Knock Correction vs Knock Correction Learn values?

[jamesm]

Originally Posted by steve99

I think I read somewhere that their is some sort of catalytic converter warm-up phase that results in higher idle and more fuel for a while after startup, not sure if Shiv disables this in sage 2 catless header tunes, seem to remember some talk on it ??

it targets rich for a brief moment after startup, and there are maps to adjust it. you can tell pretty easily when it's happening, it's when your idle target is like 1500 immediately after a cold start. the car is usually in port-only mode at this point too.

[mikalem]

Originally Posted by mad_sb

Couple things.
1. I believe the knock learning / IAM system is much more "sensitive" right after a reflash. I recall reading about that on romraider at some point. So, if after the first drive cycle the reading are more stable then take it easy for the first drive cycle.

2. Your motor could be more noise prone when it's cold, assuming that fits your scenario and your not letting it cool over night between your drive cycles.

I believe you are right - I remember reading about some fine adjustment table that resets on flash, so for a etune it seems to make sense the car is learning this table which may cause the IAM to move. Once that table is set down it seems the IAM is unlikely to move unless a true knock/bad gas situation is going on

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[jamesm]

Originally Posted by mikalem

I believe you are right - I remember reading about some fine adjustment table that resets on flash, so for a etune it seems to make sense the car is learning this table which may cause the IAM to move. Once that table is set down it seems the IAM is unlikely to move unless a true knock/bad gas situation is going on

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There are several conditions required to enter coarse correction, one of which is the last applied flkc value. It must be significant and negative (I think -3.1 or worse), so heightened activity around flkc will indeed cause the iam to move around more.

[mikalem]

Originally Posted by jamesm

There are several conditions required to enter coarse correction, one of which is the last applied flkc value. It must be significant and negative (I think -3.1 or worse), so heightened activity around flkc will indeed cause the iam to move around more.

Wondering if on a reset/flash the car starts in coarse correction mode? Perhaps that would explain what I see.... I have to read more to understand for sure.

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[jamesm]

Originally Posted by mikalem

Wondering if on a reset/flash the car starts in coarse correction mode? Perhaps that would explain what I see.... I have to read more to understand for sure.

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the modes of knock control switch so fast as to seem that they're all active at once, when in reality only one ever is. fbkc is the standard operating mode. once you see knock multiple times in the same flkc cell, negative values are written into flkc. if the value is negative enough, it enters coarse correction and drops the iam. once this has happened, it's possible for flkc to go positive, which can bring the iam back up. all the while, it's spending the majority of it's time in plain old fbkc mode, just reacting instantaneously to knock events.

so, moral of the story is that it doesn't stay in one mode for long (meaning milliseconds at a time), except fbkc where there is no knock present. it is possible that the threshold to enter flkc (the first step to coarse correction) is lower during warmup phase or immediately after a flash, but i've never recorded any data that could confirm that (of course i've never tried, either).

[thambu19]

Some OEM codes have a background knock learning strategy. What this means is that the ECU will try to learn in the background noise created by all moving parts. How this helps is once this background noise is learnt it will allow ECU and knock sensor to pick up knock more accurately. Too low a background learn will make knock sensor more sensitive to knock and too high a noise learn will let low intensity knock pass through. When we relash ECU this learn is lost and most companies resort to a safe background noise calibration. This makes the sensor pick up knock that would otherwise be ignored and perhaps is why the more stronger spark pull out initially. Background learns are completed at low load from mid to high engine speeds so almost like coast down in gear sort of or 1st gear and slow engine speed increase at low load.