The 911 | Chassis
Vehicle yaw/
course deviation
Vehicle yaw/
course deviation
Correction to
vehicle course
deviation and
stabilisation
Correction to
vehicle course
deviation and
stabilisation
Oversteer without PSM
Understeer without PSM Understeer with PSM
A strong character knows when to take a back seat.
Porsche Stability Management (PSM).
PSM is an automatic control
system for providing stability
at the limits of dynamic driving
performance, and is a standard
feature of every 911. Sensors
work continuously to monitor the
driving direction, speed, yaw
velocity and lateral acceleration
of the car. Using this infor-
mation, PSM computes the actual
direction of motion. If this
direction deviates from the
desired course, PSM initiates
braking interventions targeted
at individual wheels – recog-
nisable by the flashing indicator
light in the cockpit – in order to
stabilise the vehicle.
Under acceleration on wet or low-
grip road surfaces, PSM improves
traction using the ABD (automatic
brake differential) and ASR (anti-
slip regulation) functions. The
control interventions are smooth
and precise, giving an agile
response. When ‘Sport’ mode is
selected on the optional Sport
Chrono Package Plus (p. 74),
the PSM intervention threshold is
raised to enable greater driver
involvement – particularly at
speeds of up to approximately
70 km/h (45 mph).
The integrated ABS shortens the
braking distance even further
and the braking inputs are smooth
and precise, thereby enhancing
comfort.
An enhanced PSM system is
characterised by two additional
functions: the precharging of the
brake system, and brake assist.
If the driver suddenly releases
the accelerator pedal, PSM
automatically readies the braking
system. With the braking system
having been precharged, the
brake pads are already in light
contact with the brake discs.
Maximum braking power is there-
fore achieved much sooner.
When sudden braking is detected
– i.e. if the pressure on the brake
pedal exceeds a predefined level
– the brake assist function uses
the PSM hydraulics to apply
maximum brake pressure to all
four wheels.
If you want a purely active driving
experience, you always have the
option to deactivate PSM. It is
automatically reactivated, for
your safety, if either of the front
wheels (in sport mode, both of
the front wheels) requires ABS
assistance. The ABD function,
however, remains active at all
times.
In conclusion, PSM offers a high
level of driving stability and
safety – and typical Porsche
agility at the same time.
911 Carrera S Cabriolet
Oversteer with PSM
