At the dawn of the millennium, Prof. Dr. Ferdinand Piëch, who is today Chairman of the Supervisory Board of Volkswagen AG, set his sights on creating a practical everyday use production car with a fuel consumption of 1.0 liter per 100 km (235 mpg). In 2002 a prototype VW 1-Litre was unveiled, which was followed in 2009 by the second-generation model, dubbed the L1, which boasted a combined diesel fuel consumption figure of 1.38-liter/100 km (170 mpg). As impressive as that figure is, the company has now managed to squeeze a combined fuel consumption of just 0.9-liter/100 km (261 mpg) with its third-generation VW 1-Litre prototype – the XL1.
With a combined fuel consumption of just 0.9-liter/100 km and CO2 emissions of 24 g/km, VW is calling the XL1 is the most efficient car in the world. This is achieved through a combination of lightweight construction using monocoque and add-on parts made of carbon fiber, very low aerodynamic drag (Cd 0.186) and a plug-in hybrid system consisting of a two cylinder TDI engine (35 kW/48 PS), E-motor (20 kW/27 PS), 7-speed dual clutch transmission (DSG) and lithium ion battery.
The entire hybrid unit is housed above the vehicle’s driven rear axel, with the actual hybrid module with electric motor and clutch positioned between the TDI and the 7-speed DSG. Instead of the usual flywheel, the hybrid module is integrated in the DSG transmission case. The vehicle’s lithium-ion battery can also be recharged from a conventional household outlet.
In electric only mode the TDI is decoupled from the drivetrain by disengaging a clutch, and it is shut down. Meanwhile, the clutch on the gearbox side remains closed, so the DSG is fully engaged with the electric motor. Using what is known as “pulse starting”, VW says the restarting of the TDI while driving is very smooth. The electric motor’s rotor is sped up and quickly coupled to the engine clutch, which accelerates the TDI to the required speed and starts it.
Under certain conditions the load shared between the TDI engine and the electric motor can be shifted so that the turbodiesel is operating at its optimum efficiency level. Additionally, the gears of the automatically shifting 7-speed DSG are also always selected with the aim of minimizing energy usage with the engine controller taking into account parameters such as the accelerator pedal position and engine load, as well as the energy supply and mix of kinetic and electrical energy at any given time.
Viewed from above, the car is widest at the front and narrows towards the rear for an improved aerodynamic profile, which VW says resembles the aerodynamic lines of a dolphin. The dolphin-like looks continue to the side profile with the roofline tracing an arc from the A-pillars to the rear.
To prevent air turbulence the rear wheels are fully covered and the air flows have also been optimized by small spoilers in front of and behind the wheels, while the door mirrors have been replaced with digital cameras that send images to two displays inside the vehicle.
Instead of the aircraft-style canopy door of the first 1-Litre and the L1, the XL1 sports wing doors that are hinged low on the A-pillars and just above the windscreen in the roof frame, so they swivel slightly forwards as well as upwards for easier access.
At the front end there’s no longer a typical radiator grille with the actual air intake with electronically controlled louvres for cooling the TDI engine, battery and interior located in the lower front end section. There are also energy-efficient dual LED headlights and narrow turn indicators.
LEDs are also prominent at the rear with a strip of red LEDs integrating reversing lights, rear lights, rear fog lights and brake lights, framing the top and sides. The coupé-shaped roofline has no rear windscreen but includes a large rear boot lid that covers the drive unit and 100-liter luggage space.
When the L1 was unveiled in 2009, Volkswagen indicated it would be entering production in 2013. We’ll be interested to see if this updated model is on track for that date or whether the company hopes to bring the XL1 into production before then. All will hopefully be revealed this week when Volkswagen unveils the XL1 at the Qatar Motor Show, which runs from January 26 to 29.
See the stories that matter in your inbox every morning