Aerodynamics

Regardless of the purpose of the vehicle, one important consideration has influenced the style of all late-model cars and trucks: Aerodynamics. Aerodynamics is the study of the effects of air on a moving object. The basics of this science are fairly easy to understand. The larger the area facing the moving air the more force will be put on it by the air. The air tends to hold back or resist the forward motion of the object moving against it. Needless to say, the less air a vehicle pushes out of its way as it moves, the quieter it will be and the less power it will need to move at a given speed. If engineers want to make a vehicle use less fuel and emit fewer pollutants, they simply do whatever it takes to make the engine work less hard. Aerodynamics is one of the factors that can be used to accomplish these goals. Although the basics of this science are simple to understand, the finer points are not. What air does as it is forced around an object is not precisely predictable. As a car moves down the road, it moves the air over, under, and off to its sides. The amount of air drag a vehicle creates is determined by the amount of air the vehicle moves. Minimizing air drag is the easiest part of aerodynamics. The difficult part is predicting, then controlling, wherethe air is being moved to and where the air goes after it has been moved. Of course, more air is moved as the vehicle increases its speed. Ideally, the air that is moved by the vehicle will follow the contours of the vehicle. This prevents the air from doing strange things as it is pushed away. If the air that moves under the vehicle has a place to push up, the vehicle will tend to lift. This creates poor handling, a situation that can be very unsafe. Air can also be trapped under the vehicle, which increases the air drag of the vehicle. If the air moving over the top pushes against the vehicle, there is an increase in air drag. To help direct the air and make some of the air useable, air dams and spoilers or wings are used. Front air dams are rigid, skirt-like panels that are placed below the front bumper. The air dam diverts air up and over the hood, into the grille opening, and/or around the sides of the vehicle. By diverting this air, less air is allowed to flow under the vehicle. This results in less lift on the front end, less drag, and less under hood pressure. Nearly all vehicles benefit from air dams. They reduce a car's overall drag, aid in engine cooling, and even help to cool the front brakes. Rear spoilers and wings are designed to control rear end lift and air drag at the rear of the vehicle. It is important to remember that many cars that are equipped with rear spoilers or wings don't really need them. Often they are added to make a car look sporty’. Since these aerodynamic “aids” don’t really begin to work until nearly 100 mph (160 kph), their only purpose on many cars is simply looks. In fact, on some cars, these actually hurt high- speed operation by increasing drag. Spoilers are used to reduce air drag and lift. By moving the air down onto the rear of the car, downforce is increased as the car's speed increases. This downforce makes the car more stable at high speeds. In some cases, the spoiler is used to move the air away from the rear of the car to reduce air drag. Rear wings are narrow horizontal surfaces mounted above and away from the car's body. They are designed to deflect undisturbed air down toward the car’s body. Moving the air down increases the car’s downforce. The closer a wing is placed to the body of the car the less effective it is. The angle of the wing also changes its effectiveness. Many race cars have adjustable wings. Adjustments are made to match the car's racing speed with the conditions of the track.