Quote:
Originally Posted by MuMan
Interesting to note there's 2 locked maps in there, Gen 2 that is, one for 14psi and one for 16psi. Used to be a company in Ca I think it was, that would unlock the maps and install a user programable chip.
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This bit of misinformation was most likely started to sell ROM tunes and is still quoted as a "fact" by MR2 "literati." There are two map set available to the ECU at all times. One is only intended for use when the ECU believes that the fuel is of sufficient octane to run the more aggressive of the two maps. The high octane map set has 2 additional load columns for higher resolution at the top end. The ROM tunes effectively lock out the low octane map which probably doesn't sound as cool as saying that they unlock the high boost map which was always available as long as you ran what Toyota considered to be sufficiently high octane to use these maps safely.
Given that the load sensor on the gen2 ECU is the AFM, there is no notion of boost acting as the y index into the maps. What is being calculated from the AFM voltage signal is what we can best call "flow." It is basically the flapper voltage divided by RPMs. Flow is proportional to boost only if you keep VE fixed. When you start messing around with exhaust systems and turbos, VE changes, so the point on the maps which the ECU uses under a particular boost changes. To further complicate matters, the AFM flapper door completely opens once 210-220rwhp is reached. Beyond this point, the ECU is always referencing the same top row of the map regardless of how much more air flows into the motor. If you adjust the ROM maps to bring fuel and timing in line at this point, you also end up adjusting fuel and timing at lower part throttle settings. ROM tunes will not be all that they can be in the MR2 world until the AFM is replaced with a device that measures flow to at least the level or power that the motor is expenced to develop with said tune.
So how did we end up discussing the gen2 ECU in a thread about the MS? I've spent months pulling apart the stock ECU code and I can tell you that it is a case study into how tight you can write EFI code. Most of the MS code I've seen is pretty slow and inefficient compared to the stock ECU code.