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Thread: Fuel economy decreasing and LTFT increasing overtime after e-tune

  1. Default Fuel economy decreasing and LTFT increasing overtime after e-tune



    You guys might be able to help me, i haven't been able to find anything related on the forums so far.


    I've done about 1500kms now on my tune by PD, but i started to notice the LTFT increasing ( Negative - pulling fuel ) at light throttle. At first i thought this was the ecu learning, but it progressed from -3, and slowly got worse, reaching as high as -7.5. However reading on the forums, it stats its normal to be within the range of 10, which i think makes sense, however my fuel economy has also, with the change in ltft, decreased dramatically. My first tank of gas on the tune, i reached 550kms, 50kms more than on the standard tune, however the next tank i got 450, and now my last tank i got 400 km. All of this along with LTFT, i have no idea what to think. The onboard trip computer, while i know isnt accurate, even noticed it going from an average of 8.4l/km ( It really was closer to 9.8-10l/km) up to 9.8l/km. I thought maybe it was my driving, but the last tank i drove it like a nana, and it didn't get any better.


    I really don't understand, i would of thought overtime it would get better, but it hasn't.


    What i have done though, was reflash the final map revision. And while i have only done 20km on it, the fuel trims seem to be more reasonable. First starting off, it was reaching +6ish, but started to drop off, and the trip computer, while only a short distance was reading back in the 8's.


    If anyone has any insight, or knowledge on this i would greatly appreciate it, because i'm truly completely lost.


    Kind regards


    Connor

    2012 gen 2 - 66000kms - CS TIP + Intake, Autotech HPFP, NGK one step colder

  2. Default

    The weather can sometimes affect the fuel delivery. (air density)

  3. #3

    Default

    Really need more info to know. LTFT accommodates changes in air density (temp and altitude) as well as fuel variability (and probably other things too). It's expected that it will change in winter compared to summer. You quoted some + and - numbers after resetting. Are these at the same maf voltage? Can you get a log of MAF v., air flow, LTFT and STFT after letting it settle for a 100km or so? Do you have one from summer to compare it to? That will give you a better idea.
    You can always check for boost leaks as well.

    What fuel are you using? Has it changed? Don't think 'tank' is a good measure for fuel economy - too variable. Try using an app like fuley or calculate it yourself from distance and fuel added at station.

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  4. Default

    Cheers Lachlan for your reply,

    Yeah i'm going to put this down weather i think, specifically temperature change. When i started to notice the change was when it was getting colder. Did the tune in the summer months, and started to drop in winter. Since reflashing the map a few thousand km's ago everything has been sweet as, easily getting 500km to 50l, sometimes a little less. Average temperatures probably dropped around 10 degrees Celsius.

    i will get a maf log to compare, just to see what it looks like now vs when i did the tune.

    Boost leaks = none that i could find through boost leak testing ( pressurising the system ).

    Sorry 'tank' isnt a good measure sorry, to me a tank is always 50l give or take a few L when i fill up. Always used the same fuel, 95. Nothing changed there unless there is discrepancies between stations.

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