The BMW ActiveHybrid X6 is the world’s first Sports Activity Coupé with full hybrid drive. The overall drive system featured in the BMW ActiveHybrid X6 consists of a 300 kW/407 hpV8 gasoline engine with BMW TwinPower Turbo Technology and two electric synchronous motors delivering 67 kW/91 hp and, respectively, 63 kW/86 hp. Maximum system output is 357 kW/485 hp, peak torque is 780 Newton-metres/575 lb-ft.
The overall drive system featured in the BMW ActiveHybrid X6 consists of a 300 kW/407 hpV8 gasoline engine with BMW TwinPower Turbo Technology and two electric synchronous motors delivering 67 kW/91 hp and, respectively, 63 kW/86 hp. Maximum system output is 357 kW/485 hp, peak torque is 780 Newton-metres/575 lb-ft.
The electric motors receive their energy from an NiMH high-performance battery positioned beneath the floor of the luggage compartment and feeding electric power also to the car’s on-board network. Luggage compartment capacity is therefore the same as on the “regular” BMW X6 with its combustion engine. When applying the brakes or taking back the gas pedal kinetic energy is converted into electrical energy and is stored in the high-performance battery. To provide this function either one or both of the electric motors acts as a generator, feeding electric power generated without the slightest increase in fuel consumption directly into the high-voltage battery. Subsequent use of this energy to provide extra drive power
significantly reduces the consumption of fuel.
The two-mode active transmission is based on an ECVT (electric continuously variable transmission) operating in two separate modes. One mode is for setting off with particular power and for driving at low speeds, the second is for motoring at high speeds.
When setting off only one of the two electric motors is activated. Then, as soon as the driver requires more power, the second electric motor automatically activates the combustion engine and subsequently serves as a generator providing a permanent supply of electric power.
When driving steadily at a higher speed most of the power required is delivered by the combustion engine in a largely mechanical process. Here again, one of the two electric motors acts as a generator.
Together with the mechanical components, the electric motors form a joint transmission unit providing the optimum transmission ratio at all times as a function of driving conditions. The mechanical link within the two-mode active transmission is provided by three planetary gearsets in a configuration dividing the drive power generated by the combustion engine and the two electric motors into two transmission modes and therefore ensuring a degree of variability in combining the two power sources conventional hybrid drive would not be able to provide.
The two operating modes of the electric motors are supplemented and enhanced by fixed transmission ratios providing a total of seven gears for full use of the highly efficient hybrid function throughout the vehicle’s complete range of operation and at the same time maintaining the driving performance.
In the generator mode the two electric motors supply a lot of the energy required to slow down the vehicle whenever necessary. Indeed, the stopping power generated in this way is up to 3 metres/sec2 or, respectively, 0.3 g in a purely recuperative process, significantly reducing the load acting on the mechanical brake system.
Sensotronic Brake Actuation (SBA) in the BMW Active Hybrid X6 may be used at any time without a direct mechanical connection between the brake pedal and the hydraulic circuit. Pedal movement is recorded by sensors and split up by a control unit into brake power generated in a regenerating and in a hydraulic process. At the same time an integrated pedal force simulator generates the usual brake feeling for the driver as an additional factor in this brake-by-wire solution.
The active brake servo builds up brake pressure with electrical control according to the signals emitted by the control unit. To ensure brake power assistance also in the all-electric mode, the BMW ActiveHybrid X6 comes furthermore with an electrical under-pressure pump replacing the vacuum pressure in the intake system of the combustion engine on a conventional vehicle. A mechanical fallback function, in turn, guarantees full operation of the brake system in the event of a failure or deficiency in the electrical system, in which case the stopping power required is generated by the hydraulic system alone, like on a conventional vehicle.
Under normal conditions BMW xDrive spreads out drive power to the front and rear axle in a 40:60 split, sensors consistently measuring wheel slip both front and rear. The system is able to vary the balance of drive power within fractions of a second, BMW xDrive, unlike conventional all-wheel-drive systems, thus looking ahead and not only responding when a wheel is already spinning.
In city traffic the BMW ActiveHybrid X6 can be run in the all-electric mode without using the combustion engine. A further advantage is that the vehicle comes with a new generation of Auto Start Stop technology featured here for the first time. Tailored specifically to the requirements of a hybrid car, this new Auto Start Stop function allows a much higher standard of comfort and is available more often than the conventional system. Automatic deactivation of the combustion engine at a road junction or at the traffic lights does not in any way impair the driving experience, just as the V8 power unit will start again immediately as soon as the driver presses down the gas pedal.
BMW ActiveHybrid X6 provides the Auto Start Stop function consistently at all outside temperatures, no matter how cold or how hot.
As long as the engine is switched off, the electric climate compressor automatically maintains the climate and temperature desired within the passenger compartment. All other electrically operated functions are also maintained, with the on-board network being consistently supplied with power from the high-voltage storage unit. The only way to deactivate the special hybrid Auto Start Stop function is by choosing the manual gearshift mode on the automatic transmission.