2019 BMW Z4 M40i performance review

BMW sniffs an opportunity for its third-generation Z4 roadster. In its reinvention, specifically in M40i range-topping guise, it could well plug the gaping hole in six-cylinder roadster enthusiasts’ lives left by the demise of the flat-six Porsche Boxster and Cayman.

Yeah, we know there are boosted V6 versions of the Jaguar F-Type and Mercedes SLK, but those cars can’t hold a candle to the latest Porsche 718’s chassis. Can the Z4’s? BMW certainly thinks so.

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The previous Z4 was a soft pudding of a car, but you get the sense that the engineers in the company were given more of a say this time around. The new model is 85 millimetres longer, 74mm wider and 13mm taller; while the front and rear tracks have been increased by 98 and 57mm respectively.

So far, nothing too unusual, but then you’re told that the wheelbase has been shortened, giving the Z4 an all-square stance on the road, with the chassis team’s eyes firmly set on the centre of the target marked ‘agility’.

To make the most of the layout, BMW focused on the rigidity of the body, creating the stiffest structure of any open-topped car it has yet produced. On top of that, the lardy, high-mounted folding hardtop of the previous Z4 was binned, in favour of a light new fabric roof. That not only reduces overall weight, it also helps bring the centre of gravity down and, as a side benefit, it neatly folds away (at speeds of up to 50km/h) in front of a much-enlarged boot space (in just 10 seconds).

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It’s black as standard or Anthracite Silver as an option. The latter works particularly well on the Z4 M40i, which gets the usual Cerium Grey details found on a BMW M Performance Vehicle – though they’re admittedly lost when put up against the Frozen Grey paintwork of the test car.

Still, your eyes will be too busy digesting the weird new kidney grille mesh up front and the protruding aerodynamic breathers behind the front wheels to worry about trim colours, though we reckon there’ll be universal approval for the muscular rear end and high-tech LED lights.

The keen-eyed will note there are mixed tyre sizes front and rear, which is the case across the whole Z4 line-up – and again reinforces our sense that the engineers were listened to for this car’s development.

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There’s more technical goodness underneath as standard in the M40i, including Adaptive M Sport suspension with electronically controlled dampers, M Sport brakes and, perhaps most importantly of all, an M Sport differential on the rear axle. All Z4s send their power to the back through the latest development of BMW’s excellent eight-speed Steptronic automatic transmission.

This comes with tactile gearchange paddles behind a high-quality three-spoke M-branded steering wheel in the M40i. The rest of the cabin is neatly styled and beautifully put together. You sit down low with plenty of adjustment in the seats and steering wheel.

While the new Z4 is civil with its multi-layer roof in place, you buy a roadster to drive it with the wind in your hair, right? What’s more, you’ll want to do that to let your ears have unhindered access to the exhaust note.

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It’s a sonorous tune that only a straight-six could sing, even a turbocharged one. There’s 250kW of power from 5000-6500rpm and this engine really does encourage you to go looking for it all with a purposeful, yet cultured snarl, the soft limiter not kicking in until 7000rpm. Not that you need to use that much of the rev counter, as there’s a chunky 500Nm of torque produced from 1600-4500rpm, making the M40i feel rapid regardless of engine speed or gear selected.

That’s especially the case if you choose Sport or Sport Plus driving modes, as everything sharpens up noticeably, banishing memories of the previous Z4 to history. The Sport Plus setting is particularly aggressive in terms of throttle response and gear selection.

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The best news though, is that the adaptive damping never turns the car into a denture-loosening mess; sure, it ramps up the firmness and body control in the Sport modes, but not at the expense of composure over rougher surfaces. This means you can still use the Z4’s performance to the full, even when not on a smooth road. In Comfort mode it’s relaxed, too, making for a good long-distance cruiser.

Last, but certainly not least, is that M Sport differential, a fully active unit, the operation of which is mapped to the driving modes. In Comfort mode, this attempts to keep the rear of the car stable at all times, while enhancing traction. It does that to a certain extent, though even so, if you’re clumsy with the throttle on the exit of a dusty or damp junction, there’s a momentary twitch from the rear, ensuring you know which end the power is being sent.

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On the move it’s never nervous, however, and it takes a little provocation to push beyond that initial movement, especially on dry tarmac. The differential allows for a more ‘dynamic’ stance on the exit of corners if you’re in one of the Sport modes, as you’d hope, and this reveals a delicious balance to the whole car.

You can really lean on the outside tyres and get on the power incredibly early, letting the differential do its thing. What’s more, on the approach to a corner and on initial turn-in, it can also help make the Z4 feel ‘pointy’, adding to the overall sense of agility. No doubt the variable sport steering adds to that, as it’s a variable assistance and ratio system.

Feedback isn’t bad, though would be better with a thinner steering wheel rim. The brake pedal is reassuringly firm, even after a spirited drive, allowing you confidently mete out as much braking force as you need.

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And confidence is a word we’d use to summarise the new BMW Z4 M40i. This is an incredibly polished product from the Germans, mixing quality with the latest interior technology and the usual desirability of a drop-top roadster with rear-wheel drive. BMW has managed to incorporate all of that while giving its new Z4 a chassis that is clearly developed with the enthusiast in mind. Especially so in the M40i.

Still want that Boxster?

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2019 BMW Z4 M40i SPECS:
Engine: 2998cc inline-6, DOHC, 24v, turbo
Power: 250kW @ 5000-6500rpm
Torque: 500Nm @ 1600-4500rpm
Weight: 1500kg (est)
0-100km/h: 4.6sec (claimed)
Price: $120,000 (est)

The Nemesis

Porsche 718 Boxster

2.0-litre turbo flat-4, RWD, 220kW/380Nm, 0-100km/h 4.7sec 1335kg, $119,960

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Down on power compared to the Z4 M40i (and its more expensive S sibling), the Boxster brings razor sharp handling to the topless battle and it’s every bit a driver’s car.