Why there is default re-gen while coasting in "D" pure EV mode

Discussion in 'Prime Main Forum (2017-Current)' started by Krzysiek_KTA, Jun 16, 2017.

  1. Krzysiek_KTA

    Krzysiek_KTA Active Member

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    I am new to Prius world and am learning lot from this forum,.

    I understand that default re-gen while driving in HV mode is needed to maintain certain charge level in traction battery which is being used to improve efficiency of HV driving right?

    On other hand I can't see a point of default re-gen while coasting (taking foot off the acc. pedal) in "D" mode while EV driving. Re-gen is not 100% efficient so using all available energy to propel the car is the most effective right?

    From what I learned so far 'gliding' (depressing the acc. pedal slightly) or just shifting to "N" are the methods to eliminate unwanted re-gen. Both methods significantly improve the efficiency of EV driving (effective EV range).

    My thoughts would be that EV "D" mode without coasting re-gen at all would be the most efficient

    Any thoughts?
     
  2. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    Any driver who has driven any other vehicle expects it.
     
  3. Krzysiek_KTA

    Krzysiek_KTA Active Member

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    Expect what?
     
  4. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    "engine drag" when you lift off the gas is normal for 'torque converter' automatic transmissions and pronounced in manual transmissions. Together they represent 99.5% [made up statistic] of the transmissions on the American road. If the Prius acted differently, any driver of any previous car would have to relearn how to drive. Toyota (legal team) values presenting the same driving experience drivers are used to. (so they don't crash into the car in front of them and sue Toyota)

    As you note, there is no technical reason.
     
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  5. walterm

    walterm Active Member

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    Expects a significant slow down when removing all pressure from the accelerator If the Prius went into a true 'neutral glide' it would feel odd to someone not expecting it.

    It might be nice if they could make that a settable option, but that might cause more confusion.
     
  6. Krzysiek_KTA

    Krzysiek_KTA Active Member

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    I see.... never though of legal aspect of not simulating engine drag...
    thx
     
  7. Krzysiek_KTA

    Krzysiek_KTA Active Member

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    Agree, but driving in EV mode is by definition different so it would be just a matter to getting used to it.
    thx
     
  8. bwilson4web

    bwilson4web i3 and Prime

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    Let me see if I can through some light on it:
    transmission gear 2017 Prime 2014 BMW i3-REx
    1 N maximum coast range maximum coast range
    2 D lowest regeneration maximum regeneration
    3 B medium regeneration does not exist
    4 dynamic cruise control down to 28 mph down to 20 mph
    5 "foot fiddling" claims near perpetual motion (*) BRUHAAAAAA!

    Bob Wilson

    * - Three year old child on a "big wheel" tricycle comes to mind.
     
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  9. CharlesH

    CharlesH CA HOV Decal #5 on former PiP

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    DRCC on the Prime takes you down to a full stop. (or is that only for the higher trim levels?)
     
  10. Krzysiek_KTA

    Krzysiek_KTA Active Member

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    if the preceding vehicle is stopped it will bring the car to full stop - it is how DRCC works. I don't think it works differently on lover trims
     
  11. TonyPSchaefer

    TonyPSchaefer Your Friendly Moderator
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    Ahh the good ol days. The Gen2 Prius (2004-2009) had a "sweet spot" with the pedal where the driver could "trick" the car into not-quite-acceleration and not-quite-regen-coasting. In this state, the car was free-wheeling. In ideal situations, a driver could work the pedal and roll for quite some distance. Starting with the Gen 3 in 2010, Toyota made it considerably more difficult if not impossible to achieve the same effect.

    But back to your point. Yes, there are many times where that type of free-wheeling is more efficient in terms of maintaining momentum and would improve battery range and overall mileage.
     
  12. bisco

    bisco cookie crumbler

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    but prius regen is much stronger in glide than a standard tranny. they could probably cut it by 50%.
     
  13. Trollbait

    Trollbait It's a D&D thing

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    That sucks.:(
     
  14. bisco

    bisco cookie crumbler

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    but that reprogramming maybe part/all of the increased mpg's from gen 2 to gen 3. which helps all the prius drivers who don't read priuschat.:cool:
     
  15. Trollbait

    Trollbait It's a D&D thing

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    Much of the efficiency improvements came from improving the engine and running it at its efficient point whenever possible.
     
  16. Lee Jay

    Lee Jay Senior Member

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    That depends on the car. In my 1972 Buick Skylark GS letting off the gas pedal was about like B-mode is in my Prime.
     
  17. Krzysiek_KTA

    Krzysiek_KTA Active Member

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    To revive the subject:
    I have been playing recently with deploying 'N' to eliminate re-gen and... I was really impressed how low roll resistance the Prime has. There is no way the 'gliding' technique ( applying the acc pedal to the point there is no re-gen) could mach this. I was able to extent the EV range on slow easy non congested traffic roads significantly. Nevertheless since re-gen braking does not work in "N' one has to fiddle with the gear to engage "D" to re-gen braking. That is kinda inconvenient an might defy the benefits of switching to "N"
    Any thoughts?

    I am still learning an playing wit the car - so much fun :)
     
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  18. bwilson4web

    bwilson4web i3 and Prime

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    I've been using "N" since we got our first, 2003 Prius, and never stopped. The earlier versions had speed limits so you had to be careful going down hill with the engine off. Otherwise, it works just fine.

    Bob Wilson
     
  19. Krzysiek_KTA

    Krzysiek_KTA Active Member

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    I used to drive manual cars till 2013 when I blown my left knee, so fiddling with gears is no issue for me. Are u actually saying there is no penalty in switching to between "N" and "D" back and forth in Prime?

    I guess if one know the route (mean the stretches to glide to) then the deploying "N" makes very sense, otherwise It might be questionable. in opposition to 'gliding".
    Should the non-linearity of re-gen efficiency proved to be true then "N" gliding and strong re-gen braking would make more sense oftr the efficiency sake
     
  20. Prius from Dad

    Prius from Dad Senior Member

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    I used "N" on my 99 Solara and my 2012 v to great advantage but, in the beginning, I fooled with it in the Prime and found a combo of "B" in EV and long coasting in "D" to a stop were better than "N". Going down hill in EV mode, even on a slight down hill, will increase EV miles. Even in HV mode, using the HV portion of the battery, which replenishes better than the older Prii, is better than "N". My take is that "N" in the Prime is not does not give an advantage. Using the HV portion of the battery when there is no EV miles left is the greatest lift to mpg's. I find that any decline in the road will allow you you to use the HV portion of the battery. I use the DRCC and if there is a slight decline, I will pause It and immediately turn it back on. This should use the battery. Basically in HV mode your foot on the peddle determines if you use the battery or the ICE.
     
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