differential PORSCHE 911 GT2 2008 5.G Information Manual

· 39 · · 38 ·
The 911 GT2 |Drive
The six-speed manual gearbox in
the 911 GT2 is specifically
designed for the high engine
performance. The individual ratios
are carefully matched to the spe-
cific characteristics of the engine.The gear-lever throw is short and
precise, enabling fast and
accurate gearshifts.
A typical feature of the 911 GT2
is the Launch Assistant – for maximum acceleration from a
standing start. The clutch and
accelerator are depressed when
the vehicle is stationary.
When a
boost pressure of approximately
0.9 bar is displayed in the instru-ment
cluster, release the clutchas
quickly as possible and maximum
a
cceleration automatically ensues.
Normally on a turbocharged vehicle
with manual gearbox, the boost
pressure under acceleration from
a standing start is relatively low.
The turbo effect is delayed as
the engine gathers speed and
the boost pressure starts to build.On the 911 GT2, this initial delay
is reduced. While the car is still
stationary, the fuel injection is
modified to help the engine reach
maximum output earlier. The boost
pressure is significantly increased
and the engine readied for a faster
start.
A specially designed traction
control system adapts the acceler-
ation procedure automatically
in the ECU to ensure optimum
traction. The clutch remains
engaged. This reduces load and
prevents high clutch wear. The
power is transmitted directly to
the road via the rear axle.
The gearbox is combined with
a cable linkage and dual-mass fly-
wheel offering added comfort and
precision. The close ratio spread
enables powerful acceleration
within the optimum engine power
band.
Steel baulk rings on gears two to
five ensure a precise gearshift
action even under extreme loads.Cooling is provided by an add-
itional oil-to-water heat exchanger
and spray lubrication. Both of
these features are essential for
durability in endurance racing
conditions.
Other standard features include
a limited-slip differential with
asymmetrical lock factor. Offering
better traction and handling
when exiting a corner, it applies a
higher proportion of drive torque
to the loaded outer rear wheel.
The term ‘asymmetrical’ means
that one lock factor is applied
when cornering under power
(28 %), and another when braking
for a corner (40 %).
Maximum response to minimum effort.
Transmission.

· 51 · · 50 ·The 911 GT2 |
Chassis
Some things never change,
including driver expectations of
a 911 GT2 : sports-oriented
performance, a direct response
and impressive power.
So Porsche Stability Management
(PSM) has been specially adaptedfor the 911 GT2. In addition to
ABS, the package includes two
automatic driver aids: stability
control (SC) and traction control
(TC).
Stability control (SC), which is
responsible for lateral dynamics,uses a range of sensors to moni-
tor the direction, speed, yaw
velocity (speed of rotation around
the vertical axis) and lateral
acceleration of the car. Using
this information, it is possible to
calculate the actual direction of
travel at any given moment. If thecar begins to oversteer or under-
steer, selective braking is applied
on individual wheels to restore con-
trol in critical driving scenarios.
Traction control (TC), with its
integrated ABD (automatic brake
differential), ASR (anti-slip regula-
tion) and EDC (engine drag-torque
control) functions, is responsible
for the longitudinal dynamics of the
car. Configured for sports-oriented
driving, traction control improveshandling under acceleration on
surfaces with inconsistent grip.
It also prevents the rear from
‘stepping out’ if a wheel loses
traction under full power. The
trigger threshold is relatively high,
which means it is rarely employed
in normal dry conditions.
A unique feature of PSM on
the 911 GT2 is that the control
interventions are delayed and
can be disabled completely in
two stages – for deliberate per-
formance handling.
Stage 1 disables the stability con-
trol (SC) via the ‘SC OFF’ switch in
the centre console. In ‘SC OFF’
mode, the control system does
not intervene if the car goes off-
course in the lateral direction,
which means the throttle can
be used to help steer the car.
Traction control (TC) is still active
in this mode.
Stage 2 disables the traction con-
trol as well via the separate
‘SC+TC OFF’ switch, giving the
driver full command of the vehi-
cle. Another unique feature is the fact that stability control
remains disabled in stages 1 and
2 even when the ABS is required
under braking. Specially develop-
ed for the 911 GT2, this revised
system strategy means the car
can also be enjoyed to maximum
effect on the racetrack.
The anti-lock braking system
(ABS 8.0) is integrated in PSM
and remains active, irrespective
of which settings have been
selected. ABS ensures a relatively
short braking distance and thus
enhanced safety.
It’s good to know who’s in control.
Porsche Stability Management (PSM).