Auto 101; spoiler

 A spoiler is an automotive aerodynamic device whose intended design function is to 'spoil' unfavorable air movement across the body of a vehicle in motion, usually manifested as lift, turbulence, or drag. Spoilers on the front of a vehicle are often called air dams. Spoilers are often fitted to race and high-performance sports cars, although they have become common on passenger vehicles as well. Spoilers are added to cars primarily for styling purposes and either have little aerodynamic benefit or even worsen the aerodynamics.

The term "spoiler" is often mistakenly used interchangeably with "wing". An automotive wing is a device designed to generate downforce as air passes around it, not simply disrupt existing airflow patterns. As such, rather than decreasing drag, automotive wings actually increase drag.

OPERATION

Since spoiler is a term describing an application, the operation of a spoiler varies depending on the particular effect it is trying to spoil. Common spoiler functions include disrupting airflow passing over and around a moving vehicle. A standard spoiler diffuses air by increasing amounts of turbulence flowing over the shape, "spoiling" the laminar flow and providing a cushion for the laminar boundary layer.However, other types of airflow may require the spoiler to operate differently and take on vastly different physical characteristics.

The goal of many spoilers used in passenger vehicles is to reduce drag and increase fuel efficiency. Passenger vehicles can be equipped with front and rear spoilers. Front spoilers, found beneath the bumper, are mainly used to decrease the air going underneath the vehicle to reduce the drag coefficient and lift.

Sports cars are most commonly seen with front and rear spoilers. Even though these vehicles typically have a more rigid chassis and a stiffer suspension to aid in high-speed maneuverability, a spoiler can still be beneficial. This is because many cars have a relatively steep downward angle going from the rear edge of the roof down to the vehicle's trunk or tail, which may cause airflow separation. The flow of air becomes turbulent, and a low-pressure zone is created, increasing drag and instability (see Bernoulli effect). Adding a rear spoiler could be considered to make the air "see" a longer, gentler slope from the roof to the spoiler, which helps to delay flow separation and the higher pressure in front of the spoiler can help reduce the lift on the car by creating downforce [citation needed]. This may reduce drag in certain instances and generally increase high-speed stability due to the reduced rear lift.

Due to their association with racing, spoilers are often viewed as "sporty" by consumers. However, "the spoilers that feature on more upmarket models rarely provide further aerodynamic benefit."