FAILED BMW M5 Stage 2 = Bent Conrod
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- Опубліковано 18 бер 2023
- 6-year-old BMW M5 with a Bent Conrod and Cracked Piston!
(This work was carried out 3 years ago in 2020).
This 2014 F10 M5 (S63 engine) has 74,000 miles and is Stage 2 tuned.
Without warning the owner experienced an audible knocking noise.
Dreading the worse he switched the engine off and recovered the M5 to us for investigation.
Having not heard the knocking noise ourselves, it was hard to say what the issue might be, but seeing as the S63 is also susceptible to Conrod Bearing failure all parties initially assumed it may be a failed Conrod Bearing:
www.redish-motorsport.com/BMWF...
After we removed the sump (engine in vehicle) we found the bearings in OK condition.
However, the Conrod on Cylinder No.1 had a slight bend in it so the decision was made to remove the engine to allow an engine strip down and full assessment.
Once the engine was removed and the top end was disassembled, we pick up this short video clip here.
It shows how the slight bend in Cylinder 1 Conrod has shortened it which allows the Piston to travel down further at BDC.
This meant the underside of the Piston Skirt was coming into physical contact with the Crankshaft Counterweight at every rotation.
Even though the owner turned the engine off as soon as he heard this knocking noise, the engine probably did a few hundred revolutions and therefore made Piston-to-Crankshaft contact a few hundred times!
That was enough to also damage the Piston Skirt and cause a flattening to the underside along with displacing some Piston material into a sharp edge.
Not to mention causing 3-4 hairline cracks in the Piston around the Gudgen/Wrist Pin area.
It's amazing how much damage was caused in just a few seconds.
Interestingly, the Conrods inside the S63 engine are actually N63 Conrods!
(part number 11247843237)
This is just about OK as the S63 has approx 80nm more torque than an N63:
However, the risk comes when the S63 engine is tuned (Stage 1 / Stage 2 / Stage 3 etc) as the torque increases significantly whilst the engine internals are STILL ORIGINAL:
The N63 (F10 550i) has 600nm Torque.
The S63 (F10 M5) has 680nm Torque.
The S63 (Stage 1) has 800nm Torque.
The S63 (Stage 2) has 900nm Torque.
Asking up to 50% power to go through the N63 Conrod is where it goes wrong.
That's why we always use an uprated Conrod in our S63 Engine Rebuilds.
We rebuilt this F10 M5 (S63) Engine back in 2020 and used Carrilo Rods and Pistons to future-proof this engine.
If your S63-based vehicle is tuned, unfortunately, there's not a great amount you can do to prevent Conrod failure/bending as it's an inherently weak design due to the S63 using the N63 Conrod.
Your options are either dialing down your tuned vehicle in terms of power reduction, reverting back to an OEM tune, or upgrading the Conrods inside your S63 engine as a preventative measure (that requires an engine rebuild).
A totally separate issue is the slightly tight oil clearances between the Conrod Bearing(s) and the Crankshaft Journal, as well as the potentially unfortunate position of unknowingly having a 'Tolerance Stack' engine, (not to mention some BMW Main Dealers using BMW 0w20 LL17 FE+ Engine Oil).
If you're worried about Conrod Bearings, we offer a preventative measure to replace them (and Conrod Bolts) which you can read about here:
www.redish-motorsport.com/BMWF...
Did you learn anything from this video, if so, drop us a comment.
Is there anything further you think we should add to this sort of video?
(More detailed engine-building videos are coming soon).
Thanks for watching, and be sure to look out for next Sunday's video....
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Thanks for watching! - Авто та транспорт
You know you are the BMW guy when a dealer gives you a car to fix. And as previously stated. Dealer will only want to replace with a new engine. Not repair. Brilliant video as ever.
The clearance on the crank with the pistons looks like it was completely overlooked at the design stage.
Very interesting video James ❤
Another really informative video James. It seems to me that the best policy is to leave the engine in standard mode, really. they are already plenty powerful.
Excellent video, as ever. Did I learn anything? Yup, why oh why tune the car? Is the standard M5 not quick enough? I'm sorry this is a catastrophic failure but the words reap and sow spring to mind.
Great video. I am reading the technical training manual for the S63TU and it mentions this: "Connecting Rod: The connecting rod of the S63TU has been redesigned. It is a cracked and forged connecting rod with a trapezoidal design. In the small end of the connecting rod a formed hole is used like in the N55 engine. The force is evenly distributed over a larger area and the load on the edges of the rod bushings is reduced considerably." After reading that my questions are: 1/Is this an S63TU engine; 2/does the S63TU have the same rods as the N63 (did the N63 also receive a technical update) and 3/were the conrods in the original N63/S63 forged prior to the TU? Trying to track improvements done over the years is helpful for me to understand if later variants have stronger designs. Thanks!
I have 8 rods here from my car if you want to take a look at them since the rebuild 😂. They are the same part number as the N63 550i rods. Not very stout at all, the car ended up having forged Carrillo rods installed and all new pistons.
I don't understand how people can be messing around with an engine for "more power", and then complain that the factory parts "are not good enough".
This is what happens when people push for more power on an engine that already has more than enough power!
Not necessarily true. My bent conrod was due to a bad injector.
I think if i was the m5 owner i would have a stress crack too
My concern with the newer M5’s would be inadvertently buying one which has been remapped - how would you know, and it’s likely it makes these issues worse, or even cause them.
Well said Alex, I have this fear regarding precuring an F12 M6
I wouldn’t buy these cars used. I previously owned a BMW Certified F10 M5, and to my surprise I found out after my purchase the previous owner beat on the car. The previous owner posted the vin online and bragged about tuning and drag racing it. The car in no way should’ve been BMW “certified.” Needless to say, almost $15,000 of warranty repairs were performed on the car in the 2 years I owned it.
@@MatthewJay80 Thanks for sharing that info
Main dealer wouldn't fix? Or could not fix?
I guess it might have been embarrassing for them if they failed to diagnose and fix it. Maybe worried their workshop guides might not give them all the answers for what can happen to a tuned car? Far easier and probably more lucrative to stick to servicing the 320's and leave it to someone who knows these engines inside out! Oh Redish, how I wish I money was no object... my z4m does too! Thanks for these great videos.
Dealers dont rebuild just replace
Nice touch James, great to see you having to do what the stealers cant!!👌