[nintenho]

http://www.seattleweekly.com/2009-04...erfect-prius/4

"You get these customers that say, 'I stood on the brake with all my might and the car just kept on accelerating.' They're not stepping on the brake," says Toyota corporate spokesman Bill Kwong. "People are so under stress right now, people have so much on their minds. With pagers and cell phones and IM, people are just so busy with kids and family and boyfriends and girlfriends. So you're driving along and the next thing you know you're two miles down the road and you don't remember driving, because you're thinking about something else."

"I thought they were the coolest thing ever," James says. He and his wife Elizabeth, who teaches at an elementary school, bought their first Prius three years later.

Elizabeth survived the wreck, but her legs and back were banged up and she's still hobbled, despite a year of physical therapy. Scar tissue on her intestines requires her to drink MiraLAX for the rest of her life to ease stomach pains.

Then other horror stories rolled in.

The funniest story is of the guy who parked his Prius in his driveway, got out of his car and walked towards his house, and then saw the Prius surge forward and crash through the garage door into his Altima.

There's probably some major software issue with these cars. These accidents are a combination of unintended acceleration and unresponsive brakes. Makes me lean more towards the manual transmissions.

[Mize]

User error more likely. Remember when Audi's would accelerate wildly when the brake pedal was pushed hard during the 80s? Not one case was ever documented or proven, but Audi renamed the cars and moved the brake pedal further to the left for fat American feet. There's no car motor/engine on the planet that can overcome its mechanical brake (emergency brake) let alone the hydraulic one.

[nintenho]

Maybe, but isn't the Prius a drive-by-wire car? And the example with the car crashing into the garage can't be user error.

[Mize]

Originally Posted by nintenho

Maybe, but isn't the Prius a drive-by-wire car? And the example with the car crashing into the garage can't be user error.

So it started itself? Or it's so quiet he left it running?
Drive by wire on the brakes? There's no mechanical brake? I seriously doubt that.

There might be problems, but I'll wager no more "spontaneous acceleration" claims than Camry or Audi 6 both of which are NTHS investigation while Prius is not.

[3dilettante]

I believe Toyota hybrids are drive by wire, at least for the throttle.
Braking is something I'm not sure it applies fully to.

The transmission is an ECVT on the most modern models.
I would think setting it to park would disengage the engine and motor, but I don't know details if this requires that the control software pass that information along.

Hybrid regenerative braking does rely on the traction motor to produce a significant amount of braking force, and in cases of gentle braking, it will defer using the brake pads until the very end.
That must mean the electronics can delay the use of the brakes, but slamming on the brake pedal automatically activates the hydralic brakes.
The question is if there is a physical override, or if the electronic control system is the one passing that information along.

The reliance on the traction motor is another potential weak spot, as this allows hybrids to have brakes that are under-specced for the car.
If the traction motor is not braking, it and the gas engine can produce a lot of torque for brakes that are not meant to work solo.

[RudeCurve]

Originally Posted by Mize

There's no car motor/engine on the planet that can overcome its mechanical brake (emergency brake) let alone the hydraulic one.

Actually there are plenty of cars that can overcome its EB especially cars with lots of hp/tq.

[homerdog]

Originally Posted by RudeCurve

Actually there are plenty of cars that can overcome its EB especially cars with lots of hp/tq.

Yup, I can pretty easily overpower the EB in my truck, discovered by accident.

[3dilettante]

I think it was Mitch Hedberg who had the routine about the "emergency make my car smell funny" lever.

[nintenho]

Originally Posted by Mize

So it started itself? Or it's so quiet he left it running?
Drive by wire on the brakes? There's no mechanical brake? I seriously doubt that.

He parked the car in his driveway but left the car running. Even if he didn't switch the gear to "park", doesn't a continuously variable transmission need pressure on the gas pedal to go forward even an inch? In this case, the car actually sent enough power to the wheels to break a garage door.

[3dilettante]

I don't think that's true.
I think if the ICE is off, the motor will try to emulate the idle crawl of conventional cars.

[ShootMyMonkey]

Originally Posted by 3dilettante

I believe Toyota hybrids are drive by wire, at least for the throttle.
Braking is something I'm not sure it applies fully to.

Almost all current Toyota vehicles, hybrid or not, are drive-by-wire throttle. Some models as far back as 2003 were dbw throttle. For the most part, though, I think it's been the case since the 2006 model year. I believe this also carried over to the Toyota-made powerplants which ended up in other makes (e.g. the Corolla/Celica engines used by Lotus for the Elise/Exige).

Braking, you can consider dbw for hybrids simply because you're not really having a direct link between the pedal and whatever it is that's doing the braking, whether it's the traction motor+generator or the actual calipers/drums. Just because it has hydraulic brakes, doesn't mean it is not by-wire. Engaging of the wheel brakes is still controlled by one of the computers, and I still think that even in emergency hard braking situations where the wheel brakes are engaged immediately, you still don't actually have a direct link between the pedal and the hydraulic action.

I'm sure the e-brakes are a different story, since they're not really used in the same context as the brake pedal.

[Silent_Buddha]

My mother, at least once a week, will drive for a block or two before realizing her emergency break is still on in her BMW.

It should have been put another way, it's almost impossible to find an engine that can't overcome the emergency break. Even my old VW Diesel Rabbit from the 80's with almost no hp or torque could drive while the e-brake was on.

Regards,
SB

[Mize]

wimpy right arms! so go to your car...lay on the foot brake and tell me your 0-100 kph times

[Sonic]

Originally Posted by Mize

wimpy right arms! so go to your car...lay on the foot brake and tell me your 0-100 kph times

Have no problem believing the engine can overcome it, the transmission is a different story.

[_xxx_]

Originally Posted by nintenho

Maybe, but isn't the Prius a drive-by-wire car? And the example with the car crashing into the garage can't be user error.

Why? Downslope coupled with the guy forgetting the parking brake/handbrake would do it easily Although the gearbox should automatically switch to P when the key is pulled, if not then it's a failure.

There are no brake-by-wire cars out there besides Mercedes SL and E-class W211(till 2002, then it was switched back to regular hydraulic/mechanical brakes) models.

Thottle is "by-wire" in pretty much all cars built in the last 10-15 years.

[Captain Chickenpants]

I have never understood the term Emergency Brake. In what emergency do you use it!? In the UK we call it the handbrake, it's primary use is for initiating handbrake turns

CC

[_xxx_]

Emergency brake is when you really push the brake pedal in panic, the software assists additionally with more pressure and faster reaction. What Buddha means is the parking brake/handbrake, not emergency brake.

[Mize]

In the US they call the handbrake the emergency brake and teach (in my youth) that you use it if the hydraulic brakes fail. In reality the Captain is right, it's the Batman turns handle for FWD cars that can't drift...

[Brad Grenz]

Yeah, I think the terminology has to do with their intended use as a failsafe should a parked car get kicked out of gear. If your vehicle gets knocked in to neutral some how the emergency brake should still keep the car from moving, but it has little effect against powered movement. And there are a number of things you are taught to try when the hydrolic brakes go before trying the parking brake.

[Simon F]

Originally Posted by Captain Chickenpants

I have never understood the term Emergency Brake. In what emergency do you use it!? In the UK we call it the handbrake, it's primary use is for initiating handbrake turns
CC

Well I have certainly used the handbrake in an emergency when the foot brake on a 2 tonne, 1950's UK car which we'd been restoring failed coming up to traffic lights. Good thing the handbrake was on a long lever 'cause I needed to pull it very hard.

[homerdog]

Originally Posted by Brad Grenz

And there are a number of things you are taught to try when the hydrolic brakes go before trying the parking brake.

Such as? With an automatic transmission I don't see too many options...

[Captain Chickenpants]

Originally Posted by Simon F

Well I have certainly used the handbrake in an emergency when the foot brake on a 2 tonne, 1950's UK car which we'd been restoring failed coming up to traffic lights. Good thing the handbrake was on a long lever 'cause I needed to pull it very hard.

Wow, scary! I stand corrected!
I assume you were more careful in your restorations after that Is this why your cars now are quite lightweight?

CC

[Silent_Buddha]

Originally Posted by homerdog

Such as? With an automatic transmission I don't see too many options...

Many automatics also have an L1 and L2 setting which will engage lower gears and help slow down the car. Also while not good for the tires, putting into neutral and rubbing the curb can help. If there's no obstructions, pull the car onto grass/shrubbery can eventually slow it down.

But yes in general, at least when I was taking driving lessons a few decades ago, we were taught to use the "hand brake" in emergencies, thus why it's also called an emergency brake.

Likewise "hand brake" isn't an entirely good way to describe it, as in many older cars the emergency brake wasn't used by hand at all. It was another foot pedal generally off to in the left hand side of the foot well.

Thus, "emergency brake" is a far more universal term for what people call the "hand brake."

Regards,
SB

[homerdog]

Originally Posted by Silent_Buddha

Many automatics also have an L1 and L2 setting which will engage lower gears and help slow down the car. Also while not good for the tires, putting into neutral and rubbing the curb can help. If there's no obstructions, pull the car onto grass/shrubbery can eventually slow it down.

Ah yes, matter of fact I don't recall seeing an automatic that didn't have those settings.

Originally Posted by Silent_Buddha

Likewise "hand brake" isn't an entirely good way to describe it, as in many older cars the emergency brake wasn't used by hand at all. It was another foot pedal generally off to in the left hand side of the foot well.

Thus, "emergency brake" is a far more universal term for what people call the "hand brake."

It's a foot pedal on my 1993 Silverado, which is a better place for it IMO given most people only use it as a parking brake (at least I don't know anyone who uses it for anything else) and it's way easier to push down with your foot than pull up with your arm.

[Arwin]

Maybe it was a Prius model that has the auto-parking feature? That would make a lot more sense, whether it is user error or a programmer error.

I've never heard of something like this over here though.

Hmm, from what it sounds like after reading the article in detail, it could be a bug where the engine revs up to charge the battery, but then connects to the front axle anyway by accident, so that the engine that's supposed to only spin to charge the battery also accellerates the car. I could see how that's pretty scary, and I have no idea how you could overrule it - if it's a proper bug, then I doubt putting the engine in neutral or a different gear would have any effect at that point. Maybe by pressing the SEV button (drive electronic only, but if you accellerate above 50km/h that turns itself off automatically). That's not available on the U.S. Prius iirc - perhaps the two are related?

Or maybe just pressing the power-off button? Don't know if you can do that while the car is still moving.

The problem with snow mentioned is more well-known, I think, in that the traction control kicks in if you spin the wheels, so if you lost grip sideways while still accellerating, if the traction control kicks in at that point you'll see yourself slide out of the corner much faster (and in a straighter line) than if the wheels were still spinning.

I wouldn't rule out mechanical failure though ... if the cause is that the recharging of the battery by the gas-engine is accellerating the car, I'd reckon the flywheel or whatever is being used to connect and disconnect the drivetrain doesn't disconnect properly anymore.