Limiteur de fumée

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

The smoke limiter is a fundamental diesel ECU function that prevents excessive black smoke (soot) by limiting fuel injection quantity relative to available air mass. It protects emissions compliance and DPF longevity.

Vue d'ensemble

When fuel exceeds available oxygen, incomplete combustion produces visible smoke. The ECU continuously calculates maximum allowable IQ based on measured airflow, preventing the engine from running overly rich.

Controlled Signals

  • Air mass (MAF sensor)
  • Boost pressure
  • Injection quantity request
  • Engine speed
  • Intake temperature

Maps Involved

  • Smoke Limiter Maps (IQ max vs air mass)
  • Altitude Correction Maps
  • Temperature Correction Maps
  • Transient Smoke Maps

Logic Sequence

Air Mass Measurement → Smoke Limit Calculation
         ↓
Compare to Requested IQ
         ↓
If IQ > Smoke Limit → Clamp IQ
         ↓
Final IQ to Injectors

Calibration Objectives

  • Prevent visible smoke under all conditions
  • Allow maximum safe fueling for performance
  • Protect DPF from soot overload

Calibration Strategy

  • Raise smoke limiter only after increasing airflow (boost)
  • Never raise smoke limiter as first tuning step
  • Monitor opacity during WOT pulls

Diagnostics

  • Black smoke under acceleration
  • Rapid DPF clogging
  • MAF sensor drift or contamination

Best Practices

  • Smoke limiter protects the engine — respect it
  • Clean MAF sensor regularly on tuned vehicles
  • Verify AFR with wideband during tuning

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