Overview: Volkswagen XL1

Volkswagen’s XL1 Super Efficient Vehicle (SEV), unveiled at the Qatar Motor Show in 2011, was originaly a collection of technologies brought together to demonstrate how a very economical car might be built using current technology: a plug-in hybrid with a small diesel engine and a light, aerodynamic body. Now Volkswagen has announced that the XL1 will enter series production at the Company’s Osnabrück plant.

The result of Volkswagen’s efforts is a combined return of 313mpg in the NEDC rolling-road test régime; this is equivalent to a CO2 yield of 24g/km. (We will attach details of the formula used to give CO2 emission equivalents for electric running just as soon as we know what it is.)

Volkswagen XL1.

Powering the XL1 is an 800cc twin-cylinder TDI working with an electric motor. The diesel is two-thirds of a Polo Blue Motion power-unit and delivers 48PS. The electric motor adds 27PS to this, giving a combined 75PS: the same output as the Polo. Given the very low drag coefficient of Cd 0.186, this is more than adequate for general use. The combined torque — 120Nm from the diesel, 100Nm from the motor — should be enough to provide lively performance, given the kerb mass of 795kg. Quoted performance figures include standing start acceleration to 100km/h in 11.9s and an electronically limited maximum speed of 99mph.

The TDI engine is linked to the electric motor and the seven-speed DSG gearbox with an automatic clutch mounted between each unit; this measure allows each element to be disengaged from the drivetrain. The electric motor can either work independently of the TDI engine or in tandem when accelerating. In pure electric mode, the XL1 can travel up to around 20 miles before the diesel engine cuts in.

In both its styling and packaging, the XL1 draws on the one-litre car of 2002 and the L1 concept of 2009. (Note that ‘one litre’ refers to fuel consumption, not engine size.) The XL1 has evolved to feature staggered seating. Passenger accommodation is perhaps the XL1’s Achilles’ heel, as it is only a two-seater — the price paid for building low in search of a good CdA.

The body structure has been constructed using new techniques, providing a very good strength-to-mass ratio. Bodyshell mass is a modest 230kg.

To save as much body mass as possible, and yet still have a car which is viable for series production, Volkswagen developed and patented a new system for the manufacture of the Carbon Fibre Reinforced Polymer (CFRP) parts on the car. The technique is a type of Resin Transfer Moulding (RTM) process. RTM of one kind or another has been in use since the 1990s.

As we have mentioned, the kerb mass is 795kg, of which the bodyshell contributes 230kg. In addition, the drivetrain weighs 227kg, the running gear 153kg, the interior (including a pair of bucket seats) 80kg, and the electrical system 105kg. In total, 23.2 per cent. of the car — 184kg — is made out of either steel or iron.

Further savings are made through the use of lightweight materials, including magnesium (wheels), ceramics (brake discs) and aluminium (dampers, steering system, brake calipers).

Volkswagen considers the XL1 to be the first in a new class of Super Efficient Vehicles.

Volkswagen XL1
Vehicle type Plug-in
Cylinders 2 2 1
Fuel D D D
Swept volume 799cc 799cc 299cc
PS 48 39 8.5
Nm 120 100 18.4
Emissions EU6 EU6 N/S
Maximum speed 99* 99* N/S
0-100km/h 11.9 14.3 N/A
Combined MPG
CO2 g/km 24 36 N/S
Transmission DC7 DC7 AM6
Driven wheels Rear Rear Rear
Battery type Li-ion Li-ion N/A
Motor PS 27 14 N/A
Motor Nm 100 N/S N/A
Kerb mass 795 380 290
PS/t 94 139 29
Nm/t 276 63
Length 3888 3813 3470
Width 1665 1200 1250
Height 1156 1143 1000
Wheelbase 2224 N/S 2205
Cd 0.186 N/S N/S
* Electronically limited.
Tatra 77a (1938).
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