Lamborghini Aventador J at 2012 Geneva motor show

There maybe other Italian sports car manufacturers looking to hog the limelight at the 2012 Geneva motor show (and Ferrari and its 730bhp F12 is one of them) but Lamborghini will vie for attention with the Aventador J. A two-seat, open top speedster based on the Aventador LP700-4, it has some intriguing bits of carbonfibre tech and highly individual design.

Named 'J' after the FIA’s Appendix J that governs the tech spec of race cars in certain classes, it’s proper bedroom wall material – but little boys and girls are unlikely to ever see it on the road as it’s a one-off and will go to a lucky owner after its appearance at Geneva.

To the Batmobile… let’s go! Yep, the Aventador J is a riot of polygons with a sharp, sweeping crease like an artist’s French curve extending from below the A-pillar (if there was one, because there are no pillars) through to the rear.

And it’s not just the roof and pillars that the Aventador has been relieved of, as there is no windscreen either… unless you count a tiddly pair of wind deflectors as a windscreen. Side windows are fixed and are so small they are almost imperceptible.

A brand new monocoque has been developed for the J, with two new safety bars behind the seats. This, combined with no roof, no traditional windscreen, no air con and no sat-nav means total weight is down to 1575kg.

The other bits of canny carbonfibre trickery include a new material developed by Automobili Lamborghini called Carbonskin. It’s a woven carbonfibre fabric soaked with an epoxy resin that helps keep the material soft but stable. It’s been shaped to the entire cockpit and has inserts in the seats. Lamborghini thinks it could end up in clothing. Very expensive clothing, no doubt.

The rest of the seats are made the same composites seen in the Sesto Elemento concept car shown at the 2010 Paris motor show. If you’re a golfer and have Calloway Diablo Octane ‘woods’, it’s the same material used by the American golf club manufacturer, who jointly developed it with Lamborghini. So, you can now take both for a drive. Sorry. Had to do that.

The rear view mirror. It’s mounted on what Lamborghini calls a periscope, thrusting up from the bonnet between the driver and passenger seats. Rather difficult to have a rear mirror when you’ve got no roof to suspend it from, you see. Here’s the solution. It rather looks like a roulette croupier’s shovel.

Powertrain wise, it has the 6.5-litre 691bhp V12 engine seen in its coupe sibling. And in an age when most engines are hidden underneath a plastic cover, the Aventador J makes a real play of the power unit. Here, the engine unit overtly displays both cylinder banks of the V12.

And the hue? It’s red. Specially developed for this project, it has a slight chrome effect. Could they be poking a finger into Maranello’s cage? Just saying. Also specially designed for the Aventador J are the five-spoke aluminium wheels. They get 20-inch rims at the front and 21s at the rear and have a carbonfibre insert which functions like a little fan to aid brake cooling.

If they still did I-Spy car spotting books, you’d get 10 million points from Big Chief I-Spy if you saw the Aventador J on the road.

By Stephen Worthy