The B58 is certainly a stout engine and it is a new architecture compared to the N55. It responds very well to modifications although it is fuel capped. Still, how is the B58 beating the N55B30T0?
For one, the B58 is underrated and has a flatter torque curve. The M2 actually has similar power to the M240i. Forget the BMW crank figures. The B58 power curve also increases toward redline whereas the N55B30T0 torque curve drops off a cliff.
It shows in how this comparison plays out. The M2 has the advantage down low partially due to its low rev torque peak but also due to the shift speed advantage offered by the DCT transmission.
The M2 gets to 60 mph quicker but past 70 mph or so miles per hour the B58 is the one pulling harder. The difference becomes startling as the M240i pulls to 260 kph (161 mph) while the M2 is trailing badly.
What do you even say to this? The M2 is tuned how the M240i should be tuned and the M240i has the sort of curve the M motor should. What is BMW doing? Do they even know?