How the Red Bull RB8’s exhaust feeds its diffuser

F1 technology

To no-one’s surprise the race-specification exhaust for the Red Bull RB8 appeared on the penultimate day of the last pre-season test.

The team went to considerable lengths to cover it up, as the video above shows. But now the design has been seen we can get a look at how it works.

As the FIA has restricted where teams can place their exhausts, designers are striving to continue using the hot air to make their diffusers more powerful.

Red Bull’s approach is similar in principle to McLaren’s exhaust concept in that it tries to pull the exhaust plume downwards from the exhaust exit over the side of the diffuser to create a sealing effect.

The Red Bull design appears quite different and more elegant. But we won?t know until Melbourne whether it is more effective.

The Red Bull RB8 exhaust

Red Bull RB8 exhaust diagram

Red Bull RB8 exhaust diagram

The first illustration shows Red Bull?s new set-up. I?ve left out the pull-rod suspension arm and lower wishbones to make the image a little clearer.

The grey zone where the exhaust exits is covered in heat-resistant paint to prevent damage to the carbon fibre. The exit contains a channel indent to drag the plume downwards using the Coanda effect, as described in the McLaren exhaust article.

This area is shaped to continue to drag the exhaust gas downwards towards the diffuser. In addition, air coming over the sidepod is also used to create a high pressure zone around the exhaust exit, further helping the Coanda effect and shaping the exhaust plume. The red lines show the exhaust flow.

The issue designers face is that this potentially interferes with how the undercut sidepod works.

Over the past couple of years teams have aggressively undercut the sidepod to feed fast-flowing air to the coke bottle zone. This helps the diffuser to be more effective by creating a low pressure zone above it, which in turn reduces flow separation in the diffuser.

Dragging the exhaust plume to the floor will reduce the effectiveness of the coke bottle zone. The bulge in McLaren’s exhausts is designed to direct the exhaust gas over this flow.

Red Bull have adopted a different solution which is visible in the image. They have carved a duct at the bottom of the sidepod for the undercut airflow to go through. This duct exits in the coke bottle zone, missing the exhaust plume.

Replicating the exhaust-blown diffuser effect

Red Bull RB8 exhaust diagram

Red Bull RB8 exhaust diagram

The second illustration shows a similar picture of the RB8’s exhausts in plan view.

The exhaust exit is circled in yellow and again I’ve added the exhaust flow (red) and undercut flow (blue).

From this angle it is possible to see the shape of the exhaust indent in the bodywork. It is built in such a way that the exhaust gas appears to split – one stream spills over the side towards a vane on the floor ahead of the inner part of the rear tyre.

This will create a vortex and is primarily aimed at sealing the diffuser – this part replicates the effect of last year’s exhaust blown diffuser.

The second stream adds energy over the diffuser, which will help reduce the pressure gradient above the diffuser exit and hence reduce the risk of airflow separation under the car.

It is thought by some that the exhaust flow may partly feed a duct in the floor that houses the starter motor hole. However, it is unclear at this point whether this is for exhaust gasses or air flowing through the sidepod duct. Given the restrictions on starter motor hole size the effect is likely to be small.

As exhaust solutions are developed we’ll get a feel for the most effective solution. Last year teams quickly converged on Red Bull?s solution to optimise the exhaust blown diffuser.

Ferrari technical director Pat Fry suggested the same could happen again this year, assuming Red Bull’s design is considered legal, telling Sky: “It comes down to what re-ingested exhaust gas is really and that’s a question for Charlie [Whiting].

“I think it’s the obvious direction to go in. We gave it a shot; we didn’t quite get it right. The issues we had, we weren’t going to solve for at least the first four races, so that’s why we had to back up and change course.”

At this point the Red Bull solution is visually neater but doesn?t completely eliminate the exhaust/undercut interaction. McLaren?s solution likely does a better job in this respect but could face trade-offs on drag or quality of exhaust flow to the diffuser. The first weekend of running in Melbourne will yield more clues.

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Illustrations ?? John Beamer for F1 Fanatic

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50 comments on How the Red Bull RB8’s exhaust feeds its diffuser

  1. DrF (@drf) said on 14th March 2012, 17:34

    Amazing amount of effort to go to for what seems (to me at least) to be very little gain.

    And it’s against the spirit of fairness that the FIA are (supposed to be) endorsing. Once again the wealthier teams can afford to explore the edges of performance while the newer teams have to make do.

    • Robbie (@robbie) said on 15th March 2012, 15:08

      At least the newer teams can take comfort that the benefits if EBD that the wealthier teams particularly had gotten a good handle on, have now been curtailed. While Red Bull and Mac seem to be perhaps the ones who will still benefit a little bit from channeling their exhaust gases, the benefit is much less than last year, and the stability in the rules otherwise should help the lesser teams. I think the greatly restricted parameters of what they can do with the exhaust should also help the lesser teams more easily duplicate the wealthier teams efforts.

  2. Aldoid said on 14th March 2012, 22:15

    I know secrecy has always been part of F1 but Red Bull have taken it to a whole new level. They’re a little hypocritical too if you ask me… Complaining about McLaren copying them last year, when I still have photos of Vettel & Webber practically climbing into the McLaren cockpit (& various other team members crowding around snapping photos) trying to get to grips with how the f-duct worked. The way those guys moan, you’d think they’d never try to copy anyone themselves. Obviously we know better though.

    • Robbie (@robbie) said on 15th March 2012, 15:03

      While I take your point, I think that what happens is that before the season starts the teams have a better chance of hiding things from others with things like the screens in the video. I think that is fully within their rights and they should, having spent tons of money trying to find an edge, try to hide their secrets for as long as possible while they can. I think we all know, and they all know, that once the season begins (Friday practice) and all the teams have their latest greatest kit out there for the world to see, there is only so much hiding anyone can do any longer. And then yes it is fair game and you see drivers checking out each others cars in parc ferme etc etc. But while they can control the viewing of their car, they are going to do it.

      • Aldoid said on 15th March 2012, 17:56

        I don’t disagree with you… not even a little bit. My complaint isn’t about them hiding their innovations,it’s more about them acting as if they’re not guilty of blatantly trying to copy others as well. The way they spoke with disdain about being copied, you’d think they’d refrain from doing the same… & of course they won’t. In light of this, my position is that they should complain less, that’s all.

  3. Amaury (@joematers) said on 14th March 2012, 23:15

    This seems to be a similar way of directing the exhaust gases like Sauber rather than the McLaren. Looking forward to this season!!!

  4. gDog said on 15th March 2012, 2:37

    I think Iran could learn a thing or two from the Red Bull boys about how to conceal their latest tricks from prying eyes.

    • montreal95 (@montreal95) said on 15th March 2012, 19:17

      Mclaren should hire CIA and Mossad, then we’d see what RBR’s secrecy is worth. Should be no problem at all-just tell them you suspect they’re hiding a nuclear weapon in there. Since many Newey’s cars are indeed an F1’s equivalent of a nuclear weapon it wouldn’t even be a lie!

  5. Brando said on 15th March 2012, 14:34

    This is why I love F1!!!

  6. smudgersmith1 (@smudgersmith1) said on 15th March 2012, 20:49

    Whatever the merits of the system, this was pathetic to watch, the FIA need to step in and say, ‘ Guys, once you break cover at the test you break cover’, to see mechanics scurrying around with makeshift barriers to prevent pictures was ridiculous, reminds me of a school boy covering up his answers to an exam….grow up.

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