Overboost protection is a critical safety function that prevents excessive turbocharger pressure. When boost exceeds safe thresholds, the ECU reduces torque, opens the wastegate, or cuts fuel to protect engine components.

Overview

Overboost can result from wastegate failure, VGT malfunction, or aggressive tuning. The ECU monitors boost pressure continuously and responds within milliseconds to dangerous conditions.

Controlled Signals

• Boost pressure (MAP sensor)
• Turbo speed (if equipped)
• Wastegate/VGT duty cycle
• Fuel injection and ignition

Maps Involved

• Maximum Boost Pressure Maps
• Overboost Threshold Maps
• Response Strategy Maps
• Recovery Conditions

Logic Sequence

Boost Pressure → Compare to Maximum Allowed
         ↓
If overboost detected:
  → Open wastegate fully
  → Reduce torque request
  → Fuel cut if severe
         ↓
Monitor for recovery
         ↓
Log fault / enable limp mode if persistent

Calibration Objectives

• Protect engine from boost-related damage
• Allow brief transient overboost (controlled)
• Enable quick recovery after protection event

Calibration Strategy

• Raise overboost thresholds proportionally to boost targets
• Maintain safety margin above target boost
• Test under hot conditions where control is harder

Diagnostics

• Overboost DTCs
• Boost control deviation
• Frequent limp mode activation

Best Practices

• Overboost protection saves engines — don’t defeat it carelessly
• If overboost occurs repeatedly, fix the control system