Volkswagen refers to the XL Sport concept vehicle that it revealed at the 2014 Paris Motor Show as a “sister model” of the XL1 (see http://articles.sae.org/12588/ and http://articles.sae.org/11874/). As with most siblings, some similarities are evident—but the differences can be striking.
First, the similarities. Like the XL1, the XL Sport is extremely aerodynamic. The performance car concept has a drag coefficient of 0.258 (vs. 0.189 for the XL1) and its frontal area is 1.7 m² (18.3 ft²). Design features contributing to cooling and downforce include air curtains that direct air in the frontal area into specific channels, wheel arch ventilation, an optimized underbody, lift-reducing air ducts in the hood, an extendible rear spoiler similar to that on the Lamborghini Aventador, and adaptive waste heat vents incorporated in the rear hatch that can open automatically to cool the drive unit.
Another shared attribute is a lightweight monocoque (albeit differently shaped) made largely of carbon-fiber-reinforced polymer (CFRP), featuring slightly offset driver and passenger seats. Both cars sport wing doors that extend into the roof and are hinged at two points—low on the A-pillars and just above the windshield—allowing them to swing upward and slightly forward. Door windows are made of polycarbonate, and the windshield is a special type of thin glass.
At 890 kg (1962 lb), the XL Sport weighs more than the XL1 [795 kg (1753 lb)]. The concept is longer and wider than the XL1, and also has an increased wheelbase (see chart for dimensions). Whereas the XL1 tapers toward the rear, the XL Sport maintains its width front to back. The sport concept inherits the XL1’s e-mirrors—cameras integrated in the doors that send images of the surroundings to two interior displays.
Now to the fun part: the differences. Most notable is the powertrain. Under the rear hatch of the XL Sport is what VW claims is the world’s most powerful two-cylinder engine: the Ducati 1199 Superleggera’s V2 engine. The 1199-cm³ DOHC powerplant generates 147 kW (197 hp) and 134 N·m (99 lb·ft), can propel the concept car to 270 km/h (168 mph), and revs to 11,000 rpm. The unit was slightly modified for use in the XL Sport, according to VW, but is basically the same as the motorcycle engine.
The Ducati engine’s high speeds are possible thanks to titanium connecting rods, its bore/stroke ratio of 112 mm (4.41 in)/60.8 mm (2.39 in), respectively, and the “exceptionally short” crankshaft stroke associated with it. The two four-valve cylinders are arranged 90° to each other and feature a desmodromic valve control system (positive valve closure) typical of high-revving Ducati engines. Other features include a magnesium-alloy clutch, cylinder head and oil pan covers, the two disks of the throttle valves, and the two injectors per cylinder.
The XL Sport’s newly developed intermediate gearbox reduces engine speeds by a factor of 1.86. Torque is transmitted to the rear axle via a seven-speed dual-clutch gearbox (DSG).
The car accelerates from 0-100 km/h (0-62 mph) in 5.7 s.
True to its moniker, the XL Sport gets a significantly redesigned, racing-inspired chassis incorporated in a high-strength steel spaceframe. Its double wishbone front axle sees the dampers connected below in a pull-rod configuration, and a double wishbone rear axle has the dampers connected above in a push-rod setup.
High-speed 205/40 R18 (front) and 265/35 R18 (rear) tires wrap forged magnesium wheels, which are reportedly 23.9 kg (52.7 lb) lighter than aluminum wheels combined. The brake system features ceramic discs.Continue reading »