S55 Crank hub Fix for F80 M3 and F82 M4 crank hub issue
The notorious "spun crank hub" has become a fairly common repair for the S55 engine and is now a prevalent preventative maintenance item for F80 M3 / F82 M4 owners to prevent a potentially catastrophic failure from occurring.
After completing a handful of these repairs, StudioRSR has been able to reduce the amount of labor hours to a 1-day turnaround time without sacrificing any of the necessary replacement procedures, items, and/or hardware.
To briefly explain what happens when your crankhub spins, we go over some of the basics of how the factory crankhub was designed and what the failure means in the video below by "Simply Car Things" (explanation at 1:40)
As particularly interesting cases that we were able to somewhat document, the following s55 engines both have varying results after examining the aftermath of the crank hub failure.
Case A: 2019 F80 M3 CS
Mileage at failure: ~3,200 miles
RPM / driving condition at failure: Below 4k RPM, part-throttle acceleration
Running Condition after failure: Vehicle ran/drove with Drivetrain Malfunction displayed and CEL.
Relevant Drivetrain Modifications: Upgraded hybrid turbos, downpipes, custom ECU Flash
Engine damage: No engine damage.
Case B: 2016 F80 M3
Mileage at failure:
RPM / driving condition at failure: ~4500 RPM, hard acceleration
Running Condition after failure: Vehicle did not start/no turnover.
Relevant Drivetrain Modifications: Factory turbos, downpipes, custom ECU flash
Engine damage: 12x bent exhaust valves, no detrimental damage to pistons to warrant a full rebuild.
Factory crankhub removed from Case A:
Factory crankhub removed from Case B:
Factory crank hubs with sprockets removed to show difference in wear/damage (Case B first; Case A below)
(Above: The area highlighted in red shows the damage on the crank hub caused by the sprocket improperly spinning. The damage extended beyond the beveled area of the crank hub. Below: compared to Case A's factory crankhub with a small amount of slip.)
After rebuilding and upgrading the head with Lang Racing's Stage 1 Performance head for Case B, and completing some new mods for Case A, both cars started right up with 0 misfires and 0 error codes.
If you'd like to inquire about repairing your spun crank hub or would like to upgrade to one of the few upgraded crank hubs that we offer and install, please feel free to contact us and one of our Specialists will be glad to discuss your specific options and upgrades:
- Robert R