RF Ping

[Jeff M]

The knock retard unit I use in my 650 hp Typhoon is one from a Corvette, and
is graphted into the Accel DFI that I need to make this thing run with 66
pound injectors.  I see other companies using this knock box for some of
their custom setups.

Jeff Middaugh
tystorm at email.msn.com
1993 Typhoon (yes that is dyno tested hp ;-)


> Using the knock sensor as a 'microphone', connect an
> audio spectrum analyzer. Run the motor without knock
> as a baseline, recording the output. Now induce the
> knock, and record the output. There will probably be
> several spikes due to the knock. Choose the strongest
> spike (frequency) that is distinct from the rest of
> the normal engine noise. That is the one that you want
> to keep, filtering out everything else.
>
> Don't have an audio spectrum analyzer laying around?
> There is off the shelf PC software that will use a
> sound card to perform exactly that function.
>
> Now, as for modifying the ESC to filter out everything
> else, I cannot help. You could build an external
> filter with an op-amp and some precision resistors and
> caps.
>
> If you knew what frequency the ESC was currently tuned
> for, you could:
> 1) Have an oscillator running at the old frequency
> which would be triggered by in-band signals at the new
> frequency, feeding the ESC.
> 2) Calculate the frequency difference, then inject and
> mix the IF with the knock sensor to produce in-band
> signals at the old frequency (superheterodyne anyone?)
>
> OK, OK, you get the idea, I'm laughing too hard now to
> continue ....
>
>
>
> --- Dave Zug <dzug at delanet.com> wrote:
> >
> > > since the ESC filters out everything except the
> > specific frequency of
> > > signal it wants, unless the RFI was at the knock
> > frequency, it would either
> > > do nothing, or maybe reduce sensitivity.
> >
> > and not all knock sensors are tuned for the same
> > frequency correct?
> > I get barely any knock on a boosted 5.7l with a
> > stock prom and 89
> > octane ..I'm wondering if the new alum heads require
> > a different
> > frequency detection range ?
> >
> > ~~~
> > Dave Z. www.delanet.com/~tgp
> >
>
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