Volkswagen's 70mpg Elise Killer

VOLKSWAGEN PLANS TO create an ultralight, mid-engined sports car, with the pace of a base 911 but the fuel economy of a Golf TDI.

The goal is to take the know-how from the carbonfibre XL1, the limited edition, cigar-shaped sensation that can cover 100km on just one litre of fuel (see box,right), and create a high-tech sports car that also raises the bar, but for handling and performance.

Insiders refer to the project as the XR1. It will adopt the XL1's basic architecture, which means a carbon-fibre reinforced polymer chassis with gullwing doors. Target kerbweight is 850kg - that's lighter than a Lotus Elise.

While the XL1 runs a 48bhp two-cylinder diesel complemented by a 27bhp electric motor, the XR1 could use the Golf GTI's turbocharged two-litre. The results would be explosive: 0-62mph faster than the 911 Carrera PDK's 4.6sec sprint, yet in excess of 70mpg - around one-third better than the GTI can manage. Top speed would touch 190mph.

The engineers will have to widen and lengthen the XL1 chassis, to accommodate the mid-mounted four, new twin-clutch gearbox and two seats abreast (they're offset in the XL1,to narrow the frontal area, reducing drag). While this will add weight, Volkswagen will save more than 100kg by ditching the hybrid eco-car's batteries and motor.

VW has yet to sign off the XR1, but insiders are talking positively. The XL1 was an impressive engineering showcase, but it'll be rarer than steak tartare. Turning it into the red-blooded XR1 - and selling it for £40,000 - would create a more populist halo car, one to make car enthusiasts giddy.

A New Suit

• VW's carbon supercar will be wider and longer than the XL1. Other key changes are the elimination of the rear wheelhouse fairings, and more curvaceous rear wings. 'The performance version loses a couple of points in the wind tunnel, but it looks a lot meaner,' says our insider.

Look, No Mirrors

• The XL1' s gullwing doors will be carried over. So too the rear-facing cameras that replace wing mirrors; VW is vowing to productionise this feature. It has a major aero benefit, reducing drag and wind noise, and supposedly costs 200 including the door-mounted relay screens. A conventional rear screen is being considered.

Some Cheap Bits

• Magnesium wheels, carbon-ceramic brakes, and polycarbonate sideglass cost too much for the XR1's £40,000 target price, so more conventional components will be used. Rims a modest 16- or 17-inches.

GTI Power

• Engineers are mulling over a turbo and supercharged triple, or maybe a hybrid, but the smart money is on the Golf GTI's turbocharged four being mid-mounted across the body. 'It looks the most promising option,'says our insider. 'It's barely bigger and heavier than a three.'

Fast And Frugal

• The exotic carbonfibre construction should peg kerbweight at 850kg. With 230bhp from the Golf GTI's engine, 0-62mph would take less than 4.6sec. Fuel consumption could touch 70mpg. Either way, a 911 Carrera would end up looking off the pace.