Electric Vacuum Pump For Brake Servo Unit – Self-Study Programme 257



Electric Vacuum Pump For Brake Servo Unit - Self-Study Programme 257 PDF

Electric Vacuum Pump For Brake Servo Unit – Self-Study Programme 257 PDF. Cars fitted with a petrol engine in combination with an automatic gearbox which comply with the EU 4 Standard have an electric vacuum pump. This is used for assisting the brake servo unit. In this engine-gearbox combination, the throttle valve is opened particularly wide when the engine is started from cold, as well as when it is idling with a drive position engaged and the brakes applied. This is intended to reduce the pressure drop in intake manifold.

The reasons for this greater opening of the throttle valve is the heating-up phase of the catalytic converter after a cold engine start, as required by the EU 4 emission standard, and compensating for the greater torque friction (resistance in torque converter) which exists under the conditions mentioned above.

Depending on the particular car model, two different versions of the electric vacuum pump are fitted:

  1. open-loop controlled vacuum pump
  2. closed-loop controlled vacuum pump

The Self-Study Programme describes the design and function of new developments.
Please always refer to the relevant service literature for up-to-date inspection, adjustment and repair instructions.

CONTENTS:

Introduction

  • Function of the brake servo unit
  • Design and function of the electric vacuum pump
  • Design and function of the vane pump

Open-loop controlled vacuum pump

  • Open-loop control version
  • Installation position
  • Operating conditions
  • Function diagram

Closed-loop controlled vacuum pump

  • Closed-loop control version
  • Function of pressure sensor
  • Installation position
  • Operating conditions
  • Function diagram

Hysteresis
Self-diagnosis
Test your knowledge

Language: English
Format: PDF
Pages: 20
Size: 1.05 Mb
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