After months of speculations and contradictory reports, the saga of the next generation M3 and M4 engine has come to an end. While attending the BMW M6 Convertible and 6 Series Gran Coupe press drive event, we learned that the engine of choice for the M3 and M4 is an inline-six unit.

BMW of North America CEO, Ludwigh Willisch, shared with us the news and the confirmation puts an end to the speculations that have taken place over the last year, some of them who we are directly responsible for. Our own team went into a debate on what the final engine choice will be, from an inline-six turbocharged, as we heard from some BMW insiders, to an unique V6 powerplant that will revolutionize the automotive industry.

As we heard from other sources before, a V6 unit was on the table and tested by M, but for reasons like balance and weight distribution, it never made it to the production car. The inline-six turbo unit is likely to produce around 450 horsepower.

Some of the new features in the next M3 and M4 include an electronically controlled differential as found in the M5.

The engine is expected to be mated to a dual-clutch transmission, but we won’t be surprised if a manual box will be offered for the U.S. customers.

The BMW M3 will debut in 2013, followed a year later by the M4 Coupe.