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Poor fuel economy

Discussion in 'Gen 1 Prius Plug-in 2012-2015' started by Jerry Liebler, Jan 7, 2017.

  1. bisco

    bisco cookie crumbler

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    should have known, when you said ev miles were fine. how odd to have a dirty maf at 33k. goes along with the brakes i guess.
     
  2. Mendel Leisk

    Mendel Leisk Senior Member

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    Makes me wonder if I should do that: MAF cleaning. And not so good if it can go south like that, and not show a code or anything.
     
  3. Jerry Liebler

    Jerry Liebler Member

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    As I said early in this thread, the air filter was extremely dirty, solid black with some form of soot, like it had spent it's life following a smoky diesel. It appears that Toyota uses MAF data to set most of the engine operating conditions, things like valve timing (effective compression ratio), spark advance, even EGR and of course fuel injection flow rate. However the fuel flow is "trimmed" to the desired ratio by looking at the exaust through the wideband oxygen sensor, AKA fuel air ratio sensor. Spark timing is, no doubt also modified by the knock sensor and EGR may well be "trimmed" to keep the knock sensor quiet. This all means that an honest MAF is vital for efficiency. An operating but dishonest MAF (dirty) probably doesn't increase exaust emissions and is not all that easy to diagnose with on-board sensors so no codes. Interestingly I now know that the "volumetric efficiency" readout from Torque did clearly show that there was a problem.
     
  4. Mendel Leisk

    Mendel Leisk Senior Member

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    My brain is full, but it sounds like you're on top of it. (y)
     
    #44 Mendel Leisk, Feb 13, 2017
    Last edited: Feb 13, 2017
    Raytheeagle likes this.
  5. Jerry Liebler

    Jerry Liebler Member

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    I do believe the problem has been solved! I just filled up, the first time after cleaning the MAF, It took 8.5 gallons to go 461 HV miles and went 91 EV miles on 19kw. So HV miles were at 54.24MPG, EV miles @ 161.4MPGE with 16.5% EV & 83.5% HV. So using my scoring method the weighted average is 116% of the EPA benchmark, certainly not my best tank but about in the middle of results I recorded on the spread sheet for the 2012
     
  6. Yea Right

    Yea Right Active Member

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    Good news .... and very interesting.

    Thanks for sharing
     
  7. jerrymildred

    jerrymildred Senior Member

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    Looks pretty good. Glad you got it sorted.
     
  8. Mendel Leisk

    Mendel Leisk Senior Member

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    Yeah, that's excellent. Our more-or-less lifetime mpg is 49 mpg (US). Our BEST tanks are 54 mpg, a rarity.

    upload_2017-2-23_8-48-36.png


    To convert liter/100 km to mpg (US), or vice versa: divide 235.2 by either value to convert, ie: 235.2/4.9=49