BMW i8 Spyder concept car (2012) first pictures

BMW will chop the top off the i8 hybrid at the 2012 Beijing auto show - and it's unveiled photos of its new i8 Spyder convertible supercar a few weeks ahead of the expo in China.

It's a sign that Munich will offer a convertible i8 alongside the tin-top coupe when BMW i8 sales kick off in 2014. This one sports a two-section folding roof, converting the i8 from coupe to roadster in a few seconds.

Tellingly, the i8 cabrio gives a few pointers to the likely format of the production cars. The Spyder has a slightly shorter wheelbase and overall length, suggesting that showroom i8s will be more compact than the concepts we've seen so far.

It keeps the 'swan' doors, though, swivelling upwards despite its cabrio silhouette. It's been enabled by the carbon-rich structure of the i8, which creates a very stiff structure. The passenger 'Life' cell is made from carbonfibre reinforced plastic (CFRP) while the 'Drive' platform underneath is made from aluminium. The lithium-ion battery is housed in the car's spine, helping give a low centre of gravity and BMW's preferred 50:50 weight distribution.

Like the i8 coupe, this car has a plug-in hybrid powertrain to produce supercar performance for claimed supermini emissions.

A 129bhp electric motor drives the front wheels, while a three-cylinder turbo petrol engine sends 220bhp to the back axle. Total system output is 349bhp and 406lb ft of torque. Which explains why BMW is quoting 0-62mph in 5.0sec and a limited 155mph top speed.

Yet the two-seater i8 Spyder is claimed to manage 94mpg on the European test cycle (although today's announcement doesn't say whether that's the combined total figure or an economy on the easier extra-urban cycle).

A domestic socket will charge up the lithium-ion battery in 'less than two hours', giving a 19-mile range on EV power. Naturally, the battery recharges on the go, every time you coast or cruise to a stop.

As its hybrid set-up dictates, the i8 is four-wheel. Also handy when it's cold is the way you can set the battery and cabin to be warmed up to operating temperature in advance on a cold day so it's snug and warm - and efficient - from the moment you jump in.

Click here for CAR's story on the BMW i8 production car twins.

By Tim Pollard