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Old 12-29-2012, 11:28 PM   #1
Smile83
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Member#: 316365
Join Date: Apr 2012
Chapter/Region: TXIC
Location: Houston
Vehicle:
2011 STI

Default Knock Sum Reading

I read a few threads here on knock readings and cant find a solution. My problem is cylinder 4 is picking up knock sum and also pulling between -1 to -4.9 timing. My tuner suggested it could be a cracked ringland or an external noise. We cant seem to locate the external noise. Could it be a cracked ringland causing the knock reading? Can it be tuned out?

Side note: Not smoking and good compression across the board. New spark plugs. Also datalogged with no knock event in 3rd gear WOT.

Vehicle Specs:
DW65c FP
Tomei Type-S FPR
ID1000cc
Stock MAF/Intake
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Last edited by Smile83; 12-30-2012 at 10:17 AM.
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Old 12-31-2012, 11:00 AM   #2
fritzski
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Join Date: Apr 2012
Chapter/Region: RMIC
Location: colorado
Vehicle:
10 sti
wrb

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i tend to always pick up some knock sum. more so on #4 mostly in part due to the location of the knock sensor being closest to #4, i havent had timing pulled though. i do watch feedback knock to see when and where timing is getting pulled, and its my understanding that there are some times when its more prone to happen, starting off from a dead stop, shifting gears, and rapid throttle changes, along with boost onset. from what i've seen most would agree thar -1.4 isnt a big concern and i believe cobb says up to -2.6 is acceptable. i do know the one time you dont want to see this happen is under load with higher boost, as this can spell disaster for the motor. before jumping to the ringlands there may be some other possible causes for knock. i start with the easiest and work down the line from there. intake tract leak (vaccum leak) check all hoses are in place and in good shape, check that the maf is clean, check the front o2 sensor, or if you want to rule out ringlands you can do a leakdown test, to save time and energy you may want to start with #4 since that cylinder is #1 suspect in these cars. hope this might help. kinda suprised your tuner isnt sorting this all out, that is what he gets paid for
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Old 12-31-2012, 07:57 PM   #3
hutch959
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logs?
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Old 01-02-2013, 09:59 AM   #4
Cobb Tuning
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Location: Austin, DFW, Portland, SOCAL
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Quote:
Originally Posted by Smile83 View Post
I read a few threads here on knock readings and cant find a solution. My problem is cylinder 4 is picking up knock sum and also pulling between -1 to -4.9 timing. My tuner suggested it could be a cracked ringland or an external noise. We cant seem to locate the external noise. Could it be a cracked ringland causing the knock reading? Can it be tuned out?

Side note: Not smoking and good compression across the board. New spark plugs. Also datalogged with no knock event in 3rd gear WOT.

Vehicle Specs:
DW65c FP
Tomei Type-S FPR
ID1000cc
Stock MAF/Intake
Knock sum values are irrelevant in and of themselves and cylinder #4 will usually be higher due to knock sensor orientation. The reason why knock values have no meaning is that they are also incremented at idle and low loads when the Subaru knock detection is extremely poor at distinguishing knock from other engine noises. The only use it has is to look at when it increments when false knock is less likely (at higher load). It useful to monitor this as it can be tricky to see when learned events for fine knock learning have actually occurred as they are learned and then re-applied over and over until they ramp back to zero.

You said timing was being pulled? If it is not shown in feedback knock correction or fine knock learning columns (or DAM has not dropped), then it is not due to knock. A current knock event from the above would be shown as a increment to knock sum in one (or more) of the cylinders.

Bill
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Old 01-02-2013, 01:14 PM   #5
Smile83
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Member#: 316365
Join Date: Apr 2012
Chapter/Region: TXIC
Location: Houston
Vehicle:
2011 STI

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datalog (4th gear WOT)

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Old 01-03-2013, 10:06 AM   #6
Cobb Tuning
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Location: Austin, DFW, Portland, SOCAL
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Quote:
Originally Posted by Smile83 View Post
datalog (4th gear WOT)

This log shows two knock events (one in cylinder 2 and one in cylinder 4) during the run. Busted ringland tends to show more extreme corrections (even at lower load) and sometimes a drop in the DAM as well, which is not happening here. You need to determine if knock events you are seeing are the result of a mechanical issue and if not, if it is something that is the result of the tune. I'm not sure what you've done so far, but the first step would be to verify fueling during the WOT run via aftermarket wideband o2 sensor. If that checks out, then you should attempt to see if reducing timing advance in that area makes any difference. You can also test with some unleaded race gas mixed with a full tank of your normal gas to see if the knock stays the same or improves. These are methods that will help you determine if this is false knock or not. Some shops may also use det cans to do this. Not sure what you've tried so far.

Bill
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Old 01-09-2013, 10:54 AM   #7
bmx045
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Location: Wakefield, MA
Vehicle:
2011 MCS

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I betchya those exhaust valves are hating you right now too. 10.5* total timing
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