:facepalm:
Spoilers generally create stability by creating drag by design...some downforce, but mostly drag. What comes on an EVO or an STi or a Porsche 911 GT3 are NOT spoilers, those are wings. Spoilers mostly use one surface area for deflecting air.Think of a car with a parachute trailing behind it. Yes, that parachute is catching air and causing a lot of drag, but because of how the air is pulling on the attachment point/rear of car, it creates stability. A good example of this is the old style flap used on NASCARs (which were also used to reduce top speed). Most OEM spoilers are for asthetics though.
and largeer surface area for lower speeds..
Wings create downforce my using high and low pressure air currents along with a specified angle of attack (AOA). Much like we all know how an airplane wing works, a wing on a car will have air moving over and under it with adjustments made to the AOA for fine tuning. Notice in the picture below how you can see the fir deflect off the rear wing? Although it may look like a small change in angle, it creates a lot more force than you'd think. Also note how smooth the air is after the wing, that's minimal drag.
VS A computer model of a NASCAR's airflow with the older spoiler design. You can see how turbulent the air is behind the car. That's drag.
Wings and spoilers can be made to add downforce/stability at low speeds just as they can for high speeds, it all depends on AOA and surface area. I know several guys who autoX and use very large (8sq/ft per the rules) wings with high AOA (40+ degrees) and can make measurable differences at speeds under 60mph.
A good example of what it takes to create downforce at lower speeds. I dare you to tell these guys their spoilers look like rice...and while you're at it, try matching their times.
These designs actually create too much downforce/drag at higher speeds and would require a lot of power and a lot of front aerodynamics to balance out the rear.
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