Technical review: European Grand Prix

Mark Webber, Red Bull, Valencia, 2010

A raft of updates appeared on several of the front-running cars in Valencia.

As in 2009 when Brawn dominated the first half of the season with its double diffuser, Red Bull has enjoyed a similar performance advantage this year. The key difference is that in the first few races no-one could put a finger on why the RB6 was so quick.

Having previously suspected a trick ride-height control system was responsible for the RB6′s speed, the teams are now trying to emulate its clever exhaust and diffuser arrangement.

What is different about Red Bull?

Sebastian Vettel, Red Bull, Valencia, 2010

At the rear of the RB6 there we find an unusual pullrod suspension set-up. Pushrod suspension, used by most other teams, connects from the lower part of the upright to a point roughly a foot above the floor, effectively ‘pushing’ the rocker, which activates a spring and damper system. A pullrod does the opposite.

This creates more space on the inside of the lower upright (there is no connecting arm) but potentially compromises the diffuser as the rocker is close the floor where the double diffuser inlet should be. At the start of the season many thought Newey would revert to a traditional pushrod system but he didn’t, believing that the pullrod allows tighter rear end packaging that gives a net increase in downforce (look at how tight the Red Bull is around the engine cover).

Second is the placement of exhausts low down on top of the diffuser. The theory is that the fast exhaust gasses help keep airflow attached in the diffuser which increases downforce by (a) making the diffuser work better and (b) allowing aerodynamicists to run a more extreme design (i.e., a bigger diffuser). It is these so-called exhaust blown diffusers that rival teams now believe is the root cause of Red Bull’s considerable speed advantage.

The difficulty in emulating Red Bull’s design is that the speed of the exhaust gas is variable. When the driver is on the throttle the gas speed is high. During braking it is is low. This variance causes inconsistency in diffuser downforce (effectively reducing downforce when cornering, which is when you need it most) so in the early 2000s constructors abandoned similar designs in favour of more stable downforce.

In addition there are significant heat problems too – the carbon fibre bodywork won’t take kindly to being blasted for 90 minutes with 800C fumes. In one sense it is no surprise that Newey had the vision to bring back the exhaust-driven diffuser given the last car to sport it before the RB6 was the 2003 McLaren MP4-18 – another Newey car.

How does Red Bull’s diffuser work?

The RB6 exhausts exit immediately below the forward lower rear wishbone, a few centimetres in front of the rear tyres. About 5-10cm aft of the exhaust exit is a small inlet slit that feeds the outer channel of the diffuser. This allows some of the exhaust gas to bleed into the diffuser channel adding to the energy of the air inside the diffuser, which helps downforce. It works in a similar fashion to the slots many teams have in the front wing endplates.

The rest of the gas passes the slot and blows over the outer edge of the diffuser aft of the rear tyre. Higher air speed equals lower air pressure, so as the exhaust gasses blow over the diffuser the pressure gradient behind the diffuser is lower than it would be otherwise. The diffuser is less likely to stall so downforce is higher.

Airflow in this area is often affected by the bulk of the rear tyres which creates unpredictable and turbulent flow. The exhaust-driven diffuser reattaches and smooths the flow behind tyres.

The detail at the diffuser trailing edge is critical for managing the airflow. Over the past few races Red Bull has been extremely active developing this area. The standard solution is to place a gurney flap on the rear edge to scavenge the air more effectively from the diffuser.

Ferrari, Renault and Mercedes

Fernando Alonso, Ferrari, Valencia, 2010

At Valencia all of Ferrari, Renault and Mercedes sported new exhaust arrangements.

The Ferrari upgrade was the most high-profile and extensive. The exhaust was moved to the floor to an opening below the sidepods. The Scuderia sported a raised gearbox and attached the lower wishbone suspension arms slightly higher to protect them from the exhaust heat.

In addition the radiators and oil cooler were updated partly to help cool what the engine but also to make the coke-bottle zone more effective. Massa’s was the only car that sported the full upgrade as Alonso was in the middle of a four-race gearbox cycle.

Unlike the Red Bull solution Ferrari did not cut a slit into the diffuser. This meant that exhaust gas blew over the top of the diffuser only. The diffuser looked largely unchanged from the Canada version except for the addition of a gurney flap.

Despite Alonso and Massa failing to score a front row grid slot the upgrade was thought to have performed well. Failure to properly dial in the soft tyres in qualifying that prevented Alonso from being closer to pole although it is unlikely that had the softs worked he’d have usurped either of the Red Bulls.

Vitaly Petrov, Renault, Valencia, 2010

Mercedes’ and Renault’s implementations were similar to Ferrari’s albeit with some subtle differences to manage airflow. Mercedes added some vanes atop the diffuser to help guide air past the tyre to prevent it overheating. Renault’s exhaust exit blew onto a heat shield that was then directed over the diffuser where a gurney helped scavenge airflow from under the car.

Implementing exhaust blown diffusers present three engineering challenges. First is re-routing the exhausts – not a simple task. Each cylinder has an exhaust exit that feeds into a primary pipe. The exhaust lengths are tuned to the maximise engine power and re-routing the pipe to the floor requires meticulous engineering to ensure no loss of power.

Second is ensuring that the back of the car can withstand the heat generated by the exhausts. The suspension is covered with a protective heat shield, and heat responsive paint and sensors adorned the floor and rear wing endplates of the cars in practice.

Indeed Mercedes had to modify its exhaust exit before qualifying because of excess heat. This was where McLaren ran into trouble with their MP4-18 seven years ago – the car couldn’t run for more than five laps without setting its rear bodywork on fire. The team are planning to run their version of the exhaust package at Silverstone this weekend.

The third greatest challenge is packaging at the rear. The flow in this area is important and if suspension or other components obstruct the exhaust gasses then the effect of the exhaust gases reduces.

These three factors make retrofitting an exhaust blown diffuser to a car a significant challenge. As teams understand better how it works, expect them to get closer to Red Bull. However expect Red Bull to maintain an advantage as McLaren do with their F-duct.

Other upgrades

Mark Webber, Red Bull, Valencia, 2010

While teams are busy copying Red Bull the Milton Keynes-based outfit isn’t standing still. The team brought a revised F-duct as well as a new diffuser to the European Grand Prix. The main diffuser inlet was changed slightly and the outer arches were more pronounced.

Webber’s crash gave us a great insight into how the RB6 diffuser is fed from the floor. It is believed to have only been caught on video by FOM’s cameraman, who F1 Fanatic spoke to at the Goodwood Festival of Speed. He mentioned that one photographer had been shooting the straight until about ten second before the crash, when he walked away. A pity, as it could have revealed more of the secrets of the most competitive car on the grid.

However the video shows that as the RB6′s under-body narrows an inlet with a vane and large radius feeds the diffuser. The vanes extend the width of the step plane allowing a higher volume of air into the diffuser increasing downforce. This is now standard solution across the grid having being pioneered by McLaren at the start of the year.

Valencia was also the first track where Red Bull raced the F-duct – previously it had only appeared in practice at Turkey. As discussed before the F-duct is a pneumatic switch, with the driver turning the duct on or off with his hand or knee. The Red Bull system was the same as that run at Istanbul Park with a couple of internal tweaks to ensure downforce didn’t wash off when the ‘switch’ was closed.

McLaren is saving its big upgrade for Silverstone so made very few changes for Valencia. The only noticeable difference was a slight tweak to the F-duct cockpit inlet which is now by the driver’s hand, rather than next to his knee as previously. This is now becoming standard placement for all the teams and probably gives easiest access to the cockpit duct.

One significant area of development since the start of the season has been brake ducts. After the banning of outboard wheel fairings teams are now trying to recreate the flow effect of the fairing with ducts and vanes inboard of the tyre.

Teams are trying to get air to exit through the wheel smoothly and to direct it away from the sidepods. This minimises wheel drag and prevents any turbulent air interfering with the sidepod undercuts. In Valencia Red Bull produced brake ducts that stretched to the front of the tyre, allowing better air control through the tyre.

Renault

Robert Kubica, Renault, Valencia, 2010

After a torrid off-season where Renault CEO Carlos Ghosn came perilously close to shutting the team down before selling it to a venture capital fund, many predicted that the R30 would toil at the rear end of the grid.

However, the technical team has infused the Enstone-based outfit with new purpose and the rate has of development has been on par with McLaren and Red Bull, as proved by how quickly the team brought an exhaust blown diffuser to the car.

Renault has apparently had 22 iterations of its front wing, with close to six different endplate designs. Valencia was no different as it brought yet another revised endplate. It was based on the version raced at Turkey (the one at Montreal was a special low downforce incarnation) with a gap between the inboard cascade and the outer winglet above the footplate. This fed a different brake duct configuration no doubt to refine the airflow around the tyres.

Silverstone predictions

Ever since the RB6 stretched its legs in high-speed corners at the start of the season Silverstone has been seen as Red Bull’s race to lose. Again in Valencia the car was considerably quicker than the rest of the grid in sector 3 where there were more high-speed corners.

So what’s in store for the Silverstone? Based on Valencia there isn’t a huge amount for Red Bull to be worried about. Publicly the team has said that it won’t be bringing a huge update to its home Grand Prix while McLaren has announced it will run its revised rear package.

Odds are it will be a two-horse race. Don’t forget Turkey where the MP4-25 was quick with its conventional exhaust lay out. If the exhaust-driven diffuser is worth the half a second that most in the pit lane think then McLaren has a real shot at winning – but as we’ve seen it’s a big ask to make it reliable and efficient from its very first appearance. Also expect Ferrari in particular to be close to pace as it processes the Valencia data and starts to optimise its layout.

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32 comments on Technical review: European Grand Prix

  1. Maverick_232 said on 5th July 2010, 13:03

    Brilliant article. Thank you

  2. Sush Meerkat said on 5th July 2010, 13:34

    Lets not forget that Ted Kravitz mentioned the Renault looked like it was designed around the blown exhaust, thats how good their development rate has been.

    • Renault have been truly impressive this year. The development rate for the team has been amazing, especially given how close they were to quitting over the winter.

      The only real shame is they are surely getting to the point where they’ll want to focus on 2011 rather than fight a 2010 campaign they’re not going to win.

    • BasCB (@bascb) said on 5th July 2010, 21:05

      Renault really have been impressive this year. Their car keeps being improved each race, the exhausts blowing over the diffusor seem to work wonderfully for them.

  3. you should do a photo-version for morons like me, showing clearly with mspaint what on earth the unusual pullrod is :)

  4. Patrickl said on 5th July 2010, 14:13

    “As in 2009 when Brawn dominated the first half of the season with its double diffuser, Red Bull has enjoyed a similar performance advantage this year.”

    BrawnGP didn’t enjoy a massive perfrmance advantage in 2009. Not over Red Bull at least. Red Bull utterly underachieved in the first 7 races.

    As they did again this year.

    • Scribe (@scribe) said on 5th July 2010, 16:36

      Brawn had a substantial advantage that started dropping significantly only because they had poor development. A dominant 1-2 in Spain rather prooves this.

      In Australia it was estimaited that they might well have been up to half a second quicker than the rest of the feild.

      • Patrickl said on 5th July 2010, 17:47

        Yet Vettel was only 4 seconds behind Button at the time that Vettel rammed into Kubica. Vettel could at the very least have come in 3rd.

        Vettel also lost Malaysia because of that crash (and because he spun out)

        Then China where Red Bull dominated.

        Bahrain, Toyota should have won, but they completely messed it up. Vettel failed too (Button overtook Hamilton and Vettel could not and was stuck in P4). Pretty much the same thing in Spain, when Vettel couldn’t povertake Massa. Turkey another driver error where he trew away the win.

        etc etc etc

        At the very least the Red Bull cars were at the same pace as the the Brawns even in the first half of the season. Both the team and Vettel kept messing it up in the first seven races though.

        They were unlucky that Webber broke his leg and took a while to completely recover. Barrichello wasn’t much help for BrawnGP in the first half of the season either.

        Either way it’s completely different from the advantage of almost a second that Red Bull have had over the other teams.

  5. Dan N said on 5th July 2010, 14:27

    Been wondering how the Pullrod system worked. Great article, thanks for explaining it.

  6. As always, very interesting article.

  7. Eric said on 5th July 2010, 16:00

    totally enjoyed that read Keith, thanks.

  8. MinusTwo said on 5th July 2010, 16:13

    I LOVE these articles. I can tell how much work goes into them.

    Thank you so much.

  9. I was kind of under the impression that the move-away from the classic old-school blown diffusers was not so much about the throttle-off instability problem, but in the end more to do with engine manufacturers increasingly needing shorter and shorter exhaust lengths as they revved higher and higher … this of course was back when F1 was really F1, pre rev-limit, 21k V10s, yowzer.

    (anyone that knows anything about engines could jump in here and put me straight on that).

    Therefore, the new blown diffusers aren’t really like their ancestors that deeply drove down and through the car and diffuser, they are more about tidying and directing airflow at the rear end, to help create an efficient environment for a reasonably large diffuser to live in … not actually ‘driving it’ as such, well at least not like they used to.

    Either way, you can bet someone got sent down into the MTC basement with a torch to have a proper look at the last few Newey blown diffuser McLarens, see if there are any institutionally-forgotten neat tricks hiding in the cobwebs.

    • Scribe (@scribe) said on 5th July 2010, 16:38

      If Turbos really come back expect to see exhaust driven diffuser technology really explode. Smoother flow from lower revving engines make the whole system massivley more efficient.

  10. christopheraser said on 5th July 2010, 16:32

    What about williams?

    They clearly made steps at Valencia.

  11. Fer no.65 said on 5th July 2010, 19:20

    brilliant article!…

    it was tough read as i tried to understand everything written here (sometimes it’s too difficult) but very nice anyway!!!

  12. DaveW said on 5th July 2010, 19:30

    Great piece. Learning of the compromises Ferrari and Mercedes had to make to the design may explain the disappointing results of their blown diffuser mods. It would seem to me that cutting the slits on the side of the diffuser is essential to the gains—this was the major effect teams sought by putting the exhaust inside the diffuser itself a few years back, which is what the MPF-18 did. We know that car was a rocketship, in various senses. I do think McLaren must have much data from the MPR-18 experiments, and from watching what Newey has done now, and from the fantastic view of the RB6 underbody, are in a position to come out with a pretty amazing update. I expect something properly radical from McLaren.

    • James_mc (@james_mc) said on 5th July 2010, 20:58

      Yeah, that is a very good point. I remember reading a piece (possibly on here actually), about F1 cars that never raced and it said that the MP4-18, despite being one of the most famous, was also the hardest to write about because at the time it was still a big influence on McLaren design. I presume that has changed somewhat now, not much in the way of anteaters in the McLaren garage these days!

  13. John Beamer said on 5th July 2010, 21:06

    Thanks for the kind comments — much appreciated. One thing I have heard (I think it was from James Allen’s site is that Red Bull has an engine setting that allows that maximizes the EBD. I haven’t found out if it is true yet but here is what he said.

    ” One interesting observation is that Red Bull has a setting on the engine, whereby the ignition is retarded on the over run, which maintains exhaust gas pressure even when the driver lifts off the throttle. This maintains the performance of the blown diffuser and keeps the downforce up when it’s most needed. It’s not something you can do for more than a lap or two as it damages the engine, but it gives that vital fraction of a second which keeps Red Bull ahead of the rest in qualifying.”

    • BasCB (@bascb) said on 5th July 2010, 21:13

      Is that maybe one of the reasons they were secretive with the problems Vettel had in the Bahrain race, blaming it on the spark-plug?

  14. BasCB (@bascb) said on 5th July 2010, 21:11

    Thanks John, nice insights there, keep up these reviews.

    A shame no fotografer was closer, to that accident to get some nice shots of its details!

    I think Ferrari will make their 2nd step of development worthwhile after learning a lot from using it in Valencia (where they did not gain a lot, but more importantly did not lose a lot by testing it for the whole race on both cars).
    If get it right, Alonso won’t have the new gearbox for Silverstone as well. So Ferrari will be able to compare 2 different car versions for both races?

    McLaren will also be great if they make the rear end work from the start. They do have the most recent experience of doing something like that, as well as extensive knowledge of Neweys thinking. Like DaveW mentinos, they might have had a look back at designs of the MP4-18 etc. cars to learn before incorporating it into their car.

  15. theRoswellite said on 5th July 2010, 23:04

    FABULOUS, Fabulous, fabulous….

    Thanks John, and also to Keith for the ongoing improvements over the past year. Is there a better F1 site on the Web, if so, I’ll pass.

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