Can a power bump make the BMW Z4 a real Porsche-killer?

It’s easy to romanticise the convertible lifestyle. Sun-soaked weekend jaunts along the coast and whimsical Sunday afternoons frequenting wineries and eateries is the kind of existence a drop-top suggests.

Perceived elegance and luxury is part of the deal, one the BMW Z4 has traditionally pulled off with varying degrees of success.

Despite this, in our current context the G29 BMW Z4 M40i has two coupe-shaped thorns in its side.

On one hand the M2 Competition offers more performance for less, while the circa $45K cheaper Toyota Supra is essentially the Z4’s twin under the skin. The former is an M car ‘proper’, the latter has a cult following.

As part of the well-documented Toyota-BMW co-development, the Japanese quotient spawned a two-door coupe, while the latter morphed into a convertible.

The 3.0-litre inline six is a gem and its single-turbo application produces 285kW (5500-6500rpm) here, a 35kW increase over the version that launched in the G29 Z4 M40i in 2018. Torque remains unchanged at a hefty 500Nm (1600-4500rpm).

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Yet the Germans are renowned for under quoting power figures, so you’d be forgiven for thinking BMW is now merely quoting this B58’s power correctly. But you’d be wrong.

Not only does the M40i feel quicker by the seat of your pants, the go-fast Z4 now cracks the 100km/h sprint in 4.1 seconds – 0.4sec faster than Wheels achieved with the 250kW Z4 at COTY. That’s not hanging about.

It remains a wonderfully tractable engine, too, with the twin-scroll turbo spooling quicker than the new S58 in the X3/X4 M.

For those in the doldrums about the lack of a full-fat M version, this M40i is quick enough to be just enough of an antidote. That’s if you remember to press an important button – once. That’s the traction control, which engages M Dynamic Mode, unleashing the Z4 from the shackles of its electronic nannies.

Do that and the M40i’s 275-section Michelin Pilot Super Sport rear hoops offer up a controllable squirm under heavy loads both on corner exit and in a not-so-straight line.

Speaking of bends, the chassis loses little in rigidity over the Supra and there’s almost zero scuttle shake. However, the Z4’s softer suspension tune means it rolls more (especially from the rear) and it feels less agile when reaching for its limits. The steering also isn’t as quick.

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Dial back the tempo and the cabin is quiet with the fabric roof up or down, while there’s ample torque for lazy cross-country cruising.

The soundtrack is improved when topless, with the six-pot’s true tones outweighing the synthesized version played through the stereo.

The adaptive dampers offer just enough suppleness for poor surfaces and the ZF automatic glides through its eight ratios. The spacious cabin and 281-litre boot means that extended driving getaways are easily achievable.

Convertible two-seaters are made to look at, and Aussie designer Calvin Luk told Wheels that manipulating the kidney grille and moving the quad LEDs from a horizontal to a vertical position was a hard sell at HQ. Suffice to say, the Z4 isn’t a shrinking violet.

The interior is less polarising and is unchanged with the power update, meaning the latest iDrive infotainment system (with only Apple CarPlay) pairs with a 10.25-inch touchscreen. The instrument cluster is digital but none the better for it.

The Z4 M40i delivers a nuanced blend of old-school roadster appeal fused with a thoroughly modern execution. And in this 285kW tune, Bavaria has all-but created the Z4M it said would never see the light of day.

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2020 BMW Z4 M40i Pros & Cons

Plus: Purposeful straight-line performance; drop-top cruising; comfortable cabin

Minus: Price premium over Supra; slight deficit in dynamic focus; intrusive electronics

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The Rival: Porsche 718 Boxster - $121,490

The prospect of a Porsche and a $6500 fighting fund will be too much for some to resist, but you’re comparing a 2.0-litre 220kW four-pot in the Boxster to a 3.0- litre 285kW straight-six in the BMW.Not only is the Bavarian markedly faster, it’s also better equipped. It would take $182,590 worth of Boxster GTS to level with the Z4 M40i’s performance and equipment levels, but even then it’d be a very close thing. Couched in those terms, could the BMW be a bargain?

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