Formula 1 bosses reverse decision in exhaust row
Formula 1 bosses have done a U-turn on a rule change that has caused a row between Red Bull and McLaren at the British Grand Prix.
Just before practice on Saturday, governing body the FIA reversed a rule change that was introduced on Friday following pressure from Red Bull.
The world champions believe the rules now put them at a disadvantage but have accepted it for this race.
There will be a further change for the next race if teams unanimously agree.
A see-saw of rule changes in the course of the weekend, made in an attempt to be equitable, left all the teams frustrated - but a situation that had developed into a full-blown row was cooled by compromises by the FIA and Red Bull on Saturday.
Red Bull team principal Christian Horner agreed to accept the final rule change made by FIA race director Charlie Whiting on Saturday morning - which he says puts his team at a disadvantage - in return for a further change being considered after the British Grand Prix.
A statement released by the FIA on Saturday said that the rules would revert to what they had been at the European Grand Prix two weeks ago "if the teams are in unanimous agreement".
If it is agreed, that will mean that the technology the FIA is trying to ban - so-called off-throttle blowing of the diffuser - would remain allowed for the rest of the season, but that teams will not be allowed to change their engine settings between qualifying and the race.
The teams are meeting again at 1030 BST on Sunday to try to reach unanimity.
Mercedes team principal Ross Brawn said: "The meeting this morning was held in constructive fashion bit there were differences of opinion and different teams went away to consider their positions.
"I hope we will find a solution but I really don't know where we will be tomorrow."
He added: "it's very difficult when you make a rule change like that in the middle of the season to be equitable."
BBC Sport understands that 10 of the 12 teams have already agreed to the change, with only Williams and Sauber still to be convinced.
Horner said: "It's a very difficult subject and putting yourself in Charlie Whiting's shoes it's very difficult.
"We all ran reliably in Valencia and it seems the most sensible thing to go back to that.
"The problem is that (what has been done for Silverstone) is effectively a rule change in the middle of the season.
"We're running in a compromised situation, and we've accepted that for this weekend as long as there is a solution for Germany."
The compromise was arrived at during an emergency meeting between Whiting and the teams.
What is clear is that the row has left a sour taste that has overshadowed the on-track action at the British Grand Prix.
Horner and McLaren team principal Martin Whitmarsh had engaged in a public row on the issue during a news conference on Friday afternoon.
Following that, there were further meetings between teams and Whiting, who then issued a new rule with half an hour to go before Saturday morning practice.
Off-throttle blowing of diffusers has become a key technology in F1 in the last year.
This is where teams blow exhaust gases over the rear floor of the car even when the driver is not pressing the accelerator, smoothing the airflow and therefore increasing downforce and grip.
The FIA had ruled that teams would be allowed from the British Grand Prix no more than 10% throttle opening when the drivers were not pressing the accelerator.
Mercedes argued that they should be allowed to introduce some fuel into the engine on what is known as 'the over-run' - when the car was braking - on the basis that they had been allowed this two years previously to enhance reliability.
Although the engine is reduced to running on only four of its eight cylinders at this point, this will inevitably lead to some blowing of the diffuser, and therefore the creation of some downforce.
Renault, by contrast, does not fuel its engine on the over-run and argued that it should be allowed to compensate by opening the throttles to a specific amount, something it says it has always done to ensure reliability.
The FIA initially accepted Renault's argument and the French company will now be allowed to run its engines on 50% throttle when the driver is not pressing the accelerator.
This decision was then reversed on Saturday morning.
BBC F1 pit-lane reporter Ted Kravitz said: "Charlie Whiting told me: 'Don't be fooled by anyone telling you that Mercedes are going to get an advantage out of this, because they are not.' It's just that Red Bull perceive they are at a disadvantage."
BBC 5 live analyst Anthony Davidson said: "The teams are not looking for equality, not at all. They are looking for an advantage."
Whitmarsh said ahead of McLaren struggling in qualifying, with Jenson Button fifth and Lewis Hamilton 10th: "I think everyone is going to be running the same thing. There is a limitation on the amount of throttle that is allowed.
"Those that end up at the front will probably end up happy and those that are disadvantaged won't be, and Ferrari seemed to come out of the meeting more smiling than some others. It all sounds very small but they affect many parts on the car. Some people will luck in and some won't."