Fuel leans out when outside temps drop. - Miata Turbo Forum - Boost cars, acquire cats.

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Old 09-28-2008, 12:56 PM   #1
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Default Fuel leans out when outside temps drop.

I thought high temp leaned cars out. When the temps drop into the 70's my car starts running lean, and all over the place?????
I would adjust it. But when the temps are back to 90's in the afternoons it runs great??????
I'm still new to this MS, what do I need to adjust and the retard version please.
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Old 09-28-2008, 01:07 PM   #2
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I'm interested too. Mine does the same thing, but on a smaller scale.

FWIW, hot air has less mass oxygen per unit volume. So if fuel stayed constant, cold air= more oxygen, hot air = less oxygen.

I'm sure MS is somehow supposed to adjust for IAT, right? I wonder if this is adjustable. I know warm up enrichment is. I guess the IATcorrecting for VE tables is a fixed table that's not adjustable?
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Old 09-29-2008, 11:11 AM   #3
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Matt and Stephanie, do you have any idea's?
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Old 09-29-2008, 11:13 AM   #4
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Are you running the appropriate firmware? Meaning fw with the correct easy therm values? Meaning if no AFM are you running the correct values for GM IAT? and vice versa
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Old 09-29-2008, 11:16 AM   #5
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I bet it has to do with your AIT corrections table.... Check under coolant based air-density corrections...I only correct above 90*F AIT, I bet you have them on almost all temps.
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Old 09-29-2008, 11:31 AM   #6
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but unless he made some changes to the RPM range in which it's active it would only apply to idle. Or am I not remembering the default settings correctly? Or is he not talking about driving even, just idling?
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Old 09-29-2008, 01:22 PM   #7
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Quote:
Originally Posted by paul View Post
Are you running the appropriate firmware? Meaning fw with the correct easy therm values? Meaning if no AFM are you running the correct values for GM IAT? and vice versa
That's what I am guessing too - if it has the wrong firmware loaded, your corrections will be off.
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Old 09-29-2008, 02:14 PM   #8
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I should have the correct firmware. And I'm running 9093 without AFM. I have not changed anything besides O2 sensor to wideband, and VE values.
I quess I need to check the air density correction values. I have never messed with them.

The car starts out idling lean to rich. And when I start to drive, the afr's are back and forth.
After warm up, Idle is rich but works, cruise is high, like a full point higher. Like 15-16 and bumping 17 sometimes.
But as soon as the outside temps hit the 90's, cruise is back to perfect. Never over 14.3- 14.7 everyonce in awhile bumps 15. for a blink of the eye.

Thanks,
Any ideas are appreciated.
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Old 09-30-2008, 11:57 AM   #9
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Try reloading the firmware, just in case you have the wrong one.
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Old 10-01-2008, 08:21 PM   #10
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Reloading your firmware does amazing things. My overboost control started magically working with a reflash on mine.
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Old 10-02-2008, 12:15 AM   #11
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Quote:
Originally Posted by Savington View Post
Reloading your firmware does amazing things. My overboost control started magically working with a reflash on mine.
I reflashed and it is working better. I am going to have to read up on the corrections.

The thing that gets me is,
my tabs gray out, and when I open new tabs and close them out, the dual ve and spark like to stay gray for no reason.

I wounder if the overboost is what is shutting my car off at 9psi. Or is that only for ebc?
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Old 10-02-2008, 09:23 AM   #12
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Many of these things stay gray if not enabled - for example, normally an MSPNP isn't set up for dual table code. Could you post your MSQ?
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Old 10-02-2008, 10:57 AM   #13
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Quote:
Originally Posted by Toddcod View Post
I thought high temp leaned cars out. When the temps drop into the 70's my car starts running lean, and all over the place?????
I would adjust it. But when the temps are back to 90's in the afternoons it runs great??????
I'm still new to this MS, what do I need to adjust and the retard version please.
science: cooler air is more dense. more dense means more o2 per volume. more o2 for the same fuel means the o2 sensor will say theres a lot of o2 leftover after the cylinder event and read "lean".
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Old 10-02-2008, 11:30 AM   #14
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Quote:
Originally Posted by Matt Cramer View Post
Many of these things stay gray if not enabled - for example, normally an MSPNP isn't set up for dual table code. Could you post your MSQ?
I'll try to post it tonight when I get off work. Thanks
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Old 10-02-2008, 12:46 PM   #15
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Ok. Also list exactly what's grayed out. Sometimes MegaTune fails to check and makes a table available that you will not actually be using.
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