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Old 05-17-2011, 10:40 AM   #1
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Default Idle AFR fluctuating. Cruise AFR perfect

Had some wacky weather here lately. Last week the ambient temps were up in the 80s. At idle, the MS didn't seem to compensate for fuel correctly. In temps of 60-70* and below, my idle afrs stay around 13.5. In temps above 70*, the idle afrs want to go up to 16. In both cases, my cruise speeds, afrs are rock solid, matching my aft targets with .25-5 point. I've autocrossed on the setup in the cooler temperatures and not had any idle aft issues, so I don't believe the high afrs are due to heat soak.

Shouldn't the MS compensate for higher ambient temperatures? Is there something im missing here, or do I need to create a new tune to use in the summer?
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Old 05-17-2011, 10:44 AM   #2
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the MS is what's pulling out the fuel at higher AIT temps.

fine tune your clt-based air density table to compensate. Watch the Gair log to see what the code is doing with air temp based enrichments.
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Old 05-17-2011, 10:53 AM   #3
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I read a few posts on that and wasn't sure if it was same here. I could have sworn it was disabled when I found it in the base mspnp map. I didn't bring my laptop to work today so ill have to check this evening.
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Old 05-17-2011, 10:56 AM   #4
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its the built in ideal gas law code, it will start to pull fuel when the temps get warm. i think it's too agressive, espeically combined with our sensors that get heatsoaked easily.
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Old 05-17-2011, 11:57 PM   #5
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Damn. I just read the coolant based air density correction methodology. I believe I understand how it can be applied, but I'm not entirely comfortable with it. The correction will just do the same as me adjusting the VE Table a little richer on my own, since it will be active within the same conditions.
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Old 06-06-2011, 11:05 PM   #6
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"Fixed" it by adding 2 points to the entire table outside of idle and 4 points to idle where airflow is minimal and it soaks up a bit more heat.
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Old 06-17-2011, 01:02 PM   #7
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Ok I went back to the coolant based air density and made more sense of it. My problem was understanding the "coolant" based part of the description. The name for it is misleading me to believe it functioned differently than it actually does.

I got the engine nice and hot, then plopped it into a parking spot. Adjusted the idle AFR subtly then let the heak soak in while fine tuning the Clt-based air density table.

It did the trick. No idle issues with driving around town. I'll get some good heat on it tomorrow at the autocross to confirm it's all good.
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Idle AFR fluctuating. Cruise AFR perfect-cltair.jpg  
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Old 06-22-2011, 12:13 PM   #8
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i find this whole section quite confusing reading through the help and looking at the settings.

so basically, coolant corrected air density, if i've got it showing the MAT gauge, will correct for air temp based on the figures that i input, when i'm set to air density correction = normal correction?

i think this is where i'm going wrong somewhere - my settings are 100% at the lowest temp (40 deg C), it goes to 105% at 55 deg C, and 110% at 65 deg C - but i'm seeing a gammaE of around 95% when i'm cruising and my IAT's are about 30 deg C - below is a graph i made from the datalog

Name:  Gair.jpg
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Last edited by skinny; 06-22-2011 at 12:40 PM.
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Old 06-22-2011, 12:33 PM   #9
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Ignore the table I posted above. Yes, it also took me a while to wrap my head around it. I literally went ahead and turned off all corrections and retuned my entire VE Table yesterday at 80F, 80% humidity. Ager I got home, I parked the car and tuned the coolant related air density. My table now looks more like this:

100F - 100%
110F - 100%
120F - 101%
130F - 102%
140F - 103%
150F - 104%
160F - 105%

My drive this morning to work was 60F and the afrs were a little richer (0.5) on the average. For some reason, I've observed more significant temperature correction when I tuned it at 60F and the drove it in 80F+ than tuning it at 80F+ and driving it at 60F.

My ait correction from the coolant based air density correction table starts decaying at 1300rpm and ends at 2000rpm. Idle aits from 100F to 135F were rock solid at 14.0 yesterday.
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Old 06-22-2011, 12:43 PM   #10
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pretty sure this is the table that would completely cancel out the Gair% corrections:

matcorrectionbobi.jpg?t=1293264325
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Old 06-22-2011, 12:46 PM   #11
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ok cheers cy, i'll try reducing my correction numbers and increasing the temps to closer to yours and see if it is actually just this table that's feeding the Gair correction - the VE table seems to be tuned for the Gair to run about 95% which is pretty annoying, means i have to re-do that, but it needs sorted as it's making me idle pretty lean when i'm warm which makes me think it's coming in too aggressive...

edit: brain, do you need the low temp corrections in this section - doesn't the warm-up enrichment section take care of that?
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Old 06-22-2011, 12:54 PM   #12
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Quote:
Originally Posted by Braineack View Post
pretty sure this is the table that would completely cancel out the Gair% correction
Is this for the full range of rpm or just low/idle?

Assumes tuning at 70F right?
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Old 06-22-2011, 12:58 PM   #13
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All it assumes you want to disable the built in ideal gas law AIT corrections the MS forces.

You should be able to manipulate this table in such a way that on the coldest day or hottest day of the year your tune can remain the same.
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Old 06-22-2011, 02:55 PM   #14
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This may be a dumb question, but I need to make sure im on the same page.

Is your non-linear mat correction table the same as my coolant-corrected air density table?

Hence, by rescaling my correction table to a similar range as you posted above, I am completely replacing the "normal correction" tables that we have determined to be more aggressive.
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Old 06-22-2011, 03:03 PM   #15
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yes.
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Old 06-22-2011, 03:05 PM   #16
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Perfect. It all adds up now. Definitely appreciate the help!
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Old 06-22-2011, 03:07 PM   #17
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I find the code too aggresive. So what I like to do is tune the car and then alter my own MAT table to add/subtract fuel when needed based on my motor's requirements.
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Old 06-22-2011, 04:59 PM   #18
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that makes sense - but i'm none the wiser, the actual MAT seems to bear no resemblence to where the green dot is in my map within the correction page - my MAT shows around 35 deg C, and the green dot is around 80 deg C on the map which is more like my coolant temp

anyway, i took the correction numbers right down and even when the green dot was on the 103% correction, my Gair was still at 94% (same as when i had the higher correction numbers and the green dot was on 110% correction), it makes no difference what i do on the coolant corrected air density table, Gair still does its own thing... :(
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Old 06-22-2011, 05:01 PM   #19
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Make sure in Advanced you're correcting for AIT and not CLT.

IIRC you gotta edit the .ini file to fix what the graph displays.
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Old 06-22-2011, 05:19 PM   #20
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ahh i think i see where i've gone wrong - i had the "air density correction box" set to [normal correction] which greys out the "correction based on" box which i guess forces the MS to use its inbuilt correction. so i need to change the "air density correction box" to [corrected] and then "correction based on" to [IAT Corrected]. am unsure about what the start and end correction RPMs mean though?

also, here's the bit in my .ini file, any ideas what i need to change?

[CurveEditor]
curve = clt_IATCorrC, "Coolant corrected Air Density, see Settings", 9
topicHelp = airdenHelp
columnLabel = "Temp", "Offset"
xBins = IATCTemp, coolant
yBins = IATCorS
gauge = matGauge
#if CELSIUS
xAxis = -40, 100, 15
#else
xAxis = -40, 220, 14
#endif
yAxis = 50, 150, 11
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