“We do not start our design process with a power output in mind. We have a set of characteristics that a new model must meet. For sure, you could see a future [M3] powered by a four-cylinder engine. Performance can be boosted with more power, but if we are to address issues like emissions and consumption [in the future], we have to look more at weight. We decided in this generation to address the [upward] weight spiral."
What the M project management division head Carsten Prieds states makes sense. Except that they barely addressed weight issue this generation. If the car is much lighter, four-cylinder power is not a problem. It would have to be much, much lighter though. Cutting weight less than 100 pounds is not going to do it.
If BMW were to do a 400 horsepower turbo four-cylinder motor at around 2.5 liters of displacement paired to a 3000 pound curb weight, this would work. The thing is, BMW already has the opportunity for a turbo four-cylinder motor in the upcoming M2. Instead of developing that engine now BMW is opting to save money by using the inline-6 they already have. A turbo four makes all the sense in the world for the M2 right now which could see a nice evolution by the time the next generation M3/M4 are ready to roll out.
We will see what happens but it is no shock to anyone that BMW's engines are going to get smaller, less powerful, cheaper to produce, and cleaner. If only the cars were losing weight as quickly as BMW's engines were losing displacement.