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Old 11-09-2014, 10:21 PM   #1
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Default Indicated AFRs misbehaving

So, recently my AFRs have started behaving very sporadically, with no changes to my tune whatsoever. Before, WOT would get me mostly under 13:1, sometimes upwards around 13.2. N/A. Now, it's solid 15s/16s. It goes rich between gears and on decel (though this is probably just a lack of overrun)

Initially, since this all just suddenly started happening, I thought maybe my pre-cat (CA-spec car) had become clogged. I still think this may be a possibility, but I now have to helicoil a hole in my head due to the bolt bringing 2/3 of the threads with it, and I stopped swapping them there. I'll reapproach this idea when I have time.

Tune and Log attached. Ignore the AFR target table. It has been modified, but the VE table hasn't. Haven't run VEAL or enabled EGO since.

Suggestions?
Wideband issue?
Car is actually running at those AFRs?
Attached Files
File Type: msl weird AFR.msl (742.7 KB, 48 views)
File Type: msq Schuyler 11-9-2014 CurrentTune.msq (228.2 KB, 37 views)
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Old 11-09-2014, 10:34 PM   #2
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Did you calibrate your wideband recently?

Any old logs? Has your pulsewidth dropped at the lean conditions?
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Old 11-09-2014, 10:35 PM   #3
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Disclaimer: I've never dealt with a clogged cat first-hand.

Quote:
Originally Posted by Schuyler View Post
Initially, since this all just suddenly started happening, I thought maybe my pre-cat (CA-spec car) had become clogged.
What makes you think this?

Having no actual experience in the matter, I would think that a plugged catalytic converter would manifest itself in the form of richer AFRs, not leaner. By restricting the exhaust flow, you're going to get less intake air for the same MAP. Less air with same amount of fuel = richer AFR.
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Old 11-09-2014, 10:45 PM   #4
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Quote:
Originally Posted by Joe Perez View Post
Disclaimer: I've never dealt with a clogged cat first-hand.
What makes you think this?

Having no actual experience in the matter, I would think that a plugged catalytic converter would manifest itself in the form of richer AFRs, not leaner. By restricting the exhaust flow, you're going to get less intake air for the same MAP. Less air with same amount of fuel = richer AFR.
Honestly, my initial thoughts were the same. All I knew was that I've been told clogged cats before a wideband make them behave "unexpectedly," and that the pre-cats are very fragile. I guess you could saw I was clutching at straws at this point. My only thought currently is the clogged cat would be effectively filtering more, as the air is forced to make its way through narrower openings.
(EDIT: just adding for anyone not familiar with the cal-spec setup. This cat is part of the header, so the wideband is POST cat (well, after the first cat, before the second))

Quote:
Originally Posted by deezums View Post
Did you calibrate your wideband recently?

Any old logs? Has your pulsewidth dropped at the lean conditions?
Most recent logs I had aside from those are attached. And sorry, meant to specify in the initial post, AEM EUGO. Which aside from the calibration between MS and the gauge (which is 1:1 atm), there is no calibration button etc. like on the LC1.

EDIT: the other was too big to upload here. https://www.dropbox.com/s/gtorfrt4ub...42.09.msl?dl=0
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File Type: msl 2014-09-29_15.21.05 home from school.msl (685.8 KB, 42 views)
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Old 11-09-2014, 10:52 PM   #5
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Similar conditions, but a lot less PW and a lot leaner mix. Are you sure nothing changed?
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Old 11-09-2014, 11:04 PM   #6
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Quote:
Originally Posted by deezums View Post

Similar conditions, but a lot less PW and a lot leaner mix. Are you sure nothing changed?
Current tune to 9-28-14 19:16:
AFR Targets, SD card logging disabled, Sensor checking disabled (CEL).

Don't see anything that has changed since then that should effect VE.
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Old 11-09-2014, 11:35 PM   #7
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Quote:
Originally Posted by Schuyler View Post
(EDIT: just adding for anyone not familiar with the cal-spec setup. This cat is part of the header, so the wideband is POST cat (well, after the first cat, before the second))
Ah- I missed that part, assumed you were running the wideband before the cat.

Is this even a valid configuration? Running a wideband after the pre-cat? I mean, the factory NB02 sensor is before the first cat, I can't imagine how the readings wouldn't be distorted by placing a wideband after it.

[/voice of absolutely no experience whatsoever]
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Old 11-09-2014, 11:41 PM   #8
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Quote:
Originally Posted by Joe Perez View Post
Ah- I missed that part, assumed you were running the wideband before the cat.

Is this even a valid configuration? Running a wideband after the pre-cat? I mean, the factory NB02 sensor is before the first cat, I can't imagine how the readings wouldn't be distorted by placing a wideband after it.

[/voice of absolutely no experience whatsoever]
Oh I completely agree they will be distorted to some degree, but I decided to go ahead and install the ms and get familiar with it before boost, as in theory the readings should always read leaner than reality, resulting in a richer (read:safe) tune. Plugs have never been overly rich, so I've never really worried about it, until now when things just seem completely out of the ball park. The fact I've ran a potentially rich tune for ~6mo now was also more rational for a clogged cat.


(Picture taken recently (in the past week))
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Old 11-10-2014, 09:38 AM   #9
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Isn't 13:1 crazy dangerous to begin with?

*Edit never-mind I mis-read your sig and thought you were FI
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Old 11-11-2014, 03:21 PM   #10
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I suppose nothing obvious like exhaust leak around the pre-cat joints or head is likely? Can you smoke the system? Sometimes they're small enough not to be that audible but still cause weird AFRs.
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