BMW lifts the lid on the new BMW 6 Series Convertible that will debut at the NAIAS, Detroit in January. Priced at £55,355 on-the-road (manual) and £56,705 (automatic), the BMW 645Ci Convertible goes on sale in the UK from March 2004 alongside the acclaimed Coupé variant.

With its award-winning V8 engine, chassis and body panels using lightweight materials, an almost perfect 50:50 weight distribution and a stylish roof design, the new BMW 6 Series Convertible offers an intoxicating mix of sports car performance, grand tourer practicality and drop-top motoring.
Raising the roof
Available in either grey or black, the vinyl roof is raised and lowered at the touch of a button on the dashboard or via key fob activated remote control. In around 20 seconds - and at speeds of up to 20 mph - six hydraulic cylinders guide the compact roof into its housing, without significantly compromising luggage compartment space.

Rather than designing a Coupé then removing the roof, BMW designed the Convertible alongside the Coupé, resulting in the drop-top retaining a near 50:50 weight distribution. The roof’s relatively low weight also contributes to the car’s solid driving feel.

With the roof down, drivers will appreciate a throaty exhaust note that reflects the power of the V8 VALVETRONIC engine. However, when up, exterior noise is kept to a minimum thanks to noise insulating polyurethane foam between the rubberised outer layer and inner roof lining. The foam is also heat insulated.

Coupé contours are reflected in striking C-pillar style ‘fins’. A retractable glass rear window is housed between the fins, offering draught free ventilation, excellent visibility and impressive levels of noise insulation. This window is not attached to the roof and can be raised and lowered into the space between the luggage compartment and rear bulkhead whether the roof is up or down.

Another key factor for open-top motoring is that the designers have ensured minimal wind ingress into the cockpit through careful attention to the car’s aerodynamics. At speeds of well over 100 mph, driver and front passenger will experience very little turbulence.

With the roof up, the boot offers a capacious 350 litres of space and 300 when down which is ample for a medium sized suitcase and up to two 46 kg golf bags.

6 packed with power

BMW 6 Series Coupé and Convertible models are powered by the 2002 International Engine of the Year. Under the bonnet, this V8 powerplant pushes the BMW 6 Series Convertible to 62 mph in just 6.1 seconds (6.2 seconds for the auto). Top speed, available in fifth and sixth gears, is electronically limited to 155 mph.

Power and torque figures are predictably impressive. As with the Coupé, the BMW 6 Series Convertible achieves its maximum power of 333 bhp at 6,100 rpm with maximum torque of 450 Nm (332 lb-ft) available at 3,700 rpm. BMW’s VALVETRONIC valve control and Bi-VANOS infinitely variable valve timing ensure that power is used as efficiently as possible.

Three six-speed gearboxes are available, including a standard manual and optional six-speed automatic with Steptronic. Completing the trio is BMW’s optional SMG Sequential Manual Gearbox, with leather sports steering wheel-mounted ‘up’ and ‘down’ shift buttons offering drivers more than a hint of Formula One gear changes. Driving Dynamics Control (DDC) is standard with all gearbox options and is operated by a Sport button on the centre console. DDC offers a more sporty drive, by sharpening throttle reaction for more responsive acceleration, as well as giving a more direct feel from the power assisted steering. Where an automatic or SMG gearbox is fitted, DDC also up-shifts at a higher rev range.

Lightweight design

While extremely stiff, the 645Ci Convertible weighs just 1,815 kg, using a combination of aluminium, steel and synthetic materials. This intelligent use of lightweight materials includes aluminium bonnet and doors, thermoplastic front wings and boot made of Sheet Moulding Compound (SMC).

The UK will see approximately 1,000 BMW 6 Series Convertible models a year from 2005 (around 6-700 in 2004), and along with the BMW 6 Series Coupé, the car features a host of state-of-the-art and driver-oriented technologies including Dynamic Drive, Active Steering and Dynamic Traction Control.

Dynamic Drive

Dynamic Drive is BMW’s revolutionary system of active anti-roll bars that significantly reduces body sway in bends. Optional Dynamic Drive uses step motors which build up counter forces on two anti roll bars, preventing occupants being rocked from side to side, absorbing up to 80 per cent of roll at lateral forces up to 0.6g. The result is a more comfortable ride even when the car is being put through its paces on twisting mountain roads.

Active Steering and DSC

Active Steering and Dynamic Stability Control (DSC) are two driver assistance systems that work together to enhance safety and stability of the new BMW 6 Series, without compromising driver involvement.

Debuting on the BMW 5 Series but tuned for the new BMW 6 Series, Active Steering features a set of planetary gears powered by an electric motor. At low speeds Active Steering amplifies driver inputs at the steering wheel, making it easier to manoeuvre in town driving or when negotiating tight turns. Steering becomes progressively more indirect and firm as speed increases, enhancing stability and comfort ensuring smooth and precise handling at all speeds.

However Active Steering also helps prevent oversteer in corners by taking information from DSC yaw sensors and creating subtle steering corrections. The full range of DSC sensors – measuring steering wheel angle, individual wheel speed, and yaw rate – supply the data that allows DSC to reduce engine power and brakes individual wheels if absolutely necessary. However in hard cornering, where oversteer threatens, the intervention of Active Steering means DSC operates less frequently. The result is improved safety but a more involving drive for purists.

For a sporty extension of DSC, drivers can also select Dynamic Traction Control (DTC) by pressing the DSC button. This raises the limit at which engine torque is reduced and moves braking to a looser ‘slip threshold’. As well as aiding performance, DTC improves traction on gravel, ice and snow. DSC can be fully disengaged by pressing the button for over three seconds.

Even more technology

Describing the new BMW 6 Series line-up as a technological tour de force is no exaggeration, with groundbreaking optional systems like Head-up Display (HUD), Adaptive Headlamps and voice activated iDrive. It also includes recently EU homologated Brake Force Display with LED lamps at the rear.

Brake Force Display warns drivers following the BMW 6 Series of any heavy braking, with a brake lamp cluster that includes two sets of LEDs. Under normal braking one set illuminates, however in emergency braking or where ABS activates, a second set lights up. Drivers following the BMW 6 Series are immediately aware of emergency braking and are able to take evasive action, cutting down on rear end shunts. Brake Force Display is also standard on BMW 3 Series and BMW 5 Series models.

Service Inclusive

Lowering ownership costs, BMW is offering its popular Service Inclusive package featured on BMW 5 Series and BMW 7 Series models. This Europe-wide service and maintenance package gives drivers five years or 60,000 miles of maintenance-free ownership for a fixed fee of £750. It is also fully transferable if the car is sold within that period.

Text & Photos: BMW GB