Ignition Timing | TuningBot

Key takeaways

Ignition timing sets when the spark fires relative to piston position — the petrol power-and-knock lever.
MBT is the efficiency target; knock is the ceiling that caps it.
Advance is limited by the worst conditions the engine will see, not the best.

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.

Overview

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

In Calibration Practice

Base timing maps aim near MBT where fuel allows and rely on knock control as the fence elsewhere. Log knock retard by cylinder and load: consistent retard in one zone means the base map is optimistic there; scattered single-cylinder events point at hardware. Timing added without fueling and temperature margin is horsepower borrowed at compound interest.

Why does more ignition advance not always mean more power?

Past MBT — the timing for best torque — extra advance only raises peak pressure toward knock without adding work. The gain lives between the stock map and MBT; beyond it, knock retard claws everything back.

How does knock control interact with ignition maps?

The base map sets the aggressive intent; knock control is the safety net pulling timing when detonation appears. A map that relies on constant knock retard to survive is not tuned to the fuel — it is being rescued cell by cell.

Related: these maps and strategies are the daily work of our ECU remapping service. See also ECU Map Types Glossary in the knowledge base.