Timing Corrections

I am currently tuning an ECU where when operating in the transition zone (between cruise and boost) I have been seeing some timing corrections whilst using 95 RON fuel. If I switch to 99 RON fuel then the timing corrections go away. However, I have tried retarding the cells in the partial load base timing table but the timing corrections don't seem to be reducing or going away when using 95 RON. In some areas I have removed as much as 7 degrees of timing (but timing corrections were around -3 degrees before I made any changes).

Could pre-ignition be the cause here?

Shaun,

If it goes away with better fuel, generally it's real. If retarding timing isn't working, have you tried richening the mix a little in that area?

It certainly could be pre-ignition (AKA dieseling or compression ignition) igniting the fuel, or just raising the combustion temperatures around that point may be increasing the change of detonation from hot spots.

I'd suggest doing as Mike said, to see if that helps.