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Old 10-06-2013, 05:07 PM   #1
olenderc
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Default Consistent feedback knock/fine knock when depressing throttle.

I'm running Cobb OTS Stage 1 91v300 on 93 octane fuel. Car is a 2013 WRX.

Tune has been running fine, no knock on WOT, only I occasionally see a -1.4 blip or so randomly at partial throttle. Seems like it's usually during sudden minor throttle changes. I always drive with the accessport on and live monitoring feedback knock and fine knock learning, which is why I noticed this sudden change in behavior.

Just today, however, I noticed when shifting around 3k - 4k or higher, I'll get a consistent and reproducible -1.4 knock and around that area, upon lifting my foot off the throttle to change gears. Doesn't happen much at all if I shift at lower rpm's mainly below 2.5k.

First log is shifting from 1st, through 3rd: https://docs.google.com/spreadsheet/...nc&usp=sharing

Second log of 3rd gear partial throttle rev then letting off gas: https://docs.google.com/spreadsheet/...3c&usp=sharing

Third log is of a short WOT in 3rd gear, notice no knock really until the end when I'm letting off the throttle: https://docs.google.com/spreadsheet/...1E&usp=sharing

Haven't seen this before, I'm not sure what would suddenly cause this, and I'm not sure if this is something to worry about. Thanks for your time.
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Old 10-06-2013, 06:58 PM   #2
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Flash the 91 or 91 ACN map (with 93 in the tank) and see if it still persists. They have more conservative timing. What do your fuel trims look like? (AF Learning #1 A,B,C,D). You can pull those up at idle. Do that before you flash, because they will be reset.
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Old 10-06-2013, 07:05 PM   #3
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Originally Posted by nmlittlebigman View Post
Flash the 91 or 91 ACN map (with 93 in the tank) and see if it still persists. They have more conservative timing. What do your fuel trims look like? (AF Learning #1 A,B,C,D). You can pull those up at idle. Do that before you flash, because they will be reset.
I already am using the stage 1 91 oct map on 93 octane gas. The tune has been relatively fine up until today, and never had reproducible -1.4 knock upon letting off the gas pedal. Not really sure what would cause this type of change. Would a fueling issue have anything to do with causing knock on letting off the gas? I'll take a look at fuel trims and see if anything stands out.
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Old 10-06-2013, 07:14 PM   #4
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Sorry I derped when I read your post.
Can you log the default parameters list too. They will include AF Sensor 1 (your front 02), AF Corrections and AF Learning 1. They may tell us whether or not it is fueling related.
As for other things, loose bolts, brackets, mounts can all trigger the knock sensor.
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Old 10-06-2013, 07:17 PM   #5
olenderc
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Originally Posted by nmlittlebigman View Post
Sorry I derped when I read your post.
Can you log the default parameters list too. They will include AF Sensor 1 (your front 02), AF Corrections and AF Learning 1. They may tell us whether or not it is fueling related.
As for other things, loose bolts, brackets, mounts can all trigger the knock sensor.
I'm going to pick up some food now so I'll take a log or two, should I add just the fuel trims or plain default variables?
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Old 10-06-2013, 07:27 PM   #6
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I would use the default list. You can pull up AF Learning #1 A,B,C,D and post the numbers. They should all be +/- 8% ideally.
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Old 10-06-2013, 08:09 PM   #7
olenderc
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Back from my ride. Here are the logs. Fuel trims seemed to be okay, AF learning 1 never went outside of -3.91/.78. Not sure what else you can gather from the logs. I can pretty much replicate the same -1.4 knock every single time I shift a little higher than 3-3.5k. Haven't seen a knock greater than -1.4 that I recall.

log 1 (partial throttle, shift from 2nd to 3rd): https://docs.google.com/spreadsheet/...2c&usp=sharing

log 2 (partial throttle, shift from 3rd to 4th): https://docs.google.com/spreadsheet/...Wc&usp=sharing

log 3 (partial throttle, shift from 1st through 3rd): https://docs.google.com/spreadsheet/...VE&usp=sharing

log 4 (short WOT in 3rd): https://docs.google.com/spreadsheet/...2c&usp=sharing
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Old 10-06-2013, 08:29 PM   #8
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Fuel trims look fine. You probably need to get some guidance from COBB. They usually check this forum several times a day with the exception of weekends.
Good Luck
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Old 10-06-2013, 08:32 PM   #9
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Originally Posted by nmlittlebigman View Post
Fuel trims look fine. You probably need to get some guidance from COBB. They usually check this forum several times a day with the exception of weekends.
Good Luck
Is it possible something is "loose?" I did a quick visual check but didn't really check any bolts as I wouldn't really know which exact ones to check specifically that would cause perceivable knock to the sensor. Thanks otherwise, I guess I'll have to wait and see if I could get some feedback from COBB.
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Old 10-06-2013, 08:39 PM   #10
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Quote:
Originally Posted by olenderc View Post
Is it possible something is "loose?" I did a quick visual check but didn't really check any bolts as I wouldn't really know which exact ones to check specifically that would cause perceivable knock to the sensor. Thanks otherwise, I guess I'll have to wait and see if I could get some feedback from COBB.

Heat shields (especially aftermarket) have been known to trigger a few knock sensors. Other than that there's a myriad of things that can cause similar noises that the knock sensor thinks is detonation. You have a pretty new vehicle with virtually no mods so I wouldn't think you would have a loose or broken bolt, bracket etc.
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Old 10-06-2013, 08:48 PM   #11
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Quote:
Originally Posted by nmlittlebigman View Post
Heat shields (especially aftermarket) have been known to trigger a few knock sensors. Other than that there's a myriad of things that can cause similar noises that the knock sensor thinks is detonation. You have a pretty new vehicle with virtually no mods so I wouldn't think you would have a loose or broken bolt, bracket etc.
Well, I'm at least hoping that this isn't knock to be of immediate concern specific to engine health? Obviously, something is triggering the sensor, whether it be the OTS tune, or perhaps something has become loose recently, since never once had I ever seen knock show up when letting go of the gas pedal. I'm just hoping, its nothing seriously detrimental happening engine-wise.
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Old 10-06-2013, 08:56 PM   #12
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Throttle lift and mashing the pedal are very common things that will trigger the sensor. Some cars are more "jinky" than others.
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Old 10-06-2013, 09:29 PM   #13
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Quote:
Originally Posted by nmlittlebigman View Post
Throttle lift and mashing the pedal are very common things that will trigger the sensor. Some cars are more "jinky" than others.
Thanks, I appreciate all the help so far.
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Old 10-07-2013, 01:15 AM   #14
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It's mostly fine knock learning tabu could have been previously learned and just reapplied. Ie . You were in a higher gear at one point, the ECU perceived a knock event, pulled timing and continues to pull timing in that range until it no longer hears any noise in that load/rpm range. To see if the knock is actually occurring log the knock sum 1,2,3,4. Then if you see the knock sum increase during fine knock learning you can tell if its real knock.
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