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Old 11-02-2007, 03:15 PM   #1
Toolz
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Default Couple questions about reading logs.

I am trying to learn and have read the stickys, but am still confused about KC, in that only neg values are bad,? so then what are the acceptable ranges for postive KC and what does it mean?

Also looking for acceptable ranges for timing, mine looks similar to other logs, but would like to know other peoples opinion.

One more thing

Is it safe to say that running osecu stage 1 with boost gauge and lots of logging would tell me if my setup is safe.? Like if I was running lean in a area, it would produce knock right? So I would see that on the IAM and KC values?

Thanks!
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Old 11-02-2007, 05:14 PM   #2
Broxma
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KC=timing advance map value * IAM/16

KC will change depending on how much advance you run. It is also based on a few feedback correction maps which will adjust timing based on knock.

Negative KC in theory would be a result of pulled timing and you could try and tune all negative KC out, but it will be difficult. Timing is sometimes pulled off throttle and when knock is detected on tip in.

In addition, some logs I have seen have shown a drop in KC with no drop in advance or IAM. KC didn't go negative but dropped from 9 to 3.5 at high RPM. I am still trying to figure out what happened there.

Look here for more info.

http://www.enginuity.org/Documentation/TuningFAQ

/Brox
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Old 11-02-2007, 06:31 PM   #3
jhargis
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Quote:
Originally Posted by Toolz View Post
Is it safe to say that running osecu stage 1 with boost gauge and lots of logging would tell me if my setup is safe.? Like if I was running lean in a area, it would produce knock right? So I would see that on the IAM and KC values?

Thanks!
You generally don't want to see a whole lot of negative KC value. It's a major indicator of knock. Broxma mentioned that it would be hard to tune negative KC out completely... You would have to have a very conservative tune. Modern ECUs tend to sort of "probe" for the best timing possible by adding as much timing as aloud before detecting knock, that way they are always running at an optimal timing advance (within the boundries of the timing maps of course).

I run a fairly conservative vf-39 tuned based on ev8siv3's vf series enginuity map and I rarely see much in the way of negative value, and when I do it's fairly low and brief... like no more than -3ish. I think the most I saw was -5 briefly around mid/high 4000's rpm range in 3rd gear as boost was climbing to 16psi after letting my car sit idling with major intercooler heat soak then a hard run, just to see a worst case scenario.

IAM is also a good indicator of how "happy" your ECU is with knock. If it's below 16, you'll probably want to either pull a little timing or richen the mixture... this is where a good wideband helps to see if you're running lean when you experience knock. Some folks seem ok with an IAM of 14-15, but I can't imagine that it's a good thing.

Disclaimer: I'm no expert on this subject, so take what I say with a grain of salt... and any gurus are free to correct me if I'm mis-informed.
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Old 11-02-2007, 08:46 PM   #4
Toolz
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Thanks for the repys, my logs on stage 1 look good, KC is always positive, 5-11, and IAM is always 16, on wot pulls 3-5th. But I was just trying to figure out what the varying positive KC values are about.
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Old 11-02-2007, 11:13 PM   #5
Broxma
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Well really, during a pull, you shouldn't see any negative KC. I almost exclusively see mine at transient times, such as shifting points or when I drop from 100% to 0% throttle. I have had KC drop during a pull, but never go negative. Any Negative KC during the pull needs to be addressed as a more serious knock issue.

One of the real issues with tuning is there is no hard fast number for how much total timing is acceptable at certain RPM's. We assume the base timing map and timing advance map are acceptable, but with increasing boost maps and leaner fuel maps, there is no hard number to go on. Never mind the fact that if you look at the base advance map it looks nothing like a tuned base map looks.

I don't have any real hard figures to give you to start with for tuning your timing. Best bet might be to smooth the base timing map and flatten the advance map then adjust up until you feel comfortable, with an eye on knock sensor signals. If you have a WB02 you'll end up with alot better results since you can set your A/F targets more in stone and only worry about timing.

/Brox
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Old 11-03-2007, 02:32 PM   #6
Tea cups
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total timing = base timing + KC + other timing compensations (ex. IAT, ETC, etc.)

KC = (timing advance map value * IAM(raw value)/16) + feedback knock correction + fine learning knock correction

So, KC is basically another compensation to base timing. It is more useful to log the three elements of KC separately by using Enginuity's logger and latest logger definitions. Logging KC alone, especially if you don't know what the advance map for the particular tune looks like, isn't as useful.

As you can see from the formula above, KC can be positive even if there is negative correction due to knock. So, just looking for negative KC isn't useful in determining knock. That is why logging the individual elements of KC gives you a lot more information. You will typically see negative KC at low loads where the advance map value is zero, meaning any negative correction will cause KC to be negative. Obviously, negative KC at moderate to high loads is a great cause for concern considering the advance map value will be a positive value, meaning that there is a lot of negative feedback and/or fine learning correction.
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Old 11-12-2007, 10:58 PM   #7
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A quick question - the feedback KC is based on percieved knock right ? I always log the knock sensors 1&2 as well as feedback KC. As I understand, any Feedback KC should be accompanied by a knock sensor flag (value of 1) for the RPMs where the knock was first exhibited.

Well I logged some today and on two ocassions I got Feedback KC but no knock signal. Is it possible that due to the sample rate it was just not recorded, or is there something else that can produce the "feedback" for the feedback KC ?
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Old 11-12-2007, 11:16 PM   #8
Tea cups
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knock signal #2 isn't used. Knock Signal #1 is the same as used by the ECU to determine correction but it is generally worthless to log due to the lack of resolution. The reason why feedback knock correction is useful to log is because there's a delay that ramps it back to zero in steps after the knock signal is clear.
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Old 11-13-2007, 09:18 AM   #9
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gotcha - thanks !
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Old 12-04-2007, 04:17 PM   #10
Wheeler Bement
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along these same lines, my logs show zero feedback knock, but littered with fine learning knock correction. Even after an ECU reset and 15 minutes of driving around my neighborhood.

How do I log the knock signal on an 02 WRX? I used to do it in enginuity(or ecuexplorer) but the latests defs don't seem to have it from what I can see.
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