Volkswagen XL1: driving the technology

  • 05-Dec-2013 02:13 EST
VWXL1    6.jpg

Volkswagen's XL1 can be driven quickly and confidently in the wet.

“We have seen a best average fuel consumption in hybrid mode of 0.7 L/100 km from the car,” said Volkswagen Technical Specialist Steve Harris, suggesting that this AEI editor’s pedal-to-the-carbon-fiber exit from a roundabout was not really the salient design aspect of the VW XL1.

Maybe; but what is arguably the world’s most extraordinary production car does so with aplomb, demonstrating that even such an extreme solution to the successful pursuit of über-economy can be a highly enjoyable and practical driving experience. VW bills it as the “most efficient car in the world.”

AEI is not a publication that would normally embrace road impressions of a vehicle; it is globally renowned for its presentation of facts: revealing, describing, reporting, and analyzing worldwide automotive technology with the emphasis on absolute accuracy and impartiality. But very occasionally a vehicle will be presented by an OEM that represents such a step-change in transport that an added dimension is required; as a technological tour de force, the XL1 is a very rare example.

Although previously described by AEI in fine detail, covering everything from conception to production (now running at two a week for a total 250 units, 200 of which will be for sale or lease to customers at €110,000 a copy), the vital element of the whole concept concerns practicality, ease of operation, and satisfactory drivability.

Entering the 1153 mm (45.4 in) tall XL1 via an upward swinging, almost scissor-type door, calls for a minor degree of athleticism over a wide sill, but is helped by a steering wheel with flattened lower circumference. Control for the seven-speed automated-manual DSG (direct shift gearbox) with regular (D) and sport (S) modes comes easily to hand.

Instrumentation is basic but adequate. A small Garmin screen provides information reminding the driver if power is coming from the XL1’s 35-kW (47-hp) two-cylinder 0.8-L diesel TDI engine, its 20-kW electric motor, or a combination of both. It also indicates if the car is coasting or putting energy back into the system, mainly via regenerative braking, although in S mode on the overrun the battery receives some energy. Maximum pure EV range is 50 km (31 mi) and more than 10 times that if the diesel’s capability is added.

Sitting next to the driver on a seat positioned slightly aft to provide added elbow room, Harris underlined that as well as its ultra-parsimony, it also had—to use a decidedly nontechnical phrase now beloved by many OEM designers and engineers—a “fun factor.”

The XL1 was sampled on the UK’s unforgiving roads, which provided a plethora of surface treatments, potholes, lateral ridges, mini-roundabouts, narrow rural lanes, and high-speed motorways, in weather that included a heavy downpour of rain and gusty wind. No particular attention was paid to economy driving and maximum acceleration was used often; headlights, wipers, and air conditioning were in almost constant use. It was the sort of treatment a regular car would experience.

But driven like that, real-world fuel consumption could still average around 1.3 L/100 km; the official figure is 0.9 L/100 km.

“It’s quite a narrow car—about as wide as a VW Polo,” Harris reminded this editor as the XL1, driven in pure EV mode, accelerated to join the traffic flow on a dual carriageway in Milton Keynes, site of VW’s UK HQ. “If you need more power, just floor the accelerator.”

That done, the little mid-engine diesel took less than two seconds to respond, making a curious staccato clacking sound that Harris said had been compared to a general aviation engine. Others may be less complimentary.

“A reminder that this car has no interior or exterior mirrors, but rear-facing cameras (e-mirrors) that give very good coverage except for the area immediately behind the car,” warned Harris. Images are received on small screens positioned fairly low on the door. They are wide-angle and cover potential blind-spots along the vehicle’s flanks, but could usefully be larger and placed higher, although confidence in their efficacy is quickly gained. Lack of regular exterior mirrors makes a significant contribution to the car’s ultra-low aerodynamic drag coefficient (Cd) of 0.189. Visibility through its steeply sloping windshield and polycarbonate side windows is good. A-pillars are very slim.

The 0-100 km/h (0-62 mph) time for the XL1 is 12.7 s and top speed is limited to 159 km/h (99 mph), which may seem modest but is totally adequate.

“Coasting efficiency is greatly enhanced in the XL1 through the use of large diameter but narrow magnesium wheels—the fronts weighing 3.16 kg (6.97 lb), the rear 3.71 kg (8.18 lb)—fitted with low rolling resistance Michelin tires. From higher speeds—above about 80 km/h (50 mph)—coasting also benefits from the car’s aerodynamic efficiency.

Suspension is double wishbone and incorporates ZF motorsport-type dampers. For a car that has an unladen mass of only 795 kg (1753 lb), the ride is generally good, although some potholes and lateral ridges cause jarring and thumping through the car’s very stiff—more than 30,000 N·m (22,100 lb·ft) per degree—carbon-fiber shell.

Roadholding was confident and handling adroit on streaming wet road surfaces. The unpowered steering is direct and light, even with some loading-up in tight corners.

Ceramic brakes are fitted to save weight; they feel rather dead and create some noise. “You can just dip the brake pedal without applying the brakes to get an energy recuperation signal,” said Harris.

Also to save weight, there is little sound insulation material in the car, which at times makes it seem almost like a prototype, which it certainly is not.

Passing through a village in pure EV mode creates a mild whirr in the car but there is no exterior noise generator, which it arguably needs for safety reasons.

Out of the village, and up a hill in the DSG’s S-mode, demonstrated the car’s reasonably brisk performance, with energy regeneration achieved on the subsequent downgrade (D mode does not provide this, stated Harris).

Although no sports car, the XL1 does indeed have a “fun factor.” Rapidly exiting the roundabout that prompted Harris’s comment on the car’s fuel economy potential, a following Audi A4 cabriolet shrank in the rear-view screens. It appeared again only as the XL1 settled to an indicated 120-km/h (75-mph) cruise.

Determined to overtake, as he did so the Audi driver glanced sideways with amazement and disbelief at the extraordinary little machine, scuttling along so quickly and confidently, that may represent an embryo of future automotive engineering and technology.

Volkswagen has indicated that a motorsport version of the XL1 powered by a 1.2-L Ducati superbike engine is being considered; “fun factor” would be standard.

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