PSM
Porsche Stability Management:

– Stability management system
– Anti-lock brake system (ABS)
– Brake system prefilling
– Brake booster
– Traction control system (TCS)
– Automatic brake differential (ABD)
– Engine drag torque control (MSR)

Porsche Stability Management (PSM)
PSM is an active control system for stabilization of
the vehicle during extreme driving maneuvers. It
operates together with the Porsche Traction
Management (PTM) system.
PSM makes use of both the ABD and TCS
systems, as well as the known functions of the
anti-lock brake system (ABS) and engine drag
torque control system (MSR).


Warning!
In spite of the advantages of PSM, it is still the
driver’s responsibility to adapt her/his driving style
and maneuvers in line with road and weather
conditions, as well as the traffic situation.
The increased safety that is provided should not
induce you to take greater risks with your safety.
The limits set by the physics of driving cannot be
overcome, even with PSM.
Risks of accident due to inappropriate speed
cannot be reduced by PSM.



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 (load-alteration effect) when
the driver releases the accelerator pedal or
brakes on bends. 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 corners and on
different or varying road surfaces.
– Improved brake functioning and reduced
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:
– Driving speed
– Direction of travel (steering angle)
– Lateral acceleration
– Longitudinal 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 needed. If necessary,
PSM additionally influences the engine power
or the gear-changing characteristic of the
Tiptronic in order to stabilize the vehicle.

The events below inform the driver of PSM control
operations and warn him to adapt her/his driving
style to the road conditions:
– The multi-functional information light in the
instrument panel lights up.
– Light in the PSM Off button 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 beginning
of the brake pedal pulsing.
Examples of PSM control operations
– If the front wheels of the vehicle drift on a
corner, engine power is reduced and the rear
wheel on the inside of the corner is braked if
necessary.
– If the rear of the vehicle swings out on a
corner, the front wheel on the outside of the
corner is braked.
– Brake system prefilling:
The brake system is prepared for possible
subsequent emergency braking if the accelerator
pedal is released suddenly and quickly.
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.
Combined use of PSM and PTM/PTM Plus
In order to ensure optimal stabilization of the
vehicle, the center differential lock (PTM) and
possibly the rear differential lock (PTM Plus) are
also opened when PSM interventions occur.
Tip on driving
When PSM is switched off, wheel-specific brake
interventions and the traction control system
(TCS) are also inactive.
The automatic brake differential (ABD) remains on.

Switching off PSM
f Press PSM OFF button A.
PSM is switched off after a short delay.
The light-emitting diode in the button is lit up.
When the PSM is switched off, the multifunctional
PSM light on the instrument panel is
lit and a message appears in the multipurpose
display of the instrument panel.
During braking, the vehicle is stabilized even
when PSM is switched off.
One-sided spinning of the wheels is prevented,
even with PSM switched off.
PSM should always be switched on during
“normal” driving.
However, it can be of advantage to switch off PSM
temporarily in exceptional situations:
– On a loose surface or in deep snow
– When “rocking the vehicle free”
– When using snow chains.
When the PSM is switched off the slip monitoring
function is also deactivated.