First look: BMW Z4 goes coupe-convertible

BMW today revealed the first official photos and details of its second-generation Z4 roadster, which will debut globally at next month’s Detroit motor show and is scheduled to go on sale in Australia in the third quarter of 2009.

The big news for the new Z4 is that it has an aluminium folding roof and will therefore come in a single body style, whereas the current Z4 is produced as both a hard-top coupe and soft-top convertible.

It will also now be built at Regensburg in Germany rather than at BMW’s plant in the United States, which now produces only the X5 and X6 SUVs.

Although clearly a development of the first Z4, which in turn replaced the Z3 in 2002, the latest model’s styling does away with some of the more polarising elements and presents a well-balanced blend of curves and edges.

The new styling is highlighted by a larger kidney grille and upswept (rather than sad-eyed) headlights at the front, an Aston Martin-style bonnet, black A-pillars, smoother side panels and a Z8-style tail treatment.

It is also a step up in size over the current Z4, being 148mm longer at 4239mm and 9mm wider at 1790mm, but it rides on an almost identical wheelbase (up 1mm to 2496mm) and is 8mm lower overall at 1291mm.

BMW claims superior interior room for the occupants – with 5mm more headroom, 20mm more shoulder width and 43mm more elbow freedom – while getting in and out should be easier due to 26mm longer doors.

Going to a metal hard-top has also produced improved visibility thanks to 40 per cent bigger side windows and a 52 per cent bigger rear window.

Less welcome is an increase in weight due to the metal roof, faster-opening (just 20 seconds) roof mechanism and increased size. BMW has not released figures, but we believe that weights are between 90kg and 150kg more the equivalent current models.

Another unfortunate introduction is a new naming regime that was introduced with BMW’s SUV line-up – which now features models such as X5 xDrive30si – and is now clearly destined for the passenger car range as well, despite the fact that the rest of the automotive world has always been envious of the Bavarian company’s previous simple model names.

Consequently, the new Z4 will arrive with the entry-level model being called the Z4 sDrive23i. We’re not sure what the ‘s’ stands for and, while you would expect the ‘23’ to indicate the engine size, it will actually be powered by BMW’s familiar 2.5-litre six-cylinder engine, with 150kW of power (10kW less than at present) and an unchanged 250Nm of torque. BMW says the numbers are now indicative of each model’s performance level.

The base model will accelerate to 100km/h in 6.6 seconds when fitted with the standard six-speed manual gearbox, but that blows out to 7.3 seconds when fitted with the optional six-speed automatic (though consumption improves from 9.2 to 8.9L/100km).

Step up to the normally-aspirated 3.0-litre straight-six and the extra urge (down 5kW to 190kW and down 5Nm to 310Nm) reduces the sprint time for the sDrive30i to 5.8 seconds (auto: 6.1 seconds) while consumption goes to 9.2L/100km (9.0 for the auto).

BMW’s brilliant direct-injection turbocharged version of the 3.0-litre petrol engine makes a welcome appearance in the sportscar range, delivering 225kW and 400Nm, and powering the sDrive35i to 100km/h in 5.2 seconds.

Better still, the auto option for this new twin-turbo Z4 flagship model is BMW’s new seven-speed double-clutch transmission, which changes faster than a human being and consequently produces a better sprint time at 5.1 seconds as well as better consumption (9.4L/100km versus 9.8 for the manual).

The metal retractable roof – the first for a BMW roadster, but now standard on the 3 Series convertible – is a two-section lightweight aluminium unit that opens and closes in 20 seconds via either a centre console switch or the central locking remote control.

With the roof retracted into the boot area, luggage space is reduced from 310 to 180 litres, but BMW claims there is still enough room for a medium-sized hard-shell suitcase.

With the roof up and using the standard through-loading facility to the passenger compartment, BMW says the new Z4 can carry two full-size golf bags or four crates of large bottles.

Minor storage areas include a 10-litre glovebox, folding compartments in the door linings, centre console areas (including a large one under the armrest) and a box in the instrument panel.

As well as providing more space for the occupants, the new interior features BMW’s familiar iDrive “human interface” system for the first time, but in its more user-friendly second-generation guise with simpler navigation and quick-access programmable favourites buttons.

Audio and navigation functions are displayed on an 8.8-inch screen that pops up on top of the dashboard, as it does with the current Z4, and the system includes an 80GB hard-disk with 12GB set aside for storing music.

BMW claims that the new-look interior is more driver-oriented and features standard leather seats, employing the company’s familiar sun-reflective technology that makes it less hot to touch, integrated headrests and, of course, an optional wind deflector.

BMW’s Dynamic Drive Control system is fitted as standard, enabling the driver to select three drive modes that vary the set-up of the drivetrain, suspension, throttle response, electronic stability control thresholds, power steering assist and, when fitted, the shift points for the optional automatic transmission and M Sport electronically adjustable dampers.

As well as the electric power steering, the suspension architecture both front and rear is carried over from the current rear-wheel drive Z4.

A new push-button electric park brake is standard on the new Z4, along with run-flat tyres, a tyre pressure warning system and alloy wheels (17-inch up to 18-inch for the flagship).

Although the big grille suggests that BMW is providing plenty of breathing capacity for bigger engines, the word from Europe is that there may not be enough room under the bonnet to fit the V8 engine from the M3, so the future of the Z4 M is not clear.