Diesel-electric XL1 ‘one-litre’ concept showcases VW’s ultra-frugal new powertrain
25 January 2011

Volkswagen is set to steal this week’s Qatar motor show with its latest ‘one-litre car’, the XL1 — a diesel hybrid concept that can deliver well in excess of 300mpg.

The new car is the third concept built to the vision of travelling 100km (62 miles) on a single litre of fuel. The first two vehicles, introduced in 2002 and 2009, used tandem seating, but the XL1 achieves the goal (or at 0.9l/100km, surpasses it) while looking remarkably conventional.

See official pics of the VW XL1 concept - updated with Qatar launch pics

The XL1 is powered by an 800cc, two-cylinder turbodiesel powerplant (half a BlueMotion engine), producing 47bhp. It’s supported by a 27bhp electric motor that is fuelled by lithium-ion batteries. These can be charged from a domestic plug, allowing the car to travel for 35km (22 miles) on electric power alone.

The electric motor can also be used to support the diesel engine’s torque during ‘full power’ acceleration, lifting the figure from 74lb ft to 103lb ft. But it also contributes to overall efficiency that’s well beyond that of regular production cars. The XL1 requires just 8bhp to maintain a constant speed of 62mph; by contrast, a Golf 1.6 TDI requires 18bhp to achieve the same feat.

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The result is a car that can return 313.9mpg and emit just 24g/km of CO2 — while being capable of a top speed of 100mph (electronically limited) and a 0-62mph time of 11.9sec. Despite having a relatively small 10-litre tank for diesel, the XL1 has a range of around 340 miles.

The XL1 uses a carbonfibre-reinforced polymer (CFRP) monocoque construction, helping it to weigh 795kg. Of this, 227kg is taken up by the drive unit, 153kg the running gear, 80kg equipment (including seats) and 105kg of electrics. The body is the final 230kg.

Read more on the earlier VW L1 concept

The car’s styling is more ‘normal’ than VW’s previous one-litre concepts, although it’s clearly designed for efficiency. It’s shorter than a Polo, at 3.9m, but lower than a Lamborghini Gallardo, at 1156mm. The profile is not unlike Honda’s original Insight. But the XL1’s drag coefficient is just 0.186.

The concept is not destined for direct production. But parts of its hybrid powertrain could be used on the next generation of eco models. The matter is said to have been the subject of intense debate within the VW Group in recent months, with VW itself favouring a stronger push towards diesel hybrids and Audi flagging up its Wankel-based range-extender technology.

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