Ground effect, turbo engines, big slick tires, big front and rear wings, no wood panel, active electronic suspension, and other banned equipments. In other words: What if FIA never banned anything, how much faster would a f1 go (Forget the fan car because not enough data to make a reasonable guess)
Just to avoid further miss understanding, l meant how much faster it would go arround circuits not how fast the top speed would be.

l believe the land speed record is 766 mph

http://en.wikipedia.org/wiki/Image:ThrustSSC.jpg

Sorry to joke

They actually did a 'what if' article in F1 magazine a few years ago. They took what l believe was a 2003 or 2004 Williams. They then allowed slick tyres, ground affect & no restrictions on wheels. However, the rest of the rules governing chassis protection, engine regs etc where kept the same.

The car resembled the Williams apart from a few details. There was no rear wing. The rear of the car was slightly rectangular rather than coke-bottle shaped to take advantage of ground affect. There was also six wheels. Four at the back & two at the front. Williams had actually tested 6 wheels at the end of the 80s. Rather than the 6 wheeled Tyrell of the of the previous decade, this car had the extra wheels located at the rear rather than the front. The advantage of this was that u had four wheel drive at the rear, & the front wheels free to steer. The added contact patch coupled with this offered tremendous grip. Calculations also realised that if it was to rain, the rear tyres could be left slick as fitting wet tyres on the first rear tyres would allow the water to be cleared before the rear tyres made contact with the surface!

The results where astonishing. In the simulations the car was capable of some 15g+ in the corners. That is using the same 3.0 litre V10 engine of the era. Obviously the driver would not be able to cope with those G forces. Even fighter pilot G suits would be no good! There would also be excessive strain on components so things would have to be a lot more reliable.

So ur simple answer is - if they were allowed the driver would not physically be able to push the cars near their limit without loosing consciousness!