Ross Brawn says existing Formula 1 engine suppliers know “they can’t shut the door” on new manufacturers but concedes a compromise would have to be negotiated for a new engine maker to join the grid in 2021.

F1’s managing director of motorsports had been hit by the admission that potentially no new constructors’ would be joining the sport ahead of the 2021 rules overhaul, which led to the existing manufacturers pressuring rule-makers to retain the current engine technical regulations.

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Brawn insists adjustments will still be made to improve “the sporting direction” – rumoured to be more standardised parts and trying to improve the noise from the power units – but concedes the current F1 engine standoff has been eased with no serious interest from new manufacturers.

“The drawbridge has been pulled up and the existing suppliers don’t want anyone else to come in,” Brawn told “We have found a compromise. There are regulations coming out which would mean new entrants will get support from existing entrants. There will be components and technology which will have to be shared if it is requested.

“It is not quite such a radical change that we were proposing, but still quite a good step in the right direction and there are some nice changes to the way the driver has to manage the engine, which I think goes a long way in the sporting direction.

“There has been a recognition from the existing manufacturers that they can’t shut the door behind them.

“If we start to get serious interest from another manufacturer or supplier, they have to cooperate to find ways of helping that manufacturer come into F1.”

All four of the existing F1 power unit manufacturers – Mercedes, Ferrari, Renault and Honda – have confirmed its intentions to stay in the sport beyond 2021 having taken a key role in shaping the future rules.

A mooted engine entry run and badged by Aston Martin with technical support from Cosworth had been reported but the bid has subsided due to the costs and development required to be competitive in 2021.