Originally Posted by
murfie
Running E85 you have much more octane. Octane is the determining factor of where the MBT and borderline should cross. The fact you are getting knock while using e85 and still NA, its most likely false.
The knock logic usually enables around .35 load. As that's usually when there's enough air in the cylinder, that the energy produced from the knock can cause damage. Having borderline drop below MBT here is usually being overly cautious, or you are planning on running 87 octane. Setting up like that the knock advance would start to advance right away and you probably wouldn't leave the MBT value until a higher load, or if the advanced was limited too much to maintain MBT.
The other factor is just the general design of the combustion chamber.
Borderlines going to be a very dynamic thing, not dependant flat on load or rpm. That's why you want your knock sensors to figure it out for you. Detonation is the dynamic phenomenon, MBT only changes slightly when you are using different fuels and targeting different lambdas.
You don't want to go too aggressive with the borderline tables, but you don't want to be too soft either other wise the knock sensors have too much work to make up. All the correction tables for borderline are to help spark be closer to where the knock sensors may see detonation.
If you are at MBT, that's the best you are going to get, going more or less is just going to get less torque.
So apply white5.0s logic of timing descends as load increases to the MBT tables, with a slight increase as RPM climbs and put the borderline tables just slightly less than where you are picking up knock with your knock sensors, after verifying you are not getting false knock. Detonation at less than MBT is what you are looking for. If you are at MBT, the knock sensors well still reduce timing if they sense knock, putting you into "borderline."