M37 and M56 – Infiniti unveils the 2011 M midsize luxury sedans

The Infiniti M line won some key comparison tests when the current generation came to the market in 2006 — Consumer Reports and Car and Driver magazines were among its big fans.

Nissan’s luxury division today unveiled a redesigned version that’s set to go on sale next spring as a 2011 model, featuring curvier styling, more power, new technology, and better gas mileage — presumably coupled with the spacious interior and good ride and handling that won critical acclaim to the current car.

The two M cars are renamed from the M35 and M45 to the M37 and M56 to reflect their larger engines. The current car’s 3.5-liter, 303-horsepower V6 will be replaced by a 3.7-liter — presumably a slightly more potent version of the 330-horsepower engine in Infiniti’s smaller G37 line. There will be an even bigger jump in V8 power, with the 4.5-liter 325-horsepower engine disappearing in favor of a 5.6-liter that the automaker says will likely top 400 horsepower.