BMW->ke178 had already announced to its European buyers that the 5- and 6-Series cars would be getting a power boost, but left out us folks in the U.S. Well, that didn’t last too long, as BMW has formally announced that U.S.-spec 5-->ke317 and 6-Series->ke320 models will be getting a healthy boost in the power department too.

The models that are getting the boost will all come in the 2013 model year and they include the 550i, 550i GT, 650i coupe, and 650i convertible. The overall size of the engine in these models will remain at the same 4.4-liters, but the addition of BMW’s Valvetronic variable valve timing is what gives this twin-turbo engine the extra punch it needs.

This extra punch will be a noticeable one too, as the gains are pretty significant. In 2012, the 4.4-liter V-8 pumped out a respectable 400 horsepower and 450 pound-feet of torque. The 2013 models will boast 445 horsepower and 480 pound-feet of torque, which, barring any significant weight gain, should increase overall performance in a noticeable manner.

The lower level 5- and 6-Series models - the 640i, 528i and 535i - all look like they’ll carryover with their existing power plants. We’ll keep you updated if any more updates come down the line regarding the 2013 5- and 6-Series cars.

We will also keep an eye on whether BMW decides to upgrade all of its V-8-powered models to this new and improved 4.4-liter.

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