Knock Retard
11-14-2003, 11:04 AM
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Knock Retard
I have a 99 GMC Sierra that has a LS1 from a 99 Trans AM. I am using the truck intake and computer. The only mods I have is a UPD lid, polished throttle body(not de-screened) and a Magnaflow cat back exhaust.
I dynoed my truck a couple of weeks ago and got 250 rwhp & 296 lb/ft of torque.
I am seeing LTFT at approximately +6 to +8. My biggest problem is I am getting knock retard beginning at 70% throttle and it finally pulls 5 to 7 degrees of timing at WOT. Max timing is 14 to 15 degrees at WOT.
I do not see anything that would cause a false knock.
The knock sensors are the ones from the LS1 engine. Would this cause a problem?
Any help is greatly appreciated.
Tony
I dynoed my truck a couple of weeks ago and got 250 rwhp & 296 lb/ft of torque.
I am seeing LTFT at approximately +6 to +8. My biggest problem is I am getting knock retard beginning at 70% throttle and it finally pulls 5 to 7 degrees of timing at WOT. Max timing is 14 to 15 degrees at WOT.
I do not see anything that would cause a false knock.
The knock sensors are the ones from the LS1 engine. Would this cause a problem?
Any help is greatly appreciated.
Tony
11-14-2003, 02:22 PM
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I made the LS1 swap (2000 Vette) in my 2000 Tahoe and had similar issues with KR. My truck tuning had the LTFT's in line at 0<LTFT<2 but I experienced a lot of tip-in KR, so much that it would peg KR. A $100 tank of 100 octane proved to me that my KR was false. I tuned my max retard value so it wouldn't pull as much timing and I also tuned it to restore timing faster. I still see KR from time to time on tip in, but it maxes out at 4* now.
Do you have ls1edit? Since your KR really begins at 70% throttle do you think it is a Performance Enrichment issue. With positive LTFT's it could be a rich knock. I know that O2 voltages aren't to be relied upon for tuning, but what values are you seeing when the knock starts?
Do you have ls1edit? Since your KR really begins at 70% throttle do you think it is a Performance Enrichment issue. With positive LTFT's it could be a rich knock. I know that O2 voltages aren't to be relied upon for tuning, but what values are you seeing when the knock starts?
11-14-2003, 07:45 PM
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I have LS1edit and Ease Diagnostics.
The truck runs really good, has lots of low end torque. I am using the truck computer and the only changes I have made so far is to correct the IFR table because I am using the stock LS1 injectors from the Trans Am and delete torque management.
How and where in the circuit did you wire the resistors?
How can I change the sensetivity of the sensors, what are the exact steps?
I read in the PCM section of some of the F-bodies having their PCMs flashed with an updated software. Does anyone know if there is an update available for our trucks that might minimize the knock retard?
If I want my LTFTs to go minus, currently +6 to +8 do I multiply the IFR table by 107%. I have version 1.21 of edit.
Thanks,
Tony
The truck runs really good, has lots of low end torque. I am using the truck computer and the only changes I have made so far is to correct the IFR table because I am using the stock LS1 injectors from the Trans Am and delete torque management.
How and where in the circuit did you wire the resistors?
How can I change the sensetivity of the sensors, what are the exact steps?
I read in the PCM section of some of the F-bodies having their PCMs flashed with an updated software. Does anyone know if there is an update available for our trucks that might minimize the knock retard?
If I want my LTFTs to go minus, currently +6 to +8 do I multiply the IFR table by 107%. I have version 1.21 of edit.
Thanks,
Tony
11-14-2003, 08:45 PM
#7
you will need to reduce the ifr number to get your ltrims to go down. not exaxtly sure how much but multiplying by .93 would probably be a good starting point.
i tried using edit to get rid of "false knock", you can make it a little better but not much, i recomend you first test to make 100% sure that it is false knock. then if it does apear to be false knock you can try what i did by just adding resistors. worked great on my truck, i went from high 14's to mid 13's, i was really bateling false knock.
first to check for false knock you need to monitor it and get a good feel for when it is hapening and how much, once you know that then put in some good gas. try and run your truck low on fuel and then put in 5 gallons of 100 and re log, if the KR gets no better at all then you probably have false knock.
the resistor mod worked on my 99. there is a conector at the back of the intake on top that goes to the 2 knock sensors under the intake, one wire to each sensor. i took 1 10k ohm resistor and wired in series with each knock sensor wire, that is one resistor per wire. boom 100hp i bet.
CAUTION!! if you ignor real knock you will probably break a piston!!!! i am not responsible.
i tried using edit to get rid of "false knock", you can make it a little better but not much, i recomend you first test to make 100% sure that it is false knock. then if it does apear to be false knock you can try what i did by just adding resistors. worked great on my truck, i went from high 14's to mid 13's, i was really bateling false knock.
first to check for false knock you need to monitor it and get a good feel for when it is hapening and how much, once you know that then put in some good gas. try and run your truck low on fuel and then put in 5 gallons of 100 and re log, if the KR gets no better at all then you probably have false knock.
the resistor mod worked on my 99. there is a conector at the back of the intake on top that goes to the 2 knock sensors under the intake, one wire to each sensor. i took 1 10k ohm resistor and wired in series with each knock sensor wire, that is one resistor per wire. boom 100hp i bet.
CAUTION!! if you ignor real knock you will probably break a piston!!!! i am not responsible.
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11-14-2003, 08:48 PM
#8
AND, just in case you were wondering the knock sensors still worked. i did all my tuning based on my knock sensor readings, i could go 6-7lb but not 8, good gas then i could 9-10lb. i tuned to the limit of the gas i had by watching the knock sensors.
11-15-2003, 02:06 AM
#9
Interesting. On my old truck, I ran Nineballs, Knock Out box, which s probably just like the resistor mod, packaged into a plug in module. ANyway, it removec lots of my KR problems. I rarely saw any knock after that. I put the KObox on this new 03 truck, and I still see 6* of KR in 1st gear. Not sure if the KR is real knock, or a value given up by torque management or something else to reduce timing. I only see it in 1st gear, then it decays out to 0 after a few seconds.
11-17-2003, 09:41 AM
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Originally Posted by parish8
AND, just in case you were wondering the knock sensors still worked. i did all my tuning based on my knock sensor readings, i could go 6-7lb but not 8, good gas then i could 9-10lb. i tuned to the limit of the gas i had by watching the knock sensors.
parish8,
Any chance you have a picture of the 10 ohm resistor, or better yet a picture of them installed?