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Thread: Commanded AFR in closed loop = 13.8? Is this normal?

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    Commanded AFR in closed loop = 13.8? Is this normal?

    Using the Torque Pro app I see that my commanded AFR during ALL closed loop operation is steady at 13.8:1 and my measured AFR is very close to that. My fuel trims are both fine, I am close to sea level with 70 degree ambient temps using 87 octane California fuel (E15?).

    I thought target AFR in closed loop should be just about 14.7, or is the fact that we have ethanol in our fuel affecting things?



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    http://www.ultra-gauge.com/customer_...php?article=29

    Just a little poking around online.
    Have not dug in to see if this is accurate.

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    Mitsubishi Technician live4redline's Avatar
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    13.8 to 14.7 is normal. You will more likely see a slightly low number at start up and should rise up closer to 14.7 at normal operating temperature.

    It is an 11:1 compression motor, so I would think it would dip rich toward 13.7 a little often to keep the cylinders cool so I would expect it too be normal.
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    Once warm enough to go into closed cloop the commanded afr is pegged at 13.8 and never wavers. In open loop, yes, it changes quite a bit, but closed loop at all temps, loads, and rpm the ecu is commanding 13.8 which is close to stoich based on the ethanol in our fuel.

    Currious if anyone else sees this behavior?

    Should commanded afr fluctuate in closed loop operation with load/temp/rpm etc or is closed loop simply pegged to stoich?

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    Quote Originally Posted by live4redline View Post
    13.8 to 14.7 is normal. You will more likely see a slightly low number at start up and should rise up closer to 14.7 at normal operating temperature.

    It is an 11:1 compression motor, so I would think it would dip rich toward 13.7 a little often to keep the cylinders cool so I would expect it too be normal.
    Fyi- our compression in America is 10.5:1. In Europe it's 11:1

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    The more ethanol(oxygen) in the fuel, the lower the AFR. E85 is like 9.8:1 vs pure gas 14.7:1, everything else falls in between.

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    Mitsubishi Technician live4redline's Avatar
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    Your reading the 13.8 off a factory O2 sensor? Might need to check if the sensor being read is a narrow or wide range sensor also. It may be a narrow band and the reading is being rounded to number for display purposes. I don't know of any Mitsubishi's that have wide band sensors from the factory but I also haven't looked into the Mirages sensor. Also to note, Mitsubishi tuning doesn't work on a 1:1 AFR setting either. This mostly applies too the closed loop tuning but for example the fuel map may say 12afr at 4000rpm and 75load and the actual AFR on a wideband sensor will read 14.5afr. It's confusing to understand at first but that's just how Mitsubishi does it. I'm not familiar with the tool your using but you may be seeing what the ECU map is trying to do instead of the actual reading and if that's the case... Trying to do 13.8afr could easily translate to an actual 14.5afr.
    Last edited by live4redline; 10-17-2016 at 04:19 PM.
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    I have successfully pulled the factory tune Rom from my US-Spec 2017 Mirage SE but I am still working on defining the maps. I really hope to be able to post all the factory maps here eventually.
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    Cars don't care what the AFR is, they are really is just trying to maintain stoich. It uses LTFT even in open loop to adjust for fuel variations. Put in some E30 (30% ethanol) or 2 gallons of E85 with 7 of E10/15 and your AFR will drop even lower.
    Last edited by roosterk0031; 10-17-2016 at 06:18 PM.

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    ^ For the most part in open loop, Ya. But I have seen some readers display the "Target AFR" from the fuel map (by target afr I mean the current fuel map setting or digit). Just curious what his tool is trying to show. A reading from the narrow band sensor, or some sort of PID information from the ECU. After thought tells me that the narrow band would have to display in voltage so I'm leaning toward the other if he physically has any sort of AFR type display, cause that's the only place you could find it.


    Last edited by live4redline; 10-17-2016 at 06:27 PM.
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