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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.

  1. Paladain55

    Paladain55 Active Member

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    For my gen 3 i noticed the set point the car prefers for the battery is 58.8 SOC. It targets that for the interstate so i figure that is the cars preferred set point. Also, I noticed if you go above ~62% SOC the car will burn off a lot more of that charge over 62% cruising and accelerating compared to normal where say at 58.8% it will accelerate and cruise and stick to that point. I think the burn off gets more aggressive as you get close to 80% as it doesn't want you up there because of a combination of battery longevity and available space to absorb braking events into the battery. I can't argue with it but it seems like thats what the engineers have programmed. I mostly just use the battery on mine to shut the engine off and scoot up at stop lights.
    Also, the gen 3 has the EHRS so it will only give an engine shut off at 103Fwt, and then one or two more before 150F and it makes you wait a certain amount of time between them. Once you hit 150F the EHRS is warmed up and then the car will allow you to shut the engine on and off at will, 45mph and below of course.
    For the most part these cars don't produce enough waste heat and they suffer bad gas mileage in the winter especially on short trips because of that (what kills the gas mileage is the being cold forces the car to idle on you to warm up which is just wasting fuel outside of the fact that the air is thicker and the car is less efficient when the engine block is cold as it will typically run richer until its warm and can vaporize fuel better). So I will typically not use the heat until I hit 150F, and use it sparingly (one to two bars, heat on high, set to feet) as if you do auto heat it will cool the car off and you will have an extremely hard time maintaining 150F to get good gas mileage like a hybrid should only around town though. It produces enough heat on steady state driving.
    So I can see per trip mileage on my scan gauge and on a 60 degree day I can get 55-60mpg no problem on a trip, and have a 35 degree day later in the same week on the same tank of gas and get 45-50mpg. Outside of the air being 10% thicker on the cooler day leading to lower gas mileage since the car needs warmth. So I typically block the lower grill year round and the car does fine, and i block the upper grill below 60F. Inverter temps will typically be 40F above ambient with the block in up top, and car does great maintaining engine coolant temps with the lower block so you can use a lot more heat as well! Like a normal person in something like a v6 camry where the engine stays on all the time and has plenty of heat to spare.
    I would comment more on the lower SOC states but my car has the memory effect on the battery since i typically stay above 52-55% soc. If i cycled the pack more down low i would probably know more.
     
  2. Melthias

    Melthias Member

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    I wonder if the OP has any more progress on this in the past several months.
     
  3. Benjamin Close

    Benjamin Close New Member

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    This thread is interesting I have 2020 Corolla Hybrid and a 2021 Corolla hybrid, both NiMH batteries and all the symptoms in this thread fit. For me I noticed the drop directly after a service of the 2020 Corolla hybrid. I specificially asked them to check the 12v battery. However after pick up it seems to drag more and have less power. Before the service I could easly get 3.7l/100, after struggle to get under 4.0l/100. A long drive country drive did seem to reset it but only periodically. Having 2 hybrids of the same type the difference is very noticable. The 2021 corolla just seems to have way more power in ev mode. The 2020 corolla when I bought it was exactly the same but only after a long drive seems the same. Might be a completely different issue but symptoms seem the same.
     
  4. TheLastMojojomo

    TheLastMojojomo Active Member

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    It is not that your 2020 Corolla Hybrid that was serviced now Drags and has Less Power... What has happened is that the Corolla Computers have changed what Pedal Angle activates the engine... where before EV Mode would have been used instead for the same HV Battery State of Charge.

    Your 2020 Hybrid Corolla is still delivering the same amount of power as before the 12v disconnect... But it is now substituting Engine Power for what was previously provided only by EV Mode via the HV Battery prior to the 12v service.

    Basically, parameters in your Hybrid Corolla ECU's have been reset that tell EV Mode to be used aggressively at City Speeds (0-50KPHish). It now runs the engine in place of EV Mode for power.

    You are describing the WEAK EV State nearly word for word.

    The reason you get better L/100Kms while country driving because above a certain speed, the engine needs to run all the time to protect the transmission. At this point differences in drivetrain behavior cease between the MAX and WEAK EV State and L/100Kms will be the exact same as the drive trains deliver power in the exact same way. L/100Kms for city speeds are only what's effected... not highway speed L/100Kms.

    To get the
    MAX EV STATE to reactivate permenantly... you will likely need to do multiple drive cycles in a row of highway commuting under ideal conditions for the Hybrid Battery... as the hidden drive cycle parameter that regulates the EV States is needs specific information from the Hybrid Battery to decide that your 2020 Hybrid Corrola can safely activate the MAX EV STATE and use EV Mode aggressively again at city speeds.

    Also, an update for anyone interested:
    I'm still working on proving this issue definitively. Hopefully by Summer's end I will be able to show everyone exactly what I'm trying to explain in this post if I'm able to gather the data I need. I just need to get my Prius to engage the MAX EV State so I can record it's data.

    The WEAK EV State Data is recorded in this YouTube video for anybody interested.
     
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  5. Mongoose2

    Mongoose2 Junior Member

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    I believe I'm afflicted by what you're describing. My pedal angle seems to max out at only 20% or so before the engine kicks on. I'll be staying tuned for your findings.
     
  6. thetuningspoon

    thetuningspoon Junior Member

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    I've had my Gen 2 for over 10 years and it has never gotten above 40 mpg according to the computer. These days it's more like 37mpg. It doesn't really ever run on full EV unless you're barely moving... I'm talking 5-10mph. I wonder if this is my issue. I always thought it was weird when people talked about the Prius getting higher mileage in city driving vs. highway, since my experience has always been the reverse.
     
  7. bisco

    bisco cookie crumbler

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    after you get up to 30mph or so and back off the pedal so the mpg meter goes to full, and you not maintain speed or slow deceleration by feathering the pedal?
     
  8. Weedle

    Weedle New Member

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    Thanks for keeping this up Mojo! Rather interesting. Ill have to try and see what my car is like. The city mpg has always struck me as awful.
     
  9. Paladain55

    Paladain55 Active Member

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    I always avoid full EV mode so I can use the battery power to shut the engine off for long engine off coasting or to keep scooting up at red lights without the engine on.
    The tuning spoon, if you drive around with that big asse roof rack on thats part of your issue. A bare two pole roof rack system is about a 10% loss in FE. Thats why I don't hardly ever use my Yakima rack anymore.
    Also, avoid full EV mode. It more or less hurts you on FE on an old battery. If I find the car is running 30mph cruise control and goes into full ev mode, I will either throw it into neutral or hit the gas to where I stay above the bar and keep the engine on. IF we had a plug in EV with a larger battery i would be more about full EV mode, but we only generate E by hitting the brakes so I don't want to waste in a spot where i could just be using the engine. I barely get enough to keep the engine off at stoplights when im using the AC lol
     
  10. SoonerPrinowDasher

    SoonerPrinowDasher New Member

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    Sounded crazy.

    I think the physicians and Mel Johnson Controls tech programmed the AC to be off at acceleration and on at deceleration. It like boost an extra 5 mpg for me.

    Then sometime later, something happened; another waterpump issue and a few grands fix.
     
  11. TheLastMojojomo

    TheLastMojojomo Active Member

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    Update: I am still hard at work trying to expose this low mpg mechanism... but am failing on my own. In the end, I will need help from the Prius Community to prove it.
    Since my last post, I have bought a 2nd 2008 Gen 2 Prius with 127,000 miles and installed a brand new OEM Toyota Hybrid Battery in it and have attempted to get the MAX EV STATE to trigger by doing lots of highway commuting.

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    I have failed to get this 2nd Gen 2 Prius to trigger the MAX EV STATE despite having a brand new Hybrid Battery. I have hard pivoted to making a 2nd comprehensive post about this issue as well as a video to describe it.
    I wanted to be able to show exactly what I'm talking about... but I can't get the MAX EV State to trigger on either of my Gen 2 Priuses. To show what I'm talking about I will have to test a MAX EV STATE Prius first.

    Once I complete the video, I will have a clearly devised way that anybody can test for the MAX and WEAK EV State with relative ease as long as they have an Android Smartphone/Tablet. The second comprehensive post I make will be much more clear, concise, and well thought out. The only way I'll be able to prove the MAX and WEAK EV States for certain is by getting the data from a MAX EV State Prius/Toyota Hybrid, which will likely have to come from the Toyota Community at this point.

    For now here are links to Imgur Posts with highlighted text of every Priuschat Post I could find describing this low mpg mechanism:

    High Accuracy Priuschat Posts that describe the WEAK EV State:
    Moderate Accuracy Priuschat Posts that describe the WEAK EV State:
    Gen 2 Prius:

    Gen 3 Prius:
    LA Times Article about a 3rd Gen Prius Owner experiencing the WEAK EV State:

     
    #71 TheLastMojojomo, Jul 1, 2023
    Last edited: Jul 1, 2023
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  12. TheLastMojojomo

    TheLastMojojomo Active Member

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    Also for the video I am making about this... I've made a meme from The Matrix scene where Neo becomes the one. It is going to go in the final video somewhere but not sure where exactly yet. This is the rough draft and subject to change:

     
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  13. bisco

    bisco cookie crumbler

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    LOL, well done! :p
     
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  14. TheLastMojojomo

    TheLastMojojomo Active Member

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    Just a quick update, I am still working on my final post and have made a few graphics to better explain the EV States:

    [​IMG]

    [​IMG]

    [​IMG]

    My Final post will hopefully be done soon. I am waiting to receive the correct electrical connectors to install the EV Mode button in my American Gen 2 Prius to see if that increases EV Mode Output similar to the MAX EV State when the button is pushed.

    All Images Below measure the WEAK EV State Only:

    Below is the behavior of the WEAK EV State when the HV Battery is charged above 75%

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    Below is the behavior of the WEAK EV State when the HV Battery is charged to 74% but not above:

    [​IMG]

    [​IMG]








     
    #74 TheLastMojojomo, Aug 8, 2023
    Last edited: Aug 8, 2023
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  15. TheLastMojojomo

    TheLastMojojomo Active Member

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    A Small update:
    I have since installed the EV Mode button mod in my American Gen 2 Prius and it has allowed my Prius to use EV Mode aggressively like the MAX EV State and finally has given me a coherent way to show exactly what the MAX and WEAK EV States are.

    Below is with the EV Mode Button pressed simulating a "Pseudo MAX EV State":
    [​IMG]

    Below is the WEAK EV State:
    [​IMG]

    You can see in the WEAK EV State the Combustion Engine turns on and completely takes over power output while EV Output is virtually non-exist.

    The MAX EV State essentially makes the Prius behave like the EV Mode button is pressed in all the time when under the right condition... SOC, Battery Temp, Speed, etc. There are still nuances and such but I will have the well fleshed out in my final post.

    I will be posting a tutorial on the EV Mode Button Install and likely some preliminary videos regarding the EV Mode Button and comparing it to the WEAK State while I'm working on my final post.

    I have also made a quick tutorial on how to download chart files and test your Gen 2/Gen 3 Prius with charted data exactly as I have done above in the screenshots using the Android app Torque, and an Add-on app called Realtime Charts for Torque:



    This YouTube Tutorial was addressed at PriusChat user @Darklandscape as he has shown great interest in the EV States and has been privately messaging me about the WEAK EV State for over a year now... but the tutorial will work for anyone.

     
    #75 TheLastMojojomo, Aug 16, 2023
    Last edited: Aug 17, 2023
  16. dolj

    dolj Senior Member

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    I have been sitting on my hands while biting my tongue and biding my time to allow you to present your case.

    Now that you say that the difference between what you are calling WEAK EV State and MAX EV State is pressing the EV button to achieve a pseudo-MAX EV State, I am more convinced than ever that what you have observed is the difference between stage 3a/3b and stage 4 of the engine warm-up cycle.

    In order to advance to stage 4 from stage 3a/3b you need to come to under 5 km/h (3 MPH) and allow the hybrid system to do the little calibration that will take ~7-10 seconds (and this calibration is Gen 2 specific) – although it seems like a lot longer – to advance it to stage 4.

    In my experience, it takes 20 to 30 minutes of driving before the system is warmed up enough to advance to stage 4. One other quirk I have noticed over the many years is that sometimes the car is ready to advance (that is it is at stage 3b) but doesn't when you get under 5 km/h or a complete stop as the engine switches off while decelerating. In this case, once stopped, if you would like to 'force' it to do the calibration, you can hold the car on the brake pedal and gently press the "go" pedal until the engine starts. The engine should stay on and complete the calibration to move to stage 4 – again taking 7-10 seconds to do this.

    To any interested, you can read all about the 5 stages of warm-up and the characteristics of each stage by clicking on the "Hybrid Warm-up: 5 modes of Prius Operation." link in my sig.
     
    #76 dolj, Aug 16, 2023
    Last edited: Aug 16, 2023
  17. TheLastMojojomo

    TheLastMojojomo Active Member

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    No it has nothing to do with the stage 3a/3b to stage 4 of engine warm-up. It is the EV Output allowed that changes when comparing a WEAK EV State Prius to a MAX EV State Prius.

    At 60% SOC... a WEAK EV State Prius will only use 13hp EV Output before kicking the engine on despite being in stage 4 of Hybrid Operation.

    At 60% SOC... a MAX EV State Prius will use 28+hp EV Output before the Combustion Engine kicks while also being in stage 4 of Hybrid Operation.

    Below is the graphic attempting to explain this:
    [​IMG]
    In the YouTube videos I've posted above.. my Prius is in stage 4 of Hybrid Operation... you can tell this because the engine immediately kicks off as soon as my foot leaves the gas pedal. This is the tell tale indicator for a successful transistion from stage 3a/3b to stage 4... which requires a Calibration shutdown at a full stop once the ICE Coolant reaches its optimal temp.

    After the stage 4 Calibration shutdown... the ICE will shut off immediately as your foot leaves the gas pedal... as you can see in the 1st 30 seconds of the YouTube video below. You can also hear my radiator fans running to cool the engine proving it's at least at 200°F:



    So for example... what you see at timestamp marker 22:58 in the video... which is a recording of the
    WEAK EV State... EV hp Output is only allowed to be 19hp at 70% SOC.... before the Combustion Engine turns on.

    In this exact same scenario for the
    MAX EV State... EV hp Output would have been allowed to be 28hp+ at 70% SOC... before the Combustion Engine turns on.

    So if you watch from 22:25-23:00 in the YouTube Video I created above and I were in the MAX EV State instead... the yellow line(Instant EV hp Output) would travel at least to the orange line(28hp - Max Ev Hp Output allowed according to the WOUT parameter in the Hybrid Control ECU) before kicking on.

    And both of them would have been in stage 4 of Hybrid Operation. This extra EV Output also applies backwards to the other stages... like stage 2 where the Prius coolant is not optimal temp yet... but the ICE can still shut off if standing still long enough. The initial burst of acceleration even in stage 2 will provide more EV Output in a MAX EV State Prius compared to the WEAK EV State.

    What pressing the EV Mode button does is... it shows how much more EV hp Pwr the Prius is capable of producing and is a "Pseudo representation" of the the MAX EV State with some stipulations. It allows a similar level of EV Output and makes my Prius use the same level of EV pwr that it used to when it was in the MAX EV State.

    If you'd like to review the high accuracy posts that describe this WEAK EV State phenomenon to a T by the few Prius owners who were trying to wrap their head around this problem.. those are below:

    Hybrid System Less Efficient After 12V Disconnect/Battery Change? ECU's? (My original post)

    Beware of Dealer ECU Calibration MPG way down

    2007 "poor" gas mileage

    Significant reduction in MPG between 2004 and 2005 Prius'
    Gen 3 Prius:
    Possible undiscovered performance and MPG issues with Prius v (lowercase v)(This post solidified that the WEAK EV State was real and potentially widespread)

    Lost 10mpg after EGR clean, etc. Now losing mind!

    Does the car remap or recalibrate the HV battery?

     
    #77 TheLastMojojomo, Aug 17, 2023
    Last edited: Aug 17, 2023
  18. dolj

    dolj Senior Member

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    Happy to be wrong about S3a/3b and S4.
    That looks like the Hobbit post but just reformatted to look nicer. So, not better information, it is just formatted to look nicer.
    In these two comparisons are these two different Prii that produce the WEAK EV State vs MAX EV State? If they are the same car how is it that you can induce one versus the other?
     
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  19. TheLastMojojomo

    TheLastMojojomo Active Member

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    It can be two different Prii or the same Prius in the MAX or WEAK EV State.

    [​IMG]

    The MAX and WEAK EV States are "Phantom Software States" in the Hybrid Control ECU that dictate EV Output. Since they're software... any Gen 2 or Gen 3 Prius can be effected by them. (And possibly Gen 4/5 but I have no strong evidence for that yet).

    Most people who notice the WEAK EV State have driven two different Prius side by side... one in the MAX EV State and the other in the WEAK EV State. They notice significantly less City Mpg and the engine revving more... or what they describe as "loss of power".

    You can also notice it if you have a very analytical mind analyzing your own Prius behavior or if you drive your Prius hyper specifically like me. (106 mile mail route, 400 mailboxes, stopping at the same place and driving in the same way and speed every day. Used to get 45mpg on mail routes now get 35 due to the WEAK EV State and have lost $3,000+ in gas over the past 7 years.)

    The "WEAK EV Software State" is triggered by a 12v disconnect... which defaults the Prius to the WEAK EV State automatically as a result of the Prius ECU's losing their memory... Likely as some sort of protection mechanism for the Hybrid System but im not really sure.

    And the "MAX EV Software State" appears to engage after multiple drive cycles in a row of highway commuting... which was my experience in the past... But sometimes this seems to never happen and the Prius becomes permanently stuck in the WEAK EV State... like my Prius has been for 3+ years after a 12v disconnect.

    The multiple drive cycles in a row of highway commuting likely allow some sort of Calibration or Hybrid System self check to be undergone... and when that self check/Calibration recieves a pass condition... the Prius permanently persists in the MAX Ev State until another 12v disconnect. The behavior is similar to passing emissions monitors and may actually be directly related to emissions monitors.

    My whole reasoning for the WEAK EV State existing as some sort of protection mechanism makes less sense now that the EV Mode button makes my Prius behave like the MAX EV State. It may actually be a glitch of some kind that causes the WEAK EV State to chronically persist and never engage the MAX EV State... but I'm fairly sure the WEAK EV State exists for a reason still... it's supposed to be a normal part of the Software Programming.

    Think of the EV Mode button as a "Forced Software State" that causes the Prius to use EV Mode very aggressively by pushing a button... while the MAX EV State is a "Master Phantom Software State" that is supposed to trigger from reading other prius computer parameters and verifying certain conditions. It exists omnipresently in the software and during all driving conditions once triggered. Once it triggers... EV Mode has very aggressive useage between 3-8 bars of charge and up to 40mph for the Gen 2 Prius.

    The reason no one has ever identified this as a serious widespread issue... is because it's completely phantom. You could even be in the WEAK EV State right now @dolj and you'd have no idea.

    No error code or way to view this parameter/software state makes itself known in Toyota Techstream... so when you take your Prius to the Dealer complaining about sudden low mpg or loss of EV Power... they'll hook up Techstream and everything will seem perfect. They'll say you need to hypermile or it's bad gas or something to that affect.

    I believe Toyota has already been sued for the WEAK EV Software State... but the cause of the Low mpg/engine running more was misplaced.

    In the LA TIMES article screenshots below... multiple Prius owners complain of having low mpg, the Combustion Engine running more, less EV Power after the Hybrid Control ECU update to protect the Inverter.

    [​IMG]

    The Prius owners complained of low mpg and differences in drivetrain behavior after the update... leading to lawsuits against Toyota


    [​IMG]

    [​IMG]

    Toyota then issued A statement that we don't believe the software update should significantly reduce mpg... and they were technically right.

    The loss of mpg and EV Output as a result of the Hybrid Control ECU update... was not a direct result of the ECU update... but an indirect result of the computer reset that occured during the process... resetting the Prius to the WEAK Ev Software State.

    [​IMG]

    [​IMG]

    So this WEAK EV State Software that was already latent in the Hybrid Control ECU... and exists outside of the Hybrid Control ECU update that was issued... was activated during the update.

    Toyota and the Prius Owners that were effected by this... were looking in the wrong place in the software for the cause of the Low mpg. The Prius Owners were not wrong that they were experiencing lower mpg and different Hybrid Drivetrain behavior after the software update.
    It's just that as a byproduct of the software update... the WEAK EV State was triggered.

     
    #79 TheLastMojojomo, Aug 17, 2023
    Last edited: Aug 17, 2023
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  20. dolj

    dolj Senior Member

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    As someone who has had use of the EV button for my entire Prius experience (on Gen 2 only too), I don't believe this to be correct. It is more like 6-8 bars and the same for cruising at 40 MPH. In fact, I can "golf-cart" without the use of the EV button as long as it is flat and I have 6-8 bars on the gauge but the SoC drops rapidly so it does not last long.
    I believe I have experienced the weak state you're talking about, but not for a long time, and as an experienced Prius driver when it happens it is quite obvious something is not right. I'm pretty confident my Prii do not exhibit the phenomena currently.

    A thought I have been pondering, do you have any correlation in your data between the HV battery's capacity and the propensity for the weak EV state to occur (outside of it being triggered by a 12 V battery disconnect)?