Volkswagen 1-litre car
The Volkswagen 1-litre car is a two-person concept car produced by Volkswagen. The 1-litre car was designed to be able to travel 100 km on 1 litre of diesel fuel (280 mpg-imp; 240 mpg-US), while being both roadworthy and practical. To achieve such economy, it is produced with lightweight materials, a streamlined body and an engine and transmission designed and tuned for economy. The concept car was modified first in 2009 as the L1 and again in 2011 as the XL1, with limited production of the XL1 slated to begin by late 2013.
The prototype VW 1-Litre concept car was shown to the public in April 2002 when Dr. Ferdinand Piech, then Chairman of the Board of Management, drove the concept between Wolfsburg and Hamburg as part of the Volkswagen annual meeting of stockholders.
For aerodynamics, the car seats two in tandem, rather than side-by-side. There are no rear view mirrors and it instead uses cameras and electronic displays. The rear wheels are close together to allow a streamlined body. The total aerodynamic drag is minimal because both the drag coefficient and frontal area are small (see drag equation). The drag coefficient (Cd) is 0.159, compared to 0.30 - 0.40 for typical cars.
The external dimensions of the car are 3.47 m (11.4 ft) long, 1.25 m (4.1 ft) wide and 1.10 m (3.6 ft) tall. There is 80 l (2.8 cu ft) of storage space. The car features an aircraft-style canopy, flat wheel covers and an underbelly cover to smooth the airflow. The engine cooling vents open only as needed.
For light weight, the car uses an unpainted carbon fibre skin over a magnesium-alloy subframe. Individual components have been designed to be low weight, including engine, transmission, suspension, wheels (carbon fibre), brakes (aluminium), hubs (titanium), bearings (ceramic), interior, and so on. Empty vehicle weight is 290 kg (639 lb).
The body and frame are designed with crush/crumple zones and roll-over protection, and the tandem seating means large side crush zones. Volkswagen claims protection comparable to a GT racing car. The car has anti-lock brakes, airbags with pressure sensors, and stability control.
The engine is a one-cylinder 299 cm3 (18 cu in) diesel producing just 6.3 kW (8.4 hp). It drives through a six-speed transmission that combines stick-shift mechanics, weight, and drive efficiency with automatic convenience and efficiency controls. There is no clutch pedal. The gear selection (forwards, reverse or neutral) is made using a switch on the right-hand side of the cockpit. The engine is switched off automatically during deceleration and stops, and auto-restarted when the acceleration pedal is pressed.
According to Volkswagen, the vehicle consumes 0.99 l/100 km (238 mpg-US; 285 mpg-imp), giving it a 650 km (404 mi) driving range on one tank of fuel.
Towards production 
Around June 2008 car magazines were reporting a powerplant change to a two-cylinder diesel-electric hybrid. Volkswagen only expected the car to be a limited production run, and prices were expected by one industry insider to fall somewhere between €20,000 and €30,000.
2009 model 
The second Volkswagen 1-litre car, named L1, was first shown to the public at the 2009 Frankfurt Motor Show. Limited production of the VW L1 was expected to start in 2013 but with the announcement of the XL1 in 2011 this was considered unlikely.
The L1 continues the two-seater tandem concept first shown in the 2002 1-litre concept. It has a curb weight of 381 kg (840 lb), with a low coefficient of drag of 0.195. It is 3.813 m (12.5 ft) in length, 1.143 m (3.8 ft) mm tall and 1.2 m (3.9 ft) wide. Frontal area is 1.02 m2 giving a CdA of 1.99 m2.
It uses one half of a 1.6-litre TDI engine in a hybrid installation. The 800 cm3, twin-cylinder, common-rail turbodiesel is joined by a 10 kW (13.4 hp) electric motor and has a CO2 emission 39 g/km. The engine operates in two modes: "eco" mode, giving 20 kW (27 hp), and "sport" mode giving 29 kW (39 hp). The electric motor provides extra acceleration and can power the L1 on its own for short distances. Volkswagen claimed the L1 can achieve a top speed of 158 km/h (99 mph), with 0–100 km/h (0-62 mph) acceleration in 14.3 s.
2011 model 
According to Volkswagen, the XL1 can achieve a combined fuel consumption of 0.9 litres per 100 kilometres (310 mpg-imp; 260 mpg-US) and CO2 emissions of 24 g/km. Like the L1, the XL1 uses a two-cylinder turbo-diesel. Displacing 800 cm3, it is rated at 35 kW (47 hp) and 121 Nm (89 lb-ft) of torque and transmits power to the rear wheels through a seven-speed DSG transmission. The electric motor pitches in with 20 kW (27 hp) and 100 Nm (74 lb-ft) of torque, and can work in parallel with the diesel or drive the car independent of it. Fully charged, the XL1 can travel up to 35 km (22 mi) on electric power.
The XL1 has a curb weight of 795 kg (1,750 lb), and a drag coefficient of 0.186 (a similar drag coefficient to the General Motors EV1 electric car). Frontal area is 1.5 m2 giving a CdA of 0.28 m2.
Just 23.2% of the car (184 kg (410 lb)) is made out of either steel or iron; the drivetrain weighs 227 kg (500 lb). The XL1's length and width are similar to the Volkswagen Polo, with a length of 3,970 mm (156.3 in) and width of 1,682 mm (66.2 in). However, the car is much lower with a height of only 1,184 mm (46.6 in), and has a coupe-like roofline, reducing interior volume. The design incorporates gull-wing doors, with the interior seating layout using a staggered side-by-side arrangement similar to a Smart Fortwo, rather than the previous versions' tandem seating.
In February 2012, Volkswagen confirmed that it would build a limited series of XL1s starting in 2013. In February 2013, Volkswagen confirmed that limited production would start at the end of 2013, with claimed fuel economy to be 0.9 l/100 km (260 mpg-US; 310 mpg-imp) and emissions of 21 g/km of CO2. The test cycle allows for a re-charge of the battery every 75 km (47 mi) which results in a high mpg value. Using diesel alone the car is capable of up to 2.0 l/100 km (120 mpg-US; 140 mpg-imp). As with the 2011 concept XL1, it is powered by a 800 cm3 two-cylinder diesel engine with 35 kW (48 PS; 47 bhp) and a 20 kW (27 PS; 27 bhp) electric motor, delivering power to the rear wheels through a seven-speed dual-clutch gearbox. The drag coefficient has increased slightly from 0.186 to 0.189. The production version is expected to deliver an all-electric range of 50 km (31 mi) and the plug-in diesel-electric hybrid was unveiled at the 2013 Geneva Motor Show. 250 examples will be built.
- "Volkswagen baut das erste 1-Liter-Auto der Welt." (in German). Volkswagen AG. Retrieved 2008-02-21.
- Benjamin Jones (2008-05-07). "VW Confirms 1L Concept Will Become Reality in 2010". Retrieved 2008-05-07.
- VW 1-Litre-Car, Canadian Driver, June 5, 2002 http://www.canadiandriver.com/articles/gw/vw1litre.htm Retrieved 2002-06-05
- "Car magazine 30 June 2008". Carmagazine.co.uk. 2008-06-30. Retrieved 2011-09-23.
- Horrell, Paul (2009-09-18). "Frankfurt Motor Show: Volkswagen L1 Concept". The Daily Telegraph (London). Retrieved 2009-09-22.
- [Colum] (2009-09-15). "Frankfurt 2009: Volkswagen L1 Concept Gets 170 MPG, Production Planned for 2013". Retrieved 2010-07-20.
- Blanco, Sebastian (2009-09-14). "Frankfurt 2009: Volkswagen L1 Concept, the "most fuel-efficient automobile in the world," gets 170 mpg". AutoBlog. Retrieved 2012-11-02.
- "Volkswagen Futures official website". Volkswagen.co.uk. 1999-02-22. Retrieved 2011-09-23.
- "Volkswagen press release". Volkswagen.co.uk. 1999-02-22. Retrieved 2011-09-23.
- "Volkswagen to debut XL1 PHEV prototype at Qatar Motor Show; fuel consumption of 0.9 L/100 km (261 mpg US)". Green Car Congress. 2011-01-25. Retrieved 2011-01-26.
- Volkswagen CarScene TV: Volkswagen XL1 - Vision wird Realität (in german)
- "Auto Express January 2011". Autoexpress.co.uk. Retrieved 2011-09-23.
- Jonathan Schultz (2011-01-25). "Volkswagen Previews Refreshed 261 M.P.G. XL1 Prototype". The New York Times. Retrieved 2011-01-26.
- Jake Holmes (2011-01-31). "Volkswagen XL1 Concept - Auto Shows". Car and Driver. Retrieved 2011-01-31.
- "Volkswagen to launch diesel-powered XL1 plug-in hybrid in 2013". Left Lane News. Retrieved 3 February 2012.
- "Volkswagen XL1 revealed". Auto Express. 21 February 2013. Retrieved 22 February 2013.
- Volkswagen Media Services (2013-02-21). "Volkswagen to produce XL1 diesel plug-in hybrid at Osnabrück; 261 mpg US". Green Car Congress. Retrieved 2013-02-21.
- Volkswagen press release, 15 April 2002, "The 1-liter car" (archived)
- Volkswagen press release, 15 September 2009, E-Up! and L1 (archived)
- Official Volkswagen 1-Litre car press release
- Official Volkswagen L1 press release
- Official Volkswagen XL1 press release
- Supercars 1-litre report