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Thread: False Knock at 2000 RPM and .20 g Aircharge on Blown 392

  1. #1
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    False Knock at 2000 RPM and .20 g Aircharge on Blown 392

    Hi all,

    I am looking for a little advice with regards to a knock retard issue that I am having on a 2012 Whipple supercharged 392 challenger. I have an issue wherein I periodically see minor knock retard of .5 to 1 degree of timing pulled in the area of ~2000 rpm and ~.20 g of aircharge. I have seen this on a number of my logs and have been pulling timing in repeated iterations of my tune in the base spark table to compensate for it. I have now pulled up to 4 degrees of timing in this area of the table and am still seeing the minor knock (again never above 1 degree). I am wondering if this is false knock, but I am hesitant to ignore or tune it out if there is really something happening there. The knock sensors have already been somewhat desensitized from the tune I got from Whipple with my kit (adding up to .3V to the threshold). Cylinder 1 has a knock threshold of 1.198V at 1,800 RPM and 1.597 V at 2500 RPM. Has anybody seen this before? A picture of one of my logs along with my base spark table is attached.

    I am concerned as this area is the area that my car spends a lot of time in as I am on the highway at ~60 MPH in 6th gear. Any thoughts would be appreciated.


    THANKS!

    Blown 392
    Attached Images Attached Images

  2. #2
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    Looks a lot like false knock, have you checked over the entire car looking for any metal to metal contact? I would look around the back of the blower and make sure nothing is hitting, exhaust too, esp the midpipes and 02 sensors.

  3. #3
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    Thanks 06300CSRT8! I appreciate the feedback as I am pretty sure it is false knock. I have looked around to see if anything is hitting, and I am pretty sure nothing is. I do have a tight fitting wideband O2 on the passenger side as there was no good place to mount it forward of the cat. This said, I don't think I will be able to put it anywhere else and I am thinking of just tuning it out. Thanks again for your help!
    All the best!

  4. #4
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    have you tried adding some octane booster or a gallon or 2 of race gas?? if you try that and pulled some timing in that area along with the previous mention methods i would have to agree that its false knock. Just be careful as to not go crazy as how much to desensitize the knock sensor as they do a better job at hearing knock than you can.. Just my opinion.

  5. #5
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    Quote Originally Posted by blown392 View Post
    Hi all,

    I am looking for a little advice with regards to a knock retard issue that I am having on a 2012 Whipple supercharged 392 challenger. I have an issue wherein I periodically see minor knock retard of .5 to 1 degree of timing pulled in the area of ~2000 rpm and ~.20 g of aircharge. I have seen this on a number of my logs and have been pulling timing in repeated iterations of my tune in the base spark table to compensate for it. I have now pulled up to 4 degrees of timing in this area of the table and am still seeing the minor knock (again never above 1 degree). I am wondering if this is false knock, but I am hesitant to ignore or tune it out if there is really something happening there. The knock sensors have already been somewhat desensitized from the tune I got from Whipple with my kit (adding up to .3V to the threshold). Cylinder 1 has a knock threshold of 1.198V at 1,800 RPM and 1.597 V at 2500 RPM. Has anybody seen this before? A picture of one of my logs along with my base spark table is attached.

    I am concerned as this area is the area that my car spends a lot of time in as I am on the highway at ~60 MPH in 6th gear. Any thoughts would be appreciated.


    THANKS!

    Blown 392
    Something I found might help
    Im using the Mahle forged pistons and they rattle quite a bit when cold , it disappears once oil temp gets above 90 odd degrees however the car will log long term Knock during this period so you keep seeing the retard ,
    I had HP add temp enable to both ST knock and LT knock and I have these set at 90 deg. c. so as long as I treat it nicely in the first 10 mins or so the problem does not eventuate , I also upped the Knock thresholds similarly as you have
    Hope its useful NP

  6. #6
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    Quote Originally Posted by Nigel Pitsch View Post
    Something I found might help
    Im using the Mahle forged pistons and they rattle quite a bit when cold , it disappears once oil temp gets above 90 odd degrees however the car will log long term Knock during this period so you keep seeing the retard ,
    I had HP add temp enable to both ST knock and LT knock and I have these set at 90 deg. c. so as long as I treat it nicely in the first 10 mins or so the problem does not eventuate , I also upped the Knock thresholds similarly as you have
    Hope its useful NP
    I believe this is the same problem I am having but where is the setting for the temp enable for the knock detection.

  7. #7
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    Quote Originally Posted by Nigel Pitsch View Post
    Something I found might help
    Im using the Mahle forged pistons and they rattle quite a bit when cold , it disappears once oil temp gets above 90 odd degrees however the car will log long term Knock during this period so you keep seeing the retard ,
    I had HP add temp enable to both ST knock and LT knock and I have these set at 90 deg. c. so as long as I treat it nicely in the first 10 mins or so the problem does not eventuate , I also upped the Knock thresholds similarly as you have
    Hope its useful NP
    Out of curiosity, how do you get HP Tuners to add parameters for you in their definitions? Every time I ask if they can possibly define certain parameters, I'm given a reply to the effect of:

    Capture.PNG

    This was a response I received today after asking if HP Tuners plans to ever look into adding/defining injection timing parameters for Chrysler/Jeep/Dodge gas applications, like they have done with the GM stuff.

  8. #8
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    Usually when asking for parameters it has to be something you’ve seen in another tune and can give them the specific table name/ID number, or in my case I gave them screen shots from Diablo CMR. They don’t typically start from scratch for new parameters in an older tune

  9. #9
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    Quote Originally Posted by Nigel Pitsch View Post
    Something I found might help
    Im using the Mahle forged pistons and they rattle quite a bit when cold , it disappears once oil temp gets above 90 odd degrees however the car will log long term Knock during this period so you keep seeing the retard ,
    I had HP add temp enable to both ST knock and LT knock and I have these set at 90 deg. c. so as long as I treat it nicely in the first 10 mins or so the problem does not eventuate , I also upped the Knock thresholds similarly as you have
    Hope its useful NP
    Nigel can you post your tune so I can request these tables by name to be added to my tune?

  10. #10
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    Quote Originally Posted by 06300CSRT8 View Post
    Usually when asking for parameters it has to be something you’ve seen in another tune and can give them the specific table name/ID number, or in my case I gave them screen shots from Diablo CMR. They don’t typically start from scratch for new parameters in an older tune
    Yeah, I've sent in screen shots of various parameters over the years from competitor software, and even offered to submit stock and modified files (modified using competitor software) to make diff comparisons easy to spot changes for their engineers, and was told that it was a no go.

    Guess it just depends entirely on the mood of the individual answering support emails on any given day.

  11. #11
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    Are you logging both knock sensor voltages? This can help in determine if you are getting real or false knock depending on the voltages.

  12. #12
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    Quote Originally Posted by Jay@HAP View Post
    Are you logging both knock sensor voltages? This can help in determine if you are getting real or false knock depending on the voltages.
    Chasing my own false knock, what is the voltage signature that suggests false knock?

  13. #13
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    The tuning school suggests real knock is cascading where as false is more random pulse(s).

    start at 3:30
    https://www.youtube.com/watch?v=ScjfTGLnpPk

  14. #14
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    Sorry I haven't been here for a while I have been trying to post a screen shot but not succeeding,
    Under Spark -- Retard -- Short term Knock ---ST Enable temp. then
    Long Term Knock ---- LT enable temp
    ( ECM - 13550 ). Page code

  15. #15
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    I logged Long and short term Knock. , so I could see what it was doing
    If the car logs long term KNK as it will when its cold it will keep pulling timing every time its in that area , until it gets reset that is
    Once its above 90 Deg C oil temp its quiet so
    Once you turn the car off for a couple mins the log is cleared and the car runs fine , as its now hot and does not log the Knk
    Setting the Knk Thresholds at 90 has helped heaps , I wish that they could be linked to oil temp as that is really the best option but unfortunately its linked to water temp,
    But it is a big improvement !