"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 amount of downforce utilizing a fan, claimed to be for increased cooling, but which also extracted air from beneath the car."
https://en.wikipedia.org/wiki/Brabham_BT46
"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 amount of downforce utilizing a fan, claimed to be for increased cooling, but which also extracted air from beneath the car."