[bbnks2]

Originally Posted by TZANIDO777

Got it, I figured as much since I have been going through TIS and also didn't see any stretch measurements.

Does anyone like ARP offer rod bolts for the N55 engine?

You don't want to use ARP bolts with stock rods. You want to use stock hardware. There is a discussion on spool street about it. There is no evidence that stock bolts are not sufficient but there is evidence that ARP hardware can distort stock rod bores.

Also edited my previous post for N55 relevant specs. I thought this was the N52 rebuild thread lmao.

[feuer]

Originally Posted by bbnks2

BMW does not publish stretch measurements to go off of, but yes, that is usually more accurate than relying on a predetermined angle. My aftermarket rods supplied the proper stretch, but, they also supplied an alternative means of torque+angle.

https://www.newtis.info/tisv2/a/en/e...rings/8GvWX6fP

Proper torque specs are 20nm then 70* + another 70* (replace, wash, and oil). I am sure there is a special oil BMW wants you to coat them in that you should be bale to find on TIS. Friction is super important to get the correct stretch.

So Bentley and this: https://workshop-manuals.com/bmw/3_s..._and_bearings/ aren't correct?

[hassmaschine]

Originally Posted by feuer

So Bentley and this: https://workshop-manuals.com/bmw/3_s..._and_bearings/ aren't correct?

That's just the spec. The procedure probably tells you to use that angle twice.

Bentley has a history of typos and inaccuracies.. so I'd take them with a grain of salt.

[feuer]

Originally Posted by hassmaschine

That's just the spec. The procedure probably tells you to use that angle twice.

Bentley has a history of typos and inaccuracies.. so I'd take them with a grain of salt.

Main bearing bolts are longer and require 20mn + 70'. Longer bolts require larger angle to tighten as shorter bolt. m10x100 vs m9x47. So I don't think this 70' + 70' is accurate as that bolt will probably break off. Take the oil pan and oil pump bolts for compassion: short ask for 90' and longer for 180'

[fatty335]

Well hmmm... I was certainly hoping for a little more consensus with this most critical torque setting/procedure. The scant, openly-available information does seem to be contradictory. If I paid the $30 for a 24-hour subscription to bmwTIS, do you think it would contain the definitive answer on this? Additionally, I have an email out to both Ghassan and ABR asking what procedure they use - I'll report back.

[feuer]

I have worked on two messed up engines that were "rebuild" by Ghassan. I have used 10nm then 20nm then single 70'. I have done similar on other BMW engines, like the older M 6-cyl engines, 5nm then 30nm then single 70' and those use m11 bolts.

[bbnks2]

Originally Posted by feuer

Main bearing bolts are longer and require 20mn + 70'. Longer bolts require larger angle to tighten as shorter bolt. m10x100 vs m9x47. So I don't think this 70' + 70' is accurate as that bolt will probably break off. Take the oil pan and oil pump bolts for compassion: short ask for 90' and longer for 180'

Originally Posted by feuer

I have worked on two messed up engines that were "rebuild" by Ghassan. I have used 10nm then 20nm then single 70'. I have done similar on other BMW engines, like the older M 6-cyl engines, 5nm then 30nm then single 70' and those use m11 bolts.

Ok, I get what you're saying, but, you're speaking from a place of pure conjecture...

I would put any amount of money on it that rod bolts see higher loads, and require greater clamping force, then the main studs do. Therefore, I can also infer that rod bolts require more stretch to achieve a greater clamping force. That is how stretch bolts work.

Also, there is no comparison to the oil pan bolts. Rod bolts are not aluminum which has a completely different elasticity and fatigue. Rod bolts and bed-plate bolts are steel lol.

Also, look at the M9x170 cylinder head bolts... they require 30Nm and 90* + 180*. Yes it's a longer bolts, but it is also getting significantly more stretch than the main bolts which are M10x100 and only require 20Nm +70*.

None of this helps answer the question of what is the correct torque, but, I have to post this to point out the flaws in your argument. I am grateful I was using aftermarket rods with ARP specific fastening requirements LOL I will say that Molnar called for 30ft lbs (NOT Nm) + 65* which is actually probably very close to the same total degrees of rotation as a stock bolt needing 20Nm (15ft lbs) + 70+70*. 15ft lbs vs 30 ft lbs can easily be 70* of rotation lol... different hardware altogether but it gives an additional perspective.

I also can't find and formulas that consider the length of a bolt as having a meaningful impact on desired clamping force. I see things like diameter, desired tensile load, target torque, and most importantly coefficient of friction (which is why lubing these bolts is very important). Length is obviously a part of the more complicated formulas but it's left out of most of the basic ones...

Hopefully OP gets a definitive answer.

[TheMidnightNarwhal]

Originally Posted by hassmaschine

That's just the spec. The procedure probably tells you to use that angle twice.

Bentley has a history of typos and inaccuracies.. so I'd take them with a grain of salt.

For sue TIS vs Bentley TIS should be the most reliable source IMO. It's directly from the BMW work manuals.

[TheMidnightNarwhal]

Originally Posted by fatty335

Well hmmm... I was certainly hoping for a little more consensus with this most critical torque setting/procedure. The scant, openly-available information does seem to be contradictory. If I paid the $30 for a 24-hour subscription to bmwTIS, do you think it would contain the definitive answer on this? Additionally, I have an email out to both Ghassan and ABR asking what procedure they use - I'll report back.

Yeah that would be a worthwhile 30$.

But I'm not sure if the paid tis has more info you can get than https://newtis.info .

[9krpmrx8]

Originally Posted by feuer

I have worked on two messed up engines that were "rebuild" by Ghassan. I have used 10nm then 20nm then single 70'. I have done similar on other BMW engines, like the older M 6-cyl engines, 5nm then 30nm then single 70' and those use m11 bolts.

What was messed up or not "rebuilt" on these two engines?

[bbnks2]

Sorry Fuer, but I think there are some incorrect docs (like the one you linked) floating around causing confusion and you've been torquing rods incorrectly.

The new G30 B58 also calls for 20Nm + 70 + 70*
https://www.newtis.info/tisv2/a/en/g...ngs/1VnYvrkU0K

65 M3 is an M9 bolt and gets 6Nm + 20Nm + 130*
https://www.newtis.info/tisv2/a/en/e...arings/5rZSb5m

Seems in-line with N5x requiring 20NM + 70 + 70*.

[9krpmrx8]

Typical.

[feuer]

Originally Posted by 9krpmrx8

What was messed up or not "rebuilt" on these two engines?

They weren't rebuilt to begin with.

[fatty335]

*UPDATE: Ghassan has replied to my inquiry (thanks guys!) and confirmed that they use the, "wash and oil new bolts, 20Nm, 70 degrees, and then 70 degrees again for all rod bolts" procedure on the N55. This jives with newTIS and it seems this is more likely correct than just doing 70 degrees once. I still plan to pay and check out what bmwTIS says unless someone can confirm it is identical to newTIS. Thanks for all the discourse everyone...this is helpful.

[vespa]

It's worth noting that BMW added a plastic liner (#11 in red) to the upper half of the rod bearings in the next generation (B58) of this engine. The documentation states that this was necessary due to the increased number of starts these engines are expected to see with the auto start/stop feature (though many N55's also use this feature). I suspect the real story is that they wanted to move to 0W-20 (LL14) oil for fuel savings and saw from the N55 failures that the bearings were already going dry even with the old 5W-30 oil.

Hey fatso, one thing that would be pretty interesting to us all "in the name of science" would be to plastigauge your old bearings first. If you find a clearance out of spec it would suggest that the bearings wear with age, presumably to the point of excess/failure. But if there is no measurable wear it might suggest that the issue is due to oiling problems such as debris from an OFHG replacement.

[bbnks2]

Originally Posted by vespa

I suspect the real story is that they wanted to move to 0W-20 (LL14) oil for fuel savings and saw from the N55 failures that the bearings were already going dry even with the old 5W-30 oil.

#11 is the bearing shell. The upper (rod side) shells are coated with IROX. It's just another brand of bearing coating like Calico.

It's for start/stop wear and tear. Has nothing to do with wanting to run thinner oil or N55 specific "failure rates." The main benefit is anti-friction properties which reduce parasitic drag and increase mechanical efficiency. Coated bearings don't allow you to run thinner oil but they are used to produce the same type of efficiency improvement as thinner oil (less friction and more power/efficiency). The smoothness and friction properties of the bearing surface is also directly proportional to how effective the oil film is. A rough bearing finish, or a bearing finish which isn't slick, produces a boundary layer of flow and what KING and other bearing manufacturers describe as "mixed lubrication regime." So in that case, yes, with coated bearings you probably can run thinner oil and get the SAME protection with it since the oil film effectiveness is improved due to the coatings anti-friction properties and improved laminar flow of oil through the journal.

http://kingbearings.com/wp-content/u...ofessional.pdf

Bearing coatings like IROX and Calico certainly don't hurt when you have potential intermittent oiling issues (like start/stop, high load, oil starvation, etc.) either. These coatings increase the hardness and anti-seizure properties of the bearings as well as the efficiencies noted above. Cold start wear protection seems to be BMWs main concern.

http://www.federalmogul.com/en-US/OE...&ProductId=226

BMW points out themselves that they've seen increased bearing wear due to thinner oil films (tighter tolerances) upon startup. Not because thinner modern synthetic oil itself is less robust at handling load during operation (this is more a function of oil pressure). This is what I had speculated causes wear in S65/S85/N5x and all the other modern tight tolerance engines from all manufacturers. These guys pulled bearings out of daily driven S65 engines and found wear. The conclusion was that there is a bearing issue and/or some kind of rod deformity. In reality, it just looks like normal wear and tear you will find on any high mileage motor. Problem is these bearings were out of BMW engines with ~100k or less on them. It's an industry wide phenomenon not some BMW engine manufacturing defect.

BMW seems to be confirming that cold starts produce wear over time and tighter tolerance and increase start/stop cycles have accelerated that wear. Oil pressure during operating prevents metal/metal contact. On a cold start you don't have that oil pressure and you have less oil clinging to the bearing surface = increased cold start wear. Thin oil itself helps deliver oil to the bearing faster and bring up oil pressure faster upon cold starts.

"Iftheengineisnowstopped,itwillnotbepossibleforthe mechanically-drivenoilpumptomaintain
theoilsupply.Theoilfilmbetweenthebearingpositionsf lowsoff.Solidbodycontactoccursbetween
theconnectingrodbearingjournalandconnectingrodbear ingshell.Oncetheengineisrestarted,it
takesacertainamountoftimeforthelubricatingfilmtofu llyre-establishitself.Theconnectingrod
bearingshellmaybesubjecttowearinthisshortperiod.Th eIROXcoatingreducesthisweartoa
minimum."

Page 19: https://www.1erforum.de/attachments/...ine-pdf.84135/

TheIROXcoatingisappliedtoaconventionalbearingshell .Itconsistsofabindingresinmatrixmade
ofpolyamide-imidewithembeddedhardparticlesandsolidlubricants.T hepolyamide-imideensures,
incombinationwiththehardparticles,thatthebearingsh ellsurfaceissohardthatmaterialabrasion
isnolongerpossible.Thesolidlubricantsreducesurface frictionandreplacetheoilfilmwhichbriefly
nolongerexistsbetweenthebearingshellandtheconnecti ngrodbearingjournalduringthestarting
phase.

I now have an Accusump installed with an electric pressure switch, and I use it to prime the engine with oil pressure prior to cranking.

[fatty335]

*UPDATE: Everything has arrived and, with the upcoming holiday weekend, I plan to begin this job on Saturday. I'll post pics of my progresses. One final thought I had: is there a standard procedure to prime the engine before the first start after completely emptying the oil (such as after a pan gasket change), or is it just fill it up and fire away?

Originally Posted by vespa

Hey fatso, one thing that would be pretty interesting to us all "in the name of science" would be to plastigauge your old bearings first. If you find a clearance out of spec it would suggest that the bearings wear with age, presumably to the point of excess/failure. But if there is no measurable wear it might suggest that the issue is due to oiling problems such as debris from an OFHG replacement.

Vespa - since platigage is so imprecise (and really only meant to be a sanity check), I'm afraid it wouldn't do a very good job of determining the info you seek - one would really need to mic the diameters of the assembled and torqued rods and old bearing shells to determine wear.

[bbnks2]

Originally Posted by fatty335

is there a standard procedure to prime the engine before the first start after completely emptying the oil (such as after a pan gasket change), or is it just fill it up and fire away?

Oil will not fully drain from the oil pump. If this were the case you would have to prime the engine before EVERY start. It won't hurt to pour some oil down into the oil filter housing when you're done though. Assembly lube will cling to bearing for that first start.

Originally Posted by fatty335

Vespa - since platigage is so imprecise (and really only meant to be a sanity check), I'm afraid it wouldn't do a very good job of determining the info you seek - one would really need to mic the diameters of the assembled and torqued rods and old bearing shells to determine wear.

Any wear you would be concerned about would be readily visible i'd think.

[TheMidnightNarwhal]

Originally Posted by fatty335

*UPDATE: Everything has arrived and, with the upcoming holiday weekend, I plan to begin this job on Saturday. I'll post pics of my progresses. One final thought I had: is there a standard procedure to prime the engine before the first start after completely emptying the oil (such as after a pan gasket change), or is it just fill it up and fire away?



Vespa - since platigage is so imprecise (and really only meant to be a sanity check), I'm afraid it wouldn't do a very good job of determining the info you seek - one would really need to mic the diameters of the assembled and torqued rods and old bearing shells to determine wear.

Good oil

[feuer]

You could remove the fuel pump fuse and crank the engine.

[fatty335]

Originally Posted by feuer

You could remove the fuel pump fuse and crank the engine.

Thanks, feuer - from my reading, disconnecting the fuel injectors & cranking to build pressure seems to be the preferred method and is likely what I'll do. I do recall reading about an SIB that discussed priming the engine after completing oil system repairs but I've never actually seen it - does this sound familiar to anyone?

[feuer]

Originally Posted by fatty335

Thanks, feuer - from my reading, disconnecting the fuel injectors & cranking to build pressure seems to be the preferred method and is likely what I'll do. I do recall reading about an SIB that discussed priming the engine after completing oil system repairs but I've never actually seen it - does this sound familiar to anyone?

The oil pump hold oil. When you remove it you will see. Oil will drain from the pump as well from the oil passages upon removal. So is better to add oil through the OFH so there will be oil there when you first crank the engine. Oil pump is able to move a lot of oil very fast. Even if you don't do knowing of this it will be OK as long as you put assembly lube on the bearings.