Acoustic Knock - finale?

[Bob McElroy]

Perhaps we are all being a little too sensitive about our egos.  I re-read
my post, and didn't think it was that terribly offensive, but obviously I
did offend some persons, and for that I apologize, that was not my
intention.

Now, I did not say that acoustic knock detection does not work, and yes, my
books did reference the GM acoustic knock detection units (and yes, I am
also aware that manufacturers other than GM are also very successfully using
acoustic knock detection methods.)

No where in my reply do I make the assertion that acoustic knock detection
is not a viable means of knock detection.  All I said was that any knock
detection method needs control and interface hardware and software.  I
re-read the TI application note, and found no reference that the DSP IC
manufactured by TI is sold by TI as a simple "plug-and-play" type solution.
It is up to the person who wants to use the DSP to also make sure that there
is appropriate hardware & software for the DSP.

Quoting from the TI application note: "Knock detection strategies use the
output of a signal conditioning stage to compare with a reference to
determine the presence or absence of knock.  Most systems today use
windowing to isolate periods during the cylinder's firing cycle for analysis
when knock is possible.  ...  By eliminating possible false trigger sources,
... the detection algorithm is more robust.  The time this window is active
varies with engine speed ...  Tracking changing engine speed to calculate
this time variation requires hardware or software ... for implementation."
>From this quote, it seems to me that TI is stating that you need to provide
your own software and/or hardware to interface and control the DSP.  (Did I
miss something somewhere else?  No sarcasm intended, I'm just trying to
understand because I know that I don't know everything, and it is very
possible that I missed something important.)  The TI application note does
give some source code, but I would expect that the software would still need
to be tweaked to work with your specific combination of engine and knock
sensor.

If I am mistaken, and there is a "black box" solution that you can simply
hook up a few wires and it works, please let me know, and I will eat plenty
of crow, and will also secure my CSH with JB Weld.

Finally, as I recall, the initial posting was a simple request for someone
to point you towards some information regarding the TI chip.  Further, I
seem to recall that you implied this could be easily adapted to your engine.
I don't think it would be an easy adaptation, under any combinations of
engines and factory knock sensors.  I yield to your superior knowledge, and
I will now be forever silent on this topic.

Bob M.

PS - My apologies for posting this to the list, and I DO NOT WANT TO START
YET ANOTHER FLAME WAR on this mailing list, but I felt I needed to try to
clear up any misconceptions regarding my posting.  If anyone feels compelled
to flame me, please do so privately to my home email address of
rmcelroy at cfu-cybernet.net and don't worry about clogging my connection, my
4Mbps cable modem should be able to handle just about anything anyone can
throw at me.  Thank you.


-----Original Message-----
Thanks, but someone civil sent me the information privately.

Did you ever read in your book learning, that the GM acoustic sensor
actually WORKS and that perhaps the engine I am adapting it to might be
close enough so that all I might want to do is see if there is a way to
improve the performance and maybe push the envelope a little?