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Traditionalists may not like it, but the latest four-cylinder additions to the Z4 line-up effectively signal the end of BMW’s famous normally aspirated six-cylinder.
BMW might produce what many believe to be the ultimate driving machines, but these days, it’s as much about efficiency as it is about performance, and downsizing is the name of the game.
So here are two new versions of its highly distinctive rear-wheel drive BMW Z4 coupe-convertible, the Z4 sDrive 20i and the Z4 sDrive28i. Both variants are powered by smaller turbocharged engines, which are substantially more fuel efficient and kinder to the environment.
With the Z4 sDrive28i, BMW has moved from a 3.0-litre naturally aspirated six-cylinder engine that was the sDrive30i, down to what is essentially a tuned version of its new 2.0-litre four-cylinder turbocharged engine.
It’s the same formula with the new entry-level BMW Z4 sDrive20i, which replaces the 2.5-litre sDrive23i. The smaller 2.0-litre powertrain is known as the N20, and is a new generation of four-cylinder petrol engine from the car maker. It uses the latest technology such as Turbo Valvetronic direct injection (TVDI) with a twin-scroll exhaust turbocharger and will gradually replace existing four-cylinder engines as well as the six-cylinder naturally aspirated engines.
In both cases, the new 2.0-litre powertrains are down on power, but up on torque, compared with the outgoing Z4 variants (Z4 sDrive23i – 150kW / 250Nm to Z4 sDrive20i – 135kW / 270Nm. Z4 sDrive30i – 190kW / 310Nm to 180kW / 350Nm).
Straight-line acceleration with the new Z4 variants is either remarkably close to the outgoing cars, or, in the case of the sDrive28i, better, by a fraction of a second. The Z4 sDrive28i will sprint from 0-100km/h in 5.7 seconds, while the Z4 sDrive20i does it in 6.9 seconds.
Firing up the new Z4 sDrive28i instantly reveals a throaty like exhaust note, while a decent prod of the throttle means that you’ve got all 350 Newton-metres on-song from 1250rpm through to 4800rpm.
The standard fit transmission is a rather notchy six-speed short throw unit, but our test car was fitted with the optional 8-speed automatic transmission with steering wheel mounted paddles (thankfully, now unidirectional), allowing for rapid-fire shifts up or down the ratio range. It’s not a double clutch box, but when your pushing hard and hitting anywhere near the unusually high 7000rpm redline, gear changes seem almost as quick. It’s a $3,500 option, but well worth the expense considering the car's price/performance advantage over its closest competitors.
Going from six-cylinders down to four-cylinders obviously reduces the weight over the front end, and you can certainly notice the difference on the more twisty roads, but at the end of the day, it’s only 15 kilograms.
Performance wise, drivers can select one of three dynamic settings on board the Z4 - Comfort, Sport and Sport +. You’ll want to shift into ‘Sport’ mode, the moment you come across a quiet bendy stretch of tarmac. The difference is immediately obvious; providing more weight in the steering, faster throttle response and quicker shift times with the automatic transmission.
In-gear acceleration in third or fourth gear at between 3000-5000rpm is particularly strong, while the exhaust note turns decidedly ‘snarly’ at that point. Enthusiasts will also enjoy the turbo boost ‘blow off’ sound every time you punch the throttle and back off slightly. So called’ turbo lag’ is minimal with these new powertrains, it’s fractional, at worst.
As good as this car is in the performance department, it’s even harder to fault the ride and handling set up. It doesn’t seem to matter how hard you push the Z4 sDrive28i through these twisty bends, the car always feels planted and composed. That’s despite some rather appalling road surfaces we experienced on the drive route.
It’s even more impressive when you learn that BMW engineers perform absolutely no additional suspension calibration for markets outside of Germany on their vehicles, with the exception of their ‘M’ cars, which get a different set up entirely.
It’s that almost perfect balance between rock solid handling and ride comfort that makes this car such a joy to drive - especially around corners. Despite the fact the Z4 has a high torsional rigidity count, there’s a comfortable level of pliancy in the suspension that provides an almost supply ride, even over patchwork roads.
I’m not so fond of the standard fit seats in the new Z4 variants though. There’s not enough side bolster to hold your torso in- place during tight cornering. Enthusiast buyers would be well advised to look at the optional ‘BMW Sports seats’ for $1300, or they’re included in the ‘M Sport Package’. These sports pews are aggressively bolstered and mandatory for those quiet bendy roads on an early Sunday morning.
Hoping into the Z4 sDrive20i isn’t really a huge step down from a driveability standpoint. After all, it’s essentially the same turbocharged 4-cylinder engine albeit with unique engine mapping and slightly more turbo boost pressure.
Plant your right foot, and off the line acceleration is certainly swift, but you’ll definitely notice the drop in mid-range grunt due to the loss of 80Nm on the more powerfully tuned sDrive28i variant. That said we are yet to test the Z4 sDrive20i with the eight-speed auto, which could easily end up the pick of the model range when you take into account its price/performance proposition.
I would also stick with the stock suspension set up too, as our test car was fitted with the optional ‘Adaptive M suspension’ which in this case, made the Z4 feel nervous and less composed on poorly maintained roads.
Once in ‘Sport’ mode though, the additional weight in the steering, along with the high level of communication this car translates through the steering wheel itself, inspires enormous confidence to fully exploit the Z4’s superb handling ability.
BMW have taken a bold step with downsizing engine displacement in their sports cars, in the quest for ‘Efficient- Dynamics’ and these new Z4 variants are testament to the success of those goals.
Not only is the sDrive28i quicker than the Z4 sDrive30i that it replaces, but also fuel consumption has been reduced by up to 21 per cent, from 8.5 litres per 100 km to 6.7 litres. Importantly, this positions the new Z4 below the federal government’s fuel-efficient luxury car tax threshold, meaning lower price points.
Whereas the previous Z4 sDrive30i was $98,700 the entry price for the Z4 sDrive28i is $89,400.
It’s even more compelling with the Z4 sDrive20i, at least from an all-round perspective. Although it gives away little in the way of performance to older sDrive23i, fuel consumption falls by 1.8 litres to 6.7 litres per 100 km.
BMW’s new additions to the Z4 line-up offer reduced prices, reduced fuel consumption and reduced CO2 emissions. One thing they haven’t reduced is the serious fun factor associated with a front engine, rear-wheel drive drop top; there are still loads of that stuff on offer.