I am considering to make some aero mods to improve high speed stability.

I have a few questions and hope some one can provide some answers based on experience.

If I cut a hole in the trans tunnel or floor boards (car to have a significant cage) and connect a NACA duct to a 4 inch duct to the window to run at 90degrees (I cant spell perpinduclar) to the air stream will this create a low pressure area under the car?

Will NACA ducts mounted backwards suck air out if mounted at 90 deg to air flow?

It there a rear wing not spoiler that I can buy that is actually engineered to work? One with the proper cord length, wing shape, end plates, and mounting height to max downforce and reduce drag? If so would this be better than a spoiler?

What would be the effect of mounting a wing to the rear axle via round tubing extending through the rear window or deck lid area? It seems that this would put the downforce on the rear tires rather than the body work and springs and would not effect the front end of the car. I know this is illegal in most forms of racing as it has had dangerous effects; I just don't know what they are.

 

when wings are placed on a car the farther back it is the more dowmforce you will get from it, when placed back it acts as a lever providing more downforce than if it was on the axle just look at f1 cars and dragsters they are placed back for a reason. there is no reaason to cut holes in your floor to create low pressure when you can put a low front valance and sideskirts on it. read Tune to Win by Caroll Smith and you will find out much more on every aspect of building a racecar

 

Is there is specific class you are planning ot race in? obviously most of them will have specific rules on what wing shape, and cord length is allowed.

Wings tend to produce more downforce, There are many out there, just stay away from the ***** crap. You might try FabCar, Derhaag, or Hoerr. They are the approved manufactures for TransAm wings.

The real key to creating the downforce, is to smooth and limit the flow under the car (by smoothing it, you should also accelerate it, thus creating lower pressure). I don't have the exact numbers (I'm at work right now), but I was reading thru my Aero book one night, and in one of the chapters on undercurrents, it talked about ride height, and the ratio of ride height to wheel base, and what ratio it needs to not produce lift. On the Camaro, i figured a minimum of 16.5" of clearance. Not really usefull. Now with a smooth underside, then you can have the car low, and still not produce lift. with that, your cD will likely also go down.

For reading, I would suggest "Competition Car Downforce: A Practical Handbook" By Simon McBeath.

http://www.amazon.com/exec/obidos/tg...glance&s=books

 

Thanks for the sites.

I will try and get the books.

I will do my best to seal the front and sides of the car. I have a plan for that already and it should be easy enough to accomplish.

My real question is would the reverse NACA duct draw air and create a vaccum which would further serve to make the car more stable.

As for mounting the wing to the axle, This would not create leverage trying to raise the front of the car; and would not compress springs as to interfer with fender clearence. This was my intent of this question.

Thanks for the responses. I love the Carol Smith books, but do not have the one mentioned. I have never heard of the aero book mentioned, but I will have to invistigate it as well.

 

Simon McBeath knows his crap. He writes for Race Car Engineering.

Not sure about mounting it to the axle, Once you get over the packaging, i'm not sure how its going to do. Since most forms of racing have rules on what wing you can run, and how far back it can be located, most people try to run right up against those rules, and mount it to where they will get the most leverage.\

for the ducting from under the car, you would have to really seal the underside of the car, while it can be done, again, whatever optios you have here, are likely not legal in any form of racing. In the early days, there were lots of attempts at this, everything from using pumps to pump air out, to ducting. The key to most of them, was keeping the underside of the car completely sealed to incoming air. The pressure is going to try to equilize by having air come in where ever possible.