Quote:
Originally Posted by vstolpner
I thought light steering was due to the move to electric power steering?
And I'm pretty sure the AWD system always maintains power to all wheel in a 60/40 front to rear split?
I know the E84 maintains a 40/60 front to rear split unless it sees slippage.
|
This might help to explain the new xDrive setup:-
F48 Powertrain
4. xDrive
29
4.3.2. Operating strategy
The operating strategy ensures that the four-wheel drive is operated as required and in an energy efficient manner. The traction requirement is detected in a proactive manner and the drive torque redirected accordingly.
In most driving situations only the front wheels are driven. Only in certain situations is some of the drive torque also transmitted to the rear wheels. The distribution of the drive torque between the front and rear wheels is defined by the DSC. The following criteria are taken into account:
• Speed
• Lateral and longitudinal acceleration
• Brake control
• Steering angle
• Wheel speeds
• Vehicle longitudinal inclination
• Pedal sensor position
• Active driving program (SPORT, COMFORT, ECO PRO)
• DSC status (DSC activated/deactivated, DTC activated/deactivated)
Depending on the driving situation, some of the drive torque is transmitted to the rear wheels.
The exact ratio of the torque distribution is dependent on the activation of the multidisc clutch,
as well as the slip of the wheels. Some factors on the activation of the multidisc clutch are listed below.
The four-wheel drive is activated in the following situations, if there are no other criteria present which prevent this:
• Understeering vehicle
• Increased difference in speed between front and rear wheels
• Large vehicle longitudinal inclination (e.g. on inclines)
• Kick-down position
• Sporty driving style
• Respective environmental conditions, roadway conditions and type of terrain
The four-wheel drive is switched off in the following situations, if there are no other criteria present which prevent this:
• Large steering angle and driving speeds
• Strong braking (ABS)
To assess the road condition and thus for effective, proactive longitudinal torque distribution, the
coefficients of friction between the tires and roadway are calculated by the DSC. The wheel slip,
as well as the longitudinal and lateral acceleration, are evaluated.
Simple!
