I think your perception of the fan is a wild one! The basis of this "fan boost" is to compensate for the dynamic pressure losses experience while following dirty air and nothing more. In other words the fan will push just enough air to bring the energy under the floor up to what the car would have in clean air, so the exhaust would be quite gentle - not the hellish hurricane that you have in mind.Shakeman wrote: ↑15 Aug 2017, 11:37A fan is the least good idea to create downforce going. There was a reason why it was banned because it was bloody dangerous to other competitors and spectators in the event of a crash which sent supersonic debris into the air. If you've watched motor racing long enough you know that the maxim, 'if it can happen it will happen', to be a truism.
If I have the time I would do three CFD simulations of the car in clean air, then behind another car, then finally equipped with the fan while behind another car. Then seeing how much fan is required to bring the down-force back to normal.