The brake booster is designed to create a greater braking force from a minimum pedal effort, using a difference in atmospheric pressure and the engine’s manifold vacuum. It increases the pedal force 2 to 4 times depending on the size of the diaphragm. The brake booster is located between the brake pedal and the master cylinder. When pressure is applied to the brake pedal, pressure is exerted on the booster air valve. With pressure created by the booster the master cylinder is applied. Should the booster malfunction, the normal mechanical braking force of the master cylinder is maintained.
The brake booster consists of the body, booster piston, piston return spring, reaction mechanism, and control valve mechanism. The body is divided into a constant pressure chamber and a variable pressure chamber. The chambers are separated from each other by a diaphragm. The control valve mechanism regulates the pressure inside the variable pressure chamber.