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Originally Posted by FastOldGuy
Hmmm I assuming the AEM is reading the OEM knock sensor, correct? I guess I want to know how I decide when the knocks seen by AEM are important or not.
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Yes.
You decide what the knock threshold is by running the car at lower boost through the rev range when you know the car isn't knocking (ie: provide plenty of fuel and use a conservative timing advance range), then review your log of raw knock sensor voltage, and then plot out a knock sensor threshold calibration that's a little higher than what you logged for raw voltage. After that, when knock raw voltage exceeds your threshold, the knock control routines will apply whatever timing and fuelling changes you set up whenever the "Knock Control" checkbox is checked.
Generally, anything over about 1.5V is almost guaranteed to be "real" knock. True knock will have spikes much taller than the surrounding samples.
One thing to be careful of is that the logger via the serial cable (realtime logging) is not fast enough to catch all the knock spikes, so you are only seeing some events and not all of them. To get higher resolution you can use the AEM's internal logger set on the fastest speed and then download the log to your laptop afterwards for review.
I generally watch my knock retard and knock fuel parameters to determine if I am getting knock beyond my threshold I set. Those decay slower, so you'll be able to easily spot them in logs and know that excessive knock occured right before the fuel/timing adjustment gets kicked in.