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Old 05-30-2006, 11:24 AM   #1
engr
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Default tuning out -kc at low rpm?

I drive an 4eat and my logs are showing upto -7 KC when I accelerate hard in the range of 1k - 2k RPM just at the beginning of accelerating. What can I do to tune it out? I've got access to tuning software, but don't know what to do or how to do it.. I was going to try to increase fuel to that area and decrease timing by 3 degrees or so to see if I can get the -kc to dissapear. It runs great the rest of the power band with kc's hitting upto 12.. it's just the damn automatic is so sluggish at the low end and bogs like crazy.

anyhelp would be appreaciate.
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Old 05-30-2006, 11:29 AM   #2
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You likely cannot change fueling there since you will almost always be in closed loop in that range. You can lower timing in the base timing maps. There are probably two base timing maps. Leave the ignition advance maps alone.

Do you have logs? Can you post them?
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Old 05-30-2006, 12:02 PM   #3
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I couldn't find any file hosting.. but here's a printscreen of the log

so the only thing that I can control is timing in closeloop?

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Old 05-30-2006, 02:01 PM   #4
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Looking at that, you can tweak down a bit of timing near the 1.5-2.0 load columns from 1200-2000rpm. That's my suggestion...
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Old 06-11-2006, 08:52 PM   #5
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It looks like there is a rattle that occurs at low rpms. Heatshields? It's causing the knock sensor to pick up 'knock'.
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Old 06-12-2006, 07:45 AM   #6
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I had this problem early on too, I see you have a knock event at the area of the -ve KC, look around for something loose on the engine, or rubbing in your engine compartment.

Mine was the STi intercooler rubbing on the metal a/c line near the firewall.
Could be a loose heatshield as mentioned.
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Old 06-12-2006, 01:29 PM   #7
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FWIW, I see the same thing on my car. 0 to -2 KC at cruise. But it still runs like +40 degrees cruising. I've slightly dialed back some areas on my timing map where I was seeing the -2. I haven't logged enough yet to say if it has made a difference.

I don't think you'll ever get positive KC in those areas because the advance maps don't really kick in until higher load.
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Old 06-12-2006, 07:19 PM   #8
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These negative Knock Correction values are almost certainly the result of throttle tip-in. You can confirm this by logging while cruising at, say, 3500 RPM and then flooring it and making sure the AT doesn't down-shift. Did you record some negative Knock Correction before the throttle opening reached 100%? I'll bet you did.

There are usually separate tables for throttle tip-in fuel enrichment and spark retard. Don't mess with the general fuel enrichment and spark advance tables to "cure" this.
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Old 06-13-2006, 11:32 PM   #9
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Quote:
Originally Posted by Jon [in CT]
These negative Knock Correction values are almost certainly the result of throttle tip-in....
I concur with Jon. If you can, bump the tip-in values down at least 1 point across the board, should help with overfueling/bogging/throttle knock.

-Jason
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Old 06-14-2006, 02:49 AM   #10
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when you say bump down 1 point, you mean removing 1 degree from the entire table?

I don't think it's any loose parts.. it gets worse when I run 91 octane fuel... and I don't hear any rattle or thumps while accelerating..
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Old 07-02-2006, 10:34 PM   #11
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Follow-up?
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Old 07-07-2006, 11:54 PM   #12
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I'm working on a completly different tune using ecu edit with someone.. and there are no more -kc's. but there are other problems
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Old 07-08-2006, 02:18 AM   #13
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- KC is not a bad thing thing

The Ecu is smart to know that if it applies its full timing correction - det will occur

ifyou at low revs and go wot - the ecu will pull back timing - funnily enough ust like an old vacuum operated dissie

its part of its ability to detect / prevent and in some cases predict knock
I would leave those values alone and not try tune them out - as you will then leave yourself compromised in other areas of the map
make up a set of DET cans and listen to the engine you will learn that its not actually knocking - the ecu sees a certain load as derived from the MAF - a certain rpm a certain road speed and it knows that it needs to pull timing in order to accelarate and also prevent det - det doesnt actually occur - the ecu is being smart
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Old 10-24-2006, 12:57 AM   #14
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ill bump this as i too have teh auto with the same problem, but my tip in is almost freaky how bad it is, and its not all the time.
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Old 11-08-2006, 12:01 AM   #15
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you could bump up the knock detection range above where your problem is if you simply want it to go away

otherwise, its knocking! thats why it shows knock!
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Old 11-08-2006, 12:18 AM   #16
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yea thats great but how do you fix it without "tricks"
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Old 11-08-2006, 02:07 AM   #17
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You lower your base timing...
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Old 11-08-2006, 11:53 AM   #18
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there might also be other compensation maps in play.
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Old 11-08-2006, 07:01 PM   #19
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FWIW, I have always seen an occasional -2 KC around 2400-3200rpm at cruising load levels (0.4-0.8), even when not changing throttle position. It comes in and out and isn't consistent. I tried removing 2-3 degrees in that area from base timing. It does seem to limit this from happening, but doesn't completely stop it. I'm not sure I would worry about a -2 KC in this range while cruising or under light throttle.

I don't have a good explanation for it, but it is something I'll try to look into at some point.
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Old 11-13-2006, 01:29 PM   #20
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Quote:
Originally Posted by Freon View Post
FWIW, I have always seen an occasional -2 KC around 2400-3200rpm at cruising load levels (0.4-0.8), even when not changing throttle position. It comes in and out and isn't consistent. I tried removing 2-3 degrees in that area from base timing. It does seem to limit this from happening, but doesn't completely stop it. I'm not sure I would worry about a -2 KC in this range while cruising or under light throttle.
I'm really new to tuning and am seeing the same thing. So -1 or -2 KC isn't something to worry about? I also noticed that my IAM stayed at 16 the whole time (I have is set to start at 12). Under what circumstances is the IAM reduced if it isn't when knock is detected? My timing showed to be pulled (usually from around 40 to 37-38) but the IAM doesn't budge.
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Old 11-13-2006, 01:47 PM   #21
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I am not sure what causes the IAM to drop, I think more than a little bit of knock will make it drop. So far, the 2 automatic WRXs I've tuned/logged have low rpm, tip in -kc. The Manual did not have any -kc anywhere no matter what we did with the throttle.

I think next time though, I'll take a log of knock sensor voltage and see if there are spikes at all. Or if the ECU is just pulling timing because of something the TCU is telling it.
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Old 11-13-2006, 05:41 PM   #22
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that would be great if you could do this
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Old 11-13-2006, 06:14 PM   #23
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^^^ Was that directed at me?
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Old 11-13-2006, 06:24 PM   #24
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Quote:
Originally Posted by Master2192 View Post
^^^ Was that directed at me?
If it wasnt I would direct the same question toward you....It would be great if you could read the volts to see if its actually detecting or if its the ECU....

I dont have an auto, nor do I know anyone that does but I still just as curious to learn what exactly is happening for future reference....
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Old 11-13-2006, 06:29 PM   #25
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Alright, I'll try to get a log of the knock sensor tonight. Will be doing a 40 mile drive at cruising so I can get in some low rpm tip-in as well as some shifts to see what is happening.
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