F1 2009 Technology: Rear wings, diffusers – and the inevitable controversy

Posted on | Author John Beamer

McLaren have had lots of problems with their rear wing and diffuser
McLaren have had lots of problems with their rear wing and diffuser

As we head into the first race of 2009 a row is brewing over the diffusers used by Toyota, Williams and Brawn GP.

F1 Fanatic guest writer John Beamer takes a look at the diffuser row and offers his thoughts on what’s gone wrong at McLaren.

Hands up who finds that rear wing attractive? Uh… thought not. What is the FIA playing at? In two words: not sure.

We all know that the objectives of the 2009 regulations were to reduce the wake and aerodynamic sensitivity of the car. A high, squat rear wing was the FIA’s response to its own challenge.

By raising the rear wing it works in cleaner air so the plane should be more efficient. More downforce is available for a given angle of attack which, all else being equal, makes the associated wake smaller. However, the reduced plan area cuts total downforce and teams may simply reclaim lost grip by running more cambered profiles. Drag increases slowing the car – some in the paddock contend that this was the true intent of the FIA’s regulation.

The other consequence of raising the wing is to decouple it from the diffuser ?ǣ moving the diffuser back helps too (more on that later). How does raising the wing help? The 2008 regulations cause the rear wing to generate a low pressure zone at the base of the car, thereby creating a shallower pressure gradient for the diffuser to work against.

In theory, raising the wing pushes this low pressure zone higher so upwash from the rear wing/diffuser combination is muted. So far the profile shape and integration with the endplates are nothing that hasn’t been seen in the last couple of seasons.

More interesting is the interpretation of the diffuser regulations. Compared to 2008 the diffuser has move aft, to the rear wheel centre line, is raised, with a severely restricted central section.

The diffuser controversy

Timo Glock's Toyota - diffuser highlighted (click to enlarge)
Timo Glock's Toyota - diffuser highlighted (click to enlarge)

That teams can run a central section at all is of some contention. However a close reading of the rules suggests that a 150mm central section extending beyond the main diffuser is permissible. Toyota was the first team to take advantage of this, with its small central tunnel.

The theory is simple. By increasing the overall volume of the diffuser air can be slowed in a more controlled fashion which reduces the odds of flow separation. I find it hard to believe that the FIA will outlaw this central tunnel as it is a fair interpretation of the rules

More controversial are the subsequent interpretations by Brawn GP, Williams and Toyota. These teams have so-called ‘double decker’ diffusers and likely contravene the spirit of the regulations if not the letter. The regulations for the diffuser rely on bodywork visible from the ground. This means that bodywork behind that which is visible from the ground sits outside the rulebook governing diffusers. Hey presto, a few canny designers have exploited this loophole.

The Williams and Brawn diffusers do exactly this. A lower surface tracks a higher, wider upper surface, which creates a more voluminous device. As we head to the first race of the season it is unclear whether the FIA will permit these.

McLaren’s problems

McLaren’s woes likely originate in the diffuser, which is one of the reasons why green flow-vis paint was plastered all over the device in recent testing. Flow separation here is pernicious, causing stall and a loss of downforce. Not only will this make the car a lot more susceptible to oversteer but the rear tyres wear out a lot faster.

The problem with flow separation in the diffuser is that it is hard to pinpoint the root cause. The issue may be with the diffuser but equally may be to do with the splitter. After all the diffuser must work with the flow patters it is given – all of which is heavily influences by what happens at the front of the car.

Given the Kovalainen set the MP4-24’s fastest lap despite not being a fan of oversteer suggests the Woking-based outfit has overcome its back-end issues. However, that doesn’t mean McLaren will be on the pace in Australia.

It’s taken the team several weeks to get to the bottom of the problem, if indeed it has. Development on other aspects of the car will have slowed. Although the boffins at HQ are capable of developing the car at a prodigious rate, in the current environment of restricted testing it won’t be before the European rounds that Hamilton and co. are back on the pace.

John Beamer also writes for Race Tech magazine.

Images (C) www.mclaren.com, Toyota F1 World

66 comments on “F1 2009 Technology: Rear wings, diffusers – and the inevitable controversy”

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  1. great technical post.

    i read on autosport the other day that 1 team has complained to the FIA regarding the diffusers, aside from my thoughts that it’s probably ferrari since they complain about everything (i’m a ferrari fan), i suspected it could be mclaren, since they are suffering as a result of their aero design.

    i don’t think what the teams have done with their designs means they should lose them, they we’re smarter and designed something better and within what the rules stipulated.

    look at all the fins, wings, horns and other aero devices that ended up being attached to cars by the end of last year, f1 is designed to push the limits of design and theory, and they have done so. hats off to them for being smarter.

    1. I think it’s more likely that it was Renault complaining as Briatore has gone on record having a bit of a paddy about it not being fair (they didn’t think of it too I suspect) etc.

  2. Eduardo Colombi
    23rd March 2009, 8:07

    Great analysis by J. Beamer, very enlightening. The new rear wings looks really out of place that high and that narrow, but anyways…

  3. Are the FIA able to ban the diffusers which have expoited the loophole, even though three teams have developed them? Surely if they are banned it goes against the F1 spirit of using technology to overcome problems? Isn’t it better to allow the other teams to catch up? They have allowed Renault to get on equal terms as far as engines go, so they must allow the same rules to apply to aerodynamics too?
    Otherwise its the ‘J-Damper’ row all over again….

    1. Aerodynamics aren’t frozen in the same way as the engines so, if the diffusers on the Brawn and Williams cars are considered within the rules, all the other teams are free to redesign their own diffusers to take advantage of the same loophole.

      But, that’s not to say that the FIA couldn’t issue a rule clarification setting out that the Brawn/Williams approach was not what it intended to allow – however cunning the interpretation of the regulations. Clever engineers (like clever solicitors) will always find some way of getting around a rule, no matter how carefully worded.

    2. But you’re applying logic to the workings of the FiA – no way should that be done…

      There is some talk that Brawn GP’s diffuser might be allowed as it doesn’t contravene the rule about maximum height…

      Either way, we’re in for a messy weekend I fear…

    3. Not really, just saying what could happen – not predicting what will.

    4. the clincher/deal breaker is this paragraph in the 2009 tech rules (article 3 is the bodywork regs):

      One of the purposes of the regulations under Article 3 below is to minimize the detrimental effect that the wake of a car may have on a following car.
      Furthermore, infinite precision can be assumed on certain dimensions provided it is clear that such an assumption is not being made in order to circumvent or subvert the intention of the relevant regulation.

    5. the question is then, does their diffuser destroy the airflow needed to create down force for the chase car

    6. exactly! If the following car is disrupted by a ‘special’ diffuser more than when following a ‘normal’ diffuser, then Williams/Toyota and Brawn might not have leg to stand on. At the moment, I’m leaning toward a similar scenario to what happened last year with Ferrari: following the race, the rules are clarified and the three teams will have to change their diffuser for the next race, but they wont lose any points scored from Melbourne.

      Also, considering McLaren, Ferrari and Renault each played a hand in designing the new diffuser may go some way to explaining why they haven’t designed a ‘special’ diffuser themselves. As members of the OWG they are each part responsible for the new regs: it would have been strange scenario for them to try ‘circumnavigate’ one of the rules they themselves had a hand in creating.

    7. correction: I meant of course the 2007 Melbourne Ferrari scenario

    8. that’s where things get hairy, the 3 teams that created the rule’s didn’t exploit them.

      why? well either because their internal understanding was more specific than documented (they were trying to achieve something with the rules and didn’t consider re-reading what they wrote to exploit them beyond their initial thoughts).


      they were all just bested by other teams and smarter people.

      either way, it will come down to, how badly the airflow out of those diffusers upsets the car behind, and how much the 3 teams that created the rules cry about people exploiting them.

      i think the latter wont matter much at all, really just how it effects the car behind is all that really matters, but you can’t rule out politics in f1.

  4. i know this is not part of this post but just found it and it looks cool

  5. John Beamer
    23rd March 2009, 9:07

    Clarification – the article says the McLaren’s woes originate in the diffuser. That isn’t (necessarily) right. They manifest in the diffuser but probably originate elsewhere as I allude to.

    Thanks for all the positive comments. Appreciated.

  6. Good article, however, in regards to the rear wing for once it would be incorrect to criticize the FIA. The rear wing/diffuser, in fact most of the aero regulations are a direct result of the findings of the OWG – the Overtaking Working Group. The FIA said to the teams, “you come up with the answers to more overtaking and we’ll implement them into the new rules.” The OWG was founded and is still made up of members (including others)of McLaren, Ferrari and Renault. This was in fact a rare occasion when FIA admitted their knowledge was insignificant to that of the people who actually designed F1 cars, and thought it best to delegate responsibility to the teams to decide future (2009) ‘overtaking friendly aero’ rules. The OWG delivered their findings to the FIA, who in turn based the new 2009 regs on them.

    If the new rules are unsuccessful, one can’t really blame the FIA this time!

    1. Yes, but the OWG is a part-extension of the FIA. The FIA and Tony Purnell were quite involved but your point is right.

  7. Terry Fabulous
    23rd March 2009, 9:30

    Great article John, I find this subject pretty hard to get to grips with (and for that matter, somewhat boring) but I feel after reading this that i could explain what a difuser is and why they will be all over the news this weekend.
    @Eduardo Colombi – The cars look so much better with clean lines don’t they!

  8. I hope the diffuser row doesn’t overshadow the start of the season, considering the amount of time people have known about them in public if any cars are disqualified for running them then it will make F1 look more unprofessional than it does at the moment.


    This Autosport article had given me the impression that they had been given the all clear at the start of February.


    However this one from the weekend is saying there will defiantly be appeals against it at the Melbourne.

    I hope it doesn’t get banned, but if it does I suppose it won’t be the first time something was banned on performance grounds even though it complied with the rules.

  9. The solution is simple…

    If it proves to go against “the letter” of the rules, its illegal and therefore can be banned.

    However, I don’t think that is the case, and it probably only goes against the intent of the rule. In which case for 2010 the FIA should close the loophole, and too bad to the teams that didn’t have the foresight to see it in 2009.

    1. Logically that is what they should do, but I doubt that is what will happen…

      I wonder if the 3 teams in question have more basic diffusers ready to go on the cars just in case…??

  10. However… nothing about the FIA and their decisions are simple… ;-)

    1. Let’s face it, FIA good or bad. F1 and the sporting regulations are not a simple matter.

  11. FIA are bringing the sport into disrepute (again) with their incompetence.

    If the diffusers are against the rules, then they should have been inspected and banned as soon as they hit the track. Ferrari had exposed exhaust pipes which were illegal and they changed them. If the diffusers are within the rules, then they are legal and too bad for the tems which failed to spot the loophole. They had enough time to develop similar diffusers themselves.

    Either way, the FIA (or whoever it is that enforce the rules) should have acted sooner, rather than leave it until the first race of the season. The person who stands to lost the most from all this is Bernie. The average punter is not going to know what the hell a Diffuser is and is certainly not going to be pleased if a team is strpped of its points or a rule is changed mid season, which affect the outcome.

    FIA is a bloody disgrace and should be replaced forthwith.

    1. the thing is this: the FIA technical rules for F1 are often written out, not drawn out. The reason for this is the very essence of F1: it allows for a degree of free thinking, technological, but artistic flair. Written rules, rather then technical drawings, are always going to have at least a degree of ambiguity: enough room for interpretation. Different interpretations = different solutions = different designs. This is what F1 is all about.

      Pre-season is the off season. During the off season, teams can test cars with all sorts of gadgets on them – it’s testing, they are free, within reason, to do whatever they want. Therefore it’s not practical to allow other teams to protest their competition’s legality during pre-season.

      Teams can only protest another team’s design when the actual season starts – hence why we are heading for a showdown in Melbourne.

    2. If the diffusers are against the rules, then they should have been inspected and banned as soon as they hit the track. Ferrari had exposed exhaust pipes which were illegal and they changed them. If the diffusers are within the rules, then they are legal and too bad for the tems which failed to spot the loophole. They had enough time to develop similar diffusers themselves.

      If the FIA had let Ferrari take the illegal exhaust pipe exposure to the races there was a very real chance they would have been forced to disqualify the cars, and that goes against all F(errari)I(nternationl)A(ssitance) ethos.

      With the diffusers they have managed to delay and haggle over any decision, leaving themselves in the nice position of cars to disqualify if Ferrari don’t manage to win by themselves.

      The truth is out there…

    3. get over yourself dougie. the truth is there. ferrari changed their design because they had to, the diffusers are technically plausible. it has nothing to do with ferrari or conspiracies. i hate this conspiracy crap. grow up people, season hasn’t started and the weirdos are coming out of the woodwork already.

  12. These teams have so-called ‘double decker’ diffusers and likely contravene the spirit of the regulations if not the letter.

    IMHO if a diffuser corresponds to the letter of the regulations it is legal. The spirit (or interpretation) of the rules doesn’t count much because everyone has it’s own interpretation of the rules.

    So I think if a diffuser corresponds to the (letter of the ) rules it’s legal.

    And about the flexible wings of Ferrari These weren’t legal according to the letter of the rules, but the measure methods couldn’t detect that until later in the season.

    1. good point, i agree why couldn’t the authorisation of parts before they get slammed into a wall happen on the same day, they’d just need to take photos and get the tech specs on everything then come back to them with a decision on weather they can use said part or not.

    2. LOL!! Cheers Todd… it was purely meant tonque-in-cheek to stir the consipiracy lobby… my true view is further up. :-)

  13. Bigbadderboom
    23rd March 2009, 14:55

    As many have metioned before this is a more significant problem because this was a restriction that was suggested by the OWG, it’s a shame because the FIA has bowed to popular support and enlisted team assistance only for the main proposal to be reduced to a farce at the first race.

    Personally I am a strong advocate of pre season scrutineering. It’s true that teams test all kinds of gadgets and gizmos, and they should have this innovative freedom, but once a component or system is deemed practicle by the team it should be submitted for pre-season scrutineering. I can’t see how this is going to ride on race day!! And Mad Max’s only response is to suggest Teams submit complaints to race marshalls who will then have to decide on the legality of the diffusers………..it’s a farce.

    1. well there is pre-season scrutineering, the fia inspect devices and tell the teams that if they run said device, they’ll be in trouble – just like ferrari had to change their exhaust system.

      the diffusers have been looked at, and they want to meet about it, but there’s little time before the opening to discuss it, and there’s no time for teams to change design, so it has to be done during the race weekend (the meeting) and changes – if any will be done most likely before the next, or race there after.

      it’s not so much a matter of scrutineering, its a matter of time, however, a pre-check of all teams, like 2 weeks before the opening would be good, but its still very little time to re-design any major component if it is wrong.

    2. I’ve been giving this some thought and what I realised is;

      F1 cars have to pass crash tests etc, so why not scrutineer the designs at the same time? Then any new parts the teams wish to add to their cars must be authorised by the governing body’s representative.

      Doesn’t sound too difficult to me…

  14. @ glamourBob.
    If the regulations are written rather than drawn, what is the primary language used? French or English?
    Is part of the problem the very fact that they are *written* out and then translated into other languages whereing shades of alternative meaning can be included by mistake.
    It might be better to have large areas of the car design regs literally *drawn* out so that poor translation cannot be involved.

    1. As far as I can see, (have a look yourself at FIA.com)the F1 regulations are only written in english, so no translation problems.

      As i said in a previous post, I personally don’t agree with *drawing* the regulations. The whole point of having a non-spec series is to have different interpretations of the rules which leads to diversity and innovation – one of the cornerstones of F1.

  15. If Charlie Whiting was consulted during the evolution of the controversial diffuser designs and he declared them to be legal, how can an appeal filed after the first race
    be upheld??

    Good engineers maximize potential within the regulation. No way should this be appealed or upheld.

    1. Remember Spa last year?

      Charlie Whiting said to McLaren that Hamilton’s overtaking manoeuvre after gaving his position back to Raikkonen was OK, only to be overruled by the stewards later that day.

      Same thing could happen here!

    2. This bull about not enough time to inspect, discuss and make a decision is nothing short of bureaucracy. This issue has been on the cards for ages, I’ve been reading about the complaints over Toyota & Williams since weeks before Brawn was even confirmed as an entrant.

      The FIA were quick to act on the Ferrari exhausts and it was replaced within a few weeks. It may be that what Max said about it being interpreted either way is true, and the indecision comes from that. But with so little time left, its not fair to make the teams race in uncertainty, they should have prioritised this a long time ago and forced a decision (good or bad) then stuck by it.

      ps. this is not a conspiracy theory ;-)

  16. Captain Caveman
    23rd March 2009, 17:28

    An interesting note that is coming out from other papers (allegedly) is that some teams (albeit) Renault and Red Bull have claimed that they and 5 others teams looked into the diffuser idea and liaised with the FIA, but were given a negative response.

    If this is indeed correct, then I can see why they are annoyed, but if so, one would have to ask why it has only come to light today.

  17. MacademiaNut
    23rd March 2009, 18:19

    Great article!

    Here are some pictures of the diffusers on the different cars.

    Diffuser Pictures

    If the above link doesn’t appear properly, please edit it. Sorry in advance if it causes inconvenience.

  18. Perhaps this will be flexi-floor/tuned mass-damper all over again, banned mid-season? But with the restrictions in testing, surely a ban at this stage in the game is really unfair?

  19. The double deckers are clearly acting as a diffuser, and so are part of the diffuser – not the crash structure.

    The problem here is the FIA coming out and publicly saying (on their website) that it is an innovative use of the rules that the OWG created(!), before the debate has really been had. Now we are in a sticky position going into Melbourne.

    Part of me is with the OWG teams and part of me is not. I guess this is what makes F1 interesting $:)

    1. For instance check out the venturi channels on the FW31 ‘crash structure.’ I’m pretty sure they might be something to do with airflow from underneath the car.

    2. The problem is there is no quick right or wrong answer to if the diffusers are legal or not, there is clearly a grey area which is why Geno – USA is quite correct when he says “Gentlemen, start your lawyers”.

      Whoever has the best lawyer wins.

      Also, one of the other problems is dimensionally, when following a literal, but sneaky interpretation of the rules, the ‘special diffusers’ are arguably within the regulations. In otherwords, when the car is static and not going anywhere, it could be technically legal. Where the waters are muddied is when the car is at racing speed – only then can you say whether the following car is hindered or not, and even then this could be hard to prove either way.

      So, if Whiting has had a look at the car in parc ferme, that’s one thing, but has he inspected it at racing speed? Obviously not.

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