Lang Racing on the S54 Rod Bearing problems

[regular guy]

Originally Posted by aussiem3

I was told today that the bearing clearance in the /// engines are no different to other BMW production engines. Hope someone here can clarify/confirm or dispute this claim. Australia is not treating this as an issue and they are surprised with what's going on in NA.

I have the technical data on clearances of many dozens of BMW engines in a factory DVD. Within five minutes, I looked at two engines, and both were different than each other. I will collect ten different engines and post the results in the bearing cleaerance thread. I think this proves my point that whoever you are talking to isn't very well informed and doesn't have very much technical data. So with that, I would tend to discount just about everything else they said as well. I will post in a few hours over in the other thread.

[swamp2]

Originally Posted by aussiem3

The clearance issues was asked from the BMW trainers in Australia during a M specific workshop that took place last week. I got one of the senior techs who attended this to ask this question.

As far as BMW Australia is concerned there is no issue. They will not even entertain a discussion because "there is no problem". Period.

To be fair, engineer, field rep, marketing or sales, corporate or country based folks, all MUST "tow the company line" and will not discuss or admit any POTENTIAL design issues. They are all bound by their legal folks. There are HUGE financial implications in admitting design problems (i.e. cost of recall). Thus in short they may or may not actually believe what they say. They do also sound ignorant as pointed out just above...

[regular guy]

Originally Posted by aussiem3

I was told today that the bearing clearance in the /// engines are no different to other BMW production engines. Hope someone here can clarify/confirm or dispute this claim. Australia is not treating this as an issue and they are surprised with what's going on in NA.

I just posted a list of twelve different BMW engines with their clearance specifications. The data leaves no doubt that your Australian BMW "experts" are not giving you accurate information (or anything close to it). Another thing to notice is how the S65 sticks out in that list like a sore thumb when you compare it to other BMW engines from all era's.

http://www.m3post.com/forums/showpos...&postcount=365

[aussiem3]

Originally Posted by regular guy

I just posted a list of twelve different BMW engines with their clearance specifications. The data leaves no doubt that your Australian BMW "experts" are not giving you accurate information (or anything close to it). Another thing to notice is how the S65 sticks out in that list like a sore thumb when you compare it to other BMW engines from all era's.

http://www.m3post.com/forums/showpos...&postcount=365

I am no expert and only contributing to help what is an already healthy discussion.

It's great to see following my post that some numbers have come out to support what you have been saying all along.

[LangRacingDevelopment]

Originally Posted by swamp2

Wow, speculation and hypothesizing galore. Really, no disrespect here, we'd all just love to see the evidence. Since you've (Lang Racing) have done such a plethora of S54 rebuilds can you post some before and after evidence demonstrating your set of corrections to be definitively successful? Personally, I (and I'm sure the rest of the community here) would like to see results from multiple engines that had either massive bearing wear or a catastrophic failure at low miles, had your groups of fixes performed and then lasted a considerably longer time AND had a follow up bearing inspection to establish some level of proof of success.




Precisely... as I've already repeated multiple times. Come on, would taking a bearing clearance from .001 to .002 massively improve long term reliability, perhaps make little or no additional NVH, loose an insignificant amount of power, cost essentially nothing and have been COMPLETELY overlooked by a time and time again International Engine of the Year award winning engine OEM...



Bravo!

But then again isn't this a huge contradiction to more or less the exact approach you have taken with the S54?

There seems to be a lot of people here believing that I am a proponent of something which I am not. I have done no work yet on the S65 rod bearing, just paid attention to what's going on. What I believe is an improvement on the S54 should have no bearing on what I think would be an improvement on the S65. Why would anyone compare an inline 6 to a V8? One rod on a journal vs 2 rods on a journal and a whole lot of other differences that would make a comparison irrelevant.

The main reason for widening the rod bearing journal on an S54 is to kill two birds with one stone. Keep a customer with a spun bearing motor from having to shell out money for a new crankshaft, and to give them an economical opportunity to use better than OEM aftermarket components that potentially increase the reliability of the engine.

The truth is that most people don't want to spend the money on S54 rebuilds when used engines are available so cheap. So there aren't that many of my kits out there. I spend a lot more of my time replacing rod bearings before they've spun on S54's than I do rebuilding them after they've spun. From that experience I have seen that even people who take care of their engines seem to be experiencing rod bearing wear that's higher than most engines out there.

I don't tear apart S65's on a regular basis to check bearing wear, but I wouldn't be surprised to find higher than average bearing wear. From the photos I've seen online it seems like the relatively low bearing clearance causes the rod bearing to wear out over a larger surface area. Based on no research at all I would wonder if the tighter bearing clearance was a strategy BMW used to increase bearing service life. Perhaps they decided it is inevitable that bearing to crank journal contact will occur and increasing the surface area of that contact would lead to longer bearing life. S54 bearing clearances comparably loose and the bearing wear reflects that. Loose clearances didn't seem to do that well on the S54 so maybe BMW decided to try a different approach. This is pure speculation and no evidence at all.

My idea on the S54 doesn't seem radical and has been done by many other people on different types of engines that have rod bearing wear issues. Widen the bearing, increase rod bearing surface area to increase film strength. I'd love to have proof from 100 engines that I've built with this modification that have run 100k miles but... there aren't many out there and nobody drives there car that many miles per year so I think it will be a while before I have "real proof".

What everyone seems to think is a good idea on the S65 is to increase rod bearing clearance to what is just a normal engine level. Seems like a safe bet, assuming tightness of that clearance is your only issue. Increasing bearing clearance increases the oil volume between the journal and the bearing but doesn't increase rod bearing surface area. You can't easily widen the rod bearing on the S65, no room to do so, so it isn't an option.

If I was running an S65 I would do the same thing I would do on every other high revving BMW motor like the S14 and S54, replace the rod bearings every 50k miles or every 30 hours on a race engine. It's not that hard or expensive and it seems to make all these engines last a very long time.

I'm sure that the V8 M3 guys will start doing that when their cars are no longer covered by warranty and they don't get free engine replacements under warranty.

Hopefully this clears something up about what people seem to think that I believe about this issue.

[Patrón]

Great info Drew.

[Beedub]

great read LangDevel....

[coloradoe92m3]

Hmm m engineers purposely making bearings tighter to improve wear! Frankly I wouldn't be surprised that has a lot of truth. I think the bigger flaw is for all of us to expect an engine like this which is literally used in BMW race cars, to last 100 plus miles. Perhaps we need to accept if we want an 8500 rpm v8 with 105 HP/l we tradeoff longevity and maybe looser bearings would have put more stress on smaller portions of each bearing rather than spreading force out more uniformly and things would be failing more drastically. Who knows, I think we need to be open to all ideas

[Petros]

Originally Posted by coloradoe92m3

Hmm m engineers purposely making bearings tighter to improve wear! Frankly I wouldn't be surprised that has a lot of truth. I think the bigger flaw is for all of us to expect an engine like this which is literally used in BMW race cars, to last 100 plus miles. Perhaps we need to accept if we want an 8500 rpm v8 with 105 HP/l we tradeoff longevity and maybe looser bearings would have put more stress on smaller portions of each bearing rather than spreading force out more uniformly and things would be failing more drastically. Who knows, I think we need to be open to all ideas

Plenty of cars that can spank an M3 that don't seem to have bearing problems. Just sayin *cough*GTR/Vette/Mustang/911/Viper*cough*

[chris719]

Originally Posted by coloradoe92m3

Hmm m engineers purposely making bearings tighter to improve wear! Frankly I wouldn't be surprised that has a lot of truth. I think the bigger flaw is for all of us to expect an engine like this which is literally used in BMW race cars, to last 100 plus miles. Perhaps we need to accept if we want an 8500 rpm v8 with 105 HP/l we tradeoff longevity and maybe looser bearings would have put more stress on smaller portions of each bearing rather than spreading force out more uniformly and things would be failing more drastically. Who knows, I think we need to be open to all ideas

Porsche hasn't had these issues with the Mezger engines in the 997 GT3s which revs even higher and has higher specific output. The S65 is designed to a price point and this may be where BMW has saved some money.

[coloradoe92m3]

Originally Posted by chris719

Porsche hasn't had these issues with the Mezger engines in the 997 GT3s which revs even higher and has higher specific output. The S65 is designed to a price point and this may be where BMW has saved some money.

The Porsche is a flat 6 which is a totally different animal. Vetted is low revving pushrod v8, gtr is v6 turbo low revving car. Only direct comparison is Ferrari but the number of Ferraris sold and the number that actually used any real miles is so small that its a meaningless sample but Id bet anything Ferrari v8 engines have even tighter clearances

[regular guy]

Originally Posted by coloradoe92m3

The Porsche is a flat 6 which is a totally different animal. Vetted is low revving pushrod v8, gtr is v6 turbo low revving car. Only direct comparison is Ferrari but the number of Ferraris sold and the number that actually used any real miles is so small that its a meaningless sample but Id bet anything Ferrari v8 engines have even tighter clearances

Go check the bearing clearance wiki. We have the specs for one Ferrari. There may be a second one somewhere in the thread. The Ferrari was not tighter. The rod clearances per journal-inch diameter were nearly double the S65.

[swamp2]

Originally Posted by regular guy

Go check the bearing clearance wiki. We have the specs for one Ferrari. There may be a second one somewhere in the thread. The Ferrari was not tighter. The rod clearances per journal-inch diameter were nearly double the S65.

Yes, but...

1. That is for rod bearings only. Mains are identically speced in inch/inch.
2. It is also a bit apples to oranges since the 328 in the comparison is from 1986. It would obviously be good to have some more modern data for a Ferrari.

[coloradoe92m3]

Originally Posted by swamp2

Yes, but...

1. That is for rod bearings only. Mains are identically speced in inch/inch.
2. It is also a bit apples to oranges since the 328 in the comparison is from 1986. It would obviously be good to have some more modern data for a Ferrari.

Exactly, BMW in 86 didn't have a bearing "problem" but rather with higher and higher output in a NA high revving v8 begins to create unique forces that makes a ton of sense to need to spread the load out with tighter specs. Of all threasons thrown out like making engine quieter, making more power etc, I think this thought is much more plausible given multiple generations of tight specs. I find that a bit more likely than BMW being dense for 3 engines in 10 years

[BMRLVR]

Originally Posted by coloradoe92m3

The Porsche is a flat 6 which is a totally different animal. Vetted is low revving pushrod v8, gtr is v6 turbo low revving car. Only direct comparison is Ferrari but the number of Ferraris sold and the number that actually used any real miles is so small that its a meaningless sample but Id bet anything Ferrari v8 engines have even tighter clearances

Flat six, inline six, V8, V6, V10 matters not to rod bearings, the ultimate thing to realize is that mean effective pressure is mean effective pressure and piston speed is piston speed. Different engine configurations deal with harmonics and are balanced much better than others but this has very little effect on rod bearing wear.

The horsepower an engine makes divided by the number of cylinders tells you your horsepower per cylinder...... the Porsche Mezger engine in its ultimate N/A form made 500 HP from 4 litres with two fewer cylinders than the S65 and with a higher redline....... No matter how you slice it the loads placed on the bearings of the mezger engine were significantly higher as were piston speeds.

A very good example of an extremely similar engine to the S65 is the V8 in the R8/RS4/RS5. Similar output, 420-450 HP depending on the application, same redline (8400 in the B8 RS4/RS5), A little more torque than the S65 (317 Lb/Ft) which means higher Brake Mean Effective Pressure, and a little more compression (12.5-1)..... Now look at the dimensions of that engine: 84.5 mm bore and 92.8 mm stroke....... A way longer stroke than even the most extreme S65 stroker right out of the box. This means the Audi V8 engine has way more piston speed than the S65 which means the rod bearings of that engine are experiencing significantly higher loads than the S65, but strangely enough there are next to no reports of rod bearing issues (Lots of Carbon issues but no rod bearing issues). Also of note the Audi engine does all of this using 5W40 in the sump....... No exotic 10W60 in the sump. The Clearance specifications as per Audi for a new rod bearing on all of the 4.2 V8's is 0.028-0.077mm (0.001-0.003").

By the Way, the LS7 V8 in a corvette is hardly low revving, it spins 7000RPM and has a 101.6 mm stroke. Hardly anything to sneeze at.

[coloradoe92m3]

Good call on Audi however seems to never put put near stated power but that's prob quattro drive train loss

[swamp2]

Originally Posted by BMRLVR

Flat six, inline six, V8, V6, V10 matters not to rod bearings, the ultimate thing to realize is that mean effective pressure is mean effective pressure and piston speed is piston speed. Different engine configurations deal with harmonics and are balanced much better than others but this has very little effect on rod bearing wear.

Not quite, what determines (peak) bearing loads is the peak cylinder combustion pressure and piston acceleration, not piston speed. One governs peaks on one side of the bearing and the other on the other side.

Originally Posted by BMRLVR

The horsepower an engine makes divided by the number of cylinders tells you your horsepower per cylinder...... the Porsche Mezger engine in its ultimate N/A form made 500 HP from 4 litres with two fewer cylinders than the S65 and with a higher redline....... No matter how you slice it the loads placed on the bearings of the mezger engine were significantly higher as were piston speeds.

May be true but again not the right way to analyze this.

Originally Posted by BMRLVR

A very good example of an extremely similar engine to the S65 is the V8 in the R8/RS4/RS5. Similar output, 420-450 HP depending on the application, same redline (8400 in the B8 RS4/RS5), A little more torque than the S65 (317 Lb/Ft) which means higher Brake Mean Effective Pressure, and a little more compression (12.5-1)..... Now look at the dimensions of that engine: 84.5 mm bore and 92.8 mm stroke....... A way longer stroke than even the most extreme S65 stroker right out of the box. This means the Audi V8 engine has way more piston speed than the S65 which means the rod bearings of that engine are experiencing significantly higher loads than the S65, but strangely enough there are next to no reports of rod bearing issues (Lots of Carbon issues but no rod bearing issues). Also of note the Audi engine does all of this using 5W40 in the sump....... No exotic 10W60 in the sump.

Again just for the inertial terms, likley dominant at high rpm it it more accurate to compare rpm^2 x stroke. Next the B8 redlines at 8200 rpm. Even using these corrections you happen to be right (for the wrong reasons) that the inertial loading is higher in theRS4 B8. But finally, bearing widths will be a factor in the actual pressure generated.

Originally Posted by BMRLVR

The Clearance specifications as per Audi for a new rod bearing on all of the 4.2 V8's is 0.028-0.077mm (0.001-0.003").

Please share your source and provide meaningful (scaled in/in) results. Both the size and spread on these results sound a bit too large.

[BMRLVR]

Originally Posted by swamp2

Not quite, what determines (peak) bearing loads is the peak cylinder combustion pressure and piston acceleration, not piston speed. One governs peaks on one side of the bearing and the other on the other side.

May be true but again not the right way to analyze this.

Again just for the inertial terms, likley dominant at high rpm it it more accurate to compare rpm^2 x stroke. Next the B8 redlines at 8200 rpm. Even using these corrections you happen to be right (for the wrong reasons) that the inertial loading is higher in theRS4 B8. But finally, bearing widths will be a factor in the actual pressure generated.

Please share your source and provide meaningful (scaled in/in) results. Both the size and spread on these results sound a bit too large.

Official numbers from Audi! I have a contact at an Audi dealer since my brother used to be a service manager at a VW Audi dealer and he owns an RS4.

By the way, Mean Effective Pressure is the average cylinder pressure of a combustion cycle. Brake Mean Effective Pressure occurs at an engines torque peak and is higher for the Audi V8 since it's peak torque is higher than the S65!

[BMRLVR]

Just something further to my last post, the S65 has a 140.72mm rod and 75.2mm stroke for a R/S ratio of 1.87-1 while the Audi has a 154mm rod and 92.8mm stroke for a R/S ratio of 1.66-1.

Since the Audi V8 has an even less favourable R/S ratio than the S65 it has both higher mean piston speed and much higher piston acceleration. This confirms even higher bearing loads than the S65 while running looser clearances and lighter oil as well as a compression ratio 0.5 points higher than the S65.

[swamp2]

Originally Posted by BMRLVR

Just something further to my last post, the S65 has a 140.72mm rod and 75.2mm stroke for a R/S ratio of 1.87-1 while the Audi has a 154mm rod and 92.8mm stroke for a R/S ratio of 1.66-1.

Since the Audi V8 has an even less favourable R/S ratio than the S65 it has both higher mean piston speed and much higher piston acceleration. This confirms even higher bearing loads than the S65 while running looser clearances and lighter oil as well as a compression ratio 0.5 points higher than the S65.

As pointed out earlier neither thing you list determines the bearing loads. Absolutely not. Inertial loads are determined (to first order approximation) by the product of stroke and rpm^2 (technically stroke/2, but for comparing a ratio that is not important). That technically is only the acceleration. Inertial force is then piston mass x acceleration. Last but not least this assumes that one is in an rpm range where inertial loads > combustion load. This also really only gives the force at the wrist pin since rod mass isn't included.

[BMRLVR]

Originally Posted by swamp2

As pointed out earlier neither thing you list determines the bearing loads. Absolutely not. Inertial loads are determined (to first order approximation) by the product of stroke and rpm^2 (technically stroke/2, but for comparing a ratio that is not important). That technically is only the acceleration. Inertial force is then piston mass x acceleration. Last but not least this assumes that one is in an rpm range where inertial loads > combustion load. This also really only gives the force at the wrist pin since rod mass isn't included.

Funny thing, every thing that someone mentions is not correct. What determines bearing loads than? Please do tell, I am sick of your smoke and mirrors.......

[coloradoe92m3]

Well said swamp. None of numbers people throwing out have any relevance to bearing load and thus using them as argument is irrelevent