The production version of Volkswagen’s XL1 Super Efficient Vehicle (SEV) is under development, according to VW Group CEO Martin Winterkorn. The concept form has been revealed at the Qatar Motor Show while the final version is expected to enter small series production by 2013. It’s believed that the unit will be built either in Dresden or Wolfsburg and it will be equipped with a hybrid powertrain that includes a 27hp electric motor and a 0.8-liter 48 hp two-cylinder diesel engine. The two have a combined output of 75hp.
This may seem underpowered but it has to be considered that the concept weighs just 795 kg (1,752 lbs) due to the use of lightweight materials such as carbon fiber reinforced plastic, aluminum, ceramics and magnesium.
VW said that the XL1, which features a seven-speed double-clutch gearbox, can go from zero to 62 mph in 11.9 seconds and it can reach a top speed of 100 mph (161 km/h). In addition, it offers a fuel efficiency rating of 0.9 liters per 100 km (261 US mpg or 313 UK mpg) and has a CO2 emissions rating of 24 grams per km.
Volkswagen revealed that the new XL1 will be an example of its plug-in hybrid concept which makes use of the common rail turbodiesel, or TDI, which is known for having fuel efficient technology, and the dual clutch transmission or DSG. This whole unit is then placed on top of the axle in the rear.
The hybrid module itself, the one with the clutch and the electric motor, has been placed in the middle of the TDI and its 7-speed DSG, and incorporated to the DSG transmission case instead of the standard flywheel. The energy that the E-motor uses is sourced from the lithium-ion battery and it is the power electronics that manage the high voltage of the energy flow from the battery to the E-motor, and back again. These electronics run at 220 volts although the entire electrical system of the XL1 gets the needed 12 volts from a DC/DC converter.
An interesting fact about the XL1 is how the TDI engine is able to interact with the E-motor. Under just 0.8 liter of displacement, the TDI displays output at 35 kW (48 PS). Though the TDI is supported by the E-motor during acceleration, the engine also allows for the XL1 Concept to reach as far as 35 kilometers. When under this mode, what happens is that the clutch is disengaged which results in the TDI being decoupled from the vehicle’s drivetrain and thus eventually shut down.
All through this, the gearbox’s clutch continues to be closed in order to allow the DSG to be able to fully engage the XL1’s electric motor. Assuming the battery has been charged sufficiently, it is possible to run the XL1 using purely electricity. Using this mode is easy as all that is needed is to activate the electric mode button that is placed on the instrument panel. Should the driver want to restart the engine, it is comfortable and easy.
Referred to as “pulse starting” while being driven, the rotor of the electric motor is made to spin faster and then pairs this to the engine clutch. This helps the TDI get to the needed speed and then starts it. All of this is possible without experiencing any jolts and thus the driver cannot even detect that the engine has been restarted.
However, should the driver apply the brake, it is then that the E-motor runs the generator in order to trigger the battery regeneration, which is using the braking energy in order to charge the battery.
When experiencing certain conditions of the road, the XL1 can shift the load that is shared by the electric motor and the TDI engine. This allows the turbodiesel to run at the best efficiency level. In addition, the gears of the DSG are often chosen with the goal of minimizing use of energy.