LS3 swap knock sensor functionality

A friend of mine swapped a forged LS3 with ported heads and a G6X3 (car SCREAMS now...very very nice combo) into his 2000 Trans Am. He's got the knock sensors plugged in with a conversion harness, and they appear to be talking, but I never see ANY knock retard at all...I don't think it's possible since I'm still just beginning to dial his cars tune in.

I searched and found a few posts saying to make them more sensitive (lower the values in the Knock Sensor Level tables I think)...but should I do anything with the Global Gain table?

I lowered the values in the 2 level tables to ~80% of what they used to be, but still nothing.

Have any of you guys gone through this...have any advice for me?

I have read that the ls3 sensors are not compatible with ls1 pcm. I was not able to make them work. If you figure it out please post it up.

I used my ls1 knock sensors with my ls3. Tapped out the knock sensor holes in the side of the block and screwed the ls1 knock sensors in there. Seems to work ok, I have seen a degree or two of KR when the engine had its first tune loaded in etc.

Cheers
Benno

I've seen many of them rattle like marbles in a can and not have any knock retard. They def need to be made more sensitive. I use 'knock sensor level/vs rpm vs cyl'. Seems to do the trick.

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Originally Posted by edcmat-l1

I've seen many of them rattle like marbles in a can and not have any knock retard. They def need to be made more sensitive. I use 'knock sensor level/vs rpm vs cyl'. Seems to do the trick.

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How much did you increase the sensitivity?

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Originally Posted by edcmat-l1

I've seen many of them rattle like marbles in a can and not have any knock retard. They def need to be made more sensitive. I use 'knock sensor level/vs rpm vs cyl'. Seems to do the trick.

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If I understand that table correctly, lowering the values should make it more sensitive...I guess I will try to scale it further. The engine SOUNDS fine, and it makes very very clean pulls...but I'm still nervous about the "what if's"...like...what if he puts 87 octane in by accident??? Or what if his fuel filter gets a little crappy and he goes a little lean???...What if he gets crappy gas from the 93 pump???

I'll keep playing with it, unfortunately we live a half hour apart, and work different schedules, so I can't play with it every day. If I come up with something that works I'll post up the tables...or at least my methodology, since I guess you'd probably want to tune it around the normal noise of the engine/drivetrain which will be different on non-stock engines.

Thanks for the help guys.

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Originally Posted by mecanicman

How much did you increase the sensitivity?

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I usually just mulitply 3K and up by .7. Depending on the application, I'm looking for the computer to pull some knock retard at a specific timing level, without actually hearing the knock. If you can get it to pull some timing, then you can either modify the knock sensitivity, or modify the HO spark table.

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Originally Posted by edcmat-l1

I usually just mulitply 3K and up by .7. Depending on the application, I'm looking for the computer to pull some knock retard at a specific timing level, without actually hearing the knock. If you can get it to pull some timing, then you can either modify the knock sensitivity, or modify the HO spark table.

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My thought was to modify it until I see some...then if removing spark from the high octane table didn't change what the sensors heard...I'd know I'd gone too far and back off towards where it was just a little...and if the modification to the high octane table caused the KR to go away...then I'm right in the ball park for where the knock sensors need to be...if that makes sense?

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Originally Posted by MikeOD

My thought was to modify it until I see some...then if removing spark from the high octane table didn't change what the sensors heard...I'd know I'd gone too far and back off towards where it was just a little...and if the modification to the high octane table caused the KR to go away...then I'm right in the ball park for where the knock sensors need to be...if that makes sense?

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That's it. But you'll need to start with what would be a "sane" amount of timing for the combo. Too low or too high and it'll screw up dialing in the knock sensor sensitivity.

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Originally Posted by edcmat-l1

That's it. But you'll need to start with what would be a "sane" amount of timing for the combo. Too low or too high and it'll screw up dialing in the knock sensor sensitivity.

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Yeah...I've been very careful with his spark tables...they seem "sane" to me, not too agressive, not too conservative. They seem to produce great throttle response, his mileage is alright, and the full throttle power is fantastic. I'll play a little more with that when I have it in a controlled setting (dyno dynamics dyno) a week from tomorrow though.