When is an EV not EV?

Discussion in 'Gen 4 Prius Technical Discussion' started by dstahre, Dec 26, 2016.

  1. dstahre

    dstahre Member

    Joined:
    Apr 17, 2016
    74
    35
    0
    Location:
    Cahokia
    Vehicle:
    2016 Prius
    Model:
    Four Touring
    Got a situation and perhaps it has been addressed before but I have times when the power flow monitor shows the ICE not running, the instantaneous MPG is maxed out but the EV indicator is not on. What gives? Is the ICE running or not? Like I said the mileage is maxed out. o_O
     
  2. fotomoto

    fotomoto Senior Member

    Joined:
    Apr 22, 2009
    5,325
    3,560
    0
    Location:
    So. Texas
    Vehicle:
    Other Hybrid
    Sounds like you were in a "glide" which is power neutral; the holy grail of hypermilers! (y)
     
    Trollbait, dstahre and alanclarkeau like this.
  3. alanclarkeau

    alanclarkeau Senior Member

    Joined:
    Feb 24, 2016
    6,602
    7,218
    0
    Location:
    near Brisbane, Australia
    Vehicle:
    2016 Prius
    Model:
    N/A
    It's not an EV - it's a hybrid. The computer looks at many settings - your climate control, inside and outside temps, speed, battery charge, whether the ICE is warmed up, throttle position, probably even recent driving style etc etc and decides whether it will use ICE or Battery, a mix of the 2, regeneration etc.

    I've noticed that the Energy Monitor sometimes is in front of the instantaneous MPG (l/100km here) by a couple of seconds - I get the feeling that the Energy Monitor is right (can hear the ICE shut off when slower) - maybe the instantaneous MPG is taking sampling over short periods of time, or slightly "historical"?

    Playing with trying to force it to "EV" when it doesn't particularly want to doesn't seem to help my mileage usually, except in very limited situations. That is unless you are trying seriously to hypermile - which most of us don't, and we can't in many driving situations unless away from traffic.
     
    RCO and dstahre like this.
  4. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    92,321
    41,742
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    the monitor is only semi reliable. if you really want to know what's going on instantaneously, get a scan gauge or some such.
     
    kithmo, RCO and dstahre like this.
  5. greenmonster01

    Joined:
    Apr 15, 2015
    106
    79
    0
    Location:
    Southeastern MA
    Vehicle:
    2016 Prius
    Model:
    Two
    Yeah, there's times where we're just gliding... must be in fuel cutofff (or pretty close to it).

    There are times when my instantaneous reads about 75-80mpg, but I can't seem to stay in glide mode for that long.

    If only there was lean burn mode....
     
    RCO and bisco like this.
  6. alanclarkeau

    alanclarkeau Senior Member

    Joined:
    Feb 24, 2016
    6,602
    7,218
    0
    Location:
    near Brisbane, Australia
    Vehicle:
    2016 Prius
    Model:
    N/A
    NOT like a TESLA, I hope?
    upload_2016-12-27_13-33-54.jpeg
     
    RCO likes this.
  7. bhtooefr

    bhtooefr Senior Member

    Joined:
    Apr 4, 2016
    1,366
    1,458
    0
    Location:
    Newark, OH, USA
    Vehicle:
    2016 Prius
    Model:
    Three
    Lean burn mode would massively increase NOx emissions, which is unacceptable, especially nowadays.

    So, the reason why lean burn improves efficiency is because it allows the throttle to be open more, reducing pumping losses - a significant amount of power is lost in sucking air past the throttle plate. However, the Prius has several strategies to reduce pumping losses without having excess air in the cylinder (lean burn).

    Atkinson cycle operation is one of those strategies - essentially, all Prius engines push some excess air back out of the cylinder, reducing their effective displacement, while maintaining their full expansion. A Gen 3 or 4 Prius engine only takes about 1.1 liters of air per 2 revolutions, not the 1.8 that the stated displacement implies.

    Variable valve timing allows the computer to tweak how long the intake valves are held open, allowing it to change how much air gets pushed out.

    Cooled exhaust gas recirculation allows the engine to replace excess air with inert gas - the throttle can be held open further that way. That only works to a point, though.

    Finally, there's the hybrid system. Its primary goal is to keep the engine at its most efficient operating range, which is relatively high load, moderate RPM. If there's too low of a power demand to satisfy that, a normal car will just have to close the throttle plate and run inefficiently. The Prius, however, can do one of two things - it can instead use excess power to charge the battery, or it can shut down the engine and use stored battery power to propel the vehicle (and, in fact, at lower speeds, it will cycle between the strategies).

    Note that the Gen 4 Prius is up to 40% peak thermal efficiency without lean burn. There's only three other gasoline engines that have reached that target, as far as I'm aware (I'm not including the Mazda SkyActiv-G family, because there's nothing concrete saying that it's actually hit 40%, just that it's in the ballpark) - the hybrid variant of the Hyundai Kappa 1.6 liter as used in the Ioniq and Kia Niro (which uses some of the same strategies, as well as direct injection, which allows higher compression, and therefore more expansion ratio), the Toyota Dynamic Force 2.5 liter most likely destined for the next-gen Camry (which uses a more extreme variable valve timing approach to drastically vary the amount of Atkinsonization, and direct injection), and the hybrid variant of the Dynamic Force 2.5 liter (which is at 41% thermal efficiency). None of those are lean burn, and two of those are intended for hybrid applications (which can, again, keep it on the peak much more closely, further reducing the need for lean burn).

    Now, I'm going to go against my entire point here, and mention that diesels are always lean burn, and there are more efficient diesels out there - Toyota has a 2.8 liter diesel for pickups and vans at 44% thermal efficiency. (The increased expansion ratio enabled by the high compression ratio helps, too.) So, it can help, but you've got an emissions penalty to pay (both because of lean burn, and because of how it injects its fuel and starts ignition), that needs complex, expensive aftertreatment systems, pricing it into the work vehicle or the luxury space. And, the weight of the diesel engine, plus the weight, cost, and packaging penalty of its aftertreatment systems makes hybridization much harder.
     
    #7 bhtooefr, Dec 26, 2016
    Last edited: Dec 26, 2016
  8. dstahre

    dstahre Member

    Joined:
    Apr 17, 2016
    74
    35
    0
    Location:
    Cahokia
    Vehicle:
    2016 Prius
    Model:
    Four Touring
    This happens typically around 45 mph and has a pretty good duration. Normally the traction battery is well charged and there doesn't seem to be any reason why it shouldn't go into EV mode. I suspect that the vehicle is effectively in EV mode. Perhaps the engine and MG1 is driving accessories, electronics and environmentals, but not providing any propulsive effort?
     
    alanclarkeau likes this.
  9. alexgrigori

    alexgrigori Active Member

    Joined:
    Oct 6, 2016
    163
    106
    0
    Location:
    Canada
    Vehicle:
    2017 Prius
    Model:
    Technology
    EV indicator (EV mode icon) is on only if EV mode is forced on by pressing a designated EV mode selection button. In my Prius 'forced' EV mode is available on low speed up to 30-32 km/h. At a higher speed battery propelling (or EV condition if you will) is controlled by on-board computer without EV mode indication.
     
    #9 alexgrigori, Dec 28, 2016
    Last edited: Dec 28, 2016
    RCO likes this.
  10. bhtooefr

    bhtooefr Senior Member

    Joined:
    Apr 4, 2016
    1,366
    1,458
    0
    Location:
    Newark, OH, USA
    Vehicle:
    2016 Prius
    Model:
    Three
    There's an "EV" indicator in the Hybrid System Indicator, as well, though, independent of the "EV Mode" indicator in the speedometer.
     
    alexgrigori, alanclarkeau and RCO like this.
  11. dstahre

    dstahre Member

    Joined:
    Apr 17, 2016
    74
    35
    0
    Location:
    Cahokia
    Vehicle:
    2016 Prius
    Model:
    Four Touring
    Not true! EV is on whenever you are in EV mode. I've seen it as high as 65mph
     
  12. bhtooefr

    bhtooefr Senior Member

    Joined:
    Apr 4, 2016
    1,366
    1,458
    0
    Location:
    Newark, OH, USA
    Vehicle:
    2016 Prius
    Model:
    Three
    "EV Mode" and the icon for it refers to a mode enabled by hitting a button labeled "EV Mode", and that only works up to about 20 MPH, and only with moderate throttle at most.

    However, the EV indicator in the HSI can be illuminated due to the engine shutting off at higher speeds, and the engine is off there. I've seen that happen as high as 73 MPH.
     
  13. dstahre

    dstahre Member

    Joined:
    Apr 17, 2016
    74
    35
    0
    Location:
    Cahokia
    Vehicle:
    2016 Prius
    Model:
    Four Touring
    If the engine is off and you are on battery power then you are EV and 90% of the time the EV indicator is on and the power monitor agrees with it!
     
    #13 dstahre, Dec 31, 2016
    Last edited: Dec 31, 2016
  14. RCO

    RCO Senior Member

    Joined:
    Aug 31, 2016
    3,709
    5,175
    0
    Location:
    Cornwall
    Vehicle:
    Other Hybrid
    Model:
    N/A
    That's perfectly true, but bhtooefr is talking about the EV Mode. That is, when selected by pressing the EV button. Only pressing that button technically selects the EV Mode.
     
    alexgrigori likes this.
  15. Trollbait

    Trollbait It's a D&D thing

    Joined:
    Feb 7, 2006
    16,563
    7,804
    0
    Location:
    eastern Pennsylvania
    Vehicle:
    Other Non-Hybrid
    But your electric was all made from gasoline.
     
    RCO likes this.
  16. alexgrigori

    alexgrigori Active Member

    Joined:
    Oct 6, 2016
    163
    106
    0
    Location:
    Canada
    Vehicle:
    2017 Prius
    Model:
    Technology
    most electricity is from fossil fuel...

    BTW, Happy New Year!!!
     
    RCO likes this.
  17. Trollbait

    Trollbait It's a D&D thing

    Joined:
    Feb 7, 2006
    16,563
    7,804
    0
    Location:
    eastern Pennsylvania
    Vehicle:
    Other Non-Hybrid
    In power plants with average thermal efficiencies greater than seen in a car ICE.;)
     
    alexgrigori and RCO like this.
  18. alexgrigori

    alexgrigori Active Member

    Joined:
    Oct 6, 2016
    163
    106
    0
    Location:
    Canada
    Vehicle:
    2017 Prius
    Model:
    Technology
    burning is burning = CO2 + H2O
    :)
     
  19. RCO

    RCO Senior Member

    Joined:
    Aug 31, 2016
    3,709
    5,175
    0
    Location:
    Cornwall
    Vehicle:
    Other Hybrid
    Model:
    N/A
    With apologies to Frozen, let it go....
     
    kithmo, krmcg and Prodigyplace like this.
  20. dstahre

    dstahre Member

    Joined:
    Apr 17, 2016
    74
    35
    0
    Location:
    Cahokia
    Vehicle:
    2016 Prius
    Model:
    Four Touring
    I'm talking "Toyota" the "EV" mode is when you are on battery power with the engine off. THAT is what is called the "EV" mode and what I'm questioning is why there is a situation where the engine appears to be off, the car on battery power, and the EV indicator is not on, I never said the car is an EV.