Acura NSX 1991 Manual page 517

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Anti-lock Brake System (ABS) Description
Features/Construction/Operation
General
In a conventional brake system, if the brake pedal is depressed excessively, the wheels can lock before the vehicle
comes to a stop. In such a case, the stability of the vehicle is reduced if the rear wheels are locked, and maneuverabily of
the vehicle is reduced if the front wheels are locked, creating an extremely unstable condition.
The Anti-lock Brake System (ABS) modulates the pressure of the brake fluid applied to each caliper, thereby preventing
the locking of the wheels, whenever the wheels are likely to be locked due to excessive braking. It then restores normal
hydraulic pressure when there is no longer any possibility of wheel locking.
4-Channel Anti-lock Brake System (ABS) Features
• Increased braking stability can be achieved regardless of changing driving conditions.
• The maneuverability of the vehicle is improved as the system prevents the front wheels from locking.
• When the anti-lock brake system goes into action, kickback is felt on the brake pedal.
• The anti-lock brake system is equipped with a self-diagnosis function. When an abnormality is detected, the ABS in-
dicator light comes on. The location of the abnormality can be diagnosed from the frequency of the system indicator
light display blinks.
• This system has individual control of the front and rear wheels. Braking force is controlled on each of the four wheels
independently, resulting in optimum braking effects on the four wheels.
The system has a fail-safe function that allows normal braking if there's a problem with the anti-lock brake system.
Construction
In addition to the conventional braking system, the anti-lock brake system is composed of: gear pulsers attached to the
rotating part of individual wheels; wheel sensors, which generate pulse signals in correspondence to the revolution of the
gear pulsers; ABS control unit, which controls the working of the anti-lock brake system by performing calculations bas-
ed on the signals from the individual wheel sensors and the individual switches; a modulator unit, which adjusts the
hydraulic pressure applied to each caliper on the basis of the signals received from the ABS control unit; an accumulator,
in which high-pressure brake fluid is stored; a pressure switch, which detects the pressure in the accumulator and
transmits signals to the ABS control unit; a power unit, which supplies the high-pressure working fluid to the ac-
cumulator by means of a pump; a motor relay for driving the power unit; a fail-safe relay, which cuts off the solenoid
valve ground circuit when the fail-safe device is at work; and, an ABS indicator light.
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