What sort of signal is the knock sensor?

[Bruce Plecan]

----- Original Message -----
From: Paul Blackmore <paul_blackmore at hotmail.com>
Subject: What sort of signal is the knock sensor?

Much easier way to remember it is noise sensor.  Only after filtering is it
somewhat a knock sensor.   Exhaust rattles, fan belt, alt bearings, all of
these can mimick the sound of knock as far as the gm sensor/system goes.
  The knock between gear changes is why I beleive they came up with a burst
knock contol during rapid TPS changes (if anyone knows better feel free to
correct me).
Grumpy
The above mentioned filtering is to reduce the signal to a specific
frequency that the engineers were worring about (Maybe more than 1, I've
found two in one application).


| Hi all,
|
| I've been looking at some ALDL info of VS Holden Commodores taken while
| doing some very hard driving around Winton raceway. (Its hard to type
while
| coming out of a corner sidways)
|
| The signal is graphed and appears as a spike varying in height (well value
| actually) from 10 to 255(max).
|
| The signal rarely appears under normal driving conditions but when we were
| pushing the cars hard around the race track at WOT the spikes were coming
| high and often (four or five times while accelerating per gear change).
| The signal also usually appears (only once) when blipping the throttle for
| downchange while braking.
| It also appears (only once) when the car is stationary and the engine is
| spun up to redline with a WOT.
| It appears more so when the engine is warm and less so when the engine is
| cold.
|
| I have been told that the knock sensor would not "go off" that often.
| However, could it be that the knock sensor is probably going off more than
| we think but it is just "ignored" by the ECM if it is just a small knock
and
| that only big knocks cause the spark to be retarded?
|
| Cheers
| Paul Blackmore
|
|
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