ONCE MORE, WITH FEELING
BMW’s perennially misunderstood sports car is back; new platform, serious engine, real intent. Is the new Z4 a driver’s car to really believe in?
ESTABLISHED ROADSTER LORE: Porsche’s Boxster is a great driver’s car, while the Audi TT looks the part but doesn’t drive like it. And the BMW Z4? Bit of both.
At its worst, the Z4 has been a boulevardier that prioritises pose over poise. Great engines, so-so chassis. At its best (Z4M Coupe), it’s mixed brave design with proper hairy-chested driving dynamics.
And now we’ve a new one, a machine BMW’s adamant is an out-and-out sports car. With six-cylinder power where Porsche only offers a four, could the Z4 now be the definitive £50k sports car?
While the Z4’s been developed in conjunction with Toyota’s new Supra (see page 78), there’s plenty of clear water between them. The Supra will be available only as a fixedhead coupe, the BMW a sun-seeking soft-top. Why a fabric roof instead of the previous E89 Z4’s folding hardtop? It’s lighter, it’s faster (taking around 10sec to go from rainswept to cosy, half the time of the old folding hardtop), it lets in less noise on the move and it lowers the centre of gravity a touch. More prosaically, it means you also get the same luggage space whether the roof’s up or down, so there’s a fixed 265 litres instead of the old car’s 310 roof-up, 180 roof-down.
Whether the roof’s up or down, refinement is impressive for a roadster. There’s very little flex in the Z4’s structure, and that rigidity is as much a boon for comfort as it is for agility, extra bracing giving the suspension a consistent basis from which to work. Elbow propped on the door’s comfy armrest, back soothed by the plump seats just as the pliant suspension smooths the road, miles slide by easily in the Z4.
And when you decide to up the pace a little? This Z4 is quick. There’s always been at least one doozy of an engine in the Z4 line-up (the M3-derived 3.2-litre straight-six in the Mk1’s Z4M variant; the 3.0 twin-turbo straight-six4
in the Mk2’s range-topper) and the new car is no different – the top M40i variant still packs a straight-six. A 336bhp evolution of the B58 engine seen in the M140i/M240i and 340i/440i, the unit’s twin-turbocharged but with its throttle response sharpened by software controlling the wastegate. It was also benchmarked against the naturallyaspirated old Porsche six (God rest its soul).
Now that the Porsche is a four-cylinder, the six gives the Z4 something of a theoretical USP. Matching its Stuttgart rival’s handling is a tougher ask, though, and BMW has endeavoured to give the Z4 the best start in life by putting two thirds of the engine behind the front axle for a claimed 50:50 weight distribution – the sports car holy grail – and making it both considerably wider in track (by nearly 100mm at the front) and shorter in wheelbase than the previous Z4. Kerb weight is 1535kg for the M40i, and its 19-inch wheels are wrapped in identical Michelin Pilot Super Sports to those of the BMW M3/4, right down to the size and compound. Suspension is by MacPherson strut at the front, multi-link at the rear, and the M40i gets adaptive dampers as standard, along with uprated brakes and an electronically controlled locking diff (essentially a scaled-down version of the M5’s unit).
The way the steering, dampers and diff interact is key to the Z4’s dynamics. Turn the wheel and the outside front shock stiffens accordingly, for the sharpest possible turn-in, and the suspension’s balance front-to-rear is manipulated on the fly for optimum agility.
‘You can’t divide steering, differential and dampers; they all interact,’ says driving dynamics engineer Florian Dietrich. ‘All four dampers’ compression and rebound rates adapt within 20 milliseconds, taking into account corner speed, steering angle, how fast you’ve turned the wheel, and more.’
As is the wont of modern BMWs, switchable driving modes for steering, dampers, gearbox and engine response ramp up through Comfort, Sport and Sport +, but there’s a more marked difference in feel between them than before. In the latter two, the M40i is really quite tail-happy; begin to squeeze the throttle with some lock on and you feel it immediately tighten its line; tread a little more firmly and the rear quickly scooches round into mild oversteer. Its sudden transition is characteristic of a short wheelbase, but it’s not unsafe, or intimidating; just a little more keen to play than you might expect, like an excited puppy. Perhaps the Z4 really is a no-caveat sports car at last…
Rivals? The Z4’s traditional sparring partner, the Mercedes SLC (nee SLK), will soon be put out to pasture, and its replacement is unconfirmed. Audi’s TT Roadster isn’t going anywhere, though, and in RS form is now a very potent (if numb-feeling) sports car. Jaguar’s F-Type is brimming with character and sense of occasion, if not perceived quality. And the Boxster and its tin-roofed Cayman twin, are hardy – and hard to beat – perennials.
The top-dog Z4 M40i will be supplemented by the sDrive 20i and sDrive 30i. Both will use the same 2.0-litre four-cylinder turbo engine, with 196bhp in the 20i and 256bhp in the 30i. Despite early rumours of all-wheel-drive capability, all Z4s will be rear-wheel drive, and all use an eight-speed torque-converter auto gearbox (although a manual 20i will join the range in July as the entry-level Z4). New roadsters are an increasingly rare breed but BMW’s engineered this one like it means it: trick dampers, racecar track widths, a peach of an engine and, inside, its latest digital instrument cluster, as seen in the 3- and 8-series, plus the latest iDrive 7.0 infotainment system. It’s engaging and searingly quick, and if it’s a little too comfort-biased then a meeting with a handy mid-engined Porsche will soon show up any dynamic shortcomings… And what’s this, an incoming call from CAR’s Georg Kacher, waiting for me just up the road in an idling Cayman… Over to you, Georg.4