Just like many predicted, BMW have gone with the Inline 6 turbo engine for the next generation M3.
The 4 door M3 and coupe-bodied M4 will feature a 3 liter inline 6 cylinder with two turbo chargers and a technology BMW calls "M TwinPower". New engine produces 430 ps / 550 Nm (406 lb/ft), which is a bit more power and a lot more torque than the outgoing atmospheric V8.
Emissions and fuel economy, which was very weak on the V8, have also been improved by 25%.
I am happy to see BMW committing to the inline 6 engine design, but I am not sure if turbo is the "way to go", if BMW really wanted to bring the new M3 closer to it's early ancestors, in terms of lightness and immediacy in handling and engine response.
I am sure the very smart "M TwinPower" system will yield good engine response, but I am also certain that a brand new, naturally aspirated, high compression, high RPM inline 6 would give the best driving sensation.
Naturally aspirated engines still make sense in 2014, as there have been ground-braking new engine releases from Ferrari (458 Speciale) and Porsche (918 Spyder) with very high power to displacement ratios.
One inevitable downside of non-turbo engines is inferior efficiency. BMW are trying to make the M line of cars better compromise between usability, performance and consumption. This is a very sensible and understandable policy from BMW, however, if you want to call your car "the ultimate driving machine", you can not lose your focus and go for compromises. You have to focus on the driving aspect - driving sensation and performance have to be first in the list of priorities.
Atmospheric high output engine would not fit into BMW's current fleet of high efficiency turbo engines and would result in a considerable net loss for the automaker. But I, and many others like me, would certainly be exited about such an engine, even if we never buy the car or even have a chance of driving it. The high revving, free breathing N.A. sound on YouTube videos and city streets alone would be worth the losses on BMW's bottom line.