Will Gray

Tech Talk: Should Red Bull be worried?

Will Gray

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Red Bull's blown diffuser concept has kept their rivals' design rooms busy ever since it appeared this year - so after some of them finally introduced their versions in Valencia should Red Bull be worried?

Blown diffusers are not new to Formula One, having been regularly used on cars between the mid 1980s and mid 1990s. The concept is simple. The air flowing over and under the car gets twisted and turned along the way, losing energy as it goes. By the time it gets to the diffuser, the air is lacking energy, but it still has to perform one of the most important downforce producing tasks as turning vanes steer it out into the turbulent trailing wake of the car.

The more energy the air has, the more it can be manipulated inside the diffuser and the more it can cope with the tight curves it is asked to follow to gain vital downforce. If it lacks energy, the flow separates from the surface and damages the downforce significantly. Blowing fast-moving, high-energy air from the exhausts into the diffuser area can re-invigorate this tired air and enable it to handle more challenging routes that will ultimately produce more downforce.

The blown diffusers come with a drawback - which is why they fell out of favour - in that exhaust output is based on the engine throttle, so the airflow changes with throttle position. When a driver accelerates, the airflow through the exhaust and into the diffuser will speed up and create more downforce; when he takes his foot off the throttle, the downforce will reduce.

That unstable downforce creates a car with significantly different behaviour to one without the 'active' diffuser, and some drivers may need time to get used to the pitch sensitivity it creates - Vitaly Petrov, of Renault, admitted as much this weekend.

However, with the benefit rumoured to be upwards of 0.5s per lap, the drivers just have to get used to it, and Ferrari, Renault and Mercedes introduced their own concepts of the blown diffuser for Valencia. McLaren, meanwhile, will be bringing theirs in at Silverstone after running a straight-line test session to check it works.

Designing these new systems is not easy - and that is why Red Bull are not running scared just yet.

Exhausts cannot simply be re-routed to find a good solution. Like McLaren's f-duct, which others have struggled to perfect, the blown diffuser concept is complex and there are also many parts in that region of the car that have to be considered before the design can run.

Exhaust gases exit at around 950 degrees C and then have to pass through carbon fibre bodywork. Exhausts, which can glow red hot, are coated in ceramics for insulation but the gases must still now flow through unprotected carbon fibre areas and could cause damage - leading Ferrari to use special coloured temperature strips in this region to keep an eye on how hot it got in early Valencia runs.

Wishbones from the rear suspension can also get in the way, but this is where Red Bull is significantly different. The team suffered from their unique pull-rod suspension system last year when it restricted the development potential of the double diffuser.

 It was a surprise when they kept it for this season, but the concept has been retained with the blown diffuser in mind, and other teams may have to make compromises to their more standard suspension design that could reduce the potential downforce benefits.

It is also not just a case of putting the flow into the diffuser - knowing where to feed it in and how to manipulate it once there requires in-depth knowledge of flow regimes - meaning a good CFD department is vital.

The aim is two-fold: to move the wake from the rear wheels outwards and to re-energise the air inside the diffuser. And details are vital. Red Bull has got to the point where they are modifying small elements of the diffuser to refine the flow of the exhaust gases, most notably creating a pointed extrusion on the top outer edge of the diffuser to help the energy-filled exhaust flow drag the tired air out of the diffuser and around the tyre and give more consistent downforce.

McLaren engineering director Paddy Lowe admitted recently: "All the rest of the teams are playing catch-up in that area.

"It's quite a significant performance step but it has been a pretty massive project, not least because you've got a new exhaust system and that has many challenges, especially when you try to do it quickly. It's (tough) to hit the ground running with a system like that when we don't have any proper track testing."

A look at the numbers from Valencia proves just that. Canada was a tough track for Red Bull, and they failed to get pole, but compared to when they were on form, in Turkey, Ferrari and Renault have improved, but not at the levels expected, while Mercedes have dropped away.

Ross Brawn's team have other problems to deal with before they can focus on the blown diffuser, but Renault technical chief Alan Permane hinted that there is more to come from his team and explained: "We can probably expect to get more of an advantage from the updates at Silverstone, especially the blown floor because there are a lot more high-speed corners where you're on the throttle through the corners."

So perhaps Valencia was not the place to demonstrate the performance advantages of the blown floor to their greatest extent - and with both Ferrari and Renault happy they have a handle on their new developments, perhaps Red Bull should be looking over their shoulder with a little more concern ahead of the next race at Silverstone...

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