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P&G Pre Braking Affect on Brakes

Discussion in 'Gen 2 Prius Main Forum' started by puppetmasta, Jun 22, 2006.

  1. puppetmasta

    puppetmasta New Member

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    I recently read some tips about how to P&G (Pulse and Glide).

    In those tips it suggested that when you are coming to a stop slowly that you should barely put your foot on the brake to create more energy to charge the battery.

    My question how of the braking is actually done in the engine? I've heard alot of different people say that alot of it is in the engine and that the brake pads are only used when braking abruptly.

    The reason I ask is because I don't want to prematurely wear down my brakes just to charge the battery faster when coming to a stop.

    Any ideas on this?

    Thanks,
    Dave
     
    #1 puppetmasta, Jun 22, 2006
  2. ScottY

    ScottY New Member

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    It's actually the MGs (motors/generators) that do the braking most of the time. When you brake normally, current is drawn from the MGs creating drag to slow down the car. This is called regenerative braking. You are not using the physical brake pads at all till you are down to ~7mph (or step on the brake pedal hard and fast). You will feel the difference in braking around 7mph, which is caused by switching from regen to physical brake.
     
    #2 ScottY, Jun 22, 2006
  3. efusco

    efusco Moderator Emeritus
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    In the Prius II a huge amount of the braking is done by the MG (not the Engine aka ICE) IF you don't brake too quickly or too hard and if you don't hit any bumps while braking. In brisk or emergency braking all the braking is done by the friction brakes. But, with practice, on routine stops you can brake solely with the regenerative braking via MG2 until your speed drops to 7mph.
     
    #3 efusco, Jun 22, 2006
  4. puppetmasta

    puppetmasta New Member

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    Thanks! This answers my question, the brakes will not be worn by just barely tapping on the brakes.

    Great engineering on Toyota's part. Man I love this car.
     
    #4 puppetmasta, Jun 22, 2006
  5. auricchio

    auricchio Member

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    Exactly. The pads and shoes may last the life of the car, barring wear caused by rusted rotors. Occasional brisk braking will clean the rotors.

    Remember to brake firmly in reverse every few months to allow the self-adjusters to adjust the rear brakes. (But if they don't wear, even this isn't an important step!)

    I've also heard that the brake computer tries to apply a bit more pressure to the rear drums, to balance wear. Front brakes always wear faster due to the weight shift during braking, so the computer even tries to help a bit there.
     
    #5 auricchio, Jun 22, 2006
  6. Syclone

    Syclone Member

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    <div class='quotetop'>QUOTE(Rick Auricchio @ Jun 22 2006, 01:01 PM) [snapback]275297[/snapback]</div>
    Im curious about the rear brakes. Since they are drum brakes, the drums do not contact the inner surface of the brake drum unless there is pressure applied to the hydraulic system. With the regen system taking up 90% of the braking action, it seems to me that the rears never actually are engaged until you get down to 7 mph. This means that most of the time the car has 2 wheel braking, which in a normal car can result in front end dive when you hit the brakes. Obviously, the Prius doesn't do that, so what is going on?

    Sy Cohen
     
    #6 Syclone, Jun 22, 2006
  7. DaveinOlyWA

    DaveinOlyWA 3rd Time was Solariffic!!

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    the vancover taxi Prius replaced its brakes at more than double the recommended mileage. that may not seem like a lot except that generally, taxi's replace their brakes at 60-75% recommended mileage because of the work they do.
     
    #7 DaveinOlyWA, Jun 22, 2006
  8. hobbit

    hobbit Senior Member

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    #8 hobbit, Jun 22, 2006
  9. puppetmasta

    puppetmasta New Member

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    <div class='quotetop'>QUOTE(hobbit @ Jun 22 2006, 10:28 PM) [snapback]275623[/snapback]</div>
    Sounds like something alot of Prius owners might be interested in.

    Might be useful to know if you are braking too hard (using the real brakes) vs. the MG doing the braking.

    I can see how this might help alot when you are in stop and go traffic during rush hour. There are alot of opportunities at that point to recharge your battery as you speed up and then instantly brake.

    Maybe Coastal could commercialize this?!
     
    #9 puppetmasta, Jun 23, 2006
  10. andreaswin

    andreaswin New Member

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    <div class='quotetop'>QUOTE(syclone @ Jun 23 2006, 01:20 AM) [snapback]275519[/snapback]</div>

    ohh Your rear breaks are drums brakes??? wow , i didnt know that ,, that a US thing right ?

    andreas :blink:
     
    #10 andreaswin, Jun 23, 2006
  11. ScottY

    ScottY New Member

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    <div class='quotetop'>QUOTE(andreaswin @ Jun 23 2006, 04:33 PM) [snapback]275973[/snapback]</div>
    Yeah, the NA Prius gets drum rear brakes.... <_<
     
    #11 ScottY, Jun 23, 2006
  12. andreaswin

    andreaswin New Member

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    <div class='quotetop'>QUOTE(ScottY @ Jun 23 2006, 10:40 PM) [snapback]275978[/snapback]</div>

    hmm thats very close to insulting.......... :blink:
     
    #12 andreaswin, Jun 23, 2006
  13. hobbit

    hobbit Senior Member

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    Heh. Coastal claimed they *were* going to commercialize the brake
    pressure indicator, and never did. I decided to go my own way.
    If they swipe the idea and make a ton of money off it and I never
    see a red cent of it for my contribution, it won't be a surprise
    given Coastal's track record. In the meantime, the electronics-handy
    can stop waiting for them.
    .
    _H*
     
    #13 hobbit, Jun 27, 2006
  14. mkaresh

    mkaresh Member

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    If you hardly ever use the rear brakes, why does it matter if they are drums? Just because?
     
    #14 mkaresh, Jun 27, 2006
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