Engine knock control is a core safety and performance strategy in modern gasoline ECUs (MED17, MG1). The ECU must detect abnormal combustion, classify its severity, and adjust ignition timing accordingly to protect the engine while maintaining efficiency.

Panoramica

Knock occurs when end-gas in the combustion chamber auto-ignites under pressure. The ECU continuously monitors knocking using block or individual-cylinder knock sensors, comparing measured vibration patterns against calibrated noise models.

Controlled Signals & Sensors

• Knock sensor voltage / filtered knock intensity
• Crankshaft position (for windowing)
• Engine load, pressure ratio, temperature
• Ignition timing advance
• Noise model reference curves

Maps Involved

• Knock Threshold Maps: vibration limit per RPM/load
• Noise Model Maps: baseline engine noise
• Ignition Base Maps: main timing source
• Ignition Correction Maps: per-cylinder or global
• Knock Recovery Maps: speed of timing re-advance

ECU Logic Sequence

Knock Sensor → Filtering → Windowing (per cycle)
        ↓
Compare to Noise Model
        ↓
Is knock > threshold?
        ↓ YES
Reduce ignition timing
        ↓
Store knock intensity for learning/recovery

Calibration Objectives

• Ensure safe operation under all fuel qualities
• Maximize performance without inducing persistent knock
• Maintain consistent cylinder-to-cylinder behavior

Calibration Strategy

• Do not over-advance base ignition maps when torque targets increase
• Raise knock thresholds conservatively if needed
• Allow recovery only when sustained knock-free cycles are detected
• For turbo engines, coordinate with boost control and lambda targets

Diagnostica

• Knock sensor DTCs (range/performance)
• Cylinder-specific timing corrections >3–5° indicate issues
• Abnormal noise model adaptation

Common Mistakes

• Excessive ignition advance after turbo upgrade
• Raising knock thresholds instead of correcting timing
• Ignoring fuel quality variation

Best Practices Summary

• Safe advance first, power second
• Monitor cylinder imbalance
• Use EGT and lambda to support knock strategy