BMW Sauber F1.09 Debuts

The BMW Sauber F1.09 – fundamentally different.

The winds of change are blowing through Formula One. 2009 sees arguably the most significant rewrite of the F1 technical rulebook in the history of the sport. Whereas up to now the engineers had always been able to use the previous year’s car as a basis for the design of their new machine, now they’ve been asked to start with a clean slate – or, more accurately, a blank computer screen. Completely redefined aerodynamics, the return of treadless tyres (slicks) and the option of fitting KERS (Kinetic Energy Recovery System) technology have literally brought the teams back to the drawing board.

In early 2007 the FIA set up the OWG (Overtaking Working Group) to think up ways of making Formula One more attractive; in other words, to identify areas where change was needed to make overtaking easier.

The principle problem of modern Formula One cars lay in the massive amounts of downforce they lost once the distance to the car in front dropped below around two seconds. This “dirty air” whipped up by the preceding car significantly diminished the effect of the front wing in particular, and this manifested itself in pronounced understeer. As a result, changes in position were more frequently the result of strategies in the pit lane than overtaking manoeuvres out on the track.

The OWG looked into this phenomenon with the help of a series of experimental tests in the wind tunnel and computer-aided airflow simulations, before coming up with a proposal: less aerodynamic downforce combined
with more mechanical grip would be the way ahead. Indeed, the OWG recommended reducing downforce by some 40 percent.

This has led to radical changes, especially as far as aerodynamics are concerned. The front wing of the F1.09, for example, has grown in width from 1,400 mm to 1,800 mm, making it as broad as the car as a whole. It is also fixed lower down than before. Added to which, spectators will find the significantly narrower, higher-mounted rear wing takes some getting used to.
The regulations have also limited the use of air deflectors and cooling apertures to a minimum. The result of all these new rules is a totally new look for the F1 cars.

Even more exciting than ever.

For Willy Rampf, the BMW Sauber F1 Team Technical Coordinator and the man responsible for the concept of the BMW Sauber F1.09, and Walter Riedl, Managing Director of BMW Sauber AG – who also heads up the technical department in Hinwil and is responsible for the development of the new car – this project has represented a memorable challenge. “Developing a new Formula One car is always exciting, but this time there was something even more special about it. We really were starting from scratch,” says Rampf. The combination of the return of slicks with the possible use of KERS technology places particular importance on weight distribution. “First and foremost, the switch from grooved tyres to slicks means more grip, of course, but it also moves the balance of forces further forward: removing the grooves gives the front tyres proportionally a greater contact area and more grip than
the rear tyres,” explains Rampf. Consequently, more weight has to be shifted towards the front of the car and the aero balance adjusted likewise.

This is no easy task, especially in conjunction with KERS, as the new system adds extra weight and the engineers have much less scope for juggling ballast. Furthermore, they also have to find a way of packaging the KERS elements – the electric motor/generator, energy storage unit and control unit – which mini- mises their negative impact on aerodynamics and at the same time ensures there is sufficient cooling for all these components.

Work begins earlier than usual.

The team had to carefully consider all of these practical constraints in the basic concept of the car. Key areas included the definition of parameters such as the wheelbase, weight distribution, position of the engine and gearbox, shape and size of the fuel tank, and the positioning of the KERS elements. “Because
the car differs so significantly from its predecessor, we already started work on the first concept studies in February – two months earlier than normal and before the F1.08 had even started its first race,” says Rampf, highlighting the extraordinary nature of the situation.

“Our aim,” continues Rampf, “was to build a car with high aerodynamic efficiency and in so doing claw back as much of the downforce as possible, which the new regulations had taken away.” The first phase of the project involved conducting studies on several different concepts in which the team assessed the interplay of aero balance, tyre requirements and weight distribution. This was followed by an optimisation phase.

The aerodynamics experts invested a great deal of time in the development of the front wing in particular, as this area influences the airflow over the entire car. As far back as February, the BMW Sauber F1 Team specialists used CFD –
and therefore the capability of the Albert3 supercomputer – to look into the functioning of the front wing and, more specifically, its interaction with the underbody. “No longer being allowed to use turning vanes to guide the airflow makes the task a whole lot more difficult,” explains Walter Riedl. Another complicating factor is the centre section of the front wing, which is also precisely defined in the regulations and thus imposes further constraints on how much the engineers can do.

The result is a three-element front wing with a very dominant visual presence, which does much to shape the appearance of the car as a whole. Its outer edges are fitted with several auxiliary elements, which are all designed to channel the air as efficiently as possible around the front tyres. The less air hitting the turning wheels directly, the less uncontrolled turbulence occurs.
Another new feature of the regulations allows the drivers to move the flaps on the front wing upwards or downwards. Again, this is intended to make it easier to get up close behind the car in front.

They may have already made admirable progress, but this is just the beginning for the engineers, as Riedl explains. “The complexity inherent in the interaction of the front wing with the open front tyres means there is still a lot of potential for further development here. Indeed, we picked up a wealth of valuable knowledge in this area with the F1.08.”

The nose of the car also reveals striking changes and is now considerably higher and, above all, much wider than its predecessors. After a large number of tests, this variant proved to be the most efficient when working in combination with the new front wing.

Severe demands on cooling.

The new regulations have also presented the engineers with a challenge when it comes to the car’s cooling concept, as lamellar outlet vents in the engine cover are no longer permitted. For this reason, at the rear of the car the air now flows back centrally through the aperture between the engine cover and the gearbox. The channelling of the airflow takes on particular importance here, as the hot air heats up all the nearby components. Where you used to be able to vary the level of cooling through chimneys and lamellar outlet vents of different sizes, now you can only vary the size of the air outlets.

But that’s not all, since the KERS elements also need to be cooled. While the energy storage units fitted with impressive compactness in the two sidepods are kept within the required temperature band by the flow of air, the KERS control unit, which is fitted in the right-hand sidepod, has an integrated cooling system.

The sidepods are high at the front and do not fall away as sharply to the rear as in previous years. As chimneys or lamellar outlet vents may no longer be used as an escape route for the exhaust air, the whole rear area of the car, including the engine cover, has to increase in volume to enable optimum airflow over this section as well.

The rear wing is totally new in terms of both its form and its position. It now measures only 750 mm in width – instead of 1,000 mm, as on last year’s car – but is 950 mm in height, up from the previous 800 mm. This change in the regulations means that cars following behind will be subjected to less turbulence. A particularly striking feature are the side endplates, whose form has a major influence on the optimum functioning of the rear wing. The lower levels of downforce will have an effect on the car’s aerodynamic
set-up. “In 2009 we’ll be running maximum downforce at a lot more circuits than last season,” says Rampf.

Something the observer will not be able to spot at first glance are the changes to the diffusor also specified in the regulations. This element now rises over
a longer area than before and leads further back along the car. As a result there will no longer be direct interaction between the diffusor and the lower element of the rear wing, which will make the car less sensitive to different airflows.

Making optimum use of tyre potential.

The switch to slick tyres was a central factor in the development of the car’s suspension. The team collected initial data with the grooveless tyre, which generates far greater grip than its predecessor, over the course of the summer after Bridgestone delivered the first batch of slicks for testing. It quickly became clear that achieving the right weight distribution would play a critical role. At the front axle the priority was to extract the full potential from the tyre in the various situations. Plus, optimised kinematics and high rigidity should allow it to give the driver high-quality feedback.

Whereas the front axle for the new car shows only minor differences to the one fitted on the F1.08, the rear axle is an all-new design adapted to the changes in tyre characteristics. The aim was to achieve excellent traction, while at the same time exploiting the lateral force potential of the tyres through an extremely wide band. Added to which, the F1.09 should retain the impressive braking stability of its predecessor.

And, of course, the engineers also placed considerable importance on keeping the weight of the new car as low as possible. Numerous components were further optimised to this end. There were no compromises, however, when it came to rigidity.

“The development of the F1.09 centred on three key areas: aerodynamics, optimum tyre utilisation and the integration of KERS. That’s where our focus has been from the outset and where we have channelled the large reserves of knowledge amassed during the course of last season. The F1.09 contains the combined expertise of a highly motivated team – one which will be pulling
out all the stops to fulfil our ambitious aims once again in our fourth year on the F1 grid,” sums up Managing Director, Walter Riedl.

+ BMW Sauber F1.09 Full Release & Technical Data / Official PDF