What is it?
The BMW i8 is the second model from BMW’s new i brand. Driven here for the first time in prototype form, the low slung coupé is planned to go on sale in the UK next April at a price that will, BMW officials hint, pitch it into direct competition with the conspicuously more conventional Porsche 911 Carrera 4S, which retails here for £87,959.
A more extrovertly styled roadster version of the advanced hybrid, which boasts an official fuel consumption figure of over 113mpg and average CO2 emissions in hybrid mode of under 59g/km, is also under development at BMW’s Munich-based R&D centre, although it isn’t likely to see local showrooms until 2015.
Billed as a progressive sportscar, the i8 was first shown in concept car guise at the 2009 Frankfurt motor show. At the time, it ran a diesel-electric hybrid system. However, it has since made way for a petrol-electric set-up that shares various components, including its main electric motor, with the BMW i3’s exclusively electric driveline.
Like its smaller sibling, it can run in pure electric mode, but only for distances of up to 22 miles and a top speed of 75mph owing to its relatively small battery. Overall range promises to be quite spectacular thanks to a 42-litre fuel tank that is mounted underneath the rear seats. BMW is not prepared to make a figure official but it is already quite clear that the i8 will be among the most fuel efficient sportscars ever placed into production.
The i8’s styling has evolved during the four-year development phase, although the basic silhouette and flamboyant layered body design has been retained, giving the i8 a strikingly futuristic external appearance which is carried through to the snug two-plus-two interior. Length, width and height are put at 4689mm, 1942mm and 1293mm respectively, making it 449mm longer, 152mm wider and a scant 3mm taller than the second-generation BMW Z4 – a car against which the new BMW has been extensively benchmarked.
As with the i3, the i8 makes extensive use of carbonfibre and aluminium in a bid to offset the inherent weight of its advanced driveline. A so-called Life Module fashioned from carbonfibre forms the main structure, to which BMW has attached carbonfibre-framed doors and aluminum sub-frames both front and rear.
The outer body is a combination of carbonfibre (roof), aluminium (bonnet and outer door panels) and composite plastic (bumpers, fenders). BMW has also revealed the i8 will be the first production car to make use of Gorilla Glass – as seen on the latest smart phones. It is used for the rear window, providing added sound deadening properties for the interior.
A definitive figure is yet to be revealed, though the i8 is claimed to weigh less than 1490kg – undercutting the two seat Z4 sDrive35iS by 35kg despite providing accommodation for up to four adults (at a squeeze) along with 150 litres of luggage space underneath a liftback-style tailgate at the rear.
The primary form of propulsion for the i8 comes via a compact, turbocharged 1.5-litre three-cylinder petrol engine – the same B38 designated unit earmarked to head into a production version of the BMW Compact Active Tourer and third generation of the modern day Mini in 2014, albeit in a milder state of tune than the 2.0bar of turbocharger boost pressure used on the i8.
Mounted transversely behind the cabin, the aluminium block unit delivers an impressive 228bhp, giving it the highest specific output of any existing BMW engine at 152bhp/litre, along with 236lb ft of torque – all sent to the rear wheels via a six-speed automatic gearbox boasting a conventional torque converter.
The efforts of the compact petrol engine are supported by two electric motors, the larger of which is mounted up front within the front axle assembly, which is shared with that on the four-wheel drive BMW 650i xDrive. With 129bhp and 184lb ft of torque, the unit channels drive through a two-speed automatic gearbox.
The front electric motor is used to drive the front wheels during the start-up phase provided there is sufficient charge within the battery, a 5kWh lithium-ion unit that is housed within the centre tunnel, providing the i8 with zero local emission capability – something that will enable it to enter sidestep city charges like that in place in London. It also chimes in to boost performance in combination with the petrol engine, providing the i8 with four-wheel drive capability
There is also a smaller electric motor with 13bhp and 81lb ft sited at the rear next to the combustion engine. But while it is capable of providing additional drive to the rear wheels, it is principally used as a generator to top up the battery and alternatively as an alternator to collect and store kinetic energy during braking and periods of trailing throttle.
Interestingly, the rear electric motor is also used to smooth out delivery by providing direct drive to the rear wheels as the petrol engine is brought into the drive process. In doing so, BMW claims to have eliminated a slight dip in delivery due to typical turbocharger lag.
BMW quotes a combined 357bhp, endowing the carbonfibre intensive i8 with a power-to-weight ratio that betters that of the steel-bodied Z4 sDrive35i at 240bhp/tonne. Combined torque peaks at 420lb ft, some 44 per cent of which is available the moment you brush the throttle thanks to the inherent qualities of the electric motors.
As with the i3, the i8 receives three distinct driving modes: Comfort, Sport and Eco-Pro – all of which involve a combination of electric and petrol engine propulsion, albeit with different throttle, steering and damping mapping.
Underpinning BMW’s new age supercar is a largely aluminium chassis boasting double wishbones up front and a five link arrangement at the rear. The latter set-up is mounted directly to the aluminium sub-frame that supports the combustion engine and smaller of the electric motors. In keeping with BMW engineering philosophy, the new car boasts what the i8's project leader, Carsten Breitfeld, describes as a "near to perfect 50:50 weight distribution". The electro-mechanical steering system is borrowed from the X3, albeit with unique programming that aims to provide the i8 with sharper reactions.
The standard-fit wheels are aerodynamically optimised and measure 20 inches in diameter. They are 7.0 inches wide up front and 7.5 inches wide at the rear, shod with relatively narrow and high profile 195/50 and 215/45 tyres respectively. Buyers will be able to order more conventional 20in alloy wheels with wider 215/45 and 245/40 profile rubber – as fitted to the car i8 prototype we drove – for added grip.
What is it like?
Distinctly new world, both in appearance and driving character. You enter the BMW i8 through butterfly-style doors that hinge skywards from the front, opening to reveal a rather narrow aperture through which to climb. There is also a substantial carbonfibre sill to negotiate before you drop down into a high-backed driver’s seat, which boasts generous electronic adjustment.
It’s tricky getting in to, but the driving position of the i8 is pleasingly sporting, with a low-set seat squab, almost vertically mounted steering wheel and high centre tunnel that houses the battery. A push of a start button next to the gear lever triggers a chime to indicate the ignition has been tripped, at which a set of brilliant graphics, which alter in colour depending on the drive mode chosen, appear within the instrument panel – blue for E-drive and Eco-Pro, red for Comfort and Sport.
The default driving mode is Comfort, meaning the middle of the three hybrid settings. With sufficient battery charge, our first few hundred metres at the wheel of the i8 is achieved under electric power alone, with the front electric motor providing drive to the front wheels.
In its current state of development, there remains some whine from the electric motor, but otherwise refinement levels are spectacular. A touch more throttle nudges the speed up to 40mph, at which the petrol engine is triggered. It sends its drive to the rear wheels, instantly endowing the i8 with four-wheel drive capability.
The three-cylinder petrol engine does sound a bit gruff when it kicks into action. But once you’ve got it percolating above 4000rpm, the i8 emits a satisfying deep-chested thrum that becomes more sporting the closer you venture towards the 7000rpm cut out. The appealing acoustics aren’t all from the engine itself, though. As with the latest iteration of the M5, BMW has combined the actual sound of the engine with a synthetic sound generator to arrive at the desired result. They call it progress...
With the front electric motor and petrol engine providing drive to the front and rear wheels respectively, there is genuinely impressive acceleration in Sport mode, in which there is a noticeable change in character, with added throttle and steering response along with firmer damping for greater body control. The official acceleration claims – 0-62mph in 4.5sec and 50-75mph in 4.5sec – put the i8 on par with the outgoing BMW M3 for outright straightline pace. No slouch, then.
I drove the i8 on BMW’s Miramas test track in France. On the infield handling course and surrounding roads, it immediately dispelled any lingering doubts about its ability to deliver truly engaging driving traits. It is extremely agile, with somewhat light but extremely direct electro-mechanical steering. You can sense the low centre of gravity in the way the futuristic looking coupé enthusiastically turns in to corners. Its dynamic properties are characterised by an inherent responsiveness, nimbleness and light-footedness to the handling, which immediately stands out as one of the new car’s strengths.
There is very little body movement as lateral forces rise, although its ability to carry serious speed through corners is limited by the current state of chassis tune, which clearly favours understeer – something it tended to do quite early on the freshly laid bitumen of the BMW test track. It’s nothing too troubling, mind. But when the rest of the car is so well sorted, the deficiency in front-end bite tends to be magnified, and it quickly had the DSC (dynamic stability control) working as we began to push the i8 hard through corners.
BMW’s engineering team says the understeer is partly down to the characteristics of the specially developed Bridgestone Potenza tyres. They boast relatively soft side walls and are engineered to deliver low rolling resistance for maximum efficiency, even with the optional rubber. Still, this is an engineering mule, not a pre-production prototype, and predictably BMW says there are developments in the pipeline that will provide the definitive production version of the i8 with greater mid-corner purchase than the example we sampled.
The good news – no, the great news – is that you can dial back the threshold of the DSC and rely on it’s the prodigious torque developed by the front electric motor and combustion engine to kick out the tail in low-to-medium-speed corners, allowing you to straighten the line when conditions permit. So it is progressive, but there's also a good deal of adjustability in the chassis as well.
The automatic switching between pure electric and hybrid modes initially proved a distraction, but there is tremendous traction when all power sources are called up, allowing you to confidently lay the throttle back at the apex safe in the knowledge that drive is being sent both to the front and rear wheels. This leads to tremendous drive out of corners and, its safe to say, excellent all-season qualities.
Should I buy one?
I was worried the i8’s on-road ability would be compromised by its high-tech driveline and all the ancillary components that go with it – too complex, too heavy and skewed too much towards ultimate efficiency to make it much fun to drive. And after talking to the team responsible for its engineering, it seems as though BMW was quite concerned too – at least when they conceived the distinctly new-world coupé back in 2009.
That is why the German car maker has spent big on carbonfibre construction technology in a move that will see them bring the i8 to market early next year at a weight that undercuts many conventional two-door rivals at the scales and also endows it with the lowest centre of gravity of any existing BMW model. In doing so, it provides the basis for what is truly a landmark car.
After a brief stint in the thinly padded driver’s seat of this engineering mule, we’re confident the production i8 will live up to its billing as a sportscar. It is no track weapon – not in the traditional sense, at least. But it delivers the sort of response, directness and handling prowess that I’m sure will not only see it appeal to early adopters in search of something out of the ordinary but traditional driving enthusiasts as well. And nor does it lack for pace.
The i8 is an utterly intriguing, unreservedly fun and fantastically addictive car to drive, combining a multi-faceted drive system that is strong enough to propel it along at quite a furious pace together with engaging dynamic qualities that make it terrific fun on the track. And with a few tweaks to dial out that initial understeer, it promises to be even more exciting to pedal at the limit.
Porsche 911 Carrera 4S versus BMW i8 coupé? Old world versus new world. Expect it to be one of next year’s most anticipated comparison tests.
BMW i8 prototype
Price TBC; 0-62mph sub-4.5sec; Top speed 155mph; Top speed (electric) 75mph; Economy 113mpg; CO2 sub-59g/km; Unladen weight 1490kg; Engine inline three cylinder, 1499cc, turbocharged with synchronous electric motors Combined power 357bhp; Combined torque 420lb ft; Gearbox 6-spd automatic