BMW M5 Forum and M6 Forums banner
1 - 20 of 33 Posts

·
Registered
Joined
·
1,536 Posts
is the crankshaft straight?

is the flange that carries the flywheel square to crankshaft?

It may be normal wear due to design deficiencies of the s85 crankshaft in resisting flexing of crankshaft under S6 torque impulses.
 

·
Banned
Joined
·
1,396 Posts
Interesting. We do know that BMW used very tight tolerances in their bearing clearances, however we seldom see the crank mains because the engines are so infrequently disassembled. I have seen some similar accounts on one the M3 boards discussing the S65 where someone had issues with their worn mains. I think I asked about this once here but Troy and Jim are no longer here and they are the ones who have seen the most engines gutted. Unlike rod bearings, BMW did have 3 sizes at the factory to chose from and that is etched on the crank and engraved on the block. You should see what code that represents and also measure the clearance yourself since you have the crank and bearings still.
 

·
Premium Member
E60 M5 and building engines
Joined
·
208 Posts
Discussion Starter · #6 ·
is the crankshaft straight?

is the flange that carries the flywheel square to crankshaft?

It may be normal wear due to design deficiencies of the s85 crankshaft in resisting flexing of crankshaft under S6 torque impulses.
Crank currently being Magnafluxed at machine shop for concern of rod journal two heat witness marks. Should have full review within two days and will post results.

Does signs of corrosion. It is main #6 so out of balance flywheel/clutch assembly could had added extra stress?

Will order matched bearings (full set) and measure b/4 assembly of engine.

Mr. P
 

Attachments

·
Premium Member
E60 M5 and building engines
Joined
·
208 Posts
Discussion Starter · #7 ·
Sorry: Does NOT show signs of corrosion.

Interested in learning more about S6 torque impulses. Any recommended links?
 

·
Registered
Joined
·
1,536 Posts
Sorry: Does NOT show signs of corrosion.

Interested in learning more about S6 torque impulses. Any recommended links?
That was just a top of the head thought, from 2 years of McMaster University Engineering prior to switching to Geophysics.

There is a statistical power point presentation via a BMW pdf on line that suggests crank design was validated via statistical finite element analysis

I believe the usual iterative expensive destructive testing was bypassed for what BMW initially perceived to be a one off small volume offering.

The inertial Potential energy at 8000 rpm transferred on crankshaft flange in the form of an impulse during an s6 shift would be a significant load additive to the 383 lbft of torque resisted by crank journal at #6 main location could result in sufficient crank deflection to have crank journal to bearing contact.

All just a hypothesis at this point
 

·
Registered
Joined
·
1,536 Posts
Back in 2014 Troy shared a lot of his observations of many s85 engines He was taking apart .
Based on his observations I decided a 6.0 stroker would hold up best on track.

Simply I anticipated the billet crank, and rods, along with forged pistons and steel liners would avoid a lot of issues Troy discovered.
Thus my post in this thread have a strong bias not based on irrefutable facts
 

·
Premium Member
E60 M5 and building engines
Joined
·
208 Posts
Discussion Starter · #10 ·
That was just a top of the head thought, from 2 years of McMaster University Engineering prior to switching to Geophysics.

There is a statistical power point presentation via a BMW pdf on line that suggests crank design was validated via statistical finite element analysis

I believe the usual iterative expensive destructive testing was bypassed for what BMW initially perceived to be a one off small volume offering.

The inertial Potential energy at 8000 rpm transferred on crankshaft flange in the form of an impulse during an s6 shift would be a significant load additive to the 383 lbft of torque resisted by crank journal at #6 main location could result in sufficient crank deflection to have crank journal to bearing contact.

All just a hypothesis at this point
Hello ticat928,

I LOVE computers and simulations. While working with Nissan, got to learn a lot about stamping, castings, and continue with injection molding and extrusions. Worked with a great die design team that could simulate metals stress and pull/weak points on a CAD model! This enabled us to offer suggestions to designers on die change that did not affect part fit in vehicle and produce a better part!

Will look for BMW paper on crank!

Thank you,

Mr. P
 

·
Registered
Joined
·
1,536 Posts
I could not find it on line any more

will look at my laptop I used in 2015
Or my early post, there was a discussion on it
 

·
Registered
Joined
·
630 Posts
If it's #1 (front) main, and on upper shell it's nearly certainly due to belt tension/startup wear.

Driveline induced torque would probably be at ~30Hz input, whereas the crank natural frequency is probably on the order of 500Hz. Cranks are nearly certainly made by Alfing and are presumably salt bath nitrocarburized.

It could be corrosion due to someone getting zippy with moly content in oils (either via additive or oil formulation). This will also remove DLC on parts that are coated as such, due to typical attendant sulphur compounds with moly additives.

If there's a BMW paper on the S85 or S65 crank, please point me to it!
 

·
Premium Member
E60 M5 and building engines
Joined
·
208 Posts
Discussion Starter · #13 ·
If it's #1 (front) main, and on upper shell it's nearly certainly due to belt tension/startup wear.
Hello desmo01

No belt. Chain. No6 @ flywheel. Lower/girdle. Also small sighs of wear on No5 and less on No4 mains, again on girdle/lower.

Mr. P
 

·
Premium Member
E60 M5 and building engines
Joined
·
208 Posts
Discussion Starter · #14 ·
is the crankshaft straight?

is the flange that carries the flywheel square to crankshaft?

It may be normal wear due to design deficiencies of the s85 crankshaft in resisting flexing of crankshaft under S6 torque impulses.
Recently received information that this crankshaft (engine #2) is not perfectly strait.

It has been sent out for correction ,but reason is unknown and was reported as only "slightly out". BMW's are famous for VERY strong high quality OEM cranks.

Will have more info when crank has been repaired.

Mr. P
 

·
Registered
Joined
·
1,536 Posts
Recently received information that this crankshaft (engine #2) is not perfectly strait.

It has been sent out for correction ,but reason is unknown and was reported as only "slightly out". BMW's are famous for VERY strong high quality OEM cranks.

Will have more info when crank has been repaired.

Mr. P
Sorry I have not found the pdf, I posted the s85 crankshaft study back in 2015 for some reason cannot go back that far with my posts, the laptop I downloaded it on is dead, it is from 2002 does not start even plugged in, I think battery has aged out and has infinite resistance

I think Jim Colley was the first one to post the link, but I knew it was not going to be up forever
 

·
Premium Member
2017 BMW X5M Dinan Stage 1
Joined
·
550 Posts
HOLY CRAPOLA...WHAT ARE YOU GUYS TALKING ABOUT? So the crank case/girdle/main/ooga booga can show signs of damage because of the bearings? My limited experience with the S85 aside....this is the first I'm learning about this.

Ahhhh...screw it. If I blow my engine....I'll just buy a new one and tell the new one what a wuss the old one was.

949637
 

·
Registered
Joined
·
532 Posts
HOLY CRAPOLA...WHAT ARE YOU GUYS TALKING ABOUT? So the crank case/girdle/main/ooga booga can show signs of damage because of the bearings? My limited experience with the S85 aside....this is the first I'm learning about this.
Seems like it. Main bearing failures have been reported on our sister engine the S65 but it hasn't seem to come up with the S85. I believe P-Chi's is due to crank run out though
 

·
Premium Member
2017 BMW X5M Dinan Stage 1
Joined
·
550 Posts
Seems like it. Main bearing failures have been reported on our sister engine the S65 but it hasn't seem to come up with the S85. I believe P-Chi's is due to crank run out though
WOW. How do you bend a crank shaft???!!!! I mean...outside of the obvious like CRAZY HORSEPOWER.
 

·
Registered
Joined
·
532 Posts
WOW. How do you bend a crank shaft???!!!! I mean...outside of the obvious like CRAZY HORSEPOWER.
Well I've only heard of it happening once on an S85 and it was from something hitting the crank pulley in a front end collision.
 

·
Premium Member
E60 M5 and building engines
Joined
·
208 Posts
Discussion Starter · #20 ·
HOLY CRAPOLA...WHAT ARE YOU GUYS TALKING ABOUT? So the crank case/girdle/main/ooga booga can show signs of damage because of the bearings? My limited experience with the S85 aside....this is the first I'm learning about this.

Ahhhh...screw it. If I blow my engine....I'll just buy a new one and tell the new one what a wuss the old one was.

View attachment 949637
Hello kimcheebowl,

LOL.....Ahhhh...screw it. If I blow my engine....I'll just buy a new one and tell the new one what a wuss the old one was

I am many other S85 owners are doing this....getting a 2nd engine....just in case.

Want some more scares? Look up a raw block on ebay and most if not all will have scoring on bank-2.

Please help if you can as we are all trying to figure out why these engines suffer too much. My money in fuel injectors, but if the engine is well maintained, the MIL light should alert the owner before any serious damage.

My thoughts only.
Mr. P
 
1 - 20 of 33 Posts
Top