Technical review: British Grand Prix

Posted on | Author John Beamer

McLaren front wing

Looking back on the technical developments from Silverstone, here’s John Beamer.

Silverstone was always pegged as a Red Bull track and a 0.7s qualifying gap confirmed it as such.

To see the RB6’s superiority one need look no further than Abbey where it had an astonishing 10mph exit speed advantage. That is why the rest of the paddock is scurrying around introducing exhaust blown diffusers (EBD).

And, as explained here two weeks ago, McLaren proved implementing EBD successfully is at least as challenging as getting the F-duct to work.

The ‘new’ McLaren

McLaren's low-cut sidepods
McLaren's low-cut sidepods

McLaren’s EBD resulted in a radically revised car. Most noticeable were the new super-low sidepods that ultimately housed the new floor-based exhaust exits. With its original periscope exhausts the McLaren always had a rather bulbous rear end. Although the sidepods where heavily undercut to allow air to flow over the coke-bottle zone, the engine cooling was integrated into the exhaust openings, which impinged rear wing efficiency.

The new EBD has allow McLaren to lose these original cooling slots and carve louvres in their place. Although the rules forbid multiple bodywork slots McLaren has got round the regulations by bisecting a slit through the middle of all the openings so ensuring they are technically only one opening. This was a solution Ferrari pioneered at the opening race in Bahrain and shows how canny F1 teams push rule interpretation to the very limit.

As a result the rear of the car drops off quite precipitously allowing much cleaner airflow over the rear wing – this in itself will be worth a couple of tenths.

In addition to the engine cover revamp the exhausts exit just aft of the sidepod below the forward lower rear suspension wishbone. It’s unclear if McLaren has moved it suspension pick-ups to optimise the flow of exhaust gasses as Ferrari did. The lower wishbones have always been close to the floor but McLaren seems to have created enough space for the gasses to flow.

The bodywork appears to cover the exhaust exit to better direct the hot gasses under the wishbone. A close look at the wishbone shows the inboard part is covered with heat resistant material to protect it from the hot exhaust gasses.

To complement the lower exhausts McLaren installed a revised diffuser to improve the downforce. The diffuser was reinforced with heat proof materials and the fins in the outer channel were reduced in size. The McLaren EBD solution is similar to Ferrari’s in that the gasses blow over the top of the diffuser and effectively reduce the pressure gradient the diffuser has to work against – this secures more downforce.

No one has been able to adopt the Red Bull solution, which is to feed some of the exhaust gasses directly into the outer channel of the diffuser.

McLaren: what went wrong?

McLaren's low-cut sidepods
McLaren's low-cut sidepods

Before we answer the question its important to understand some of the handling characteristics of the MP4-25. The oversize diffuser means that the car is more sensitive than most to ride height changes. This presents particular problems over bumps where the change in ride height causes airflow under the car to detach. Going down a straight this isn’t a problem but can result in awkward handling through high-speed corners.

This ride height issue means that the car has to be sprung very stiffly. All F1 cars have limited suspension travel (about two-thirds of total suspension travel actually comes from the tyre side walls) but the MP4-25 takes it to a new level.

It just so happened that the new complex at Silverstone was exceptionally bumpy, particularly in the quick Abbey right hander (where the new and old tarmac join) and up to the Village loop. As a result the McLaren had numerous offs during Friday practice.

The EBD makes the car more sensitive to throttle use as drivers lift approaching a corner downforce causing the exhaust gasses over the diffuser to decay. This proved too much for the stiffly sprung McLaren to cope with and the car started porpoising through the Abbey section.

The decision to remove the EBD was marginal – Hamilton wanted to race it. The problem came down to set-up. Because of the pitch-sensitive nature of the car the MP4-25 is much harder to set-up than its predecessors. McLaren engineers claim the MP4-23, for instance, had a wide set-up sweet spot, which allowed it to the fast out of the box. Not so with the latest McLaren – failure to find a good set-up resulted in the Woking-based outfit removing the EBD.

Set-up wasn’t the only problem, however. McLaren’s difficulties with the EBD were similar to Mercedes’ in Valencia. The floor wasn’t insulated enough, which meant that it slightly warped under the intense heat of the exhausts, which also damaged performance.

It’s back to the workshop to get the new floor fixed for the German Grand Prix this weekend. McLaren remains confident that its EBD package, when working, will be worth over half a second, so it should be able to challenge the RB6 more consistently.

Other teams’ EBDs

Ferrari exhaust arrangement
Ferrari exhaust arrangement

Despite McLaren’s trouble there is little doubt that the EBD works. Sure teams won’t be able to extract Red Bull levels of downforce but that will always be the case when you’re retrofitting major upgrades. By all accounts Ferrari’s and Renault’s versions are both working well and judging by Nico Rosberg’s pace, Mercedes has its device working far better than at Valencia.

Williams also introduced the system for Silverstone, although unlike some of the leading teams the EBD has been part of its development cycle since October last year. Had it stayed with the Toyota power plant Williams would probably have run it at the start of the year but the move to Cosworth engines led to a postponement.

Since Valencia more information has emerged about how Red Bull manages to eke out a few extra tenths in qualifying. In effect there is a setting on the engine control unit that for a couple of laps retards the ignition. What this does is keep some throttle open but later in the engine cycle.

This draws in fuel that is then ignited as the exhaust valve is open. Obviously the exhaust exit and cylinder tops aren’t designed to handle repeated combustion so its not a setting that can be applied all race. This results in a more constant flow of exhaust gasses over the diffuser and hence greater downforce and is the primary reason why Red Bull have such hot qualifying pace (this is probably worth half a second a lap or so). The process is similar to that used in the old F1 turbos to keep the turbo jacked up.

Red Bull front wing

Red Bull's new front wing
Red Bull's new front wing

Thanks to Red Bull’s much-publicised brouhaha a lot of time and effort was spent dissecting the difference between the Milton Keynes-based outfit’s new and old front wing.

The changes are subtle and Red Bull publicly stated were worth about a tenth per lap. The most radical change is the front camera housing which has been moved to the central section of the wing as opposed to being outboard of the nose. This isn’t a new invention – Force India pioneered it a few races back.

During the design of the revamped 2009 regulations the Overtaking Working Group, commissioned by the FIA to look at how to reduce downforce to improve overtaking, mandated a standard central section to the front wing. This section actually produces a touch of lift to help cars follow each other more closely.

The re-housed cameras mean that this zone now generates some downforce. Two effects are going on here. First the housing is mounted as an aerofoil so generates suction. Second the gap between the underside of the wing and ground creates a mini-venturi, which further amplifies grip.

The two major changes to the Red Bull wing was the addition of a second inlet slot in the endplate and revised main profile. The endplate slot allows air outboard of the endplate to energise air working hard under the wing to produce downforce. This has the effect of increasing downforce (and drag – not that that is a problem at Silverstone). It shows how quickly Red Bull is pushing development given the team did not expect to have updates for this race.

Given the high-quality of the pictures we have this month (thanks Keith!) it is worth a closer look at Red Bull’s nose section.

The raised shoulders of the V-nose are doing two things. First they help prevent airflow spill off the top of the car, which may interfere with that below the car. And second it allows the designers to optimise the shape of the underside of the nose (and still keep within the minimum cross-section rules). If you look at the lower suspension pick-ups there is additional space, which allows more air to pass between the underside of the nose and the tyres (see picture).

McLaren front wing

McLaren front wing
McLaren front wing

McLaren introduced a unique front wing solution for Silverstone that featured a double endplate. Originally introduced to help better balance the front of the car after the addition of the EBD, it was eventually run with the old floor.

If you look carefully you’ll see what looks like a second endplate 20cm or so inboard of the outer endplate. This is to try to separate the air going around, to, and inside of the tyre.

This allows the zone between the two endplates to be worked harder and tuned specifically to interact with and reduce tyre drag while protecting airflow over the rest of the wing, allowing more consistent downforce, particularly as air leaves the wing and feeds the sidepods, bargeboards and floor.

Notice the three curve sections towards the front-bottom of the main plane. These help generate vortices which act to extend the endplate so sealing each section – in effect acting like skirts.

Ferrari and Renault front wings

Ferrari front wing
Ferrari front wing

After its new EBD and floor in Valencia, Ferrari finally introduced an updated front wing. Scuderia-watchers have been complaining for some time that the team’s development, particularly of the front wing, had fallen behind Red Bull and Renault, which was part of the reason for the inconsistent showing.

For Silverstone Ferrari introduced a new, three-piece front wing. Although not as radical as some hoped, it does show that Ferrari is being thoughtful about this area. Expect more refinements in the next few races as this is one area where the F10 lags its competitors.

In complete contrast to Ferrari, Renault’s front wing evolution has been nothing short of astonishing. It came to Silverstone with yet another wing with an impressively complex endplate arrangement.

Renault front wing iterations
Renault front wing iterations

The upper cascade has been discarded in place of two horizontal splitters, one in place of the outermost part of the cascade and one aft at the back of the endplate just in front of the tyre.

The reason for this supreme complexity is to manage airflow around the tyres and try to control wheel drag. Studies show that the right combination of wheel and front wing design can have a massive effect of net drag.

Williams front wing
Williams front wing

Counter-intuitively adding lift in front of the tyre can sometimes result increase in aero efficiency (although that doesn’t appear to be happening here). Unfortunately for Renault this front wing appeared not to work and the team elected to revert to its old wing.

It’s worth comparing the Renault and McLaren front wings to Williams’ (see picture). You can quickly see how developed the Renault endplate is in particular.

Virgin and Lotus

Virgin's new aero package
Virgin's new aero package

Virgin suffered problems at the start of the season what with unreliable hydraulics and an embarrassing mistake with its fuel tank. Since then the team always planned to introduce a substantial upgrade at Silverstone and it did.

The team introduced a B-spec car almost with new front and rear wings, new brake ducts, a revised diffuser and lots of new detailed around the side of the car e.g., bargeboards and pod vanes.

The car is starting to lose its boxy, amateurish feel and performance (relatively) improved. The team was only four-tenths behind the fastest Lotus in qualifying, which ignoring the first race of the season, Malaysia (which was wet) and Monaco (which is a short track where performance bunches) was by far the closest Virgin has ever got to Lotus on a Saturday.

Lotus isn’t standing still and bought what it claims is its last major upgrade of the season to the British Grand Prix before it turns its attention to the 2011 car. The biggest change was the introduction of a new floor to try to improve underbody downforce.

Many of the other changes were to help reduce the weight from some of the parts to allow better weight distribution through ballast. What Lotus has done under Mike Gascoyne is impressive. The team was the last to get its 2010 race license and has clearly established itself as the best new team. With the backing of Tony Fernandes and the ingenuity of Mike Gascoyne expect Lotus to swiftly close the gap to the midfield next year.

On to Germany

The Hockenheimring is more point-and-squirt than Silverstone and doesn’t make the same extreme downforce demands. The tighter corners demand good traction out of the corner, but there are a couple of high-speed straights where an F-duct will come in use for those that have one.

The technical story of the weekend will be whether McLaren can get its EBD to work. The odds are they will – Friday running at Silverstone should have given the Woking-based outfit some good data. The nature of the circuit should also mean that Red Bull’s advantage will not be as great as it was at Silverstone.

One other thing to watch is the battle between Red Bull and Ferrari. This will be the third race that the Scuderia has run its EBD – it should now understand the intricacies of the system and we should see refinements to the diffuser in particular as the team ekes out further performance. A good job too – for if Ferrari is to win the championship it needs a sterling result at Hockenheim.

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