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Attention Prius Owners, I believe I have discovered a previously unknown Mechanism of Low MPG.

Discussion in 'Gen 2 Prius Main Forum' started by TheLastMojojomo, Nov 2, 2021.

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  1. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    Trivia: to convert km/100km to mpg (US gallons), or vice versa, divide either into 235.2. I forget how I arrived at that, but it's just a distillation of the conversion process.
     
    #121 Mendel Leisk, Jul 15, 2024
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  2. Troy1994

    Troy1994 New Member

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    That’s handy, thanks!
     
    #122 Troy1994, Jul 17, 2024
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  3. Frankusa94

    Frankusa94 Junior Member

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    Your post made me realize my 07 Prius no longer chirps when doors are locked…and I am also experiencing 40mpg in city and 50+mpg on drives above 40 mph. I did disconnect my 12v a few months… and ICE immediately kicks on with the very little pedal press. Must be an easy way to restore max ev … has anyone spoke to Toyota about this?
     
    #123 Frankusa94, Aug 24, 2024
  4. Frankusa94

    Frankusa94 Junior Member

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    You may have not proved it all out yet… but you are onto something that is really happening in my 07 Prius… since 12v battery disconnect a few moths ago. My city mpg is around 38 and above 40 mph… mpg is in low 50s… complete opposite of advertised performance. Gas pedal above 10-15% … kicks ice on… even with a nearly full charge battery…
    Love to hear the finds of this theory….
    Frank
     
    #124 Frankusa94, Aug 24, 2024
  5. di0tima

    di0tima New Member

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    I am also experiencing this behavior on my prius v — over 50mpg on highway and sub 40 in the city! Would really appreciate a way to reset the low ev mode to high ev!
     
    #125 di0tima, Aug 25, 2024
  6. dolj

    dolj Senior Member

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    I personally believe the (Gen 2) car configures itself in response to the way it is driven.

    If you drive it like a race car, it will configure itself for a sport mode (less economy).

    If you drive it using typical eco-driving techniques (especially pulse-and-glide), it will configure itself for economy driving.

    This is just my observation, take it for what it is worth.
     
    #126 dolj, Aug 25, 2024
  7. Frankusa94

    Frankusa94 Junior Member

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    I Believe Prius v has a ev mode button you could use to force maximum ev operation…
     
    #127 Frankusa94, Aug 25, 2024
  8. dolj

    dolj Senior Member

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    That's not how the EV button works. Hybrids are not EVs, they are combustion cars. Using the EV button this way is just robbing Peter to pay Paul.
     
    #128 dolj, Aug 26, 2024
  9. MAX2

    MAX2 Member

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    I'll put in a few cents.
    You have several topics and messages about problems with the fuel system and engine operation of your car. What does the EV mode have to do with it?
    You need to understand the engine operation first.
     
    #129 MAX2, Aug 26, 2024
  10. MAX2

    MAX2 Member

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    I agree with your theses.
    With an aggressive driving style, fuel consumption for the same distance is higher than with smooth pressing of the gas and brake.
     
    #130 MAX2, Aug 26, 2024
  11. Frankusa94

    Frankusa94 Junior Member

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    it doesn’t… I’m trying to solve my highway speed stalling issue on 07 Prius

    I also noticed a drop in city mpg since battery post cleaning … 1000 lies ago… “possible stuck in weak ev mode”
     
    #131 Frankusa94, Aug 26, 2024
    Last edited: Aug 26, 2024
  12. Frankusa94

    Frankusa94 Junior Member

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    #132 Frankusa94, Aug 26, 2024
  13. Frankusa94

    Frankusa94 Junior Member

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    as little as 15- 20 percent pedal/throttle causes engine to kick on… even with all green bars on battery indicator…. This started when I cleaned battery posts 1000 miles ago… seems like Prius stuck in weak ev mode… I think I am also experiencing that phenomenon…. This is a lesser problem compared to highway stalling issue.

    Still searching for answers….

    ✌️
     
    #133 Frankusa94, Aug 26, 2024
    Last edited: Aug 26, 2024
  14. MAX2

    MAX2 Member

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    It's hard to look for a black cat in a black room where there isn't one.
     
    #134 MAX2, Aug 26, 2024
  15. TheLastMojojomo

    TheLastMojojomo Active Member

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    I will hopefully have my final video out by the end of this year. I have most of the content I need to make the actual video... I've just delayed making it because I'm distracted by other matters.

    Yes this is a very real phenomenon. There is too much evidence in my own experience and other people's posts where they describe the exact same MAX and WEAK EV State Behavior between 2 Prius or Toyota Hybrids that can't be explained by anything else..

    My guess is there's a process somewhat similar to Ignition Mapping that occurs for the Hybrid Battery. Ignition mapping is where the engine software tests different Ignition points to learn knock values (engine compression causes causes fuel mixture to preignite).

    During prolonged highway driving where the Hybrid Battery can be maintained at roughly 60%... software in the HV ECU does an analysis of the Hybrid Battery based on capacity, resistance, Battery temperature and other factors using methods like columb counting.

    Here is my original post describing increased EV Output after multiple commutes in a row (3rd highlight paragraph):

    [​IMG]

    Here is a Gen 3 owner that experienced the same thing (3rd highlighted paragraph)

    [​IMG]

    Both of us drove our vehicles on stop & go drive styles for hours a day due to our jobs. Me in action below:



    I'm driving in the exact same spot in the exact same way multiple days in a row on the mail route. You become very sensitized to how the Hybrid System behaves at different States of Charges and the behavior of the Hybrid System delivering mail like this... which is why I'm the 1st person to connect the dots to all of these other posts and really done the leg work to filter out any other possible causes like stages of Hybrid Operation, Hybrid Battery Temp, etc.

    Now compare two other posts from a 2020 Rav4 Hybrid and 2005 Gen 2 Prius.

    [​IMG]

    [​IMG]

    They both describe the same phenomenon of one Hybrid putting out more EV Power than the other despite driving both in the exact same condition.

    That's because one Prius/RAV4 has met the necessary condition to verify it's Hybrid System health via software measurements and allow aggressive usage of EV Output during city driving, and the other has not. Toyota has likely programmed some version of this software into all of their Hybrids... and thisactually led to a lawsuit against them in the 2015 timeframe...

    [​IMG]

    [​IMG]

    [​IMG]

    The cause of the Low EV Output in this lawsuit was misattributed to a software update... where really the software update just activated the latent WEAK EV State Software due to resetting the HV ECU.

    The plaintiffs were right that they were experiencing a loss of EV Power and mpg in city traffic because of the update... but it was an indirect result rather than direct which led to the lawsuit going knowhere as they were looking in the wrong place in the software for the issue. When they brought it to Toyota's attention, the cause was misplaced and Toyota was 100% correct in that the low EV Output/MPG was not caused by the Software Update.
     
    #135 TheLastMojojomo, Aug 28, 2024
  16. MAX2

    MAX2 Member

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    When the 12V battery is disconnected, several ECUs are disconnected.
    The engine ECU resets fuel trim settings and other things.
    This is more important than resetting the high-voltage battery ECU (internal resistance of module pairs from 22-23 milliOhm to 19 milliOhm and the SOC value.
     
    #136 MAX2, Aug 28, 2024
  17. di0tima

    di0tima New Member

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    I went in for a recall and my ride home had some improved gas mileage. Time will tell, but maybe this could point to a method of resetting?
     

    Attached Files:

    #137 di0tima, Oct 17, 2024
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