Understanding Long Term Knock Retard

[Animal451]

Did some datalogging to send out for an email CMR tune yesterday and noticed something that I'm hoping someone can explain. Before we get too far I'll just say I have an 06 Charger SRT8 with a CAI and cat-back exhaust, and a Spartan MAX cam. There is a baseline CMR tune in the PCM now also . . .

Just for the sake of getting more information I selected the PID's for the knock sensor voltage to see if I could see where the threshold is set and to get a better idea of what causes the LTKR but now I'm more confused.

Looking at the voltages there were higher voltages earlier in the session (which was over 30 minutes). Further into the logging session I was getting long LTKR and the Knock Sensor Voltages were very low. Does the PCM keep track of the voltage over time and then start adjusting the LTKR?

[Animal451]

Nobody can answer this?

I can assume from my log that knock retard is not directly related to the voltage from the knock sensor . . . Maybe I should look at the voltage range during knock retard??

[johan]

LT KR is basically a learned/predicted value where the pcm has seen enough knock at that point that it will think it will knock at that point again and pulls out timing based on that prediction, kind of sort of....

[neidan]

So it's one of the adaptive values? If so would a reset adaptives or pulling F2 put you back to square one?

[duster360]

Not sure about the fuse(i usually disconnect the battery) but resetting the Adaptives through a DRB or other scan tool works.

Flashing a new tune doesn't do anything to the Adaptive memory.

[neidan]

Not sure about the fuse(i usually disconnect the battery) but resetting the Adaptives through a DRB or other scan tool works.

Flashing a new tune doesn't do anything to the Adaptive memory.

Your correct duster, and as I understand it pulling the F2 will also clear the adaptivs. But it was implied above that long term knock values were a 'learned' value used to 'anticipate' knock points. So what I am wondering now is; if clearing the adaptives would effect the Long Term Knock values? It would seem so?

[DGatzby1]

But wait! What are we saying here? If you have a CMR tune, you should have little or no short term knock, and long term knock should be the least of your worries. That car should be performing very well...I know, I have nearly an identical unit!

Just for fun last night, I have the 93 CAI tune with 10% fuel across the board added, 93 BP Gas (had to say goodbye to E-85 for the year, damn getting too cold), nailed it at 30 mph, broke them loose, burnt rubber into second gear, plus great second gear rubber, finally bit and was off sounding great. If you can't do that with a cam and CMR tune, have them RE-DO that tune.

FYI I log the ST and LT RETARD, I don't know what you would want to do with the voltage readouts, would not make any sense to just a simple user like me. If you do a search I believe it has been discussed before.

[duster360]

Not sure about the fuse(i usually disconnect the battery) but resetting the Adaptives through a DRB or other scan tool works.

Flashing a new tune doesn't do anything to the Adaptive memory.

Your correct duster, and as I understand it pulling the F2 will also clear the adaptivs. But it was implied above that long term knock values were a 'learned' value used to 'anticipate' knock points. So what I am wondering now is; if clearing the adaptives would effect the Long Term Knock values? It would seem so?

Yes clearing the adaptives will always bring LT knock to 0 across the board, up until the PCM decides it needs to add it back in.

[gizmodo]

The knock sensor voltage does you no good, you need to look at the actual knock PIDs.

[neidan]

Not sure about the fuse(i usually disconnect the battery) but resetting the Adaptives through a DRB or other scan tool works.

Flashing a new tune doesn't do anything to the Adaptive memory.

Your correct duster, and as I understand it pulling the F2 will also clear the adaptivs. But it was implied above that long term knock values were a 'learned' value used to 'anticipate' knock points. So what I am wondering now is; if clearing the adaptives would effect the Long Term Knock values? It would seem so?

Yes clearing the adaptives will always bring LT knock to 0 across the board, up until the PCM decides it needs to add it back in.

Thanks a lot man. I was guessing that would be the case... but ya know... I was guessing! javascript:emoticon(':D')