BMW Heaven - The Knowledge Base 2.0

  • Increase font size
  • Default font size
  • Decrease font size

X6 ActiveHybrid - E72 (2009 - ...) - Drivetrain: Superior Technology in a Winning Team.

User Rating: / 73
Article Index
X6 ActiveHybrid - E72 (2009 - ...)
Driving Experience
Body and Safety
Features and Equipment
All Pages


Drivetrain: Superior Technology in a Winning Team.

• BMW presents the most powerful hybrid in the world.
• V8 power unit with BMW TwinPower Turbo Technology and two electric motors del ivering overall system output of 357 kW/485 hp.
• Supreme variabil ity and efficiency in generating and transmitting drive power through the Two-Mode Active Transmission and BMW xDrive.
“Never before have the combustion engine and hybrid components been matched to one another as precisely as in the BMW ActiveHybrid X6. The V8 power unit with BMW TwinPower Turbo and the Two-Mode Active Transmission form a perfect team.” Hans-Stefan Braun, Project Manager BMW Drivetrain Development ActiveHybrid X6

The drive system featured in the BMW ActiveHybrid X6 is made up completely of cutting-edge components offering top technology the world over unparalleled in particular in terms of all-round efficiency. This applies to the V8 gasoline power unit with BMW TwinPower Turbo Technology and to the two synchronous electric motors integrated in the innovative Two-Mode Active Transmission developed specifically for the BMW ActiveHybrid X6 and BMW’s intelligent xDrive all-wheel-drive system, the high-performance battery with its particularly high capacity, and the power electronics serving among other things to mastermind the highly effective generation of electric power through Brake Energy Regeneration.
Both the individual details and the overall concept clearly bear out BMW’s leading competence in the development of drive systems. This superiority is also expressed clearly by the full hybrid technology featured for the first time in a BMW, BMW ActiveHybrid technology capitalising on both the strengths of the combustion engine and the specific qualities of electric drive to offer a truly outstanding combination of these two drive modes.
The BMW ActiveHybrid X6 is the most efficient vehicle in its performance class. At the same time it comes right at the top of all hybrid vehicles worldwide in terms of driving dynamics through its overall system output of 357 kW/485 bhp.

Eight-cylinder power unit with TwinPower Turbo Technology.
The combustion engine is an eight-cylinder absolutely unique in technical terms presented for the first time in the BMW X6 xDrive50i. The world’s first V8 gasoline engine with two turbochargers and two catalytic converters in the V-section between the two rows of cylinders develops maximum output of 300 kW/407 hp from engine capacity of 4.4 litres, maintaining this supreme power all the way from 5,500 – 6,400 rpm. Torque peaks at 600 Newton-metres/442 lb-ft in the speed range between 1,750 and 4,500 rpm.
With BMW TwinPower Turbo Technology four cylinders are each supplied with compressed air by one turbocharger for a particularly spontaneous and direct response to the gas pedal. Engine power builds up without the slightest delay, continuing all the way to high engine speeds.
The innovative arrangement of the turbochargers also benefits the response of the engine, the new position of the intake and outlet ducts helping to keep the intake pipes and manifolds shorter and provide larger cross-sections significantly minimising pressure losses on both the intake and exhaust side.
High Precision Injection developed by BMW ensures precise dosage of fuel at all times. In the same process the cooling effect of the fuel injected directly into the engine allows a compression ratio exceptionally high on a turbocharged engine, further enhancing the efficiency of the V8 power unit.
Piezo-injectors positioned in the middle between the valves help to make the combustion process particularly smooth, efficient and clean, the V8 power unit therefore fulfilling both the European EU5 standard and the ULEV II standard in the USA.
Compared with the BMW X6 xDrive50i, the power unit has been modified in a number of its features to meet the specific requirements of the BMW ActiveHybrid X6. First, there is no longer a conventional starter, just as the alternator and belt drive for the a/c compressor and the hydraulic pump on the power steering have both been dropped. The main and secondary coolant circuit, in turn, have been modified for all-electric motoring, and a heat insulation plate protects the power electronics additionally from excessive temperatures.
The position of the oil filler manifold has been modified, the conventional torque converter is replaced by a two-mass flywheel, and the exhaust system has been modified for an optimum acoustic effect when the combustion engine fires and cuts in in the all-electric mode. Last but not least, the specially designed engine cover serves to distinguish this unique power unit also in its design and looks.


Two-Mode Active Transmission as the central unit in fully hybrid drive.
The Two-Mode Active Transmission with its fully integrated electric motors is the central unit in the drive system featured in the BMW ActiveHybrid X6.
Developed specifically by BMW for the Company’s first full hybrid vehicle, the Two-Mode Active Transmission ensures optimum interaction of the combustion engine and electric drive in the interest of maximum power and efficiency at all speeds.
In its dimensions, the transmission is virtually identical to a conventional automatic transmission and is arranged directly behind the combustion engine. Following the principle of an ECVT Electric Continuously Variable Transmission, the Two-Mode Active Transmission provides the mechanical connection between three planetary gearsets and four multiple-plate clutches in a configuration allowing the power split required for the drive power coming from the combustion engine and the electric motors in two transmission ranges and therefore ensuring unique variability in the combination of the two power sources conventional hybrid drive is not able to offer.
One of the two transmission modes is specifically for setting off and accelerating at low speeds, the second is for driving at higher speeds under optimum conditions. When setting off only one electric motor is activated at the beginning, enabling the BMW ActiveHybrid X6 to drive under electric power alone up to a speed of 60 km/h or 37 mph. As soon as the driver requires more power, the second electronic motor automatically fires the eight-cylinder power unit and subsequently acts as a generator providing a permanent flow of electric power. The combustion engine is automatically added to the power flow in accordance with the driver’s requirements and the level of performance needed, and is cut off by the electronic control unit when coasting at speeds below 65 km/h or 40 mph.
Power is transmitted by the Two-Mode Active Transmission acting as a seven-speed transmission operated by the driver by means of an electronic gear selector lever on the centre console. As an alternative to the automatic mode, the driver may also opt for manual selection of gears, shifting up and down either sequentially by moving the gear selector lever appropriately or by using the gearshift paddles featured as standard on the steering wheel of the BMW ActiveHybrid X6.

Electric motors increasing system output to 357 kW/485 hp.
The two electric motors offer almost the same degree of power but have been modified in their performance characteristics as a function of their specific purpose and application. Their output is 67 kW/91 hp and, respectively, 63 kW/86 hp, with peak torque of 260 Newton-metres/192 lb-ft and, respectively, 280 Newton-metres/206 lb-ft.
Maximum system output developed jointly by the combustion engine and the two electric motors is 357 kW/485 hp, with combined torque of 780 Newton-metres/575 lb-ft. This makes the BMW ActiveHybrid X6 the world’s most powerful production hybrid, with acceleration from a standstill to 100 km/h in 5.6 seconds. Top speed is limited electronically to 236 km/h (146 mph) or, respectively, 250 km/h (155 mph) in combination with the optional Sports Package.
The outstanding position of the BMW ActiveHybrid X6 within the BMW X Model segment results in particular from the balance of this kind of performance, on the one hand, and the vehicle’s fuel economy, on the other.
Fuel consumption is a mere 9.9 litres/100 kilometres (equal to 28.5 mpg imp), the CO2 emission rating is 231 grams per kilometre.

High-performance battery with separate liquid cooling systems.
The electric motors receive their energy from a nickel-metal-hydride (NiMH) high-performance battery fitted beneath the floor of the luggage compartment and feeding power also to the vehicle’s on-board network.
Even with the combustion engine switched off, this maintains all electrically operated functions including the automatic air conditioning, with electric power generated through the recuperation of brake energy. To perform this function the electric motors serve as a generator in overrun and when applying the brakes in order to feed electric power generated on no extra fuel into the storage units.
The high-performance battery in BMW ActiveHybrid X6 has a capacity of 2.4 kilowatt hours, with 1.4 kWh being used actively for running the vehicle.
To provide the power required, the high-voltage direct current coming from the high-performance battery is converted into three-phase alternating current for the two electric motors. The maximum power available for a period of three seconds is 57 kW, the control unit for the NiMH battery serving to permanently measure and determine various data such as the power currently available and the charge level.
The high-performance battery comes with its own liquid cooling system incorporating a heat exchanger to cool the battery both through outside air and, additionally, through the coolant circuit in the air conditioning. Both circuits are activated as required either individually or in an appropriate combination, the control unit choosing the most effective and efficient cooling option as a function of ambient temperature and the temperature of the high-performance battery.
The cooling function using the vehicle’s air conditioning is activated by an appropriate switch valve, the electrical a/c compressor is activated automatically as required, with the interior and the battery being cooled independently of one another.
This ensures much more efficient cool ing than with systems cooled by air alone, helping to make the energy storage unit significantly more efficient and maintaining the hybrid functions longer both under extreme weather conditions and whenever the driver prefers a particularly sporting style of motoring. This, in turn, gives the BMW ActiveHybrid X6 a dynamic potential quite unique in comparison with other hybrid vehicle.

Power electronics for highly efficient energy management.
Power electronics developed especially for BMW ActiveHybrid serves to keep energy management on board the BMW ActiveHybrid X6 both efficient and flexible at all times, consistently masterminding the distribution of energy as a function of ambient conditions, the status of the vehicle, and the driver’s individual requirements. The most important parameter for determining and controlling the operating strategy is the charge status of the high-performance battery storing electrical energy generated through the recuperation process.
The power electronics also mastermind the charge process of the high-performance battery during recuperation, alternating current generated by the generators through Brake Energy Regeneration being converted into direct current subsequently fed into the battery.

Recuperation using energy released when applying the brakes.
To generate the electric power stored in the high-performance battery, the BMW ActiveHybrid X6 uses an upgraded version of the Brake Energy Regeneration already featured in BMW’s current models running on a combustion engine alone. In overrun and when applying the brakes, the electric motors act as generators feeding power into the high-performance battery.
This uses energy lost on conventional vehicles as heat dissipated from the brakes. Depending on the stopping power applied, this task of recuperating brake energy is performed either by one or both of the electric motors. The output generated in the generator mode of approximately 50 kW is about 25 times higher than the energy supplied so far by Brake Energy Regeneration.

Generator mode providing electric brake power.
In addition to these features, the two electric motors provide a major share of the brake power required by the vehicle when operating in the generator mode. Indeed, the electrical brake system is able to provide up to 3 m/sec2or, respectively, 0.3 g of brake power in the purely recuperative mode, thus taking a significant burden off the mechanical brake system.
Hybrid technology in the BMW ActiveHybrid X6 serves to convey brake power through the xDrive powertrain to all four wheels, thus benefiting from the stopping power provided by the electric motors in the recuperative mode.
And whenever the stopping power required exceeds the level of 3 m/sec2, the control unit, interacting with the active brake servo, generates additional brake power through the mechanical brakes.

First BMW X Models with Electronic Power Steering.
The BMW ActiveHybrid X6 is the first BMW X Model to feature EPS Electronic Power Steering for active steering assistance both when running on the combustion engine and in the all-electric mode.
EPS Electronic Power Steering on the BMW ActiveHybrid X6 is combined with integrated steering assistance related to road speed (Servotronic).
EPS significantly reduces the energy required in comparison with conventional, hydraulic power steering, since this electronic system is activated only when power assistance is really required or is desired by the driver. When driving straight ahead, therefore, the electric motor does not take up and consume any energy, thus serving to reduce fuel consumption to an even lower level.

Variable, efficient, superior: intelligent xDrive all-wheel-drive technology.
The sporting performance of the BMW ActiveHybrid X6 is also attributable to xDrive all-wheel-drive technology, permanent all-wheel drive with electronically controlled, variable distribution of drive power front-to-rear giving this new model, like all BMW X Models, not only superior traction, but also enhanced driving dynamics.
BMW xDrive stands out as a particularly “intelligent” all-wheel-drive system by feeding drive power through a power divider with an electronically controlled multiple-plate clutch appropriately under all conditions to the axle and wheels with optimum grip on the surface below. BMW Media Information 11/2009 Page 27 Under normal driving conditions BMW xDrive subdivides drive power in a 40:60 front-to-rear split. With sensors constantly measuring wheel spin on the front and rear wheels, the system is able within fractions of a second to vary the distribution of drive power, BMW xDrive – contrary to conventional all-wheel drive – therefore responding even before a wheel starts to spin.
Benefiting from these qualities, xDrive further enhances the driving dynamics of the BMW ActiveHybrid X6 by recognising even the slightest tendency to over- or understeer in good time and taking appropriate counteraction.

Last Updated on Saturday, 01 May 2010 17:42  

Latest specifications

2008 Alpina D3 Biturbo LCI Sedan (E90)

2008 Alpina D3 Biturbo  LCI Sedan (E90)
View full specifications

2010 BMW 135i (E82)

2010 BMW 135i    (E82)
View full specifications

2011 BMW 640d A Coupe (F13)

2011 BMW 640d A  Coupe (F13)
View full specifications

2010 BMW 1 Series M Coupe (E88)

2010 BMW 1 Series M   Coupe (E88)
View full specifications

1994 BMW 740i A Sedan (E38)

1994 BMW 740i A  Sedan (E38)
View full specifications

Latest pictures