Why Red Bull has had a diffuser boost

The action in the press conference, as Christian Horner and Martin Whitmarsh argued about the latest technical directive regarding blowing diffusers, comfortably overshadowed that on the track where only slivers of significant form emerged from the gloom of two rain-afflicted Friday practice sessions.

Intermediates were the tyres of choice for the field during both the morning and the afternoon and the timesheets - particularly those of the second free practice session - reflected only who was best placed in the dying seconds of the session to take fullest advantage of a drying track. That happened to be Felipe Massa in the afternoon, but nothing too much should be read into that.

Horner and Whitmarsh had some choice words for each other © sutton-images.com

On the few occasions in which it was on the track, the Red Bull appeared still to be by far the fastest car, Mark Webber heading the FP1 times and also lapping fastest when he was running in FP2. The combination of Michael Schumacher and Mercedes also appeared competitive in these conditions, as was the case in Canada a few weeks ago.

The current expectation is that both qualifying and the race will be held in dry conditions and only then will we know definitively what the effect of the latest ruling on off-throttle blown diffusers will be. That ruling was actually changed on the eve of FP2 after extensive consultations between FIA technical delegate Charlie Whiting and Renault Sport. This was at the centre of the heated post-practice discussion between Horner and Whitmarsh and of an animated pitlane conversation between Whitmarsh and Ferrari team boss Stefano Domenicali.

Whitmarsh was angered to hear that the Renault engine as used by Red Bull had been allowed to run with its throttles up to 50 per cent open while the drivers were off-throttle, whereas the previous directive had been a blanket restriction of 20 per cent (at 18,000rpm, declining to 10 per cent at 12,000rpm) for everyone. But, as Horner was quick to point out, this was only to even out the fact that the Mercedes engine had been allowed to retain firing from four of the eight cylinders when off-throttle. This was agreed between Whiting and Mercedes in between the Valencia and Silverstone events.

AUTOSPORT understands that as a protest against the FIA concession on the Renault engine, both McLaren and Ferrari ran their engines in Friday FP2 with the same 50 per cent throttle openings as Renault. This argument could run for some time yet.

Mercedes has argued through historical precedence - the FIA has detailed data on file for all the engines in 2009 spec - it has used off-throttle fuelling as part of its engine's operating strategy since before the advent of off-throttle blown diffusers.

Renault has used the same logic in showing it ran up to 50 per cent open throttles (when the driver was off-throttle) since pre-blown diffuser times. Mercedes has argued that it needs the off-throttle fuelling to relieve crankcase pressure, Renault that it needs to keep the throttle this far open when the driver has released the accelerator in order to prevent its exhaust valves from overheating.

Whether the two allowances accurately equate to each other is the real bone of contention, but it's clear that had Renault not pressed its case, and only the Mercedes concession been approved, then the Red Bull's advantage would certainly have been trimmed back. That would appear to be less likely now, though the matter may not be over yet.

Read nothing into Massa's pace-setting time in FP2 © LAT

The nature of Silverstone's circuit, with a succession of the high-speed, long duration bends at which the Red Bull RB7 naturally excels, will probably only cloud the issue further.

McLaren spent the Friday sessions comparing its new rear wing - with a more aggressive DRS stall characteristic - with the old one, but the conditions made arriving at a firm conclusion difficult. This is a less than ideal start for the team's preparations to the weekend.

Ferrari too has a succession of aerodynamic upgrades at Silverstone. It was consistently among the fastest in sector one - which includes heavy braking for turns three and four and hard acceleration from low speeds out of four, the sort of demands that traditionally suits its car - but less convincing in the high-speed aero sections of sector three.

In short, it's very difficult to see past Red Bull again and if anyone was hoping that the latest instalment of the exhaust sage would find and neutralise a silver bullet of its performance, they will likely be disappointed.