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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I'm glad. Yet another blow against the aero empire. Good. Please get rid of the wings while you're at it.


Sure! you know, wing was generate more drag and drag not good for fuel efficiency, you need to burn more fuel to make car go fast because drag from wing. This is also opposite to what the federation is trying to achieve, too. Why not?

Marcus in Canada

Absolutely! Chop the wings off (figuratively obviously) and the ratio of mechanical to aero grip would go up and make the cars much more drivable (especialy for the good drivers) and make passing and slip streaming more practical. And surely to god noone thinks that wing technology is transferable to road cars?


Can't agree on that: 40mph is fast enough to generate significant lift if steps aren't taken to mitigate it. The shape of most road cars is designed to create downforce at speed - if this wasn't the case then you could easily loose front wheel traction at motorway speeds, especially if driving into the wind. Sportier cars also have spoilers and wings - these aren't there for cosmetic or poser-ish purposes, they are required to make a more powerful car safe to drive (the exception being the ridiculous things you see younger drivers doing to their 1.1 Corsas!)

All of that said, I agree that it would be desirable to have less aero and more mechanical grip in F1

Marcus in Canada

Exactly my point "The shape of most road cars is designed to create downforce at speed", in other words for practical purposes the wings aren't necessary. More than enough aero downforce can be generated by the underbody to eliminate lift, the wings are not necessary for that. Also, the underbody aero work is much more practically transferable to road cars, as all but the most powerful sports cars (and then only at near full speed) need wings.


I can understand that the FIA are trying to achieve and I don't wholly disagree but F1 was always about the clever devices engineers and car designers come up with to get that extra tenth of a second. The way the FIA are going about this will ultimitly stifle that creativity that F1 fans love to see. They might as well contract out the car design to one team and everybody uses the same equipment. What I'd like to know is what the team principals really think about things such as KERS, DRS and the raft of rule changes designed to stop the cream rising to the top?


I understand your point. Part of F1 is the incredible creativity of engineers like Adrian Newey.

However, I remember Ross Brawn saying a few months ago that this area of car design is in its infancy and that if it wasn't stopped or limited by regulation it could go very far.

If it is allowed it will inevitably create safety issues much like ground effects did.



This does throw a question my mind... are Red Bull able to use the DRS wing around the corners because of the blow diffuser being so efficient?

Therefore the question has to be will Red Bull still be able to use the DRS in the corners if they are over-reliant on the forced diffuser...

The other consideration is that everyone else will also take a step back to some degree... how much is the question...

This level of technology is the main reason for me supporting a new engine and some sort of engine championship to ensure that it justifies the engine development programs that are required....

World Champion, Team Championship and Engine Champion for 2013 would make the development costs all worth while for the extra screen time and awareness the F1 circus would give to the engine suppliers.

Finally James, loved the forum video and podcasts over the last few days.



Am so glad. The cars sound terrible off throttle Espically the Renault. Good move Charlie. I approve. Not chuck the drs in the skip also :).

Francesco Lanza

For next year them would that be worse for the cars behind following the car infront trying to stay close


Surely, if the exhaust gases can be used effectively using the cold blowing method, then this should be kept, isn't it just recyling.. Additional fuel is not consumed - is this in actual fact a way to slow the Red Bull machine?


Agree with this - cold blowing sounds like a very clever use of the exhaust, while hot blowing sounds like the first step to the fan cars.

However, policing it might just be terribly difficult.


You may be on to something there Terry....


Yeah, it sounds to me as if cold-blowing should still be allowed, but not hot-blowing; it's only the latter that costs more fuel and needs lengthy engine reliability programmes...


Lot's of people seem to believe (or hope) this will slow the Red Bulls down relative to the other teams.

I don't see it. They'd be more vocal in the press complaining about such a move. As James rightly points out RB have other technological advantages, all working together.

I think there will be some very unhappy (and vocal) McLaren fans after this kicks in.


I certainly will not be too surprised when the RBR comes out of this with even more of a gap to the rest.

Mclaren only became competitive this year when they copied the Newey exhaust in the 11th hour before Australia, and last year their blown diffuser car had a lot of teething problems that Im pretty sure only went away when they nailed the off throttle mapping.

Ferrari has a similar RBR system and until recently have been off pace which I suspect will resurface when we go back to harder tires.

Wont even go into the Merc except that on another forum someone astutely noticed that Ross Brawn seems to be more or less happy about this decision, perhaps its just revenge for all the hate he got about his DDD or perhaps and more probably they stand to gain from this reg.

We need to remember its not like RB7 is a lame duck of a car, this isnt going to be a free lunch for any of their competition, more probably this will take one less avenue of development away from the competition as they try and catch RBR, making their job even harder.


completely agree - it may hurt RB a touch more than the other top teams, but they will all suffer prob roughly the same amount so status quo.

ultimately, its just the hot blown element that is banned and so if the system works well then it will still work well for cold blow.... the real impact will be more apparent next year when other novice solutions will be sought to make up the difference once more.


"ultimately, its just the hot blown element that is banned and so if the system works well then it will still work well for cold blow…"

I don't believe that's a correct statement. The word I heard from the BBC is that Charlie whiting has stated a maximum of 10% throttle when the drivers lift off the accelerator. That effects cold blow too.


One technology bites the dust. next is a

gearbox, but full steam ahead with 4 cylinder

engine, "Bravo ".Welcome to wonderful world

of F1.


This sounds like good news. Hopefully aero features will become a bit less important for the cars. But knowing how smart, creative and innovative the designers are I would n't hold my breath.

No matter how accurately the regulations are worded, their interpetation always leaves room for maneouvering. So at the end of the day, retrospectively banning an aero feature is more effective.


You can't be serious.


FIA probably need to hire more lawyers with engineering degrees.


Thanks for the explanation James, a very clear summary.

Can I ask if there has been any explanation as to why DRS is allowed throughout qualifying? It seems to me that not only is there a safety issue, but as you say it creates a difference between qualifying and race conditions without adding anything positive to the fans. Have the FIA ever given an explanation?


Technically Qualifying is a Practice session therefore DRS can be used at any time during the lap.

See Article 33 in the FIA regualtions:

"Qualifying Practice"$FILE/1-2011%20SPORTING%20REGULATIONS%2008-03-2011.pdf



The BBC's article on this topic quotes 'Whiting's new restrictions have set a limit of 10% of throttle when the driver has lifted off the accelerator.'

What is this going to do to car stability in the corners? Is the combination of exhaust gas exiting over the diffuser and severe limits on the control over the amount of exhaust gas pressure that generates going to make the cars dangerously unstable in the corners?

Is the FIA going to allow an extra test session between now and Silverstone to allow the teams to verify this? If not, are we risking Silverstone becoming a complete crash-fest?


They've got simulations and they can do straight-line tests to confirm the mechanical and aerodynamic balance of the car. They'll arrive in Silverstone with a well-handling car, and they'll do well.

The only difference will be a relative loss (or potentially gain, if they play their cards right) to the other teams.

No big deal.


I don't see why it would make cars so unstable that we start seeing more cars flying off the track.

Afterall most teams only started using the part of the system which is been banned in the past 2 years & we didnt see cars flying off track back then.


FIA: “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.”

And introducing totally new engines with turbos is very cheap to develop and the fuel consumption if the turbo is very low too of course.

FIA is run by strange people.

The onyl reason they do this is to spice up the championship, nothing else. They are manipulating the outcome of the races for entertainment purposes, to draw more viewers. It is a joke.


I don't know exactly how expensive they are to develop, but small turbocharged engines will be more economical (per unit of power or torque) than the current engine formula. Remember, the turbocharger makes use of wasted energy going out the exhaust.

It seems inappropriate to me too to change such an important piece of the regulations in mid-season. When you factor in all transportation costs for moving F1 around the globe, that 15% loss in fuel economy doesn't add anything significant to the sport's carbon footprint.


Seriously? What about the image? It just doesn't look good when the headlines spell out that the top teams are using significantly more fuel for more downforce.


Unless strictly and clearly in response to safety issues, I abhor mid-season rule changes. Teams spend a fortune developing their cars in line with the regulations, only to have those regulations changed at the whim of the FIA. This only leads to more money spent adapting to the change. If you built your home to a specified code, had it inspected and approved, then were subsequently told by the government that you need to replace the plumbing because they had a change of heart, would you be happy?

Marcus in Canada

Agreed, the mid season rule changes seem like impatient tinkering, or trying to adjust results like in NASCAR. They should just ban it for next season.


guys, guys! think about it, you have a system that credits you when you take your foot out of throttle... that's not racing... so now, everytime you face a corner, this system makes you enjoy more downforce so you can better your times... this system has nothing to do with racing, you are using the engine to help you create better aerodynamics... and so, this hot air is spelled and affect whomever is following you... so yes we have eliminated the aero winglets, but with this induced system you guys are creating the same turbulence that an F-15 creates when turning. Come one! level the playing field so we can have Schumi slaps everyone else ass.


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...



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!


...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!


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?


''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.

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?


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.


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.


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?



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?


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.


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.


... 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.


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.


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.



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.


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.


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?


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?


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.


"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.


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.


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.


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.


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!

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