[Sylvan]

Originally Posted by jus7o

I think the wing is for looks.

does it really serve any function?

also could it possible give you bad gas mileage?

when I get one (aw11) im taking it off.

Let's look at a hypothetical scenario. Say you were designing an aftermarket wing. If you pick a good low-speed airfoil, (say, Selig for example) which can achieve a lift coefficient over 2.0 at the right angle of attack. Now if you were able to position the wing to grab clean air and make it around 4 square feet in area, you can get the following kind of numbers: (made an Excel spreadsheet cause I'm a nerd)

~ 75 lbs of downforce at 60 mph.
~ 200 lbs at 100 mph.
~ 400 lbs at 140 mph.
just for the heck of it it would be ~ 800 lbs at 200 mph but we don't need to worry about that, do we?
So on and so forth.. (lift is proportional to the square of velocity).

So what would 200 lbs of downforce at the rear wheels do for an MR2? Well, say we have a 2800 lb car with 60% weight on the rear axle (pulled this out of my ass, dunno what it really is). So around 1700 pounds on the rear axle. Let's say on a good race day your tires are giving you a coefficient of friction of 1.0.

Now with our snazzy downforce at 100 miles per hour, the road is feeling 1900 pounds from the rear tires. Since we are using awesome tires we have 1900 pounds of grip at our disposal. So at the rear axle this gives us about 1.1 g's possible (1900/1700). So for all that work we gained a potential .1 g of acceleration in the rear. Yippee! Would that keep you from spinning out? Dunno, probably not unless you had an extremely well dialed-in suspension and you were a good driver.

Note that all the above assumptions about the wing and tire performance were very generous, so real-world performance would probably be significantly suckier. Then of course there will be extra drag, which would affect miles per gallon a bit, but would help with high-speed braking a bit, too.

So, I think most wings are just for looks. To really get a good functioning wing, it has to be big, and should probably use some sort of multi-flap which would look like an F1 wing and would probably get you laughed at in the In-n-Out drive thru.

I'm pretty sure most of the downforce in high-end cars and competition cars comes from the underbody aerodynamics, not the wing.