[Alex D]

Dan from Dinan sayds he would bet it is the detonation/knocking sensors intevening. In an a related thread on bimmerforums Shiv from Vishnu says he also thinks that the knock sensoring system is pulling back timing.

Problem being that these N54 engines (same with like our Saab turbo) do not have real knock sensors, but actually measure ionization of the combustion as it occurs on firing the intake charge. How they do it nobody has ever been able to explain to me. I don't think there are any actual sensors.

I think I remember from a discussion on the Saab forum that in our Saab turbo engine the spark plug is actually the sensing unit .... somthing about the resistance of the current flowing through the plug during ignition measuring ionization and informing the computer of impeding detonation ... I think ...