QUOTE(maf914 @ Jan 20 2004, 05:50 AM)
... no one seems to use them on on new prototypes anymore. I wonder why. Has new brake technology made them unnecessary?
they were always a little controversial, since FIA regulations specifically prohibit "moving aerodynamic devices".
i think the big reason now is the development of ground effects chassis, which was a new, little-understood black art in the late '70's and early 80's. now you're better off having air moving under the air to work on the undertray to produce downforce, as opposed to trying to pump air out from under the body.
the fans added unsprung, rotating mass, and wheel assemblies were smaller in diameter then. and these cars predated carbon/carbon brakes. they also add a significant amount of drag - it takes work to pump air like that - and they're most effective at the end of the straight - when brakes are cold anyway, and less effective in the slow parts, where you really want the cooling.
it was a clever way to improve braking after all the other development had boxed them into a corner. prototypes have more freedom to reject brake heat with designed-in rather than added-on solutions ...