Originally Posted by
engineermike
Good questions.
There are a few ways to deal with flex borderline timing. One would be to leave the table all 0s and let the knock advance find the new, higher limit. This is the ultra safe way. Another way is to just populate the table with something in the 4-8 range. This is the least safe, but will work fine if you follow fords instructions for flex fueling. Then theres the in between way that the f-150 does it. They only add borderline at low speeds and loads and phase it out up top. My theory is it basically gets you the timing sooner at low rpm which allows knock advance to bring in the timing up top.
On mbt, it actually reduces timing on e85. This is probably technically accurate but most seem to agree that fords mbt is too low to begin with. For sure, if you leave it alone you wont be seeing those 30-32 deg numbers you hear about. However, you do at least need to copy the low load/speed numbers over because it affects anything requiring torque control, like idle, shift torque modulation, etc. what you could do is copy the f150 values at .8 and below load, and add a couple degrees above that. That said, make sure youve adjusted the cylinder pressure limit table or youll hit that before you ever reach mbt.