FIA's Charlie Whiting says some teams will lose 0.5s per lap to mapping clampdown

With teams bracing themselves for a major change in the way they use blown diffusers over the next two races, FIA race director Charlie Whiting believes the first step in Valencia this weekend may well have an effect on the competitiveness of some teams.

"I think it is impossible for us to quantify it, but I have heard during discussions that the most extreme maps may give you half a second per lap," explained Whiting. "That is what I hear, but it is not something we are concerned with."

Whiting has been surprised about what some teams have been doing with their engine maps - and said that was the motivation for him acting now in both the ECU restriction and the ban on the off-throttle use of blown diffusers from the British GP.

"Everybody is doing this to an extent. Some are doing it more extremely than others and you could argue some are doing it better than others, but everyone is doing it to some degree. There are real extremes out there but I am not at liberty to say how extreme, but I have been quite surprised."

Responding to questions about why the FIA had chosen to act now, Whiting said: "All we are doing is making sure how we think a car should be run legally.

"It is not for us to say whether or not a certain team would be more penalised than others. It just depends how extreme they are, but I have seen evidence of maps from teams that are extremely extreme and it is not confined to one team, I can assure you.

"We know exhaust gases have an influence on aerodynamic performance of the car, we accept that, but the point is that the designs should minimise the effect they have on the car, they should not attempt to use the exhaust for a completely different reason.

"It is a bit like mass dampers, where its first use was fairly benign when it came to aerodynamics. But the more it got developed the more extreme the designs were. There were four, five, six mass dampers on the car, and they were clearly being used for aero reasons. These things escalate as we all know to the point where something has to be done. The mass damper was the same example of the approach we have taken."

He added: "We haven't made any changes to the rules; all we are doing is stopping people breaking the rules."

Whiting said that discussions were still taking place with teams about the extent to which the throttle can remain open from the British GP - with teams requiring different levels pending on the design of their engine.

"There are a few elements that we have not yet finalised," he said. "We have had meetings with a couple of engine manufacturers, as we only want to target this one particular area for what we feel is the illegal use of engine maps for aero reasons.

"We don't want to influence the perfectly legitimate systems on the cars like engine braking for example, we are happy for them to use it but we don't want it to be abused.

"If a driver comes off the throttle, we are saying that the throttles can be 10 per cent opened at 12,000rpm and 20 per cent open at 18,000rpm. One engine manufacturer is asking for a little bit more and for what appear to be genuine reasons.

"We have the ability to go back to 2009 and look at the maps and records we have and everything. We can refer back to those - if they needed 28 per cent of throttle at 18,000rpm back then it is perfectly legitimate - so that would appear to be a perfectly reasonable request. "

Whiting also revealed that if the FIA had not seen through on its decision to clamp down on the issue now, then there would likely have been a protest from a team about the matter.

"I think we got close to a protest in Monaco and I gave the team the assurance that we were going to follow it up and we were not going to give it up," he said. "They were concerned about us changing our mind and letting it go for the rest of the season.

"I have already emphasised to the teams that that option is open to them. Everyone is doing to the same degree the same thing, but we need to be sensible about it and approach it in a pragmatic way to get the situation under control."