Psm question help???
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Psm question help???
I just freshened up my turbo's and upon getting the car back I noticed that even when I shut the PSM off it keeps flicking on and off holding the car back. I have seen a few posts discussing PSM but my question is there anyway to fully disengage it. I find it very difficult to drive the car with over 700whp when PSM is on.
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I just freshened up my turbo's and upon getting the car back I noticed that even when I shut the PSM off it keeps flicking on and off holding the car back. I have seen a few posts discussing PSM but my question is there anyway to fully disengage it. I find it very difficult to drive the car with over 700whp when PSM is on.
)IMO if it blinks and simultaneous your car holds back there's a problem with your tune...like overboost protection engaging or ignition being pulled...
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with it switched off.
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Unplug the booster pump under the master cylinder, one big two wire plug. It will put your psm light on but will go away when you plug it back in. The car can no long apply the brakes. If it still feels like psm in on you have a maf issue.
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What Tim said. I have a trunk mounted on/off switch that is wired to the power supply cable for the PSM pump. Total cost: $3.00 and 30 min of your time. I have never turned it on but the option is there. PSM is totally out of the loop and combined with an LSD and RWD makes this a real drivers car.
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With PSM on and smooth driving there were no problems, works as it should.
With PSM off you could spin it like a top if you wanted, or drift all day long. Zero interference from PSM, too much throttle and it would bounce off the rev limiter spinning the tires for as long as you dared. So I don't really believe that it's not ever off, turn it off and it's off.
Car was a 2001 US model with AMS billet K16 and a LSD, perhaps the PSM is different in the newer years, mine is also a 2001 US model.
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could very well, be right. i just in fact read in here, that the psm CAN be de-activated but it requires more that a toggle of the dash button. as to your real world experience, i defer. my only MAJOR experience with abs/psm was going ( fully ) sideways at a high rate of speed ( badly cutoff ) and it saved me from disaster, of this i have no doubt. i am a fan, even when it pisses me off to activate in/out cornering etc. i am not embarrassed to say at this power level, this driver's *aid* has not hurt me yet.
Last edited by '02996ttx50; Apr 6, 2013 at 10:11 AM.
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Not so sure about that, just drove a 996TT at a winter driving school on a frozen lake. Car had snow tires on it but the viscous coupler was worn out for sure, no where near as awd as my car. By the end of the day we had worn through the snow to shear ice of the frozen lake, grip as you could imagine was almost nil.
With PSM on and smooth driving there were no problems, works as it should.
With PSM off you could spin it like a top if you wanted, or drift all day long. Zero interference from PSM, too much throttle and it would bounce off the rev limiter spinning the tires for as long as you dared. So I don't really believe that it's not ever off, turn it off and it's off.
Car was a 2001 US model with AMS billet K16 and a LSD, perhaps the PSM is different in the newer years, mine is also a 2001 US model.
With PSM on and smooth driving there were no problems, works as it should.
With PSM off you could spin it like a top if you wanted, or drift all day long. Zero interference from PSM, too much throttle and it would bounce off the rev limiter spinning the tires for as long as you dared. So I don't really believe that it's not ever off, turn it off and it's off.
Car was a 2001 US model with AMS billet K16 and a LSD, perhaps the PSM is different in the newer years, mine is also a 2001 US model.
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Now some tech talk...:
Porsche Stability Management 5.3 (PSM)
Porsche Stability Management (PSM) 5.3 was introduced
on the 1999 Carrera 4 (996). PSM 5.3 determines
direction, speed, yaw velocity and lateral acceleration to
calculate the actual direction of travel, then seamlessly
coordinates the the following inputs to maximize vehicle
control and stability for the given road condition/situation.
PSM does this by varying and/or applying any combination
of selective brake application with a change in engine
torque production (via changes in ignition timing, fuel
injection and/or throttle position).
The system combines:
• Anti-lock Braking System (ABS)
• Automatic Brake Differential (ABD)
• Automatic Slip Regulation (ASR)
• Electronic Brake Force Distribution (EBV)
• Engine Drag Torque Control (EDC)
• Dynamic Driving Control (DDC)
Components of the PSM System:
1 - Wheel Speed Sensor
2 - Yaw Sensor
3 - Lateral Acceleration Sensor
4 - Steering Angle Sensor
5 - Priming Pump with Brake Pressure Sensor
6 - Hydraulic Unit
7 - PSM Control Unit
8 - PSM Switch
9 - Motronic Control Unit
Yaw Sensor
Yaw is the rotation of the vehicle around a vertical axis.
The yaw sensor sends an analog voltage signal to the
PSM control unit for the yaw speed and direction of
rotation of the vehicle, and is located under the right-front
passenger seat.
Lateral Acceleration Sensor
The lateral acceleration sensor provides the PSM control
unit with an input signal that corresponds to the degree of
lateral acceleration (G-forces) acting on the vehicle. The
sensor element combines a Hall-effect sensor and a
damped spring/mass.
The lateral acceleration sensor is mounted longitudinally
on the center console.
Wheel Speed Sensors
The wheel speed sensors are located on the front and rear
wheel carriers. PSM uses the same DF 6 type inductive
sensors as previous ABS systems.
Steering Angle Sensor
The steering angle sensor is mounted at the bottom of the
steering column, in front of the flexible coupling. It utilizes
two potentiometers to determine steering angle and rate
of steering change.
The steering angle sensor supplies PSM with a signal for
the steering angle of the front wheels (related to the
driver's desired direction of travel). This signal is used in
the PSM control unit, combined with the calculation of the
driving speed, to calculate the nominal driving behavior of
the vehicle with reference to its lateral dynamics. The
sensor is a non-contact digital magnetic sensor.
Steering angle values between -720° and +720° are
measured with both rough and a fine systems. The sensor
does not have a defined zero position. The position for
"straight ahead" direction of travel must be programmed
with the PIWIS Tester (after taking vehicle readings, installation
of a new sensor, accident repairs etc.). During this
learning process, be sure that the vehicle is in the "straight
ahead" direction of travel (see Technical Manual).
Brake Pressure Sensor
Brake system hydraulic pressure is measured by the brake
pressure sensor. The sensor is located on the priming
pump and senses pressure in the front brake circuit. If
stability management is required during braking, the PSM
control unit uses the brake pressure sensor signal to
modify its calculations.
Brake Light Switch
When the brakes are applied, signals from two brake light
switch contacts (Normally Open and Normally Closed) are
received and evaluated by the PSM control unit. Two
signals are required in order to ensure that actuation of
the brake light switch is detected, and to supply the
control unit with a switch signal if a switch fails.
If brakes are applied during ASC operation, ASC is
stopped immediately so that ABS operation can be
initiated. If DDC is operating, these signals are processed
in addition to the brake pressure signal.
Parking Brake Warning Light Switch
If the driver pulls on the handbrake, the parking brake
warning light switch contact is closed and a ground signal
is sent to pin 76 of the PSM control unit. When the signal
from the parking brake warning light switch is present,
EDC operation is not permitted to prevent excessive
increase in torque at the drive wheels.
Priming Pump
Brake system hydraulic pressure at the wheels must be
adequate and must change rapidly for correct regulation
of driving dynamics. Low temperatures can increase fluid
viscosity and can cause problems.
PSM 5.3 Hydraulics
To ensure adequate fluid delivery from the return pump under
all conditions, the priming pump is switched ON whenever
DDC is in operation. When DDC is active, the priming
pump is switched ON and draws brake fluid from the fluid
reservoir. The intake and switching valves in the hydraulic
unit are actuated and open. From the HE connection, pressure
is generated upstream of the return pump in the front
axle circuit via intake valve (9).
From the HZ connection, the same pressure is supplied to
the pushrod circuit of the master brake cylinder. This
pressure is available at intake valve (6) and the return
pump for the rear axle circuit. The floating piston in the
master brake cylinder acts as a balance so that the same
pressure is applied upstream of the return pump for the
front and rear axle.
In the master brake cylinder pushrod circuit, a throttle
valve (modified central valve) is connected to the
expansion tank. The throttle valve ensures that excess
brake fluid flows into the reservoir and that a certain
pressure is produced. The priming pressure is between
10-20 bar (145-290 psi) depending upon temperature.
PSM Control Unit
The rotational speed of the wheels, steering angle, yaw
velocity, latitudinal acceleration and the brake pressure in
the master brake cylinder are registered and processed in
the PSM control unit. The control unit is connected to the
engine control module via a CAN data bus (or the
transmission management on Tiptronic). This digital
connection allows rapid data exchange between the PSM,
DME and Tiptronic control units.
The control module is continuously supplied with current
data concerning engine torque, accelerator pedal position
and gearbox transmission ratios (on Tiptronic version). The
yaw velocity and lateral acceleration sensors detect the
forces which want to turn the vehicle around its center of
gravity. Using these inputs, it is possible to calculate the
longitudinal and lateral force on the wheels.
If these values exceed certain thresholds, the
corresponding solenoid valves and the return pump in the
hydraulic unit are activated to alter the braking pressure
on one or more wheels. Commands are simultaneously
forwarded via the CAN data bus to the engine control and
transmission control modules (on Tiptronic). To reduce
drive torque, throttle position and ignition timing are
altered, and, if necessary, gear shifting is triggered or
prevented.
PSM Operation
A “PSM-OFF” switch is located in the center console. If
PSM is deactivated, the ABS and ABD functions are maintained
over the entire speed range. For safety reasons,
the driving dynamics control system is temporarily reactivated
during brake pedal operation.
Normal Mode
In normal mode there are no driving conditions which
require control. All solenoid valves in the hydraulic unit are
in the default position and are de-energized. The system is
ready for braking. This operating mode is also used in the
event of faults. The drive torque control system is not
activated.
ABS Control Mode
The control unit recognizes from the wheel rotation signals
that ABS is needed, and the corresponding solenoid valves
in the hydraulic unit are activated. The solenoid valves in
the hydraulic unit for the front and rear axles are activated
individually (4-channel control system).
ABD and ASC
With PSM, longitudinal dynamics control during
acceleration is similar to ABS/TC 5.3 traction control.* The
implementation of E-throttle improves torque control.
If a difference in wheel speed is detected at the rear
wheels, braking pressure is increased on the spinning
wheel via the ABD function. This transfers drive torque to
the other rear wheel. If both wheels start to spin, the DME
control unit closes the throttle until engine torque is sufficiently
reduced. Ignition and fuel injection can also be influenced
in order to dramatically reduce the engine torque.
*ABS/TC 5.3 (4-channel)
ABS/TC 5.3 is a 4-channel system which adds Traction
Control (TC) functionality. TC is a combination of ABD and
ASR (Automatic Slip Regulation) functions. ASR reduces
engine torque if both rear wheels begin to slip during
acceleration. It works over the entire vehicle speed range.
When TC is activated, an indicator light in the instrument
cluster illuminates.
The TC function can be deactivated by the “TC OFF”
switch located in the center console. ABD remains active
up to 62 mph (100 km/h). Over this speed it behaves like a
conventional differential.
ABD is a type of traction assistance which applies the
brakes to a slipping wheel on acceleration in order to
transfer torque to the opposite wheel. ABD works in
conjunction with the new ABS/5 brake system. ABD is
active up to 45 mph (72 km/h).
The ABS/ABD control unit receives throttle angle input
from the DME control unit. ABD becomes active when
throttle angle >2%. When throttle angle >10%, ABD
braking is limited to approx. 10%.
ABD is one component of the Porsche Stability
Management system, to be discussed later in this
section.
Engine Drag Torque Control (EDC)
Engine drag torque control (EDC) prevents excessive
traction slippage of the driving wheels during deceleration
(trailing throttle). The wheel speed sensor signals on the
front and rear wheels are compared. If engine braking
causes the rear wheels to slip excessively, the throttle is
opened slightly in order to achieve optimum friction
between the road and the tires.
Dynamic Driving Control (DDC)
Dynamic Driving Control (DDC) compares driver inputs with
what the vehicle is actually doing and intervenes if
necessary.
The PSM control unit receives inputs for desired driving
direction, speed and acceleration. These driver inputs are
compared with the actual direction of travel of the vehicle.
Signals from the yaw sensor, lateral acceleration sensor
and wheel speed sensors provide information for the
vehicle's rotational speed around the vertical axis (yawangle
velocity), and wheel slip.
If a deviation between the intended and actual direction of
travel results from oversteering or understeering,
opposing torque (yaw-torque) is generated by braking the
wheels on one side of the vehicle. The vehicle is held in
the desired driving direction, provided this is possible
under the given physical conditions (road friction factors).
If braking functions are not sufficient to stabilize the
vehicle, then engine torque is reduced. Initially, ignition
timing is adjusted, followed by throttle control. Fuel
injection can also be modified to greatly reduce engine
torque.
On vehicles with Tiptronic S, gear shifting is
controlled so that changes in wheel torque do not
destabilize the vehicle.
Note:
When PSM intervenes, brake pedal pulsation and
movement may be present.
PSM Diagnosis
All components such as sensors, solenoid valves, return
pump, priming pump and brake light switches, and all
functions, are monitored by the control unit. If a fault is
detected, the ABS or PSM systems are deactivated immediately
after a control function has ended. The fault is
stored in fault memory.
The Porsche PIWIS Tester can be used to read and erase
DTC memory. Further functions such as actuator
selection, switching inputs and system testing are also
possible. These functions are described in the relevant
Technical Manual.
Porsche Stability Management 5.7 (PSM)
Porsche Stability Management (PSM) 5.7 was introduced
in 2001 on the 911 Turbo (996). This system is a revision
to PSM 5.3. Several system components have been
consolidated, and the mechanical brake proportioning
valve is replaced with electronic brake force distribution
(EBV).
Integrated Yaw Rate/Lateral Acceleration Sensor
The yaw rate and lateral acceleration sensors have been
combined into one unit. The previous system had a
separate yaw sensor under the passenger seat and a
lateral acceleration sensor in the center console. The integrated
yaw rate/lateral acceleration sensor is located in
the center console.
The integrated yaw rate/lateral acceleration sensor
provides the PSM control unit with an input signals that
correspond to the degree of lateral acceleration (G-forces)
acting on the vehicle, and also the yaw velocity to
determine the degree of regulation required to maintain
stability.
Brake Pressure Sensor
The brake pressure sensor is mounted on the hydraulic
unit in the front axle circuit on PMS 5.7 systems, instead
of on the priming pump as on PSM 5.3 systems. The
brake pressure sensor function is unchanged.
Hydraulic Unit
On PSM 5.7, the hydraulic unit incorporates the control
module, pump and solenoid valve relay, solenoid valves
and pump in one unit.
Linear Technology Solenoid Valves
The PSM 5.7 hydraulic units use new linear technology
solenoid valves. The new valves can have intermediate
flow positions and are not simply fully opened or closed.
Also, the rate of valve opening and closing can be
controlled. With the “open again slowly” feature, the
pressure increase in low friction conditions can be applied
more gradually. Vehicle yaw moments do not build up due
to the gradual pressure increase. This is particularly beneficial
when braking on icy roads.
Active Wheel Speed Sensor
PSM 5.7 phased-in a new active wheel speed sensor (DF
11 type). This sensor has a Hall element and an IC
(Integrated Circuit).
This technology not only determines the wheel speed, but
also the direction of rotation, wheel stop, and signal
quality.
Important:
Measuring active sensor resistance can destroy the
sensor. Do not subject the wheel bearing to strong
magnetic fields.
Porsche Stability Management 5.3 (PSM)
Porsche Stability Management (PSM) 5.3 was introduced
on the 1999 Carrera 4 (996). PSM 5.3 determines
direction, speed, yaw velocity and lateral acceleration to
calculate the actual direction of travel, then seamlessly
coordinates the the following inputs to maximize vehicle
control and stability for the given road condition/situation.
PSM does this by varying and/or applying any combination
of selective brake application with a change in engine
torque production (via changes in ignition timing, fuel
injection and/or throttle position).
The system combines:
• Anti-lock Braking System (ABS)
• Automatic Brake Differential (ABD)
• Automatic Slip Regulation (ASR)
• Electronic Brake Force Distribution (EBV)
• Engine Drag Torque Control (EDC)
• Dynamic Driving Control (DDC)
Components of the PSM System:
1 - Wheel Speed Sensor
2 - Yaw Sensor
3 - Lateral Acceleration Sensor
4 - Steering Angle Sensor
5 - Priming Pump with Brake Pressure Sensor
6 - Hydraulic Unit
7 - PSM Control Unit
8 - PSM Switch
9 - Motronic Control Unit
Yaw Sensor
Yaw is the rotation of the vehicle around a vertical axis.
The yaw sensor sends an analog voltage signal to the
PSM control unit for the yaw speed and direction of
rotation of the vehicle, and is located under the right-front
passenger seat.
Lateral Acceleration Sensor
The lateral acceleration sensor provides the PSM control
unit with an input signal that corresponds to the degree of
lateral acceleration (G-forces) acting on the vehicle. The
sensor element combines a Hall-effect sensor and a
damped spring/mass.
The lateral acceleration sensor is mounted longitudinally
on the center console.
Wheel Speed Sensors
The wheel speed sensors are located on the front and rear
wheel carriers. PSM uses the same DF 6 type inductive
sensors as previous ABS systems.
Steering Angle Sensor
The steering angle sensor is mounted at the bottom of the
steering column, in front of the flexible coupling. It utilizes
two potentiometers to determine steering angle and rate
of steering change.
The steering angle sensor supplies PSM with a signal for
the steering angle of the front wheels (related to the
driver's desired direction of travel). This signal is used in
the PSM control unit, combined with the calculation of the
driving speed, to calculate the nominal driving behavior of
the vehicle with reference to its lateral dynamics. The
sensor is a non-contact digital magnetic sensor.
Steering angle values between -720° and +720° are
measured with both rough and a fine systems. The sensor
does not have a defined zero position. The position for
"straight ahead" direction of travel must be programmed
with the PIWIS Tester (after taking vehicle readings, installation
of a new sensor, accident repairs etc.). During this
learning process, be sure that the vehicle is in the "straight
ahead" direction of travel (see Technical Manual).
Brake Pressure Sensor
Brake system hydraulic pressure is measured by the brake
pressure sensor. The sensor is located on the priming
pump and senses pressure in the front brake circuit. If
stability management is required during braking, the PSM
control unit uses the brake pressure sensor signal to
modify its calculations.
Brake Light Switch
When the brakes are applied, signals from two brake light
switch contacts (Normally Open and Normally Closed) are
received and evaluated by the PSM control unit. Two
signals are required in order to ensure that actuation of
the brake light switch is detected, and to supply the
control unit with a switch signal if a switch fails.
If brakes are applied during ASC operation, ASC is
stopped immediately so that ABS operation can be
initiated. If DDC is operating, these signals are processed
in addition to the brake pressure signal.
Parking Brake Warning Light Switch
If the driver pulls on the handbrake, the parking brake
warning light switch contact is closed and a ground signal
is sent to pin 76 of the PSM control unit. When the signal
from the parking brake warning light switch is present,
EDC operation is not permitted to prevent excessive
increase in torque at the drive wheels.
Priming Pump
Brake system hydraulic pressure at the wheels must be
adequate and must change rapidly for correct regulation
of driving dynamics. Low temperatures can increase fluid
viscosity and can cause problems.
PSM 5.3 Hydraulics
To ensure adequate fluid delivery from the return pump under
all conditions, the priming pump is switched ON whenever
DDC is in operation. When DDC is active, the priming
pump is switched ON and draws brake fluid from the fluid
reservoir. The intake and switching valves in the hydraulic
unit are actuated and open. From the HE connection, pressure
is generated upstream of the return pump in the front
axle circuit via intake valve (9).
From the HZ connection, the same pressure is supplied to
the pushrod circuit of the master brake cylinder. This
pressure is available at intake valve (6) and the return
pump for the rear axle circuit. The floating piston in the
master brake cylinder acts as a balance so that the same
pressure is applied upstream of the return pump for the
front and rear axle.
In the master brake cylinder pushrod circuit, a throttle
valve (modified central valve) is connected to the
expansion tank. The throttle valve ensures that excess
brake fluid flows into the reservoir and that a certain
pressure is produced. The priming pressure is between
10-20 bar (145-290 psi) depending upon temperature.
PSM Control Unit
The rotational speed of the wheels, steering angle, yaw
velocity, latitudinal acceleration and the brake pressure in
the master brake cylinder are registered and processed in
the PSM control unit. The control unit is connected to the
engine control module via a CAN data bus (or the
transmission management on Tiptronic). This digital
connection allows rapid data exchange between the PSM,
DME and Tiptronic control units.
The control module is continuously supplied with current
data concerning engine torque, accelerator pedal position
and gearbox transmission ratios (on Tiptronic version). The
yaw velocity and lateral acceleration sensors detect the
forces which want to turn the vehicle around its center of
gravity. Using these inputs, it is possible to calculate the
longitudinal and lateral force on the wheels.
If these values exceed certain thresholds, the
corresponding solenoid valves and the return pump in the
hydraulic unit are activated to alter the braking pressure
on one or more wheels. Commands are simultaneously
forwarded via the CAN data bus to the engine control and
transmission control modules (on Tiptronic). To reduce
drive torque, throttle position and ignition timing are
altered, and, if necessary, gear shifting is triggered or
prevented.
PSM Operation
A “PSM-OFF” switch is located in the center console. If
PSM is deactivated, the ABS and ABD functions are maintained
over the entire speed range. For safety reasons,
the driving dynamics control system is temporarily reactivated
during brake pedal operation.
Normal Mode
In normal mode there are no driving conditions which
require control. All solenoid valves in the hydraulic unit are
in the default position and are de-energized. The system is
ready for braking. This operating mode is also used in the
event of faults. The drive torque control system is not
activated.
ABS Control Mode
The control unit recognizes from the wheel rotation signals
that ABS is needed, and the corresponding solenoid valves
in the hydraulic unit are activated. The solenoid valves in
the hydraulic unit for the front and rear axles are activated
individually (4-channel control system).
ABD and ASC
With PSM, longitudinal dynamics control during
acceleration is similar to ABS/TC 5.3 traction control.* The
implementation of E-throttle improves torque control.
If a difference in wheel speed is detected at the rear
wheels, braking pressure is increased on the spinning
wheel via the ABD function. This transfers drive torque to
the other rear wheel. If both wheels start to spin, the DME
control unit closes the throttle until engine torque is sufficiently
reduced. Ignition and fuel injection can also be influenced
in order to dramatically reduce the engine torque.
*ABS/TC 5.3 (4-channel)
ABS/TC 5.3 is a 4-channel system which adds Traction
Control (TC) functionality. TC is a combination of ABD and
ASR (Automatic Slip Regulation) functions. ASR reduces
engine torque if both rear wheels begin to slip during
acceleration. It works over the entire vehicle speed range.
When TC is activated, an indicator light in the instrument
cluster illuminates.
The TC function can be deactivated by the “TC OFF”
switch located in the center console. ABD remains active
up to 62 mph (100 km/h). Over this speed it behaves like a
conventional differential.
ABD is a type of traction assistance which applies the
brakes to a slipping wheel on acceleration in order to
transfer torque to the opposite wheel. ABD works in
conjunction with the new ABS/5 brake system. ABD is
active up to 45 mph (72 km/h).
The ABS/ABD control unit receives throttle angle input
from the DME control unit. ABD becomes active when
throttle angle >2%. When throttle angle >10%, ABD
braking is limited to approx. 10%.
ABD is one component of the Porsche Stability
Management system, to be discussed later in this
section.
Engine Drag Torque Control (EDC)
Engine drag torque control (EDC) prevents excessive
traction slippage of the driving wheels during deceleration
(trailing throttle). The wheel speed sensor signals on the
front and rear wheels are compared. If engine braking
causes the rear wheels to slip excessively, the throttle is
opened slightly in order to achieve optimum friction
between the road and the tires.
Dynamic Driving Control (DDC)
Dynamic Driving Control (DDC) compares driver inputs with
what the vehicle is actually doing and intervenes if
necessary.
The PSM control unit receives inputs for desired driving
direction, speed and acceleration. These driver inputs are
compared with the actual direction of travel of the vehicle.
Signals from the yaw sensor, lateral acceleration sensor
and wheel speed sensors provide information for the
vehicle's rotational speed around the vertical axis (yawangle
velocity), and wheel slip.
If a deviation between the intended and actual direction of
travel results from oversteering or understeering,
opposing torque (yaw-torque) is generated by braking the
wheels on one side of the vehicle. The vehicle is held in
the desired driving direction, provided this is possible
under the given physical conditions (road friction factors).
If braking functions are not sufficient to stabilize the
vehicle, then engine torque is reduced. Initially, ignition
timing is adjusted, followed by throttle control. Fuel
injection can also be modified to greatly reduce engine
torque.
On vehicles with Tiptronic S, gear shifting is
controlled so that changes in wheel torque do not
destabilize the vehicle.
Note:
When PSM intervenes, brake pedal pulsation and
movement may be present.
PSM Diagnosis
All components such as sensors, solenoid valves, return
pump, priming pump and brake light switches, and all
functions, are monitored by the control unit. If a fault is
detected, the ABS or PSM systems are deactivated immediately
after a control function has ended. The fault is
stored in fault memory.
The Porsche PIWIS Tester can be used to read and erase
DTC memory. Further functions such as actuator
selection, switching inputs and system testing are also
possible. These functions are described in the relevant
Technical Manual.
Porsche Stability Management 5.7 (PSM)
Porsche Stability Management (PSM) 5.7 was introduced
in 2001 on the 911 Turbo (996). This system is a revision
to PSM 5.3. Several system components have been
consolidated, and the mechanical brake proportioning
valve is replaced with electronic brake force distribution
(EBV).
Integrated Yaw Rate/Lateral Acceleration Sensor
The yaw rate and lateral acceleration sensors have been
combined into one unit. The previous system had a
separate yaw sensor under the passenger seat and a
lateral acceleration sensor in the center console. The integrated
yaw rate/lateral acceleration sensor is located in
the center console.
The integrated yaw rate/lateral acceleration sensor
provides the PSM control unit with an input signals that
correspond to the degree of lateral acceleration (G-forces)
acting on the vehicle, and also the yaw velocity to
determine the degree of regulation required to maintain
stability.
Brake Pressure Sensor
The brake pressure sensor is mounted on the hydraulic
unit in the front axle circuit on PMS 5.7 systems, instead
of on the priming pump as on PSM 5.3 systems. The
brake pressure sensor function is unchanged.
Hydraulic Unit
On PSM 5.7, the hydraulic unit incorporates the control
module, pump and solenoid valve relay, solenoid valves
and pump in one unit.
Linear Technology Solenoid Valves
The PSM 5.7 hydraulic units use new linear technology
solenoid valves. The new valves can have intermediate
flow positions and are not simply fully opened or closed.
Also, the rate of valve opening and closing can be
controlled. With the “open again slowly” feature, the
pressure increase in low friction conditions can be applied
more gradually. Vehicle yaw moments do not build up due
to the gradual pressure increase. This is particularly beneficial
when braking on icy roads.
Active Wheel Speed Sensor
PSM 5.7 phased-in a new active wheel speed sensor (DF
11 type). This sensor has a Hall element and an IC
(Integrated Circuit).
This technology not only determines the wheel speed, but
also the direction of rotation, wheel stop, and signal
quality.
Important:
Measuring active sensor resistance can destroy the
sensor. Do not subject the wheel bearing to strong
magnetic fields.
Last edited by pete95zhn; Apr 7, 2013 at 04:41 AM.
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If you have PSM off with the dash button, PSM will be off under acceleration but it will turn itself back on under braking. This is why you could bounce off the rev limiter with the tires spinning to your hearts content. To oversimplify it, PSM off with the button = PSM off under acceleration, PSM on under braking. This is why PSM off still sux at the track because you can't effectively trail brake....
All I am posting is my real world experience, I've read on here all sorts of things about PSM that I've not experienced. We spend the entire day literally trail braking every turn as you had to do that to initiate the slides. PSM on it was not possible to do anything as its very agressive especially on the ice.
Here's an interesting writeup
http://www.deter.com/porsche/PSM.html
From the owners manual
When PSM is off, the vehicle is stabilized as soon as one of the two front wheels enters the ABS control range.– When PSM is off and Sport mode is on, the vehicle is stabilized as soon as both front wheels enter the ABS control range
Lots of differing information, my real world experience doesnt match up. PSM is an excellent system to keep the driver safe. On the icy track you just could do nothing to loose control with it on. With it turned off I have never experienced it re-activating, psm is very obvious when it comes on.
Last edited by Basic; Apr 7, 2013 at 11:44 AM.