Blown motors, Rod Bearing failure S65 Registry.

Sneaky Pete wrote

My meagre understanding of fluid dynamics is that increasing flow through the rod bearings by increasing clearance will *not* increase flow through the main bearings...in fact the opposite.
This may or may not be a good analogy but:
Imagine a pressurised hose with 16 holes in it, 8 representing the rate at which oil flows out of the rod bearings and 8 for the mains.
Now if you make 8 (RB) holes bigger the oil will flow out far more quickly out of those and less so out of the other 8 (mains). The flow controlled oil pump *might* see a very small drop in flow but it will be only a part of the overall output of the Mahle pump (to the Vanos, timing chains, piston cooling, cam lubrication etc)....not as a direct proportion of the reduced flow through the main bearings.
It may not make a dramatic difference or it may in some cases be just enough to significantly reduce service life of the main bearings.
Noting that one would imagine that the engine design team went to some length to balance the flow between these two sets of bearings for maximum service life...not expecting end users to change that balance.

The rod bearings are fed from the mains, so are "down stream". Any oil flowing to the rod bearings comes via the main bearings first.

PaulGros wrote

I often see the quote about hand measuring into matched sets. But I genuinely don't understand this claim. As far as I am aware you cannot specify the wall thickness you want / require from them. The Wiki data also shows the largest variation in size for them also from all parts measured, double what some brands are achieving. So what is the hand measuring achieving?

I also don't understand why its believed hand measuring is "better". Humans make more mistakes than machines, and laser / optical measuring equipment is more accurate and consistent.

Suggesting clearance "specifications" based on measuring (typically a few number of shafts/housings vs shells) imo simply does not make sence. This is an area I feel sometimes is misinterpreted.

While measuring, binning and matching shells imo is great and certainly reduce the actual clearance variation.

Helmsman wrote

Suggesting clearance "specifications" based on measuring (typically a few number of shafts/housings vs shells) imo simply does not make sence. This is an area I feel sometimes is misinterpreted.

While measuring, binning and matching shells imo is great and certainly reduce the actual clearance variation.

It may make sense if we knew the sorting criteria. What are they being matched to? I see the claims, yet the WIKI data shows over 12um difference in wall thickness. The data doesn't match the claim. So either the data is wrong, I'm misunderstanding the data, or the claim is wrong :-)

PaulGros wrote

It may make sense if we knew the sorting criteria. What are they being matched to? I see the claims, yet the WIKI data shows over 12um difference in wall thickness. The data doesn't match the claim. So either the data is wrong, I'm misunderstanding the data, or the claim is wrong :-)

Hmm, maybe I missunderstand something here (happened before...), but my assumption is that the shell variation is intended to be sorted with the binning/matching i.e. you get a pair with total thickness confirmed down to the measuring tool tolerance which assumingly is significantly better than the 12umx2 possible variation.

But sure, what clearance this result in is obviously completely depedning on the surrounding hardware. From what I understand the housing is known (13um variation?) while the shaft is estimated (I believe ACL use 0.016um and BE measured 0.010 variation). So a (theoretical) clearance variation is in my mind not possible to quote while confirmed combined shell thickness is tightening it down a bit.

I'm assuming that MAHLE have BMWs shaft/housing tolerances?

Helmsman wrote

Hmm, maybe I missunderstand something here (happened before...), but my assumption is that the shell variation is intended to be sorted with the binning/matching i.e. you get a pair with total thickness confirmed down to the measuring tool tolerance which assumingly is significantly better than the 12umx2 possible variation.

But sure, what clearance this result in is obviously completely depedning on the surrounding hardware. From what I understand the housing is known (13um variation?) while the shaft is estimated (I believe ACL use 0.016um and BE measured 0.010 variation). So a (theoretical) clearance variation is in my mind not possible to quote while confirmed combined shell thickness is tightening it down a bit.

I'm assuming that MAHLE have BMWs shaft/housing tolerances?

Maybe that is what is happening, I really don't know. But if that was the case, why is there such a large variation in the wiki measurements?

I do have the original figures for the shaft and housing, but it is somewhay academic. As long as you use the same figures to calculate all parts then you can compare. Maybe I am misunderstanding the way the data is presented (it's been a long week!). There is shaft size measurements (which correspond very closely with BMW average) but no housing size data. There is measurements once bearings are in the rod for each part and a clearance figure given. You can take this data and back calculate to an average housing size as you have shaft size, clearance and wall thickness. But this isn't adding up, I'm seeing theorutical differences of 30um. So either the data is wrong, I'm misunderstanding the data or I've transposed the data incorrectly.

This is why I believe we need manufacturer data on shell thickness, we can then use a standard housing and crank figure and calculate theoritocal clearances. This can then be compared to measured shell thickness and calculate with the same crnak and housing size. This shoukd give us two data points. What the bearing manufacturer is targeting and what they are actually achieving.

PaulGros wrote

Maybe that is what is happening, I really don't know. But if that was the case, why is there such a large variation in the wiki measurements?

I've touched on this, or rather how the variation span can be shortened/moved, with BE several times but never really understood the answer. I count on the guys to chime in here.

PaulGros wrote

I do have the original figures for the shaft and housing, but it is somewhay academic. As long as you use the same figures to calculate all parts then you can compare. Maybe I am misunderstanding the way the data is presented (it's been a long week!). There is shaft size measurements (which correspond very closely with BMW average) but no housing size data. There is measurements once bearings are in the rod for each part and a clearance figure given. You can take this data and back calculate to an average housing size as you have shaft size, clearance and wall thickness. But this isn't adding up, I'm seeing theorutical differences of 30um. So either the data is wrong, I'm misunderstanding the data or I've transposed the data incorrectly.

From what I understand the housing spec is official: Max 56,013, Min 56.000. No?
While for the shaft spec:
ACL use Max 51,991, Min 51,975 and
BE I believe use Max 51,9887 and Min 51,9786 i.e. a tad tigher.

PaulGros wrote

This is why I believe we need manufacturer data on shell thickness, we can then use a standard housing and crank figure and calculate theoritocal clearances. This can then be compared to measured shell thickness and calculate with the same crnak and housing size. This shoukd give us two data points. What the bearing manufacturer is targeting and what they are actually achieving.

We have ACL. Haven't been into BE wiki for a while but surely they spec'ed their shell thickness?

Anyways, great if BE took part in the discussion.

Helmsman wrote

I've touched on this, or rather how the variation span can be shortened/moved, with BE several times but never really understood the answer. I count on the guys to chime in here.



From what I understand the housing spec is official: Max 56,013, Min 56.000. No?
While for the shaft spec:
ACL use Max 51,991, Min 51,975 and
BE I believe use Max 51,9887 and Min 51,9786 i.e. a tad tigher.



We have ACL. Haven't been into BE wiki for a while but surely they spec'ed their shell thickness?

Anyways, great if BE took part in the discussion.

I'm on my phone at home so don't have the specs inform of me, they look about right though. So if you check the data for ACL as we know the specs and calculate back to the housing size. I can send a copy of my calculations to check if you like?

PaulGros wrote

I'm on my phone at home so don't have the specs inform of me, they look about right though. So if you check the data for ACL as we know the specs and calculate back to the housing size. I can send a copy of my calculations to check if you like?

FWIW, sure thing mate...

PaulGros wrote

It may make sense if we knew the sorting criteria. What are they being matched to? I see the claims, yet the WIKI data shows over 12um difference in wall thickness. The data doesn't match the claim. So either the data is wrong, I'm misunderstanding the data, or the claim is wrong :-)

"What it's being measured to" is probably one of the best documented pieces of this puzzle on many threads and many discussion groups. For clarity, it's also been documented at the BE Wiki.

http://wiki.rcollins.org/core/index.php?title=BE-FAQ_-_Mixed_sets_of_STD/%2B025_shells

PaulGros wrote

Maybe that is what is happening, I really don't know. But if that was the case, why is there such a large variation in the wiki measurements?

It's intentional to put the widest range of shell thickness variance in play to see the effect on clearances and to document it as such.

I do have the original figures for the shaft and housing, but it is somewhay academic. As long as you use the same figures to calculate all parts then you can compare. Maybe I am misunderstanding the way the data is presented (it's been a long week!). There is shaft size measurements (which correspond very closely with BMW average) but no housing size data.

Housing size is documented by BMW, and this is what (hopefully) everybody is using.

There is measurements once bearings are in the rod for each part and a clearance figure given. You can take this data and back calculate to an average housing size as you have shaft size, clearance and wall thickness. But this isn't adding up, I'm seeing theorutical differences of 30um. So either the data is wrong, I'm misunderstanding the data or I've transposed the data incorrectly.

The data is definitely not inaccurate or wrong.

This is why I believe we need manufacturer data on shell thickness, we can then use a standard housing and crank figure and calculate theoritocal clearances. This can then be compared to measured shell thickness and calculate with the same crnak and housing size. This shoukd give us two data points. What the bearing manufacturer is targeting and what they are actually achieving.

I'm not sure I'm following you or what you're thinking is missing here. Is it...that you want the measurements of the virgin rod housings before the shells were installed?

PaulGros wrote

The rod bearings are fed from the mains, so are "down stream". Any oil flowing to the rod bearings comes via the main bearings first.

Its the same feed though?
If you massively increased rod bearing clearance, oil flow through the mains would be reduced or not?

Sneaky Pete wrote

Its the same feed though?
If you massively increased rod bearing clearance, oil flow through the mains would be reduced or not?

Pete, there are no shells available that "massively" increase clearance, are there.

Green-Eggs wrote

"What it's being measured to" is probably one of the best documented pieces of this puzzle on many threads and many discussion groups. For clarity, it's also been documented at the BE Wiki.

http://wiki.rcollins.org/core/index.php?title=BE-FAQ_-_Mixed_sets_of_STD/%2B025_shells

Ok, it makes a little more sense now. The Clevite parts have a wider manufacturing tolerance than others @ 12.7um

Helmsman wrote

Pete, there are no shells available that "massively" increase clearance, are there.

Thats wasn't the suggestion...rather, can increasing the RB clearance have an effect on the flow through the main bearings.

Put it another way if you kept increasing the RB clearance towards infinity would the oil flow through the mains be affected at any time.

Green-Eggs wrote

Housing size is documented by BMW, and this is what (hopefully) everybody is using.

The max housing is 56.013mm. Maybe I'm missing this in the wiki, I can only see measured sizes when the bearing is installed, headed clearance measurements.

Green-Eggs wrote

I'm not sure I'm following you or what you're thinking is missing here. Is it...that you want the measurements of the virgin rod housings before the shells were installed?

If I take BE V2 shell thickness from the wiki I get the following dimensions

Std Bearing = 1.9812 - 1.9939
+0.025 Bearing = 1.9939 - 2.0066

So we get a theoretical total wall min max as follows

Min - 1.9812 + 1.9939 = 3.9751mm
max - 1.9939 2.0066 + 1.9812 = 4.0005mm

then take the measurements from rod 1 with bearing fitted
2.0494" = 52.055mm

minus the shaft size
2.065" = 51.9811mm

Gives a clearance of
.0029" = 0.0737mm

BUT if I take the following

housing size - 56.013mm
Upper Min Wall - 1.9939mm
Lower min Wall - 1.9812mm
Crank - 51.9811mm

I get a theoretical max clearance of 0.0568mm

It's been a long week and I'm jumping in and out of the data, hence why I said maybe I'm missing something, or misunderstanding something?

Sneaky Pete wrote

Its the same feed though?
If you massively increased rod bearing clearance, oil flow through the mains would be reduced or not?

It is the same feed, so increased flow through the rod bearings also means increased flow through the mains

Sneaky Pete wrote

Thats wasn't the suggestion...rather, can increasing the RB clearance have an effect on the flow through the main bearings.

Put it another way if you kept increasing the RB clearance towards infinity would the oil flow through the mains be affected at any time.

I suspect you would see a rod bearing failure first if you kept increasing clearance

PaulGros wrote

It is the same feed, so increased flow through the rod bearings also means increased flow through the mains

I'm not sure thats how fluid dynamics works..but could well be wrong in this case.
Its my understanding that a fluid will always tend to flow fastest through the point of least resistance.
Is it not the case that the oil feed to the mains is the same oil feed to the rod bearings...albeit with the feed arriving at the mains first.
Does the analogy I posted earlier not hold true?
If you have a pressurised pipe with two holes in it, one represents the feed to the mains and the second the feed to the RBs.
If you increase the size of the second hole, fluid will flow faster through the second hole and slower through the first hole all else being equal?

Sneaky Pete wrote

I'm not sure thats how fluid dynamics works..but could well be wrong in this case.
Its my understanding that a fluid will always tend to flow fastest through the point of least resistance.
Is it not the case that the oil feed to the mains is the same oil feed to the rod bearings...albeit with the feed arriving at the mains first.
Does the analogy I posted earlier not hold true?
If you have a pressurised pipe with two holes in it, one represents the feed to the mains and the second the feed to the RBs.
If you increase the size of the second hole, fluid will flow faster through the second hole and slower through the first hole all else being equal?

Not if the rod bearings are fed from the mains. The oil has no way to get to the rod bearings without going via the mains first.

Sneaky Pete wrote

I'm not sure thats how fluid dynamics works..but could well be wrong in this case.
Its my understanding that a fluid will always tend to flow fastest through the point of least resistance.
Is it not the case that the oil feed to the mains is the same oil feed to the rod bearings...albeit with the feed arriving at the mains first.
Does the analogy I posted earlier not hold true?
If you have a pressurised pipe with two holes in it, one represents the feed to the mains and the second the feed to the RBs.
If you increase the size of the second hole, fluid will flow faster through the second hole and slower through the first hole all else being equal?

No. You don't understand fluid dynamics. Q=vA.

Sneaky Pete wrote

If you increase the size of the second hole, fluid will flow faster through the second hole and slower through the first hole all else being equal?

This is incorrect. Assuming constant pressure in your pipe, the mass flow rate must be equal. The mass flow rate of the fluid is function of the velocity and area (size of the hole), when you REDUCE the area of the cross section, the velocity INCREASES, thus maintaining the overall flow rate. This is fundamental fluid mechanics. This is how your garden hose works when you put a nozzle on it, or just your thumb over the end.

PaulGros wrote

I often see the quote about hand measuring into matched sets. But I genuinely don't understand this claim. As far as I am aware you cannot specify the wall thickness you want / require from them. The Wiki data also shows the largest variation in size for them also from all parts measured, double what some brands are achieving. So what is the hand measuring achieving?

I also don't understand why its believed hand measuring is "better". Humans make more mistakes than machines, and laser / optical measuring equipment is more accurate and consistent.

Not had a chance to read later posts yet, but re hand measuring.
IIRC what they do is over stock on the bearings so that they have spare to be able to match and measure, then sell sets of hand measured shells within a very tight tolerance, negating any variances from the factory.
So they have no need to ask the factory for a specified wall thickness.

Re laser measuring, yes but they couldn't afford to bin or hold onto loads of shells could they? I'm sure you mentioned something like that if the tolerances were tightened right up.

Sneaky Pete wrote

I'm not sure thats how fluid dynamics works..but could well be wrong in this case.
Its my understanding that a fluid will always tend to flow fastest through the point of least resistance.
Is it not the case that the oil feed to the mains is the same oil feed to the rod bearings...albeit with the feed arriving at the mains first.
Does the analogy I posted earlier not hold true?
If you have a pressurised pipe with two holes in it, one represents the feed to the mains and the second the feed to the RBs.
If you increase the size of the second hole, fluid will flow faster through the second hole and slower through the first hole all else being equal?

I think where you're getting mixed up Pete is that the RBs and mains are fed in parallel, they're not.
Each main bearing has it's own feed from the main oil gallery, then each main goes onto feed one pair of RBs

This diagram shows what I mean (even though it's not a BMW engine )
http://www.grumpysperformance.com/SBCOilingnew.png

So assuming their was not a variable vol pump, their would be a drop off of mains pressure with larger RB clearances, but nowhere near as much as if they all had individual parallel feeds.

Helmsman wrote

M539 is far from the only source who suggest just that.

Btw bumped into another main fail here, VAC non extended RBs in this case (who later upgraded donor engine with VAC again).

Added to the list, thanks mate.