Originally Posted by marcel b
+1 from my own experience. Z4M with S54 no issue what so ever, reving it till 8000 RPM lap after lap on the Ring. 335i (standard w/o tune) Limpmode end of second lap on a hot day
(which is after about 17 minutes)
Without changes to the cooling you can forget pushing a 335i on the track.
I would add cooling ducts to my 335I, but I don't even have an oil cooler, so I don't know if that'll do any good.
FYI, since your in europe, your probably not getting very hot summers, in which to push your Z4's S54. Although germany did have some heat waves this summer, so I wonder if you "pushed it" at the ring on one of those days.