Ignition timing controls when the spark plug fires relative to piston position in the compression stroke. Optimal timing produces maximum brake torque (MBT) while avoiding engine knock and excessive exhaust temperatures.

Vue d'ensemble

The ECU calculates ignition advance from base maps, then applies corrections for temperature, knock, lambda, and transient conditions. Modern engines may have cylinder-individual timing control.

Controlled Signals

• Ignition coil dwell and fire commands
• Crankshaft position
• Camshaft position
• Engine load (MAP/MAF)
• Coolant and intake temperatures

Maps Involved

• Base Ignition Maps vs RPM/load
• Cold Temperature Correction Maps
• Lambda Correction Maps
• Knock Retard Maps
• Transient Advance/Retard Maps

Logic Sequence

RPM & Load → Base Timing Lookup
         ↓
Temperature Corrections
         ↓
Lambda Corrections
         ↓
Knock Corrections (subtract)
         ↓
Final Ignition Advance → Coil Driver

Calibration Objectives

• Achieve maximum brake torque (MBT)
• Avoid knock under all conditions
• Control exhaust temperature

Calibration Strategy

• Advance timing in 1° increments, monitoring for knock
• Higher octane fuel allows more advance
• Coordinate with boost and fueling changes
• Verify catalyst inlet temperature remains safe

Diagnostics

• Misfire DTCs
• Knock sensor faults
• Rough idle or hesitation

Best Practices

• Never advance timing beyond knock threshold
• Use data logging to verify timing under load
• Test with intended fuel grade