Swirl flaps (intake manifold flaps) create controlled turbulence in the intake air to improve air-fuel mixing, particularly at low RPM and light load. The ECU adjusts their position based on engine operating conditions.

Overview

At low RPM, swirl flaps close partially to accelerate intake air through a smaller opening, creating a swirling motion in the cylinder. At high RPM, they open fully to maximize airflow.

Controlled Signals

• Swirl flap actuator position
• Engine speed
• Engine load
• Intake air temperature

Maps Involved

• Swirl Flap Position Maps vs RPM/load
• Temperature Correction Maps
• Fault Fallback Position

Logic Sequence

RPM & Load → Swirl Position Lookup
         ↓
Temperature Correction
         ↓
Actuator Command
         ↓
Position Feedback Verification

Calibration Objectives

• Optimize low-RPM combustion efficiency
• Reduce emissions during warm-up
• Minimize flow restriction at high RPM

Calibration Strategy

• If swirl flaps are deleted, deactivate in ECU to prevent faults
• Opening flaps earlier can improve high-RPM airflow slightly
• Verify idle quality after any changes

Diagnostics

• Swirl flap actuator faults
• Position sensor deviation
• Rough idle after mechanical failure

Best Practices

• Swirl flap delete requires ECU adaptation to avoid limp mode
• Inspect flaps for carbon buildup periodically