Motor vehicle with a rear diffuser

A motor vehicle, comprising:

• an underbody extending rearward from a position in proximity to a rear axle of the vehicle in a substantially horizontal plane;
• and
• a diffuser extending rearward from the underbody and including:
• a positionally fixed front part having a front end connected to the underbody and a rear end spaced rearward from the front end, the positionally fixed front part of the diffuser being curved up from the front end to the rear end thereof, and
• a movable rear part pivotally connected to the rear end of the front part with a pivoting connection that prevents air flow on an upper side of the diffuser while permitting a pivoting movement about a transverse positionally fixed axis of rotation, the movable rear part being pivotable between an upwardly pivoted operative position where the movable rear part extends up from the positionally fixed front part and a downwardly operative position where the movable rear part of the diffuser is at a reflex angle with respect to the upwardly curved positionally fixed front part of the diffuser.