The fastest, most radical Bentley - EXP Speed 8

Team Bentley's EXP Speed 8, the fastest, most radical Bentley in history

Crewe, 14 March, 2001.... Bentley Motors announced today that the racing team that will return the marque to Le Mans for the first time in 71 years will be known as `Team Bentley'.

The decision to return to Le Mans with one of the most advanced designs ever to take up the challenge of the classic French race is symptomatic of the mood of innovation and adventure, indeed a new dynamic that is shaping the Bentley Motors of the 21st century.

Not only will the two EXP Speed 8s be the only fully enclosed prototypes at the start of the 24 hours in June, they will also have been constructed in a way that is unique even among 21st century sports racers, reflecting the pioneering spirit of company founder W.O. Bentley.

At the heart of the concept lie three hoops of carbon-fibre. The largest of the trio surrounds the car behind the driver, the smallest goes around the pedal box, while the third central hoop encircles the car's structure roughly around the driver's knees. This, then, forms the platform onto which the fully stressed carbon-fibre body is attached to create a monocoque that is both exceptionally strong, stiff and light.

The strength is needed to protect the driver in the event of an accident, the stiffness to provide the rigid base without which the optimum handling is impossible and the lightness to counteract the extra weight that items such as a roof, doors and windscreen force on a closed racing car. The result is a monocoque which weighs just 70kg or 154lb.

The second benefit of this innovative design is it doubles as an immensely strong roll structure and negates entirely the need for a conventional steel roll cage within the car. Not only does this save a great deal of weight, it also means the size of the cockpit can be reduced, enhancing aerodynamic efficiency without compromising driver comfort.

While the actual speed of the EXP Speed 8 must remain under wraps until May, it is breaking no secrets to observe that, under the rules governing closed prototypes racing at Le Mans, its twin-turbo 3.6-litre V8 is allowed to use an air restrictor 1mm larger than those on cars in the open class. And while this might sound like a negligible amount, the effect is anything but, providing a significant increase in the output of an already very powerful engine.

Actual potential lap times around the 8.4mile circuit will not be known until the pre-race test weekend (5-6 May) but it is safe to say the EXP Speed 8 will reach speeds considerably in excess of 200mph four times every lap. Indeed the only factors preventing the EXP Speed 8 from going faster still is the geography of the circuit and the effects of downforce at high speed which uses air pressure to push the car ever harder onto the track as speed increases and inevitably compromising its top speed.

The aim in optimising a racing car's shape is to produce the maximum downforce possible with the minimum amount of drag and, to achieve this aim, the EXP Speed 8 has been wind tunnel tested extensively for over a year. It has been tried in well over 1000 configurations to make sure that, when it comes to racing, it has the best shape possible within the rules and the confines of the latest technology.

In addition to testing in the wind tunnel, the EXP Speed 8 is currently undergoing exhaustive `real world' testing on European race tracks to make sure what is shown in the tunnel is proven on the track. Team Bentley plans to complete at least one full 24 hour test run before the actual race.

Naturally all areas of the car's performance envelope are being tested but particular attention is being paid to fine tuning the Dunlop tyres to the

EXP Speed 8 and, in particular, the incredible amount of downforce it develops at speed. It will never reach its maximum potential velocity at Le Mans but even at top speed on the Mulsanne straight it will develop downforce equivalent at least to having a Bentley Arnage bolted to the roof. As an even more graphic description of the aerodynamic efficiency of the design, the amount of downforce generated at just 150mph is sufficient theoretically to drive the EXP Speed 8 upside down.

For Dunlop the challenge is tougher than for any other car in the race. Not only do its tyres have to withstand such forces and do so potentially for hours on end, they also have to do so within the 14in width specified by the rules for the closed prototype class. All other prototypes entered are open and can therefore use 16in rims.

And while other aspects of EXP Speed 8's performance remain closely guarded secrets, it can be revealed that the car is capable of developing in excess of 3G cornering power (only the most specialist, high performance road cars can approach 1G) and a similar level of G under braking.

The EXP Speed 8 is also extremely light. Despite the extra weight of the windscreen, roof and doors that its closed configuration demands, it will still have to carry ballast to make sure it tips the scales at the 900kg required for Le Mans prototypes. Then consider the fact that its engine develops at least 600bhp and in excess of 650Nm (Newton metres) of torque and it can be seen that the estimated 0-100mph figure of 6sec is, if anything, conservative.

Put another way, a typical 1500kg road saloon would require an engine developing in excess of 1000bhp even to approach the power to weight ratio of the EXP Speed 8.

-TB-