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

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

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  1. 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

  2. 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

  3. 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

  4. Types of EGR: • Integral Backpressure • With or without PCM • Internal Modulator controls EGR flow based on positive or negative exhaust pulses

  5. 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.

  6. 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

  7. Types of EGR: • Linear Solenoid EGR • No vacuum control • PCM PWM • Improved accuracy • Faster response (10X) • Improved diagnostics

  8. Types of EGR: • Linear EGR schematic 5 wire: 2 for solenoid 3 for sensor

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

  10. Types of EGR: • GM Digital Schematic

  11. 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.

  12. 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

  13. 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

  14. Various EGR controls

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