Driving and Driving Safety
203
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
vehicle reactions (Ferraria effect) when the
driver releases the accelerator pedal or brakes
on bends. This compensation functions up to
the maximum lateral acceleration.
– PSM actively stabilises the vehicle if necessary
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.
– Improved brake function and shorter stopping
distance in the event of emergency braking.
Readiness for operation
PSM is switched on automatically every time you
start the engine.
Function
Sensors at the wheels, brakes, steering system
and engine continuously measure:
– Speed
– Direction of travel (steering angle)
– Lateral acceleration
– Axial acceleration
– Rate of turn about the vertical axis
PSM uses these values to determine the direction
of travel desired by the driver.
PSM intervenes and corrects the course if the
actual direction of motion deviates from the
desired course (steering-wheel position):
It brakes individual wheels as required.
If necessary, PSM also influences the engine
power or the gear-changing characteristic of
Porsche Doppelkupplung (PDK) in order to
stabilise the vehicle.
The events below inform the driver of PSM control
operations and warn him to adapt his driving style
to the road conditions:
– PSM warning light on the instrument panel
flashes.
– Hydraulic noises can be heard.
– The vehicle decelerates and steering-wheel
forces are altered as 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 engine power is reduced and the
rear wheel on the inside of the bend is braked
if necessary.
– If the rear of the vehicle swings out on a bend,
the front wheel on the outside of the bend is
braked.
