Why anti-lag needs bypass air
Anti-lag keeps a turbo spinning off throttle by retarding timing heavily and adding fuel, so combustion carries on into the exhaust and keeps driving the turbine. That only works if the engine is still breathing. With the throttle closed, there isn't enough air getting in, so anti-lag systems need a way to let extra air bypass the throttle plate. Using the idle air valve for this is one of the simplest options, since it's already plumbed around the throttle.
Haltech hasn't yet published detailed help text for this setting. If you're setting it up, work through the main Anti-Lag page first, along with Anti-Lag Enrichment, Ignition Advance/Retard and Anti-Lag Wiring.
What to check
- The idle valve can flow enough air for the effect you want.
- Idle control behaves normally again once anti-lag switches off.
- EGTs and turbo condition; anti-lag is hard on both.
Want a hand configuring it? Ask us.
