fans for downforce

What do you guys think of using fans to suck air from the bottom of the car in rectangular side skirts to produce suction and downforce? of course they wouldn't be ordinary house fans but basically the same idea?
I read something in popular science magazine about using venturi tunnels under a car and using fans could produce some really good suction and traction.

Venturi tunnels do provide a crapload of downforce...a lot of modern sports cars and race cars have them. I know that the Salleen S7 has the ability to stick to the roof of a tunnel at speed with all of the downforce it makes with it's venturies.

There was a Can-Am race car (Chapparal) from about 37 years ago that used a big fan and skirts to create downforce. It worked very well and won its first race. But the fan acted like a big vacuum cleaner and blew every piece of dust and dirt on the track into the air behind it, which make it almost impossible for others to pass it

It got banned after its first race.

the same thing happened in the 60's or 70's with the Brabham F1 car, it won its first race but blew rocks into competitors faces (oh the love of open cockpit) and was banned.

They had a car called "The Sucker" that produced so much down force it could corner in excess of 1.9 G's (about twice the road-holding ability of most "super cars") - I'm not sure if it used fans or not though. It was banned because it was deemed "unsafe" because it could corner so un-godly fast. They figuired if it broke downforce turning on a dime at those speeds that it could fly off into some unsuspecting spectators way too easy.

That's why in F1 venturi tunnels were banned, a couple of times the cars broke suction and got airborne. Not a good thing when your going 200+ MPH lol.

How exactly does the "venturi" effect / shape work? I've heard it used before, and I know it's on the back ends of lots of super cars, but I'm kind of left in the dark. Can someone explain?

The venturi is the basic shape of the device used in Bernouli's principle. The same thing that causes lift in an airplane wing can create the opposite of lift in a car. A venturi is simply any enclosed tube which uses a change in cross-sectional area or diameter to effect a change in pressure. Basically, race cars use Bernouli's principle on the outside of the car since pressure changes are naturally present under and around the car, but we're basically discussing the use of artificial pressure regulation with fans.

Bernouli's principle basically states that identical airflows forced over different distances will exhibit different pressures. The airflow over an airplane wing takes a longer distance than the air under the wing, and it therefore creates a lower pressure above the wing creating lift. An airplane wing is basically a venturi without the tube part. If you took a venturi (in this case a tube of reducing diameter) and cut it lengthwise and flattened it out, that is an airplane wing.