"B" on transmission.

Discussion in 'Gen 2 Prius Main Forum' started by brockketcher, May 19, 2005.

  1. brockketcher

    brockketcher New Member

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    I just picked up my prius...put 350 miles on it in the first two days...love it. Can someone tell me when and where they use the "b" on the transmission to thier benifit???? I don't get it. I asked the sales person and he said to use in in town...but I read the manual and it said not to use it for long periods of time. whats the deal???? thanks
     
  2. Godiva

    Godiva AmeriKan Citizen

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    It's not B for battery it's B for brake.

    Someone will correct me if I'm wrong....but I believe you use it when you have a lot of downhill driving. It's an engine assisted brake...the equivalent of low gear on a conventional car.
     
  3. Frank Hudon

    Frank Hudon Senior Member

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    if you do a search on B here on PC you'll find at least 2000 lines on it.
     
  4. xevious

    xevious New Member

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    1) Use the search feature.

    2) Please post in the appropriate forum. This is not newsworthy.

    Enjoy your Prius!
     
  5. Sufferin' Prius Envy

    Sufferin' Prius Envy Platinum Member

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    Page 138 of the Owner’s Manual kind of covers what “B†is for, but they could have done a better job of explaining the function is like low gear in less advanced cars.

    Toyota so should have labeled it “L†for low gear, or “EB†for engine braking. “B†is not intuitive.

    [You are right xevious . . . this thread is not “News.†I clicked on the blue square to notify the moderators . . . but more out of curiosity in seeing what the blue squared does.
    I guess we shall see. :wink: ]
     
  6. Wolfman

    Wolfman New Member

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    The blue box just emails us mods, to let us know that a member has reported an improper post.

    We can then decide the appropriate course of action, if any. In this case, the thread has been moved to the general forum.
     
  7. DanMan32

    DanMan32 Senior Member

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    B=Brake. Works for me. L=Low wouldn't be completely accurate. Unlike a true Low, B does not affect acceleration, only braking.
     
  8. Mystery Squid

    Mystery Squid Junior Member

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    IMO, I avoid engine braking, I have yet to be convinced periods of engine load at the expense of brake pads/rotors wear is truly "worth it". Can't speak for the Prius yet, but higher end pads and rotors for any car I've ever owned just aren't that expensive, and they're easy to replace by the home mechanic....
     
  9. Jaguar88

    Jaguar88 Member

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    I don't know if engine braking is good or bad. I thought it was a continuous regenerative braking mode. I use it everyday on my way to work.
     
  10. Mystery Squid

    Mystery Squid Junior Member

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    "good or bad"... That's sort of like saying which is better MAC or Windows... lol There are TONS of arguments about that.

    On another note, unless I'm mistaken, I don't THINK engine braking increases regeneration by any margin. I could be wrong, let's see what Danman chimes in with... :mrgreen:
     
  11. jeromep

    jeromep Member

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    B is an automatic low gear simulator, through the use of engine compression braking, a reliable and well developed technology that is many, many years old. In fact, so many things are simulated on the Prius that we don't really notice it. Break pedal feedback is essential simulated. Braking feels like friction braking, however it is mostly regenerative except for very low speeds or panic braking situations. I have read it here described as a "wet" brake by wire system since hydraulics are involved at many different stages in the system. Steering is still physically connected to the rack, however the electric assist system simulates much of the same behavior as a hydraulic system. Throttle is also by wire. This has been offered for many years now on vehicles from many different manufacturers. Pedal resistance is provided by springs rather than the drag of a cable going to a throttle body.

    Engine braking is not bad for the engine. The engine reverts to its more primitive form, a compressor. It is fully oiled and cooled when in B mode and therefor there is no more wear and tear than if the engine were running.

    I'm sure that Danman has more detail to add.
     
  12. coloradospringsprius

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    I used "B" mode for the first time a couple of weeks ago, coming down Cameron Pass in Colorado. It was great - I'd never used the brakes so little on a long mountain descent. I've never seen any need for it on regular hill. The standard light regen touch on the brakes works fine.
     
  13. Mystery Squid

    Mystery Squid Junior Member

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    Well see, there I sort of disagree (at least, in terms of usage. I've even read opinions that say engine braking should be encouraged). The engine is being used, as opposed to not being used. Therefore, on the most basic level, it is, at the very least, being used when "engine braking". :mrgreen: Whereas by using brakes, you are not using the engine, simply wearing brake pads and rotors. Given, what would you rather place wear upon?

    IMO, the only vehicles that legitimately have the need for engine braking, are large, heavy vehicles, various sports cars, of if your brakes should completely fail for whatever reason. The pads and rotors on the Prius are ample for its weight, and will likely last a long, long, time....
     
  14. brandon

    brandon Member

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    A coworker of mine has a long, narrow, steep, and winding gravel trail (without a shoulder) that leads up to his home from the highway. You don't want to go faster than about 8 mph or you'll lose control and total your Prius. I use "B" on the descent after visiting him. I feel I have better control over the vehicle than with the standard brake setup.
     
  15. jeepien

    jeepien Member

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    But it is not true that by stepping on the brake pedal you are necessarily "using brakes". You are probably just using regen braking, and therefore wearing out neither the brake pads nor the engine.
     
  16. Frank Hudon

    Frank Hudon Senior Member

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    MG2 in generator mode sends it's output to MG1 which uses the ICE as a load to buck against to absorb the current that would normally go to recharge the battery. When you have all green bars (80% charge) the battery will not accept anymore charge and if the hill your on is long enought you'll note that in D mode your using the friction brakes to keep the cars speed in check. If you then put it in B mode the output from MG2 goes to power MG1 to slow the car by using the ICE as a load.
     
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