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Thread: Fuel trims and different type of fuel

  1. #1

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    Fuel trims and different type of fuel

    Ok. I have noticed the followin: High and Medium fuel trims are not working? 0 all the time.

    Low fuel trim seems to works, BUT, all cars I have logged in Finland show the same value 4,6875. Today i just made my ecu use the closed loop again and i could see as the value climbed to 4,6875 when idling in closed loop. But why is that? Shouldnt we get the value around zero, and the value doesn't update afterwards, stays on the same spot. This suggests that our fuel contains so much alcolhol (should be 5% max) that the trim goes too high, and it doesnt show anything after 4,6875. The value just clips there? In evos the values can go higher?

    What do you get as fuel trim low in your uk cars and nz and au cars?
    -00 Galant Vr4 Type-V
    + Equipped with Type-S arches, genuine wind deflectors. only thing missing is the sunroof
    + Red interior with recaro front seats
    + Momo steering wheel
    + 600x300 FMIC, Custom hardpipes
    + Custom Downpipe+ Fujitsubo Legalis Super R slighlty modified/Custom catback + custom decat + Custom air intake with big K&N cone filter
    + BC Racing Coilovers
    + Advan RCII 17"x7,5 rims
    + Flexifuel /Gasoline + Ethanol E85, 850 cc injectors
    + Manual conversion with evo clutch (a standard clutch)
    + 2 x TD04-13T
    + Adam's 262 -cams
    + Xenon -projectors
    + Carbon fibre hood
    + About 450bhp/ 570Nm at the moment....with stock internals and clutch...

  2. #2

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    Please lads share me your low trims? You gotta know where they lie?

  3. #3

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    Quote Originally Posted by lateshow View Post
    Ok. I have noticed the followin: High and Medium fuel trims are not working? 0 all the time.
    Dont think our ROMs uses these... I believe the code might he there though...

  4. #4
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    Only Low fuel trims are actually used.

    What MUT references are you logging and what addresses are at those references in the MUT table?

    /edit: checked and Bill is right, only low fuel trim is used

  5. #5

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    Well what values do you have in your low trims? With standard injecetors and standard scaling. Ive multiplied my scaling by 0.95 and still the same 4,68...

  6. #6
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    Thread from dead. Did few runs after setting up tps and ifs.
    Getting fuel trim value 4.8 regardless. Air leak or that's how ecu maps are set?
    Ex: Galant VR4
    Running 268 HP ATW and 443 Nm torque at 0.9 bar
    Now: Lancer Evolution 8 FQ-300
    Running 325 HP ATW and 510 Nm torque at 1.6 bar

  7. #7

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    Like i've said here in many places, with standard scaling it goes up to 4,8 and stays there. If you reset your ecu you can see that it's 0 and you get a big positive oxygen feedback. Then drive a little and stop to idle. The trim maxxes out and you get a little smaller but still positive oxygen feedback.

    BUT

    There seems to be some reason in this. If you rescale it so that you get something else, like +- 0 trim, the car feels a lot lazier as the AFRs dip very easily below 12.

  8. #8
    Kenneth's Avatar

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    Have you tried reducing the injector latency a little rather than re-scaling the injectors?

    With the ID1000 injectors my car is running very well with the fuel trims within limits. I don't see less that 12:1 unless on full chat and then usually around 11.2:1 to 11:1

    The trick is to balance the injector latency and the scaling. When at idle, the latency is the #1 contributor to AFR values

  9. #9

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    By lowering injector scaling, duty cycle map is increased. By doing this in closed loop long term fuel trim is reduced but open loop becomes overfueled in comparison to situation befor rescaling injectors and for that reason open loop needs some adjustments.

  10. #10
    swinks's Avatar

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    Actually didn't follow this with stock injector, because few days back I swapped them for 560cc anyway.

  11. #11

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    Tried a bit to mess with the latecy but had no effect. With ethanol that isn't such a big problem since it needs more fuel all the time.

    One idea would be to mess with MAF smoothing at lower Hz.

    It just feels bit strange that these are designed as stock to be like this. In evo V and so on the trims are working. I've seen one vr4 legnum that had a live low fuel trim as standard. Weird.

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