Has anyone figured out how unscheduled acceleration apparently can result in some cases to the brakes failing to slow the car down? This may or may not relate to the 2010 Prius. I thought that heavy brake application would slow and override a stuck acceleration but I'm beginning to think otherwise and I am not clear if this is a smart thing to go out and test on a stretch of road. Is it known for certain that you can or cannot override acceleration? Maybe there is a speed threshold where below and you can slow but above it is impossible? What about the driver who claims that Neutral didn't slow her car down even? It almost seems like holding the start button in while applying the brakes is about all you can do? Does anyone really figure there might be something electronic going on where you get unscheduled acceleration with no gear selection to neutral possible and on top of that brake failure? At this point I have to chauk up the multiple problems to driver error/panic. That doesn't mean I want to be in any of their shoes. I just want to know the truth. I don't feel confident Toyota, NHTSA, or Congress knows the truth yet.
Hi Susan, This is a technical forum, not an opinion forum. So the obvious question back: How do you propose to find the truth? Check the message archives and you will find many of us have performed the experiments. You can do the same thing we have done. That is the difference between spreading Fear, Uncertainty and Doubt versus doing the experiment. If you really want the answer, fly to Huntsville Alabama. I'll pick you up at the airport and you can observe what happens. But it would be cheaper for you to do the experiments yourself. Now many of us know how to analyze circuits and circuit boards but your question presumes we have: circuit board(s) schematics test setup to do an analysis interest time The answer to your question begins with study, learning the skills of an electronic technician and conducting experiments and investigation. It is also helpful to have the maintenance manual: "2010 Prius Repair Manual, Volume 2" RM1291U2, pp. CC-1 to CC-249 Are you bringing some experimental data or research from the maintenance manual? If so, please post what you have. Better still, is your curiosity enough to lead you to learning the skills of an electronic technician and get parts to analyze? "You're either part of the solution or you're part of the problem." Eldridge Cleaver. Asking a question is easy ... using the question to learn how to find the answer is harder. Are you ready? Bob Wilson
First, the brake "problem" did not include acceleration. It feels like the car suddenly accelerates, but that is just human perception. When you suddenly drop deceleration to zero it feels to us like you accelerate. You don't. Second, as stated elsewhere, the -sure- way to disconnect the drive to the wheels is to press "P". If you are not moving the car will lock the drive train. If you -are- moving the car will beep and switch to "N" with -no- delay. It will not over-rev, it will not explode, the world will not end, you will not loose power steering or brakes. If you'd rather believe untrained vehicle operators who are apparently, easily confused, then you are in for a bad life!
What is the highest speed that you are likely to drive? Go find an empty stretch of road, accelerate up to that speed, floor the accelerator with your right foot, and stab the brake with your left foot. See how long it takes you to stop while holding the accelerator pedal down. Carolyn did this from approximately 70 mph. I did this with my car last night from about 40 mph just to verify, because someone in another thread was claiming that his 2007 did not work. My car comes to a dead halt within 3 seconds from 40 mph with the accel pedal held down.
It's gamma rays from the planet Mongo, I tell you. The Mongonian warrior chieftains are laughing their asses off watching us run in tiny circles over this. . _H*
It does take some coordination to use the left foot to brake if you aren't used to it. (I'm not a left foot braker since I learned to drive on a manual trans). If nothing else, if you haven't done it, you should really test once to see how effective the EBD system is. Find an empty road or parking lot and quickly and firmly apply the brakes. Make sure you don't have any loose objects in the cabin and make sure there aren't any other cars behind you. This is not your grandfather's Oldsmobile. :madgrin:
I took fuzzy's suggestion, and shifted into reverse, which really switches to neutral. This is a more natural action (neutral needs to be held, the park button is just wierd, so push joy stick up while moving to get it to neutral) to me. Note, I did have a coworker do this on a conventional rental car on a dare on the boston turnpike. The transmission just buckled. Because of the relationship with our company and hertz they drove a replacement vehicle out to him within an hour. So don't try this at home on a non prius. I am curious with those with scan gauges and gen II though. Accelleration and brakes? Is juice flowing to the motor to go forward while friction brakes are trying to stop it? What are mg1 and mg2 trying to do?
I have a Scangauge, but I wasn't looking at current. I was watching RPM - prior to braking the ICE was > 4000 rpm with the accel pedal floored, when I hit the brake, the ICE dropped below 1k within about 2 sec with the pedal still floored as the car came to a stop within 3 sec. There is some update lag when reading RPM, so it is not possible to get exact time vs. RPM with the Scangauge, but you can hear the ICE revs drop as you brake. Interestingly, after the car came to a stop, I could rev the ICE above 2k, but the brake held it stationary. Also, releasing the brake will launch the car, but it wasn't as impressive as I had hoped based on Carolyn's video.
I'm satisfied. I'll conclude under the demonstrated circumstances so far that Prius drivers who claim to be unable to stop their cars using brake alone have panicked. It is good to know that braking does overpower acceleration when all systems are working. It looks like braking disconnected the acceleration though. And that acceleration does not resume until the brake is released? So, if you have some other kind of unscheduled acceleration error (like in the ECU itself) bypassing the pedal and the acceleration is not interrupted when applying the brakes what would the story be? I think a lot different--no?
What would the story be? Fiction. We were dealing in non-fiction. We like non-fiction as you can test that. Once you get to fiction, you can argue about which would win: Star Trek's Enterprise or a Star Wars Imperial Cruiser indefinitely. Back to non-fiction. Any number of folks describe other cars where hitting the brakes does not limit the accelerator. How To Deal With Unintended Acceleration - Tech Dept. - Auto Reviews - Car and Driver You will notice that even the cars with no feature to limit the accelerator when the brakes are applied stopped fine. (personally, when I was in a Ford Aerostar with unintended acceleration, we used the brakes to stop, then shifted once stopped) The most powerful Prius has a 1.8 liter engine that only makes 98 HP, Car and Driver used examples of cars making 150 to 450 more Horse Power. So the effect in a Prius should be even less stressful, even when the Mongonian warrior chieftains shoot rays at our ECUs, or whatever story you invent.
Well, there is a stopping distance difference but not nearly what I thought. That is _great_ to know. Thank you.
Remember that if you're sitting holding the car stopped with the brake with your foot also on the go-pedal, you're force-charging. . _H*
The other day when looking for the tire pressure transducer reset and SKS button I also pushed the accelerator all the way. I was surprised to see it travel all the way to the floor carpet. I expected it to stop prior to reaching the floor. Has anyone else noticed this? Problem for anyone? Thanks.
Do you mean testing of BA (Brake Assist), not EBD? If so, and if any average size (or larger) female passengers are in the car, first make sure their shoulder belts are comfortable positioned. I unintentionally tested BA twice with the wife in the car. This brought immediate complaints of breast pain. This Prius stopped shorter than even the rental car where she accidentally hit the 'clutch' -- on an automatic transmission.
EBD = Electronic Brake Distribution - works with ABS to allow max braking force at all 4 wheels. You are also correct, the Brake Assist system also comes into play when you slam on the brakes suddenly by fully applying the brakes for you.
