Anti-lag

Anti-lag (ALS) keeps exhaust energy in the turbine when the throttle is shut so the next time you open it the turbo is already spinning. Race Core does this with extra fuel, retarded spark (often into the exhaust), and a path for air — a cracked ETB, a bypass valve, or an idle valve held open. It is a race function. It is also how you glaze a turbine, colour a manifold, and light a dump pipe on fire if you leave it armed in the paddock.

What the ECU is actually doing

• Throttle closed, RPM above an arming threshold, clutch in or a dedicated ALS switch — the strategy arms.
• Spark is retarded, often past TDC, so combustion finishes in the manifold and the turbine. Fuel is added so that mixture still burns.
• Air has to get in. A cable throttle at idle stop is not enough air for serious ALS — use ETB angle, a solenoid bypass, or a lock-open idle valve.
• A rev limiter (spark or fuel cut) holds RPM while the clutch is in so the engine does not run away against a closed throttle.

Arming

Give ALS a switch. A digital input, latched, in reach of the driver. Do not leave it on with ignition. A typical map: switch on + clutch in + TPS below a few percent + RPM above ~2 000. Switch off, or clutch out and TPS rising, and ALS must drop immediately — you want the spark table back, not 20° ATDC in the next gear.

A working starting point

1. 01Base map first

   Idle, cruise and a clean boost pull without ALS. If VE is a guess, ALS will just add a richer guess on top.

2. 02Air path

   Confirm the bypass or ETB actually opens on the bench. Log ETB angle or the bypass output. No air = no ALS, just a rich misfire.

3. 03Retard and fuel

   Start mild: 10–20° retard from the normal table and a modest fuel adder. Look at EGTs and the colour of the dump. Add retard until the turbo stays alive, not until it pops the loudest.

4. 04Limiter

   Set the ALS RPM cap below the hard rev limiter. Spark-cut ALS is harsher on the turbine; a mix of retard + a little cut is the usual race compromise.

5. 05Timers

   A max-on timer (a few seconds) and a cooldown save manifolds. Rally stage ALS is not the same as leaving it on down the return road.