Moderate Engine Knock Detected- Cobb AP
+ Reply to Thread
Results 1 to 11 of 11

This is a discussion on Moderate Engine Knock Detected- Cobb AP within the Tuning: Electronic Engine Management forums, part of the Tech & Modifying & General Repairs category; I am going to moving up to stage 2 here soon and wanted to get to know my machine a ...

  1. #1
    Registered User
    Join Date
    Oct 2012
    Location
    Central, Pa
    Posts
    45

    Moderate Engine Knock Detected- Cobb AP

    I am going to moving up to stage 2 here soon and wanted to get to know my machine a little bit better before i just start throwing mods on. I've read a good article on how to look at this stuff but its just not really clicking yet, so i did about a 40 min data log. It starts cruising at highway speed then towards the end it is all country roads. Earlier today when i noticed knock i retarded the timing 1 degree but obviously didn't help. The only mods i have done to my car are Cobb AP Stage 1 93 (-1 Degree), Spt cat back and Spt boost gauge. Datalog1-2.txt

    EDIT: I don't know how to neaten this up but at Time:659.07 -1.4 is the feedback knock
    Last edited by Ryno10rex; 11-30-2013 at 10:24 PM.

  2. Remove Advertisements
    ClubWRX.net
    Advertisements
     

  3. #2
    Admiral Ackbar the 1st mycologist's Avatar
    Join Date
    Oct 2005
    Location
    Late Devonian
    Posts
    13,315
    I Support ClubWRX
    That is pretty weird. Yeah though, pulling 1 degree isn't going to do anything about that.

    It is a low RPM low throttle log and without even changing throttle position, speed, or load it all of a sudden pulls timing and keeps on pulling it until -11 and there is no learned knock in that area. I wish I could see what an accurate A/F sensor would have shown. BTW, -11 is massive, not moderate. If I am reading it right I'd be concerned enough not to drive it into boost.

    I think for it to pull that much timing and not correct itself it was either a packet of crappy gas (maybe some water) or myabe your knock sensor is loose and rattling around at that RPM? Maybe there is a tear in an intake hose or a leak that opens up massively at times (seems unlikely)?
    "From a little spark may burst a mighty flame." - Dante
    "The stitch is lost unless the thread is knotted." - Italian proverb

  4. #3
    Registered User
    Join Date
    Oct 2012
    Location
    Central, Pa
    Posts
    45
    I value and appreciate your opinion but that puts me between a rock and a hard spot considering its my DD. That is the only time I've seen it spike that high so far. I will try to post the other part of the log that gradually hits -1.4 then gradually declines. Also I've done several WOT on the same log from ~2500 rpm up to 5700 rpm and each time no knock whatsoever showed up. Seemed to happen all between the 2500 and 3000 rpm cruising. I will put another section of the log into the next post.

  5. #4
    Registered User
    Join Date
    Oct 2012
    Location
    Central, Pa
    Posts
    45
    Is the knock sensor accessible from the outside of the engine? And what do you think about turning back to the stage 1 lower octane fuel tune to help it until i can figure this problem out?

    Here are the parts of the log of what the "normal" knock looks like and a boosted pull with no knock.Datalog2.txt

  6. #5
    MAINEiac 11blackSTi's Avatar
    Join Date
    Nov 2012
    Location
    Land of the Port. ME
    Posts
    2,898
    I Support ClubWRX
    I have a hard time seeing the text files line up with the columns, but am I seeing it correct that the column that builds from -1.4 to -11.8 is feedback knock? If so, that is a serious issue. Are you running 93 octane fuel in your car?

    Probably not the cause of knock up to levels of 11.8, but out of curiousity...Do you drive around with your defrost on all the time?

  7. #6
    Admiral Ackbar the 1st mycologist's Avatar
    Join Date
    Oct 2005
    Location
    Late Devonian
    Posts
    13,315
    I Support ClubWRX
    If you don't see it again, it was the gas IMO.
    "From a little spark may burst a mighty flame." - Dante
    "The stitch is lost unless the thread is knotted." - Italian proverb

  8. #7
    Registered User
    Join Date
    Oct 2013
    Posts
    24
    Quote Originally Posted by 11blackSTi View Post
    I have a hard time seeing the text files line up with the columns, but am I seeing it correct that the column that builds from -1.4 to -11.8 is feedback knock? If so, that is a serious issue. Are you running 93 octane fuel in your car?

    Probably not the cause of knock up to levels of 11.8, but out of curiousity...Do you drive around with your defrost on all the time?
    Is there an issue with constantly having the defroster on? Here in New England I find myself doing this fairly consistently.

  9. #8
    Admiral Ackbar the 1st mycologist's Avatar
    Join Date
    Oct 2005
    Location
    Late Devonian
    Posts
    13,315
    I Support ClubWRX
    Quote Originally Posted by Ryno10rex View Post
    Is the knock sensor accessible from the outside of the engine? And what do you think about turning back to the stage 1 lower octane fuel tune to help it until i can figure this problem out?

    Here are the parts of the log of what the "normal" knock looks like and a boosted pull with no knock.Datalog2.txt
    Stage one map is NOT recommended for a stage II car.

    Yes, the knock sensor is outside the motor.

    Knock Sensor Location - Subaru Impreza WRX STI Forums: IWSTI.com

    It has to be torqued to the right spec. and it has to be in the correct orientation (clocking). I did one on an outback without removing the manifold - you need to take off the TMIC and it will still be hard to get to (they mention a crows-foot). If you replace it, use ONLY OEM (or the exact same part from the manufacturer). I found a real OEM one for cheap on ebay or the outback.
    "From a little spark may burst a mighty flame." - Dante
    "The stitch is lost unless the thread is knotted." - Italian proverb

  10. #9
    Registered User
    Join Date
    Oct 2012
    Location
    Central, Pa
    Posts
    45
    Quote Originally Posted by 11blackSTi View Post
    I have a hard time seeing the text files line up with the columns, but am I seeing it correct that the column that builds from -1.4 to -11.8 is feedback knock? If so, that is a serious issue. Are you running 93 octane fuel in your car?

    Probably not the cause of knock up to levels of 11.8, but out of curiousity...Do you drive around with your defrost on all the time?
    Yes I run 93 and i'm as particular as I can be when it comes time to fill up the tank. I hardly use the defroster maybe on a cold morning, for random knowledge though what affect does that have?





    Quote Originally Posted by mycologist View Post
    Stage one map is NOT recommended for a stage II car.

    Yes, the knock sensor is outside the motor.

    Knock Sensor Location - Subaru Impreza WRX STI Forums: IWSTI.com

    It has to be torqued to the right spec. and it has to be in the correct orientation (clocking). I did one on an outback without removing the manifold - you need to take off the TMIC and it will still be hard to get to (they mention a crows-foot). If you replace it, use ONLY OEM (or the exact same part from the manufacturer). I found a real OEM one for cheap on ebay or the outback.
    I am still stage 1, but not for to much longer! I will go with the bad gas theory and keep a close eye on it.

  11. #10
    MAINEiac 11blackSTi's Avatar
    Join Date
    Nov 2012
    Location
    Land of the Port. ME
    Posts
    2,898
    I Support ClubWRX
    Quote Originally Posted by Ryno10rex View Post
    for random knowledge though what affect does that have?
    I've noticed that if I drive around with the A/C or defroster on then I will get random knock events (mostly low boost, not full throttle, as the defroster is disabled at WOT). Not large amounts of knock (below -4 ish), but without them on I never get knock.

  12. #11
    Registered User
    Join Date
    Oct 2012
    Location
    Central, Pa
    Posts
    45
    Good to know and troubleshoot if i see this problem in the future. Thanks guys

+ Reply to Thread

Quick Reply Quick Reply

Register Now

Please enter the name by which you would like to log-in and be known on this site.
If you do not want to register, fill this field only and the name will be used as user name for your post.

Please enter a password for your user account. Note that passwords are case-sensitive.

Please enter a valid email address for yourself. We strongly suggest that you stay away from using aol, yahoo, msn, and hotmail accounts. Sometimes the mail server blocks the emails from our server. As a result you will not receive any notifications including the confirmation email.

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.


Posting Permissions

  • You may post new threads
  • You may post replies
  • You may not post attachments
  • You may not edit your posts
  •