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Knock sensor question

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Old 06-15-2012, 05:07 AM   #1
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Default Knock sensor question

Hi all, I'm sure this has come up a million times but I'm having problems getting a definate answer and I hope you can help.

I've built an LS3 stroker for my father's 57, it has an LS1 from a 'vette in it at the moment and I want to use the existing computer.

I've swapped the reluctor wheel and cam timing gear to LS1 spec and bought the extension harness for the loom.

Where i'm stuck is the knock sensors, the extension harness will plug into the LS3 knock sensors but I've been told that the LS3 knock sensors won't "talk" to' the LS1 computer. Is this true? I would like to keep the LS3 sensors as I already have them and the budget has been well and truly blown.

Both engines are out of the car, but I don't want to rob anything of the LS1 if I can avoid it.

Any help will be greatly appreciated.

Matt
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Old 06-15-2012, 08:16 AM   #2
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Quote:
Originally Posted by Suparoo View Post
Where i'm stuck is the knock sensors, the extension harness will plug into the LS3 knock sensors but I've been told that the LS3 knock sensors won't "talk" to' the LS1 computer. Is this true?
LS1 knock sensors are a single wire and later Gen4 are a twin wire.
Think of LS1 style as just a simple microphone collecting noise samples, whereas the Gen4 style puts a noise down one wire and collects a new noise back down the other wire. Gen4 computer then compares induced noise to returned noise and spits out the differential noise as a result.
The physics/construction of the knock sensors will suit one process but not the other.

Same solution for LS3 as LS2 below.
Click the image to open in full size.
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Old 06-15-2012, 06:08 PM   #3
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Thanks for that, but are you sure?
The extension loom I have (genuine GM) has the second wire on the sensor going to ground
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Old 06-15-2012, 10:03 PM   #4
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You probably have the wrong harness then. You must use ls1 knock sensors on your Gen4.
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Last edited by litle88; 06-16-2012 at 07:47 AM..
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Old 06-17-2012, 01:42 AM   #5
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Originally Posted by Suparoo View Post
Thanks for that, but are you sure?
The extension loom I have (genuine GM) has the second wire on the sensor going to ground
Check the GM diagram here:

http://www.hsv-gts.ls2.com/KS1.pdf
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Old 07-02-2012, 07:49 PM   #6
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Thanks all
I got the new sensors and drilled and tapped the block.
Almost ready to fire up, fingers crossed.
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Old 08-27-2012, 01:25 PM   #7
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Default additional input on knock sensor?

Looking for more information on the knock sensor. On the ls3 driver side my knock sensor fits without drill/tap with header and wiring (alternative location in green on pic above)...however on the passenger side the knock sensor fits but not with the wiring as it rests on the header. Can 1 side be in the upper location while the passenger side is on the lower location (being drilled and tapped, red location on pic above). I'm probably thinking too much about it but if its listening to "the heartbeat" does it matter the location or should it be truly "stereo" and be in the same location on both sides of the block.
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Old 08-27-2012, 08:53 PM   #8
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Should be ok, iirc that's what I had to do because I have 2" headers and I had clearance issues.
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Old 08-27-2012, 08:53 PM
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