It was bordering on farce at Silverstone: the FIA ban on off-throttle blowing of diffusers had completely collapsed by Saturday morning of British Grand Prix weekend. Delegations of angry engineers and team principals had trailed back and forth to FIA technical delegate Charlie Whiting's office throughout the previous couple of days, each explaining why the latest in an ever-changing FIA position would unfairly and adversely affect them.
By Saturday lunchtime we had the black comedy of Whiting asking all the teams if they could agree to have the rules of the previous race – i.e., with off-throttle blowing allowed – applied for the balance of the season. In other words, “Could you all please agree to have it the way it was before we tried to change it?” It was duly voted through and so for the remainder of the year full off-throttle exhaust blowing of diffusers is once more permitted, having been restricted only at Silverstone. For 2012 though, a newly prescribed zone for the exhaust will ensure it physically cannot blow onto the diffuser – thereby effectively outlawing all blowing of diffusers, on throttle or off.
How did we get here? Using the exhaust gas to energize airflow over the diffuser to increase downforce is not a new idea; it was first used by the Renault Formula 1 team in 1983 and has moved into and out of fashion on a regular basis ever since, according to the geometries of the diffuser and bodywork allowed by the regulations. But its current vogue began with the 2010 Red Bull RB6 (RIGHT). The team had tried disguising it when it first appeared at the final preseason test, with stick-on exhaust outlets in their conventional place and the real exhausts way lower in the car's dark, shadowy nether regions. But that just alerted the opposition: why had Red Bull gone to all that trouble?
By midseason, all the serious teams had their own blown diffusers. But the sudden increase in grip you got when you floored the throttle just made the off-throttle part of the corner feel all the more unstable. There was more grip to be found there…if only the exhaust could continue to blow even when the driver lifted his right foot.
Hence the advent of off-throttle blowing: keep the engine throttles open even as the accelerator is lifted, reducing the torque to the wheels by cutting the spark and fuel, leaving the engine to pump air through the exhaust onto the diffuser – hey presto, off-throttle blowing. All the front-running teams had it by the second half of last year and the governing body had full knowledge of that.
But for this year, with a winter to think and work on it, the systems became more extreme. Mercedes and Ferrari introduced “hot blowing” off-throttle whereby the engine throttle still remained open but some fuel was introduced. With no spark, it still didn't ignite within the engine but did so as it reached the hot exhaust, increasing the velocity of the flow to the diffuser.
Renault had it too, but it wasn't used on the Red Bull-Renaults since RBR found it increased their already marginal rear tire temperatures too much. Extreme engine maps – of both hot and cold blowing – giving 100-percent throttle opening throughout the lap were devised for use in qualifying. But these couldn't be used in the race as the ignition retardation would ultimately cause a failure and the fuel consumption would be too high.
It was Williams – with an engine supplier (Cosworth) unwilling to develop a hot-blowing map for reasons of cost and reliability – that first questioned the FIA about whether a) having separate maps for qualifying and for racing contravened the parc ferme regulations, and b) whether the throttles were being used primarily as an aerodynamic device. Williams was surprised at just how enthusiastically the FIA took up these points – almost as if it was pushing against an open door. Ferrari said nothing publicly but in the Technical Working Group meetings was highly supportive of the FIA's intention to outlaw off-throttle blowing. What no one could fathom was Mercedes' attitude but many thought they detected the politically savvy hand of Ross Brawn here. As ever, competitive agendas, politics and governance all interweaved, and trying to unstitch each of them is an impossible task.
There was definitely a feeling among Red Bull's opposition that the RB7 was gaining more than anyone else from this technology. They believed that the extra lap time the car would invariably find in Q3 and the way the car would revert to a more normal performance in the race was evidence of an extreme and more effective off-throttle blowing map for qualifying. That belief would certainly have provided a motive to the opposition for trying to have the whole thing switched off.
Except Red Bull wasn't even using hot-blowing! No one believed this before Silverstone, but they do now. RBR has a somewhat unreliable KERS system that isn't used until Q3 and then only sparingly in the race. It also has an aerodynamic profile that makes it less sensitive to the higher ride heights of qualifying when the cars are near-empty of fuel.
So, in the brief window that Silverstone provided – showing limited off-throttle blowing (fueling off-throttle from only four cylinders and a maximum throttle opening of 20 percent at 18,000rpm down to 10 percent at 12,000rpm) – Red Bull's qualifying advantage over everyone but Ferrari was much as it had always been. The Ferrari picture was muddied by an extensive and effective aerodynamic upgrade that gave it enough downforce to get heat into the hard tires for the first time. What these rules did reveal was that the McLaren MP4-26 seems to rely heavily on off-throttle blowing to find a good window of setup; just as the car was suddenly switched on at the start of the season by an RB7-like exhaust, so it seemed switched off at Silverstone when off-throttle blowing was restricted.
Two weeks later, it had all blown over and, in the meantime, F1 had revealed a lot about its inner workings and those of the various leading cars. Farcical, yes, but ultimately fascinating for us observers.