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03-01-2024, 09:59 AM | #23 | |
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Rather than introduce new variable measurements I've used all of the data from the BE Wiki, even for the OE & MAHLE parts. I did this to try and organise the data for my own understanding, but it ended up creating more questions. The most surprising was the variability of the wall thickness of the Clevite manufactured parts. The other is that average wall thickness on all parts are remarkably close. Maybe get Bert to drop me a mail as there are other inconsistencies / inaccuracies in the information. |
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03-01-2024, 10:00 AM | #24 | |
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All of the measurements at the wiki will eventually be redone. The shell thicknesses will be redone with the air gauge, and the clearances will be redone with a custom LVDT bore gauge accurate to 0.00005 inch. Those custom gauges are already done and ready to use. Preliminary tests show that the measurements with the custom gauges are 99% repeatable. The clearance measurements are performed with 34-points around the circle of each connecting rod/bearing assembly. Time availability is the only limiting factor at this point. |
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03-01-2024, 10:06 AM | #25 | |
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All measurements, old and new, were performed within 2-degrees F of each other, and within about 5% relative humidity of each other. This data is logged using a Kestrel gauge. True, it's not a scientifically controlled environment, but it's consistent across all sets, old and new. |
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03-01-2024, 10:21 AM | #26 | |
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The other anomaly is the assumption that the OE parts always use 1 of each colour code. Yes, this is the way it is presented in the BMW OEM catalogue, but it makes no sense to have graded parts and always to fit the same parts regardless of tolerance on the crank & rods. This could be achieved with a single bearing as both shells are the same design and material. To me this suggests that a combination of red / red, red / blue or blue / blue were used depending on the crank & housing size inline with standard OEM grading schemes. Unless a number of used sets with the colour codes still visible can be found and these documented against crank & housing size this will have to remain a reasonable assumption. And yes, it is not unknown for BMW OEM catalogue to have an error. I know of one vehicle where it states only 7 main bearing bolts are required |
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03-01-2024, 10:59 AM | #27 | |
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I look forward to seeing the new measurement data and the repeatability improving very close to 100% |
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03-01-2024, 11:21 AM | #28 | |
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Another problem with the wiki, and it should be an obvious one, only one set of shells were measured for everybody except BE. There's really no way to draw statistical meaningful conclusions from only one set of measurements, yet it's surprising how often people try to do exactly that. On the plus side, Bert is probably the only person around who still has a virgin set of 088/089 shells. |
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03-01-2024, 12:01 PM | #29 | |
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QUOTE=Green-Eggs;30948766] Another problem with the wiki, and it should be an obvious one, only one set of shells were measured for everybody except BE. There's really no way to draw statistical meaningful conclusions from only one set of measurements, yet it's surprising how often people try to do exactly that.[/QUOTE] OK, so is the data accurate or not? Forgive me if I'm misunderstanding reading the information, but the incorrect clearance theory was drawn from this data. Yet now we shouldn't draw meaningful conclusions? If there are multiple sets of BE bearings measured is that statistically more accurate? Because if so, the BE parts (along with other Clevite parts from VAC) are showing the largest variation in wall thickness of between 12um (0. 000472") & 13um (0.00512"). This would suggest that of all the parts measured Clevite produced parts have the largest tolerance. MAHLE have published theirs at 9um (0.00354"), independant measuring (including BE) has shown they are hitting sub 6um (0.00236"). ACL are stating 8um (0.00315"), but the BE data shows a marginal difference of 9um (0.00354"). QUOTE=Green-Eggs;30948766]On the plus side, Bert is probably the only person around who still has a virgin set of 088/089 shells.[/QUOTE] We have the OE data / print for the 088 / 089 parts so we no longer have to guess the specifications . What would be interesting is measurement data from removed 088 / 089 shells to compare to original drawing to establish the level of wear. Given that the OE colour codes tends to be removed by oil this would also involve a level of assumption. But given that indium copper intermetallics are often visible it would suggest the level of wear would be in the region of the overlay thickness of 13um (0.000512") |
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03-03-2024, 04:28 PM | #31 |
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This thread is getting super technical and over my head with all the specs and values! What I’m getting is that…OEM specs are good, staggering bearing sets “maybe” questionable. I think 🤔 that’s what Mahle is saying!
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03-04-2024, 11:08 AM | #32 | |
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OEM specs are almost double what has been quoted ( 0.0254mm / .001" quoted vs 0.046mm / .0018") In fact, if you run the data from the BE WIKI on the shells they have measured you will find ALL currently available bearings including OEM are remarkably close in clearance at around 2um (.00008") variation. Now, I'm deliberately using the wiki data as this is often where people are pointed so there is consistency in comparisons. Given the smallest part tolerance that is proven is the OEM parts at 6um (.0002") you begin to understand how small the difference is on all of these parts. The only time we see a larger deviation on clearance is when you run theoretical min / max clearances between the parts. The problem is here that the largest measured deviation on some parts is over 12um (.00047") where others are deviating only 1um (.00004"). This then shows the parts with the largest measured size deviation will show a larger theoretical clearance. Theoretical clearances based on min / max is only relevant when absolute min / max sizes are known, including production tolerance. We don't have this data for all parts. For reference here are the production tolerances that are known. OEM 6um total - source original drawing MAHLE 9um total - source original drawing ACL 8um total - source email to ACL King currently unknown, data requested BE currently unknown In short, the differences between bearings available are as follows: 1. Eccentricity (is this by design or wider tolerance? Without drawings it's unknown) 2. Material specification 3. Brand 4. production tolerances So choose your bearings based on the above, local availability, price or preference of the person doing the job. All will have clearances within spec based on published data. And staggering bearing sets or using extra clearance (ACL HX for eg) is perfectly OK. but if it were me, I would only use after shaft and housing measurements are checked to prove the extra clearance was required or desirable. |
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03-04-2024, 01:52 PM | #33 | |
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Again I’m aware of that you are not employed by MAHLE and I don’t expect you to know all answers. Still curious of your (and possibly other – initiated - peoples) view here: Quick question on the BMW OE shells As the shaft and housing variation together is 0.030 on its own (according to the specs I’ve seen?), I still don’t quite get how BMW clearance variance can be as tight as 33um (0.062 – 0.029mm), with a shell variation of apparently 0.006 on top. There are a couple of different shell thicknesses to play around with but doesn’t help really if surrounding HW isn’t known. So each shafts and houses are measured during assembly of the engine where after matched with the shells? MAHLE MAHLE’s target extended clearance (54um vs OE 46um) from what I understand to avoid getting too tight/lose in the ends due to overall variation (rather than increasing the oil film)? Others The various “extended” shells seems to all target around 55-60um clearance, i.e. similar to MAHLE? So... should my understanding be that 1) Originally installed OE bearings should theoretically be fine “for ever”, obviously assuming the engine is maintained/treated correctly. 2) If one for whatever reason (tons of miles, 10th owner etc) want to replace the RBs it should be with extended clearance due to mentioned tolerance stack up? Thanks, Nik |
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03-05-2024, 06:15 AM | #34 | |||
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Hi Nik,
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It seems odd to use one of each grade on assembly as per the parts catalogue. This could have been achieved with a single grade part. Again, I have seen no data to prove or disprove what colour codes were fitted from the factory. Quote:
Correct. The increase in clearance is mainly due to offering a single grade part to ensure it works at all extremes and the material MAHLE has selected to use. I think in the MAHLE document they used the phrase er on the side of caution :-) What others are targeting is difficult to say. I see posts saying "we are targeting x clearance" for example, but no data to back this up. I know some are stating "real world" measurements, but for me the first stage has failed. How do we know the parts measured are the size the manufacturer intended i.e. are they in spec? I know you kindly queried ACL on their tolerances so maybe I will use that data along with the MAHLE Motorsport data which will give us theoretical min / max as well as average clearance from drawing specs. Maybe BE will divulge their specs and we can add those too. I have asked king for the same information. Maybe then we can start to build a clear picture of target Vs actual each bearing brand available. Quote:
We really need to define the "extended clearance" It is not unusual for aftermarket bearings to run marginally larger clearances. This is due to aftermarket parts only having a single grade V's OE multiple grades. It ensures the part stays within spec at the extremes of tolerances. For me "extended clearance" for means parts that have additional clearance over the standard part from the same manufacturer. These commonly use an X in the part number (ACL / Clevite HX, King STDX). These parts typically have 0.025mm (.001") extra clearance over the standard part from the same company. Anything else would be a standard part (even though technically they have a little extra clearance to OEM). |
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03-05-2024, 11:06 AM | #35 | |||
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03-05-2024, 01:08 PM | #36 | |
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http://wiki.rcollins.org/core/index....ring_Clearance |
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03-05-2024, 02:27 PM | #37 | |
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