Tech Analysis: BMW F1.08

Entering their third season as BMW Sauber, the team have evolved massively from their origins. While Sauber were a respectable team creating innovative cars with relatively small budgets, it taken the huge resources of BMW motorsport to evolve the team to where it stands today.

The 2007 season was the team's strongest to date. It was without argument the third best team on the grid, and captured second in the constructors' championship after McLaren's penalty.

Last year, BMW Sauber were clear of the midfield, but lacked pace compared to the leading two teams. That said, occasionally they were able to break into the top four positions in either qualifying or the race, through both reliability and pace.

It's been this step up that has enabled BMW Sauber to make the big move forward that they appear to have done this year. The change was driven by the fact that the F1.07 was good, but lacked a little in all areas to match Ferrari or McLaren on pace. Thus, the team needed a major update to gain the speed, rather than simply rectify a single area.

Taking this step was helped by the team being sufficiently clear of the opposition to halt development on the F1.07 as early as September, to focus on the new F1.08.

This freed the team up to make far-reaching changes to the car - perhaps a unique position, as almost every other team was either fighting for championship position or looking into fundamental problems in the 2007 car.

It will be important that BMW Sauber make the most of this opportunity, as it might not present itself again.

By working the long square jawed middle section harder the front wing is less sensitive © Scarborough (Click to enlarge)

Development

As the third car in the teams current guise the F1.08 is a "radical evolution", according technical director Willi Rampf. This is quite an achievement, as the F1.07 was also a distinct step from the F1.06, itself an evolution from the previous Sauber car.

The F1.07 was the first car fully designed by the new team, with the power train (engine and gearbox) being provided by BMW Motorsport in Munich. While the gearbox did have its reliability problems, it must be remembered that this was the first F1 transmission from the team, and a seamless shift unit at that.

So in many respects the F1.08 is the second generation car from the team. Without any specific vices to iron out from last year, the team were able to aim at the usual improvements: more grip, less weight, more aero efficiency and better reliability.

Along with the new rules, there was the introduction of the SECU (the standard ECU), which impacted on the in-house electronics development of the BMW Race Car Controller (ECU). Additionally, there was the four-race gearbox rule, which demanded a new gear cluster and casing to be developed.

But Rampf's key targets were improvement in aerodynamic sensitivity; also a key aim for the F1.07. With the team's wind tunnel and their supercomputer for CFD, BMW have perhaps reached or even exceeded the leading teams' ability to analyse aerodynamic behaviour.

However, this is tempered with an approach that isn't looking for ultimate downforce in an idealised environment, but reflecting the attitudes and conditions that the car sees on track. So, Rampf is looking at how the car works when it steers, rolls, pitches and yaws ... even side winds are analysed. Heading the aero department is ex-Honda man Willem Toet.

The work the team did on sensitivity paid off last year, as the car performed well at all tracks. This lack of sensitivity will be even more important this year, as the cars will be less stable due to the lack of electronic controls. This will have a knock-on effect, as the rear suspension may have more travel to improve traction.

Seen in early testing, the pod wing gains a vane to connect it to the bargeboards © XPB/LAT (Click to enlarge)

Aside from the aerodynamic side, the new car aims for better mechanical grip, using a development of last year's front suspension and a new rear set-up. Mechanical grip will be aided by a longer wheelbase by some 20mm (not a particularly large increase to 3130mm) and more flexibility in where the ballast can be placed to alter weight distribution.

The F1.08 in detail

From first appearances the F1.08 is a very detailed car, just as last year's McLaren featured heavy thinking in every detail of the aerodynamic surfaces.

Starting at the front, the new BMW sports an all-new wing, borrowing thinking from McLaren's much-copied three-element wing. But BMW have a more aggressive wing, with the same square-shaped centre section which features a jutting chin to make the more efficient central section more powerful.

By making the middle section work so hard, perhaps BMW have found the outer wing area can be less powerful to reduce its sensitivity to the movement of the front wheels.

Sporting three elements which take all the available area allowed within the rules, the wing's balance is much further forward and hence it is hung from its middle element.

One curiosity on the wing's slot gap supports is the forward support tying the main plane and first flap together. This is a metal part, incorporating the pitot tube - a device that measures airspeed and is more often mounted top the monocoque. Above the wing, the nose cone is much slimmer and longer than on the F1.07.

Feeding back from the front wing, the bargeboards are revised, the main board being much larger and featuring Ferrari-like serration along its top edge.

Once the car started testing, the tail ends of the bargeboard boards were joined to the pod wings by an extra turning vane. This is a progression of the vane added between the boards flip-ups last year, and enables the pod wing to be much smaller.

The job of gathering up the flow and sending it around the sidepods is achieved by the vertical vane, and not large sensitive pod wings.

Innovation extends to the front wheel fairings with a square lower leading edge © XPB/LAT (Click to enlarge)

A particular feature of the car are the front wheel fairings, or 'rim shields' in BMW Sauber-speak. These static fairings are an evolution of the devices run by several teams last year.

In BMW's case, the fairing starts with a straight vertical leading edge. The square-shaped lower portion extends beyond the rim, although this still fits in within the brake duct rules, which define how far forward a duct can reach.

By having an extension in this area, the flow spilling off from the front of the tyres is picked up and fed back along the car in a tidier fashion.

Also, the duct departs common practice by having an exit formed by a bulge in the rear of the fairing. Again, a slightly better method than the arcs removed from the fairings of other teams. Thus, BMWs wheel fairings could be more efficient in sending a tidier flow along the flanks of the car.

Again the sidepods are further slimmed, starting from the undercut and leading back to the gearbox area. By routing their exhausts high and venting them over the bulge concealing the rear dampers, the coke bottle area can be much neater.

Above the sidepods is another innovation from BMW Sauber, the 'heck' wing. The T-wings placed behind the chimneys are extended to reach on-board and connect to the engine cover. This negates the shelf wing fitted between the rear flips and the tail of the engine cover.

According to BMW Sauber, the Heck wing creates its own downforce, as well as improves flow the rear wing. It's forward placement might be a less sensitive area to bend the flow towards the rear wing.

BMW Sauber's unique 'Heck' wing (yellow) is sure to be copied by other teams © Scarborough (Click to enlarge)

At the rear, the car's diffuser adopts the high expansion format of the Ferrari, McLaren and Williams. The normal central and side channels are supplemented by smaller channels piggy-backing the side channels. This makes use of the small area missed out by the bodywork rules between the rear wheels.

A greater diffuser exit area allows for more downforce to be potentially created, but this demands that the floor and area around the diffuser is working well to prevent separation. No doubt the new bargeboards and intricate rear brake ducts assist the flow remaining attached through the diffuser.

As has been mentioned, the mechanical set-up of the car has been developed for more grip, with the front suspension only being revised and new front hubs designed to allow the static wheel fairings to be fitted.

At the back, more grip is created by revised but outwardly unchanged rear suspension. In order to meet the reliability and dimensional rules of the gearbox, the entire unit has been revised by Markus Duesman's drive train department in Munich. This team have also developed the engine and gearbox to work on the SECU.

This work started as far back as July 2007, and has entailed the repackaging of the entire electrical system, which includes a revised steering wheel; complete with the standard LED displays, and a new feature for 2008, a throttle pedal sensitivity control. This helps the drivers' control wheels pin by altering the way the throttle pedal reacts to driver inputs.