Following the success of the BMW i3 electric car, and the i8 hybrid supercar, BMW has developed an even more powerful petrol-electric drivetrain that could underpin prestige and performance models in the future. This could be the most powerful BMW production powertrain ever.
The new system is part of an increasing investment into hybrid electric powertrains, starting with the upcoming 3-Series ActiveHybrid. This one in particular will sit at the top of the range. Expect it to appear in the firm's large saloons and M-powered SUVs in the next few years.
Dubbed Power eDrive, the new system forms part of a extended range of modular hybrid drivetrains being developed in a performance-based EfficientDynamics engineering program at BMW's research and development centre in Munich and envisaged for launch on a limited number of BMW Group production models in what it describes as "up-market segments" before the end of the decade.
The new hybrid system aims to provide the sort of smooth yet urgent step-off performance qualities delivered by a contemporary battery powered electric drive systems like that offered in the Tesla Model S, albeit with an overall range described as being over 600km thanks to a range extender function, including a 100km range on electric power alone.
Revealed in an otherwise innocuous-looking 5-series GT xDrive described by BMW as “the Tesla-killer”, the most powerful of BMW's new modular hybrid drivetrains uses the company's new 170 kW turbocharged 2.0-litre four-cylinder direct injection petrol engine in combination with two electric motors – a 150 kW version of the i3's synchronous unit mounted up front in the space usually taken up by the torque converter in the car's eight-speed automatic gearbox and an even more powerful 200 kW unit set within the rear axle assembly.
All up, it is claimed to boast a combined system output of 500 kW along with a torque loading that, BMW engineers suggest, reaches beyond 1000 Nm – figures that easily top the 338 kW and 720 Nm of the existing 6.75-litre V12 petrol engine used by the 11-year-old Rolls-Royce Phantom.
The principle behind BMW's Power eDrive system is a maximization of electric motor performance.
"The electric motors provide approximately two-thirds of the combined output, with the combustion engine accounting for the remaining third," says Franz Drescher-Kaden, a BMW concept engineer responsible for the new petrol-electric hybrid set-up.
Energy for the electric motors is provided by a 20 kWh lithium-ion battery mounted both longitudinally in the rear of the 5-series GT's centre tunnel and horizontally underneath the rear seat in a space ahead of the rear axle. It can be charged both via plug-in means and on the run using the combustion engine in a steady state mode. The fuel tank has been reduced in size from a standard 70-litres to 30-litres.
As well as acting as a generator to produce electricity, the Power eDrive hybrid system's petrol engine can also provide a performance boost with direct drive to the front wheels during kick down, in which all three power sources are used for propulsion.
Drive is nominally channeled to the rear wheels via the rear electric motor, whose reserves are sent through a multi-speed gearbox like the front motor in an i8. The introduction of the front electric motor, which operates via the eight-speed automatic in which it is housed, provides all-electric four-wheel drive. This is further enhanced by the combustion engine, which also delivers its power to the front wheels.
BMW has not revealed a weight figure for its new hybrid system. However, it does concede the addition of two electric motors as well as the lithium ion battery pack and ancillary electronic management system adds handsomely to the kerb weight. Despite this, the German car maker says the straight line performance of its 5-series GT Power eDrive prototype exceeds that of the 330 kW twin-turbocharged 4.4-litre V8 powered 550i GT, which tips the scales at 2070 kg.
Power eDrive is being developed as a scalable system with power outputs ranging from 190 kW to over 500 kW, according to BMW, which says the plug-in hybrid technology will be "a natural choice for use in up-market vehicle segments". The unit could appear in the forthcoming Rolls-Royce SUV, although the first model it will be dropped into is expected to be the BMW X7 luxury 4X4 in 2017.