A 4 cyl turbo it s much efficient than a 6 cyl aspirated. I'll give u an example: in Europe VW & Audi sale much more cars with petrol engines (TSI/TFSI) than BMW. Here, the averrage people don t need cars with more than 200 hp, so 4 cyl and around 175 hp are enough for some good performances and also a good fuel economy. Also the taxes are much better (lower) for this kind of engines!
I'm sure that these kind of engines don t present so much interest to the North American market, but for Europe this will be a good move for BMW
