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 and are positioned below the front of the vehicle. Spoilers are frequently fitted to race and high-performance sports cars, although they have also become common on passenger vehicles. Spoilers are added to cars primarily for styling and either have little aerodynamic benefit or worsen the aerodynamics. The term "spoiler" is often mistakenly used interchangeably with "wing". An automotive wing is designed to generate downforce as air passes around it, not simply to disrupt existing airflow patterns. Rather than decreasing drag, automotive wings actually increase drag.
Operation Aerodynamics plays a critical role in a car's behavior at high speeds. Vehicles must be stable and balanced first at lower speeds through their mechanical grip on the road via the chassis, suspension, and tires. Aerodynamic aids can then be used to provide the necessary balance and stability characteristics at higher speeds. Spoilers and wings on a vehicle have little effect at low speeds as improper designs may create undesirable responses and lower stability or efficiency for the car at high speeds. Since "spoiler" is a term describing an application, the operation of a spoiler varies depending on the particular effect it is trying to spoil. Standard spoiler functions include disrupting airflow passing over and around a moving vehicle. A standard spoiler diffuses air by increasing 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.
In racing cars While a mass travels at increasing speeds, the environment's air affects its movement. Spoilers in racing are combined with other features on the body or chassis of race cars to change the handling characteristics affected by the environment's air. Race tracks demand specific aerodynamic configurations due to the varying speeds and track layouts. Configurations and devices may also be tailored to suit the talents of a particular driver, with the overall goal of reaching faster times. A car's performance is susceptible to the aerodynamic forces acting upon it because both drag and downforce increase proportionally by the square of velocity. This relationship has implications for vehicle setup. At speeds below about 120 mph (190 km/h), aerodynamics plays a role, though the emphasis shifts.
On short oval track racing, maximizing downforce is crucial for enhancing grip and enabling higher cornering speeds. However, excessive drag can severely hinder acceleration out of corners and top speed on the straights. Teams often use relatively large rear wings and front splitters, but must balance downforce and drag. Road racing courses present a mix of high-speed straights, tight corners, and elevation changes. Aerodynamic setups must balance downforce for cornering and minimizing drag for straight-line speed. Teams often employ adjustable aerodynamic elements, like wings and flaps, to fine-tune the car's behavior for different track sections. In contrast, at speeds higher than 120 mph (190 km/h), such as those seen on superspeedways, even small changes in aerodynamic configuration can dramatically impact handling and performance.
Passenger vehicles
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 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 airflow becomes turbulent, creating a low-pressure zone, increasing drag and instability (see Bernoulli effect). Adding a rear spoiler could be considered to make the air "see" a more extended, 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. 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. In 1968, Craig Breedlove set a flying mile record of 161.7335 miles per hour (260.28 km/h) at the Bonneville Salt Flats with a prepared production 304 cu in (5.0 L) V8 AMC Javelin featuring Breedlove's unique roof-mounted spoiler. Stylists at AMC later made a streamlined fiberglass airfoil above the rear window that became a factory option on the 1969 Javelins. Testing by Car Life magazine indicated no improvement in reducing lift at speeds below 115 mph (185 km/h). This feature was replaced and homologated in 1970 by AMC with a trunk lid-mounted oversized ducktail spoiler designed by Mark Donohue and Roger Penske. This race-proven feature became standard equipment on every 1971 through 1974 AMC Javelin AMX models. However, "the spoilers that feature on more upmarket models rarely provide further aerodynamic benefit." The vast majority of the designs do not do anything, except the factory units on competition and high-end sports cars, while some manufacturers disclose that their "spoilers are for looks only". Moreover, "attention must also be paid to the sides of the car" to achieve drag reduction such as techniques to reduce the cross-sectional area at the rear of the car to reduce the volume within the wake as in the case of a boat-tail design that extends back to a fine point.
Material types
Spoilers are usually made of lightweight polymer-based materials, including:
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