ECU tuning JDM vs USDM

[b3lha]

As this thread has bubbled to the surface again, let me give an update on my current understand of these maps.

The fuel map shows a target air:fuel ratio based on rpm and load. The value 128 means stoichiometric 14.7:1. Higher numbers mean more fuel (lower AFR), lower numbers mean less fuel (higher AFR). The formula is something like 14.7/(z/128).

The timing map shows base timing. That is the fully retarded timing based on the lowest octane fuel.

The map which I have labelled "Knock Correction" should really be labelled "Ignition Advance". This is the maximum amount of advance that the ECU is allowed to add on top of the base timing. It would be easier to visualise if I had printed the maps in the same orientation.

There is a variable that determines what proportion of the advance gets added to the base timing. I assume that the ECU increases the value of the variable until knock is detected and then backs it off a bit. But I don't know for sure yet. I am still figuring out exactly how this works.

Looking back at the graphs, you can see that while the base timing is not very different, the JDM ECU is allowed much more advance, presumably because of the higher octane fuel.

The (previously) unknown map at 8F50 calculates the duty cycle for the purge control solenoid. Since the previous posting I have found lots of other unknown maps, mostly 2 dimensional ones.