Knock sensor specs

[Bruce Plecan]

-----Original Message-----
From: Clarence Wood <clarencewood at centuryinter.net>
To: diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu>
Date: Friday, January 29, 1999 12:00 PM
Subject: Re: Knock sensor specs

The circuit involved here is for monitoring the ESC Modules input to the
ecm,
it's at the Turbo Buick GN-Ttype site in the Tech area.
Bruce


> I missed some of this thread....where can I find the schematic for the
knock sensor detector??
>Clarence
>>I built the knock sense detector-  it works fine-  just hook it to the
wire
>>going into the ECM though...  this is a full (rail-rail) logic signal.
>>Hooking it to the output of the knock sensor will not work.  When you look
>>at the ECM wire you should see a negative pulse when you rap the block.
>>All the 555 does is stretch it out so it is long enough that you can see
it
>>on an LED or a beeper.
>>If you are still having probs...  let me know.
 Kevin Vannorsdel     IBM Arm Electronics Development
 kv at us.ibm.com
>>>Since the KS thread began, been thinking how important it is.  Did some
>>poking around, after putting together the 555/LED monitor (which didn't
>>work).
>>The one off the GN has worked for others,,,,,,  What did you use for
>>trigger?.
>>>DC on the KS is 2.36v; solid rapping on the block near the sensor puts an
>>AC voltage of maybe 0.015v tops on the sensor line.  Scan tool reads
>>knocks,
>>but the value presented can be anything from 1 to 255; when it hears a
>>knock, new (seemingly random) value is set & held till the next 'knock'
>>comes along.  Knock retard degrees always reads zero.
>>There are degrees of knock retard, and knock counts (0-255) the
>>knock counts are the number of counts heard in 1/8 of a second.
>>Some calibrations for some reason just run 0-255 knock counts, and
>>repeat that continually.
>>Bruce
>>>Don't think 0.01VAC is enough fluctuation to trigger the 555 reliably;
>>even
>>using a comparitor, that's barely enough signal to pick out of the
>>background noise - lots of ignition wires nearby.
>>>Are these readings within normal limits??  Helm manual just says "an AC
>>voltage should be present" (when rapping) - no value given, but 0.01v
seems
>>real low.
>>>Thanks for any feedback - Barry