DRCC braking Prius 4 Touring

Discussion in 'Gen 4 Prius Technical Discussion' started by sillymike, Jun 14, 2017.

  1. sillymike

    sillymike Junior Member

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    When DRCC is set and the car brakes to slow down. Why do the brake lights not come on?

    Posted via the PriusChat mobile app.
     
  2. alanclarkeau

    alanclarkeau Senior Member

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    I thought they do - but would depend on how severe the vehicle is slowing. I though I'd seen the brake lights show shining on the car behind.

    My previous car, a diesel, had fairly good engine braking, and if I dropped back a couple of gears at a Motorway exit it would drop back to the speed limit quite quickly, but no brake lights would show as I didn't use the brake pedal.

    Have you had someone following and observing?
     
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  3. 'LectroFuel

    'LectroFuel Senior Member

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    They do come on when braking hard enough to turn them on. The DRCC may slow the car down as if in B mode with engine braking. When this happens there is more drag that slows the car down without touching the brake.
     
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  4. alanclarkeau

    alanclarkeau Senior Member

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    Thinking about it since my last reply - maybe someone with 2 cars and a spouse/friend be able to do a test run and ascertain for certain what happens?

    I've only got one car and 2 dogs, (neither of which are old enough to drive).
     
  5. sillymike

    sillymike Junior Member

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    I am cruising on the hwy at 74mph in a 70 with the DRCC set (on) car in D not B and I have 1 bar on the distance set on the DRCC as I approach a car doing 61mph and my car uses the brakes to slow down not the engine brake it does not seem that the brake lights come on. I was on the hwy late at night. I could see the car that was close behind me make a defensive move to not hit me. I could see him come closer but I could not tell if my brake lights lit up.
     
  6. alanclarkeau

    alanclarkeau Senior Member

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    I'd think that, unless it was steep downhill, it would only be regenerative braking. You can get some indication by the position of the Hybrid Indicator in your HUD - if the blue section isn't full, then it's regenerative braking:
    upload_2017-6-16_8-30-13.png
     
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  7. sillymike

    sillymike Junior Member

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    I did a test on the Hwy tonight. It's not regenerative, you can definitely feel the brakes slow the vehicle. I stand corrected on the brake lights. They do come on. I had DRCC set to 74mpgs. No one on hwy. I used the cruise control stick to reduce the mph down to 61 mph. The car brakes to slow down to the desired speed and the brake lights illuminate. I'm still curious to know in the situation of the radar picking up a slower vehicle in front of me and the car brakes to reduce speed if brake lights appear. I assume since deceleration would be the same it should under both circumstances.

    Posted via the PriusChat mobile app.
     
  8. sillymike

    sillymike Junior Member

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    Also I don't think I've ever seen my brake lights illuminate when using B to slow down. Especially exiting an Interstate. My most common use for B. Not even in my 2010 prius.

    Posted via the PriusChat mobile app.
     
  9. alanclarkeau

    alanclarkeau Senior Member

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    How do you know it wasn't regenerative braking - it's quite savage, particularly in "PWR" mode. I regularly wind my C/C stalk from 100 to 60, and it's only regenerative braking unless it's a downhill grade. Though, I'm usually in "ECO".

    I don't think anyone uses "B" mode much - I've only ever used it once.
     
  10. Prodigyplace

    Prodigyplace Senior Member

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    I agree.
    BTW, nice dogs - a Poodle and Portuguese Water Dog? I hope you have water nearby and room for them to run!
    Our Miniature American Shepherd (a smaller version of the Australian Shepherd) is a hyperactive water dog!
     
  11. alanclarkeau

    alanclarkeau Senior Member

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    It's an older photo of Winston-Gerard who was only a puppy there - he's 5 now, red pure-bred MiniPoodle. Kieara, the black with white isn't pure-bred - I got her 2nd hand - a used dog, was about 3yo then - 8yo now. Plenty of room for them to run, but no suitable water near here.
     
  12. Prodigyplace

    Prodigyplace Senior Member

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    I love the colo(u) r of your poodle! I assumed he was a standard poodle. Minis are more my size.
    I thought your black dog looked like this.
    [​IMG]

    From Photo Gallery
     
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  13. sillymike

    sillymike Junior Member

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    I forgot to mention all this while in economic mode. So in my old 2010 prius II it was definitely regenerative. It didn't have DRCC. But I'm positive in the 2017 it's using the brakes. I can feel them engage. Beautiful dogs for sure!

    Posted via the PriusChat mobile app.
     
  14. FuelMiser

    FuelMiser Active Member

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    B mode is drivetrain braking, thus not using the brakes at all, so no brake lights
     
  15. alanclarkeau

    alanclarkeau Senior Member

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    I've never seen a Portuguese Water Dog - I just looked it up - there are only 3 breeders in the country. Probably a bad photo - they were zooming around the yard when I snapped them. Winston (red) is 5kg, Kieara about 6kg.
    upload_2017-6-16_23-11-20.png upload_2017-6-16_23-7-35.png
     
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  16. Mendel Leisk

    Mendel Leisk Lapsed Cargo Cultist

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    I wouldn't shift to B for something like that.

    First off, as you mention, that is one situation where the car will slow suddenly without showing brake lights: never a good situation, doubly so on the freeway.

    Secondly, it's just not a good application of B "gear". You could likely go the entire life of the car without ever using B, or needing it. It will reduce regen braking, and reduce mpg. The reduction in regen braking is by design: it's main use is to postpone the hybrid battery becoming fully charged. And it's only practical use is for descending mountains, where there's a serious danger of the battery becoming so charged that regen braking will cease and the car will fall back to friction brakes only.
     
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  17. RCO

    RCO Senior Member

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    I think it would be a good idea if Toyota offered (subsidized/subsidised) courses to help driver's adjust to the precipitate peculiarities of the Gen 4 Prius as and how to use it properly. Obviously, many find the choices of features a stumbling block and I know I'm far from perfect. Would $€£100 be too much for such a service?

    But then you'd have to find a willing dealership with salesperson in the know. That should be a problem should it? :cautious:
     
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  18. Prodigyplace

    Prodigyplace Senior Member

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    My local salesman didn't even know Trim Two was available with interior color other than black! :eek:
    The salesman I purchased from still drives a Gen 1 Prius and spent over 30 minutes covering the Prius features before we test drove it. :D
     
  19. RCO

    RCO Senior Member

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    That's great, me too. However, it seems to me that not everyone buys from such an informed dealer and understanding of the B Mode seems to crop up more than it should. Perhaps it's just that I've forgotten all the stuff was what we used to mull over back along to we worked it all out together.
     
  20. kithmo

    kithmo Couch Potato

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    Willing and Capable. Seriously though, the Prius is the easiest car in the world to drive, so no need for lessons in that, the technology on the other hand should be explained FOC at the point of sale. I think it's just a case the many dealers don't have enough knowledge to explain it properly.
    I'm lucky, my dealer has one salesman who has a Prius as his company car/demo model so drives it all the time and another of the sales team has been on the Gen 4 induction course over in Japan before it was introduced into the UK.
     
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