BMW has given its new Z4 two-seat sports car a retractable hardtop, plus a raft of technology changes, and has stretched its dimensions. It is more than a decade since one of the car’s main rivals, the Mercedes-Benz SLK, appeared with a folding hardtop, and the trend toward this roof solution for sports cars has been clear for some time. The Z4 uses an electrohydraulically operated two-piece system with an operating cycle speed (to open or close) of 20 s.
The car, to be shown for the first time at the 2009 North American International Auto Show this month, will be available with three six-cylinder engine options.
The smallest-capacity (2.5-L) sDrive23i produces 150 kW (201 hp) at 6400 rpm, with 240 N·m (177 lb·ft) from 2750 rpm, using a standard manual six-speed gearbox, and provides the car with 0-100 km/h (0-62 mph) acceleration in 6.6 s and a top speed of 243 km/h (151 mph). Combined fuel consumption is 8.5 L/km, and CO2 emissions are 199 g/km.
The middle range engine for the 3.0-L sDrive30i has 190 kW (255 hp) at 6600 rpm and 310 N·m (229 lb·ft) from 2600 rpm. In this form, the Z4 takes 5.8 s to reach 100 km/h, and top speed is limited to 250 km/h (155 mph). Fuel consumption and emissions figures are the same as those for the 2.5-L version of the engine.
The top engine version is the 3.0-L twin-turbo sDrive35i with 225 kW (302 hp) at 5800 rpm and 400 N·m (295 lb·ft) from only 1300 rpm. Zero to 100 km/h takes 5.2 s, top speed is governed to 250 km/h, fuel consumption is 9.38 L/100 km, and CO2 emissions are 219 g/km. An option for this power unit is a seven-speed double-clutch transmission.
A significant aspect of the Z4 is the use of Adaptive M Suspension. This comprises electronically controlled dampers offering three configurations including a 10-mm (0.4-in) reduction of ride height. The Sport+ setting compares directly with the former car’s standard ride.
Also available for the new car is Drive Dynamic Control. As well as allowing the driver to vary the standard of ride comfort, it also provides control of throttle and steering response, Dynamic Stability Control (DSC) response, and gearshift times for automatic or double-clutch cars.
In keeping with other BMW models, the new Z4 benefits from the company’s EfficientDynamics philosophy. This includes brake energy regeneration, electric power steering, reduced rolling resistance tires, on-demand operation of the engine’s ancillaries, and an optimum shift indicator for cars fitted with a manual gearbox. Weight savings include the use of aluminum for the front suspension and subframe.
The latest generation of BMW’s iDrive functions control system is fitted.
To address the need for improved space, the new Z4’s overall length is 4239 mm (166.9 in), 148 mm (5.8 in) longer than the outgoing version, and it is 9 mm (0.35 in) wider at 1790 mm (70.5 in). Headroom is greater by 44 mm (1.73 in), and there is 20 mm (0.8 in) more shoulder room.
Driver visibility around the car is improved by up to 14% and by 40% to the sides.
Storage packaging is far more versatile than that of the old car, with a 15.5-L (0.55-ft³) compartment stretching the width of the interior behind the seats. An optional extra storage pack adds even more capability. Trunk space with the roof down is 180 L (6.4 ft³) and 310 L (10.9 ft³) with it up. A through-loading facility is optional.