Senna's last title-winning F1 car: Why McLaren 'had to start again'

F1

Ayrton Senna won the 1991 F1 championship with McLaren's MP4/6, the only V12 car to win the title. Team members tell James Elson of the chaotic efforts to defeat the superior Williams — a fight where Senna made the difference

Ayrton Senna McLaren 1991 Belgian Grand Prix Spa-Francorchamps

Senna in his final title-winning F1 car: the McLaren MP4/6

Paul-Henri Cahier/Getty Images

With 30 years having passed since the great Ayrton Senna’s death, a special commemorative parade and commemoration will take place at his home venue of Interlagos before the 2024 Sao Paulo GP.

His 1990 title-winning McLaren MP4/5B will run this weekend, but it’s that car’s successor, the MP4/6, which became the bedrock of his final championship-winning year – one that could be put forward as his greatest season.

Wrestling with an initially overweight, 1991’s underpowered V12 McLaren Honda car, the Brazilian saw off the coming force of rivals old and new to cement his racing legacy.

As well as being a landmark Macca based on its results, the MP4/6 is the only V12 car in F1 history to win a world title and the final champion effort to use a manual gearbox.

2 Ayrton Senna McLaren 1991 French Grand Prix Magny-Cours

Taking in the opposition during a challenging season

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However, it wasn’t 1991’s best car – that was the Williams FW14. Much of what defines that year of Senna/McLaren brilliance is the fact they were fighting what should have been a losing battle against Grove and Nigel Mansell, yet still prevailed.

This was down to both the drivers’ genius, the team optimising what it had and Honda’s inspired push to keep giving Senna what he wanted.

As the Brazilian’s 1991 race engineer James Robinson tells Motor Sport: “He only had to use 1% of his mental capacity to drive the car” focusing the rest on helping the team dig deep to keep itself in the battle.

Speaking three decades on, he and former McLaren designer Matthew Jeffreys – part of the design team led by Neil Oatley – recall the fascinating story of a hugely significant year in grand prix racing.

Similar to Red Bull in 2024, 1991 was the year McLaren found itself fighting rising challengers after enjoying a number of dominant seasons.

Williams had signed hotshot young designer Adrian Newey to design 1991’s FW14, and its Renault V10 was coming on song – plus there was Mansell behind the wheel to grab the matter by the scruff of the neck.

Honda’s answer was to come up with a V12 engine. More weight but, its engineers hoped, more power too – starting at 725bhp, would it be enough to make the scaling-up worth it? It meant a comprehensive redesign of Senna’s previous championship winners.

“We almost had to start again, because of the bigger engine V12 and the increased fuel capacity,” remembers Jeffreys, who now produces painstakingly detailed engineering drawings of famous F1 cars – including those he helped design.

“The engine’s heavier, it’s thirstier so it needs more fuel, potentially the car’s going to get longer. Though we seemed a lot more worried about wheelbase length in those days than perhaps we needed to be, when you look at the length of F1 cars now!

“[How] centre of gravity [is affected] is also is very important – both with height especially but also terms of the fore-and-aft weight distribution. It just presents a different number of packaging and dynamics requirements.

“The radiators have to be bigger because the engine is producing more heat, etc.”

Ayrton Senna McLaren 1991 French Grand Prix Magny-Cours

Senna searches for more power

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For Senna, who loved the Honda V10 with which had won his two previous world championships, moving to a V12 was hard to accept.

“I think people like Ayrton were very sceptical, and we were too,” Jeffreys remembers. “It’s all very well having great top end power, but if the power curve and the torque curve are too peaky, then the driver can’t use it effectively [in low and mid-speed corners].”

“The car understeered like a pig, which was no good for Ayrton”

It wasn’t just a lack of response under his right foot that was rankling either.

“The car understeered like a pig, which was no good at all for Ayrton, he hated that aspect,” says Robinson.

The car was hardly without its virtues though. A rethink in monocoque and bodywork design meant that Jeffreys and co were able to come up with a machine they hoped would be better balanced.

“The previous [McLaren] monocoques, we had quite a few sharp edges where the natural corners happen – but with flat panels in between, to maintain torsional stiffness,” he says.

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“[But] on the MP4/6, the two surfaces that run from the front to the back of the monocoque are on a curve, they don’t actually change direction with an angle – it’s a flowing surface.

“We wanted to reduce the number of changes of angles that the [carbon-]fibres had to go around, to improve torsional stiffness.”

Not that this initially appeased Senna or his team-mate Gerhard Berger much.

“They thought the power wasn’t enough,” recalls Jeffreys. “And Honda said ‘We’re just not running it at full power, we would prefer the reliability.’

“That was it, it wasn’t powerful enough, and it was heavy. So there was concern, even though we’d won the first four races.”

Despite Senna making a clean sweep of 1991’s opening quartet, all at Woking could see the storm on the horizon.

“The Williams was a far better car,” says Robinson. “But they had a major gearbox problem.

“They didn’t know what it was. They were smashing gears. It turned out they were selecting two gears at the same time, because of their transverse box…”

Nigel Mansell carries Ayrton Senna at 1991 British Grand Prix

McLaren’s lead driver ran out of fuel twice in 1991

Senna would go out of ‘91’s fifth round at Canada with electrical issues, the first of five races without a victory.

Before that race he led the championship with 40 points, his closest challenger being Ferrari’s Alain Prost on 11 points, with Mansell on six points.

After the five-race lean spell, he had 51 points to Mansell’s 43, the Brit taking a hat-trick of victories in the meantime.

Among reliability and weight issues, Senna’s McLaren’s colleagues remember he would test their nerves with some daredevil lack-of-economy runs too.

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“We knew we had a fight on our hands,” remembers Jeffreys. “A number of things started to creep in – we also had problems with fuel reading, in getting an accurate fuel measurement.”

“He would use more fuel than he was allowed to use early on in the race and say, ‘Well, the race is at the beginning. At the end, I can back off and save it,’” says Robinson.

“So he would go very negative on the meter, which would have us all on the pitwall screaming at him, and he’d just go: ‘Don’t worry, I can get it back – but in two races [Silverstone and Hockenheim] he didn’t, and ran out!”

Things started to come back together in Hungary when Senna was once more on top of the rostrum – but it wasn’t easy getting there.

“The car wasn’t brilliant,” says Robinson. “And one thing I had not been used to – Henri Durand [who moved to McLaren from Ferrari for 1991], who had done the aero on it, was very much: ‘I’ve designed this car, this car is perfect.’

“And I’m going: ‘No, we need to be developing the car. We need to find two-tenths a weekend.’ And he was adamant: ‘No, no, this is the car. We can’t change anything. That’s the best car I’ve done.’

Ayrton Senna crosses the line to win the 1991 Hungarian Grand Prix

Hungary win got Senna title fight back on track

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“There was a bit of a fight within the team and all of us about trying to improve the car, because you’ve got Ayrton ringing you up, banging on each weekend.

“[In contrast] Honda would do that [improve their product]. They would come every weekend and say: ‘Mr Senna, we have found 10 horsepower’, or whatever it was. He’d demand to see the graphs and ask where the power was on the torque curve.

“Martin [Whitmarsh] had wanted Henri because he liked Ferrari’s front wing,” says Jeffreys. “But it turned out that was done by someone else at Ferrari!”

From the archive

The eventually-redesigned MP4/6 which Senna took to victory in Hungary managed to combine its more powerful engine (now 780bhp) with a new, lightweight monocoque. Jeffreys explains the process.

“The only way you can really do it is to look at everything,” he says. “And if you can take 2 or 3% off everything, then that’s quite a lot.

“It’s very difficult to find big chunks, where you can say ‘Oh, that could be half the size of that.’

“And you have to make things more efficient as well – which affects your thinking in terms of the design.

“When were were looking at the dampers, it struck me that the line where nose cone joins to the rest of the body cuts across the Marlboro chevron, meaning George [Langhorn] in the paint shop had to paint two little triangles of Marlboro red over the nose.

“It’s one of the qualities of McLaren, the ability to develop the car”

“So we decided to split the join of the bodywork so it follows the line of the [cigarette design] chevron.

“It’s just how your brain works when you’re looking for the efficiency of everything.”

The changes made the difference – in the six races from Hungary to Japan, Senna would score two wins and three second places to clinch the championship with a race in hand before the season close.

Managing to dig deep when he needed it most – with the help of a brilliant team – it’s perhaps Senna’s greatest title triumph.

“We produced more ‘6’s than we would normally have done in a season,” says Jeffreys.

Grand Prix of the United States

Senna’s race engineer Robinson said the Brazilian had an unrivalled racing intelligence

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“We had to keep finding new ways to be competitive. We were aware we had to shed weight and increase power on both sides.”

“I think it’s one of the qualities of McLaren, the ability to develop the car,” says Robinson.

“That’s McLaren’s depth. That was Ron, if people got a bit sidelined, he’d put them on different projects. Other teams would have let go of them. But you could bring them back in if needed.”

As ever though, Senna was a driving force.

“I’d worked with Nelson Piquet at Williams, so was used to the technical, methodical approach, but with Ayrton it was an extreme level,” remembers Robinson.

“The thing is that confidence circle goes around. If you’ve not got confidence in your driver and your driver hasn’t got confidence in you as an engineer or in your team or whatever, then the snowball doesn’t roll.

“The difference with Ayrton was that driving the car was 1% of his effort. His mental capacity was what gave him the difference. He knew what was going on the whole time.”