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whats the correct way to desensitize knock sensors and still be functional?

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Old 08-02-2005, 11:50 AM   #1
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Default whats the correct way to desensitize knock sensors and still be functional?

I have a ton of KR on my 98, i've done everything i can think of over the years to kill it, and never found the culprit (have new knock sensors, checked alot of other stuff).

anywyas, i need to kill the false knock but would like to still have the knock sensors as functional as possible incase of bad gas etc... I'm currently running in SD mode, which doesnt allow the computer to revert to the preset low octane table (since i'm using a modified low octane table - but you guys know this stuff..). so what is the most correct way to kill the KR but keep it working for detonation purposes (I still havent tuned spark advance yet, so this is important).

I think the only things i've changed were Knock sensor Global Gain vs MAP vs Cyl, Knock Fast Recovery Rate vs RPM, Maximum Knock Retard vs RPM in PE, Knock Fast Attack Gain vs. Baro, and maybe something else, i need to go back and compare what i really changed. but here are some screenshots of it. yaeh, i know they are huge screenshots, i have a dual monitor setup, so what I probably should have done is make it really tall so its scrollable now that i think of it, if anyone requests it, i can do that.

Click the image to open in full size.
Click the image to open in full size.
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Old 08-02-2005, 12:52 PM   #2
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Ouch that's ugly.

A foundational question here...Do you have any oil consumption at all?

I ask because there's one way that your knock could be real and not false...and that's if you are sucking in oil.
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Old 08-02-2005, 10:32 PM   #3
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interesting, I didnt think of that, and i dont remember reading about it in my searches, so the oil may be getting into the cylinders and causing hotspots, or baking to the pistons and causing hotspots or turbulent air - is that the right thinking?

and yes, i've always had some oil consumption, havent really monitored it since i put the cam/intake/ls6 pcv conversion on, i'll try topping it off tomarrow and metering my oil consumption. btw, my KR is either around 1600rpm under about 30% throttle, or at WOT, so if my KR was caused by oil in the combustion chamber, wouldnt it be all over the place?
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Old 08-02-2005, 10:38 PM   #4
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Could be getting KR only when you suck in oil vapors. oil has much different burn properties than gas
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Old 08-03-2005, 06:37 AM   #5
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Quote:
Originally Posted by bigshoe
btw, my KR is either around 1600rpm under about 30% throttle, or at WOT, so if my KR was caused by oil in the combustion chamber, wouldnt it be all over the place?
I can't say. It depends on too many variables....But yes you were right about how oil contamination results in knock.

Based on what you just said, even if the oil consumption is gone now (perhaps since your PCV upgrades) you still can't count out that there is carbon buildup in the cylinders causing it.
At this point you not only need to ensure that fresh oil isn't being consumed, but do a top engine cleaning to get rid of the carbon.
Someone mentioned seafoam. GM has a top-engine cleaner you can purchase at dealerships for somewhere around $30 a can. Either way, just follow the instructions.
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Old 08-03-2005, 09:06 AM   #6
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Not knocking GM, but IIRC, my can of seafoam was ~$5 at autozone
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Old 08-03-2005, 09:11 AM   #7
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It doesn't sound like the problem to me, but if you're going to try the top engine cleaning TAQuickness is right... Seafoam works great and is cheap.
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Old 08-03-2005, 10:01 AM   #8
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Quote:
Originally Posted by Wet 1
It doesn't sound like the problem to me, but if you're going to try the top engine cleaning TAQuickness is right... Seafoam works great and is cheap.

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Old 08-03-2005, 11:03 AM   #9
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have you checked the valve train to make sure it is all still in tact? there are way too many variables here that could cause real or false knock. i would want to fix it instead of override it, it may cause you problems with real knock...
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Old 08-03-2005, 11:20 AM   #10
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thanks guys, i'm buying seafoam today, planned on doing it today, but slept in, and now i have to go to work.

about the valve train, I had KR before and after my cam install, when i changed the cam, i changed to 918 springs and Ti retainers. now, when my old cam came out, i found this:
Click the image to open in full size.
and to be honest, i didnt notice it till the car was put back together with the new cam, it was after that, that i looked at the old cam and noticed this blemish. I made a post about it and we determined that it was a bad casting, and it lasted 80kmiles, the lifter that rode on it appears to be ok, the rest of that particular lobe is very smooth just like the others, so it seems that it was rolling over it fine. BUT, this is possibly a source of harmonic noise causing my KR, car runs fine, i really dont feel like changing my lifters at this point.

top engine cleaner will probably be done tomarrow, then i'll take some logs and see where i'm at (i'll put the knock sensor settings back to stock).
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Old 08-03-2005, 11:24 AM   #11
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good chance you have a lifter thats causing that, whether it looked ok or not. is there any info to log to monitor noise from cyls by the knock sensors?
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2000 WS6 M6
Old Setup: 480 rwhp 437 rwtq with 230/232 cam and a best of 7.17@98.47 w/1.58 60'
New Setup: AFR heads, 11.6:1 CR, 90 mm ported FAST, Exo-Skel, 236/244 cam, QTP HVMC, EWP, GMMG, 9" w/4.11s
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Old 08-03-2005, 11:25 AM   #12
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remember also. those knock sensors are RIGHT at the lifters, so the slightest noise could cause it, and if it was like that before the install i would put my money on that. did the heads come off at all? when i took my heads off i cleaned the **** off my pistons and there was a good bit of it, then that would tell you you are looking in the wrong areas, esp with that bad lobe on the cam!
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2000 WS6 M6
Old Setup: 480 rwhp 437 rwtq with 230/232 cam and a best of 7.17@98.47 w/1.58 60'
New Setup: AFR heads, 11.6:1 CR, 90 mm ported FAST, Exo-Skel, 236/244 cam, QTP HVMC, EWP, GMMG, 9" w/4.11s
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Last edited by WS6FirebirdTA00; 08-03-2005 at 11:35 AM..
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Old 08-03-2005, 11:33 AM   #13
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SHINOLA! would be a very good idea to replace the lifters and elimnate them as a possible cause of knock.
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Old 08-03-2005, 11:44 AM   #14
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Quote:
Originally Posted by bigshoe
thanks guys, i'm buying seafoam today, planned on doing it today, but slept in, and now i have to go to work.

about the valve train, I had KR before and after my cam install, when i changed the cam, i changed to 918 springs and Ti retainers. now, when my old cam came out, i found this:
Click the image to open in full size.
and to be honest, i didnt notice it till the car was put back together with the new cam, it was after that, that i looked at the old cam and noticed this blemish. I made a post about it and we determined that it was a bad casting, and it lasted 80kmiles, the lifter that rode on it appears to be ok, the rest of that particular lobe is very smooth just like the others, so it seems that it was rolling over it fine. BUT, this is possibly a source of harmonic noise causing my KR, car runs fine, i really dont feel like changing my lifters at this point.

top engine cleaner will probably be done tomarrow, then i'll take some logs and see where i'm at (i'll put the knock sensor settings back to stock).
Ouch! Are you 100% sure about the lifter???
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Old 08-03-2005, 11:52 AM   #15
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the rest of the lobe on the old cam has PERFECT wear, makes me think that the lifter was just rolling right over it.

now, the new cam was smooth, and has that same lifter running on it, but still doubt thats causing the KR (i'm not ruling it out though), just because the rest of the lobe is good. I understand that at max lift, thats where most pressure is against he lifter and against the bad surface, and that maybe the other areas are so smooth since there isnt as much force running on the lobe from the maybe bad lifter. BUT what could it be? i have a feeling that the surface of the lifter roller is ok by looking at the rest of the cam wear, so what could cause that lifter to be bad and make the noise now? the bearings should be fine, i dont think they were introduced to anything that will cause slop in the roller (but who knows), and then as far as the lifter doing its job with collapsing and all that, i don't know much about how that works personally.

just trying to gain some knowledge of how it could be affecting it. changing lifters.... man, i dont want to do that
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Old 08-03-2005, 12:06 PM   #16
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doesnt matter if it was perfect, the roller could be fine and not leave marks but still make noise, trust me on this one. the bearings could be screwed in it or loose
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2000 WS6 M6
Old Setup: 480 rwhp 437 rwtq with 230/232 cam and a best of 7.17@98.47 w/1.58 60'
New Setup: AFR heads, 11.6:1 CR, 90 mm ported FAST, Exo-Skel, 236/244 cam, QTP HVMC, EWP, GMMG, 9" w/4.11s
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Old 08-03-2005, 12:08 PM   #17
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im almost positive enough about this that i would throw 1000 bucks down on that
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Sulski Performance Tuning
2000 WS6 M6
Old Setup: 480 rwhp 437 rwtq with 230/232 cam and a best of 7.17@98.47 w/1.58 60'
New Setup: AFR heads, 11.6:1 CR, 90 mm ported FAST, Exo-Skel, 236/244 cam, QTP HVMC, EWP, GMMG, 9" w/4.11s
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Old 08-03-2005, 12:29 PM   #18
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i take it the heads were off then if you looked at the lifter. that would have let you know how much build up you had. new heads too or no?
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Sulski Performance Tuning
2000 WS6 M6
Old Setup: 480 rwhp 437 rwtq with 230/232 cam and a best of 7.17@98.47 w/1.58 60'
New Setup: AFR heads, 11.6:1 CR, 90 mm ported FAST, Exo-Skel, 236/244 cam, QTP HVMC, EWP, GMMG, 9" w/4.11s
HP Tuners Forum
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Old 08-03-2005, 12:33 PM   #19
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Quote:
Originally Posted by WS6FirebirdTA00
i take it the heads were off then if you looked at the lifter. that would have let you know how much build up you had. new heads too or no?
Don't think so. He said he assumed the lifter was OK because the rest of the cam lobe didn't show scuffing from the lifter.
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Old 08-03-2005, 12:46 PM   #20
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I would not question pulling that lifter,I would just do it automatically.Theres no way those bearings in the lifter are fine after rolling over that thing for 80k miles.if you are getting kr like you say that would be my number one guess.
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Old 08-03-2005, 12:46 PM
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