Porsche 911 Carrera - Manual (Page 68)

Four-Wheel Drive
Engine power
With the four-wheel drive, the engine power is
variably distributed to the front and rear wheels.
Power distribution and wheel speed compensation
between the front and rear axles is realised with a
viscous multiple-disc clutch.
Distribution of the engine power is dependent upon
the wheel speed difference between the two axles.
The viscous multiple-disc clutch always delivers
sufficient drive power to the front wheels (approx.
5% to 40%) to ensure optimum traction even on a
poor road surface.
In combination with the Porsche Stability
Management (PSM), four-wheel drive improves
handling and increases driving stability.
Warning!
The increased control that is provided should
not induce you to take greater risks with
your safety. The limits dictated by the laws
of physics cannot be overcome, even with
four-wheel drive. The risk of accidents due
to inappropriate speed cannot be reduced,
even by four-wheel drive. The driver bears the
responsibility for all driving maneuvers.
Adapt your driving style to the prevailing road
and weather conditions.
Obey all traffic laws. Dynamometer testing procedure
Some U.S. states and Canadian provinces conduct
emissions inspection/maintenance testing
involving the use of two-wheel dynamometer. A
two-wheeled dynamometer is a treadmill type
device upon which a single axle of the car, the
driving axle of the vehicle, rotates to simulate
vehicle operation on the road while the vehicle
remains stationary.
The full-time four-wheel drive system of your
vehicle cannot be disabled. Severe damage to
the powertrain can result if tested on a two-wheel
dynamometer.
Warning!
To avoid severe powertrain damage and
a possible unexpected movement of the
vehicle.
Vehicles with four-wheel drive must never be
tested on a two-wheel dynamometer.
Advise the emission station of this warning
before testing the vehicle.
Power measurement
Power measurements on dynamometers are not
approved by Porsche.
66
Controls, Instruments