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Shift position B

Discussion in 'Toyota Prius Plug-in' started by chesleyn, May 12, 2012.

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  1. chesleyn

    chesleyn Active Member

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    Okay, made a huge mistake today. Driving down from Beverly Hills (Mulholland Dr) I shifted into B mode to get more regen. Thought that it would only stay in B mode while I had it shifted down into that mode. I was incorrect.

    Didn't realize the car stays in B mode until 10 minutes of driving around town and I was only getting 20 mpg and the engine wasn't shutting off at red lights.
  2. massparanoia

    massparanoia Active Member

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    No harm done, other than tanked gas mileage.
  3. iRun26.2

    iRun26.2 New Member

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    That would be frustrating. Why would B mode give you more regen? I thought it would be the other way around (limited regen).
  4. JimboPalmer

    JimboPalmer Nadir of Wrongness

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    iRun it is a persistent misunderstanding of what B mode is for.

    It never gives more regen than an equivalent amount of braking.
  5. FUUFNF

    FUUFNF Forum Lurker

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    Can you throw the car into B at any speed? Say you were coming down a mountain doing like 70, can you throw the car into B or would that ruin the transmission?
  6. The Electric Me

    The Electric Me Go Speed Go!

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    But isn't that true? It will stay in B mode, while shifted into B mode...but it will come out of B mode, when you shift out of B mode.

    But you do have to shift out of B mode...it doesn't magically know you don't want B mode anymore.

    What am I missing?
  7. john1701a

    john1701a Prius Guru

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    Makes you wonder how many never come to that realization.

    I remember encountering an owner who hadn't discovered how to properly keyless unlock the door for almost 2 years. The act of passing his hand within the handle went unnoticed. He thought pushing the button was required and was somehow able to do that without causing it to lock, resulting in an unlocked state from his particular hand placement.

    I also remember it taking me about 2.5 years to figure out why a small number of people had reported not being able to shift into "D" sometimes. Turns out, they were hitting the power button before the brake was fully depressed. It take split-second timing to actually do that. And of course, those rapid-starters weren't paying close enough attention to notice the subtle difference.

    Stuff happens. We do our best to share our experiences, so others don't have to make the discovery on their own.
  8. chesleyn

    chesleyn Active Member

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    I thought you had to hold the shifter down into b mode to get the lower engine speed. Didn't realize it would "stick". Just ignorance on my part.
  9. prj

    prj Member

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    "B" just shuts off the gas to the engine, and makes the engine pump air to slow the car. Yes, that's a good time to use it, and it won't cause any problems.

    You may hear the engine rpms increase while coasting downhill in B. It's funny, if you give it a little gas where the mountain levels off, it'll actually drop the rpms to the usual range.

    And cruise control doesn't work in B mode.
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  10. qbee42

    qbee42 My other car is a boat

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    On the Gen II Prius, B mode regenerates a bit more aggressively in some special cases, a fact which is used by some hyper-milers. I don't know if this quirk made its way into the PiP, but I wouldn't be surprised if it did.

    Also, some people think the "B" in B mode means "battery", not "brake". This adds to the confusion.

    Tom
  11. Rebound

    Rebound Senior Member

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    Perhaps the PriusChat regulars could start to refer to B Mode as Engine Brake Mode?
  12. JimboPalmer

    JimboPalmer Nadir of Wrongness

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    Yes, there are no 'gears' in a Prius, so it is not in a lower gear. Someone at Toyota was WAY too honest and did not label the position L, but you use it just like L in a 'normal' car, except there is no top speed.
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  13. Corwyn

    Corwyn Energy Curmudgeon

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    As far as I can tell there is no way to ruin the transmission. Even if the shifter actually did what you told it (rather than editing your request based on conditions), I don't think you could hurt your transmission (e-CVT). Telling the car to go into reverse while traveling 75 down the highway (and having it obey) would just put a field on an electric motor, which would cause some regen braking. In other words exactly the same thing that would happen if you wanted to do it the smart way.

    See: http://eahart.com/prius/psd/if you want a more visual understanding of what is going on.



    Unless you are one of those people who use 'L' in a normal car for dealing with low traction issues, like snow.
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  14. FUUFNF

    FUUFNF Forum Lurker

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    There's no gears in a Prius? That's interesting.
  15. Corwyn

    Corwyn Energy Curmudgeon

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    There is a planetary gear system. No changeable gears, like a standard transmission.
  16. JimboPalmer

    JimboPalmer Nadir of Wrongness

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    Mechanically, it is a one speed manual transmission with no clutch. all the 'CVT' wizardry is software, two motors, one engine and a planetary gearset.

    Park [P] is just Drive [D] with a pawl to stop the wheels from actually turning.

    There is no Reverse [R], you just spin M/G2 backwards. (M/G2 always has a fixed relationship to tire speed)

    Neutral [N] just removes the ability of the Motor/Generators to get or make electricity, you are still 'in gear'

    engineBraking is the same gear as Drive [D], you just use the engine as a air pump instead of a motive source when needed, and default to a more aggressive Regen than Drive.

    The simplicity of this system involves certain compromises, but reduces the number of parts that can break as well.
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  17. JimboPalmer

    JimboPalmer Nadir of Wrongness

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    The transaxle failures I hear of, have to do with the Motor/Generators shorting out. Toyota has no set time or mileage to change the WS ATF in the transaxle, but some PriusChat members feel that changing it at 30,000 miles, then every 60,000 miles after that may carry away metal before it shorts out the motors. It is not a bad DIY project, and at a Dealer it should be about $100. Always use Toyota's WS ATF, as it needs the electrical characteristics.
  18. FUUFNF

    FUUFNF Forum Lurker

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    Very interesting. So can you drive as fast in [R] as you can in [D]? And can you accelerate while in [N]? Also, if your technically still "in gear" while in [N], can the car be taken out of gear if needed (for instance, when getting towed or something)?
  19. JimboPalmer

    JimboPalmer Nadir of Wrongness

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    No, in [D] the engine adds to the motor, in [R] it subtracts from it. (You can't rotate an engine backwards) I bet you find 22 MPH as top speed in [R]

    in [N] the car can coast faster if it is going downhill, but that is dangerous on many levels. Never coast from less than 40 MPH to over 45 MPH

    No, it is never out of gear and there is no clutch. tow on a flatbed.
  20. netsirk

    netsirk New Member

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    I'm one of the people that doesn't understand B mode very well. If it uses engine braking, what does it do when you are in EV mode? Is there some way to do engine braking with the electric motor?
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