Hessitation in Late Model Subarus

[Bruce Plecan]

OK, just for giggles, how do you tell a bad A/C compressor bearing that
radiates a frequency of 25 Hz,  from a knock "noise" of 25 Hz?.  (Feel, free
to change to any freg of noise)
  Repeat the above, with fan belt "noise", Alternator bearings, throw out
bearings, rocker arm noise lifter noise etc, etc..
  If you can do it, more power to you, but, I'll still stick with my
original statement.
As for miss detection, I'll rely on crank accleration rate changes thank,
you.
Bruce


> > That's not the problem as I see it.  It's seeing a knock you don't want
it
> > to see.
> > That is a problem with all these dumb acoustic sensors, only cure is
going
> > to ionization kknock detection, please refer to the archives and search
ION.

> I don't actually believe there is anything wrong with the idea of a
> acoustic knock sensor, I really believe that most of the issues are
> with crude way they are doing it (simple filter).  I believe using a
> acoustic sensor and DSP and some code using a better algorithm would
> do alot better in removing other noises.     I would also think you
> could do miss detection using this method also, ie listen for each
> cylinder igintion and count the ones you missed.     Now I just need
> to put a mic on my engine and collected and figure out how to
> process the data in such a way to get meaningful data.
> Roger