Every athlete knows the importance of recuperation to peak performance, not just when coming back from injuries, but also in scheduling in regular recuperation days. Audi is applying the principal to its upcoming e-tron, demonstrating the principle in its e-tron prototype.
The e-tron full-size SUV prototype’s powertrain puts out 300 kW (about 402 hp), which is enough to drive the full-size SUV from zero to 100 km/h in less than six seconds, yet can travel more than 400 km on a full charge thanks to the way it recuperates.
Taking to the 4,302-metre Pikes Peak to prove the theory that one km downhill would return an extra km of range, the e-tron prototype ran the fabled 31-km course from top to bottom, and found that the system recuperated (regenerated) up to 30% of the vehicle’s predicted range.
The regenerative system uses both the vehicle’s electric motors and brakes, and is able to work automatically while the vehicle coasts, manually by manipulating the shift paddles, and through braking. The system works together under deceleration/coasting so that if less than 0.3 g of braking force is applied (i.e., without using the brake pedal), regeneration is handled solely by the electric motors. Audi says this accounts for over 90% of decelerations.
With the paddle shifters, the driver controls the degree of regeneration from lowest drag (mostly free-wheeling) to highest (in which there is noticeable speed reduction, and which allows the driver to control the degree of deceleration through the accelerator pedal — back off a little for a little regeneration; back off a lot for maximum drag).
The brakes only need be involved when there is more than 0.3 g of braking force needed, and rely on a world-first electrohydraulic actuation concept. A hydraulic piston in the brake module generates additional pressure, and can make the system go from deceleration to maximum force in just 150 milliseconds. The rapid pressure build-up shortens braking distances by 20%, says Audi, and the transition from engine braking to friction braking is reportedly seamless.
Acceleration is also done in two stages. The two motors combine for an output of 265 kW (about 355 hp) and 419 lb-ft of torque and can deliver peak outputs for up to a minute, which the company says allows several quick zero-200 km/h runs. With the driver-selectable mode in S, the driver is presented with 300 kW and 490 lb-ft of torque for eight seconds, allowing for quick zero-100 km/h launches.