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Intakes, Fuel Trims, and AFR

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Old Aug 2, 2009, 01:42 PM
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Originally Posted by tokeone
since maf scaling is available, does that mean that this could be remedied easier without all the fuel trim changes?
I copied and pasted the code that Tephra gave in my 015 xml file and then started ECUflash and looked for the table, but there was no MAF table. Strange.
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Old Aug 2, 2009, 01:53 PM
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Slightly off topic, but for everyone who's not an expert in the area: I was studying up on how fuel trims work earlier this week and found a page that had lots of very good info that might help some of those following this thread. enjoy
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Old Aug 2, 2009, 04:42 PM
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Originally Posted by nj1266
It does not...It just carries over from closed loop cruise into WOT operation. So even though the LTFT cruise is not adding/subtracting fuel at WOT, it adds/aubtracts the fuel it has calculated in closed loop to WOT. So if LTFT cruise is X, then the AFR becomes, target AFR+X. X stays the same in WOT operation as it was during closed loop cruise. It is simply added to the target AFR.
Yes but how?

the 3 fuel trims (Low, Medium and High - forget STFT for a sec) are MAF-Hz bins, so Low MAF-Hz, Med MAF-Hz and High MAF-Hz... High MAF Hz means open loop - which also means you probably not going to run stoich, you might run ~11:1 AFR... which means the 02 sensors will be useless and thus cant give you a reading on how far lean or rich you are from stoich...
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Old Aug 2, 2009, 04:44 PM
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oh you need the XML to go in evo10base.xml:

Code:
    <table name="MAF Scaling Part 1" category="Fuel" type="2D" level="2" scaling="uint16">
        <table name="Volts" type="Y Axis" elements="44" scaling="VoltsADC1023"/>
    </table>

    <table name="MAF Scaling Part 2" category="Fuel" type="2D" level="2" scaling="uint16">
        <table name="Volts" type="Y Axis" elements="44" scaling="VoltsADC1023"/>
    </table>

    <table name="MAF Scaling Part 3" category="Fuel" type="2D" level="2" scaling="uint16">
        <table name="Volts" type="Y Axis" elements="42" scaling="VoltsADC1023"/>
    </table>
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Old Aug 2, 2009, 05:04 PM
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Originally Posted by tephra
oh you need the XML to go in evo10base.xml:

Code:
    <table name="MAF Scaling Part 1" category="Fuel" type="2D" level="2" scaling="uint16">
        <table name="Volts" type="Y Axis" elements="44" scaling="VoltsADC1023"/>
    </table>
 
    <table name="MAF Scaling Part 2" category="Fuel" type="2D" level="2" scaling="uint16">
        <table name="Volts" type="Y Axis" elements="44" scaling="VoltsADC1023"/>
    </table>
 
    <table name="MAF Scaling Part 3" category="Fuel" type="2D" level="2" scaling="uint16">
        <table name="Volts" type="Y Axis" elements="42" scaling="VoltsADC1023"/>
    </table>
Thanks, but the voltage columnhas ... in it. How do I fix that?
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Old Aug 2, 2009, 05:53 PM
  #36  
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Scaling:

Code:
    <scaling name="VoltsADC1023" units="Volts" toexpr="x*5/1023" frexpr="x*1023/5" format="%.2f" min="0" max="16" inc="0.05" storagetype="uint16" endian="big"/>
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Old Aug 2, 2009, 07:32 PM
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I've been logging my fuel trims on the stock intake with 800cc injectors and my trims are -12.xx at idle and -11.xx during cruise. Would this explain why on my Hi-oct fuel map I can adjust my tables to about 12.5-12.7 in the correct load cells but only register low 11 afr's on the wideband?
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Old Aug 2, 2009, 07:35 PM
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When installing new injectors you SHOULD ALWAYS setup the scaling+latencies so that your trims are as close to 0% as possible.

Once your injectors are tuned properly you can then begin tuning your fuelmap...
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Old Aug 2, 2009, 07:39 PM
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^Roger that, lol... I'm adjusting the injector scaling as we speak.
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Old Aug 3, 2009, 12:28 AM
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The volt units in table 1 do not look right. There is no decimal like in the other two. Are they supposed to look like this?
Attached Thumbnails Intakes, Fuel Trims, and AFR-maf_tables.gif  
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Old Aug 3, 2009, 12:30 AM
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double check your XML - copy and paste it back here if you want...
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Old Aug 3, 2009, 04:42 AM
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Hmm... I had slightly different addresses for MAF Scaling from Gunzo. I wonder if that is why I'd been having so much trouble with trying to compensate for an intake. Maybe I'll try these ones and see if it improves anything.

Here's what I had (For 52680015):

Code:
<table name="MAF Compensation" address="5753a">
		<table name="X" address="615ea"/>
	</table>

<table name="MAF Compensation #2" address="5758a">
		<table name="X" address="6163a"/>
	</table>

<table name="MAF Compensation #3" address="575da">
		<table name="X" address="6168a"/>
	</table>
The first one is the same, but the others differ.
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Old Aug 3, 2009, 05:11 AM
  #43  
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Just check your evo10base.xml and make sure the axis counts match (ie 42/44 or whatever)
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Old Aug 3, 2009, 08:06 AM
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Originally Posted by tephra
Just check your evo10base.xml and make sure the axis counts match (ie 42/44 or whatever)
They don't, actually. Mine are "40, 40, 50" where yours are "44, 44, 42"

Though I lined up the data from the tables I used with the single table from one of the Cobb AP maps, and the axis matched up. I was comparing what Cobb used for MAF Scaling on an AEM Intake with stock since I don't have my stock intake to do the scaling myself.
Code:
	<scaling name="MAFVoltScaling" units="units" toexpr="x*5/1024" frexpr="x*1024/5" format="%.3f" min="0" max="5" inc="1" storagetype="uint16" endian="big"/>

	<table name="MAF Compensation" category="Fuel" type="2D" scaling="AirFlow16">
		<table name="X" type="X Axis" elements="40" scaling="MAFVoltScaling"/>
	</table>

	<table name="MAF Compensation #2" category="Fuel" type="2D" level="1" scaling="AirFlow16">
		<table name="X" type="X Axis" elements="40" scaling="MAFVoltScaling"/>
	</table>

	<table name="MAF Compensation #3" category="Fuel" type="2D" level="1" scaling="AirFlow16">
		<table name="X" type="X Axis" elements="50" scaling="MAFVoltScaling"/>
	</table>
I'll check my actual ECUFlash stuff when I have the right computer.

This could be why I was getting crazy boost/load curves when I tried MAF Scaling! If only the first table was correct, it would reach the second table and think there was a drop in airflow. That might explain why I was getting a "double peaking" load curve. Sweet.
Last edited by xPRimNT; Aug 3, 2009 at 09:06 AM.
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Old Aug 3, 2009, 11:37 AM
  #45  
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Aggressive mivec lean AFR by 1-1.5 afr at hight load. So changing mivec on low load will affect on Fuel Trims? So we should recalibrate low load AFR before tuning hight load AFR?

I'm running stock intake (except Upper IC pipe) with pretty aggressive mivec . My FuelTrim_Cruise is -4.5% and FuelTrim_Idle
jumping between -4 and -3.2.
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