IN AN age of polarising opinions about styling trends, alternative tyres and interior ‘simplification’, most agreed that BMW’s Z4 roadster was more of a driver-focused sports car than the original Z3.

Powered by either a 2.5- or 3.0-litre six, the Z4 sounded good, had cutting-edge looks and was faster than most of its competitors – including the Porsche Boxster. But thankfully, the Z4 was not available with a puny four-cylinder engine which aided residual values and kept hairdressers at bay.

So when BMW previewed the fixed-roof Z4 in concept form at the 2005 Frankfurt motor show, sportscar enthusiasts and BMW purists rubbed their hands together and eagerly awaited BMW’s answer to Porsche’s Boxster-based Cayman. But apart from the expensive matte silver paint work and suave nubuck-clad interior, the Z4 coupe pretty much looked the same as the concept.

Developed concurrently with the Z4 roadster as an ‘unofficial’ special project, the coupe shares its long bonnet, stubbed rear, and origami creases and curves with the roadster.

Front on, the only visual difference is the coupe’s ‘double bubble’ contoured roof, said to be an aerodynamic aid while providing more headroom for taller occupants. In profile, the roofline visibly moves the car’s centre of gravity to the rear, hanging above the rear axle.

Trainspotters will also be happy to see BMW’s signature “Hofmeister kick” on the rear side windows.

The sexy rear, which arguably looks tougher and more purposeful than the roadster’s, integrates a large hatch opening and squats like an old-school Corvette, finishing fast and abrupt.

With the additional stiffness of a fixed roof, the coupe’s torsional rigidity is said to be 32,000Nm per degree while the already-taut roadster is rated at 14,500Nm. The coupe, at 1320kg, weighs just 10kg more than the roadster in manual guise.

Powering the Z4 coupe is, according to BMW, the world’s lightest six-cylinder production engine. As shared with the 3.0si roadster, the 3.0-litre-only inline six produces a healthy 195kW at 6600rpm and 315Nm from 2750rpm. However, the reality is that the coupe feels much quicker than its official 0-100km/h time of 5.7 seconds suggests.

First appearing in the revised Z4 range in October 2005, the engine block and cylinder head are made of aluminium and magnesium and weigh 10kg less than the old 131kg aluminium unit that powered 3 and 5 Series, X3 and X5 models.

Employing BMW’s variable-valve timing and valve-lift technologies to maximise power and minimise fuel consumption, our test Z4 coupe achieved a fuel consumption average of between 9.3L/100km and 10.5L/100km, involving daily commuting and hard driving – not far from the 8.9L/100km official claim. A relaxed country cruise should easily achieve the latter.

With its availability of power just about anywhere in the rev range, the coupe is certainly a fast and very rewarding drive. The problem is that it stimulates the imagination of how good the M coupe must be.

In manual guise, gear changes while overtaking are somewhat unnecessary – but are so worth it just to hear the inline six sing at the top of its athletic lungs.

With the feeling of nimbleness, the coupe darts into corners – assuming a smooth surface – lighting up the traction control warning lights and understeering if pushed as it charges out. Press the ‘Sport’ button and the coupe’s abilities, as well as the throttle pedal’s sensitivity, are amplified.

But it is a car you need to drive all the time, requiring full-time concentration, unlike an Audi TT, for example.

So why is this the case?

It comes down to the usual suspects of most modern BMWs: the behaviour of the Servotronic electric steering and run-flat tyres.

Less than confidence-inspiring, the coupe fidgets like a cranky toddler, requiring constant attention and correction over bumps and camber changes just to maintain a straight line. BMW claims the active steering gives a 0.25L/100km improvement in fuel economy as engine power normally needed to drive a hydraulic steering pump is reduced. We would happily sacrifice a little economy for more steering feel.

Thankfully, there are steering wheel audio controls, because God forbid anyone attempting to change radio stations while driving on a curved road. On a smooth surface, however, it can be a little more forgiving.

That said, the 3.0si coupe’s stiff-walled run-flat tyres are a further 5mm lower than the conventionally-shod Z4 M coupe, which brings even more deterioration in ride quality – despite the fact the M coupe runs on lower, firmer M suspension.

These BMW bellyaches aside, there are BMW tasty treats too: a sonorous engine and exhaust note, 50-50 weight distribution giving the driver the feeling of being at the centre of the action, mixed stares from onlookers of either admiration or perplexity, a bit of exclusivity and the Z4’s endless bonnet that seems to stretch beyond the horizon.

Claimed to be roomier than the old Z3, the coupe’s interior is an intimate place to be. Driving enthusiasts will love the low and rear-positioned cabin. Claustrophobics need not apply.

Our silver test car came with a black leather interior which, while tasteful, failed to create any sense of space. Compared to the fabric-roofed roadster, the coupe is also said to offer more headroom. No such complaints from our 180cm tester or from a taller passenger. Entry and exit, however, require a bit of ‘90s R’n’B side-to-side neck shuffling.

The rest of the interior is straight out of the roadster. A sweeping, full-width, brushed-aluminium panel dominates the dash, while two large dials in a hooded surround contain speedo and tacho. Regular controls, plus vents for the climate control air-conditioning, are located in the centre. And like the roadster, you’ll find yourself keeping the peripheral view-deterring TV/SatNav pop-up screen folded down, unless necessary.

Another current BMW criticism – the lack of interior storage – also applies to the Z4 coupe.

Apart from small door pockets, which are useless for big hands, and a larger vertical centre console between the backrests which will have you visiting your chiropractor regularly, a wallet, keys, mobile phone, loose change, or even cigarettes, cannot be conveniently placed or easily reached. At least the coupe has an overhead sunglasses holder.

Open the hatch and it is a different story. With a substantially larger boot space over the roadster, the coupe offers a handy 340 litres of luggage space – though not accessible from the cockpit. While it may not be as commodious as an Audi TT (which folds its superfluous back seat flat) or a front-and-rear booted Porsche Cayman, the Z4 coupe will quite happily accept a decent amount of grocery shopping or a medium-sized suitcase.

Compared to its nearest rivals, the $87,900 Z4 coupe sits somewhere between the new and slightly-sedate 184kW Audi TT 3.2 V6 ($88,900) and the better-handling, better-sounding, but dearer, 180kW Porsche Cayman ($118,000). Of course, buyers can always opt for the twin-topped Mercedes SLK, but you would have to spend at least $101,400 for the 170kW SLK280 to come close to the power credentials of this company of coupes.

Also making an appearance in the Z4 coupe’s armoury of safety equipment is BMW’s latest Dynamic Stability Control system (DSC) which has five additional features. Among them include a ‘Hill Start Assistant’ to prevent rolling backwards on a hill with manual transmissions, ‘Soft Stop’ which prepares the car for a smoother stop by releasing a proportion of braking pressure as the car comes to a standstill, and a brake-drying system, as used by Audi, which periodically wipes the discs of moisture to improve braking performance in wet conditions.

Built alongside the Z4 roadster, X3 and X5 SUVs at the Spartanburg factory in South Carolina in the United States, the coupe is expected to sell at the rate of about 200 Z4 3.0si and M versions in 2007, with a bias toward the high-performance M Coupe.

Like many modern ‘flame-surfaced’ BMWs, the Z4 coupe is sure to polarise opinion. But with the addition of a hardened Helmut, the coupe becomes a testosterone-driven driver-focused Z4 – this side of the M variants – that brandishes its firm fist at Z4 roadster drivers.