I think I figured out why Red Bull’s are so fast. They’ve stuck a rocket launcher to the back of their car. Seriously though, if their exhausts come out on the floor to power the diffuser, then what the heck is this massive hole in the back of their car? There was one last year, but no where near this big.
Its where all the air which flows over the radiators and is used for cooling the engine, Kers, gearbox, etc, is let out. It normally comes out in a few smaller exits around the end of the sidepods and also in one rear exit, but in order to make the back of the car so fitted and small, they exit all the air through that one larger hole.