Motor vehicle with an adjustable air-guiding element

1. A motor vehicle with a vehicle rear, a rear wheel and an underbody or an underbody covering extending to the vehicle rear, the underbody or the underbody covering rising toward the vehicle rear to define a diffuser, the diffuser having a front end rearward of the rear wheel and a rear end at the vehicle rear and defining a diffuser length extending from the front end to the rear end of the diffuser, the motor vehicle comprising: at least one adjustable air-guiding element having a front edge spaced rearward of the front end of the diffuser by a distance at least equal to one-half the diffuser length and a rear edge in proximity to the vehicle rear and substantially adjacent the underbody or the underbody covering, and a holding and adjustment device connected to the air-guiding element and being configured for extending the air-guiding element from an upper rest position substantially adjacent the diffuser down toward a ground contact area on which the vehicle is supported, the holding and adjustment device further being configured for moving the air guiding element into a plurality of operative positions by pivoting the air-guiding element about an axis of rotation arranged substantially in a center of the air-guiding element and running transverse to a direction of travel.

2. The motor vehicle of claim 1 , wherein the air-guiding element is movable via the holding and adjustment device from the rest position bearing against the underbody vertically down into a first of the operative positions, in which the air-guiding element is substantially parallel to and spaced from the underbody.

3. The motor vehicle of claim 2 , wherein the air-guiding element is pivotable about the axis of rotation from the downwardly extended first operative position into a second of the operative positions, in which the air-guiding element is at an angle to the underbody and the front edge of the air-guiding element substantially bears against the underbody.

4. The motor vehicle of claim 3 , wherein the air-guiding element is adjustable in at least one third operative position that is pivotable between the first operative position and the second operative position.

5. The motor vehicle of claim 1 , wherein the underbody or the underbody covering rises from a rear axle of the motor vehicle substantially to a lower edge of the vehicle rear and forms the rear diffuser with a diffuser angle of approximately ≧25° formed between the underbody and a horizontal.

6. The motor vehicle of claim 1 , wherein a distance from the front edge to the rear edge of the air-guiding element is approximately ⅓ to ½ of the length of the diffuser.

7. The motor vehicle of claim 1 , wherein the rear edge of the air-guiding element is substantially flush with a lower edge of the vehicle rear.

8. The motor vehicle of claim 1 , wherein the air-guiding element extends over an entire width between the rear wheels of the vehicle.

9. The motor vehicle of claim 1 , wherein the air-guiding element has a wing profile with a convex lower surface and an upper surface that is nestable with the underbody covering.

10. The motor vehicle of claim 1 , wherein the rear diffuser has longitudinal channels on the underbody and the at least one air-guiding elements comprises plural air-guiding elements disposed respectively in the longitudinal channels on the underbody and being adjustable about a transverse axis within the longitudinal channel.

11. The motor vehicle of claim 1 , further comprising a control element that is operable to control movement of the air-guiding element into the individual operative positions and intermediate positions depending on a driving state of the vehicle.