2015 BMW M3 and M4 revealed, featuring all-new twin turbo inline 6

The BMW 3- and 4-Series are effectively the same car, only the 3-Series comes with four doors while the 4-Series uses two (replacing the outgoing 3-Series coupe). When it comes to the 2015 M3 and M4, same rules apply. They both shed weight compared to their predecessors, go faster, produce better fuel ratings, and ditch their V-8 motors in favor of a brand new twin-turbocharged inline 6.

Sounds promising.

However, many may lament the lack of a V-8, but in today's age where fuel efficiency ratings are everything, smaller engines with turbos are becoming more prevalent. This one adds oomph, boasting 425 hp with peak power between 5,500 rpm and 7,300 rpm -- unusually high for a turbo motor. Peak torque arrives as low as 1,800 rpm, cranking an impressive 406 lb.-ft. That helps both cars shift to 60 mph in 3.9 seconds with the M-DCT automatic transmission, or 4.1 seconds with the standard 6-speed manual. Yes, the manual (now with auto rev-matching) remains. Hoorah.

Back to fuel efficiency: The new M3 and M4 are approximately 176 lbs. lighter than the outgoing models -- due to additional use of carbon-fiber and aluminum (the M3 Coupe now gets the carbon roof), a lighter engine and gearbox, along with other weight-saving tricks -- both cars can now claim a 25-percent increase in fuel efficiency. They are also notably stiffer, too, featuring an e-diff that promises "effortless drifting" and launch control to maximize the lightening fast acceleration. A lap time app is also available, offering a way for drivers to analyze their performance from their phones.

Many outlets are reporting the new M3 and M4 has a system called "Smokey Burnout Control," something that is rumored to be on the 2015 Ford Mustang. But don't get too excited. According to BMW, this is not a new system. It has, in fact, been an "unnamed feature of the M-DCT versions of the E92 M3, current M5 and M6 for several years."

U.S. pricing has not yet been released, but we'll see the new M3 and M4 at the Detroit auto show in January, appearing in dealerships early next summer.