still wrong. Clearance is only half that spec though, the oil must be mated to the clearance. RPM, torque all must be taken to account. The problem with the .0013 clearance is it needs to be mated with a 20wt oil like a honda accord. But they dont turn 8500 and they dont make the power either, therefore no way would I try to run a 20wt oil in the m3.
So could you run that clearance spec, sure honda and toyota do it all the time but they also run 0w-20
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      02-15-2015, 10:23 AM   #2213
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For the 8000 rpm Honda engines like the old s2000 motor, what was the oil spec?
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      02-15-2015, 10:52 AM   #2214
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Quote:
Originally Posted by kawasaki00 View Post
It is less than the minimum clevite spec. .75 would be .0014 clearance. I have measured myself quite a few that were .0012-3. Even going off the clevite spec it is still wrong. Clearance is only half that spec though, the oil must be mated to the clearance. RPM, torque all must be taken to account. The problem with the .0013 clearance is it needs to be mated with a 20wt oil like a honda accord. But they dont turn 8500 and they dont make the power either, therefore no way would I try to run a 20wt oil in the m3.
So could you run that clearance spec, sure honda and toyota do it all the time but they also run 0w-20
Yes, surely the combination of load, rpm, clearance and oil are all strongly related. I also completely botched the simple division of RGs updated numbers in my prior post (point #3). The result from his nominals is 0.66 thousandths in/in, about 10% tighter than the minimum Clevite spec of 0.75. Despite this, I still believe firmly in my point #4 in my prior list (and all of the other points). Your point about measuring some nominals even tighter is largely irrelevant. Again all assemblies in all industries have tolerance stack, there will be a nominal, some will be loose and some tight. The existence of numbers smaller than the mean is a truism, not a damnation that BMW screwed something up. That observation is universally true for all engines. Again, what is the formula, relationship, observed data, etc. for bearing/engine longevity vs. bearing clearance? Surely moving toward too large of a clearance could be equally bad for engine longevity, but we have no real data there either.
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      02-15-2015, 12:53 PM   #2215
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Quote:
Originally Posted by swamp2 View Post
Yes, surely the combination of load, rpm, clearance and oil are all strongly related. I also completely botched the simple division of RGs updated numbers in my prior post (point #3). The result from his nominals is 0.66 thousandths in/in, about 10% tighter than the minimum Clevite spec of 0.75. Despite this, I still believe firmly in my point #4 in my prior list (and all of the other points). Your point about measuring some nominals even tighter is largely irrelevant. Again all assemblies in all industries have tolerance stack, there will be a nominal, some will be loose and some tight. The existence of numbers smaller than the mean is a truism, not a damnation that BMW screwed something up. That observation is universally true for all engines. Again, what is the formula, relationship, observed data, etc. for bearing/engine longevity vs. bearing clearance? Surely moving toward too large of a clearance could be equally bad for engine longevity, but we have no real data there either.
It is truism up to a limit. You cannot simply discount real measurements that might indicate your process is out of control, or that there is a variable that wasn't adequately accounted for post-production.

Anyway, I think at this point I want to see how the new design performs once released.
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      02-15-2015, 01:10 PM   #2216
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Quote:
Originally Posted by pbonsalb View Post
For the 8000 rpm Honda engines like the old s2000 motor, what was the oil spec?
=> http://www.bobistheoilguy.com/forums...Number=1144094
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      02-15-2015, 01:11 PM   #2217
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Swamp have you been lurking in the shadows waiting for RG's ban to be lifted? Seems kind of odd that you suddenly show up right after he does...

Hopefully any debate can remain civilized this time around.
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      02-15-2015, 01:38 PM   #2218
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Quote:
Originally Posted by gatorfast View Post
Swamp have you been lurking in the shadows waiting for RG's ban to be lifted? Seems kind of odd that you suddenly show up right after he does...

Hopefully any debate can remain civilized this time around.
Well, if you really must know, I have not been using the forum much at all. I was pretty pissed about the issue mentioned above. It was totally out of control (IMHO). However, after a long 100% absence here I've been periodically keeping up with a couple of threads, this one included.

Obviously data is always a good thing and I've commended RG on multiple occasions, as well as help fund the purchase of parts whose measurements are reported here in this thread. Most of the posts since RG left were far less interesting and largely inconsequential as compared to some new data. Again, RGs conclusions about the data are absolutely not accurate nor founded and that is worthy of comment and discussion.

In short the answer to your question is a clear "no". Does that satisfy your curiousity?
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      02-15-2015, 01:47 PM   #2219
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Quote:
Originally Posted by swamp2 View Post
Yes, surely the combination of load, rpm, clearance and oil are all strongly related. I also completely botched the simple division of RGs updated numbers in my prior post (point #3). The result from his nominals is 0.66 thousandths in/in, about 10% tighter than the minimum Clevite spec of 0.75. Despite this, I still believe firmly in my point #4 in my prior list (and all of the other points). Your point about measuring some nominals even tighter is largely irrelevant. Again all assemblies in all industries have tolerance stack, there will be a nominal, some will be loose and some tight. The existence of numbers smaller than the mean is a truism, not a damnation that BMW screwed something up. That observation is universally true for all engines. Again, what is the formula, relationship, observed data, etc. for bearing/engine longevity vs. bearing clearance? Surely moving toward too large of a clearance could be equally bad for engine longevity, but we have no real data there either.
Saying that it is irrelevant shows you need to stick to reading books because you don't know much about engines. Tolerance stack is there for a reason. If you take all the worst case scenarios it still has to work. If it doesn't then BMW did a crap job of designing it.
Your so called truism is a fancy word for they can't control tolerance worth a heck. If there were a engine here or there like the one Malek had that looked like there was something wrong with the main line and it ate the first journal up that is a truism as you would call it.
How many sets of rods have you fit for the s65? RG and I have fit many and all but one set I did was under the clevite spec.
As far as it being too loose there is a point that it will hurt it but if it were a .0005 too loose the only person that will know about it is the guy that bolted it together.
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      02-15-2015, 01:48 PM   #2220
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Quote:
Originally Posted by 1love View Post
It is truism up to a limit. You cannot simply discount real measurements that might indicate your process is out of control, or that there is a variable that wasn't adequately accounted for post-production.
No, it is a truism, tolerance stacking and a resulting potential for that to be a consequential design/performance issue exist in every assembly in every device in every industry. Here there is absolutely no baseline about crankshaft rod journal standard deviations nor more importantly those vs. longevity. The latter would be significantly stronger evidence than the former. In this particular case the standard deviation of the rod journals is 1/10th of one thousandth of an inch. Is that small or large, small or large compared to what. Again, there is NO "yardstick". I'm sure there are some, but they have not been discussed here.

Quote:
Originally Posted by 1love View Post
Anyway, I think at this point I want to see how the new design performs once released.
Fully agree, the proof is always "in the pudding". However, it will take well more than 1 or 2 engines to constitute proof.

I'm highly amused by the recent (highly negative) updates on coated bearings. There was outright joy, enthusiasm and near worship for such a wonderful solution for this problem when they first became available. And although I've not seen the data, nor heard that there is much of it, it seems clear that this solution, just ain't a solution. And of course, yours truly held this opinion early that reduced clearances were a bad idea and that the vendors providing these parts/services (treated or coated bearings) provided not a single iota of data/proof that they had a solution (or even a minor improvement).
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      02-15-2015, 01:56 PM   #2221
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Quote:
Originally Posted by kawasaki00 View Post
Saying that it is irrelevant shows you need to stick to reading books because you don't know much about engines. Tolerance stack is there for a reason. If you take all the worst case scenarios it still has to work. If it doesn't then BMW did a crap job of designing it.
Your so called truism is a fancy word for they can't control tolerance worth a heck. If there were a engine here or there like the one Malek had that looked like there was something wrong with the main line and it ate the first journal up that is a truism as you would call it.
How many sets of rods have you fit for the s65? RG and I have fit many and all but one set I did was under the clevite spec.
As far as it being too loose there is a point that it will hurt it but if it were a .0005 too loose the only person that will know about it is the guy that bolted it together.
Great way to get off on a cordial reengagement... But, nope, you're totally missing the point, as usual.

Please provide me with one shred of data about bearing clearance tolerance variation vs. engine lifetime. You better stick to turning wrenches rather than discussing matters dominated by serious engineering and science. After all, you've never shared a single iota about your credentials.

Too tight is no good and too loose is as well, there is a sweet spot in between and it depends on loads, part strength, redline, oil and other factors.

For about the millionth time, I am NOT saying that extremes in tolerance stacking is not a factor here, I'm just saying that we have no proof and don't even have an appropriate metric or "yardstick" to use along with RGs new data.

Do you feel that 1/10th of a thou standard deviation for crank rod journals is significantly higher than norm for a high performance production engine? If so that opinion or conclusion should be supported by your data. Let's see that. Again, that is only the first step, the next is some metric about how bad this standard deviation is (really the standard deviation in the clearance itself ultimately, but the new data here is more about the crank).
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      02-15-2015, 01:57 PM   #2222
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Quote:
Originally Posted by SMRT_SG*E92 M3 View Post
Helloa all just replaced my rod bearing at 65k miles. I have a 2009 m3

The findings were right in line with normal wear and tear.

I drive my car very hard and I am the third owner.

Tell me what you think of the pics
What pics ?
See 0 pics ..
Actualy we all would love to see pics of your bearings...
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