Gas & Brake at the same time

Discussion in 'Gen 2 Prius Technical Discussion' started by Tripod137, Mar 13, 2010.

  1. Tripod137

    Tripod137 New Member

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    From an AP story, "Toyota has said all Priuses are equipped with a computer system that cuts power to the wheels if the brake and gas pedals are depressed at the same time, "

    Obviously this isn't true with the "floor mat" issue highlighting the fact including my own floormat incident where the engine kept going whether I had my foot on the brake or not. The only reason the car didn't continue accelerating is because the brakes were slowing the wheels down.

    Has anyone know if this statement from Toyota is actually true?
     
  2. Politburo

    Politburo Active Member

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    Many posters here have reported that it is true for their vehicles. I haven't tried it myself.
     
  3. Helio

    Helio Member

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    In my 2007 I tried this the other day at appx 35 MPH and at that speed it did not work. the car continued to accelerate albeit with alot of drag from the brakes. One note: I neither had the brakes or the accelerator fully depressed so there must be some combination of factors that controls the power to the wheels being shut down. At highway speeds applying the brakes did shutdown the power to the wheels.
     
  4. fuzzy1

    fuzzy1 Senior Member

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    From the Toyota press release: "All Prius vehicles have a brake system program that reduces gasoline engine power if both the throttle and brake pedals are depressed at the same time." [emphasis added to both quotes]

    I haven't tried it, but the Toyota version suggests that engine power is not eliminated as some would read AP version.

    Is this consistent with your incident?
     
  5. qbee42

    qbee42 My other car is a boat

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    The Brake Override system does not cut power to the ICE (engine), it cuts power to the drive wheels.

    Many people don't understand that a Prius can run the ICE at any speed with some, none, or all of the power going to the drive wheels. It's not like an ordinary car where the engine is directly geared to the drive wheels.

    With the Prius, if you hold the gas and the brake, power is cut and friction brakes are applied. If you continue to hold the gas and brake, at low speed the system goes into forced charge mode, where the ICE recharges the HV battery, but does not move the car.

    Tom
     
  6. bac

    bac Active Member

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    I think the better question is: does it matter? As you found out, even with the gas wide open, you were able to stop the car with the brakes. The contradicts all the accounts of "I stood on the brakes, but the car continued to accelerate out of control" stories.

    -Brad
     
  7. F8L

    F8L Protecting Habitat & AG Lands

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    I have tried it numerous times and at WOT the brakes will dramatically slow you down at any speed.

    I urge everyone to try it. Just be prepared to eat steering wheel if you stomp the brakes too hard. :p
     
  8. qbee42

    qbee42 My other car is a boat

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    Been there, done that, scared myself with the sudden stop.

    Tom
     
  9. jdcollins5

    jdcollins5 Senior Member

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    I just tried this again today on my way to work (yea Saturday :confused:). It works just like qbee42 and the others say. I was watching the HSI display, running 60 mph, no one close to me, I stomped on the gas to WOT, held the pedal down and I hit the brakes with my left foot.

    Dumped everything in the seat on the floor, the HSI power monitor jumped quickly to the left and I was damn near stopped in just a couple of seconds.

    The brakes on the Gen III immediately cut the power to the ICE as soon as you touch the brakes with the accelerator pedal engaged at the same time. No further question in my mind :p
     
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  10. spinkao

    spinkao New Member

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    It was probably because you did not stomp on the brakes hard enough. I tried it out, along with the other emergency procedures with my 08, and I can confirm that:

    1) If you stomp on the gas and then apply brakes mildly, they would fight the engine but the car would still accelerate

    2) if you stomp on the brakes harder, the engine would cut off and friction brakes would engage, bringing the car to a rapid stop

    3) if you select neutral with the gas floored, the engine would cut off and the car would coast; the friction brakes work as usual, there is no regen

    4) if you hold the power button for 3 sec while flooring the gas, the car would shut down, but the friction brakes still work, albeit with no power assist. But they are still more than capable to bring the car to a rapid stop if you step on the brake pedal hardly.

    So I can confirm that all these procedures work as advertised, backed with my own experiments.
     
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  11. David Beale

    David Beale Senior Member

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    As already posted by hobbit, if you depress the brake pedal first, then the accelerator, the engine will rev. to about 2000 RPM and you will "force charge" the traction battery. I tried this twice today at red lights. First time I got 1888 RPM (thought there was some error on the Scangauge). Second time I got 1976 RPM.

    If you floor the gas pedal, then press the brakes, first the brakes will fight the power system without reducing power, but if you press hard enough the hydraulic pressure will trigger a sensor that will reduce power (and you will stop very fast!). Note that most drivers don't realize how hard you can press the brake pedal and how fast a car can stop! Remember, you are letting the anti-lock system control the car's tire slip (to almost but not quite zero).

    Try it if you must, but first ensure you have no loose items in the car and that all passengers (and the driver) are securely belted in! Also, only do so on a -deserted- road!

    The speed of the car is not a factor in this braking/throttle interaction.
     
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