I would’ve posted this in Technical, but really, it belongs in a section called Gospel, and we don’t have that (yet). So here goes. I’m going to tackle basic aerodynamics for you, out of the goodness of my heart, and I’ll try to keep it as easy as possible. This is not a complete, or even in-depth analysis by any means, and if you’d like, I can do a much more detailed and advanced one, in another thread, so as to keep this information segregated for the newbies.
Aerodynamics is a very often misunderstood topic, which can have some pretty bad consequences. If used right, it can give you several things, added stability at high speeds, and added grip in cornering. Both of those things kick ass, so I’m going to throw some ideas at you to help you figure it all out.
Before we begin, you have to understand what a moment, or torque is, because that’s pretty important to this whole discussion. A car has a center of mass, and it likes to rotate about it. Go to the back of your car, and push down, you’ll notice the front went up a bit. Same thing with that big ass wing on the back of your car. It’s helping keep your rear wheels jammed into the ground, but it’s causing your fronts to lift a bit, pitching your car rearward, causing more frontal lift at high speeds. Shit can get you killed.
So what do you need? Balance. Just like playing with spring and swaybar stiffness, aerodynamics modify handling characteristics, and can make your car understeer or oversteer.
For a street driven car, you can kinda forget about additional cornering grip, as you should NEVER be taking corners at speeds that will allow your aero to become functional, but high speed stability would be nice. Consider adding a front splitter for this, it will add a lot more front downforce than you would think, considering its small area.
In effect, pushes your front end down, giving you better control at high speeds, as well as promoting oversteer.
Another thing to consider is, how smooth is your underbody? I wouldn’t suggest you go all out and do a full undertray for a street car, but lowering your car will definitely help if you don’t have one. The beauty of an undertray, or having your car lower, is that the force is distributed over the car’s body, giving you downforce without upsetting the car’s balance too much.
Now on to the most common part of car aero, rear spoilers and wings.
Despite the shit that people say about functional and unfunctional, ALL rear wings that have an angle of attack to them are functional. Period. If you take a flat piece of metal, and weld it to the back of your car at a negative angle of attack, it WILL produce downforce. The question is how much, and at what cost.
Now, the difference between a spoiler and a wing, is a spoiler is attached to the car, like what comes on the S13 hatch, and is called a lip by most people. The purpose of a spoiler, is to cause some turbulence and generally mess up (aka SPOIL) the airflow at the rear of the car. This will increase the pressure at the top part, causing some downforce.
A wing on the other hand, is mounted above the trunk, and goes about things a bit differently. It uses an airfoil profile, just like something you would find on an airplane, and is meant to generate downforce. The main problem with wings is height. Due to the shape of the car, there is rarely any clean air going to them for them to do their jobs, so on most race cars, they are mounted very high. In general, despite their failings with lack of height, wings generate more downforce than spoilers.
So again, aerodynamics are a refined way to balance your car’s handling, and SHOULD NOT be played with by a total novice. Any idiot can go and buy the best coilovers out there, have them installed, and it will make their car handle better. The same does NOT apply to aerodynamics, the purpose of the car and balance have to be considered. Too much aero will hurt your top speed (for another thread), and too much aero in the wrong place can cause adverse effects to handling.
If anyone cares, I can make a much longer, much more detailed Advanced Aerodynamics post.
