Front air dam
- Thread starter GregM
- Start date
Andy Bettencourt
Super Moderator
I agree- awesome article. Thanks Greg for the contribution!
A question arose while I was reading;
How come there are provisions in the GCR that allow for fitting of an airdam and splitter that would result in an increase in front end downforce, yet, there are no provisions for increasing downforce in the rear?
(Not trying to start trouble just asking!!)
R
A question arose while I was reading;
How come there are provisions in the GCR that allow for fitting of an airdam and splitter that would result in an increase in front end downforce, yet, there are no provisions for increasing downforce in the rear?
(Not trying to start trouble just asking!!)
R
Well, you asked for it...
The air dam/spoiler has historically been viewed as a drag-reduction item, not a downforce-producing (or lift-decreasing) device. We didn't have complex computer flow modeling 25 years ago, all we had was seat-of-the-pants, "hey I'm going 5 miles per hour faster into the bridge at Road Atlanta" type of testing. You'll notice in that article that the affect on drag reduction (mostly from reducing under-body turbulence) far outweighs its affect on downforce, and that is typically supported by the seat-of-the-pants-wind-tunnel testing.
Given its drag reduction value, there had to be limits, and those limits were set (generally speaking) at no lower than the bottom of the wheel (so a flat tire does not cause it to drag), no higher than 4 inches above the center of the hubs (so that you cannot use it to reduce cooling drag), no farther back than the front of the wheel openings (so that you cannot use it to reduce wheel opening drag), and within the outer confines of the body outline (so you can't use it to produce downforce with extended winglets). Of course, think of the cars we had "back then": most of them were blunt front cars with protruding bumpers (think Pinto, Capri, Rabbit, Scirocco, Civic, TR-7, etc). Most of these cars did not have integrated bumpers and if you followed the rules it would be VERY difficult to construct any type of aerodynamic downforce given the horizontal restrictions and protruding bumpers excluded.
Today that's not the case; most cars are shipped with enclosed integrated bumper assemblies and it's perfectly legal to the rules to attach someting under that cover. You mount an air dam under the nose of your Z3 and you'll have a good 4 to 6 inches of forward horizontal space to work with before you hit the tip of the nose. That can be a big advantage (especially for FWD cars).
Geo's favorite slogan is "if it says you can, you bloody well can." While there are no allowances to install a splitter, there are insufficient restrictions on the air dam to disallow one. Who's to say that this piece is a "not specifically allowed" aerodynamic device or actually a specifically-allowed air dam part? Absent those restrictions, the "openness" of the air dam rule pretty much allows you to do whatever you want within those physical boundaries.
So, it's not that the SCCA is specifically allowing a splitter and thus frontal downforce; I'm of the opinion that it was not even considered at the time the rule was written simply because "they" could not have foreseen the design of current vehicles... - GA
