LS1 KR
05-11-2009, 12:30 PM
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LS1 KR
Alright, for those of you who have had the wonderful opportunity of chasing down KR, heres my dilemma (this is also posted on some other forums)
I hooked up an HPTuners to my vette the other day to scan to see how she’s behaving under WOT. Turns out I’m hitting 6* of KR on the upper revs (5700+). (I’ll post the log here in a bit) I just filled halfway up with cam 2, bringing my combined octane to approx 99. I’m gonna scan again to see if the knock went away to rule out false knock vs if its actually pre-detonating. Questions as of now, what would be some of the things to look at if I determine it to be false knock (hitting 6* still with higher octane)?. What is normal knock for a stock LS1? (wouldn’t it ideally by 0?) Also, if it is actually knock, instead of running $100 fill ups (110 is running almost $7 a gallon
) This sound a bit over kill, but this would be an excuse for me to switch to 243 heads, put in my G5X3 cam, new lifters, stiffer springs, and LT’s.
Only mods are intake and corsa exhaust.
I hooked up an HPTuners to my vette the other day to scan to see how she’s behaving under WOT. Turns out I’m hitting 6* of KR on the upper revs (5700+). (I’ll post the log here in a bit) I just filled halfway up with cam 2, bringing my combined octane to approx 99. I’m gonna scan again to see if the knock went away to rule out false knock vs if its actually pre-detonating. Questions as of now, what would be some of the things to look at if I determine it to be false knock (hitting 6* still with higher octane)?. What is normal knock for a stock LS1? (wouldn’t it ideally by 0?) Also, if it is actually knock, instead of running $100 fill ups (110 is running almost $7 a gallon
) This sound a bit over kill, but this would be an excuse for me to switch to 243 heads, put in my G5X3 cam, new lifters, stiffer springs, and LT’s. Only mods are intake and corsa exhaust.
05-11-2009, 02:02 PM
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Re: LS1 KR
Finding out the source of knock is pretty tricky. You may not actually have knock at all, and the source of the knock retard could be engine noise picked up by the knock sensor in its resonant band. It happens. Higher octane gas will shed a little light on that, but it's really hard to replicate the same conditions to do an actual head to head comparison. As soon as the ambient temp, underhood temp, engine temp, air density, and fuel quality change, you aren't dealing with the same hand of cards.
If it's a hot day, you've got regular pump gas, and you've been driving around for a while so the underhood heatsoak is pretty thorough, some minor detected knock is not uncommon on a performance engine.
Having a little knock retard some of the time under some conditions is a lot better than having a tune that is so conservative that it never knocks at all. That's the beauty of modern ECUs with knock retard.
Oh, you could try to reset the ECU to get rid of any fuel trim and other stored parameters and see if that helps. That sometimes goes a long way if you've got conservative trims because you don't drive the car in anger very often.
If it's a hot day, you've got regular pump gas, and you've been driving around for a while so the underhood heatsoak is pretty thorough, some minor detected knock is not uncommon on a performance engine.
Having a little knock retard some of the time under some conditions is a lot better than having a tune that is so conservative that it never knocks at all. That's the beauty of modern ECUs with knock retard.
Oh, you could try to reset the ECU to get rid of any fuel trim and other stored parameters and see if that helps. That sometimes goes a long way if you've got conservative trims because you don't drive the car in anger very often.
Last edited by Fabrik8; 05-11-2009 at 02:06 PM.
