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From a tuning perspective why would you use knock counts rather than knock retard to tune! given what Jayme advised "knock counts only occur right when the knock happens, wheras the retard starts where the knock happans, then ramps down, so in a histogram, you get data appearign in cells that didnt actually ping"

Is this because of the time it takes from the point that the knock count occurs is then processed and a decision to apply the appropriate knock retard amount plus the decay factor or the decay factor only.

Because if it is the decay factor only then the 30 hertz knock retard is superior as it appears in the same cell and has the added advantage of showing the knock intensity in degrees and therfore a reference for moving the timing map accordingly.

If it is not the decay factor only then logging the knock counts would be superior for tuning.

I guess when we can log both knock counts and knock degrees at 30fps the answer hopefully will become clearer.

VL400 wrote:Knock counts cause knock retard. The counts is what the ECU uses to determine how badly its knocking and how much spark advance to pull. The knock filter filters the sensor to a narrow frequency range, the digital output of the filter changes state based on if knock is present. How long its present for determines how many counts you see, which is then used with the table "ESC Attack rate(Deg/mS) vs RPM". The table has values that are deg/ms of knock, the ms component is the duration of the pulsed output of the knock filter. So if the table has 4 deg/ms then 4 deg of spark advance gets pulled for 1ms of knock - which using a 65khz counter inside the ECU gives 65 knock counts per ms. More counts more spark gets pulled and conversly, less counts less gets pulled.

A detailed insite thanks.