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Exhaust Gas Recirculation (EGR ) Lowers Oxides of Nitrogen (NO x) emissions caused by high combustion temps Reduces engi

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Exhaust Gas Recirculation (EGR ) Lowers Oxides of Nitrogen (NO x) emissions caused by high combustion temps Reduces engi - PowerPoint PPT Presentation


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Exhaust Gas Recirculation (EGR ) Lowers Oxides of Nitrogen (NO x) emissions caused by high combustion temps Reduces engine knock (ping) EGR decreases combustion temperatures EGR valve = main element of EGR system Feeds small amounts of exhaust back to the combustion chamber

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Presentation Transcript
slide1

Exhaust Gas Recirculation (EGR)

  • Lowers Oxides of Nitrogen (NOx) emissions caused by high combustion temps
  • Reduces engine knock (ping)
  • EGR decreases combustion temperatures
  • EGR valve = main element of EGR system
  • Feeds small amounts of exhaust back to the combustion chamber
  • This dilutes the air/fuel mixture, combustion temperatures are reduced
  • Valve is open during engine cruise periods
  • EGR activation:
  • Warm engine operation
  • Above idle speed
  • EGR flow calculation
  • PCM looks at readings from:
    • ECT
    • TPS
    • VSS
    • MAP or MAF
    • IGN REF
slide2

The EGR valve opens and closes the passage between the exhaust manifold and intake manifold. Vacuum is used to move the EGR valves.

  • EGR opens and closes a passage between exhaust and intake.
  • EGR valves are opened using:
  • Vacuum (usually ported, may use vacuum control solenoid)
  • Electronic (EGR valve uses solenoid)

Spring

Pintle

Passages

slide3

Types of EGR:

  • Single Diaphragm
  • Used with or without PCM controls
  • When the engine is idling, opening valve should stall the engine
  • Opens fully with about 8” Hg.
  • Used with a thermal vacuum switch and a possible vacuum delay valve.
  • Single diaphragm may be used in an electronically controlled systems
  • Basic standard since 1973
slide4

Types of EGR:

  • Integral Backpressure
  • With or without PCM
  • Internal Modulator controls EGR flow based on positive or negative exhaust pulses
slide5

Types of EGR:

  • External Modulator
  • With or without PCM
  • External Modulator controls EGR flow based exhaust pressure

Vacuum modulation is vital for good driveability and precise NOx control.

slide6

Types of EGR:

  • External sensor
  • PCM commands solenoid (VSV)
  • Sensor reports EGR valve position to PCM
  • May use 2 solenoids (vacuum and vent)

EGR SOLENOID

slide7

Types of EGR:

  • Linear Solenoid EGR
  • No vacuum control
  • PCM PWM
  • Improved accuracy
  • Faster response (10X)
  • Improved diagnostics
slide8

Types of EGR:

  • Linear EGR schematic

5 wire:

2 for solenoid

3 for sensor

slide9

Types of EGR:

  • GM digital
  • No vacuum
  • 3 solenoids, 3 different exhaust ports.
  • Valves may be operated separately or together to control EGR.
slide10

Types of EGR:

  • GM Digital Schematic
slide11

Types of EGR:

  • GM Integrated Electronic
  • Combines vacuum and electronic operation
  • PCM controlled vacuum regulator is built into the top of the EGR valve.
  • PWM signals operate regulator solenoid and control vacuum.
  • Ported vacuum is supplied to the EGR valve assembly.
  • EGR pintle sensor provides feedback to the PCM to verify desired action has occurred.
slide12

Types of EGR:

  • GM EGR solenoid details.
  • PCM controlled PWM
  • PCM regulates the time the EGR is open by regulating solenoid on time (more EGR).
  • Percentage of solenoid on time is the duty cycle:
  • 0% equals no EGR; 100% equals maximum EGR.
  • EGR vacuum switch signals PCM -vacuum present
slide13

High backpressure

Low backpressure

  • External Modulator with PCM controlled vacuum solenoid
  • PCM command opens or closes vacuum solenoid
  • Modulator controls EGR flow based on vacuum & exhaust backpressure
  • Vacuum signal varies through throttle opening