2012: Exhaust Position and Blown Effects

For 2012 the technical regulations were partly released with the 2011 regs, but there are also some late additions to be published, mainly related to the efforts of the FIA to eradicate exhaust blown diffusers.
I have seen a draft copy of the exhaust positioning rules. These rules are still subject to change because of an ongoing Technical Working Group (TWG) discussion to refine the rules. Ross Brawn in particular has made comments about possible loopholes in these regs.
Looking at what has already been proposed, I do not think he was suggesting a loop hole to allow blown diffusers, but perhaps other areas where the exhaust could be blown to benefit aero.
Currently the exhaust rules are fairly open in terms of positioning, the main stipulation being only two exhaust exits are allowed. In 2010 we saw the Red Bull RB6 reinvent the concept of blown diffusers as a way of creating downforce from the exhausts. Since then every team has relocated their old periscope format exhausts, into low exiting solutions to blow the underfloor.

2012 Rules
For 2012 we will see rules which tightly dictate the position of the last 10cm section of the exhaust pipe.
Firstly the exhaust must only transfer fluids from the engines exhaust ports to the tail pipe exit. i.e. no other gasses can enter or exit the exhaust along any point in its length. This prevents any reinterpretation of the exhaust exit or one way valves to maintain exhaust gas velocity. As Ferrari have been believed to have run on their car this year.
Then the tailpipe section is tightly defined, the last 100mm must be a round thinwall circular section, of 75mm internal diameter with no obstructions. So oval tailpipes, or pipes with internal vanes and\or slash cut exits are barred.
Then this last 100mm of pipe must be entirely within a specific area on the car. This has been highlighted on the accompanying drawings. The box seen in side elevation has to 500mm from the rear axle line and 250mm above the reference plane. This area is however very generous with a length of 700mm and height of 350mm. Thus the top of the exhaust could be as high as 600m above the reference plane, around the same height as the top of the rear tyres.
In plan view the box must be more than 200mm and less than 500mm from the cars centre line. So exhausts could not exit tightly placed along the cars centreline.
Within each of the boxes the exhaust must be positioned within a range of angles. From the side the exhaust must exit tailpipe-up and between 10 to 30 degrees from the reference plane. In plan view the tailpipe must be plus or minus 10 degrees from the cars centreline.

The red cones must not touch bodywork, the red area shows the range of where the exhausts could blow

Lastly the exhaust position is also controlled by ensuring no bodywork sits in the tail pipes wake. To measure this, an imaginary cone (diverging at 3 degrees) in line with the pipe, reaching as far back as the rear axle line must be drawn. This cone (drawn red in the illustrations) must not touch any bodywork, nor must bodywork be placed over the cone. With a typical F1 car the only bodywork in the regions behind the tailpipe are the rear wing endplates, the front portion of rear brake ducts and any central top bodywork (i.e. Red Bulls bulged central cooling exit).
Bodywork behind the rear axle can cross the cones path. Bodywork is defined as any sprung part of the car, so little can be done to deflect the exhausts plumes to reach a specific aerodynamic device.

2012 solutions
Without access to the as yet unpublished clarification on overrun engine mappings, it hard to be sure if it might still be beneficial for teams to blow bodywork for aero benefit. It may end up that it’s better to create an aero neutral exhaust position.

Aero Neutral
For a neutral exhaust position, a low & forward position within the allowable areas, blowing roughly in line with the line of the bodywork would make sense. This would follow the common approach teams used before EBDs.


For teams with low line gearbox solutions, blowing the exhausts into the void behind the engine above the gearbox may be beneficial in cutting drag. A ‘middle ground’ option could be blow towards the cars centreline above the rear impact structure, in most cases this would be fairly neutral, but the fitment of the winglet atop the crash structure for high downforce races would see it benefit from the exhaust plume.

Aero Benefit

To create an aero benefit we have to look at the influential bodywork at the back of the car, to see what could be blown advantageously.

Diffuser

Clearly it will not be possible to blow the diffuser, the forward and upwards exit of the tailpipe make the exhaust plume too high to interact with the diffuser anymore.

Beam wing

Blowing the beam wing is unlikely to be efficient

The beam wing is another possibility, this will be hard to blow with the exhaust positioning, perhaps the airflows downwash over the rear of the car could make it possible, but this doesn’t seem likely.
One possible help to creating more downwash of the exhaust plume towards the beam wing is the use of the suspension elements. The wishbones, push rod and track rod are unsprung and not counted as bodywork. Although they should be considered aero neutral, they are allowed to point up or down 5-degrees. If these elements were placed in the exhausts flows path, they could deflect the exhaust plume downward. In particular the rear leg of the top wishbone, which is already widely used a flow control device sitting high up in line with the top of the wheel and rear axle, could be used to drive some flow downwards to the rear of the car. Clearly any suspension element whether it be made of composites or titanium would need heat shielding to protect it from the +800c gasses

Rear wing

Blowing the tips of the top rear wing will add downforce, but may add a lot of drag

The upper rear wing is well within range of the exhausts especially in their higher position in side elevation. Teams could blow either towards the centre or towards the tips of the wing. Blowing the tips inboard of the endplates would create downforce, but also induce more drag from the vortices produced at the wing tip. So blowing the centre of the wing makes more sense.

Blowing the centre of the top rear wing will add downforce with less induced drag

Blowing the underside of the wing as opposed to blowing over it, should be most beneficial. Although the effect on the DRS may need to be better understood. As would any sensitivity to throttle, with the revised engine mapping rules. Practical issues of the wing being able to withstand the heat are not insurmountable, with wing sections made of Metal or with ‘Glass Ceramic Composites’ (already used for heat shielding). If the centre blowing of the top rear wing is used, we will some very high exhaust outlets. Either in tall fairings also acting as cooling outlets or sprouting from the side of the engine cover.

Brake Ducts

Blowing the rear brake ducts will add downforce directly into the tyres

Also blowing the rear brake ducts is an avenue worth exploring. The exhaust geometry doesn’t work quite so well in this area. Brake duct vanes, which we have seen proliferate over the past few years are allowed to be 120mm inboard of the rear wheel, roughly in line with the wheel and can protrude forwards the front perimeter of the tyre. But as some of the brake duct is ahead of the rear axle line there is less surface to blow on.
This might still be better than rear wing blowing, as the downforce is produced directly on the unsprung wheel, rather than passing through the suspension. The benefits of this over rear wing blowing would need a simulation to establish the better path.
Practicalities of heat shielding the rear brake ducts are already understood from EBDs which already apply of the exhaust plume over their surfaces. Also tricky would the positioning of the brake cooling snorkel, but again this is not insurmountable.

Drag reduction

Blowing outside the rear wing endplates will reduce drag

One leftfield idea would be blowing outside of the rear wing endplates. This would not produce downforce, but reduce drag. Just as we see slots in the endplate to reduce the vortices created at the wing tip. Blowing the exhaust would reduce drag when the exhausts are blowing hard. Theoretically when the car is in accelerating out of a turn or in a straight-line and needs as little drag as possible. The beauty of this idea is when the driver lifts off the throttle for a corner, even with limits on overrun mapping the slower exhaust plume would reduce its effect, increase drag again. This might be a less sensitive, but still effective position for the exhaust plumes. But its complications might not be worth the drag benefit.

Summary

What’s clear is we will see a variety of exhaust positions being tested and raced next year. Certainly the exhaust position we see on the launch car will not always be what we will see in Australia for the first race.

29 thoughts on “2012: Exhaust Position and Blown Effects

  1. Great work as usual, Craig, reading the regs is never as good as an image of what is and isn’t permissible.

    Something that occurred to me the other day is that the lessons learned about airbox spillage under hot- or cold-blowing regimes aren’t going to go away, and we’ll still hear funny noises on the over-run next year as the engines are used to fine-tune the flow to the rear wing and Coke-bottle even without the direct influence of squirting exhausts through the diffuser area. Maybe these are even the loopholes that Ross Brawn’s talking about.

  2. I think the use of exhaust energy to add performance should be allowed! The one thing that shouldn’t be allowed is to use more fuel to add aero performance. Why they try to kill exhaust energy usage considering the fact that it is basically free?

  3. looking at the drawings, I had an idea to use the centerline exhaust blowing of the rear wing that you described, and, based upon almost no understanding of the underlying principles, i would think that the exhaust would act like a modified F-Duct on the rear wing, thus decreasing downforce the faster the car went. And because it’s purely based upon throttle position, I can see no problem with controlling the effects for fast or slow corners. In addition, I would think that the DRS winglet would help this effect along because it would force the flow from the backside of the wing more horizontally at the top of the wing, and thus reduce downforce even more. But, to repeat, I am no aero expert and have no training on the subject. I simply thought that it would be another solution to help straight-line speed/top-end.

    • I can see what you are are envisaging. However, I dont think it will work.

      I would expect blowing the wing will increase flow over it, increasing downforce. I guess at a certain angle the flow could drive the wing into astalled condition where the flow is no longer attached to it. But this seems difficult to achieve consistently

      If blowing the centre of the wing could detach the flow and reduce downforce, this would have very little effect on drag and thus not increase top speed.

  4. Will the exhaust gasses really have that big an effect being so far away from the rear wing? Surely the amount of gas flowing through the exhaust will have a negligible effect, especially at high speed? i’m no engineer (or aerodynamicist!) but I can’t believe they’ll be doing anything other than trying to minimise the drag the exits cause and trying not to disturb the airflow to the wing?

    • The current EBDs are nearly 70cm from the backof the diffuser and they have huge effect. Having the 2012 exhaust 50cm from the rear wing, would be a more powerful effect, albeit acting on a less effective aero device.

  5. Further to Ryan’s comments (and his modest claims to have ‘almost no understanding of the underlying principles’) and to prove my absolute naiveté in the realms of aerodynamics, I submit the following:
    Isn’t blowing gasses from one ‘sprung’ part of the bodywork to another rather like sitting on a yacht on a calm day, and blowing the sail? Or perhaps like getting the rear passengers of a car to push on the back of the front seats to help you up a steep hill?
    Or is it more like being on a yacht on a windy day and switching on a fan aimed at 90degrees across the wind flowing into the sail, thus ‘disrupting’ the normal flow? This second suggestion, as ridiculous as I may have made it sound, makes more sense to me – in F1 terms I guess I’m asking if exhaust gases are used to ‘interact with and disrupt’ normal aerodynamic flow over the car – at least, that’s what I think I’m asking.
    Thanks at the very least for trying to demystify the witchcraft of aero-science.

    • Firstly blowing any aero surface on the car from the car will have an aero effect (as EBDs do now). So its similar to sitting at the back of yacht with a big fan pointing at the sail.
      On the point of using the exhaust to disrupt airflow over the wings surface, I dont think its going to be effctive. The exhaust flow will tend to follow the wing (coanda effect) and increase flow over it. Which will increase downforce.

      • I’m fairly certain that sitting on a yacht on a calm day with just a fan blowing on your sail will result in 0 movement. Any force generated by the air hitting the sail will be offset by the force of the fan accelerating the air…

        Watch Mythbusters – truck full of pigeons episode🙂

      • citing the Mythbusters, they also did a full episode on the very topic about which you speak. I believe it was called ‘Blow your own sail’ but I could be mistaken. Definitely worth a look though

      • I may be wrong (again no knowledge of aerodynamics), but an fan pointed obliquely at the sail would result in overall movement of the yacht. This would fit the principle better surely? The aim of blowing an aero device isn’t to move the car forward but obliquely downward.

  6. On another note, I have been thinking about this for quite some time, how does the thermal expansion and then subsequent contraction of gases influence aerodynamics? As in cold air flows in through the radiators, expands in the process and then flows out of the outlets and contracts again. Is that why RBR have one single outlet placed to release under the rear wing were there is a natural low pressure area? And how much does that same principle apply to hot exhaust gases? How much volume do the have when they exit the exhaust and how hot and how much volume do they still have after reaching the end of the car? Is that also why the exhaust blown diffuser is more efficient when blown underneath the diffuser because of the exhaust gases entering the diffuser at a certain volume and then cooling down and creating a increased lower pressure underneath the diffuser?

    Would like to hear your thoughts on it.🙂

  7. You write: “But as some of the brake duct is ahead of the rear axle line there is less surface to blow on.”
    That I don’t understand; since the brake duct is an unsprung part, the exhaust is allowed to blow on it regardless of position relative to the rear axle line, right?

    Then, your proposal for drag reduction; would the gain in drag reduction not be offset by the increased drag caused by the exhaust position itself; as the periscope would protrude quite far from the sidepod and sits in (as far as I can judge) otherwise clean air?

    Last, do you think there could be any benefits gained through using the exhaust flow in ‘cleaning up’ the flow around the rear wheels? As I understood this was an added benefit of RB’s EBD this year.

    • Theres a classic case of the rules getting conbfused with themselves. I woudl regard the brake ducts as bodywork and hence cannot be blown until the rear axle line. Even though, as you say they are considered unsprung.

      If I were a team I’d be asking Charlie for a clarification on if this is the case.

      As if you could blow the front protruding section of brake duct, then that would be a VERY powerful solution. The rear wing is 35cm long the brake duct fin could be as much as 50cm long! plus the exhausts can blow much closer to this section of ‘bodywork’.

      • This is pretty much exactly the same question I was going to ask!

        The rear brake ducts have seen a huge amount of development recently, if the teams can clarify what is and isn’t allowed around here surely the direct benefit straight on to the rear tyres is by far the most beneficial of the solutions proposed?

        When I first thought of the periscope exhausts though my initial ideas were blowing onto the centre line of the body work (as clean up), or possibly the beam wing (but I didn’t realise the latter would be so drag-y or inefficient).

        This is such good work Scarbs, you’re well ahead of the game here, keep it coming!!

        Just out of curiosity, it must have felt great when you heard about the TWG and a team enquiring about the ‘See-Saw Splitter’ solution?!? You’re having a direct impact on all of the teams development basically!

      • There is several other cool things with blowing on the brake ducts. due to roll and aero pushing the car down the gains will variate with speed and if its a corner.

        Matsnorway

  8. I would have thought brake ducts wouldn’t be an issue, as they form part of the ‘unsprung’ mass of the vehicle, do they not….

    I think you may see quite a number of aero -neutral solutions pre-season, until their effect on track is better understood. I’m sure we’ll see a raft of revisions early on, until most teams converge towards the solution of the team that got it right first.

    I suppose the teams only need small panels screwed to the rear deck, with different outlet locations, and altered tailpipes to test different configurations.

    Craig, how much do you think the exhaust position next year will affect the overall aero-map of the cars? And what changes upstream do you think will be required? I’m thinking in regards to the L shape side-pod philosophy of this year’s McLaren…

    Cheers,

    Pat

  9. I find F1 aero and engineering really interesting but only have a small amount of knowledge on these subjects, so please excuse me if the following questions seem silly. From what I’ve heard on tv the dry tyres come out of their blankets at around 100 degrees Celsius, so I assume that this is close to their ideal operating temperature. Would trying to blow the brake ducts with gases of over 800 degrees Celsius have an effect on rear tyre temperature? Also what would be the effect on the actual temperature of the brakes themselves?

  10. So it seems that Williams was testing blowing the middle of the rear wing today in the Abu Dhabi “young drivers” test. Your article is a great way to make sense of that!

    Will take some getting used to seeing that sort of solutions, but not as much as blowing the ends of that wing would.

  11. Could the exhaust outlet be used to pull air through the radiators, like an air multiplier, allowing more compact radiators and thus more compact sidepods?

    Could move the radiators more ‘inboard’ to the chassis and possibly combine the double-floor and u-pod concepts – possibly even switching according to track type eg. exposed u-pod for drag deduction on faster tracks, covered u-pod (looking more conventional) with through body airflow (exiting around beam wing?) for high-downforce tracks.

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  15. I was wandering, how big is the downward reaction force created by the exhaust gasses exciting upward at an angle wrt the reference plane. It is probably quite small, compared to the overall downforce generated by the car. If I remember correctly, during his years in McLaren, Newey was trying to use the reaction force of the rear exciting gasses. Something like a jet, although not very strong one. Can you make some estimation of the mass*velocity of the gasses at full throttle? If it is significant it might make sense to alter the engine mapping again, to add that to the downforse in corner.

  16. it would be interesting to ask Mercedes and Williams about their new exhaust positioning used in Abu Dhabi testing session last year. They were the first teams to change the bodywork

  17. Does the regulation says anything about materials ( alloys ) that can be used in exhausts ?
    If not i see oportunity to trick rules out by using Shape-memory alloys :>

    Conditions are good enought and i don’t think anyone would measure angles of hot exhausts pipes ( at least for some time )

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