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Old 01-17-2003, 10:23 PM   #46
Jon [in CT]
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Member#: 2992
Join Date: Nov 2000
Chapter/Region: NESIC
Location: Connecticut, USA
Vehicle:
02 WRX Sedan
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Some other observations.

It appears that the stock ECU's load reference for ignition timing is, crudely, boost.

It appears that ignition advance determination depends, ultimately, on the input from only three sensors:
Crank angle position sensor (for engine RPM)
Manifold absolute pressure (MAP) sensor
Knock sensor

It appears the ECU ignores other sensors which folks here have speculated are an influence on timing advance:
Mass air flow (MAF) sensor
Throttle postion sensor
Intake air temperature (IAT) sensor

I know, for instance, that RiftsWRX believes strongly that intake air temperature plays an important role in determining ignition timing advance, so strongly that he was able to persuade the UTEC designers to include it as a timing advance modifier in the TurboXS UTEC piggyback.

And to Shiv (who asked: "Hey, doesn't anyone want to know why this works? I don't think anyone has asked that yet... any guesses?"):

I'll bite. I'm asking: why this works?

And please don't be shy in the future about sharing other observations/tips about how the stock ECU really works, now that you can see it internals.

P.S. Shiv, if I have guessed more or less correctly, am I the lucky winner of an ECUTEK Stage 2 from Vishnu?
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