BMW unveils i8 Spyder concept

i8 Spyder. Not the sound of a Wurzel expressing hatred for an arachnid, but BMW's roofless, two-seat hybrid concept.

It'll be unveiled at this year's Beijing auto show later this month and is, as you'd imagine, a pretty good sign that Munich's going to give us a drop-top to join the i8 coupe. For those hard of memory, that's the 155mph, 100mpg sportster due to land in showrooms come 2014.

See more pics of the BMW i8 Spyder

The i8 Spyder concept is a little stinted compared to its coupe brother, though. Under the two-section folding roof it's slightly shorter and there's a more compact wheelbase, suggesting its original proportions - based on the splendid Vision EffecientDynamics supercar of 2009 - have been rethunk. 

BMW has kept the swan doors, which swivel up like the wings of a, umm, swan... They're retained thanks to the amount of carbon that's used in the i8's super-stiff passenger ‘Life' cell, which is made from carbonfibre reinforced plastic (CFRP).

Underneath, there's an aluminium chassis with a lithium-ion battery buttered along its length, keeping the centre of gravity nice and low and achieving a 50:50 weight distribution. It's got the same plug-in powertrain as the coupe, too; a petro-electro melange of 129bhp electric motor driving the front wheels and three-cylinder turbo petrol engine sending 220bhp to the rears (that's 349bhp in all).

See more pics of the BMW i8 Spyder

All together, it makes 406lb ft of torque, which gets it from 0-62mph in 5.0 seconds and a tethered top speed of 155mph. And it's claimed it can do 20 miles of FWD on the battery alone. 

Unlike the 100mpg coupe, the convertible only claims a piffling 94mpg, but charge time on a domestic socket is impressive; BMW says it would be "less than two hours". It'll do 19 miles on EV power alone, and the batteries are charged up when you coast, cruise and stop.

There are, as you'd imagine, some spurious concepty add-ons. Also included are a pair of electric scooters housed under a transparent tailgate, a camera-based proactive collision warning feature, and the interior can be pre-warmed on a cold morning so it's all toasty and warm when you go to drive it. 

But still, look at it. This is definitely a vision of the future we like. Your thoughts on the arachnid-hating Wurzel of tomorrow, TopGear.communists?

And you can read about its slightly smaller twin brother, the i3, right here

UPDATE: BMW has now released footage of the i8 Spyder in action - watch it here: