McLaren’s exhaust solution examined

F1 technology

Posted on

| Written by

The distinctive exhaust slot in the McLaren MP4-27

The FIA has introduced a raft of new rules aimed at curtailing the use of exhaust-blown diffusers.

Despite this, evidence from the first two tests suggests teams are using exhaust gases for aerodynamic benefit.

McLaren have come up with one of the more interesting solutions addressing the new restrictions on exhausts for 2012. John Beamer takes a look at what they’ve come up with for the MP4-27.

2012 exhaust rules

The new 2012 rules dictate the positioning of the final 10cm of exhaust piping. The rules specify that this section must be circular, thin-wall and 75mm in diameter.

Teams can have no entry or exit slots along the length of the exhaust. The exhaust exit must between 250-600mm above the reference plane, 500-1200mm from the real axle and 200-500mm from the car centre line.

In addition, the exhaust exit angle must be at positive 10-30 degrees from the reference plane (i.e., pointing slightly upwards) and plus/minus 10 degrees from the car centre line.

This is all aimed at limiting teams’ abilities to place the exhaust in a position that will increase the power of the diffuser. “The exhaust will still have an effect,” Ross Brawn admitted last week, “but it’s much, much reduced.”

The rules leave three apparent options for where designers may place the exhaust exit:

1. Towards either the rear or beam wing,
2. Over the suspension / brake ducts,
3. Away from the car altogether.

Based on early the first two tests it appears the top teams are blowing the exhaust gases over the suspension. However they are trying to seal the diffuser to replicate the benefits of the exhaust-blown diffuser.

It has been suggested that some teams are pushing the spirit of the rules but the so far the FIA hasn’t stepped in. The sport’s governing body may prefer to let the 2012 solutions pass and clean up the regulations for next year if needed.

McLaren MP4-27 exhausts

McLaren exhaust exit

The first picture shows the new McLaren from above. In the blue circle it is easy to see the exhaust ‘bulge’ and exit channel. The fact it protrudes from the sidepod is the first clue that McLaren is trying to do something clever with the exhaust flow.

There has been a lot of speculation about exactly how the device works but it is likely to exploit the Coanda effect to seal the diffuser.

The Coanda effect is when fluid is guided by a nearby curved surface to modify its direction. As the surface curves away from the flow it creates lower pressure close to the surface. This pulls the fluid towards the surface.

McLaren exhaust exit

The second picture is a side-on view of the exhaust. Again, the exhaust bulge is circled in blue.

From this angle you can see the exit slot is pointing towards the floor. This helps induce the Coanda effect and pulls the exhaust flow towards the floor as indicated by the blue arrow. Also the ‘bulge’ directs airflow coming around the sidepods away from the exhaust plume, protecting this flow to the diffuser.

McLaren exhaust exit

The third picture shows the MP4-27 exhaust from behind with the blue circle highlighting the exhaust exit.

In this diagram the exhaust seems to contravene the regulations which states that it must be circular. The exit appears to have a protruding section and there are also two collars on top of the pipe which appear part of the exhaust. From the published photographs it is hard to see exactly what is going on and the team remains unsurprisingly coy.

There are several possible explanations for why this design may still be legal: these parts may not be attached to the exhaust – they may house sensors to monitor the temperature and flow of the gasses – or they may be an interim solution to allow McLaren to better understand the effect of blowing gasses over the diffuser.

Also in the third picture it is possible to see a number of temperature sensors on the topside of the diffuser – these are circled in yellow. Given we’ve now seen this exhaust solution in two tests and McLaren’s performance looks pretty good it is very likely that the McLaren exhaust solution is working.

What the other teams are doing

Another view of the exhaust outlet on the McLaren MP4-27

Many other teams – Ferrari, Mercedes and Sauber in particular – all had similar but less aggressive solutions. Their exhausts were pointing in a similar directions to McLaren’s but without the bulge and bodywork.

Many teams also added vanes to their rear wing and floor to steer airflow to the diffuser. Don’t be surprised to see an innovative solution from Red Bull too – engine suppliers Renault have indicated the world champions have some exhaust innovations coming.

Despite the FIA’s efforts 2012 will continue to see a lot of work on exhaust and diffuser development. But the early indications are teams have some way to go to recoup the downforce lost due to the new restrictions

Brawn added: “We’re still getting a bit of performance from the exhaust with the new car. Nothing like what was achieved with last year’s regulations and last year’s concept. But once you’ve discovered something you don’t un-invent it.

“All of the engineers, all of the designers in Formula 1 have been looking at how you can still retain some of the performance. But it’s far, far reduced to what we had last year and I think most people designing their new cars would be quite happy if they were able to achieve the overall performance that they achieved last year.

“We were testing in Jerez with the 2011 car and it looked to be the most consistent and fastest car there, in 2011 spec. All the new 2012 cars were a bit behind that.”

F1 technology

Browse all F1 technology articles

Images © McLaren; Illustrations ?? John Beamer for F1 Fanatic

66 comments on “McLaren’s exhaust solution examined”

  1. OmarR-Pepper (@)
    28th February 2012, 13:19

    One thing I don’t like about FIA is that if a team finally produces an advantage solution, they should be able to use it next year, not “2012 observations” should be done. Well, good for McL if they have found a loophole or pushed the rules to the limit

    1. I seem to remember a regulation that states that the ECU mapping must not aritificially keep the revs high at low speed to support this.
      If i am right about this then without the ECU mods it will make the cars pretty undrivable at low speeds

      1. Exactly, but why not exploit the effect under acceleration. Any improvement is welcomed in any area. That’s the way how these cars are designed and built.

      2. Why not put the car in neutral? And let the driver use his pedal to create the right amount of revs?

        1. When running at 18,000 rpm and 100-200 mph, I imagine there’s a really good chance of blowing the engine / gearbox / clutch.

          This stuff would be so delicate, so precise, a driver would more likely do more harm than good. It would be extremely hard to manage it in a way that resulted in a gain.

          Given the distraction of effort, concentration, plus trying to race, in the hope of gaining .001’s of a second, the net result would likely result in a lose of .10’s of a second. Even one corner where you lose .10’s of a second would negate any gains elsewhere.

          The net result would be a negative. The greatest risk would be the driver blowing the engine / gearbox / clutch, which you really can’t afford to risk.

          1. @hare I remember reading some about Mark Webber last year and how he could never really replicate Vettel’s brilliant starts. He was more often than not a couple of hundred RPM outside the optimum zone and as a result lost places off the line etc…

            Basically, you’re right, the margin of error is very, very small.

        2. In his glory days Schui was known to keep the throttle open while braking into corners for these reasons.

        3. It would upset the balance of the car as well… A decoupling of the wheels to engine under braking or mid corner could quite conceivably cause a spin all of it’s own

    2. I don`t like rules being revised over the season just because someone was smarter than others neither, but remember it happens.
      Ask Red Bull when FIA changed mid season the engine mapping restriction, or changed the way wings and keel were tested.

  2. Red Bull almost definitely have slight curved vains on their brake ducts to direct some flow to the diffuser and the duct outlets point upwards, no doubt to channel air through & upwards, essentially pushing the wheel assembly down.

    Saw that on both Scarbs & RE’s analysis of the RB8.

  3. I’m a bit of a McLaren fan so I’m hoping the FIA find the design okay. But you have to say that they (the FIA) do leave themselves wide open in these situations.

    I do of course realise that there are literally hundreds of brilliant minds in the teams (including Mr Newey who is a genius) and only a few rule makers, but surely they could have said something along the lines of…

    “The exhaust shall exit the car perpendicular to its centre line between X and Y distance from the rear axle, at a height of between X and Y. The Exhaust gas shall in no way enhance the overall aerodynamic performance of the car” Any attempt to do so will result in the first born of every design engineer being shot! ;-)

    or something…. discuss :-)

    1. Why should the FIA do such a thing? GP2 is a pretty sweet spec series to watch if you dislike development, innovation, and the pushing of rule boundaries. Personally I love it. I thoroughly enjoy seeing what each design team comes up with, who pushed the limit, who crossed it, and the hows and whys therein. The ambiguity is wonderful!

    2. @CovertGiblets The Exhaust gas shall in no way enhance the overall aerodynamic performance of the car

      The problem is that, first of all it is impossible to enforce. Secondly the exhaust will always enhance, or at least have an effect on how the car perform.
      Even the basic rear pointing exhaust of a few years back enhanced the performance of the car by blowing gas rearwards it gave them a boost. In a very small scale, but it is essentially the same principle that powers a rocket into the air.
      Also, why stop development in that area in the first place?
      I see the idea of removing the EBD, because most people thought the sound was horrid (I loved it, but never mind) and by removing that tool it makes the teams work harder and can lead to new and exciting innovations in that area.

      1. I don’t think anything in that post worked out as planned..

        1. Haha, made me laugh. Well confessed lol.

    3. I’m bit of a McLaren fan too. If they lost the silver, and when with Orange, I’d be a lot of a McLaren fan… maybe even a full blown McLaren fan! :) I need to see the passion in the team! I can’t abide silver :)

    4. That sounds clever, but that’s not circular at all.

  4. Many other teams – Ferrari, Mercedes and Sauber in particular – all had similar but less aggressive solutions. Their exhausts were pointing in a similar directions to McLaren’s but without the bulge and bodywork.

    Surely the whole extra chimney on the Ferrari is pretty aggressive? To me the bulge looks like more of an afterthought, and can be removed without changing the rest of the car, whereas the Ferrari’s is a direct extension of the bodywork

    1. But it seems that bulge is more for exiting heat from inside the sidepods. And the channel is not that extremely formed.

      1. Battle of the bulge anyone? :S I find poor humour exhausting.

    2. The bulge is design to induce the Coanda effect on the exhaust gas and push the air coming from the sidepods away from the plume. Feels aggressive to me. It doesn’t look like Ferrari is doing that. But hard to know. And depends on your definition of aggressive.

  5. It is not fully described in the article, but McLaren’s solutions is totally different from for example Ferrari’s. McLaren tries to make the exhaust plumes stick to a piece of bodywork behind the actual exhaust, but Ferrari directs the gasses down by the downwash created by that (awful looking) bodywork thing in front of the actual exhaust. Both solutions have the same result: directing the exhaust gasses to the diffusor.

    1. By the way, great to see a technical article on F1fanatic!

      1. Agreed, great work. Better than Scarbs…….. almost ;)

      2. Certainly @andae23 !

        Check the link for technical articles. They’re usually written by guest writers so you will find the majority of them in there if you have a look around.

    2. Nice summary. :D

  6. I think scarbs on the flying lap mentioned that it probably worked like the Ferrari by attaching to the downwash generated by the large undercut below the sidepod… that and the Coanda effects of course.

    I have a question for John, do you know whether the teams are allowed or for that matter choose to run an engine inside the wind tunnel? Presumably this solution can be tested quite accurately in the wind tunnel so long as they can generate exhaust gasses in there?

    Thanks for the article. I like the drawings.

    1. Looking at it again, wouldn’t the (Coanda) airflow over the top of the bulge effectively prevent the exhaust gasses travelling upwards after exiting the pipe at 10 degrees. This airflow over the top is perpendicular to the exhaust direction and thus seals it off.

      Instead, exhaust gas would be directed along the bodywork channel until coupling with the downwash under the bulge and hence heading towards the diffuser.

      Hope that makes sense ;)

    2. @JohnH
      I have heard somewhere that they do channel hot air through the exhaust on the wind tunnel model.
      Though I am not entirely sure that it wasn’t just another rumor.

    3. @ JohnH: What engine would they run on a 60% scale model in the wind tunnel ?
      The only time they can run a full sized car in a W/T is if they sacrifice wind tunnel time for track testing.

      1. I will try to find out but I would be surprised. They may run a modified engine to test exhaust flow …

        1. @JohnH The Coanda effect pertains to the flow aft of the exhaust. The cliff notes version is that if you pass a gas/liquid over a curved surface, the curvature of the surface induces a low pressure zone which effectively sucks the flow down against said surface.

      2. Tom Haxley (@)
        29th February 2012, 9:21

        They’d only need an engine with the same output flow I guess.
        Im sure some clever engineers could modify something to work

        1. Or they just have a full size engine separate from the model and feed exhaust gas to the outlet via an extended pipe.

          Wuoldn’t necessarily have to be engine exhaust gas either, just heated air – they do something sinilar with aircraft wind tunnel testing.

      3. dont now how they do it but i was watchin a mclaren clip n they can replicate hot exhaust gasses on the test model in wind tunnel

  7. Very good insight into a possible exhaust function. I wish one would be able to analyse that of the RB8 …… The Finger is already complaining the car is quite different, grip-wise, to the RB7 …..

    Hopping Webber will thump him this time around …… hope dies last :(

  8. Roger Fed'error'
    28th February 2012, 15:01

    Gr8 f1-ology!

    I wud deffo want to view such refreshing analysis! Cant wait to direct all my fellow f1 buddies to this site!


  9. Quite apart from anything else. this “appears” to contravene both the vertical and horizontal angular requirements.
    When viewed from above, the centreline of the final exit pipe can point in or our from the car centreline by up to 10 degrees in ether direction, this appears to be angled outward far more than that.
    The same centreline when viewed from the side must point upwards by between 10 and 30 degrees from the horizontal (actually from the Ref plane so may appear greater if rake used) However in this case it seems to be pointing far too low.

    1. Charlie has inspected both this and the Ferrari exhausts and deemed them to be legal. I think the channel is generating a bit of an optical illusion in the sense it makes the exit pipe seem more at an angle to the reference plane/centreline than it actually is.

      I’m surprised that so much bodywork is actually allowed in the rules after the exhaust exit itself.

      1. I’m surprised that so much bodywork is actually allowed in the rules after the exhaust exit itself.

        the same for me, It looks like if someone would want to have the exhaust completely covered under bodywork for some reason they would still be complying!

      2. Double ditto.
        If the FIA were after a classic, simple exposed exhaust they could have added a rule stipulating a range around the exhaust exit in which it has to be directly visible from, say, a yard away. As it is they’ve done nothing about bulges and coverings and the like. They’ve obviously left that bit wide open and should fully expect development in that area.

        And why not. Something has to differentiate the cars. I don’t think anyones going to create a half-second reliable-enough effect at that distance from the diffuser.

        1. If the FIA were after a classic, simple exposed exhaust they could have added a rule stipulating a range around the exhaust exit in which it has to be directly visible from, say, a yard away.

          Why so roundabout? Just say “10 cm of exhaust pipe will stick out outside the bodywork”.

          I’m thinking that’s what Ross Brawn was referring to when he said that the rules governing the use of exhaust gasses were still too ambiguous.

          The teams would have still found ways to make use of the gas flow, but nowhere near as “obviously”.

      3. The regulations go to define a cone shaped area after the end of the exhaust where there must be no bodywork:

        5.8.4 Once the exhaust tailpipes, the bodywork required by Article 3.8.4 and any apertures permitted by Article 3.8.5 have been fully defined there must be no bodywork lying within a right circular truncated cone which :
        a) Shares a common axis with that of the last 100mm of the tailpipe.
        b) Has a forward diameter equal to that of each exhaust exit.
        c) Starts at the exit of the tailpipe and extends rearwards as far as the rear wheel centre line.
        d) Has a half‐cone angle of 3° such that the cone has its larger diameter at the rear wheel centre line.
        Furthermore, there must be a view from above, the side, or any intermediate angle
        perpendicular to the car centre line, from which the truncated cone is not obscured by any bodywork lying more than 50mm forward of the rear wheel centre line.

        This is illustrated by Scarbs in this article:
        2012: Exhaust Position and Blown Effects

    2. Looking at the drawings and pictures, I suspect the bulge we can see on the car is bodywork. The actual exhaust pipe would finish in the trough inside the side panel and the bodywork is used to “steer” the gas to the desired point. Might even be why McLaren use a trough rather than a pipe.

      This would in effect bypass all the regulations you mention. Not saying I’m right, just my 0.02 cents worth.

      1. That’s right – the exhaust exit is in the bulge. This is bodywork and complies with the rules about one opening for exhausts.

        The rules are clear – it is one opening – but that won’t stop teams being creative. Remember a couple of years ago when we started to see the return of gills as teams carved a slit linking the gills to keep within the 1 opening rule.

        1. I think just such a slit is what can be spotted on the Caterham’s gills in these pictures as a very thin line @john-beamer

          1. Yup – otherwise those gills would not be legal!

  10. Colin Chapman would be amused…

    1. If this were a caption competition you would get my vote!

  11. Wow, thanks John for the excellent insight here. I had been wondering about what they were doing with that exhaust.

    The drawings add a lot to making it perfectly clear even to those of us who are not as technically educated.

    As you mention, I would expect Newey to have come up with something special indeed. Its clear that Red Bull is still running with high rake, and the details of the floor aroud the rear wheels point at something going on there.

  12. This is infinitely excellent. Thank you, John and Keith, for shedding some light on McLaren’s exhaust ‘nubs’.

    Im curious about the flow around the sidepods that passes underneath the nubs though… is it plausible that the same Coanda affect draws the air so tightly inwards against the gearbox and surrounding bodywork that it creates two distinct flows over this section of the car (with the exhaust flow crossing above, and then dropping down beside, the airflow that passes beneath the nubs)? If so, wouldnt this mark a significant distinction between the concepts of the McLaren and Ferrari exhaust solutions?

  13. Very interesting article, John. Many thanks.

  14. Kieth, quick off topic question if you see this.

    Will you have access to any viewing figures from Sky and the BBC when the new season starts. I would love to see the ratings comparison between the two broadcasters in an article.

  15. Great article John.
    Not sure if I am making the right observation here but do any of you think Mercedes has got something going on with the rear bodywork. It appears from pictures that a lot of scorching is happening downstream from the exhaust exits. I beleive they might be directing the exhaust gas inside the rear bodywork and having it exit just in front of the lower rear wing. It looks like there are two irregular shape pipes either side of the centreline that exit just before the upper rear bodywork finishes, just in front of the lower rear wing, there is also a higher angle portion of the lower wing behind these exits.
    Does anyone agree?

    Great site Keith, follow it daily, keep up the good work.

    1. I was looking at Mercedes and wondered if they could divert heated air through the outlets at the rear by heating it blowing it through the exhaust manifold section. Would that be possible do any of you know, and if it would be within the rules. Technically the pipes would heat the air and not the exhaust gasses.

    2. Yes – there is something going on there. There is quite a lot of bodywork around the rear crash structure which indicates they are trying to get the exhaust flow to that region. Last year it was clear that the most effective use of exhaust gasses was to seal the diffuser. That is what McLaren is attempting to do. Mercedes, it seems, are trying to use the exhaust to reduce pressure over the top of the diffuser. This reduces pressure gradient and creates more diffuser downforce. Unclear at this stage which solution is the best – and indeed how effective each is given the more stringent exhaust regs

      1. If the the air was channelled through tapered pipes and heated at the same time wouldn’t it increase the speed/pressure blowing on the diffuser in a significant way? Almost as powerful as the exhaust I reckon.

        1. John & Bobdredds, thanks for the reply.
          I agree John, I also think you may have something there Bobdredds.
          The pictures show that some exhaust gas must be exiting the sidepod upper bodywork through small exhaust port outlets (perhaps for cooling purposes), so perhaps only part of the exhaust gas in being diverted to the rear lower wing. The scorch marks indicate more work is needed to stop the bodywork from melting of catching fire.

          1. The rules say that exhaust can only exit through the 2 ehhaust pipes and nowhere else. That is why I think they are heating air by feeding it through the manifold and out the two pipes at the back. It also looks like they could be easy to switch for different configurations. Considering the efforts and details that have gone into the front wing blown diffusers and how they are applied, this looks less complicated if they can get it to work. It would also be a major step IMHO. We wont know until Melbourne ultimately but then it’s only 2 weeks away.:) It looks like a typical Ross Brawn “outside the box” idea to me.

          2. Well, it’s no problem to make the insulation that withstands exhaust gases temperature. I’m not aware if they apply it. However its around there for 30 years. Space Shuttle’s TPS is up to the challange, and beyond. Material designated as LI-900 has a bulk density of 9 pounds per cubic foot (144.2 kg/m³). It was for this reason that it was called the LI-900. It is made from 99.9% pure silica glass fibres, and 94% by volume of air. An LI-900 tile can be heated to 2200 oF (about 1478 K or 1204 celsius) and then immediately plunged into cold water and suffer no damage.
            Pity for them if they don’t use it…

  16. hi there my husband & myself have been watching f1 for manys years , & looked forward to the new season, but to our disspear u have now gone over to sky, which we dont have , & can not afford to buy sky , so looks like we lose out , very disspointed hope we have got it wrong , hoping to hear from you very soon , angela moore .

    1. you’re joking right

    2. This isn’t an official site if that’s what you’re getting at Angela.

      The news regarding Sky has been the case since the middle of last season. It’s a real shame for those who cannot afford it but if you check out this link perhaps you can find a more economical solution?

  17. Absolutely brilliant @john-beamer The best technical article i’ve read. It all makes perfect sense and you explained it very well. Thanks!

    Other than the actual exhaust pipe itself this all sounds legal and sounds like it will give relatively good performance.

  18. PLEASE READ at the top it’s has got 3 apparent options for where designers may place the exhaust exit which one of these 3 has the mclaren got

Comments are closed.