6/4/11

Overview: BMW 6-series

Third generation of models to carry the 6-series badge is available as a coupé or convertible. Compared with its predecessor, the six has grown by 75mm in the wheelbase — to 2855mm — and by virtually the same amount (74mm) in overall length, making the new car 4894mm long. An unspecified proportion of this stretch has gone into making the rear seats more accommodating. Additionally, the newcomer is 39mm wider and 5mm lower.

So much for girth.

When the new six goes on sale, two power-units will be available; both are petrol engines, and both use twin turbochargers.

The 640i has a three-litre straight-six. It is directly fuelled and uses BMW’s Valvetronic system, which controls not only the valve timing but also the lift. This unit offers 320PS and 450Nm; creditably, the maximum torque is available between 1300rpm and 4500rpm. The engine is homologated to EU5 emissions standards. Fuel consumption over the NEDC is 7.7l/100km or 36.7mpg; the CO2 yield is 179g/km. BMW claims that the 0-100km/h sprint can be achieved in 5.4s, while the maximum speed is limited electronically to 155mph.

That’s the cheap version.

If you can run to it, there is also the 650i. This uses a 4.4-litre V8, directly fuelled like the straight-six but lacking the Valvetronic system. The turbochargers are installed between the cylinder banks. Headline outputs are 407PS at 5500rpm and 600Nm delivered between 1750rpm and 4500rpm. Acceleration from a standing start to 100km/h is completed in a claimed 4.9s, with maximum speed once again limited to 155mph. Fuel consumption over the NEDC is 10.4l/100km — 27.2mpg — with a CO2 yield of 243g/km.

Both engines come with ZF’s 8HP eight-speed automatic gearbox and BMW’s Efficient Dynamics technologies: in the case of the 640i, these include stop-start, an ‘Eco Pro’ driving mode and active air intakes. Unfortunately, BMW — like Mercedes-Benz — sets up its stop-start system to work only with the foot-brake: if you apply the parking-brake when you come to a stop at a red light, the engine will not shut down. The power-unit restarts when the brake pedal is released or — if the driver is using the auto-hold function — when the accelerator pedal is pressed.

As you would expect, he transmission can be controlled manually using steering-wheel paddles. Brake energy regeneration is standard, while ancillaries operate on demand.

The chassis is new. Power assistance for the steering is electric, with Integral Active Steering an optional extra — more about that anon. Drive Dynamic Control is fitted as standard, offering the driver a choice of driving modes, while dynamic damper control and Adaptive Drive are optional; these provide a degree of roll stabilisation.

Adaptive LED low and high beam headlights are standard, and include a cornering function.

Eco Pro

This is a driving mode available on the 640i, selected using the Drive Dynamic Control button. Eco Pro mode re-maps the engine and transmission management, changing the accelerator response and the shift characteristics of the transmission, keeping engine speeds low under normal conditions. Readouts in the instrument cluster and central control display keep the driver informed about the levels of energy efficiency currently being achieved, as well as keeping a record for the journey up to that point and encouraging a driving style that minimises fuel consumption. For example, the increase in range achieved by using Eco Pro mode is displayed. As ever, we have to say that we have grave doubts about whether this sort of information display represents anything other than a distraction for the driver.

Driver assistance systems

The new Six has a full complement of driver assistance systems: rear-view camera, surround view, parking assistant, night vision with pedestrian recognition, speed limit information, lane departure warning and lane change warning. A head-up-display, which is an optional extra, works with the driver assistance systems to project relevant information in colour onto the windscreen: speed limits, junction graphics from the sat. nav., messages from the lane departure warning system, pedestrians detected and so on, as well as vehicle status information.

Systems and services can be specified to link the driver and car with the outside world. The Apple iPhone and other smartphones as well as MP3 players can be integrated into the car’s ‘infotainment’ system. BMW’s Connected Drive provides internet access and allows e-mail messages received on a smartphone to be shown on the Control Display — not something of which we’re wholeheartedly in favour. Internet-based services can be used for navigation and entertainment. Other functions include the location-based telephone information service from BMW Assist and the Advanced Emergency Call function with automatic vehicle location and accident severity detection.

The adaptive LED headlights produce a light spectrum that is a lot closer to natural daylight than that created by halogen or xenon units, producing greater contrast. The light pattern is tailored to the car’s speed, steering angle and yaw rate, allowing the pivot of the headlights to adapt automatically to the line of the corner. Meanwhile, a light source positioned specially in the headlight housing generates the cornering light which, at low speeds, ensures illumination of the road surface in the direction the car is turning.

The car’s basic instruments use black-panel technology, presenting clear, circular instruments. A high-resolution 23cm display below the four dials carries the mileage counter, fuel consumption reardout and Efficient Dynamics display, as well as feedback from the driver assistance systems and check/control messages. This black-panel technology, which made its debut in the BMW 7 Series, is also used for the climate control displays in the centre section of the instrument panel. The iDrive operating system, which is standard, uses as 18cm flat screen, though a 26cm unit is fitted if the buyer specifies the optional ‘Professional’ navigation system.

The front seats are lightweight items with integrated seatbelts. There are three versions. The standard driver and front passenger seats have electric adjustment for the seat height and fore/aft position, backrest angle and head restraint height — including memory function — as well as seat heating and an easy-entry function to improve access to the rather snug rear compartment. The optional sports seats offer more lateral support, and come fitted with integrated head restraints as well as manually adjustable thigh support. ‘Comfort’ seats are another option, adding what BMW describes as ‘comfort head restraints’, lumbar support, and electric adjustment of the thigh support, backrest width and angle of the upper backrest segment.

For the sports seats and comfort seats, there is the added option of active seat ventilation. Also, comfort seats can also be specified with the active seat function. All the seat types come with crash-activated head restraints, which move forward to counter whiplash.

In some markets, the new 6-series is equipped with an active bonnet system; in the event of a collision with a pedestrian, a pyrotechnic actuator mechanism automatically raises the front and rear of the bonnet. The purpose of this is that the pedestrian’s head will deflect the bonnet panel and, normally, could come into violent contact with something very hard and solid underneath. If the bonnet panel is raised, it will absorb the impact relatively gently and there will be little chance of injury from any of the equipment beneath.

So far as the bodyshell of the new Six is concerned, the static torsional rigidity of the Coupé derivative is around 53 per cent. greater than that of its predecessor, though no actual figure is available. In the interest of weight-saving, the doors, bonnet and front spring mounts are all aluminium, while the front side panels are made from plastic; the boot lid is fabricated from glass fibre composite.

Both the double wishbone front suspension and the multi-link arrangement at the rear are made predominantly from aluminium.

Unusually for a sporting car, low rolling-resistance tyres are fitted as standard. We have noted recently that this type of tyre seems to be improving — albeit from an unpromising start — so this vote of confidence from BMW is significant. Of course, as ‘low’ is not actually quantified, the title could mean relatively little.

Available as options for both models are Dynamic Damper Control and the Adaptive Drive system, which also includes Dynamic Drive active roll stabilisation. The electronically-controlled dampers adapt to the road surface and the driver’s style; both compression and rebound settings are adjusted continuously and independently from one another and from wheel to wheel. The roll stabilisation feature reduces effects such as body roll in high-speed corners and under sudden changes in direction: the system doesn’t prevent the car from leaning over, but by setting a very high damping rate it slows the rate at which the roll angle increases.

We mentioned previously that the Six is available with Integral Active Steering. This is an adjunct to the electric power steering system. Integral Active Steering combines the Active Steering system for the front axle — already available for the previous 6-series — with a steering rear axle, allowing the steering angle and power assistance to be controlled at both the front and the rear using electric motors.

At speeds of up to 60km/h (37mph), the rear wheels are turned in the opposite direction to the steering angle of the front wheels. This has the effect of reducing the car’s turning circle and the amount of steering effort required to manoeuvre. At higher speeds, the rear wheels follow the same steering movements as the front wheels: this arrangement is at its best when changing lanes at speed on the motorway. In cross-country driving, although handling is not adversely affected, slightly more steering input is needed to change the car’s direction.

BMW’s Drive Dynamic Control, like other similar systems, gives the driver the opportunity to choose between pre-set ‘maps’ covering such matters as accelerator response and damping rates. Three modes are offered: Normal, Sport and Sport+. In the 640i, Eco Pro mode can also be activated. If the Dynamic Damper Control or Adaptive Drive option has been specified, an additional setting — Comfort — can also be selected. In this mode, as well as adjusting the accelerator pedal progression, engine responses, power steering characteristics, DSC response thresholds and the shift dynamics of the automatic gearbox, Drive Dynamic Control also tweaks the damper responses and, if necessary, the roll stabilisation settings. On cars also fitted with Integral Active Steering, the basic steering set-up is also adjusted according to the mode selected, as well as the level of power assistance.

Lightweight, floating-calliper brakes with internally-ventilated discs are specified. They operate in combination with Dynamic Stability Control (DSC). This driving stability system brings together technology such as the anti-lock braking system, Dynamic Traction Control (DTC), Cornering Brake Control (CBC), Dynamic Brake Control (DBC), the Start-Off Assistant, the automatic Brake Drying function and brake fade compensation.

Full details of the new 6-series convertible models are given below; figures for the coupé will be added when they are available.

BMW 640i
convertible
650i
convertible
Cylinders 6I 8V
Block/head Al/Al Al/Al
Valves 4 4
VVT IE
Aspiration/
geometry
2T 2T
Fuelling D D
Min fuel grade RON 91 RON 91
Bore/stroke 84.0/89.6 89.0/88.3
Swept volume 2979cc 4395cc
Compression
ratio
10.2:1 10.0:1
PS/rpm 320/5800 507/5500
Nm/rpm 450/1300 600/1750
Maximum speed 155 155
0-100km/h 5.7 (5.4*) 5.0 (4.9*)
Urban MPG
(l/100km)
25.9
(10.9)
18.2
(15.5)
Combined MPG
(l/100km)
35.7/36.7*
(7.9/7.7*)
26.4/27.2*
(10.7/10.4*)
CO2 g/km 185 (179*) 249 (243*)
Emissions EU5 EU5
Transmission
— I
— II
— III
— IV
— V
— VI
— VII
— VIII
— Final drive
A8
4.714
3.143
2.106
1.667
1.285
1.000
0.839
0.667
3.232
A8
4.714
3.143
2.106
1.667
1.285
1.000
0.839
0.667
3.077
Driven wheels Rear Rear
Fuel tank 70l 70l
Kerb mass † 1840 1940
PS/t 174 261
Nm/t 244 309
Length 4894 4894
Width 1894 1894
Height 1365 1365
Wheelbase 2855 2855
WB/L 0.58 0.58
CdxA 0.31x2.23 0.32x2.23
Track
— front
— rear

1600
1657

1600
1657
Tyres 225/55R17 97Y 245/45R18 96Y
* Coupé.
† DIN kerb mass. For E.U. kerb mass, add 75kg.
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