Question about Knock Detection

[dc_justin]

I was flipping through the Knock-Software section a few days ago and got to thinking about the modes of Knock Detection. I noticed that the engine PCM has the ability to detect knock at the cylinder level. It would stand to reason that there would also be the ability to detect knock at the cylinder level. Is there possibly a set of PIDs that haven't been discovered yet that would show knock detection per cylinder?

:nixweiss:

[emarkay]

Nope. There are only 2 KS's in the LS1 series engines and 8 cylinders - and the "microphones" (a good analogy) are non-directional - there is no way to localize the event's direction.
Now, some post processing on the outputs with a seperate analyzer may be able to interpolate a geneeral location based on delay and phasing, but even that would not be accurate enough for per-cylinder knock detection.

As for a PID - there ain't no way it could be.

[dc_justin]

My ponderance on the possibility is more along the lines of the timing of the knock occurence than triangulating a source.If there was not some sort of timing possible, then the knock sensor multiplier tables wouldn't seem to make any sense... Just a thought.

[joecar]

Or... the PCM knows when each cylinder is going to fire and compares the timing of each knock event to the cylinder firing sequence.

$0.01

[Blacky]

The cylinder mode knock detection just uses one or the other knock sensor for each particular cylinder.

During calibration, each cylinder has knock induced in it and the knock sensor that picks it up the best is allocated to that cylinder. There is a table in the PCM that calibrates the mapping between knock sensor and cylinder number. That table is not shown in EFILive - since there is no accurate way (outside of GM's engine labs) to calibrate that table.

So in cylinder mode, at each firing event, the knock routines are only listening to one of the two sensors.

Regards
Paul

[dc_justin]

The cylinder mode knock detection just uses one or the other knock sensor for each particular cylinder.

During calibration, each cylinder has knock induced in it and the knock sensor that picks it up the best is allocated to that cylinder. There is a table in the PCM that calibrates the mapping between knock sensor and cylinder number. That table is not shown in EFILive - since there is no accurate way (outside of GM's engine labs) to calibrate that table.

So in cylinder mode, at each firing event, the knock routines are only listening to one of the two sensors.

Regards
Paul

:master: