BMW Z4 Coupe v Porsche Cayman S 2007 Comparison

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So, after all these years, how exactly are we meant to pronounce coupé, anyway? Is it 'coop', as Americans like to call it, or is that strictly for turkeys? Or does the fact that it’s a French word ('cut'), with the same acute accent as a popular brand of instant coffee, make 'coopay' correct?

More to the point, what is a coupe? In the modern, automotive context, it's anything but clear.

A mid-engined, purpose-built, two-seater supercar is a coupe. But so is a four-seater that's no more than a two-door twin of a sedan. The first generation of BMW 3 Series sedan was actually a coupe. A Porsche Cayman S is a coupe. A BMW M3 is a coupe. A BMW Z4M Coupe is, er, self-explanatory.

I'll explain it anyway. It's yet another kind of coupe; a high-performance, enclosed version of a two-seater convertible. With a claimed torsional stiffness of 28,000Nm  per degree, it’s significantly more rigid than the open Roadster and, given the dark magic they've conjured beneath the $127,200 Z4M Coupe's Brylcreemed-and-backswept lines, it could use it.

Most significant is the shoe-horning in of the M3's strato-revving 3.2-litre in-line six, good for 252kW at 7900rpm and 365Nm at 4900rpm. Roughly speaking, those figures are almost a BMW 120i-worth beyond the base 2.5-litre engine available under a Z4's bonnet.

Tellingly, however, there are a few things that don't carry all the way through to the Z4M Coupe. Like the SMG II gearbox, replaced here with a conventional, six-speed manual. It also gets one-touch DSC, specifically calibrated and evidently not of the two-stage type.

The steering isn't the standard Z4's electric-assist, either, but old-fashioned hydraulics, pirated from the M3 for reasons of feel. The tyres (18-inch Continental Sport Contacts) aren't run-flats, for reasons of ride; combined with the M’s stiffened suspension, run-flats would render it utterly unbearable. And we'll stop this with the brakes, track-ready, cross-drilled and vented from the M3 CSL.

The Z4M Coupe's standard equipment list is pitched high for its $127,200 sticker. The two leather seats boast full electric adjustment with memory, (manual) under-thigh slides and a first-aid kit beneath the passenger. A storage cubby on the rear bulkhead houses the black boxes for the standard sat-nav and six-stack CD systems. Park-distance control would seem a welcome fitment on a waterfall-nosed coupe but, bizarrely, it has sensors only on the rear.

The Porsche Cayman S ($148,500) is another high-performance coupe grown out of an existing, two-seat convertible, the Boxster S. The two share the 3.4-litre, mid-mounted flat-six that develops 217kW at 6500rpm and 340Nm at 4600rpm. Like its Munich rival, the Cayman S drives through a six-speed manual box (five-speed Tiptronic S is an option) with PSM stability control as standard.

Dimensionally, the Porsche is some 228mm longer than the BMW, and 20mm wider. (The 1350kg Cayman is just five kilos heavier than its sister roadster; between the BMW Z4Ms, the 1495kg coupe is 10kg heavier than the convertible). Much more intriguing, however, is that the Cayman S still costs $14,000 more than the Boxster S.  At BMW, the Roadster undercuts the Coupe by $3300.

On paper, the Cayman S looks opportunistic against the more powerful, better-equipped BMW. Stuff like satnav, multi-disc CD changer and climate-control for the A/C are all optional on the Porsche, while the standard seats are 'leatherette' with Alcantara inserts and almost entirely manually adjusted.

Our test Cayman, loaded with bi-colour leather interior ($5490), cabin carbon (over $6180), 19-inch wheels, optional rear wiper and a bunch else, came to $171,580.

Everyone lurves the Z4M Coupe's dash -- black leather textured to resemble raw carbon-fibre. After that, however, there's less to write home about, starting with the air of blackness and hard, dog-nose textures on the upper dash.

The electrically adjustable seats wedge your body between hard side wings. But it's only really uncomfortable on the cushion, where your right thigh must rest to compensate for the slightly offset pedals. The door armrest also nerfs at the elbow, but there's plenty of headroom.

Height and reach adjustment grace the manually adjustable steering wheel. And what a wheel: it's like driving with a Kransky sausage in each hand. The instruments attempt a finely-marked chronograph feel, but end up looking a little underdone. (That might also describe the Cayman S's standard interior, which so underwhelmed our design judges at WADA 2006.)

From behind a thinner, larger-diameter wheel on a heightand-reach column, however, the Cayman S immediately feels lighter and more spacious. There might be only millimetres of difference in interior dimensions, and the two might be comparable for rear three-quarter visibility (the BMW's forward view handicapped by fat A-pillars and a bulbous mirror), but the Cayman's slightly larger glass area and (optional) lighter interior colours serve to exaggerate its roomier, less claustrophobic cabin.

Despite less adjustability, the Cayman's broader cushion makes for marginally superior seating. The rather cheesy, silver-faced instruments are at least comprehensive, clearly calibrated and stylishly housed. Too bad the sound system is ordinary, next to the BMW's door-doofing monster.

There's at least twice the Z4M's oddments storage space, and if luggage matters to you, it's Cayman all the way. Its rear hatch is reasonably useful, but the front boot is like a plunge pool, able to swallow two decent-sized suitcases. Meanwhile, the Z4M's space-eating battery and puncture-repair kit makes for an impractical shape of what remains.

Your pricey, preening Porsche should be getting a good look at the BMW's boot, too -- at least on paper. BMW's claimed 0-100km/h acceleration figure of 5.0 seconds puts the Z4M Coupe quicker by 0.4sec; an eternity between the futures-trading floor and lunch. Mind you, if it's a long way to lunch, the Cayman claws some back with its ungoverned top speed of 275km/h.

On a stinking hot and dry day, two-up and with their respective tracky-controls disabled, the difference wasn't so great. We couldn't match BMW’s claim, the Z4M's torque too easily overwhelming even the grippiest patch of track. Our smoothest and swiftest 0-100km/h run netted 5.5sec.

The Cayman S, meanwhile, has to go looking for a slippery surface to get some wheelspin (and avoid violent axle-tramping). It bagged a best of 5.7sec and the two deadheated over the standing 400 metres, at 13.8sec.

Aside from being fast, being coupes, and being at least ostensibly German, they don't have much in common. The Z4M is built in the US, and if BMW's intention was a raw, mini Dodge Viper 'coop', it has come close to the mark. The engine is hard-edged and urgent in its power delivery, utterly unselfconscious about the chest hairs hanging out of its Tommy Hilfiger shirt.

Seat of your pants, BMW's rolling acceleration blows the more linear Porsche away. Remember, this 3.2-litre's power and torque are bang in the ballpark with a 3.6-litre 911 -- and for low- and mid-range grunt, the Cayman S is no 911.

Creditably, then, the BMW also trumps the Porsche on fuel efficiency, consuming an average of 11.7L/100km against the larger-engined Cayman's 12.3L/100km. Offsetting that is the Porsche’s 64-litre fuel capacity, versus 55 in the BMW.

So, the BMW is fast -- but man, is it frustrating. The throttle has a sense of fly-by-wire artificiality, most annoyingly in Sport mode where it exaggerates any small adjustments and lifting for gearchanges. The responsiveness also seems to vary, slightly but perceptibly, from one light application to the next. Compounding all that is a reasonably heavy clutch, a notchy (although rapid-fire) gearbox, grabby (although resolutely effective) brakes, firm and immediate steering, a restless chassis and an unrelenting ride.

Strange, then, to think of a Cayman S as the calm and composed half of this comparison. Just over six months ago we were getting our butts nipped by the snappy-tailed Cayman in a Porsche comparo (Wheels, June issue 2006), and again raising a sweat through Lang Lang's fast flip-flop section during recent COTY testing. And yet it's the Porsche that’s the most fluid, relaxed and ultimately -- easily -- the fastest to drive here.

The smooth and linear power delivery, punctuated with a VarioCam snarl at around 4000rpm, is wrung out via a light and quick six-speed shift with ratios a tad tighter than the BMW’s. Stepping over to the brakes, there's a light and progressive feel, with a firmer foot quickly finding strong retardation.

Your hands are hooked to the most sublime steering on the market. The larger wheel feels almost old-fashioned after the BMW's, but it's what happens below, that begins to distinguish these cars.

The Z4M's steering has an off-centre immediacy that gives it a quicker initial turn-in than the Porsche. Which ought to be a good thing, except that the near-zero 'sneeze factor' makes the tramlining of the 18-inch tyres a chore on rippled surfaces and steeply-crowned roads.

This firm, fat-tyred feel is more natural than that of the electric-steered regular Z4, but it doesn't translate to exceptional grip in the front end. Once into the turn, artificially-engineered understeer restricts corner speeds, even on smooth surfaces. On patched surfaces, the orange flicker of the DSC warning light is a constant companion when you try to lean hard on the bouncy rear end.

The Porsche rides almost as firmly but tracks across, rather than into and over, bumps. Though potentially disadvantaged by the optional 19-inch wheels, the Cayman S claws across the road's surface, maintaining a squat, confident composure that's quite beyond the eternally busy BMW.

Quite aside from weight distribution (50/50 BMW, 47/53 Porsche), the feel is simply explained by the Porsche being less powerful but lighter, the BMW more powerful but heavier.

Occasionally, one arrived quickly at a corner in the Z4M and instead of brushing the grippy brakes, popping the firm clutch and keeping a firm hand on the excitable steering, just to heel-and-toe back a cog, a better choice was to simply leave it in third and ride the torque. This is the essence of the Z4M; despite its undoubted pace,appeal and dynamic ability, it's always busy, never relaxing and sometimes a chore. It's a frenetic personality that appeals to some, but here is overshadowed.

In the Porsche, you'll spend your Sundays looking for this sort of scenario. Its nailed nose is slower to turn in, but stays exactly where it's planted and delivers superior feel and feedback as it roots out grip. One can feel the rear end toeing out to help turn-in, and we all know what happens next in the mid-engined Cayman S...

Except it didn't. For reasons unknown, this car was better behaved than any previous Cayman S we've driven. We called Porsche Cars Australia to check that there had been no running changes, that nobody had sneaked Boxster bushes into the rear suspension.

We then ran through a checklist comparing this model to previous examples, the only marked difference being no Porsche Active Suspension Management; earlier drives, on 18s and 19s, all had PASM.

Not wanting to get into the myriad layers of PASM's capabilities, I’ll just say that in this car, direction changes and trailing throttles were nearly Boxster-benign. I could lean hard on the rear end and confidently run out to the road's edge, making corner exits -- as with the entry, and mid-corner -- something beyond a 'production car' experience.

And therein lies the distinction between these two cars, both called coupes. The Z4M made me think of a sports sedan, a regular production model bull-worked up to the role of hulking high-performance car. Artificial restraints keep its compromises in check.

With most such sports sedans and coupes, one forgives these dynamic limitations for their daily-use comfort and practicality. Which you don't get in the Z4M Coupe.

The Porsche, however, is supercar-lite: a purpose-built, mid-engined sports car, over-engineered for what this class of power is asking of it. It covers ground enjoyably and effortlessly. I didn't think I'd be saying that about the Cayman S, a car I still can't rationally recommend over the substantially cheaper, better and now identically-engined Boxster S.

If you're after a truly sublime sports car experience, and a $20K premium doesn't bother you, this test has to go to the Cayman S. And for everybody else, wait for the real M coupe: the BMW M3.

M-EMORIES
BMW won't admit it, but with the next M3 going V8, the Z4M Coupe and Roadster will be the final resting place for its iconic S54 3.2-litre straight-six. This high-revving, 252kW/365Nm, 3246cc unit first screamed into Oz with the launch of the E46 M3 coupe in May 2001. In 2003, the limited-edition CSL saw the ultimate incarnation of this engine, with a new intake system unleashing 265kW/370Nm and a freakish, feral noise. S54, you will be missed...