Road Test: BMW I8 2dr Auto

Can this really be the i8 on the road at last? Feels like the longest tease in history.

Yes, the first concept car was at the Frankfurt show in 2009. Since then it's felt like a tease because the i8 has been growing up in public - in fact, the development period was remarkably brief by industry standards. There have been more concepts, and we've had development rides and prototype drives and various static launch jamborees. That's because BMW has felt the need to get the i brand established, and even more to get us used to the idea of a new sort of BMW. A new sort of sports car.

How new? Remind me.

About as far from the usual BMW template as you can get. The i8 has a 1.5-litre turbo three-cylinder engine mounted transversely ahead of the rear wheels. Tiny but mighty, this little triple makes 231bhp and drives only the rear wheels. The front wheels have a 131bhp electric motor. Down the spine is a plug-in battery big enough to power the front wheels for about 15 all-electric miles in gentle town driving. It'll do that on two hours' charge. The battery and motor are technology borrowed from the i3 electric hatchback, although different outputs. After the battery is flat, or when you need more power, the petrol engine starts, giving you a 4WD hybrid.

The main tub is carbon-fibre - again the same sort of newly developed stuff they've used on the i3. The subframes aluminium, the exterior panels (and my how revolutionary they look) are thermoplastic, except the roof which is moulded out of recycled carbonfibre offcuts. Even the glass in the doors and rear is half the weight of the normal stuff. It's the hardened, thin 'gorilla glass' used on phone screens.

What's the exact point of all this complication and novelty?

Efficiency. The aim is to make a car that'll operate all-electrically in the new era when some cities are banning or tolling combustion cars. And even in the hybrid and sports modes, even if you never plug it in, it'll go about 30-50 percent further on a gallon than other cars of similar performance: we're talking 0-62 in 4.4 sec. And because plug-in energy isn't counted in the European fuel cycle, it registers an official figure of 135mpg and 49g/km CO2. It gets the £5000 Government plug-in grant, is exempt from the London congestion charge and worms its way out of road tax. And if it's a company car you'll pay somewhere not far shy of £10,000 less personal tax per year than a 911.

Thanks to all that obsessive lightweighting, it's just 1465kg, even though it's got nearly 98kg of battery aboard, and another 100kg of power electronics and e-motors. There's a second motor, which acts as a starter/alternator for the petrol engine, and more interestingly develops a pulse of torque that covers the hole while the turbo spools up. Wringing all that power out of a 1.5-litre engine required a far bigger puffer than on the same engine in a Mini Cooper, and that'd normally lead to endless laaaaaaag.

Weight affects consumption when you're accelerating or climbing, but drag matters at steady speed. To eke out the energy, the tyres are low-resistance jobs, and have a narrow but tall shape to cut drag. The body is obsessively low-drag, with a Cd of 0.26 and a low frontal area.

Is that why it looks so whizzy?

Partly. Of course a low-drag car can be boring-looking (see the Prius) but this one goes further and some of the wind-cheating solutions, like the shape over and behind the rear wheels, and the layered skins to adhere air to the surface, look very Thunderbirds. Besides, BMW wanted to make a statement here. See it among traffic and it really does seem like an escaped concept car. From most angles it's dramatically beautiful, even if some of the multi-colour schemes are a bit too much of an eyeful. We'd go for dark grey on black, without the blue striping, and let the shape speak for itself.

So it actually work as a sports car?

For the most part, like a charm. In sports mode, using the paddle shifters, it disguises its hybridness entirely. It'll leap ahead with lag that's barely perceptible. Honestly it does an amazing impression of a 340bhp big six, rather than a 231bhp little triple. In sport mode some of the engine's natural frequencies are amplified through the hi-fi, and it's a strong, gutteral sound. The real pity is it doesn't rev beyond 6500, and for some reason its shifts up by itself on the red-line, even if you're in manual mode.

Even when the battery is pretty much depleted, by the way, you still get all the power of petrol plus electric. Remember, you never drive any car flat-out all the time, and so in the i8 (and any other hybrid), when all the engine's power isn't needed, spare is syphoned off to charge the battery just enough that for the next squirt of acceleration you can have the full petrol-plus-electric beans.

Is it 911 fast? Doesn't feel quite at that level. You don't get the high-rev drama or violence. But it's ruddy quick, be in no doubt. I believe the 4.4sec 0-62mph claim, because traction's so good.

But I'm worried about cornering, what with the mashup of different power sources for different axles.

Ah yes. Well, go into most corners and your doubts will be vaporised. It's wonderful. There's barely any roll, the steering is terrific, and there' a wonderful agility - it'll take left-right-left flicks like a lizard. In longer bends you can come on and off the throttle and tuck the nose in a little, or edge the tail out very slightly under power. It feels consistent and confident. Lovely.

Very long, slow, second-gear corners can trip it up though. If you go in too fast or under brake, and get understeer, the i8 seems to get a little confused and won't let you have full power for an annoying interlude. But if you get your entry speed right, then get early on the power, it feels just fine. I think there might still be a front-rear calibration issue in second gear, too. But what do I know - this is such a brainy car you never really know how it's doing what it's doing.

Er, calibration? Explanation please.

The engineers say the hardest job on the i8 wasn't the new materials or the weight or body. It wasn't even the power units per se. It was getting them to work together, getting everything smooth and maintaining the right variable torque split in corners. Imagine, you change throttle position. The petrol engine reacts, but with a bit of a delay as turbos do. So the electric front motor, and the auxiliary rear motor, have to be controlled to match that transient state, while maintaining the target front-rear torque split to keep the cornering dynamics right. Whatever of the six gears the petrol engine is in. However much grip each wheel has. Mind boggling.

Best not to think too hard. Just to let it get on with it, and enjoy the results, which except in that one tight-bend understeer situation, are fine. Anyway, the engineers say they're still working on a stickier front tyre compound, which should help too.

Ah yes, tyres. Aren't they a bit skinny?

Yes, they're narrow to save weight and drag. But they're tall, so the contact patch is longer than in a normal sports car, so overall there's enough tread on the road. That's with the optional tyres as on the photo car. The engineers admit the standard tyres don't give as much lateral g.

So does it cling on like a 911?

Not quite, but close. I found the limit easy to reach. But then that wasn't because it's a low limit, more that the car is confident and friendly and generally transparent as it gets there. And given the complexity that's remarkable.

How's the chassis itself?

Brilliant actually. The fundamentals are present: a very low C of G, all significant mass inside the wheelbase, and 53 percent on the rear, plus a palpably stiff body. You sit low, so you feel little rock or pitch. The steering is spot-on in ratio and progression, and gives you a good feel for the tyres' effort. Springing is beautifully judged, supple enough to be acceptable in grumpy urban running, but firm enough for the dampers to stick their teeth into when you're pressing on. In twisty and bumpy sections taken fast, there's no float to speak of and the dampers check body motions with terrific resolve, and yet they don't make things harsh when you're wafting. They're adaptive, but feel very natural. There's also remarkably little tyre roar, thanks probably to their narrowness, which adds to the refinement and matters a lot in electric running when there's no engine noise to drown the tyres out.

Electric mode you say?

You can select whether to use up the mains charge straight away, or save it for when you get to a town. As a pure EV the i8 is pretty good, though not as fast as an i3 as the motor is less powerful. But it's smooth and capable, probably as accelerative as a base-model supermini, and can do 75mph in all-electric mode. Going gently, 15 miles is easily possible on the battery. If you want more acceleration or speed, just kick-down the throttle and the engine cuts in to lend a (strong) hand. Only the brakes give it away: the mixing between regen and friction gives a grabby pedal at low speed. Again, the i3 is much better at this.

Will it do hybrid?

Yup, that's the normal 'comfort' mode. The engine cuts in and out, but it's not too obtrusive because it doesn't have the amplification that it has in sport mode. That said, there can be occasional pauses if the system thinks you don't want much power and you suddenly do, and it has to clear its throat, start the engine and change gear.

Sport mode is what it says: for quick driving. The engine always runs so it's always tensed and ready, and the car uses the electric system for regen so as to be sure the battery gets enough charge to ensure the full electric-augmented 362bhp is always under your toe.

I still don't believe the official economy numbers. Fess up, what did you actually get?

Er, about 24mpg on a fairly long day. But some context. There was some town running to begin with, and I did that at pretty much infinity mpg, because it was all electric. Then it was up into the mountains, where it fell to 19mpg. I really think other sports cars this quick would have been sub-20 for the town bit and low-teens for the mountains, given it was so heavy on second gear hairpins. My route took in barely any A-road cruising and just five or so miles of motorway. At steady speeds, the i8's small engine and its low drag would definitely help economy.

I can well believe it would go 30-50 per cent further on a gallon than rivals if you never plugged it in. If you always plugged it in and just did short commutes you'd never use any fuel at all. Somewhere between those usage extremes lies the 135mpg of the official test.

OK so it's economical in everyday running. Is it useable?

Pretty much. The rear seats are strictly for kiddies, but the front is habitable and comfortable. There's a bit of a boot under the rear hatch, but you'd end up using the rear seats for bags on a weekend away for two. The doors are a bit of an issue: sure they add theatre, but what with the high sills it makes getting in and especially getting out into a bit of a ballet. I wouldn't like to do it in a skirt (even were I female). And they have no storage pockets, and there are no front cup-holders. Porsche wouldn't make those mistakes. But a Porsche is a well-engineered ordinary car: the i8 is from another planet, or another era, and that's it's appeal.

So was this re-invention of the car worthwhile?

Well, it costs £95k after the Government grant, and a 350bhp 911 Carrera 4 PDK is £80k if vastly more tax-heavy. Now, was it worth all this BMW brainpower and new tech to make a car slightly less sporty than the Porsche that uses rather less fuel? That's a very dull question. For a start the 911 is 50 years into its development; the i8 is a first stab. I suspect different tyres and a firmware flash will soon improve it. But more than that, the i8 is exploring the future. It bestows lightweight construction, hybrid expertise, and a quick-thinking highly creative engineering mentality onto the whole BMW group.

It's an enormously satisfying thing to drive, because if you're thinking about it you can use its different characteristics in different ways to suit the moment - in fact it's at its very best either wafting in pure-EV mode, or being thrashed in sport mode.

And it makes everyone point and smile.