Does it really matter how powerful your engine is if air slows ya down? At about 80 seems like air wants to rip it apart. I know some of that can be expected but surely there is something I can get to make myself a bit more aerodynamic.
Good thinking- Just take it one step further to understand what's happening.
For a given speed, you are displacing x cubic feet of air per second. The air striking your vehicle provides all sorts of unwanted forces- Lift, drag, and with some cars, downforce. Increase your speed, and you increase the amount of air you're displacing per second, thus increasing all of the above forces. Some are desireable, some are not.
For cars, you'd like to minimize drag, just so more of the power your engine puts out can go towards moving the car rather than fighting the wind. Now, cars will always have some coefficient of drag, so you just have to deal with it. Minimize it by all means, but you'll still have some.
Lift and downforce- These are touchy forces to contend with, at speed even more so. Sometimes you can have situations where your lift actually becomes a significant fraction of the weight of the car, taking your power source (the wheels) away from the ground. This is obviously not cool, since you end up decreasing the stability of the whole vehicle. You can counteract lift by lowering the car (allowing less air to get under the vehicle) or by providing downforce.
Here's where ricers haven't a clue. Your power comes from your front wheels, so, naturally, you'd like to keep those wheels on the ground. So, provide some method of downforce in the front of your car- An air dam, or valance. Best example- The Visteon front air dam. It cuts the air as the vehicle moves and disburses its force towards the ground as it moves. Your front wheels like to stay on the ground, where they belong. Spoilers in the rear of the car are about the dumbest thing possible for FWD cars (hence the clueless ricers who pin 8-point bucks to the back of their Honduhs...). You provide rear downforce, right where the wheels that aren't doing a damn thing are sitting, shifting the weight away from the drive wheels.
Of course, you don't really have to contend with these forces on a large scale until close to about 100MPH or so- It's crucial for NASCAR, BTCC, and F1 where speed is paramount.
This isn't to say that a rear spoiler may or may not be a necessary aerodynamic item on a FWD car however; SCCA Pro touring class all use spoilers, as do many other events featuring mixed FWD and RWD cars. The purpose is to work in conjunction with a splitter to keep the vehicle as a whole 'stuck' to the ground, assisting slightly in traction in vehicles that travel at high speeds. Then again, to find the proper balance of wing and splitter/front valance, you'd probably have to spend way too long in front of a computer with physics equations forcing your eyes to bleed. :biggrin:
Undercarriage aerodynamics can also heavily affect the way a car sticks to the road, helping to defeat lift. This is what diffusers and the smoothest/flattest possible undercarriage can help do. There are quite a few webpages on aerodynamics floating around. Use google.com and see what you can find?
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