Results 1 to 13 of 13

Thread: still chasing phantom burst knock.. ideas?

  1. #1
    Tuner in Training
    Join Date
    Jan 2013
    Posts
    15

    still chasing phantom burst knock.. ideas?

    heres a coupe clips of my logs i keep getting this random burst knock pretty sure i have disabled it but maybe someone can walk me through it?? 1998 camaro with a 5.3 iron block 228r cam stalled auto im working off the 98 ls1 tune. it seems to only burst knock when i floor it you can see that the knock retard and burst knock are about the same idk whats going on. i have a older hptuners cable so alot of you may not be able to view my tune.. the one i attached is an older one but i havent changed alot



    Attached Files Attached Files

  2. #2
    Tuner in Training
    Join Date
    Jan 2013
    Posts
    15
    could it be a lean spike? wonder if i should change my power enrichment tps enable?

  3. #3
    Tuner in Training
    Join Date
    Oct 2013
    Location
    SOUTH TEXAS
    Posts
    10
    you could give it a try... and mess around with the PE and tps

  4. #4
    Tuner
    Join Date
    Jan 2013
    Location
    Delaware
    Posts
    67
    I cant see what your actual AFR is under WOT but your Commanded AFR is 12.08, which in my opinion is really rich for a naturally aspirated 5.3, 13.5 is probably best. I guess you have tried pulling timing already? go to burst knock, enable delta cylinder air table under Spark, Retard. increase your value by 10% from 4000 down until you don't have burst anymore. btw burst knock tries to predict a knock event before it happens to prevent getting knock in the first place, its not really a bad thing to have active

  5. #5
    Tuner in Training
    Join Date
    Jan 2013
    Posts
    15
    i have the enable delta cylinder air maxed out at 8, im trying to get rid of it because it has to be false i only get it on throttle transitions i think i've read somewhere when you have a cam it could cause it... and i've been fighting a lean issue in the tune i just got it figured out my afrs use to be 14.0 at wot now they are down to 13.5-13.3-13.0 by redline.

  6. #6
    Tuner in Training
    Join Date
    Jan 2013
    Posts
    15
    another thing it seems like if i roll into it it doesnt do it or doesnt do it nearly as bad, seems only violent throttle transitions is when i get it (if i were to pedal it the burst knock would come up then slowly go away). its a 98 car so it could just be the computer having a brain fart it had new knock sensors and harness put in when i installed the motor.

  7. #7
    Tuner
    Join Date
    May 2013
    Location
    Houston
    Posts
    105
    Have you tried taking out timing in that area 2 or 3* at a time and see if it starts to go lower?

  8. #8
    Advanced Tuner n0dih's Avatar
    Join Date
    Mar 2006
    Location
    Cherry Valley, IL
    Posts
    391
    Air moves faster than fuel, so the potential of burst knock is high, hence the PCM is designed in the code to pull timing to reduce or prevent it.

    You need fuel that moves faster than the burst of air when you nail the gas.

    Greg Banish talks about this in his book (first one I think).

    Look at your log, when the knock appears the rear O2 also goes lean. So it is quite possibly a lean condition that isn't characterised properly. Try to add more fuel, see if you can control it with fuel.

    Don't tune by narrowband, anything over 450mv or under is unreliable data, it was never intended to be accurate. Seeing your front O2 is at 820mv and not well over 900 is suspect that it is still on the lean side.

    Do you have any possibility of a cat that is partially plugged? But looking at the rear O2 sensor it might be telling you a story there. eve 1 psi backpressure can cause issues, and if it is confusing the AFR it will have tendacy to ping easy because the AFR may "look" ok on the NB, but it isn't. Which might explain the rear O2 readings.
    Last edited by n0dih; 11-07-2013 at 05:45 PM.

  9. #9
    Tuner in Training
    Join Date
    Jan 2013
    Posts
    15
    i've tried pulling timing, i've pulled so much that i finally went back to my original tune because im almost certain thats not the issue. and i have my cats deleted as well as my rear o2s. the light blue o2 sensor in the graph is actually my innovate mtxl wideband simulating the narrowband signal (passenger side)... so those really arent accurate to go off of its deff. lean out of the hole so im gonna tweak my power enrichment tps enable and see what happens ill report back.

  10. #10
    Tuner in Training
    Join Date
    Jan 2013
    Posts
    15
    well i set it fairly low and still got it.. ill post up tomorrow

  11. #11
    Tuner in Training
    Join Date
    Jan 2013
    Posts
    15
    bueller

  12. #12
    Senior Tuner SultanHassanMasTuning's Avatar
    Join Date
    Nov 2009
    Location
    All Around
    Posts
    3,149
    seems like your MAF tuning I dont like them on LS1/ older PCM's I feel that they are too slow. I recommend converting to SD also convert your fuel control to open loop.
    Follow @MASTUNING visit www.mastuned.com
    Remote Tuning [email protected]
    Contact/Whatsapp +966555366161

  13. #13
    Tuner in Training
    Join Date
    Jan 2013
    Posts
    15
    the maf is descreened, might be causing an issue. i've cleaned it a couple times but its old and sat for a while before i got the car and fixed it.