When you lift off the throttle, whether at idle or coasting down a hill, the engine behaves very differently from when you're driving it. The Zero Demand table lets you fuel those closed-throttle moments separately from your main fuel map, so you can tune them without disturbing the rest of the map.
When it's active
The table only takes over when driver demand is below the User Demand Minimum set in Throttle Limits. On a cable throttle, that's judged from throttle position; on drive-by-wire, it's accelerator pedal position. Above that threshold, your normal fuel table is back in charge. It's disabled by default, so nothing changes until you switch it on.
What the numbers mean
| Tuning method | Zero Demand values are |
|---|---|
| VE | VE-style values |
| Mass Air Flow | VE-style values |
| Injection Time | Raw injection times |
You can map it in up to 2D. With VE or Mass Air Flow, enabling the table also brings in the MAP Reference At Zero Demand setting.
How we use it
We turn it on when idle and overrun fueling are fighting with the main map, for example on big-cam engines where MAP at idle is noisy and overlaps with light cruise. Start by copying values that match what your main table was giving at idle, confirm the car behaves the same, then refine from logs of lambda at idle and on decel. Make sure throttle or pedal calibration is spot on first, because the switch-over depends on it.
See also base fuel tuning, fuel tuning, ignition zero demand and throttle position.
