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Old 06-02-2009, 05:07 PM   #1
kh15
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Default fbkc, knock sum, knock correction advance, help

so i normally log only fbkc along with flkc but today i decided to log fbkc, flkc, knock sum, and knock correction advance.

my logs show a value of 0 through out the whole run in the fbkc and flkc tables but knock sum is at 15 the whole time and knock correction advanace goes from 0 to 8.

what is knock sum and knock correction advance?

my logs show 0 in fbkc and flkc so that means my car was not knocking correct?
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Old 06-02-2009, 08:10 PM   #2
Tea cups
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knock sum increments for every single isolated knock event of the first knock event of a series of consecutive knock events. Knock event means as perceived by the ECU. knock sum has no restrictions, so it will increment even when the ECU deems that no response to knock event should occur, such as at low RPM when the knock sensor is useless (lot of false knock). When the ECU decides to respond to a knock event, there will be a decrease in FBKC, decrease in FLKC (current cell), OR decrease in the IAM (only one of these at any given time). If knock sum is 15 the entire log, then there's was no knock event in the log. Knock sum will reset to zero when it reaches 35.

Knock correction advance is the advance added to base timing after being corrected by FBKC, FLKC and the IAM. So, you need to know what the advance map looks like. Still, I wouldn't bother logging it. Log knock sum with understanding that it will be quite active at idle and low rpm and that is generally false knock. The number itself doesn't mean anything, only WHEN it increments.
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Old 06-02-2009, 10:05 PM   #3
kh15
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Originally Posted by Tea cups View Post
knock sum increments for every single isolated knock event of the first knock event of a series of consecutive knock events. Knock event means as perceived by the ECU. knock sum has no restrictions, so it will increment even when the ECU deems that no response to knock event should occur, such as at low RPM when the knock sensor is useless (lot of false knock). When the ECU decides to respond to a knock event, there will be a decrease in FBKC, decrease in FLKC (current cell), OR decrease in the IAM (only one of these at any given time). If knock sum is 15 the entire log, then there's was no knock event in the log. Knock sum will reset to zero when it reaches 35.

Knock correction advance is the advance added to base timing after being corrected by FBKC, FLKC and the IAM. So, you need to know what the advance map looks like. Still, I wouldn't bother logging it. Log knock sum with understanding that it will be quite active at idle and low rpm and that is generally false knock. The number itself doesn't mean anything, only WHEN it increments.
thank you! that sort of cleared things up for me. Forgive me though as im still trying to understand the in's and out's of subaru ecu's
here is the log....figured this might make things a little easier!

so in the log FBKC & FLKC remain at zero because the knock sensor was never "set" (knock detected) correct?

why is my knock correction advance adding base timing if the fbkc and flkc tables are at 0?

knock sum is basically a totaly count of everytime the knock senor picks up knock, no matter what the load or rpm range?
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Old 06-02-2009, 11:11 PM   #4
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so in the log FBKC & FLKC remain at zero because the knock sensor was never "set" (knock detected) correct?
Yes, although, remember that FLKC can be a correction due to a past knock event. You would have to know which FLKC cell you were in and whether the value changed at that moment. Most people will do a Learning View before and after a run and compare. Also, be aware that a decrease in the IAM is another possible response. And, of course, no response is a possibility.

Quote:
why is my knock correction advance adding base timing if the fbkc and flkc tables are at 0?
knock correction advance is basically a high octane map -> KCA = (advance max map * IAM) + FBKC + FLKC. So, if FBKC and FLKC are zero and the IAM = 1.0, then you'll be running the max advance (added to your base timing).

Quote:
knock sum is basically a totaly count of everytime the knock senor picks up knock, no matter what the load or rpm range?
Yes, even where the knock sensor is useless. So, the number itself is irrelevant. Your count of 15 could have occured at idle, let's say. It is only relevant when it increments and then at what load/rpm that occured.
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Old 06-03-2009, 12:19 AM   #5
kh15
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Originally Posted by Tea cups View Post
Yes, although, remember that FLKC can be a correction due to a past knock event. You would have to know which FLKC cell you were in and whether the value changed at that moment. Most people will do a Learning View before and after a run and compare. Also, be aware that a decrease in the IAM is another possible response. And, of course, no response is a possibility.


knock correction advance is basically a high octane map -> KCA = (advance max map * IAM) + FBKC + FLKC. So, if FBKC and FLKC are zero and the IAM = 1.0, then you'll be running the max advance (added to your base timing).


Yes, even where the knock sensor is useless. So, the number itself is irrelevant. Your count of 15 could have occured at idle, let's say. It is only relevant when it increments and then at what load/rpm that occured.
great! thanks so much for taking the time to explain that to me!
what do you suggest logging for the future then, just FBKC and KLKC?
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Old 06-03-2009, 07:29 AM   #6
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I suggest you log the knock sum and NOT FBKC/FLKC. Use Learning View before and after the run.
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Old 06-03-2009, 06:32 PM   #7
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ok and if the knock sum value changes DURING the WOT portion of the log i should be concerned right?
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Old 06-05-2009, 12:56 PM   #8
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It's normal to see a lot of non-interesting knock sum increments below about 2500 rpm and 1.0 g/rev, but stuff at higher load and RPM (3500+, more or less) is worth paying attention to. Some of that is random too but if you get repeatable increments then it's worth doing something about it. There's a big grey area between easy-to-ignore and must-fix, so I mostly look for repeatability.
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