A spoiler is an automotive aerodynamic device whose intended design function is to either create downforce or reduce drag. Spoilers on the front of a vehicle are often called air dams, because in addition to directing air flow they also reduce the amount of air flowing underneath the vehicle which generally reduces aerodynamic lift and drag. Spoilers are often fitted to race and high-performance sports cars, although they have become common on passenger vehicles as well. Some spoilers are added to cars primarily for styling purposes and have either little aerodynamic benefit or even make the aerodynamics worse.
Spoilers for cars are often incorrectly confused with, or the term used interchangeably with, wings. Automotive wings could be loosely described as anything that has an air gap between it and the car's body while spoilers have no gap and are protrusions out of the body (generally at the rear of the car).
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A spoiler basically works by slowing down or stagnating the air in front of it which is going to increase the pressure and this higher pressure creates a downward force on the body (i.e. downforce). This higher pressure can also help reduce flow separation (e.g. at the roof and rear window transition) which may also help reduce the lift created on the vehicle. The low pressure region behind spoilers can also reduce underbody lift or help drive diffusers by pulling air upwards that flows under the car. At certain angles (generally low) and lengths a spoiler can reduce drag on a car, but will increase it if optimized for high downforce.
The main design goal of many spoilers in passenger vehicles is to reduce drag and increase fuel efficiency.[1] Passenger vehicles can be equipped with front and rear spoilers. Front spoilers, found beneath the bumper, are mainly used to decrease the amount of air going underneath the vehicle to reduce the drag coefficient and lift. Rear spoilers can be either designed with the goal of reducing drag, creating localized down force, or for aesthetics.
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 vehicles have a fairly steep downward angle going from the rear edge of the roof down to the trunk or tail of the car which may cause air flow 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 left on the car by creating downforce. This may reduce drag in certain instances and will generally increase high speed stability due to the reduced rear lift (or increased downforce in rare cases).
Due to their association with racing, spoilers are often viewed as "sporty" by consumers.
Spoilers are usually made of:
Heavy trucks, like long haul tractors, may also have a spoiler on the top of the cab in order to lessen drag caused from air resistance from the trailer it's towing, which may be taller than the cab and reduce the aerodynamics of the vehicle dramatically without the use of this spoiler.
Trains may use spoilers to induce drag (like an air brake). A new prototype Japanese high-speed train, the Fastech 360 is designed to reach speeds of 400 kilometres per hour (250 mph). Its nose is specifically designed to spoil a wind effect associated with passing through tunnels, and it can deploy 'ears' which act to slow the train in case of emergency by increasing its drag.
Some modern race cars employ a situational spoiler called a roof flap. The body of the car is designed to generate downforce while driving forward. These roof flaps deploy when the body of the car is rotated so it is traveling in reverse, a condition where the body instead generates lift. The roof flaps deploy because they are recessed into a pocket in the roof. The low pressure above this pocket will cause the flaps to deploy, and counteract some of the lift generated by the car, making it more resistant to coming out of contact with the ground.
An earlier use of the term whale tail, now used to refer to a visible thong, dates back to August 1974, when the Porsche 911 Turbo debuted with large, flared, rear spoilers that were immediately dubbed whale tails.[2][3][4] Designed to reduce rear-end lift and so keep the car from oversteering at high speeds,[5] the rubber-edges of the whale tail spoilers were thought to be "pedestrian friendly".[6] The Turbo, with its whale tail, became an instant hit.[7] It also became one of the world's most recognizable sports cars,[8] remaining in production for the next two decades in one form or another, with more than 23,000 sold by 1989, although from 1978, the rear spoiler was redesigned and dubbed 'teatray' on account of its raised sides.[9] The Porsche 911 whale tails were used in conjunction with a chin spoiler attached to the front valence panel, which, according to some sources, did not enhance aerodynamic stability.[10] It has been found to be less effective in multiplying downforce than newer technologies like an airfoil,[11] "rear wing running across the base of the tailgate window",[12] or "an electronically controlled wing that deploys at about 50 mph".[13] (80 km/h).
The whale tail came on the heels of the 1973 "duck tail" or Bürzel in German (as a part of the E-program), a smaller and less flared rear-spoiler fitted to 911 Carrera RS (meaning Rennsport or race sport in German), optional outside Germany.[2][4] The whaletail was originally designed for Porsche 930 and Porsche 935 race cars in 1973, and introduced to the Turbo in 1974 (as a part of the H-program), it was also an option on non-turbo Carreras from 1975.[14][15] Both types of spoilers were designed while Dr. Ernst Fuhrmann was serving as the Technical Director of Porsche AG.[16] In 1976, a rubber front chin spoiler was also introduced to offset the more effective spoiler.[3] By 1978, Porsche introduced another design for the rear spoiler, the 'teatray, a boxier enclosure which accommodated the intercooler, and was also an option for the 911SC.[2][17]
These whale tail car spoilers of the Porsche 911 caught on as a fashion statement,[18] and the term has been used to refer to large rear spoilers on a number of automobiles, including Ford Sierra RS,[19] Focus,[20] Chevrolet Camaro,[21] and Saab 900.[22] Whale tail spoilers also appear at the rear of tricycles,[23] trucks,[24] boats,[25] and other vehicles.
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