Blown diffusers – So what exactly is being banned?
Blown diffusers – So what exactly is being banned?
Posted By: James Allen  |  12 Jun 2011   |  11:52 am GMT  |  75 comments

The Formula 1 teams have been on notice for a few weeks that the practice of “hot blowing” and “cold blowing” exhaust through the diffusers is to be banned and yesterday the FIA confirmed that this would take effect from Silverstone onwards.

These narrow flat exhausts will be banned in 2012

Meanwhile the whole concept of blown diffusers will be banned in 2012 as new rules will insist that the exhausts exit out of the back of the car, as in the past.

The Technical Working Group, which consists of the FIA’s Charlie Whiting and engineers from all the teams, will meet this week to decide exactly how to frame the wording of the ban so it is policeable.

But what exactly is “hot and cold blowing” and what is being banned here?

Cold blowing – When the driver lifts off the throttle pedal the engine throttles go to 100% and it cuts all the fuel to the spark, so there is no drive from the engine but all the air is flowing through the engine to give about 75% of the exhaust pressure you get on the power. Everyone has been doing this for the last 12 months.

Hot blowing – For the last two or three months this practice has come in. In hot blowing they start to inject some fuel and put a spark into the engine to increase the energy into the gas. So they end up with more downforce. To do that they have to retard the ignition and kill the torque, because if you don’t then the engine is going to create torque and the engine is going to keep going when the driver lifts off the throttle.

The performance gain is around half a second to one second per lap. But this drives fuel consumption up by around 15% and is very hard on engines, so it means costly reliability programmes. This is not the way the FIA wants the sport to go.

The question everyone wants to know is, will this slow the Red Bulls down relative to the opposition?

Renault, Red Bull’s engine supplier, has been working on this technology for longer than the others, but Ferrari and Mercedes are very active in this area too. The majority of Red Bull’s advantage is the power of its DRS wing, which can be used in fast corners and gives it a couple of tenths of a second in qualifying over McLaren in particular and also Ferrari. In the race this advantage goes because the DRS can only be used on a straight and when following another car. Hence why the races are much closer than qualifying.

Hot blowing is something Cosworth haven’t been engaged in, so teams like Williams can only do cold blowing.

Fans at Silverstone, who have already attended a race this season, will notice the absence of the distinctive crackle sound when the driver lifts off the throttle.

The FIA’s memo to the teams, issued on Saturday in Montreal, makes it clear that the reason for the move is that the direction these devices are taking the sport is completely opposite to what the federation is trying to achieve.

The memo says, “The financial, technical and human resources required to support such developments, as well as the impact on engine reliability and on fuel consumption are totally contrary to the objectives pursued by the FIA, the teams and the engine manufacturers.”

For next year exhausts will go back to looking conventional, they will have to extend to between 330-350mm beyond the rear wheel centre line, be situated in the area between the bottom of the rear wing and the top of the diffuser and have to be circular, with a vertical cut-off.

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Hey James,

I have just read through all the comments about the race. As an engineer I love to see the innovation in the sport, definitely a big part of why I watch Formula One. And in a way I am very glad that the FIA have decided to move on from blown diffusers because I know that there will be a new technology rising up from it’s ashes long before they settle. Formula One is the pinnacle of Motorsport because it is dynamic. It is as much a battle between drivers and manufacturers as it is a manifestation of our human hunger for innovation and knowledge. We are so lucky to bear witness to the spectacle of the advanced development of land transportation before our very eyes.

Furthermore, I am quite surprised that no one has really talked about the fact that we saw a chink in Vettel’s armour in Canada. After seeing him crash in Turkey in the rain and that error we saw on Friday, as a driver I would be extremely relieved to know he’s still human.

It has been a pleasure to share the season thus far with you and look forward to your future blogs. Long live Formula 1!


I generally don’t have an opinion regarding this one, my problem is rewriting the rules in the middle of the season though.


To get rid of the pace of Redbull, I think.

If not they can wait until new season to do it.


This is what I mean, I’m not against the decision, just don’t change the game rules in the middle of the season.


Its as if FIFA had a squad of big, Rugby-types that would dash onto the pitch whenever Blatter phones during a match, and reset the net in different places.


Since we are well into the season and the teams have already spent a lot of money on it why not just ban it for next year like they did for the DDD? Why right in the middle of the season? Are they hoping it will ‘spice’ up the championship?


May be. They can wait for next season with no problem on anything except Redbull dominate the race.


This whole issue is just a prime example of the ebb and flow between the rules and innovation. Though this gives us all a lot to debate and is fascinating to watch, in the end these things come and go. It’s not worth getting too worked up about one way or the other.


“I’m glad they are banning the effects of the hot blowing and reducing cold blowing.

This will bring back more of the skill of the driver in slow to medium corners.”

I agree, however the championship is actually for constructors.


I’m glad they are banning the effects of the hot blowing and reducing cold blowing.

This will bring back more of the skill of the driver in slow to medium corners. Hopefully we will see so more overtaking at these points.

We have seen cars having huge traction coming off slow corners being provided by computers.

We should now see more mistakes and more driver input into slow corners.

It will be interesting to see what teams and individuals benefit from this.

I’m betting Mark Webber for one!!!


I remember James writing last year that it was believed the reason why Vettel began to outperform Webber over the second half of the season was because RBR refined the sofware for the throttle and how it ran through the diffuser, ie Webber had superior throttle control during the early development of the blown rear end. It will be interesting to see if things change.


As an edit to my comment above, I’ve just looked at the regulations, and can see nothing that would disallow an infinitely adjustable wing. But I imagine controlling it would be an absolute pain in the neck – one button for each corner setting?


Are the DRS rear wings allowed to have a multi-stage setting? Can they open them fully for a straight, and close them partially for a fast corner? Is that what Red Bull are doing?


I strongly disagree with the FIA on this. The engineering innovation is a major part of my interest in F1. If they continue on this route, teams will question the wisdom of investing time and money into innovations only to have them dissallowed if they work too well. Their attitude will be “if such and such team have been creative and gained a few tenths on us, we can just save our money and wait for Whiting to legislate them back down to the rest of the field.” His argument that the engine is a moving part and therefore the blown diffuser is a moveable aero device is on very shaky ground. By the same argument, one could say the wheels are moving parts too and movement through air creates downforce so the wings are also illegal then! That is the ultimate irony I think: previously, the engineers tried to find loopholes and creative interpretation of the rules (eg: double diffusers in 2009). Now it seems the FIA/Whtiing are the ones resorting to creative and questionable interpretation of the rules to hamper innovation.


F1 start to become one make race series.

I wish we have another race series may be “Premier Formula” that let engineer have more freedom to develop the car. Let people who satisfied with one make race low cost series continue with Formula1.


F1 as the pinacle of racing means the top of the cream, the best drivers, with clear rules. Yes engineers can use some creativity to a certain extent, but we don’t want engineering to be above driving ability… this hot-blown exhaust system is like a driving aid… like a turbo, if you have it you win 0.5 to 1 second over your competition and it is not fare!

Now, I understand why Michael Schumacher has not raised to the top, the younger generation (Fernando, Vettel, Hamilton) are relying on electronics and driving aids in order to compensate their lack of driving skills… we saw it in montreal, in the wet, no driving aids, Schumacher was there at position 2… once the wet was gone and dry weather came, all driving aids help the younger guys.

Come on! stop giving driving aids and we shall see who is the top racing driver.



I cannot agree with your statement – ” The majority of Red Bull’s advantage is the power of its DRS wing, which can be used in fast corners and gives it a couple of tenths of a second in qualifying over McLaren in particular and also Ferrari. “

That to me is not where the RBR fast corner advantage has come from – there advantage has been – Hot Blown diffuser, Bendy front wing – And the ability to pump huge amounts of fuel into the Quali 3 to power the blown diffuser.

Where you say their advantage is their DRS wing I cannot comprehend this statement – they even were opening the DRS in corners showing the downforce came from other places.

I said at the beginning of the year that I didn’t think RBR were utilising KERS and I still think this – the RBR is a smaller car with correctly places ballast to ensure a short correctly weighted car – they arenj’t worried about KERS.

Great win for Jenson – he deserved all the accolades today.

Thanks James great journalism.


No excuse for soing this during the season. “It’s not the direction the FIA wants to go” is no excuse tho change the rules midstream.

1. All money available to the teams ALWAYS gets spent on something.

2. Fuel efficiency? GTFO. A 15% increase in on track comsumption probably amounts to about a .01% increase in the total fuel consumption of an F1 weekend.


the main problem with f1 at the moment is now what we are watching .nothing because of the weather in a country where we should not be at this time of the year only because the television companys want it not for the sport .its all done for ratings not the dont mind late nights early mornings as long as they race not crap…..


nick legg… remember that name. The guy who didn’t enjoy the Canadian Grand Prix. nick legg.


… and now the race is red-flagged. So everyone will change tires, change wings, have a soda, take a leak, twitter a while, watch some Curling to break the monotony, and Kobayashi will be in 2nd. Lets see if he tries some banzai move on Vettel!


Rather than Kobash, who put in a great race today, it seems that Lewis is fast becoming the master of the Banzai move. As an Englishman, I’m a fan of Lewis (and Jenson and Paul and any other Brit who joins the top flight of motor racing) but I wish he’d cool off a notch and realise that the race is more than one lap.

He appears to have a little more natural speed than Jenson, particularly over a single lap, and if he’d waited until the DRS was enabled to start picking off cars, he’d most likely have been cruising to a win by the end.

At the moment, I’m reminded of the story of the hare and the tortoise. With all due respect to Jenson, who is far from being tortoise-like, his more measured driving style and cool brain under pressure gave him a fantastic result today. Less haste, more speed, Lewis!


Regardless of someone complain about how easy DRS help to overtake but we still have a sad to see a lot of driver DNF while they try overtake each other.


Good post. Just what I was thinking. Red bulls style is loads of well executed ideas working as a whole. Is taking one part of the package going to unravel the progress of red bull. As their kers is only 2/3 the power of mercedes does it mean the domination going to end.


It’s disappointing that another innovative concept was not allowed to be fully developed. It was a clever response by the engineers to the FIA’s chokehold on technology. From an aesthetic POV, it’s too bad because you could at least differentiate the cars by the different engine notes. F1 is so homogenous as it is.



These close-up photos and drawings you often provide are very interesting… but I often find it difficult to tell which part of the car I’m looking at, and from which angle. It would be nice to have a wider-angle shot or a few words to go along. I hope I’m not the only one who thinks this?


I can´t understand this changes during the season, why not wait and regulate this blowing dilema up to 2012!


Just becuase it is not a level playing field today… the advantage they can take from this hot air off the throttle system is just to much… and ultimately do we want to see races win by drivers because their foot is not in the throttle? i dont think so… otherwise F1 drivers will be replace by drones!


But we in race car sport and the better car should win right?

Why not let driver pull car by them selves if we want to prevent the better car to win?


about Hot Blowing James, I understand that there’s the technique you explained but in the case of Renault, I read in a french blog confirmed by Newey press conference in Monaco that the french engine uses a different technique.

The fuel doesn’t burn in the cylinder. It is injected and leaves the engine during exhaust stoke. In the exhaust pipes, the heat is such that the fuel ignites creating the air flow which energizes the flow around the diffuser and creates downforce.

This technique not only helps downforce but helps cool the engine thanks to relatively cold fuel and air going into the cylinders.

That’s why Newey complained of reliability issues if they are banned from using it.


So they want Redbull to have reliability issues and other team can catch up, right?

I start to feel strange with this sport.


It depends how we define ‘exhaust’.


Well, it seems FIA is dumb when it comes to clearly defining anything actually.

Seems every rule they come up with is hazy and open to arbitrary adherence.

Marcus in Canada

Is the RBR DRS actually better, or is their overall aero (including their hot blown diffuser) so much better than other teams that it allows them to use their DRS at times that others cannot?


”The majority of Red Bull’s advantage is the power of its DRS wing, which can be used in fast corners and gives it a couple of tenths of a second in qualifying over McLaren in particular and also Ferrari.”

This can only be on the exit of fast corners when the downforce is not required, because by this rational then less downforce (and thus less drag) through a fast corer is better, therefore Ferrari and Mclaren should be quicker through fast corners.

There is a theoretical limit to downforce defined by engine power. An f1 car can use as much downforce as it can get. So am i missing something , can someone explain this to me.


I agree that hot blowing should be banned. But why ban cold blowing? It is using the normal exhaust gasses in a convenient to create downforce. While instead the exhaust gasses would be a total waste, they deliver extra power to the car now. It is a bit like recycling. Instead of throwing your waste away, you reuse it to improve the performance of your car. How can this be a bad thing?


…and what color are they required to be?




Exactly! And the mechanics can only consume food up to the limit of 7350 calories per head per race weekend.


Man! I would freakin’ *starve on that!



May be its artificial, but it will definely spice up the second half of the season – with Red Bull loosing their big advantage – and other teams trying to find something new!


To be honest this won’t change anything and as such it wasn’t worth changing. I think it’s a dynamic and interesting technology that is adding something to the racing so let them go for it. As for the cost issue, that’s a dead rubber. The FIA are the ones that change the rules so often that car designs have a very limited shelf life in terms of seasons before a redraw. If it aint broke…

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