Despite what looks like a screenshot from the game, above, the E-motion concept car is not available to drive in Gran Turismo 5. It's not even a real car.
It's instead one of the best fan projects I've ever seen for a game. Four French designers have teamed up to design the vehicle, which they've (virtually) built from the ground up, engineering a car that would be able to "change its mass distribution during the race... if you are in a turn, in a straight line or breaking phase."
In other words, morph and transform depending on how fast you were driving and how you were handling the car.
It looks like it'd be fast as all hell, too. Powered by a battery and weighing almost nothing, it would fly around the track, with performance the designers say would be a "compromise between a kart and a F1".
If, you know. The car actually existed.
The idea of putting non-existent cars inside Gran Turismo isn't new—the X-1 being perhaps the most notable example—so maybe developers Polyphony cold help these guys out.