Anti-lag is designed simply to spool the turbo and therefore create positive boost pressure to allow the turbo to build boost pressure at a standstill, turbo lag normally occurs when when the vehicle is initially pulling away from a standing start. Anti-lag can be integrated into the engine management, or can be fitted as a standalone unit.
Method of Anti-Lag
The basic method of operation is to artificially lower the engine rev limiter to hold the engine at a speed where the turbo can produce usable boost, by altering the ignition. Because the ignition is alternately cut or retarded, there is similar noise and misfires associated with other anti-lag systems. Systems for two-step launch are designed to be fitted in addition to the existing engine management work by interrupting the crank position sensor signal, so that the engine develops a controlled misfire at a pre-determined RPM. The basic premise of the launch control system is to build positive boost pressure from a static engine.