Legacy
///Member
Pho3niX90@OBDWorx said:
They do indeed
http://www.realoem.com/bmw/enUS/par...W-M3&mg=11&sg=20&diagId=11_3693&q=11247838623
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Read the WELCOME ALL BMWFANATICS post.
E92 M3 'refresher' thread
- Thread starter Ratslaaf
- Start date
They do indeed
http://www.realoem.com/bmw/enUS/par...W-M3&mg=11&sg=20&diagId=11_3693&q=11247838623
Ratslaaf
///Member
M3_FTW said:
I've given this a looooot of thought and spoken to many local experts in this regard. Including a few BMW Master techs that rebuild these motors locally.
Obviously opinions differ here, but what struck me is what a few people said: the bearings aren't supposed to touch the crank. Just dwell on that for a minute before reading on...
Did you think about it? Think a little more...
Now that you've given it some thought, I ask this: ideally, does the coating on the bearing matter given that it's not supposed to touch the crank? We all know that they do touch the crank however. The pictures above prove this.
Are clearances the issue? Well if it was, why are only the top shells overly worn but the bottom ones only show some slight wear?
My feeling on the matter is that it's all great going for harder bearings, but what happens to the crank now should the harder bearings come in contact with it?
I feel that harder bearings is a band aid solution. I'd rather determine the cause of this and there's many guys out there that lean towards pre detonation as the cause due to bad fuel.
We all know our fuel is bad. We also know that U.S. Failures are more to the South, where fuel quality is also an issue. I don't know how much any of you had spent time researching this issue, but in the research I've done I've not found any issues with these cars in the UK or Europe. And if there was an issue, I must have missed it?
So, based on what I've researched, I also drew the conclusion that this is more fuel related than anything else. Of course, I urge those of you interested to do your own research.
The next step for me is to empirically study this once my car is together to test the theory. These engines don't have knock sensors in the traditional sense, but I can test knocking by seeing how timing is pulled back under WOT. I can also test a few fuel additives and compare timing retardation using these.
That's the plan, so I think there's a lot of fun to be had going forward in testing this scientifically. I'm pretty sure this hasn't been done locally, and if it has it's not in public domain...
Fordkoppie
///Member
You would typically find that an engine tends to detonate roughly at the RPM point where it makes the most torque.
In the S65, that is at 3900 rpm. So if detonation occurred, my guess would be that it will only be in the 3000 - 5500 rpm range where the torque is at its fattest.
Analysing the affected cars, its also safe to say that almost all of the cars with modified software that increased the limiter to 8800 rpm had bearing failure. So my guess is that its still a lubrication issue at those high RPMs.
Secondly - People rev them too high when they are still not at operating temperature. I am saying that 3500 rpm when the oil is <50deg C is still too high.
I am of the opinion that even a new set of OEM bearings should last if you:
If the bearings get a nick from just one abusive session while the engine was cold, you have had your chips. Once the coating is damaged, an irreversible process has started regardless of how much care is taken afterwards
In the S65, that is at 3900 rpm. So if detonation occurred, my guess would be that it will only be in the 3000 - 5500 rpm range where the torque is at its fattest.
Analysing the affected cars, its also safe to say that almost all of the cars with modified software that increased the limiter to 8800 rpm had bearing failure. So my guess is that its still a lubrication issue at those high RPMs.
Secondly - People rev them too high when they are still not at operating temperature. I am saying that 3500 rpm when the oil is <50deg C is still too high.
I am of the opinion that even a new set of OEM bearings should last if you:
- ALWAYS Limit your RPM to 2000 until oil barely lifts the needle at 50, 2500 up to 60, 3000 up to 75 and after 80 you can go bonkers
- never exceed 8300 rpm
- never exceed 8000 RPM for longer than 5 seconds
- use 0W40 oil from day 1
If the bearings get a nick from just one abusive session while the engine was cold, you have had your chips. Once the coating is damaged, an irreversible process has started regardless of how much care is taken afterwards
Fordkoppie
///Member
Actually the piston speed is relatively low because of the short 75mm stroke
Legacy
///Member
Kish2604@TheFanatics said:
At 8200 RPM the V8's piston speed (20.56 m/s) is only slightly more than a E46 330i (19.41 m/s) at only 6500 RPM so there has to be more significant other contributing factors as well.
Another example is a 335i with a N54 which at 7000 RPM has a piston speed of 20.91 and I have not heard of any bearing failure on these thus far. And as we know the N54 guys reach these revs all the time :rollsmile:
I've only now had a chance to read this thread from begin to current and I must say Gert, you are a legend!!!!!!!:clapper:
I love seeing these type of builds fully documented with pics and vids etc. If only I had your wealth of knowledge and expertise, I'd try to do the same! (one day when I'm big LOL)
Really admire your work bud and attention to the finest of details.
Keep it up! :thumbs:
I love seeing these type of builds fully documented with pics and vids etc. If only I had your wealth of knowledge and expertise, I'd try to do the same! (one day when I'm big LOL)
Really admire your work bud and attention to the finest of details.
Keep it up! :thumbs:
Ratslaaf
///Member
Legacy said:
Well, I suppose it depends on how the car is going to be used. Knowing that clearances are dangerously small already on these cars, I'd rather have more viscosity at lower temps. I don't race the car around the track and my car has never, ever seen 120deg oil temps. So I still have good lubricity at operating temperature. If your car is purely a track toy, then yes, going for 10W60 is a wiser choice. so to make a short story long, it depends
444YYY said:
Hehe, I'd rather not think about that thank you
Pho3niX90@OBDWorx said:
Yup, that is so. And the fact that many S series motors suffer from the issue is what got me thinking down the detonation path, bearing in mind that the S54's have more clearance than the S65/85. What they do have in common is that they're tuned all the way to winwang and that they rely extensively on knock detection mechanisms.
Of course, without extensive testing we're all pretty much speculating here.
Pho3niX90@OBDWorx said:
Yup, that is so. And the fact that many S series motors suffer from the issue is what got me thinking down the detonation path, bearing in mind that the S54's have more clearance than the S65/85. What they do have in common is that they're tuned all the way to winwang and that they rely extensively on knock detection mechanisms.
Of course, without extensive testing we're all pretty much speculating here.
Stop chit chatting and get to work!! We want more pics!!! :smashScreen: :rollsmile::rollsmile:
922-ZN
Well-known member
Ratslaaf@OBDWorx said:
I will be logging my car(stock apart from exhaust) under 95, 95+NF, 95+Liqui Moly, 95+OB1 and BP98, I'll forward you the logs and we can see timing pull. Might take me a while cos I hardly use my car but none the less. What octane do you think the car will be happiest at Gert?
I don't think NF will be a permanent solution though as they tend to nacker your plugs after continued use, in my experience atleast.
Fordkoppie
///Member
Ratslaaf@OBDWorx said:
Its not.
Ask Andy
