With the hybrid system engaged the prototype XL1 accelerates from 0-62 mph (0-100 km/h) in 11.9 seconds and has an electronically limited top speed of 100 mph (160 km/h). The electric motor can deliver 100 Nm of torque from a standstill and works as a booster to support the TDI engine, which itself delivers 120 Nm of torque. Together, the TDI and E-motor deliver a maximum torque of 140 Nm in boosting mode.
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.