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Old 12-28-2012, 10:08 PM   #1
veel86
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Default Random feedback knock

2006 STi

Turbo back exhaust (catless down pipe)
Cobb sf intake
Perrin silicone turbo inlet
Cobb stage 2 OTS 93 Octane LWG map

I'm having random feedback knock events -6 and -4. This was happening when I had my stock turbo inlet as well. I haven't been able to ketch the knock events in my logs due to how random they are, but it occurs under non acceleration or low load. Has anyone had this happen to them? Or know what could be wrong?

Thank you
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Last edited by veel86; 01-16-2013 at 08:40 PM.
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Old 12-28-2012, 10:13 PM   #2
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Also my DAM is at 1 and my fuel trims are all good.
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Old 12-28-2012, 11:20 PM   #3
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i reflashed my ecu cobb OTS stage 2 LWG map. I did this because of the new perrin silicone turbo inlet. These are logs i got after awhile of driving.

https://docs.google.com/spreadsheet/...kVoMHY2aWhpT0E

https://docs.google.com/spreadsheet/...ks3aHVDZlpzOHc

Last edited by veel86; 12-28-2012 at 11:27 PM.
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Old 12-29-2012, 08:30 AM   #4
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Low load knock corrections or corrections during throttle transitions are typically noise and something you can ignore. But, you should not be seeing very large corrections. For this car, feedback correction is done in 2 deg. steps, so with the low load "noise" you should only see -2, maybe an occasional -4, but not consistent -6 or worse. When you see those type of extreme corrections at low load, it could indicate some engine bay noise (like a rattling heatshield) that the knock sensor is picking up, for example.

Best thing to do is to get a high load wide open throttle (WOT) run, if you can do so safely. That will tell you how the car is responding. Check out our data logging video below.


Bill
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Old 12-29-2012, 10:02 AM   #5
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oh okay thank you Bill. But in my new logs i'm experiencing a lot of fine knock learning. Is my best bet getting a intake track leak test?
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Old 12-29-2012, 10:04 AM   #6
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I will try to get a 3rd WOT pull if the roads will allow it.
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Old 01-02-2013, 09:35 AM   #7
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Quote:
Originally Posted by veel86 View Post
oh okay thank you Bill. But in my new logs i'm experiencing a lot of fine knock learning. Is my best bet getting a intake track leak test?
You can look at your A/F Learning 1 A,B,C,D fuel trims over time which is a good method to determine if there are any intake leaks or other fueling related issues that are manifested in closed loop. It can take some time for these to populate accurately since the last time they are cleared which happens when you install the AccessPORT, reflash a new map, reset the ECU or disconnect the car's battery. Each individual fuel trim should be within around +/- 5%.

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Old 01-02-2013, 01:08 PM   #8
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Okay thank you very much. I will keep a close eye on it. I just recently got a p0457 CEL so I took a look at everything that could be causing it and I found that the lower hose on my purge control solenoid valve was broken. I also found a small hose with a half of it broken open. So I replaced the torn hose and ordered a new purge control valve which should be here on Thursday . Ever sense I replaced the small hose I am not experiencing the high FBKC anymore which I am happy about. Right now my learning valves are all with in a normal range. I do however smell fuel when I start my car. Should I be okay driving it till I can get the new purge valve on Thursday? And what things should I be mindful of with the p0457 CEL?
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Old 01-03-2013, 10:00 AM   #9
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Originally Posted by veel86 View Post
Okay thank you very much. I will keep a close eye on it. I just recently got a p0457 CEL so I took a look at everything that could be causing it and I found that the lower hose on my purge control solenoid valve was broken. I also found a small hose with a half of it broken open. So I replaced the torn hose and ordered a new purge control valve which should be here on Thursday . Ever sense I replaced the small hose I am not experiencing the high FBKC anymore which I am happy about. Right now my learning valves are all with in a normal range. I do however smell fuel when I start my car. Should I be okay driving it till I can get the new purge valve on Thursday? And what things should I be mindful of with the p0457 CEL?
I would replace the purge control valve that you ordered and then reset the ECU. Also, make sure your gas cap is on securely.

Bill
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Old 01-03-2013, 05:38 PM   #10
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Okay I will thank you Bill.
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Old 01-09-2013, 04:17 PM   #11
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Okay so with in the next few days the weather should permit me to be able to do a 3rd gear WOT safely. I just installed my new purge control solenoid valve and the p0457 CEL is gone. But i did do a log just cruising down the high way and i picked up a lot of high FBKC. Here is the log to show.

https://docs.google.com/spreadsheet/...nhjVjFhNllDR1E

Can anyone try and tell me what i should do? Or what could be wrong?

Thank you.
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Old 01-09-2013, 06:18 PM   #12
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Old 01-09-2013, 06:29 PM   #13
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Sorry here are the correct links
3rd gear pull
what do you guys think?

https://docs.google.com/spreadsheet/...Gd2cFhrVms2NHc

https://docs.google.com/spreadsheet/...XhpenlyS1pHWGc

Last edited by veel86; 01-09-2013 at 07:01 PM.
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Old 01-09-2013, 07:08 PM   #14
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Anyone?
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Old 01-09-2013, 08:29 PM   #15
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Could a boost leak be the cause of the FBKC? I just jacked up my car and got underneath it and discovered a nut on the bottom of the turbo to down pipe was missing.
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Old 01-10-2013, 10:26 AM   #16
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If the -6 or worse feedback correction is happening pretty consistently (but seemingly randomly) at low load, then it may still be that you have something loose/rattling in the engine bay that the knock sensor is picking up. Not sure if one missing nut on the downpipe will make noise or not, but I would replace that ASAP. Potential exhaust leaks won't cause knock in and of themselves, but obviously can be dangerous due to carbon monoxide poisoning. Intake tract leaks can cause problems such as knock - you can rule in/out most fueling issues by looking at A/F Learning 1 A,B,C,D as described earlier (over time since they are cleared when you reflash a map/reset the ecu/OR disconnect car's battery).

As far as the WOT logs, make sure you are not going WOT under 2000 RPM - that is not good for the motor. The first log shows one knock event at higher RPM, but otherwise looks fine. You are overboosting in the second log. Was the second log done at much colder temps?

Bill
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Old 01-10-2013, 02:11 PM   #17
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Oh okay ill watch my a/f values over time. There is a heat shield under the down pipe right where the down pipe connects to the turbo that only has one small bolt on the bottom holding it on and there is movement with it. Whether or not it is making noise I don't know. I tried to take it off last night but the bolt was rusted on pretty good I will try to get it off again today. I am going to the store pick up a new but for the down pipe I just need to look up the size. Ill keep searching for things that could be rattling and I have taken my BPV off several times to remove the intercooler so ill check that is sealing properly or not.

Thank you
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Old 01-10-2013, 03:56 PM   #18
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so when i was putting the new nut on the down pipe to turbo. the far left one was missing aswell. But i had bought extra nuts just in case and i put one on the far left side as well. but the bottom right side is very hard to get tight as there are other things in the way so i wasn't able to get that one tight. But i'm taking my car to the dealer tomorrow so ill have them run a intake track leak test, and tighten the down pipe to turbo nut that i'm not able to.
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Old 01-11-2013, 08:33 AM   #19
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Quote:
Originally Posted by veel86 View Post
Oh okay ill watch my a/f values over time. There is a heat shield under the down pipe right where the down pipe connects to the turbo that only has one small bolt on the bottom holding it on and there is movement with it. Whether or not it is making noise I don't know. I tried to take it off last night but the bolt was rusted on pretty good I will try to get it off again today. I am going to the store pick up a new but for the down pipe I just need to look up the size. Ill keep searching for things that could be rattling and I have taken my BPV off several times to remove the intercooler so ill check that is sealing properly or not.

Thank you
I would try to remove the lower turbo heatshield (or at least get new bolts to secure it properly). Soak the rusted bolt with PB Blaster and let it sit (maybe overnight) and you'll probably be able to get it off.

Bill
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Old 01-11-2013, 01:37 PM   #20
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Okay I will do that. I got it back from the dealer and they said they found no leaks. And the replaced the down pipe to turbo bolts and nuts. They said the MAF sensor was dirty so they cleaned that. I was driving it home and I got a -12FBKC and I have some fine knock learning 3-4000 rpm I was logging at the time.
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Old 01-11-2013, 10:29 PM   #21
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I also, the -6 through -12 knock events have mostly only occurred in 6th gear driving on the highway. They will randomly happen and go away. Also, I feel like I would notice while driving the car when i get a -12 FBKC, but the feel of the car hasn't changed at all. Should i be feeling the engine shutter or anything like that when a -12 or of similar magnitude occurs?
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Old 01-12-2013, 08:08 AM   #22
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I also, the -6 through -12 knock events have mostly only occurred in 6th gear driving on the highway. They will randomly happen and go away. Also, I feel like I would notice while driving the car when i get a -12 FBKC, but the feel of the car hasn't changed at all. Should i be feeling the engine shutter or anything like that when a -12 or of similar magnitude occurs?
Its possible you might not notice it. I would address all the potential issues that could be making noise, such as the lower turbo heatshield (and anything else). That type of random extreme correction can definitely be false knock due something rattling in engine bay.

Bill
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Old 01-16-2013, 08:06 PM   #23
veel86
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I logged my A/F Learning values in this log. I am experiencing extreme knock and i hope this can help figure out what is going on.

https://docs.google.com/spreadsheet/...TRPdlpoQTFyMnc

This log is leading to me believe that it is false knock. The learning values are all with in +/- 5.5, but there are right at that point... so i really don't know anything for sure. I really don't know what is causing the knock events and its been occurring for some time now and i could really use your guys help.

Thank you

Last edited by veel86; 01-16-2013 at 08:20 PM. Reason: more specific
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Old 01-16-2013, 08:38 PM   #24
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I could not remove the lower heat shield so i bent it so it is not touching anything or is close to anything.
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Old 01-16-2013, 09:03 PM   #25
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WOT 3rd gear pull

https://docs.google.com/spreadsheet/...nZPbmtBLTlmOGc

I do notice that i did over boost quit a bit. Cold weather possibly? But this pull did not show any FBKC or FKL.
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