Originally Posted by Sal@Evolve
Ignition advance is massively affected by octane. We have datalogged this many times.
With high octane fuel the ECU will very much hit it's ignition targets (Stock) and make best power.
The Dinan car is quite clearly hitting it's ignition targets.
The car we tuned is on 91 and will not hit ignition targets as you can clearly see and nor are we forcing ignition.
The sudden drop and rising of the ignition is quite normal at high rpm's. Will vary from run to run.
Sal - Not trying to get you to give up the farm but what does the stock spark advance plot look like? Is it more like the Dinan car in this comparison (in terms of magnitude and shape) or more like the Evolve tuned car? Just trying to understand what the ECU is up to when it's compensating for reduced octane. Is it simply going to retard timing by several degrees across the board (what I would expect from experience with less sophisticated knock control systems) or does it also change the shape of the curve/map (what we see in the two different plots above)?
It's threads like this that make hanging around these forums worth it, awesome stuff.