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Knock Retard Question

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Old May 16, 2010 | 11:01 PM
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Default Knock Retard Question

How is it possible to be getting 8 degrees of knock retard at 55% tp with a air/fuel at 10.6 at 5psi of boost? I mean you can be any where below 55% tp and floor it with no retard but above that the instant u roll into the throttle it goes right to 8 degrees retard?
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Old May 16, 2010 | 11:03 PM
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and it doesn't matter what pulley i have on. From a pulley that makes 7-8psi or one that makes 10-11 psi it does the same thing.
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Old May 17, 2010 | 01:41 AM
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have you zero'd your burst knock tables?

When ever I'm having a timing issue I use a config file that has every single timing pid available in the table. KR does not necessarily mean it knocking.
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Old May 17, 2010 | 06:20 AM
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While tuning mine on the dyno it constantly pulled 7 deg. They even set total timing at only 3 deg and it still pulled 7 deg. They ended up turning the sensors off and made several pulls while checking the spark plugs, afr... I made max power with only 12 deg so they just left them off thinking they were picking up noise from the blower.
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Old May 17, 2010 | 04:51 PM
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Originally Posted by waterdog
While tuning mine on the dyno it constantly pulled 7 deg. They even set total timing at only 3 deg and it still pulled 7 deg. They ended up turning the sensors off and made several pulls while checking the spark plugs, afr... I made max power with only 12 deg so they just left them off thinking they were picking up noise from the blower.
THAT is scary!
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Old May 17, 2010 | 08:18 PM
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Mine was doing basically the same thing after I put the cam, dual springs, 3" pulley, and louder exhaust on. I never had any KR prior to these changes and was running 16*-19* of timing under boost. I dropped the timing clear to 6* and it made no difference.

I was pretty sure it was the exhaust or springs or a combination. The KR was at throttle roll-in from steady-state cruise; if I kept rolling into the throttle I could keep the KR running. As soon as I let off the throttle the KR would immediately decay to zero. The KR was typically right where the exhaust had the highest resonance - it is bad enough that it's vibrating the floorboards noticeably at its peak.

I ended up tweaking the knock sensor Tip in TPS and Tip in RPM slightly in the areas where there was KR, 1600-2800 rpm, and also desensitizing the knock sensors slightly in the same area. The KR was gone after the first small tweaks. I bumped the timing back up to 12* and was still good. I am planning to bump it back to 14* in those areas next, scan it, and call it good. I'm also adding a resonator to the exhaust and then increasing the knock sensor sensitivity back where it was to see what happens; the exhaust is resonating a little too much for my liking.
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Old May 17, 2010 | 11:14 PM
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It could be a bad knock sensor.... when they or one of them is bad it automatically pulls 8 degs past 55% throttle
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Old May 18, 2010 | 08:48 AM
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This dam thing is moody. Last night i was out testing and the knock retard was at the most 3 degrees retard and that was a totally different tp have before. But that's the way its been with this truck it is always something different just depends on the day.

Blown 06-As far as the burst knock table not sure what they are set at.

Avalanche2002-This a happened after i put on headers and the cam.

00Z71-I put new GM knock sensors in at the time the 6.0 was installed w/cam and headers. It seems like ever since then it has set a po327 code.
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Old May 18, 2010 | 12:04 PM
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Do you hear the actual knocking outside the vehicle? the only reason why I'm asking is because, I'm having similiar issues and I'm about ready to burn my truck..#7
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Old May 18, 2010 | 10:05 PM
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no i can't hear any detenation and i have a pretty sharp ear for it. I can hear it in other vehicles when other people cant. I am guessing the majority is a false knock. My tuner is looking into a couple things on his tune so we will see.

Last edited by SpdFrk; May 18, 2010 at 10:05 PM. Reason: more info
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