BMW has detailed the selectable all-wheel drive (AWD) 'xDrive' system in its all-new forthcoming M5 performance sedan, which will also feature a more potent version of the 4.4-litre twin-turbo V8 in the current model, as well as an eight-speed 'M Steptronic' automatic transmission.
Due to arrive in Australia around March or April next year, the M5 will feature all-new drivetrain technology that BMW says will strike a balance between the handling characteristics of rear-wheel drive with the traction and stability of AWD.
The xDrive system works by only using the front wheels when the rear wheels no longer have enough traction to transmit enough power to the road, retaining the rear-drive feel of previous M5s.
It is also selectable, with the dynamic stability control (DSC) and M xDrive modes configured in a way to let the driver choose from five different drive modes, ranging from pure rear-drive to full AWD to suit road and environmental conditions.
The default mode for the M5 is 4WD with DSC on, while 4WD Sport sends extra power to the rear wheels and allows for wheel slip.
Turning DSC off allows for three modes – 4WD, 4WD Sport and 2WD – with each mode transitioning further from a focus on traction and stability to agile handling and sporty feel.
The 'Active M Differential' aids traction and handling through the rear wheels, and can engage its locking mechanism between zero and 100 per cent as required.
Part of the reason for the move to AWD is the increasing amount of power in modern engines makes it harder to get all the power down, which was explained at the launch of the new 5 Series in October last year by BMW Munich product expert Sven Arens.
“Engines have become so powerful. For a reasonable saloon car, the cut off is 700Nm of torque on two driven wheels.
“With the current M5 we are at 680Nm and thanks to the fact that we use Michelin Pilot Super Sport tyres, it can get all the traction and all the power on the ground.
“If we are now stepping up to 600hp (447kW), which means we are going to go beyond the 700Nm of torque, only if you would use a (Michelin Pilot Sport) Cup 2 tyre would you be able to transfer that to the ground.
“But then it means your customer would come in every 5000km for new tyres. They won’t be very happy.”
Under the bonnet of the new M5 will be a reworked version of the 4.4-litre twin-turbo V8 powering the current M5, but BMW has promised the new powerplant will deliver more than 447kW, with the reported figure closer to 459kW, which would make it the most powerful engine in BMW’s stable – even more than that of the 448kW 6.6-litre twin-turbo V12 in the incoming M760Li xDrive.
Torque will reportedly also push more than 700Nm, up from 680Nm in the current model.
BMW has eschewed the seven-speed dual-clutch transmission for a new eight-speed 'M Steptronic' automatic shifter, which it says will shift even faster than the old dual-clutch unit while providing a ratio spread that helps keep fuel consumption low.
Despite the addition of an AWD system, BMW says the new M5 will be even lighter than the old model thanks in part to the addition of a carbon fibre roof.
The 0-100km/h sprint can be completed in under 3.5 seconds, from 4.2s in the old model.
Whispers suggest the new M5 could be shown publicly at the Frankfurt motor show in September, ahead of its March/April Australian release date.