There are many products available in the aftermarket to supplant extra forces on the performance of a car's original airflow, partly known now as ground effects. One way is by using a spoiler. Essentially, it is an aerodynamic device normally on the rear of the vehicle (a front spoiler is called an airdam) that changes the direction of airflow in order to reduce lift or aerodynamic drag. A spoiler can reduce drag and lift or create a downward force on the car. It is called a spoiler because it "spoils" the normal airflow over the car. However, it should be noted that most of these attempts to reduce drag, such as adding spoilers, underbody panels, and airdams, are not entirely practical to road-going cars. The results, if any, are very minor, if they don't result in actually impairing the vehicle's daily capabilities, including reduced ground clearance and so on. Simply put, most aerodynamic aftermarket equipment serves more to improve the car's appearance than its performance-not that there's anything wrong with that.
On the track, however, there is nothing more hotly debated than the effects of aerodynamics on a racecar, as the same principles that apply to aircraft are applied here but with a twist. The shape of a racecar chassis is similar to an inverted wing or airfoil that creates downforce rather than lift. This keeps the car on the ground at high speeds and increases traction around curves because the air under the car is moving faster than the air above it. Slower moving air creates greater pressure, forcing the car down against the track. The reverse-wing shape of the underbody creates another area of low pressure that sucks the car to the pavement.
Downforce must be carefully balanced against drag, which slows the car. Designs are refined through research using wind tunnels equipped with moving tracks to simulate racing conditions, and an efficient compromise in the downforce/drag relationship is the goal to obtain the best handling at the highest possible speeds. This concept is mostly lost on production cars.
Throughout the '50s, a typical prototype sports racing car was small and lightweight, had a front engine, and had a body with a nicely designed aerodynamic shell. Due to relatively inefficient engines, racecar designers were relegated to building a car as aerodynamic as possible by making the body round and streamlined so that it cut through the wind to make up for any horsepower deficits. Sometimes they did this too well. Racecars of the era were prone to too much positive lift, causing them to unpredictably launch into the air even if slightly provoked at high speeds.
In 1956, Michael May, an engineer, had an idea to construct an airfoil, but flip it over so that it produced a negative force toward the ground, and mount it onto his Porsche Type 550 to use the downforce to improve the traction, grip, and handling on his car. May's innovation was too successful; race organizers kept him from the track because the wing "restricted the view of the drivers behind him." Nothing more was said of the innovation or anything like it for the rest of the decade.
Ten years later, Jim Hall mounted a wing onto his 2E Can-Am Chaparral and proved the value of the concept by running competitively in the Can-Am championship that year, and he introduced it to the Europeans the following year. By 1968, wings started to show up on Formula One cars, and a new era of aerodynamic development began, specifically in the area of downforce.
In the early '60s, Ferrari's engineers discovered that by adding an airfoil to the rear end of the Ferrari 246SP endurance racer for the 1962 season they were able to direct the majority of the airflow away from the rear of the car, thereby reducing drag and lift. This technology trickled down the following year to the 250 GTO road car, which incorporated a small duck-tail rear wing.
In 1969, Porsche introduced the 917 to international sports car racing, a car with a reliable but low-horsepower engine paired with sleek, low-drag bodywork. The combination worked well, but it couldn't get the championships the factory was after. Porsche switched to a higher-horsepower engine, but the car was then plagued with aerodynamic instability problems (drivers soon named it "The Ulcer"). Through wind tunnel testing, the front and rear bodywork was restyled and the car soon dominated the Sports Car World Championship in 1970 and 1971.
However, the wing did not get popular until Porsche launched its 911 RS 2.7 in 1972, whose big duck tail reduced lift by 75 percent at high speed. Now a trademark of the 911, the "Whale Tail" appeared the following year on the RS 3.0, and it completely eliminated lift at the rear tires.
Almost 750 years ago, scientist Roger Bacon was onto something when he uttered the words with which we began this compendium: "When you get it right, mighty beasts float up into the sky. When you get it wrong, people die."