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"B" mode

Discussion in 'Gen 3 Prius Technical Discussion' started by FireIsBorn, Aug 12, 2009.

  1. FireIsBorn

    FireIsBorn Junior Member

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    After benifitting from the extra NiMH charging downhill with the "B" engaged, how do we disengage it? Also, if we are going down a smaller hill, can we put it into "N", and back into "D" while driving?

    Thanks
     
  2. PeteJE

    PeteJE Junior Member

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    I just shift straight back to D from B. Don't worry about moving past N on the shift when doing so; I believe you have to hold the shifter at N for a second or so to actually go into N.
     
  3. fred garvin

    fred garvin New Member

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    there are several threads where this is discussed - you should search

    there is a speed above which you shouldn't coast in "n"
     
  4. morpheusx

    morpheusx Professor Chaos

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    Unless something has changed with the 2010 there is no extra charging benefit with shifting into B. The B mode uses the engine to throw away energy to keep your speed under control while coming out of the mountains you should rarely ever need to use it.

    It's not a good idea, I prefer to let the hill give me some regen, but many hypermilers do perform this trick. If they initially start down the hill while gliding they can switch to "N" to prevent the engine from coming on and to travel at speeds higher then the 41 MPH threshhold (in the Gen.II.) that being said I believe that if you are somewhere around the speed of 50 - 55 MPH while in "N" you will damage one of the electric motors (I believe its MG1)
     
  5. ksstathead

    ksstathead Active Member

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    Search for nomograph. These show the HSD component interactions, and let you see exactly what speed keeps the MG's within design limits.

    As stated, don't use B for regen. Use it on long descents.
     
  6. hobbit

    hobbit Senior Member

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    Warp-neutral works in the third-gen, too. Great in the hills.
    .
    _H*
     
  7. bwilson4web

    bwilson4web BMW i3 and Model 3

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    If the engine is running because you are already above 46 mph (ZVW30) or above 42 mph (NHW20/NHW11), there is no problem. The engine will spin faster as needed to meet the control law goals. Several of us have coasted down grade to exceed the control law limits with the NHW20/NHW11 and saw no failures. However, I don't recommend it because it does violate the control laws on over-spinning MG1. Otherwise, I have no problem with shifting into "N" at any time.

    There have been several discussions of the risk and so far, no one has reported an MG1 failure from over revs. We've also speculated about the generated voltage being too hand and resulting in over stressing the inverter. But again, no one has done the 'forbidden' experiment and tested to destruction.

    Bob Wilson
     
  8. pfreeus

    pfreeus New Member

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    This is very intersting and explains the MPG quirk we've been getting. We live in on on the foothills and there is a 1/2 mile downgrade we have to travel pretty much when we leave our street. In "D" I notice the MPG vertical guage hovers around 25 mpg. When I put it in "B" is it just north of 75 but not 100 mpg. Is this because the "B" mode is helping to warm up my engine so less gas is consumed to warn it up?

    It was very confusing as I thought I should be registerint 100 mpg as gravity is working and not the engine.
     
  9. RickFlashman

    RickFlashman New Member

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    My 2010 shows as "Charging" when B is engaged, much higher level than regular braking.