Ever Since Infiniti unveiled the FX37 and FX50 at the Geneva motor show earlier this year, there's been some confusion as to which models are coming to the U.S. -- and why. While both markets receive the FX50, North America gets G35's 3.5, not the G37-sourced V-6.

Why don't we get the 3.7? Infiniti cites a few reasons. The company wanted to differentiate the V-6 and V-8 models, and one element of that was by widening the performance gap.

There was only a 42-horsepower difference between 2008 FX35 and 45; the new engines are now separated by nearly 90 horses. Also, the 3.5-liter's 303 horses are only 27 fewer than the 3.7 puts out, and its 6.1-second 0-to-60 time is actually faster than the previous FX45's. Despite what Infiniti says, though, the real story may be one of cost: the 3.7-liter is a more complex engine, and using it could've driven up the MSRP on U.S. models. The new version of the VQ35 isn't the only thing that separates the FX35 from the 50. Rear drive is standard, as are 18-inch wheels, and neither the Sport package nor summer tires are available.