Catalyst Systems

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

Catalytic converters use precious metal catalysts to convert harmful exhaust gases (CO, HC, NOx) into less harmful substances (CO2, H2O, N2). The ECU manages catalyst temperature and monitors conversion efficiency.

Übersicht

Three-way catalysts (gasoline) require precise stoichiometric AFR. Diesel oxidation catalysts (DOC) handle CO and HC, while SCR handles NOx. Catalyst light-off temperature must be reached quickly after cold start.

Controlled Signals

  • Pre-catalyst lambda sensor
  • Post-catalyst lambda sensor
  • Catalyst temperature (measured or modeled)
  • Catalyst heating strategies

Maps Involved

  • Catalyst Heating Maps (retarded timing, secondary air)
  • Light-off Temperature Targets
  • Efficiency Monitoring Thresholds
  • Lambda Control Maps

Logic Sequence

Cold Start → Catalyst Heating Strategy
         ↓
Monitor Catalyst Temperature Rise
         ↓
Light-off Achieved → Normal Lambda Control
         ↓
Continuous Efficiency Monitoring

Calibration Objectives

  • Fast catalyst light-off
  • Maintain high conversion efficiency
  • Prevent catalyst overheating

Calibration Strategy

  • Catalyst delete requires O2 sensor simulation or deactivation
  • Sports catalysts may require lambda sensor offset
  • Verify AFR control after any exhaust modifications

Diagnostik

  • P0420/P0430 catalyst efficiency below threshold
  • Oxygen sensor response faults
  • Catalyst overtemperature

Best Practices

  • Catalyst removal is illegal for road use
  • Rich running damages catalysts — fix fueling issues promptly
  • High-flow sports cats maintain emissions compliance with better flow

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