Knock limitation
WARNING: This page is about a different car, the 2003 Saab 9-3 and 2002 Saab 9-3. However, it is still accessible from the selected car via links, so may be relevant.
Knock control first retards the ignition timing for each cylinder. If the mean value for the ignition retardation for all the cylinder exceeds a certain value, fuel enrichment will take place.
If the mean value for ignition retardation increases further, the maximum permissible air mass/combustion will be reduced.
This reduction takes place continuously as the ignition retardation increases.
The value constitutes the maximum air mass/combustion value permitted by knock control.