What it's for
Launch control works from a standstill. Roll racing starts at speed, and a turbo engine cruising along at part throttle has no boost. Rolling anti-lag fixes that. While the driver holds the rolling anti-lag button, the ECU caps either engine rpm or vehicle speed. The driver can go to full throttle, loading the engine and building boost, while the car holds its pace. When the button is released, the cap goes away and the car launches with boost already made.
Choosing a control type
| Control Type | What it holds | Good for |
|---|---|---|
| RPM when activated | Whatever rpm the engine was at when the button was pressed | Flexible setups where the start speed varies |
| Fixed RPM | The rpm entered in Fixed Limit | A repeatable rpm every time, in a known gear |
| Speed when activated | Whatever road speed the car was doing when the button was pressed | Events where you roll in at a pace car's speed |
| Fixed Speed | The speed entered in Fixed Limit | Events with a set rolling start speed |
Both speed-based options need a working vehicle speed input. Check it reads correctly before an event.
The other settings
- Cut Method: how the ECU enforces the rpm or speed cap. If you have a choice between fuel and spark cut, ignition cut tends to hold a limit more tightly, but it's harder on the exhaust and turbo.
- Ignition override enable: adds a rolling anti-lag ignition override table in NSP. Retarding timing here lets the engine take more throttle without gaining speed, and puts more heat into the turbine.
- Fuel correction enable: adds a rolling anti-lag fuel correction table, so you can adjust mixture while the function is holding.
Both tables can be mapped in two dimensions, so you can shape the correction against rpm, speed or whatever axis suits your setup.
Start with mild timing retard and a short hold, then add more as you confirm exhaust temperatures and boost in the logs. Holding anti-lag for a long time puts a lot of heat into the turbo and exhaust.
The button wiring is covered in rolling anti-lag wiring. For the standing-start version, see launch control, and for anti-lag between gears, see anti-lag.
