Porsche Stability Management (PSM)
PSM is an active control system for stabilization of the vehicle approaching the performance limits of driving maneuvers.
Inappropriate Driving Style and Speed
The increased control that is provided should not induce you to take greater risks with your safety. The limits dictated by the laws of physics cannot be overcome, even with PSM.
The risk of accidents due to inappropriate speed cannot be reduced, even by PSM.
The driver bears the responsibility for all driving maneuvers.
Sensors at the wheels, brakes, steering system and engine continuously measure:
– Direction of travel (steering angle)
– Lateral acceleration
– Rate of turn about the vertical axis
– Longitudinal acceleration
PSM uses these values to determine the direction of travel indicated by the driver.
PSM intervenes and helps to correct the course if the actual direction of motion deviates from the chosen course (steering-wheel position):
It brakes individual wheels as needed. In addition, the engine power may be manipulated in order to stabilize the vehicle.
The events below inform the driver of PSM control operations and warn him/her to adapt his/her driving style to the road conditions:
– The multifunctional information light on the instrument panel flashes.
– Hydraulic noises can be heard.
– The vehicle decelerates and steering-wheel forces are altered as the PSM controls the brakes.
– Reduced engine power.
– The brake pedal pulsates and its position is changed during braking.
In order to achieve full vehicle deceleration, foot pressure must be increased after the brake pedal has begun vibrating.
Examples of PSM control operations
– If the front wheels of the vehicle drift on a bend, the rear wheel on the inside of the bend is braked and the engine
power is reduced if necessary.
– If the rear of the vehicle swings out on a bend, the front wheel on the outside of the bend is braked.
Additional braking functions
– Pre-filling the brake system:
The brake system is prepared for possible subsequent emergency braking if the accelerator pedal is released suddenly
The brake system is prefilled and the brake pads are already applied gently to the brake discs.
– Brake booster:
In the event of an emergency braking operation where the pedal force is insufficient, a brake booster provides the
braking pressure necessary for maximum deceleration at all 4 wheels.
Advantages of PSM
– Best possible traction and lane-holding ability in all driving situations – even on road surfaces with varying friction.
– The system compensates for undesired lateral vehicle reactions when the driver releases the accelerator pedal
or brakes when cornering.
This compensation functions up to the maximum lateral acceleration.
– PSM actively stabilizes the vehicle as required during dynamic driving maneuvers (e.g. rapid steering movements, during
lane changes or on alternating bends).
– Improved braking stability on bends and on different or varying road surfaces.
– It improves braking function and shortens stopping distance in the event of emergency braking.
Readiness for operation
PSM is switched on automatically every time you start the engine.
PSM should always be switched on during "normal" driving.
However, it may be advantageous to switch off PSM temporarily in exceptional situations, for example:
– On a loose surface or in deep snow,
– When "rocking" the vehicle free and
– When using snow chains.