McLaren team principal Martin Whitmarsh claims the FIA has altered the off-throttle exhaust-blown diffuser ban to satisfy Renault Sport F1 and Red Bull.
The ban, which took effect for the British Grand Prix, limits off-throttle blowing to just 10%, however according to Whitmarsh, the regulations changed on Friday after the aforementioned parties protested the limit.
“We learnt halfway through the session that Christian [Horner] hadn’t lost as much as we had expected him too,” he said during the FIA press conference. “The rules are slightly fluid and seem to change by the hour at the moment, so we’re still learning [how much downforce we’ve lost].
“It’s not a criticism of Red Bull, they’ve got to get the best they can get out of the situation, but we were all a little surprised when we were told the regulations had been changed halfway through FP1.
“That puts us, and I’m sure many teams this weekend on the back-foot and we’re trying to cope with that at the moment.”
Whitmarsh and Horner got into a heated debate over the matter as the former looked to explain the change as he understands it.
“The expectation was that when you’re off the throttle then the engine throttle would be closed, but there has been a negotiation and as I understand Renault’s throttles are 50% open under braking, that’s probably not what most of us expected,” explained Whitmarsh.
“It’s been a bit of a revelation that we’ve gathered today.”
As we understand it, the FIA has allowed Renault, and only Renault to run 50% cold-blowing when off the throttle, whilst Mercedes and others have been allowed to continue ‘fired overrun’ or hot-blowing to 10%, which Horner suggested was equal to, if not more powerful than the 50% permitted to Renault.
Renault cannot run ‘fired overrun’ for reliability issues because it would cause the engine to overheat, which is why the FIA has allowed different regulations for different engines.
Tony Fernandes, team principal of Team Lotus, described the situation as a ‘shambles’ and called for clearer regulations.
