I took my Z4MR to her first track day at NJMP early November, since this is only my second time doing a track day I was still in green. The first day I was on Lightning and was doing pretty well, even slowly learning heel-toe from my instructor. Unfortunately I wasn't paying attention to the dashboard and ran out of gas on track near the pit lane. Car was towed in.
Second day we were running on Thunderbolt and again, I was learning more and shifting more often on the track. I only ran between 3rd and 4th gear, sometimes just redlining at 3rd gear during a straight. The engine cuts power at redline, however I would downshift early into the braking zone instead of late but never did a money shift.
By the 3rd run on the second day, it was during a long turn around the 'octopus' where the service engine light came on and a loud engine knocking sound started as I coasted back to pit. A couple of guys took a look at it did a quick look at the spark plugs but nothing visible.
I had the car towed to Bimmer Clinic and had them take a look. The tech told me the first thing he thought of when he heard the knocking was the rod bearings, I had them take the oil pan out and the valve cover off.
The rod bearings were worn as it seems like a common issue with S54 engines, but no other visible issues like valves, springs, vanos. They saw some wear or deposit on the piston walls but could not verify with only a boroscope, but I also didn't want to spend that much money just to remove the cylinder head to inspect since the common cause of knocking was bearings.
I am having them replace the bearings with a treated version and should be done next week. I am hoping that will solve the issue and not have to swap engine blocks.
Videos of Lightning
Thunderbolt
Final lap of breakdown
I'll keep you guys updated.