What is it?
The BMW Z4 sDrive18i convertible is the entry-level model in BMW’s facelifted Z4 range.
It uses a lower-output version of the 2.0-litre turbocharged petrol engine found in the sDrive20i and sDrive28i, resulting in a less expensive list price of £27,615.
Opting for the sDrive18i saves approximately £2100 compared with the previous base model, the sDrive20i, but it also dispenses with some of the kit. Dual-zone climate control and rain-sensing wipers are, for example, optional instead of standard.
As well as the new engine option, the facelifted Z4 benefits from small cosmetic tweaks to keep it fresh among rivals such as the Mercedes-Benz SLK. These include white LED ‘corona’ rings around the headlamps and a smattering of chrome trim.
What's it like?
Under the BMW’s bonnet, you’ll find a 154bhp 2.0-litre ‘TwinPower Turbo’ engine, which features a single twin-scroll turbo and variable valve lift and cam timing control. The combination of these technologies allows it to generate 177lb ft between 1250rpm and 4400rpm.
Although its modest power output translates to a tame but acceptable 0-62mph time of 7.9sec, its wide spread of torque means that the BMW feels flexible and punchy, even in higher gears.
It sounds moderately potent, too, with frequent flutters from its wastegate, audible turbo spooling and a satisfying burble on overrun.
There are no improvements in efficiency, though. The sDrive18i’s combined 41.5mpg and 159g/km of CO2 are the same as the 181bhp 20i’s and 241bhp 28i’s.
Drive is transmitted to the rear by a six-speed manual gearbox. It offers a decent selection of ratios and a short and swift shift action, allowing you to make good use of the power on offer, but its action is baulky and notchy.
The car we drove had several options, most notably 18-inch alloy wheels, adaptive M Sport suspension, sports seats and a Comfort pack that includes a rear wind deflector.