Too fast for Formula 1: the Brabham BT46B fan car

In 1977, the Brabham F1 team was licking its wounds after a punishing season, finishing fifth in the Constructors' Championship behind second-placed main rival, Lotus. And the 1978 season was shaping up to be even more hotly contested, as Lotus began to master the cutting-edge ground effect technology it introduced the year before. 

A revolution was needed if Brabham was going to keep up. Thankfully, producing revolutionary cars was already becoming a habit of Gordon Murray's, and he set to work building a Brabham car that was the Yin to Lotus' Yang. 

Copying the Lotus 78’s ground effect design and side skirts would have been a quick way to get the Brabham up to speed. But it was also impossible.  Murray’s car's glorious flat-12 Alfa Romeo engine left no space for the wing-shaped side pods needed for ground effect. 

Brabham’s solution came in the shape of the Chaparral 2J. Whether this early fan car inspired Murray is unclear but the two cars used the same basic tech, a large fan that physically sucks the car into the ground. 

But the cars also differed; Brabham's fan ran off the engine rather than a separate motor, and its primary function wasn't downforce. More than 50 per cent of the Brabham's fan power was for cooling, ensuring the car stuck to the letter of the law. Because of this, even a stationary BT46B noticeably sucked itself into the road as the engine revved. 

Being able to produce downforce at any speed gave the BT46B unique handling characteristics. If the nose ran wide in you wouldn’t slow down, but speed up, boot the throttle, spin up the fan and let the car suck itself to the road, pulling its front tyres deep into the tarmac for unheard of cornering grip. 

An altimeter and pitot tube hooked up to a gauge in the cabin told drivers Niki Lauda and John Watson how much downforce the car produced; green for good, red for bad – more throttle. 

Not unexpectedly, the fan wasn't the only innovative part of the BT46B. Murray also conceived a car that ran heat exchangers instead of conventional oil or water-filled radiators. Unlike the fan, this idea didn't make it into competition, though, as poor cooling outweighed any aerodynamic benefit.

Conventional radiators barely blunted performance, and as Brabham engineers removed the steel dustbin lids hiding the cars’ huge fans, a deep unease washed across the rival teams' garages.

The BT46B's performance was so vivid that the team had to keep a lid on their true, searing, speed. Team boss Bernie Ecclestone ordered his racers to be sent out with tanks brimmed and on the hardest compound tyres available, his drivers on strict instructions to underdrive. 

Brabham wouldn't just have to battle on track. F1's Piranha Club ferocity would be on full display as frenzied opposition teams tried and failed to have the fan car banned on technical grounds, the fan’s primary cooling function plugging that avenue of attack. Mario Andretti, meanwhile, understandably questioned the safety of having a car fitted with cannon-sized exhaust spewing debris out the back at breakneck speed, but this argument also proved fruitless. 

Race day would be even worse than the other teams had feared. Still conscious of playing down the outrageous performance of their cars, John Watson and Niki Lauda qualified second and third behind Mario Andretti's Lotus 79 at the 1978 Swedish Grand Prix. But the race revealed what the cars were actually capable of, and Lauda had moved into second place by lap two behind Andretti.

Lap 20 saw Watson drop out of the race with a throttle problem, leaving Lauda to pass leader Andretti, who would later retire with engine trouble. But the fan car's real opportunity to shine came after Jean-Pierre Jabouille's Renault dropped oil on the track. As the others around him slipped and slithered as they struggling for grip, Lauda nailed his throttle over the oil and let the fan-power downforce do the rest. He won the race with a commanding lead of nearly 35 seconds, despite his best efforts to 'underplay' his performance.

The other teams demanded a steward's meeting, but the car was deemed legal. Its fan primarily cooled the engine, and while the leaf-blower back end didn't follow the 'spirit' of the law, it did follow the letter of it. 

In the end though, it was ambition, not legislation, that would bring death to the BT46B. 

Bernie Ecclestone, who was executive of the Formula One Constructors’ Association as well as owning Brabham, had ambitions to run the sport and wasn't keen to upset the team bosses he would need support from. Instead, having failed to negotiate a three-race reprieve, Ecclestone chose to withdraw his machine from racing, returning the cars to standard BT46 configuration with immediate effect. 

It was a strange parallel for a man famed for his ruthless negotiating, but who ultimately gained his power by choosing not to dominate the sport he loved on track. Unfortunately as a result, we will never know quite how good the Brabham BT46B really was.

The 2025 Festival of Speed takes place on 10^th-13^th July. Friday and Saturday tickets are now sold out, but Thursday and limited Sunday tickets are still available.

Images courtesy of Getty Images.