Getting started with Aerodynamics

[exwestracer]

Are you trying to increase downforce, or reduce drag for top speed (you CAN'T do both)?

The air dam will always help to some extent, but if you are looking for real downforce; it needs to be pretty close to the ground. Like touching the ground... The idea is to stop the "high pressure" air going under the car from meeting back up with the "low pressure" air going OVER the car. The air dam will also help with penetration (uhhh...lower drag), but reshaping the entire front end would be a lot more effective.

The hood scoop isn't going to help either way, although it may kill some lift by interrupting airflow over the hood and roof...with a huge drag penalty. If you need it, run it; just don't expect to get any great aero gains from it.

A spoiler on the decklid will do a lot to kill lift, but the drag penalty is directly proportional to how well the spoiler works. The Monte aerocoupes were built for low drag in NASCAR. The notch isn't a terrible thing from a downforce standpoint, so again it depends on your goals.

Personally, I wouldn't worry about a diffuser in the rear unless you are really going to clean up the underside (flat bottom, or close to it). THe diffuser is probably the only place you will be able to generate "drag-free" downforce, but it won't do much of anything if the airflow under the car is cluttered up by hanging components...

So, what was your aero goal again?