Ken, according to Wiki the BMW N62B48 is used in the S4 Aeros. Did I read your post correctly in that the motor was "developed" by Alpina and then taken over by BMW for the X5?
If so what would the present S4/S5 Plus 8 Motor make if it had the Alpina engine map, rather than the BMW X5 one?
Nope. The M62B46 was developed by Alpina using specially cast blocks from BMW - BMW were so impressed by the improvements over the M62B44 they bought the engines back off Alpina - I think they were then built by BMW. The B10S used the M62B48. The N62B48 was then used in the X5.
Confused???