When the table is active
The Zero Demand Ignition Angle table only applies at closed throttle. On a cable throttle, the ECU checks Throttle Position. On a drive by wire setup it checks Accelerator Pedal Position. When that reading is below the User Demand Minimum set in the Throttle Limits, the engine is treated as having zero demand, and this table supplies the timing instead of the base ignition angle table.
It can be mapped in up to 2D, so you can vary closed throttle timing against a channel of your choice.
What we use it for
Closed throttle covers idle, coasting down a hill and lifting off between shifts. Having separate timing there is useful because:
- Idle stability: you can set a steady timing value near idle without compromising the part-throttle cells of the main map. See tuning for idle ignition.
- Smoother overrun: timing on decel can be shaped to reduce popping or surging as the engine slows.
- Clean transitions: keep the zero demand values reasonably close to the base table near idle rpm, so touching the pedal doesn't cause a sudden jump in timing.
If the table never seems to take effect, check the closed throttle reading against the User Demand Minimum. A throttle that rests slightly above that value will never count as zero demand.
