Porsche 911 GT3R 2010 Technical Manual page 129

10.10.2. Mea suring vehicle dynamics
The ABS allows the driver to brake near the locking limit of the wheels. By
preventing the locking of a wheel the systems ensures braking in the
optimum deceleration range.
T o determine the vehicle's driving state the following data is permanently
measured:
 Brake pressure at each wheel
 Brake pressure of the front brake circuit
Lateral acceleration

 Longitudinal acceleration
 Yaw rate
 Each wheel speed
To prevent the locking of a wheel the wheel speeds and brake pressures
of each wheel are measured. The system calculates the corresponding
wheel accelerations. These values are compared with the expected
optimum wheel accelerations.
In case the measured values differ from the calculated optimum values
the ABS becomes active. The brake pressure at each wheel is corrected
until the wheel slip is back in the optimum range to be able to brake at the
highest deceleration rate. The comparison of the measured and the
calculated values is being carried out through the whole brake phase and
for each wheel individually.
To reduce the brake pressure at a wheel an electrical scavenge pump
returns brake fluid via the pressure reservoir of the hydraulic control unit
to the corresponding master brake cylinder. This return can be noted
acoustically by a pulsating brake pedal.
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