Tag Archives: Diffusers

Banning off-throttle blown diffusers and the FIA’s (un)intentional attempt to create a silly circus

So the FIA is at it yet again, and this time their decision is going to directly affect the racing on the track, as opposed to determining when and where F1 will race.  Now the hot button issue is the teams’ use of off-throttle blown diffusers and the FIA’s decision to ban them midseason, just in time for the British Grand Prix.  To clarify, here’s a quick background on diffusers and their storied technical history in the past several years.

A diffuser is a shaped section of the rear underbody of a car that manipulates its aerodynamic properties.  A diffuser increases the velocity of the air exiting underneath the car, which in turn reduces pressure, and the subsequent effect is the slower velocity/higher pressure air flowing above the car generates a downward pressure effect on the car, creating the mystical yet very tangible and beneficial aerodynamic principle of downforce.  In its simplest terms, think of a diffuser as an inverted wing installed on the bottomside of a car, and the faster the car goes, the more atmospheric pressure presses downward on the car, ultimately improving its grip and handling.

Now that’s a rear end only an F1 fan could love.

Starting last year, Red Bull Chief Technical Officer Adrian Newey designed the RB6 so that the exhaust gases are discharged from the bottom undercarriage of the car, essentially dumping the hot gases into the airstream flowing underneath the car and out through the diffuser.  The net result from the artificially energized air flow was an increase in downforce without any increase in drag, which is the holy grail for aerodynamic engineers.

Fast forward to 2011, and Red Bull took their design a step further by “mapping” the engine to leave the throttle slightly open to blow exhaust gas into the diffuser even when the driver is off the throttle pedal, hence the term off-throttle blown diffuser.  Not to be left behind, the other teams responded with their own off-throttle diffuser systems, with only a small minority sticking with a “cold blowing” diffuser design.

One of the general design doctrines in F1 is the strict ban on moveable aerodynamic devices other than the ones permitted by the regulations.  The FIA chose to interpret the use of off throttle diffusers as in violation of this rule by declaring that the engine was now a moveable aerodynamic device because of use of exhaust gases to influence aerodynamics, specifically during the off-throttle stage.  Clever buggers.

After several months of debate and a meeting by the FIA’s Technical Working Group, the decision was made to ban the use of engine mapping to artificially blow exhaust gases during the off-throttle stage, with the British Grand Prix set as the deadline for the teams to modify their designs.  Several of the teams using the innovative diffuser design in conjunction with the off-throttle engine mapping, Renault and Red Bull in particular, voiced their dissenting opinions with the FIA’s decision, with other teams either supporting the decision or staying silent on the matter.  Point is, the FIA decided to change the rules of the game mid-season, which could potentially lead to a dramatic change in the teams’ performance for the remainder of the season.  Imagine the NBA deciding to shorten the shot clock by tw0 seconds or MLB deciding to shrink the size of a baseball midseason.  Does that sound fair to you?  It’s not an apples to apples comparison, but hopefully you get the gist.

Skeptics will claim that the FIA is trying to manipulate the outcome of both Championships this season, in particular because Red Bull is the team that pioneered the off-throttle diffuser design and has fielded the strongest car on the grid for the past two seasons.  Pragmatists will claim that the FIA is simply executing their duty to ensure the teams adhere to the technical design regulations.  Personally speaking, it seems a little absurd to force teams to come up with new designs midseason, especially considering the current trend in F1 to reduce costs in the area of car design and testing.  But if Ferrari manages to benefit from the FIA’s decision, then who cares?  Forza, and off to Valencia!

MP

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