BMW i8 Prototype 2013 Review - International

BMW chose a tough and brave battle for its i3 electric car. Launched into an unproven market at vast expense, the i3’s success or failure rests on a knife’s edge and not even BMW knows which way it will fall.

Not so the i8. Every bit as high tech as the i3, BMW’s i8 is the thinking man’s Porsche 911 (or M6), with four seats, ludicrous fuel economy and a sprint to 100km/h that slides beneath 4.5 seconds.

A combination of a plug-in hybrid powertrain, with the i3’s electric motor in charge (see what I did there?) of turning the front wheels and a 1.5-litre turbocharged petrol motor at the back, it’s every bit as sleek as it is clever. Aside from its see-through glass doors, it’s remained relatively true to the original concept car from 2009.

We drove the i8 in its final prototype form in Miramas, France, this week and BMW is already hinting strongly that it’s going to be priced directly on top of the 911 when it goes on sale in Europe early in 2015.

The final result -- so far -- is a car that is fast, distinctive-looking, aerodynamically sleek and capable of running for around 35km in its pure electric mode. That’s enough to get most people to work (and, for some, back home again) every day, so the nominal fuel economy figure of around 2.5L/100km is something they’ll easily be able to improve on.

And, unlike its city-based i3 stablemate, the i8’s hybrid drive system means it can dispel any range anxiety by being able to stretch its legs to over 500km between refills of its 42-litre petrol tank.

It can charge its lithium-ion battery pack (for pure electric drive) overnight on a conventional powerpoint, in less than an hour on a fast charger over lunch, or via using every spare kilowatt from the petrol engine.

It uses a detuned version (to protect the high-frequency charge-drain-charge hybrid batteries) of the i3’s 130kW electric motor, so it’s capable of delivering 97kW of power and 250Nm of torque to the front wheels.

At the back, sitting just ahead of the five-link rear axle, is a 170kW version of the B38 1.5-litre three-cylinder motor that is about to be BMW’s prolific small-car engine. Yet while it will also be seen in the MINI range and the upcoming 1 and 2 Series BMWs, none will have the i8’s 2.0bar of turbo boost, which gives this the highest specific output in the BMW range.

Combined, the two power units (which never physically meet up in any way) deliver a total system power of 266kW and 570Nm of torque, almost half of which is on tap instantly, thanks to the delivery characteristics of the electric motors.

BMW ties that together in an unusual piece of chassis architecture (as seems to be the norm at ‘i’), with an aluminium battery carrier, which runs down the middle of the car, forming the core of the structure. A carbon-fibre body module sits on top of that, then there are aluminium subframes at both ends to carry the engines and to hang the suspension from. The electro-mechanical steering comes directly from the X3 (though reprogrammed for a more direct response) and it uses BMW’s new two-stage damping philosophy, with Comfort and ECO PRO using the softer setting and Sport using the firmer one.

It rides on 195/50 R20 front wheels and 215/45 R20 rears, though BMW expects most people to opt for the larger 215/45s and 245/40s we had on the prototype.

Even with two motors instead of one, the i8 still weighs less than 1490kg and its curvaceous, multi-layered body will boast a Cx of 0.26 to make it the most aerodynamically efficient sports car on the market.

While the benchmark in most people’s minds will be the M6 or, for the faithful, the original M1, BMW has actively benchmarked the current Z4 in handling and attitude, and the i8 is half a school ruler wider, 449mm longer and just 3mm taller than the convertible. And it’s around 35kg lighter, even though it has four seats (nominally, anyway) and 150 litres of luggage space, behind the engine, beneath its liftback tailgate.

Overall, it’s 4689mm long, 1942mm wide at the mirrors and 1293mm high, all clad in a combination of aluminium and carbon panels. There is an aluminium bonnet and aluminium outer skin for the enormous, carbon-framed doors, while the roof is carbon-fibre and the enormous front and rear bumpers are single pieces of plastic. It also sees another innovation by using three layers of sandwiched Gorilla Glass, as used widely on smartphones and combat helicopters, to separate the cabin from the engine bay. The sheet of glass is light, impressively flexible and very absorbent for vibrations and noise.

That level of innovation carries over under the bonnet, where it will also be the most technically sophisticated BMW ever made, with incredibly complicated software to match the two different powertrains seamlessly in their responses to the driver’s throttle inputs.

One of its secrets is a high-voltage, 10kW electric motor connected via a belt drive to the petrol engine. This acts as both a starter motor when it’s in start-stop mode and, effectively, an electric ‘turbocharger’ to speed the petrol engine’s revs to match the instant delivery of the electric motor up front. It also acts as a generator and can punch another 110Nm of torque into driving the rear wheels, too.

The rear end’s power delivery relies on a six-speed automatic transmission, while the electric front end has a two-speed gearbox (though it only works in the bottom gear with its pure-electric mode).

BMW limits the torque delivery to the front end, though, because the electric motor is more than strong enough to spin up the front wheels on take off from the lights.

DRIVING
Don’t get into an i8 for the first time while you’re wearing a kilt. That would just be rude.

It isn’t an easy thing for first timers, with that enormous door hinging off the A-pillar and still not quite seeming to open wide enough. As large as it is, it doesn’t seem to leave you a lot of room to clamber over the wide sill and slither down into the driver’s seat. And getting into and out of the rear seat is even harder.

Even if you’re not tall, you’re going to have to leave the driver’s seat in the most rearward position if you want to re-enter the i8 with any dignity and without banging your head on the door, or the roof.

Once you’re in, the i8 feels slightly, anti-climactically normal. There is BMW’s traditional afterthought of a multi-media screen blocking out the obvious curves of the dash top. There is a steering wheel built for the rest of BMW’s sporting range, there is the same gear-shift lever for automatics, the same toggle switch for the driving modes and the same iDrive unit, too.

The seats are taut and thinly padded and the two-pedal arrangement is perfectly in line.

Push the start button and the i8 comes silently to life, which you only know via the colouring on the dashboard. It’s red if it’s in the default Comfort mode (also for Sport) and blue for ECO PRO.

And then it moves off, silently, in ECO PRO. In the drive program we had, we started in electric mode because i8 project manager, Dr Carsten Breitfeld, insists that’s how most people will drive it during the peak-hour drudgery.

And it’s incredibly sophisticated. There is some whine from the front end as the i8 moves off, but it’s more than quick enough for most traffic scenarios with just the front wheels cranking out torque and it’s free, too.

The silence gives us an easy chance to assess the rest of the i8, leaving the impression of a wonderfully calm machine. The ride is exquisite in Comfort mode and the seat has the driver sitting deep in the machine’s innards, with a roll centre some 20mm lower than the next best BMW (the 435i, in case you were wondering).

It surges forward seamlessly until it hits 65km/h, when the three-pot motor kicks in. It isn’t exactly a Ferrari V8 back there, and its awakening is accompanied by a gruff blurt and a slight pullback in performance as it spins up so that its contributions to the rear wheels match those from the electric motors already working away up front.

Even in ECO PRO and Comfort modes, you can make the petrol motor add its gravitas whenever you like by simply punching the accelerator through the détente at the bottom of its travel, much like you would to get an auto transmission to downshift.

While the three-pot isn’t a jewel at low rpm, it does sound far nicer when it’s up and spinning hard and from around 3500 revs to the limiter at 7000rpm, it’s a little charmer. A lot of that is due to the artificial sound generator BMW has pilfered from the M5, but the lack of harshness is at least genuine.

Besides the eco, there is genuine speed here when the i8 is flicked over to the Sport mode. Combined, the two powerplants hurl the sleek chassis to 100km/h at least as quickly as BMW claims and the prospect of even more to come out of the front electric motor (it’s 30kW down on the same unit in the i3) is incredibly tantalizing.

The petrol engine does more than provide mumbo and 320Nm of torque, though. It provides the driver with a baseline of aural effort that helps you to judge how hard you’re pushing the car and how quickly it’s being hustled.

And it can be hustled very quickly indeed. All the powertrain sophistication in the world wouldn’t work if the i8’s chassis was rubbish. It isn’t.

Its incredibly low centre of gravity and the way it contains all its greater masses inside its wheelbase lend it a low moment of inertia and very little body roll. It corners with a level of grip and controllability that leaves you believing any driver who throws one of these into the weeds will deserve their crash.

It’s astonishingly forgiving and very easy to generate speed mid-corner, and very communicative and delightfully fun.

It can carry stupid amounts of speed into corners, too, then it has the wheelbase to carry that speed all the way through, while the torque vectoring helps the front end avoid running wide on the exit.

The prototype chassis setup lent itself to ultimate understeer, though it arrives a long way into the handling envelope and will be tuned out as BMW develops the algorithms of its powertrains even further -- and stiffens the sidewalls of the low-longitudinal-resistance rubber a bit.

It won’t always be like this, BMW insists, and you can see how it can be fixed quite easily, with one way being to push the single button on the dash to turn off all the driving aids.

This allows you to throw the i8 harder into corners, to stamp on the power earlier and to watch as that layered rear bodywork drifts gently and controllably wide on the way out of corners.

That’s the good news for BMW. The car is good. The basics are all there. The final tying together of the last scraps of the work of the software boffins is all that really remains.

And it’s convincing in a way that the M6 isn’t. It has a future that will outlive standard fast cars.

And it doesn’t just provide a roadmap to future sportscar production, like a concept car or a Porsche 918. It provides a picture of future sportscar production that is already here.

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