[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.

[_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.

[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.

[Sxotty]

Originally Posted by 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.

That is silly Mize.

The number of people I know who have driven off with their emergency brake engaged is quite large. Engines can easily over come an emergency brake. The hydraulic brakes are another matter. And I agree with the user error comment until further information comes to light.

edit: Sorry I see that horse was severely beaten already.
BTW my drivers ed teacher said he put a coat hangar into the e-brake release for one of those foot ones so he could actually use it in an emergency instead of just have it on/off. That seemed a bit overkill to me. I mean if you have to use it, use it all the way. Still a handle lever one is much nicer for having fun with even if you dont have a FWD. I remember when I practiced sliding into a parallel parking spot with the E-brake it was entertaining and it allows you to go slower in your stupidity.

[Cheezdoodles]

Originally Posted by Sxotty

Still a handle lever one is much nicer for having fun with even if you dont have a FWD. I remember when I practiced sliding into a parallel parking spot with the E-brake it was entertaining and it allows you to go slower in your stupidity.

Whats the point of using your e-brake unless your driving a FWD?

Using e-brake to slide an RWD car would just be stupid. Just learn how to drive a RWD properly, and you can easily control oversteer by throttle control. Safer, faster, funnier, everything.

Using an e-brake to slide is just dangerous, completely locks your wheels. Just using physics to your advantage is much more rewarding and a 100 times safer

[ShootMyMonkey]

Originally Posted by Ostepop

Whats the point of using your e-brake unless your driving a FWD?

For that matter, using the e-brake isn't 100% necessary to get a slide even on FWD. Usually involves something that makes the rear slide more easily than the front, which can include some suspension tuning, some braking bias, and/or simply lower tire pressure in the rear than the front. It would also typically involve some hard left-foot braking and disabling any existing ABS.

The rear also breaks easily on some FWD cars simply because they have such an extreme forward weight bias that with some basic weight shifting from a strong feint, you could almost lose rear traction just from the weight shift.

[sham63]

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.

The emergency brake be overcome. When I was selling my old 95 Saturn SL2 the buyer accidently left the emergency brake engaged and starting driving. After getting down the street he commented about the lack of power. I noticed the brake was on. Boy was there a lot of smoke!!!! After it was released he liked the car better. This car had 124 hp, and over 130k miles on it. So it doesn't a lot of hp to overpower the emergency brake.

Jim

[Cheezdoodles]

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.

Um.. Are mechanical brake\ emergency brake the same thing as parkingbrake\handbrake?

I have driven around with the hand brake on in my merc for short periods several times by accident. I didn't notice anything except for the dash starting to blink red and telling my i was doing something stupid. The car pulled pretty much as good as it allways pulls.

I dont think these brakes are very powerful, nor do you need a lot of hp tourque. 90% of the time i did this in the merc, i was backing out of parking lots..

Hell, even our old S70 volvo would overcome the handbrake.

A m8 of mine "borrowed" his moms Ford Focus when we where 15-16 (you need to be 18 to get a driving licence in norway) and we drove like 2-3km with the emergency brake on. That focus probably didn't have more than 100hp... We didn't really notice anything (except that the car was rather slow)

[Simon F]

Originally Posted by Ostepop

I have driven around with the hand brake on in my merc for short periods several times by accident. I didn't notice anything except ....

What? You didn't notice a hot/burning smell?

As for the engine overcoming the handbrake, it's "trivial" in our Renault Scenic. You just drive off and the handbrake releases automatically. It took some getting used to at first but I quite like it now.

[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.

[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

[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.

[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

[_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.