LONDON • Engine makers will have to share some parts and technology with new entrants under proposed rule changes for 2021, Formula One's managing director for motor sports, Ross Brawn, announced on Friday.
Mercedes, Ferrari, Renault and Honda between them supply the 10 teams and there are no newcomers set to join them in two years' time.
"The drawbridge has been pulled up and the existing suppliers don't want anyone else to come in," said Brawn.
But the former Honda and Mercedes team boss, and technical director of Ferrari, revealed a compromise had been found to lower the barriers to entry. He said: "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.
"There has been a recognition from 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."
F1's post-2020 vision set out last April originally envisaged cheaper, simpler engines to encourage new manufacturers to enter the sport, with Porsche and Aston Martin attending some meetings.
However, Aston Martin chief executive Andy Palmer told Reuters last month that his company had lost interest after the sport backtracked on those plans.
The four suppliers have been wary of incurring significant costs in engine development just as the power gaps are closing.
Though Brawn acknowledged the proposal was "not quite a radical change", it was still "quite a good step" in the right direction.
He said that next season's changes, with cars boasting bigger, wider and simpler front wings, should promote closer racing, while the sport is on course for a budget cap for 2021.
He said: "Until the cars run, we don't know what solutions they have made, but from predictions, we're achieving about 20 per cent improvement."