The HKS Track Attack Altezza...
The HKS Track Attack Altezza creates so much downforce that it literally sucks the car onto the tarmac.
Adding downforce fights the effects of lift, and more. The proper application of downforce, by manipulating the movement of air over the car, will actually increase the friction between the tires and the ground, so you can accelerate, brake and corner harder without the tires spinning, skidding, or sliding.
Wings and spoilers are the most common tools used to increase downforce. An automotive wing basically takes the design of an airplane wing and turns it upside down, changing an airplane's lift into a force that pushes down on the car. A spoiler is even simpler, as the drag of the air flowing over it creates downforce.
Kim's aero tips for street...
Kim's aero tips for street cars dealt mostly with controlling the air flowing under the car. Using an air dam or chin spoiler will route air away from turbulence-causing areas in the chassis, like suspension components, oil pans, transmissions and such.
You can also create downforce by lowering a car. Bringing the bottom of the car closer to the ground makes the air flowing beneath it move faster. An aerodynamic principle called Bernoulli's Equation states that faster air speed results in lower air pressure, and low air pressure under the car creates downforce.
When talking about downforce, one word that kept coming up from all the experts was "balance." You have to be careful when exerting downforce on a car so as not to throw off its overall balance. For example, in a front-wheel-drive car, having some downforce on the rear wheels is necessary to stabilize the portion of the car that, for the most part, is just going along for the ride. But exert too much downforce on the rear wheels and you can unload the front wheels, which will result in a loss of traction that hurts acceleration and creates understeer. Conversely, if you put too much downforce over the front tires in an effort to help traction, you could unload the rear wheels and induce oversteer.
Downforce increases as speeds increase, but downforce increases faster than speed. As speed doubles, from, say, 35 to 70 mph, the downforce exerted by a wing or spoiler will increase by four times. This can cause changes in handling and traction characteristics as speeds go up and down. So, again, balance the amount of downforce you're seeking with the type of driving you're doing, so you work up to optimal downforce at peak speeds.
OK, now that you're armed with some aerodynamic basics, let's talk with some experts in the field to find out how to apply these rules. For some more basic aero info, check out our Aero Glossary.
The 200-mph Celica
In May 2002, the Turbonetics/Scranton Brothers Celica, powered by a twin-turbocharged Tundra V-8, became the first sport compact car to go more than 200 mph in the quarter-mile. And as Tyler Tanaka, Turbonetics' marketing manager put it, when you're looking for high miles per hour, aerodynamics are very important. "You're looking for any way to lighten the load on the engine to make the car quicker and faster."
The body used on the race car contains some Celica body panels, but the envelope was stretched and widened to fit over the drag-race chassis. "We were looking for the lowest CD possible that would still fit on the frame and look like a Celica," Tyler said.