BMW Z4 2006 Review

Experience tells us the BMW roadster has emerged as closer in character to Benz's softer but competent SLK than the razor sharp Porsche. In terms of total sales it also sits midway between the two, though 2005 saw it fall to less than 300 cars Down Under. This was behind both rivals and less than a third of Mercedes SLK sales.

For 2006, the Z4 gets what its maker has termed a "mid-life freshen up". In essence, BMW has refined the Z4 a little more -- we'll stop short at saying it's knocked off the rough edges... The changes are not so much related to dynamics -- it's still quite sporty -- rather, the mods are in its engineroom, equipment and accoutrements.

The bad news is there has been little if any change to the convertible's unconvincing and at times disconcerting electrically-assisted steering. The good news is the arrival of the new generation, lighter weight, more powerful mag-alloy six-cylinder engines and the extra equipment the update has wrought.

The even better news? A full M3-spec Z4M Roadster arrives reviving the tradition and 'madness' of the original M Roadster -- see our separate CarPoint coverage for details on this cracker!

FEATURES
The latest Z4s get an upgrade in terms of nomenclature. Now dubbed Z4 2.5si and 3.0si, the new badging signifies higher output engines in BMW speak. This is a side benefit of the adoption of BMW's latest N52 series inline sixes -- see Mechanical section below.

The controversial styling of the Z4 range is largely unaltered in this update with changes limited to front and rear 'plastic'.

Up front there's a new valance with wider under-bumper intake and more aggressive 'splitter'. Out goes the circular fog lights, replaced by slimline trapezoidal units that tuck under the more masculine bumper section.

At the rear there's a matching, aggressively profiled rear bumper from which protrude twin larger diameter exhausts. New tail lights (with two-stage illumination) have a more horizontal orientation but 'live' in the same sheet metal openings as old.

The interior remains somewhat Spartan on both the 2.5si and 3.0si variants with the trademark convex brushed alloy dash 'beam' taking pride of place. The tight single-hooded binnacle with deeply set tacho and speedometer is unchanged and doesn't need to be: it screams sportscar (Shame BMW used almost the same unit in the X3).

That said there have been subtle changes to trim colours (stereo surround mouldings for example) and BMW has 'softened' the interior slightly with small but telling details -- like the soft-touch HVAC (heating ventilation and air conditioning) controls.

The convertible hood is electrically operated on both models and also unchanged. Claimed to fold away in under 10sec, the fully automatic soft-top is fully lined and features a heated-glass rear window. Unlike some of the Z4's opposition, the soft-top doesn't seriously handicap boot space. It's also commendably quiet at speed.

The Z4 2.5si kicks off the roadster range priced from $77,600 with the auto model priced at $80,200. The 3.0si starts at $90,800 with the auto the same $2600 premium.
Pricing is up between $3100-4800 on the outgoing model.

MECHANICAL
It's under the skin where most of BMW (and prospective purchasers') money has been spent on the latest Z4s.

Like most of the BMW range, the Z4 now gets the magnesium-alloy-blocked 24-valve DOHC N52 series inline sixes; in both 2.5 and 3.0-litre form. These engines have won high praise for their balance of performance, refinement and weight saving. They are claimed to be more economical than the 'older' engines.

As noted above, BMW uses 'si' on models to signify higher engine outputs. In Australia only single 2.5 and 3.0-litre models will be offered boasting 160kW and 195kW -- up from 141 and 170kW respectively on the original Z4 launched in 2003.

The 2.5 is available in 130kW form in some overseas markets (there's also a four-cylinder car in Europe), and the standard N52 3.0-litre engine as featured in the 330i and 530i produces a claimed 190kW. The Z4 3.0si offered locally shares its slightly more muscular six with the hotshoe 130i. Which by the way isn't an si... Confused?

Engine output semantics aside, these are top-class powerplants, the 2.5 in particular is a very sweet powerplant and a favourite of ours. They are matched to both manual and auto six-speed transmissions (previously only five-speed autos); the latter BMW's latest Sports Automatic.

In addition to gaining wheel-mounted shift paddles, the auto has new (closer) ratios and faster shift times.

Both Z4s also boast a Dynamic Drive Control (DDC) 'Sport' mode button that alters shift points on the auto, and on both manual and auto changes engine management software and steering assistance.

Brakes have also come in for attention on the latest Z4 series. As you'd expect they're vented discs all-round with the 3.0si now boasting an all-new set-up with 325mm front binders. The 2.5si get 300mm front discs -- the same size as the outgoing 3.0i. And not only has the hardware been upgraded, the Z4s benefit from the latest ABS and allied software yielding convenience items like Hill Start Assist, brake drying, brake standby and so forth.

Save for new alloys (18-inch on the 3.0si) and the like, the rest is essentially unaltered -- from the car's massively stiff body structure onwards. If the suspension settings have been altered, our quick drive was too short to pick.

COMFORT
We split our launch time between a manual 3.0si and an auto 2.5si (and the ball-tearingly giggle-inducing Z4M, of course). Like the outgoing models, leather sports seats are standard in both, with seat heating and electric adjustment also standard.

The steering wheel is adjustable for height and reach and the ergonomics are typical BMW... Just so!

You sit a little higher in the standard Z4s but only drivers of Z4Ms will pick this. Roof up or down noise levels are well subdued with the 3.0si's engine noticeably more vocal than the 2.5si. That said it's never wearing and makes its presence known only when you're exercising your right foot.

As you'd expect air-con, auto wipers and lights, CD player, cruise and Bluetooth phone preparation are all standard on both models. The 3.0si gets an upgraded 10-speaker sound system, CD changer and metallic and timber interior trim options to help soften the $13,200 price difference.

Options like M Sport seats and suspension, navigation and Park Distance Control are offered across the Z4 models.

Particular attention has been paid to rollover protection, with the Z4's A-pillars and windscreen frame forming a rollover frame in front of the occupants. Sturdy fixed steel rollover bars are combined with a massive rear cross member to complete the safety cell behind.

Sold as a safety and convenience feature, the Z4 uses 'run flat' rubber. In a vehicle like the Z4 it's probably a good choice, given the urban nature of the average roadster buyer. That said the 'run flat' debate continues. Read CarPoint's run flat story here

Honda's S2000 ($72,590) probably deserves a mention as does Nissan's 350Z convertible (Track model $73,990) -- though we doubt people actually shop these cars against the Z4. Same goes for Crossfire Cabrio -- SRT6 or $69,990 cooking model.

No, it's the Germans that are the main rivals though all three cars are quite individual. The SLK doesn't have a soft-top -- its folding steel roof might upset purists. And the Porsche is mid-engined -- not the front-engined Healey-like mould of the true sports roadster says BMW.

Pricing sees the base SLK 200 hit from $85,300; midway between the BMWs. The top six-cylinder SLK 350 weighs in at $110,900. Porsche's base Boxster is $107,400 on current pricing.

ON THE ROAD
The combination of the 160kw 2.5-litre six and the six-speed auto in the latest Z4 will win more than a few hearts. This is a wieldy, sprightly sports roadster that offers plenty of bang for your Euro-bucks.

Ride on standard 17-inch wheels (up from 16s on the last model) is good though oddly not as subtle as the low slung (and conventionally-tyred) Z4M.

In isolation this entry-level combination is plenty fast enough. BMW quotes a 0-100km/h time of 6.9sec (0.4sec faster for the manual version) for the 2.5si which is 0.6sec faster than the old 2.5i and only 0.7sec slower the 'old' auto 3.0i.

Overtaking performance is good too, matching its manual stablemates roll-on times thanks to the new fast shifting auto.

The DDC sport button enlivens throttle response and gets the auto into action quicker. It also weights the steering -- cutting assistance levels. But it's here that the whole plot starts to get a little lost.

In the 2.5si, the Sport setting for the steering is the best steering a standard Z4 delivers. There's sufficient weighting but feel is still dull and there's little in the way of communication -- especially just off straight ahead On the 2.5si's standard setting the steering is just as uncommunicative and arguably too light for a car with sporting pretensions.

Add the extra mumbo and bigger 18-inch rubber of the 3.0si and the equation gets worse... and you're going a whole lot faster, to boot.

With close to 200kW, the 3.0si gets to 100km/h from standstill in 5.7sec and charges hard into the 100-190km/h range. On anything other than smooth roads you can't help but feel you are steering the car via a video game handset. There's an impression that you are chasing the car's front end as it wanders over irregularities. The tiny corrections we make almost subsconsciously when driving become, well, conscious.

It's not worrying but it's not nice either. No wonder BMW's M division has junked the electric-assisted steering of the standard Z4 for a conventional hydraulic set-up for its muscular Z4M. And the difference is chalk and cheese.

The shame of it all is that the 3.0si should the considered choice: it's more hairy-chested than the 2.5 but not balls-out like the M. That 3.0-litre engine is a gem and we love the seated-over-the-back-wheels Cobra/Healey style driving position and feel.

If you're not as sport focused and you can live with the steering you will appreciate the hewn from solid feel of the Z4: There was not an ounce of flex or shimmy even on the bumpy Northern NSW roads we drove during the launch.

The manual gearbox is precise and ratios well chosen -- top marks again. Shared with the Z4M, the only hiccup is the big gaps between fourth, fifth and sixth. This makes for relaxed cruising but means snap fifth-third downchanges need a big boot of throttle to balance the revs.

We like the updated Z4, but as with the original we can't help think what could have been. The new engines and equipment have added appeal to the Z4 but it is still handicapped by less than satisfactory steering precision.

But for a dose of conventional engineering at the pointy end, the Z4 could be BMW's performance bargain. BMW's best engineers must have thought so too -- that's why they built the Z4M.