1997 ACURA NSX Service Repair Manual

Operation

1. Ordinary Braking Function

In ordinary brake operations, the cut-off out valve in the modulator is open to transmit the hydraulic pressure from the

master cylinder to the brake calipers via the chamber A and the chamber B.

The chamber C is connected to the reservoir through the outlet valve which is normally open. It is also connected to the

hydraulic pressure source (pump, accumulator, pressure switch, etc.) via the inlet valve which is normally closed. The

chamber D serves as an air chamber. Under these conditions, the pressures of the chambers C and D are maintained at

about the atmospheric pressure, permitting regular braking operations.
Features/Construction/Operation (cont'd)
Anti-lock Brake System (ABS) DescriptionProCarManuals.com

If brake inputs (force exerted on brake pedal) are excessively large and a possibility of wheel locking occurs, the control

unit operates the solenoid valve, closing the outlet valve and opening the inlet valve. As a result, the high pressure is

directed into chamber C, the piston is pushed upward, causing the slide piston to move upward and the cut-off valve to

close.

As the cut-off valve closes, the flow from the master cylinder to the caliper is interrupted, the volume of chamber B, which

is connected to the caliper, increases, and the fluid pressure in the caliper declines.

When both of the two valves, inlet and outlet, are closed (when only the outlet valve is activated) the pressure in the

caliper is maintained constant.

When the possibility of wheel locking ceases, it is necessary to restore the pressure in the caliper. The solenoid valve is

therefore turned off (outlet valve: open, inlet valve closed).

Slide Piston Function

When the vehicle is used on rough roads where the tires sometimes lose adhesion, the anti-lock brake system may func-

tion excessively, causing an excessively large volume of brake fluid to flow into the chamber C. As this occurs, the piston

is moved excessively, resulting in an abnormal loss of pressure in the chamber B. In order to overcome this problem, the

slide piston is kept in the proper position by the spring force to avoid a negative pressure in the chamber B.

Kickback

When anti-lock brake system is functioning, the piston moves upward, the volume of chamber B increases, and the fluid

pressure on the caliper side is reduced. At the same time, the volume of chamber A is reduced and the brake fluid is

returned to the master cylinder. When the brake fluid is pushed back to the master cylinder, the driver can feel the func-

tioning of the anti-lock brake system because the brake pedal is kicked back.ProCarManuals.com

Component LocationsProCarManuals.com

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ABS Control Unit Terminal ArrangementProCarManuals.com

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ABS Control Unit Terminal ArrangementProCarManuals.com

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