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FIA: Ban on Aggressive off-throttle Engine maps

with 20 comments


Teams have been adopting exhaust blown diffusers (EBD) since last year and in 2011 every team has exploited the exhaust to some extent to help drive airflow through the diffuser. As I have explained in previous posts on the subject (, the problem with EBDs is that they create downforce dependant on throttle position, so as the driver lifts off the throttle pedal going into a turn, the exhaust flow slows down and reduced the downforce effect, just at the point the driver needs it for cornering.

If a team want to really exploit the benefits of an EBD then they need to resolve this off-throttle problem. Last year Red Bull exploited a different mapping of the engine when off throttle (see ). By retarding the ignition when the driver lifts off, the fuel is no longer burnt inside a closed combustion chamber, but instead the fuel and air burn in the exhaust pipe, the expandign gasses blow out of the exhaust exit as though the engine is running . This creates a more constant flow of exhaust gasses between on and off throttle. The problem here is that the mapping uses more fuel and creates excessive heat in the exhaust pipe and at the exhaust valve. Renault reported that both Red Bull and Renault used 10% more fuel in Melbourne compared to last year, most likely due to these off-throttle mappings.

With these off throttle mappings the fuel burns in the exhaust pipe, not the cylinder


As the engine suppliers have become increasingly comfortable with the heating effect of these off throttle mappings, teams have been able to use more of this effect in the race. One of Red Bulls advantages this year according to McLaren is their use of aggressive engine maps for downforce. At the Turkish GP several people pointed out the engine note on the overrun on Alonso’s Ferrari during FP2. Teams have clearly started to drive the engine quite hard when off throttle, to keep the diffuser fed with a constant exhaust flow.

Now the FIA have stepped in to limit this effect. Although initially scheduled to be in effect from this weekends Spanish GP the change will now take effect after Canada. This clarification is based on Charlie Whitings changing opinion of how these mappings are used. At first some mapping was allowed, but these increasingly aggressive and fuel hungry mappings are changing the engines primary purpose. Effectively when off throttle the engine is being used purely to drive the aerodynamics, this contradicts the regulation on movable aerodynamic devices. Although this is a vague interpretation it can be justified.

What is now required is that the engines throttles (at the inlet manifold) must be closed to 10% of their maximum opening when the driver lifts off the throttle pedal. Unlike in most road cars, in an F1 car the engines throttles are not under the direct control of the driver via the pedal. The throttle pedal is instead the drivers method to request power\torque, the cars SECU then controls the level of throttle required to meet the drivers request. So as the driver lifts off the throttle pedal, he is no longer requesting power\torque and therefore the throttles should close. what happens with these EBD mappings is that the throttles remain open, Fuel continues to flow then the delayed spark from the plugs sends the burning charge down the exhaust pipe.

Now with the throttle closed to 10%, the amount of fuel that can be burnt will be limited and thus the blown effect will be reduced. so drivers see will a bigger variation in downforce as they modulate the throttle pedal, making the car less predictable to drive.

Blowing the exhaust under the 5cm of outer floor (yellow) will be most penalised by the ban


All teams will be affected to some extent, however the more aggressive that teams have been with the exhaust position relative to the floor, then the greater they will be affected. From the start of the season Red Bull, Ferrari and McLaren have blown the exhaust at the outer 5cm of diffuser. this area is allowed to to be open and bow the exhaust gas under the diffuser for greater downforce. these designs will be most greatly affected by the clarification. Renaults Front Exit exhaust is also likely to be a victim of the change. Many teams have been developing Red Bull Style outer-5cm EBDs, such as: Williams, Lotus, Virgin, Sauber, While Mercedes are rumoured to be adopting a front exit exhaust. These may to need be shelved after Canada, in order to employ a less aggressive EBD.

Written by scarbsf1

May 19, 2011 at 12:09 pm

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20 Responses

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  1. Surely springing a surprise change in regulations which will require major redesigns of 90% of the cars on the grid is completely contradictory to the FIA’s own commitment to reduce spending in F1?

    Stephen Hopkinson

    May 19, 2011 at 12:29 pm

  2. Is it possible to do the opposite of an EBD say a Negative EBD where the diffuser becomes less effective when blown and reduces down-force and possibly increasing straight line speed? Or would this simply not work/be illegal?


    May 19, 2011 at 12:48 pm

  3. I must admit that I was a little disappointed that the FIA backed down from imposing this change immediately. I think the consequences would be fascinating.


    May 19, 2011 at 1:35 pm

  4. A lot of road cars now use drive-by-wire throttle pedals. They’re easier to place and easier to route electronic cables than mechanical throttle cables, generally more reliable and it allows the ECU to optimize fuel economy and drivability.

    I believe Ford introduced drive-by-wire on the original Focus C-Max in 2004 and then adopted them on the Mk2 Focus in 2005. Toyota have had a lot of trouble over the last year with ‘unexpected acceleration’, which – because they are drive by wire – kicked off an investigation by NASA into the electronics and software. Toyota have recalled cars for sticking throttle pedals and floor mats fouling the pedal.

    I have a Prius, which makes continuous decisions as to how to vary engine load, speed, and the speed and torque of both drive motors, depending on the road conditions, battery charge status, and driver’s throttle input. Without drive-by-wire the driver would have to make those decisions. (It’s no wonder Toyota were not interested in KERS, the Prius had already been out for 10 years and is far more sophisticated.)

    Mike Dimmick

    May 19, 2011 at 3:31 pm

    • A quick observation; I commute 90+ miles each day on very flat, boring highway. I never had a working cruise control growing up so I don’t use them now, but I am quite good at maintaining a constant speed. Anyway, I talked to our local dealer techs and to Toyota about issues with ‘unexpected acceleration’ because I have noticed that my car will very subtly accelerate and pick up a few mph. Then, a few minutes later, will very subtly decelerate and loose a few mph. A passenger might not notice it, but when you spend 1.5 hours a day in your car, you notice it. It’s just a sudden gentle push, or gentle brake. Just enough to make a relaxed head rock backward or forward.

      I mentioned this to them about three years ago. Even took a tech for a ride along who said they could feel what I was talking about, but said it was/is not an issue.

      Luckily, my car has standard transmission, so even if the car took off I could just drop it into neutral.

      Just an observation.


      May 20, 2011 at 1:41 pm

  5. “I believe Ford introduced drive-by-wire on the original Focus C-Max in 2004 and then adopted them on the Mk2 Focus in 2005.”

    BMW’s 850i, introduced in 1991, had throttle-by-wire on the M70B50 V-12 engine. I owned one for 11 years and never had any trouble with it. There were two “DK Motors” that that controlled the throttles, one for each cylinder bank. If one bank had a problem, the car could downmode to “limp home mode,” and run on six cylinders.

    Pretty high tech stuff for a production car built 20 years ago.


    May 19, 2011 at 5:29 pm

  6. [...] [...]

  7. Electronic throttle control (ETC) has been around for a long time.
    BWM first used it in 1988 on the 7-series.
    Even my 2002 BMW E46 325ci has electronic throttle control.


    May 19, 2011 at 7:21 pm

  8. Could the teams no change the software so that as the brake is pressed the engine is retarded?So if the driver goes into a corner with his foot still flat on the throttle but on the brakes, the throttle position is open so maximum exhaust flow is allowed.

    Ross Dixon

    May 19, 2011 at 8:04 pm

  9. [...] big engineering explanations from me since I’m hopeless when it comes to tech stuff (check this article by Scarbs for a superb technical explanation), but basically what EBDs (Exhaust Blown Diffusers) are is [...]

  10. scarbs, i’m curious as to how the teams are (currently) running these systems legally with regards to the following rule:

    5.5.3 The minimum and maximum throttle pedal travel positions must correspond to the engine throttle minimum
    (nominal idle) and maximum open positions

    So then if the drivers foot is off the throttle – the engine throttles must be at minimum, no?

    Kyle Reimer

    May 20, 2011 at 4:41 am

    • They forgot to include “respectively.” There’s your loophole.

      Should have been written, “The minimum and maximum throttle pedal travel positions must correspond to the engine throttle minimum (nominal idle) and maximum open positions ‘respective’


      May 20, 2011 at 1:44 pm

  11. you deserve a job in F1 Ross D, brilliant thinking :]

    and well spotted kyle, another loophole realised! next thing drivers will be learning to hold their right foot flat while braking… insane.


    May 20, 2011 at 5:38 am

  12. I wonder if there aren’t any regulations that prevent Ross D’s solution being legal. I vaguely remember (was it Williams? In the 90s?) the FIA banning brakesteering; which entailed balancing braking power to the left/right side depending on the position of the steering wheel. The basis on which that was banned might also apply to this situation.

    Please correct me if I’m wrong! :)


    May 20, 2011 at 9:00 am

  13. how do they plan to enforce this?


    May 20, 2011 at 12:24 pm

  14. @Paulo: Wow! Didn’t know about that BMW solution

    Il Venturetto

    May 20, 2011 at 12:30 pm

  15. It was Mclaren that had this brakebalance pedal


    May 21, 2011 at 8:04 pm

  16. Great post Scarbs!

    I really didn’t know that the flow was “re-enforced” with the fuel combustion.

    I always assumed that the inlet and outlet valves were just kept open (with no fuel injected), so the flow would simply go through the engine. I guess you would get too much turbulence and not enough flow to successfully power the diffuser. Do you think it could still be enough to generate some extra down-force (obviously less than now)

    I quite liked Ross D’s idea, but that doesn’t solve the issue of shutting the throttle down to 10%. I guess a team could have a massive manifold so the 10% was the maximum it actually needed, but the throttle could go up to the daft full 100% for the scrutineers tests. Still do not think that would work, seeing as I am not too familiar with the intake manifold regs.

    Good post. Now I cant wait to see what the teams come up with next!

    El Presidente Raf

    May 23, 2011 at 2:32 pm

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