The Brabham BT46 is a Formula One racing car designed by Gordon Murray for the Brabham team, owned by Bernie Ecclestone, for the 1978 Formula One season. The car featured several radical design elements, the most obvious of which was the use of flat panel heat exchangers on the bodywork of the car to replace conventional water and oil radiators. The concept did not work in practice and was removed before the car’s race debut, never to be seen again. The cars, powered by a flat-12 Alfa Romeo engine, raced competitively with modified nose-mounted radiators for most of the year, driven by Niki Lauda and John Watson, winning one race in this form and scoring sufficient points for the team to finish third in the constructors championship.
The "B" variant of the car, also known as the "fan car", was introduced at the 1978 Swedish Grand Prix as a counter to the dominant ground effect Lotus 79. The BT46B generated an immense level of downforce by means of a fan, claimed to be for increased cooling, but which also extracted air from beneath the car. The car only raced once in this configuration in the Formula One World Championship—when Niki Lauda won the 1978 Swedish Grand Prix at Anderstorp. To the dismay of its designer Gordon Murray, the concept was voluntarily withdrawn from racing again by Bernie Ecclestone.