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Old 11-16-2011, 10:57 AM   #1
Tryptofan
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Default Fine Knock steadily growing: -3.5+ - only when cruising?

I'm a bit concerned about my car - I've been logging with the standard log list, after watching Cobb's video about what to log and how to interpret it. I am custom tuned (tune is almost 2 years old) - at WOT, everything works absolutely great. I rarely if ever have a knock event under high load (the last few 3rd gear test pulls I've done show no knock to speak of, and virtual dyno reads within 10 whp of my tune).

However, at low-ish loads (1.0-1.75) and when cruising (literally, cruise control is on), I am getting occasional events where I will repeatedly see FKLC pull as much as 4.5 degrees of timing. Generally, this will happen 3-4 times in rapid succession, and the events will happen only once every 1-2 hours of freeway driving. Since I do a lot of freeway driving, I'm worried about why this would be happening. DAM is never less than 1 (never has been in the life of this car as far as I can tell), and I'm not noticing any large changes in A/F learning 1 (nothing greater than -3%); A/F learning A,B,C,D are 3.5,-0.6,-0.2,0. I'm not sure what constitutes "a lot" of knock, but generally I'm looking at about 100 knock events per hour on cylinder 4 below 55F. In warmer temperatures (65+F), knock is much less frequent for some reason (about 50-60 on #4 per hour). The other issue may be the AFR at cruise, which lies between 15.5 and 17.5 at 3000 rpm. This logging was all conducted after a leak test, so I know there are no leaks in the intake system.

The only modification I have made to the car since the tune is a new, large top mount intercooler (which I am going to be tuned for in the next few weeks). At worst, I was told by the installer this would make the car run richer. I am being gentle on the car and not doing any pulls other than the tests I did to make sure I'm not knocking if I need to pass or merge with traffic. If this is the cause, I would be relieved.
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Old 11-16-2011, 11:47 AM   #2
DoWork
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I'm interested to see some answers regarding this. We have had the same issues with our car. Cold weather seems to make it worse, as you said. I have tried using the AP to dump 5* of timing, mixing in a bit of race gas, etc, and nothing really helps. I posted on the Cobb forums a while back:

http://www.cobbforums.com/forums/sho...ock-Correction....

regardless of what Cobb says, it still freaks me out lol.
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Old 11-16-2011, 12:31 PM   #3
snoopy_sti
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I get that frequently, its always when cruise control is on at very light throttle. It shows up as fine knock learning while I watch the AP. The numbers start to decrement. Bu the end of the day if I plug into ATR the Fine Knock learning table is still showing "0". Under WOT I have no fine knock. I think the knock sensor just sucks.
2011 STI
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Old 11-16-2011, 12:49 PM   #4
DoWork
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Quote:
Originally Posted by snoopy8818 View Post
I think the knock sensor just sucks.
I read some huge thread about this on the LGT forums that pretty much said the same thing lol
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Old 11-16-2011, 01:36 PM   #5
Tryptofan
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Haha, damn DoWork - we have almost the exact same posts about this problem. It's downright unnerving. Good to know I'm not the only one with these problems though, and that cobb seems to think they're not bad for the car. I did just replace the heat shield, so I'm going to check and see if that could maybe be it - I never would have imagined that could cause a false knock. I've noticed that there's a jingling from time to time under the hood when I downshift in particular, so maybe that's it (if anyone knows it: driver's side, not near the turbo, sounds like loose change jingling but very consistent in tone, 5-10 hz, speed of the sound changes with engine speed). Only audible after you let off the gas at high RPM (3500+) when downshifting.

And now I realize, we also have almost the exact same list of parts...do you have a 2.5? If so, we're the same even down to displacement... Here's yours:
-VF43
-GMS 3 port
-GMS UP with 44mm Tial EWG
-HKS DP/Cobb Catback
-Snorkus delete(paper filter)
-Walboro pump
-samco inlet
-huge TMIC
-1 step colder plugs
-Protuned/APv2

Here's mine! Similarities bolded
- 3-port HOA boost controller (very similar to GM)
- Intake (K&N cone filter, 90* elbow, bigger MAF - P&L HiFlo)
- TGV deletes
- Samco inlet
-Spearco (huge) TMIC
- P&L TurboXS DP
- P&L 44 mm EWG kit (TiAl)
- Walbro 255 LPH
- 1-step colder plugs
- Protune by Jorge at P&L(if this is who protuned you, then question answered. I see you're in wisconsin, so I think it could be a possibility.)
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Old 11-16-2011, 02:23 PM   #6
DoWork
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Yes, my car is 2.5L. Unfortunately, I live the land of cow ****, corn, bars, and lifted trucks, so I had to resort to e-tuning for my map.

I'll send you a PM. I dont want this to turn into a bash fest because of me.
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Old 11-16-2011, 04:37 PM   #7
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did you monitor knocks when you make turns?
my 2011 STI, i see some knocks when i make left turns.....not on right turns.. strange...
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Old 11-16-2011, 05:22 PM   #8
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I'm having a similar issue. I get large amounts of "feedback knock" while cruising in the 2000-2500 rpm band and the engine sees a slight load increase from driving up a hill. The shop that built my motor says that it is harmless and is more than likely a harmonic pitch that the car is hitting at the certain rpm range with that load... It is annoying when I log my car and I am hitting -4 to -9 FKC though... I also see knock when I rev the motor sharply in neutral...

Very annoying... And I'm still looking for a way to correct it...

Subscribed.
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Old 11-16-2011, 05:29 PM   #9
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Also to add. I swapped in a brand new knock sensor and no change.
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Old 11-16-2011, 05:49 PM   #10
DoWork
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Quote:
Originally Posted by bzbuzz View Post
did you monitor knocks when you make turns?
my 2011 STI, i see some knocks when i make left turns.....not on right turns.. strange...
No, never noticed anything like that. Honestly, it souds like you may have some sort of false knock....maybe noise from the front diff or something. I know when my trans shat the bed, my car pulled like 20* lol, but it was LOUD. Do you hear any rattles?

Quote:
Originally Posted by SubieWReX View Post
I'm having a similar issue. I get large amounts of "feedback knock" while cruising in the 2000-2500 rpm band and the engine sees a slight load increase from driving up a hill. The shop that built my motor says that it is harmless and is more than likely a harmonic pitch that the car is hitting at the certain rpm range with that load... It is annoying when I log my car and I am hitting -4 to -9 FKC though... I also see knock when I rev the motor sharply in neutral...
^That is my issue to a "T"
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Old 11-16-2011, 07:14 PM   #11
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If anyone would be inclined, please post how many knock events/hour on #4 you get in these conditions (cruising ~2500-3000 rpm, or wherever your problem region is; preferably the colder air condition where there are more events). I just want a general idea of what is "normal," since I'm not sure if I'm seeing a normal or uncommon or concerning amount of "knock events" per hour.

Ideally, I'll be able to afford a real, high quality knock sensor and start logging #4 off that in the next few months. Then I can get some idea of how much knock I'm actually getting, rather than the not-so-trustworthy data I get from the ****ty corner-cutting OEM sensor.
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Old 11-16-2011, 08:36 PM   #12
ArSoN9
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these problems arent to uncommon in low load, low rpm instances. Im having a similar issue with my car and pulling timing across the map hasnt yielded much.

Its common to have flase knock on motors with nosiey valve train, such as full race builds where the heads have been put back on without proper tolerances. but ther two cars ive tuned that have this issue havent had any head work.

one thing to do to solve this issue with false knock and excess fine knock learning is to increase the rpms where the knock sensor is enabling to look for knock to something around 3k. the names of these tables are feedback correction range and fine knock correction range on romraider and these are on Accesstuner software from cobb also
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Old 11-17-2011, 10:32 AM   #13
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Lot of different discussions going on this thread, but keep in mind that the knock detection set up on these cars is a compromise between effectiveness and low cost. At low RPM/loads, it is very poor at determining combustion knock from other noises. The occasional negative feedback or fine knock learning correction at low loads (around 1 g/rev or less) is not a concern. If you see multiple counts at low loads (say about -4 deg. or worse) consistently, then you may have something rattling in the engine bay (such as a loose turbo heatshield or uppipe heatshield with broken welds) that the knock sensor is picking up (i.e. false knock). A built motor changes the noise characteristics of the motor (relative to the stock block) and you will see increased false knock. We do have tables in the AccessTUNER which will allow you to experiment with adjusting the knock sensitivity for these cases.

Where knock is a concern is when you see consistent knock correction under heavy load, such as wide open throttle, that is not due to mashing the throttle or lifting off the throttle abruptly. Or where you see the DAM drop that is not due to resetting it to its initial value (due to reflash a map, resetting ECU, or disconnecting car's battery). Remember, that the higher the load, the higher the cylinder pressures and the more damaging a potential knock event will be. So, even if you were actually knocking occasionally at low load, cylinder pressures are low and generally it isn't a problem (and the ECU reacts accordingly by pulling timing). It is all relative and as long as you keep in mind that the knock detection is not perfect and consider when the reported knock is occurring, you'll be able to make a reasonable determination of whether it is a problem or not.

The knock sum value itself is meaningless and cannot be compared across cars. That is becaues it is incrementing at low loads (including idle) when the ECU sucks at knock determination (which is why the ECU does not respond to those events). Those ECUs that have per cylinder knock sum monitors will pretty much always see a higher value in cylinder #4 - that is normal and due to how the knock sensor is placed on the engine block.

Bill
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Old 11-17-2011, 12:23 PM   #14
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Thanks for all of the comments! This is really helpful stuff!

I will keep you posted on how tuning comes along.

-Mark
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Old 11-17-2011, 05:11 PM   #15
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Quote:
Originally Posted by Tryptofan View Post
I've noticed that there's a jingling from time to time under the hood when I downshift in particular, so maybe that's it (if anyone knows it: driver's side, not near the turbo, sounds like loose change jingling but very consistent in tone, 5-10 Khz,
err.. fixored!
If you can hear noises at 5-10 hz, you have superhuman hearing! Plus, it wouldn't sound like a jingle, but rather the deepest rumble you've ever heard (if it were possible to actually hear it). Humans can feel 5-10 hz, but cannot hear it.
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