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Old 01-23-2003, 01:40 AM   #60
Vishnu Performance
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Member#: 14494
Join Date: Jan 2002
Location: SF Bay Area, California
Vehicle:
WRX Porsche 996
blue & black

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Wow... a lot of info here. But here's what I know (or at least I think I know) from our remapping efforts :

1) There is only one ignition timing table and one knock correction table.
2) The load axis for the fuel, ignition and knock correction tables is MAF, not MAP.
3) The ignition timing map is very conservative and relies on anywhere from 0-12 degrees of additional advance which is provided by the active knock correction system.
4) The knock correction tables resembles the ignition timing table with respect to having MAF and RPM as its X and Y axis. However, in its cells is maximum knock correction authority, not absolute base timing value. At low loads (off boost), knock correction authority is 0, meaning that no additional advance is allowed to be added upon the base ignition table values. Under boost (and especially around 5000rpm, knock correction reaches its maximum authority range (or around 10-12 degrees depending on ECU type). I can only presume that the engine calibrators at FHI determined this RPM range to be particularly "trouble-prone", requiring the "go ahead" from the knock sensor to add in the full amount of timing (learning to advance timing instead of simply assuming that is okay to do so). Naturally, the underlying timing values in the ignition timing tables are unusually low at this rpm/load range.
5) Knock correction authorty range tapers off as RPM and Load goes up (above 5500rpm). I suspect this is because knock sensors tend to become inaccurate at higher engine speeds (unable to differenentiate between actual knock and normal engine noise).
6) The "vishnu reset" simply keeps in the engine operating in a rpm/load zone where base timing is very conservative and knock correction authority range is relatively large. When the engine assumes this rpm/load, the active knock correction system readily adds in maximum positive authority range due to an absense of knock and (I suspect, engine noise). I could make this special reset not work by simply advancing base timing too aggressively in his rpm/load area. This would induce knock prematurely and never all the ECU to add in the allowable knock correction. Needless to say, I keep these rpm/load zones purposely detuned to facilitate this accelerated learning technique.

Cheers,
Shiv
www.vishnutuning.com
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