Road test: BMW’s roofless pursuit of fun with Z4

By Stuart Farquhar
Published on 28/07/2012 16:25

GIVEN the summer we’ve had so far (the blue sky you see in this picture lasted less than five minutes), buying a car with a retractable roof in Scotland might seem as worthwhile as installing an expensive burglar alarm in the Easter Road trophy room*. But while some of the coupés and cabriolets we’ve tested here at Scotsman Motoring can count their open-toppiness as one of very few redeeming features, the BMW Z4 28i has so much else going on that it could rain non-stop until the four horsemen of the apocalypse trot through the Hampden turnstiles to watch Hibs lift the Scottish Cup* and I would still be in love with it.

No, the big news here is not the roof, it’s the engine. In the luxury sports coupe wee-weeing contest, the Z4 is up against the likes of the Audi TT, Mercedes SLK and the Porsche Boxster. Until the arrival of the sDrive 20i and 28i, BMW’s 3.0-litre six-cylinder Z4 was dribbling all over its own shoes in the economy stakes compared to the more efficient Audi. But a clever bit of plumbing has taken care of all that.

The Z4 20i and 28i were among the first in the BMW range to benefit from the manufacturer’s new 2.0-litre, four-cylinder TwinPower N20 engine, which is now hitting the 1, 2 and 5 series, and boasts a 20 per cent improvement in fuel economy and CO2 emissions compared to the six-pot 3.0-litre engine of its predecessors.

Chucking two cylinders and a whole litre of displacement out the window seems like a lot of compromise in the name of economic and climatic meltdown. But it isn’t, and you realise this from the moment you put the foot down and BMW’s clever plumbing comes to the fore. It’s called a twin-scroll turbo and it would take a 32-week serialisation in Scotsman Motoring to properly explain how it works but, simply put, the exhaust manifold draws exhaust gases from certain cylinders at certain times before sending them into the turbine, meaning each cylinder gets a proper deep lungful of fresh air rather then a slight draught driven by a smoky fart from its neighbour. Because none of the cylinders’ emission gusts interfere with each other, the turbine can spin faster and stay cooler, which matters.

Absolutely none of this information was of any interest to me when I was driving the Z4, however, because I was much too busy having fun. All that mechanical mumbo jumbo really means is that this thing is fast – fast enough to reach 60mph from a standing start in 5.7 seconds and go all the way up to BMW’s electronically-limited 155mph top speed. While it’s a few horses short of its predecessor, leaving a still-frisky 245bhp, torque is up to 250Nm and it’s delightfully rapid at getting you up to motorway speed, without it having to work too hard, and with very little, if any, turbo lag.

Ditching a couple of pistons also means the 28i is a little lighter than six-cylinder Z4s, with the engine moved little more towards the middle of the car from the front, which allows for a hugely reassuring sense of balance, poise and grip when tackling country roads. The M Sport I drove had BMW’s usual offering of Comfort, Sport and Sport+ modes, which alter suspension and throttle according to how you fancy driving on any particular day.

While driving purists may always insist on manual transmission, my 28i was fitted with an eight-speed automatic gearbox, which, when in Sport mode, quick-shifted and rev-matched well enough to keep me amused.

The automatic makes for a point-and-go, user-friendly sports car which is a pleasure pootling about town or breezing up the motorway. Slip it into manual mode, and you can run through the gears with the enjoyably clicky and responsive paddles behind the lovely little leather steering wheel the M Sport comes with. While that slightly spongy ergonomic wheel is something you could happily grip onto all day long, though, it doesn’t communicate the road surfaces to your hands as clearly as you might expect in a sports car.

As with all BMWs, build quality inside and out is premium, as it should be at these prices. The options-encrusted car I drove cost around £10,000 more than the £36,810 on-the-road price for the 28i M Sport. Unfortunately, looking down the options list to try and chip away at that £10K, there aren’t many items I’d be willing to ditch.

The navigation system cost £2,225 but you’d have to prise it out of my cold dead hands because BMW makes the best system out there. And I’m keeping the £1,845 sport automatic transmission, but I certainly could dispense with the Pure Balance Design interior colour coding at £1,250.

Behind the seats, there’s a little bit of stowage space, into which a couple of small rucksacks fit fine. The boot holds 310 litres – a lot – when the roof is up and 180 litres – not a lot – when the roof is down.

Whether the roof is up or down has little bearing on the stunning good looks of the Z4. Those swooping, elegant lines and that long, long bonnet make it a real headturner either way. And if you do catch a glimmer of sunshine, press the button and that roof performs a glorious 20-second ballet of mechanised folding, pivoting and sliding to tuck itself away before the rain returns and you get to watch the whole magnificent dance again. It’s the kind of technology, that how-do-they-do-that engineering also found in the engine, which makes the four-cylinder BMW Z4 sDrive28i such a compelling – if rather expensive – proposition.

* Some of my best friends are Hibees.

VITAL STATS

CAR BMW Z4 sDrive28i M Sport

PRICE From £33,645 (£43,995 as tested)

PERFORMANCE Max speed 155mph; 0-60mph 5.7s

MPG 41.5 combined

CO2 EMISSIONS 159g/km