which supercar produces more downforce at present??

You talking aerodynamics ?

Interesting topic. Go on.

I do know that Saleen S7 at 160mph can create a down force equal to that of its own weight. So trying to race upside down at 160mph is, I'd imagine, a very tempting idea to those who own one.

On second thought the liquids in car not going into the right places while upside will prolly cause it to not work upside down.

I've heard that Indy and F1 cars have a downforce = 2x their weight at 200mph.