Model: BMW Z4 M
Price: £42,750 (range starts with 2.0i at £22,945). On sale now
Engine: 3,246cc, six cylinders, 24 valves, 343bhp at 7,900rpm, 269lb ft at 4,900rpm
Transmission: six-speed gearbox, rear-wheel drive
Performance: 155mph, 0-60 in 4.9sec, 23.3mpg official average
What a wonderfully retro idea. A powerful, front-engined sports car with manual transmission, a long bonnet and a licence to thrill. Something like an Austin-Healey, perhaps (as seen in our centre pages)? A Jaguar XK120? A Chevrolet Corvette? Retro indeed.
Hardly anyone creates such a thing nowadays. Just Chevrolet, still making Cor-vettes in a modern interpretation of the old formula, TVR - and, now, BMW.
Yes, the Z4 roadster has gone hard. The whole range, containing a surprising number of variations, has just had a makeover with new lights, new valances to define those lights' edges, and some new engines. The mightiest of these is the 343bhp, 3.2-litre, straight-six engine that powered the now-defunct BMW M3 to such bombastic and sonorous effect, and which now finds itself under the Z4's flame-surfaced snout while BMW readies the next-generation M3 (which may, in fact, be a V8).
The result is the Z4 M, expensive at £42,750 but likely to make a certain sort of driver salivate copiously. Nothing wrong with that; driving can be so much more than a utility task. The surprise is that it has taken BMW so long since the Z4's launch in 2002 to come up with the M version.
Anyway, it's here now, complete with a fiercer face (thanks to bigger air intakes), crease-lines on the bonnet to emphasise the beating heart beneath, fatter wheels and four exhaust tailpipes.
Those bigger wheels - more so at the rear where the tyres are a massive 255/ 40 ZR18 in size (the fronts are 225/45) - are attached to suitably firmed suspension. They are steered by a hydraulic power-steering system energised by an electric pump in place of the regular Z4's fully electric arrangement, a change made for two reasons. Electric systems don't exist that can control such high forces. And pundits have been lukewarm about the regular Z4's steering feel, although it has improved since the range's launch.
The Z4 M also has a "variable M differential lock", which progressively sends up to 100 per cent of the engine's effort to the rear wheel better able to make use of it - the opposite of a normal differential, in which a spinning, gripless wheel sucks all the energy away from the one with the grip. With the stability system turned off, then, we have a recipe for powersliding fun should the chance arise.
Such an opportunity won't arise on roads with traffic, however, where discretion must rule. This is especially true in the low-speed, Highway-Patrolled US where I'm driving BMW's latest M-car. We're there because the Z4, and the X5, are made in Spartanburg, South Carolina, so we're trying the cars in their home surroundings before they are shipped over to the UK to join BMW's demonstrator fleet. So we're in right-hand drive cars in the US, and strange looks are heading our way.
The stereotypical view of the US is of long, straight roads, four-way intersections, lumbering SUVs driven at 55mph, total driver disengagement. It's different in the Blue Ridge Mountains. Fabulously bendy roads open out to vast misty vistas, a challenge to man, woman and machine, hardly another soul in sight. Here the Z4 M should be in its element, engine speeding up to 7,900rpm to reach that 343bhp power peak, all six throttles wide, front tyres biting hard, rear wheels always on the edge of grip as we power out of every bend.
Downhill it's mind-concentrating; some corners are damp but the brakes, taken from the M3, are indefatigable. Uphill it's more fun, because you can use the power to help steer this Z4 out of every bend.
Howling along in this power-infused convertible with, claims BMW, the world's fastest-folding soft-top, all should be heavenly. But all is not quite right. The steering, despite its hydraulic assistance and firm weighting, is numb around the straight-ahead. The accelerator, for all its eagerness to let the engine sing when prodded, has some stodge at the start of its movement before latching on to action.
This makes a driving flow hard, with clutch and accelerator too often mismatched as you move through the six gears.
This is highlighted by a drive in a lesser Z4, the new 2.5 Si fitted with the higher-output (218bhp) version of BMW's ultra-light, magnesium-block engine plus firmish "sport" suspension, a combination offered for £30,725. It still sounds terrific - a good straight-six engine has a note whose smoothness is matched only by a V12's - and it pulls with gusto through the gears, if not with the M-car's five-seconds-to-60 bombasticity.
And, crucially, it's easier to drive thanks to a more fluid interplay between the major controls and a slightly more supple ride (all Z4s have an impressively stiff structure, free of shake and shudder). Even the steering is acceptable now, thanks to some remapping of the electronic assistance system. For real roads this is actually a nicer car.
Back at the BMW Performance Centre opposite the factory, however, there's a chance for the Z4 M to redeem itself. There's a circular skidpan soaked with water, the Dynamic Stability Control (DSC) is off and the challenge is to hold a lurid powerslide without spinning or correcting into a violent fishtail.
Three or four laps and the required gentle touch is learnt, so now I can drift at will, even if I'm not skilled enough to hold the slide for laps at a time. This is a fabulously controllable car, and even with the DSC switched back on there's quite a lot of tail-out freedom before the system reins you in.
Then to a high-speed slalom followed by S-bends, a tight turn and a good straight. The lap times of this tight circuit are similar for M-car and 2.5 Si, but the styles differ. The Si feels lighter, more willing to flick in and out of the bollards, but ultimately its front wheels run wide sooner and neither steering nor brakes have the M-car's precision.
The Z4 M is less about flow and momentum, more about squirt-brake-steer-squirt-aim-squirt-again. You have to haul it harder, but not only do the front wheels resist running wide, the rear wheels are ever ready to power outwards to detonate you to the bend's exit as you unwind a little steering to catch the incipient slide.
This is the true sports car, the latter-day four-wheel drifter, the car that reminds you of the raw dynamics of driving without the veneer of civility most drivers have now come to expect.
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