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Old 05-15-2012, 04:35 PM   #1
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Default Why is my afr steady sometimes and unsteady at others?

Ok so sometimes my afr's are very stable and sometimes they bounce like crazy. I dont even know the first thing to look for. Not lookin for someone to solve my problem, I just need pointed in the right direction. But if you wanna solve it I'm not gonna stop you. Attatched are pics of the graphs and the logs that the graphs came from.
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Why is my afr steady sometimes and unsteady at others?-bouncy.png   Why is my afr steady sometimes and unsteady at others?-steady.png  
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File Type: msl steady.msl (295.3 KB, 105 views)
File Type: msl bouncy.msl (133.1 KB, 81 views)
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Old 05-15-2012, 10:37 PM   #2
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different area of the fuel table it looks like to me
whats your tune and setup?
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Old 05-16-2012, 03:50 PM   #3
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I dont really think it is different parts of the map. I recently went on a 440 mile road trip. And the first half of the trip my afr's were steady. Halfway through the trip I stopped for gas. Then after I restarted the car the afr's were very unsteady like in the graphs. This was while traveling at the same speeds.

Anyways I am uploading my msq as well as my fuel table in case you just wanted to load the fuel table into megalogviewer.
edit: nevermind on me being able to load the fuel table by itself as well. apparently the settings for the forum will not allow you to upload a .table

thanks

btw this is my first tuning experience
so this tune is surely a work in progress
just wanted to let u know in case u saw a million other things that were wrong with the tune lol
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Old 05-16-2012, 04:11 PM   #4
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Almost forgot. My car is nearly bone stock as of now. MS DIYPNP, afm removed, lightweight flywheel, 1.6. I'm learning to tune BEFORE I go turbo. I'm slowly gathering parts for that.
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Old 05-16-2012, 07:39 PM   #5
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stock injectors?
The injector dead time is to high for them, fixed your ve table should be a lot flatter everywhere.
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Old 05-16-2012, 08:27 PM   #6
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IAT sensor heatsoak???
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Old 05-16-2012, 10:29 PM   #7
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injectors are stock. as far as the ve table goes, see this thread. https://www.miataturbo.net/megasquirt-18/does-look-right-you-fuel-table-65839/
autotune insists on making it go up and down starting at 2900 rpm's, and the afr's are good in that area.
I think I remember reading on mt.net a while ago about naturally aspirated miata's. and they said something about NOT getting rid of the oem crossover tube because if you did you would lose some torque around the 3k range? is that maybe why my fuel table goes up in that ares?

you said fixed your ve table? you didnt upload anything. did you mean to tell me to fix the ve table?
yeah thats still a work in progress

ill look into the dead time thing and figure that out

iat is in the stock location so i can't really see that being too much of a problem. and if it were heat soaking would it really make the afr's bounce like that?
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Old 05-16-2012, 10:58 PM   #8
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I would start with a .75ms dead time and restart tuning the cells, honestly I wouldn't use autotune, I would do it myself cell by cell, hit a cell tune in the value to lambda 1 in that cell go to next the cell

Do you have incorpate AFR target on?
I would turn it on and tune with it on, because once tuned properly, changing the AFR table changes your commanded fuel which makes tuning from that point on easier.
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Old 05-17-2012, 10:09 AM   #9
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.75ms deadtime for stock injectors is too low. Do 1.0ms--actually I wouldn't toucch it from whatever it is right now. I absolutely would use autotune but id filter out iddle areas and run it on easy mode.

Without being about to see right now id assume from what u describe is that uyour mat corrections are screwing up the tune. Take a lot at what gair looks like on the logs or all the other gammae gwarm gaiir gbaro logs look like. Also if the gve is all over the place in those areas its your fuel table.

autotune works very well and will get u a 80-90% fuel map in a 20min drive iff u hit the s
cells slowly and have good afr targets.
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Old 05-19-2012, 11:02 PM   #10
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Ok so here are graph's of both a steady and unsteady afr with all the things showing that brain suggested to look at. The one for the unsteady I took from a different log than posted above because the above log did not include shifting through all the gears so the minimums and maximums were much closer together that the steady log making it's graph look much more dramatic in comparison. I am also attatching the log that the unsteady graph came from.

It doesn't look to me brain that any of those things you suggested are the problem. Then again im no expert with these things.

Now I am gonna feel really dumb if that this is the issue. Could it be a grounding issue with my mtx-l wideband? I know you are supposed to ground it where the ecu and all the other sensors are grounded at. But I dont know where that is at. When I installed the mtx-l I took the ground wire and spliced it into the ground coming from the DIYPNP. It is only inches from the DIYPNP.
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Why is my afr steady sometimes and unsteady at others?-steady.png   Why is my afr steady sometimes and unsteady at others?-unsteadysfr.png  
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File Type: msl 2012-05-13_13.14.26.msl (754.7 KB, 46 views)
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Old 05-26-2012, 02:08 AM   #11
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Check out the open loop switch point also. Mine has been doing the same thing and I realized it was switching to open loop way too low.
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Old 05-26-2012, 12:32 PM   #12
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do you have overrun turned off? looks like youre coasting without throttle at full vacuum and still injecting fuel
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