EGR System

🧠 Part of the TuningBot ECU Knowledge Base — in-depth documentation on ECU logic, maps, emissions systems and safe calibration methods.

Exhaust Gas Recirculation (EGR) reduces nitrogen oxide (NOx) emissions by recirculating a portion of exhaust gas into the intake manifold. This dilutes the fresh charge with inert gas, lowering peak combustion temperatures.

Panoramica

Modern engines use high-pressure EGR (upstream of turbine) or low-pressure EGR (downstream, after DPF). The ECU modulates EGR valve position based on engine load, RPM, and temperature.

Controlled Signals

  • EGR valve position
  • EGR cooler bypass valve
  • Intake manifold pressure
  • MAF / MAP sensors
  • EGR temperature sensor

Maps Involved

  • EGR Rate Target Maps vs RPM/load
  • EGR Valve Position Maps
  • EGR Cooler Bypass Maps
  • EGR Temperature Limits

Logic Sequence

Operating Conditions → EGR Rate Lookup
         ↓
Temperature / Altitude Corrections
         ↓
EGR Valve Command
         ↓
MAF-based Feedback Verification

Calibration Objectives

  • Minimize NOx emissions
  • Maintain drivability and response
  • Prevent intake contamination

Calibration Strategy

  • EGR delete requires full ECU adaptation to prevent faults
  • Reducing EGR increases NOx but may improve response
  • Monitor intake manifold for carbon buildup

Diagnostica

  • EGR valve position faults
  • EGR flow insufficient/excessive
  • Intake manifold pressure deviation

Best Practices

  • EGR delete is emissions-illegal in most jurisdictions
  • Regular cleaning extends EGR life on stock vehicles

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