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DRCC Braking

Discussion in 'Gen 3 Prius Main Forum' started by cproaudio, Jun 6, 2011.

  1. cproaudio

    cproaudio Speedlock Overrider

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    Just a reminder that in an event of hard braking, such as someone cut into your lane or unexpected traffic jam, don't panic and apply the brakes. Just let the DRCC brake for you.

    Unlike some radar cruise control that only uses up to 20% of the braking power, the Prius's Dynamic Radar Cruise Control system utilizes up to 100% of the braking power. As the DRCC brakes, it will utilize friction brake and brake as hard as it needs to maintain a safe distance between you and the car in front of you down to 25mph. By the time the car lost its braking momentum, you'll slow down to about 17-20mph.

    Let's say a car cuts in front of you, DRCC goes into panic braking using friction brakes. As your Prius approaches the car in front of you, you then panic and apply the brakes. The DRCC will cancel and release the friction brakes. You are now left with fractional regen braking, giving you a false feeling of sudden acceleration. You would have to depress the brakes much further to regain the same braking force that the DRCC was initially braking at. Be safe out there.
     
  2. indyV

    indyV Junior Member

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    Do you speak upon experience?
     
  3. 32kcolors

    32kcolors Senior Member

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    You're comfortable doing that, yet are scared as hell of IPA ramming your car?
     
  4. cproaudio

    cproaudio Speedlock Overrider

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    Yes, twice. When I first got the car, I panicked and braked and almost hit the car in front of me. That's how I know not to brake when DRCC is braking. And another 2 times where I let the DRCC brake for me with at least 50-80% of braking power. Once with my mom and another time with my dad. The one with my dad was intentional. It didn't brake as hard as the one with my mom. The one with my mom was accidental. I was talking to her and not paying attention to the road and all of the sudden, the DRCC beeped and it braked hard enough that the grocery fall off the back seat and onto the floor. My mom asked if I braked and I said "No, the car did."

    I always set the following distance at 3 bars so I always have about 3 seconds of following distance. At 70mph, 3 seconds is about the length of a football field. There's still enough room for me to brake to a complete stop.
    And hell yeah I'm still scared of the IPA curbing my rims.
     
  5. robby3

    robby3 Member

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    In the cars with HUD the display shows an allert sign and tells me to brake even the car already applied the brakes.

    A real dangerous situation activates the seatbelt motors, brakes heavily and flashes the stop lights (experienced this two times). This is a strange experience! But I don't believe it uses 100% of braking power as it initial braking gives you enough time to brake and tells you to do so. And no I don't have to press the brake pedal so much down to get the braking power. In such situations you gonna slamm the brakes anyways - otherwise it's too late.
     
  6. 32kcolors

    32kcolors Senior Member

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    If a car cuts in front of you, you have less than 3 seconds. You're asking us to trust the system, yet you won't trust the same system when it comes to IPA. Makes no sense.
     
  7. cproaudio

    cproaudio Speedlock Overrider

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    Let's say you're traveling at 70mph. Another car traveling at 60mph cuts in front of you. The cruise will brake from 70 to60 in a matter of seconds. While it's baking, and you apply the brakes, it will release the friction brakes leaving you with regen brakes until you depress the brakes further to reactivate the friction brakes.
    The problem with the IPA is the low resolution screen. When setting up the parallel parking, the green box looks like it's sitting on the curb. If I adjust it visibly off the curb then it's too far. If I don't adjust it away from the curb then I'm afraid it's going to curb the rims. If the screen is hi res, then it's easier to differentiate the box and the curb. I have no problem letting it do back in parking. I do that all the time.
     
  8. robby3

    robby3 Member

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    I did not experience this in the situations I had. There was no brake release as I pressed the padel hard a quick. Is your description somewhere documented in the manual or even service manual?
     
  9. cproaudio

    cproaudio Speedlock Overrider

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    I'm just speaking from experience.
     
  10. tomlouie

    tomlouie Member

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    If you brake hard enough, the friction brakes will come on, period. If DRCC braked before you did, then you either need to hang back further or brake sooner.

    IMHO, a driver shouldn't leave it to the DRCC to hit the brakes for them, as it dilutes the driver reflex to hit the brakes when they need to reduce speed.
     
  11. qbee42

    qbee42 My other car is a boat

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    I was going to hit the "thanks" button for this post to give it a +1, but since this is a safety issue it's worth making an additional post. The method suggested in the OP's post is dangerous and ill-advised. The one here is correct. DRCC is intended to be a safety backup system, not the primary controller of the car. In a panic situation, mash on the brakes. Do it fast and hard and you won't have to worry about regeneration or the reliability of DRCC.

    Tom
     
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  12. ETC(SS)

    ETC(SS) The OTHER One Percenter.....

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    Concur.
    Tom is right, as usual...and yes. Danny should pay him.

    Think you should rely on your DRCC?
    It's a heckuva good system. A little expensive for my tastes, but DVD players used to cost most of a thousand bucks too.
    Once the non-recurring engineering fees are recovered they'll probably be standard equipment in Yaris-class cars until some low octane type runs out of other things to get pissed about and starts squealing about electromagnetic pollution.

    However (comma!) they do break!...not to be confused with brake!!!
    DRCC Malfunction?

    Yeah....I know.
    In this one gezample the DRCC was braking when it shouldn't. It can go the other way too.
     
  13. Thai

    Thai Prius Neophyte

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    Actually, for me, DRCC is too conservative at times...it brakes too much. So, i would override it. :)
     
  14. unkprius

    unkprius Member

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    '....However (comma!) they do break!...not to be confused with brake!!!...'

    I wouldn't worry about it failing so much as me forgetting that I =hadn't= turned it on......after the crash............
     
  15. Dweezil

    Dweezil Cat Juggler

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    So (comma) I purchased my 2010 V with ATP simply because it was the best deal on the lot at the time. I don't know that I would've sought out a car with ATP...mine just happened to have it...remember, I bought my gently used with about 4k on the odom.

    I've had the DRCC apply braking a couple of times when folks feel they just HAVE to be in front of me on the highway...only to slow down. I generally use the braking on my DRCC to freak out my passengers. It's great fun...well worth the extra $$$ in entertainment value alone.
     
  16. macman408

    macman408 Electron Guidance Counselor

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    +1 for each of the Toms, plus a relevant quote from the manual:
    Press the brake pedal hard and fast if you have any doubts about the DRCC's ability to slow down fast enough, especially when it's warning you about it. And if you press suddenly, it's also likely to engage the Brake Assist system, where it applies the brakes harder than you're telling it to because it detected a panic stop situation. It might also use the Pre-collision Brake Assist, which is the same thing, but activated when the radar sees an obstacle instead of based on how quickly you hit the brakes.
     
  17. cproaudio

    cproaudio Speedlock Overrider

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    In my experience, if I hit the brakes while the cruise control decelerates, there's that fraction of a second of no braking. It feels a lot like braking over a pothole. There's a feeling of sudden acceleration. Thats why when the cruise is braking, I just let it brake. If someone cuts in front of me and the DRCC fail to slow down, then yeah I hit the brakes.
     
  18. robby3

    robby3 Member

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    Wait a second, you mix up cruise control and DRCC. Even they use the same radar and electronics the control process is different. What you have experienced is the moment you disable the cruise control with the brake switch. It then disables any accellerating or decelerating. While it is decelerating and the switch disables cruise control the braking is gone of course too and this is what you feel. At this moment DRCC is not yet thinking of any braking at all. Disabling cruise control while decellerating feels the same in any other car too and has nothing to do with DRCC.
     
  19. cproaudio

    cproaudio Speedlock Overrider

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    I meant DRCC
     
  20. tomlouie

    tomlouie Member

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    Let me see if I understand you. In an emergency situation, you want to avoid hitting the brakes while DRCC is already braking because of the "fraction of a second of no braking". Instead, you'll willing to wait for the DRCC to kick in, and if "DRCC fail to slow down, then you hit the brakes".

    How much time passes while you wait for DRCC to brake? Compared to the fraction of a second of no braking? How far does your car travel at highway speeds while you're waiting and watching to see if DRCC will kick in?

    Please reconsider your line of thinking for the safety of yourself and those around you.

    Tom