Pops and Bangs (Anti-Lag)
Pops and Bangs officially called anti-lag keeps the turbocharger revving with shifting, a technique derived from racing. Nowadays with the gasoline turbo engines, it’s mainly about the pops and sometimes flames from the exhaust at throttle off!
Thus, an anti-lag system (ALS) ensures that, after the throttle is released, the turbocharger’s impeller continues to rotate and immediately returns to pressure, thus eliminating the problem of a slowly spooling turbo. This is done by injecting additional fuel after releasing the throttle and igniting it in a delayed manner creates pops and keeps the turbo’s impeller revving.
Applying the anti-lag system is done in the engine software because when the throttle is released, the software must reset the ignition about 20 to 40 degrees from BDP (top dead center) and small amount of fuel are injected.
In theory, the ALS system is nothing more than resetting the ignition at the moment the throttle is released (20 to 40 degrees after top dead center). This combined with a light amount of extra fuel provide the Pops and Bangs.