4x4 Explained

Introduction to All Wheel Drive systems - By Eliot Lim

Stability Management Systems

An emerging trend in vehicle dynamics development is the use of "stability management systems", which use much of the ABS and computer controlled AWD hardware to further optimize all available grip. The more sophisticated AWD systems will reproportion the power distribution according to available traction at each wheel, leading to a very safe and neutral feel when powering out of a turn. However these systems do not work if the driver lifts off the accelerator pedal completely in a turn.

Recall that Porsche progressively locked the rear differential to handle such a situation. The latest 996 Carerra 4 will in addition to this, selectively brake individual wheels as needed to stabilize the car when it is driven in a clumsy manner to its limits. Specifically it will brake the inner rear wheel to correct an understeering situation and the outer front wheel for an oversteer. This is done independent of driver input. Stability management systems have started to appear in other more expensive car models and will undoubtedly trickle down and be as common as ABS one day.

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