Such was the effort deployed to keep the drag coefficient low that VW’s super-computers spent whole weekends cranking out simulations.
The upshot is just delectable – a sort of 50th percentile supercar, immaculately surfaced and detailed. Its Cd is just 0.186, 2.5 times lower than a contemporary Golf and better even than its conceptual predecessors.
However, in the efforts to build a much more serious and safe machine, the XL1 tips the scales at 795kg - virtually the same as a Mk1 Golf.
What’s it like?
When you stand next to the XL1, it looks impossibly small and it’s hard to imagine it swallowing two full-size adults. Even when the gullwing doors swing open, it doesn’t look promising. However, it is pretty easy to get into, despite the combination of the wide carbonfibre sill and very low (carbon-shell) seat. It then takes just a few seconds to realise that this is fantastically well planned interior, with a superb, slightly laid-back driving position.
Despite sitting so low and the fact that the A-pillar partly snakes across in front of the driver, the view forward out of the car is superb. The staggered seat position – the passenger sits further back than the driver – is inspired. Really, the cabin doesn’t feel cramped; it feels positively spacious.
The interior – much of the structure is made from “natural fibre” – is beautifully conceived and immaculately styled, from the tiny, flat-bottomed steering wheel to the shift lever. Indeed, the whole cabin – which weighs just 80kg – feels properly fettled and close to production quality. The digital rear-view mirrors – which have iPod-style screens let into the door skins – are a major advance.
The XL1 starts off silently via the battery and 26bhp electric motor (the combination has a range of 22 miles). Call up some acceleration and the 47bhp twin-pot engine fires up, initially, without the driver noticing, via the ‘pulse starting’ technique (this uses the electric motor to spin the diesel engine up to speed). However, once the combustion starts, the cabin is filled with a very odd metallic thrum from engine, which is mounted hard up against the rear bulkhead. But that, and the occasional resonance that’s generated by vibration through the hollow sections of the carbon tub, are all things that will be refined away over the expected 24-month pre-production development period.
Despite having such narrow tyres (115/80s on 15in front wheels and 145/55s on the 16in rear wheels, which are made of magnesium) the XL1 didn’t understeer around the Doha roundabouts and the steering is nicely weighted and accurate. The lack of a brake booster was alarming, though, especially as the car can put on a reasonable turn of speed. Shifts from the seven-speed DSG ’box were also hardly noticeable.
During the urban driving cycle I sampled, it was surprising how little the engine came into play. But that’s part of the strategy, because the slippery, low-friction XL1 requires just 8bhp to maintain a steady 60mph cruise.
Should I buy one?
Because this is a concept, you can’t. But much of the technology in the XL1 will start to migrate into mainstream VW models by the end of the decade and it will be inspiring to see a short-run series production version of the car on the roads in 2013. After experiencing the sense of drama involved in piloting this extraordinary little car, my advice to VW would be simple. Consider fitting the punchy VW 1.4 TSI engine in XL1’s rear end and create the world’s first truly green supercar.
Price: £30k-£100k; 0-62mph: 11.9sec; Top speed: 99mph; Economy: 313mpg (combined); CO2 emissions: 24g/km; Kerb weight: 795kg; Drag coefficient: 0.186; Engine layout: 2 cyls in line, 800cc, turbodiesel, plus 5kWh plug-in electric assist; Installation: Mid, transverse, RWD; Power: 47bhp (diesel), 26bhp (electric); Torque: 103lb ft (combined); Gearbox: 7-spd dual-clutch auto