July 2, 2007 BMW has for the first time combined its twin-turbocharged, six-cylinder diesel with the marque’s flagship Grand Tourer in the form of the new 635d. Coinciding with the revamp of 6 Series model line-up to include Active Headrests, Brake Energy Regeneration and other fuel saving and emissions-cutting technology, the 635d Coupé and Convertible will hit showrooms in the UK in October with world’s most powerful production diesel under the bonnet.
The BMW 635d Coupé records a zero to 62mph time of 6.3 seconds while the Convertible achieves this in 6.6 seconds. Both have top speeds electronically-limited to 155mph but still maintain impressive fuel efficiency levels - the Coupé still achieves 40.9mpg on the combined cycle and a CO2 emissions figure of 183g/km, while the Convertible retains near identical figures recording 39.2mpg and 190g/km.
The new 635d has also been given a subtle restyling to mark the technological changes including a revised headlight arrangement featuring LED technology and clear lenses, a new style of front valance and repositioned vertical struts on the front spoiler to accommodate a different shape of air intake for the car.
Powered by a twin-turbocharged 2,993cc engine with an all aluminium crankcase and third generation common rail fuel injection system, the 635d comes with an output of 286hp and 580Nm of torque. These performance figures have been made possible by the unique way the twin turbochargers work. A smaller turbocharger provides near instantaneous response for swift initial acceleration before a larger turbocharger comes in mid-range to provide additional thrust through to the redline. Peak torque is available from just 1,750rpm to deliver a seamless wave of smooth acceleration.
The performance is made possible by the introduction of “EfficientDynamics” technology that introduces Brake Energy Regeneration and the implementation of various needs-only operations of ancillary units for the first time in the 6 Series range. This includes the ability to decouple the air-conditioning compressor from the drive-train to prevent unnecessary drag on the engine and the use of lower viscosity fluids in key components to reduce friction. An optimum gearshift indicator is fitted to advise on economical motoring, while active flaps located behind the kidney grille can close off to improve aerodynamic flow and reduce drag. These measures mean lower fuel consumption and emissions figures than would previously have been possible.
Revised petrol powerplants
The BMW 635d is joined in the range by the 630i and 650i, offered in both Coupé and Convertible bodystyles. The six-cylinder magnesium and aluminium engine in the 272hp 630i now features new lean burn technology in the guise of high precision direct injection and double-VANOS variable valve technology. With its piezo crystal injectors for optimium fuel atomisation, the new style of induction makes for a near-complete fuel vapour burn and improves engine efficiency.
The new 630i Coupé records a 4.4mpg improvement (now 35.8mpg in combined fuel consumption) compared to the previous model and CO2 emissions also drop from 216g/km to 188g/km. BMW 630i Coupés fitted with automatic transmissions post even better performance figures with combined fuel consumption rising from 29.7mpg to 36.7mpg and emissions falling from 238g/km to 184g/km. The 630i Convertible achieves a combined fuel consumption figure of 34.0mpg compared to 29.4mpg, while CO2 emissions drops from 229g/km to 198g/km.
The top of the range 650i models are powered by a 4,799cc V8 engine providing an output of 367hp. The 650i with its aluminium engine and double-VANOS and VALVETRONIC variable valve technology is capable of a zero to 62mph time of 5.1 seconds in the Coupé and 5.5 seconds in the Convertible.
EfficientDynamics technology assists both 650i models in achieving improved economy and emissions figures. For the 650i Coupé consumption on the combined cycle improves by 2 per cent to 24.1mpg, while emissions drop by 2 per cent to 279g/km. The 650i Convertible also achieves better performance recording 22.4mpg, up 7 per cent. CO2 emissions are cut from 310g/km to 299g/km.
The 630i and 650i comes as standard with a six-speed manual gearbox, while the 635d is offered with a new six-speed sports automatic transmission. This gearbox features a new torque converter with enhanced software and a two-stage damper to reduce vibrations. The enhanced transmission specification means power-wasting slip in the converter is largely eliminated and with the improved software results in gearshift times that are smoother and 50 per cent quicker.
Along with revised exterior features such as the new headlight arrangement, the kidney grille is larger compared to the outgoing model and lower reflectors have been optically enhanced at the rear as part of a redesigned bumper and a third high level brake light now sits on the boot lid lip for improved safety. The introduction of new alloy wheel design in 17-, 18- and 19-inch sizes completes the exterior changes.
6 Series Convertible models also offer SunReflective Technology leather which has embedded pigments that reflect infra-red radiation in the sunlight and can reduce leather temperature by up to 20 degrees centigrade.
The revised 6 Series also features an infotainment system that includes eight ‘Favourite’ buttons. BMWs have featured popular programmable buttons on the steering wheel for a number of years and the 6 Series comes with a small bank of programmable buttons for added convenience on the centre console. These can be customised and used as shortcuts to the most frequently visited parts of the iDrive system such as navigation destinations or radio stations.
BMW is at the forefront of automotive safety technology and Active Headrests appear on the 6 Series for the first time. Standard fit on cars, the system has been introduced to prevent occupants from whiplash injuries in rear end accidents. When the airbags’ central control unit registers a rear end collision pyrotechnics fire to release two springs in the head rests. These then rapidly push the front of the restraint forward by 6cms and upwards by 4cms, reducing risk to the driver and front seat passenger of serious neck injury.