The BMW ActiveHybrid 7 is the first car in the world to combine a V8 petrol engine, an eight-speed automatic transmission and an electric motor in a mild-hybrid concept. The BMW ActiveHybrid X6 is BMW’s first full-hybrid model and is able to drive entirely under electric power and therefore free of CO2 up to speeds of 60 km/h.
The combination of a highly developed eight-cylinder engine featuring BMW TwinPower Turbo technology and High Precision Injection with a three-phase synchronous electric motor gives the BMW ActiveHybrid 7 overall system output of 342 kW and maximum torque of 700 Newton-metres.
Controlled interaction of the two power sources optimises both efficiency and the driving dynamics offered by the BMW ActiveHybrid 7. As a result, the car accelerates from a standstill to 100 km/h in just 4.9 seconds, with average fuel consumption in the EU test cycle of 9.7 litres/100 kilometres.
The ActiveHybrid 7 is also the first BMW with an Auto Start Stop function fitted to an automatic transmission. Also for the first time, the air conditioning and ventilation may remain operating even with the engine switched off.
BMW ActiveHybrid technology uses energy usually lost as brake heat escaping unused from the car. The recuperation capacity of the BMW ActiveHybrid 7 is eight times higher than on a BMW with Brake Energy Regeneration driven exclusively by a combustion engine.
Electric power generated in the BMW ActiveHybrid 7 while the car is running in overrun or under application of the brakes, that is without the slightest increase in fuel consumption, is fed as required into the two on-board networks of the car. In all, the BMW ActiveHybrid 7 comes with a conventional 12 V on-board network supplied with power by an AGM (Absorbent Glass Mat) battery as well as a high-voltage battery featuring lithium-ion technology fitted in compact arrangement in the luggage compartment and operating at a voltage of 120 V.
The eight-cylinder power unit featured in the BMW ActiveHybrid 7 develops maximum output of 330 kW at an engine speed from 5,500–6,000 rpm. Maximum torque of this superior V8 is 650 Newton-metres maintained consistently between 2,000 and 4,500 rpm.
The dynamic response provided by this kind of power is further enhanced by the additional drive power generated by the electric motor. In less dynamic driving situations this additional power allows the combustion engine to run in a more favourable – that is, more efficient – load range, thus optimising its all-round efficiency and motoring refinement.
Nineteen-inch light-alloy rims in aerodynamically optimised turbine wheel design created exclusively for the BMW ActiveHybrid 7 as well as model designations on the luggage compartment lid, the C-pillars behind the side windows and on the entry trim strips serve to visually distinguish the hybrid cars.
The drive system is a 300 kW V8 with BMW TwinPower Turbo technology and two electric synchronous motors developing 67 kW and, respectively, 63 kW. Maximum system output is 357 kW; peak torque is 780 Newton-metres.
The two-mode active transmission provides the ideal combination of the two sources of drive power required for an even higher level of both efficiency and driving dynamics. Through the two electric motors, three planetary gearsets and four multiple-plate clutches, drive power is conveyed in the same way as with a seven-speed automatic transmission. Intelligent xDrive all-wheel-drive technology spreads out the power of the engine variably between the front and rear wheels.
The electric motors draw their energy from an NiMH high-performance battery fitted beneath the floor of the luggage compartment and supplying electric power also to the car’s on-board network. When applying the brakes or taking back the throttle, kinetic energy is converted into electrical energy and saved in the high-performance battery.
To perform this function either one or both of the electric motors, depending on driving conditions, acts as a generator feeding electric power developed without any additional consumption of fuel into the high-voltage battery. The power generated in this process is about 25 times greater than the power developed so far by Brake Energy Regeneration in its “standard” form.
In the generator mode the two electric motors provide a significant share of the brake power required to slow down the car. With the electric brake system stopping forces of up to 3 metres/sec2 or, respectively, 0.3 g may be achieved in a purely recuperative mode. Clearly, this takes a significant load off the mechanical brake system.
The hybrid system on BMW ActiveHybrid X6 is able to convey brake forces through the xDrive drivetrain to all four wheels, developed by the stopping power of the electric motors with their recuperative function. Wherever the brake power required exceeds the figure of 3 metres/sec2, the control unit, using the active brake force booster, generates additional brake power through the mechanical brake.
The two-mode active transmission is based on an ECVT (electric continuously variable transmission) operating in two power-split modes. One mode is specifically for setting off with particularly dynamic power and for low speeds, the second mode is for driving at higher speeds.
The BMW ActiveHybrid X6 is distinguished from its conventional drive train counterparts with hybrid-specific displays in the instrument cluster, entry trim bars bearing the designation “BMW ActiveHybrid” on the driver’s and front passenger’s side, Powerdome on the engine compartment lid as well “ActiveHybrid” designations on the special tailgate trim bar and on the front doors.
Leave a comment