Re: Desensitizing GM knock sensors

[Roger Heflin <rah@horizon.hit.net>]

On Thu, 17 Feb 2000, Jim Wilson wrote:

>   Hi Guys,
> 
>   On my 92 LT1 383 Vette I have a CR of 9.4:1 and a Vortec Supercharger (10#
> boost). I have tried 101 76 Race gas, have changed the spark map over 4000 @
> 100KPA to as low as 20 degrees Adv. and still show a 7 degree knock retard
> spike anytime in boost (over 100KPA). What do you think about trying to
> densitize the Knock Sensors. If so what is the best way, teflon tape?
>                                  Thanks, Jim
> 

THe easiest way to detune is the to put a resistor in circuit with the
knock sensor to change the magnitude of the signal.    My knock sensor
went out (open circuit) and is disabled right now, though I am NA with
a big cam (on a 93 f-body) so I am less worried about real knock
happening.  I have tried to replace the sensor, and it won't come out
of the block, ie it is sheet metal with 120k on the car and has never
been removed, I don't think it is getting replaced until I pull the
engine.

And something to note, If you really get knock with a blower, the
LT1's computers usually don't pull spark fast enough to save the
pistons, of course that may not be true with aftermarket piston like
you proably have.

You can also adjust things in the computer to control how fast and how
much knock retard it will do.

Watching the knock counts does it spike all of the time, or just when
the TCC locks or when gears shift?  Check to see exactly when things
happen, mine was registering knock during TCC lockup and during
shifts, both things that physically rattle things around.  The is what
most false knock is, something moving around the engine that makes
noise, I have heard that timing gear sets will make the car computer
think it alwasy has knock.

			Roger
			http://www.hit.net/~rah


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