2004 PORSCHE CAYENNE engine

178
Driving and Driving Safety Selecting off-road driving program
fPush rocker switch forward .
The vehicle becomes one step more suitable
for off-road driving.
Selecting on-road driving program
fPull rocker switch to the rear .
The vehicle becomes one step more suitable
for on-road driving.
Once the driving program has been selected, the
rocker switch springs back to home position.
A-High Range on-road driving program
(without reduction)
B-Low Range off-road driving program
(with reduction)
C-Center differential lock in Low Range is fully engaged
D-Rear differential lock in Low Range is fully engagedDisplay of the selected driving program
The selected driving program is displayed by light-
emitting diodes next to the rocker switch (illustra-
tion).
The corresponding indicator lights on the instru-
ment panel and light-emitting diodes beside the ro-
cker switch flash several times during the shif-
ting process.Tip on driving center differential lock
When the center differential lock C is fully enga-
ged, there is no longer any speed difference bet-
ween the front and rear axles. If, for example, both
wheels at the front axle lose traction on an icy
road or soft surface, the rigidly linked drive wheels
will permit the car to continue moving neverthe-
less.
Tip on driving rear-differential lock
When the rear differential lock D is fully engaged,
there is no longer any speed difference between
the two rear wheels. If, for example, one drive
wheel at the rear axle loses traction on an icy road
or soft surface, the rigidly linked drive wheels will
permit the car to continue moving nevertheless.
Note on operation
The rear differential lock can be engaged only
while the engine is running.
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Driving and Driving Safety
179
Note on operation
If the Low Range indicator light next to the rocker
switch flashes rapidly after the ignition is swit-
ched on, there is a fault in the shifting system.
fHave the vehicle checked immediately.
Please consult an authorized Porsche dealer.
If the Low Range indicator light next to the rocker
switch flashes when you attempt to operate
rocker switch, then at least one condition for shif-
ting has not been met:
Vehicles with manual transmission
– Vehicle is not stationary.
– Brake is not pressed.
– Gearshift lever in not in neutral.
Vehicles with Tiptronic S
– Vehicle has exceeded or gone below the limit
speed.
– Tiptronic selector lever is not in position N.
Sport ModeFunction
The sports exhaust system is switched on and a
sportier car set-up is obtained when Sport mode
is switched on.
Interventions by the Porsche control systems are
intentionally shifted towards greater agility and
driving performance.
– PASM (Porsche Active Suspension Manage-
ment) is automatically changed to Sport mode,
resulting in a stiffer suspension setup.– PDCC (Porsche Dynamic Chassis Control) is
automatically set to Sport mode, and this
further reduces the roll tendency of the
vehicle.
– The air suspension automatically changes to
the low level setting.
– The Tiptronic S transmission changes to a
sportier shift strategy.
The gear-changing points are shifted to higher
speed ranges. Upward shifts are initiated later,
and deceleration shifts are performed earlier.
The vehicle moves off in 1st gear.
– The electronic accelerator pedal reacts
sooner, and the engine is more responsive to
throttle inputs.
– Sporty engine tuning is activated.
fFor further information:
Please see the chapter “PORSCHE ACTIVE
SUSPENSION MANAGEMENT (PASM)” on
Page 193.
fPlease see the chapter “PORSCHE DYNAMIC
CHASSIS CONTROL (PDCC)” on Page 194.
Low Range indicator light
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Driving and Driving Safety
181
Power-Transmission and Running-Gear Control SystemsA complex interconnection of all control systems acting in power transmission and in the running gear has been realized in your Porsche.
All control systems have been linked with the aim of combining the best possible driving performance with maximum safety.
The following systems are involved:
System/designation Scope
PTM
Porsche Traction Management– Full-time all-wheel drive
– Electronically controlled center differential lock
– Automatic brake differential (ABD)
– Traction control system (TCS)
– Reduction gear/Low Range
PTM Plus
Porsche Traction ManagementIn addition to the PTM features, PTM Plus also includes:
– Electronically controlled rear differential lock
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)
Air suspension
with level control and height adjustment– Fully load bearing air spring struts with integral shock absorbers
– Air supply system with pressure accumulator
PAS M
Porsche Active Suspension Management– Shock absorber system with adaptive, continuous shock absorber control
PDCC
Porsche Dynamic Chassis Control– Active chassis control system to stabilize roll tendency of vehicle body when driving
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182
Driving and Driving Safety
Warning!
In spite of the advantages of PTM or four-wheel dri-
ve, 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 situ-
ation.
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 PTM or four-wheel drive.
Risks of accident due to inappropriate speed
cannot be reduced by PTM.Porsche Traction Management (PTM)Porsche Traction Management is a full-time all-
wheel control system designed to influence the
longitudinal and lateral dynamics. It is closely
linked with the Porsche Stability Management
(PSM) system:
PTM ensures the best possible power distribution
to the four driven wheels at the front and rear
axles. The system realizes this optimal traction by
intervening in the lock control function of the trans-
fer case and rear differential. PTM is active at all
times and, unlike the PSM, cannot be switched off.Advantages of PTM
– Obvious improvement in traction, driving
stability and steering ability of the car.
– Vehicle is more manageable when driven at its
performance limits.
– Improved straight-ahead tracking and stability.
– The aforementioned features allow for a
sportier setup of the running gear.
– The TCS and ABD provide even better traction
for all wheels.
Full-time all-wheel drive
With the four-wheel drive, the drive power is
variably distributed to the front and rear wheels.
Power distribution and wheel speed compensation
between the front and rear axles is realized with a
transfer box.
Distribution of the drive power depends on the
wheel speed difference between the two axles.
The transfer box always controls power distribu-
tion in such a way that optimal propulsion is achie-
ved, even on an unfavorable road surface.
Full-time four-wheel drive ensures optimal handling
and greater stability.Automatic brake differential (ABD)
The ABD system controls the front and rear axles
separately. If one wheel of an axle starts to spin,
it is braked so that the other wheel on the same
axle can be driven.
The ABD recognizes different driving states, and it
features control strategies adapted to these
states. In situations in which little propulsive power
is required, such as when the car moves off on a
level gravel surface, traction control already
becomes active at low engine speeds. If great
propulsive power is required, e.g. when moving off
on an uphill slope or for rapid acceleration, the
ABD is adapted accordingly.
A special off-road program is used in Low Range
mode.
Traction control system (TCS)
The traction control system prevents the wheels
from spinning by adjusting the engine power,
thereby ensuring good lane-holding ability and a
stable driving behavior.10_Cayenne_21_KW17.book Seite 182 Donnerstag, 9. April 2009 3:33 15

Driving and Driving Safety
183
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 vehi-
cle 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 neces-
sary, PSM additionally influences the engine power
or the gear-changing characteristic of the
Tiptronic in order to stabilize the vehicle.
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184
Driving and Driving Safety 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 begin-
ning 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 sub-
sequent 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 neces-
sary for maximum deceleration at all 4 wheels.
Combined use of PSM and PTM/PTM Plus
In order to ensure optimal stabilization of the ve-
hicle, the center differential lock (PTM) and possib-
ly the rear differential lock (PTM Plus) are also
opened when PSM interventions occur.
Tip on driving
When PSM is switched off, wheel-specific brake in-
terventions and the traction control system (TCS)
are also inactive.
The automatic brake differential (ABD) remains on.Off-road PSM
(PSM in Low Range program)
When Low Range is active, an off-road PSM
specially matched to off-road driving is activated
to enhance traction.
In order to improve driveability on difficult terrain,
the response of the off-road PSM is less sensitive
in the low speed range when the vehicle is opera-
ted in the Low Range off-road driving program.
If the brakes are highly stressed, the automatic
brake differential (ABD) switches itself off to
protect the brakes. It remains deactivated until the
brake system has cooled sufficiently.
Engine drag torque control
In conditions of excessive slip, the engine drag
torque control system prevents all driven wheels
from locking up when the car is passing. This is
also the case for downshifts on a slippery road.
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Driving and Driving Safety
187
Warning light
If the ABS warning lights light up in the instrument
panel and on the multi-purpose display of the
instrument panel while the engine is running, the
ABS has switched off because of a fault.
In this event, the braking system will operate with-
out lock prevention,as in cars without ABS.
fAdapt your driving style to the changed
braking behavior.
fThe ABS must be checked immediately at an
authorized Porsche dealer. This is necessary
in order to prevent the occurrence of further
faults whose effects cannot be defined.
The ABS control unit is adjusted for the approved
tire dimensions.
The use of tires with non-approved dimensions can
lead to different wheel speeds, causing the ABS to
switch off.
Off-road ABS
(ABS in Low Range program)
When Low Range is active, an ABS specially
matched to off-road driving is activated automati-
cally.In the event of braking on loose ground, the per-
missible slip values for ABS braking are increased
so that the off-road braking distance is reduced
(wheels dig into the surface).
If the driver needs to steer, this off-road driving
program is automatically switched off to maintain
steerability.
Hillholder -
moving-off assistant on vehicles with
Tiptronic SIn Tiptronic selector lever positions D and M, the
hillholder function makes it easier to move off
from a standstill on an upward slope when the
engine is running. The driver does not have to
apply the brake.
The hillholder thus makes moving off on slopes
easier.
Danger!
Risk of accident, resulting in serious perso-
nal injury or death.
The vehicle can roll backwards if the Hillhol-
der is switched off.
fAlways apply the footbrake on slopes.Hillholder is not active:
– In Tiptronic selector lever positions N and R
– In the limp-home mode and
– If not all of the wheels are touching the ground
(on difficult terrain, for example).
Warning!
In spite of the advantages of the hillholder func-
tion, it is still the driver’s responsibility to adapt
her/his driving style and maneuvers in line with
situational conditions.
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 the hillholder function.
Driving at the limits should be avoided, e.g., on icy
slopes or on slippery surfaces. In this and similar
cases, the support of the hillholder function is not
guaranteed.
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188
Driving and Driving Safety
Porsche Drive-Off Assistant –
Moving-off assistant on vehicles with
manual transmissionThe Porsche Drive-Off Assistant enables the driver
to move off on upward slopes. The vehicle must
have sufficient road contact to use this feature.
The Porsche Drive-Off Assistant is available for
slopes starting at approximately 5%.
fPlease see the chapter “TRAILER COUPLING”
on Page 230.
Danger!
Risk of accident, resulting in serious perso-
nal injury or death.
When moving off on a slippery surface (e.g.,
on icy or loose surfaces), assistance by the
Porsche Drive-Off Assistant is no longer
assured. In this case, the vehicle could slip.
The limits set by the physics of driving cannot
be overcome, even with the Porsche Drive-
Off Assistant. The responsibility for moving
off on upward slopes is still the driver's,
despite the Porsche Drive-Off Assistant.
fAlways adjust your driving style to the driving
conditions and vehicle load, use the footbrake if necessary.Moving off with Porsche Drive-Off Assistant
1. Hold the vehicle securely with footbrake or
parking brake on the slope.
The engine must be running.
2. Fully depress the clutch pedal.
3. Engage one of the gears used to ascend in the
direction of travel (1st gear or reverse).
4. While keeping the clutch pedal depressed,
release the footbrake or foot-operated parking
brake.
The vehicle is held on the slope.
5. Move off as usual.Note on operation
The Porsche Drive-Off Assistant ceases to func-
tion:
– By shifting to neutral.
– When changing gears.
– If the engine is not running.
Danger!
Risk of accident, resulting in serious perso-
nal injury or death.
If the Porsche Drive-Off Assistant ceases to
function, the vehicle will no longer be held on
a slope.
fHold the vehicle with the footbrake.
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