Toyota's runaway-car worries may not stop at floor mats-LA TIMES

yes yes, this I knew. I just was curious what would happened if the smart keys got thrown out the window...I mean, obviously being minus your keys is preferable to being dead

 

thats what i tried to say.Another way is to put your head between your legs and kiss your but good by.
I tried hitting the brakes and putting it in neutral and it works

 

For the runaway lexus'es, I came across this article today in the Detroit Free Press: http://www.freep.com/apps/pbcs.dll/...t-being-frank-on-problem&template=fullarticle


""There is no possibility of the pedal interference with the all-weather floor mat if it's placed properly and secured," the automaker told regulators in April 2007.

But by August, federal regulators had found 12 deaths linked to the mats. A survey of 600 Lexus owners found 59 reporting sudden or unexpected acceleration. NHTSA also found evidence that in some crashes, owners were standing on the brakes yet unable to stop their vehicles. Toyota issued its first recall in September 2007 covering 55,000 vehicles.

NHTSA began testing some of Toyota's claims about the problem. It found that the brakes in the Lexus ES350 sedan could stop an engine at wide-open throttle -- but only after 1,000 feet, and only with five times the amount of pressure usually needed to bring the car to a halt."

 

You're telling me that braking performance is affected by a WOT? No wai! (And note how that paragraph implies that Toyota was lying, but the article never actually states what Toyota claimed the braking performance would be.. gotta love the Detroit press)

In seriousness, though, this issue does raise some good questions. Just what is a company supposed to do if a very small fraction of their product is defective? And what if the defect is an intermittent condition?

While the article implies that Toyota was covering up a larger problem, could it be that they were really just unable to replicate it, and were throwing stuff at the wall until it stuck?

 

Well, if that intermittent problem leads to a teeny-tiny percentage of spectacular, action-news-worthy crashes, then it will get a lot of visibility and the company has to do major PR work (as Toyota is doing now).

On the other hand if it kills hundreds or thousands of people in a boring way, they can probably just overlook it.

It helps if there are other potential sources of blame - like in the SUV rollover scenario where the SUV manufacturers were blaming the tire company and vice-versa. My guess in today's particular case is that the pedal manufacturer will eat most of the blame and go bankrupt.

As others have said, the fix (which already exists in some other cars) is to have a brake/accellerator interlock which will idle the engine whenever the brake is pressed. I wouldn't be surprised if this becomes a new safety standard for any electronic pedals - it should already be, but as Nader proved, the auto manufacturers do basically nothing to improve safety until they're forced to, either by law or by public embarassment...

 

What does WOT stand for?
Even I approached the article cautiously since it is from the freep, not because I knew them to be biased, but the fact that they are associated with Detroit, hence possibly sympathetic with the competing companies... However having said that, I didn't follow up with any serious research on them.

Note that the factoid quoted above from that article concerns with braking to stop the car when the throttle was fully open. That should not be interpreted as slander on the braking performance of the car under normal circumstances. I posted that in response to a previous post that claimed that the Prius can come to a stop, presumably with not much effort, when the throttle is wide open. It was also in response to previous posts in this thread that listed strong and unrelenting brake pedal pressure as one of the ways to bring a runaway car situation under control. However, as mentioned in the article that I cited, NHTSA testing realized that that alone may not have been sufficient to safely bring the runaway cars (Lexus ES350?) to a stop.

Also, going by the number of reported runaway acceleration cases reported to the NHTSA with Toyota/Lexus cars, and that number relative to similar reported cases with other brands and historically, I think the number in Toyota's case may be concluded as statistically significant (it's a small fraction, but it still is statistically significant in context of expectation of that number).

 

WOT means 'Wide Open Throttle'.

There are a number of videos, including a good one from CR, which explains what happens but essentially when a vehicle is being floored and the brakes are applied the extra boost to give the brakes their full stopping power is supplied by the engine vacuum.

However iIf the brake is released once or twice then that boost is lost and there no longer is any vacuum from the engine to draw from so the brakes lose much of their stopping power. This is true of all modern vehicles.

The solution is simple. The Germans are doing it and right now Toyota is implementing it; a brake override. When the brake is hit the input from the pedal/throttle to the engine is stopped. Therefore the engine is no longer at WOT. Except for a couple of German-designed Chrysler models no other maker in the US except Toyota is implementing brake override technology yet...but they certainly will be in the future.

 

The brake override does seem to be the way to go.

I hope that for the current situation with Toyota, the courts do not implicate the company of any wrongdoing. It would put a damper/doubts on my current ownership experience with the Prius.

 

Without the equivalent of an Event Data Recorder in the car (and that can survive a crash), it's hard to say what actually happened in the car. Whether the driver panicked, the shutoff system failed, the brake boost vanished, or the driver simply did not respond for 4 seconds or more, by which time it was going too fast or too high on the torque curve for the brake to be effective.

I think the driver's apparent failure to respond is understandable, if that's what it was. This is a very unusual situation, and the cognitive load to guide the car multiplied by the second.

What perhaps a "panic button" could do is limit engine torque based on cylinder shutoff, if the driver signals the presence of a serious fault in the powertrain.

 

I think something we from Detroit actually bring to a discussion like this, in addition to again being flame bait, is in some cases actual knowledge of how some of these systems work and the potential variations in their designs. When I worked for one of the US OEMs I designed the electronics and participated in the safety design for their first electronic throttle system to be deployed.

The Prius is an electronic throttle car, as is the Lexus in question. You as the driver would never know, without monitoring the throttle itself, if the throttle is actually at WOT. All you would know is that you have the accelerator fully depressed.

There seem to be two types of events under discussion. One is that the pedal sticks open, either due to stiffness in the pivot or mats blocking the pedal. In either case, the driver will press the accel and the car will accelerate normally in accordance with the demand. What it won't do is slow down when the driver releases the pedal, because the pedal was stuck. This can happen to cars that do not have electronic throttle, as well as ETC cars.

The second is that the driver may or may not have depressed the pedal, the car on its own accelerates at an undesired rate. In this case the acceleration was greater than demand, and the throttle was moved more than the driver requested. This is something that can mainly happen to ETC cars. The problem can be in the pedal, the ETC electronics, the vehicle networking, the powertrain or engine control, or in the motorized throttle itself. It could also be with the driver, unintentionally overpressing the pedal or by mistake stomping the accel rather than the brake, especially in one-footed driving.

Neither case is simple. I think that for Toyota to have come up with any solution so soon is amazing, because there was barely time for the fault analysis to be verified. Either Toyota has been working to resolve this problem for perhaps a year, the solution they are implementing is a lucky solution, or it is a partial solution.

 

It should not have mattered how long he waited to hit the brakes - if the brakes had been hit firmly once the car would have eventually stopped even at over 100mph. Had the brakes been pumped and vacuum assist lost, then it's likely stopping using the brakes alone would have been very difficult if not impossible.

As far as brake/throttle overrides go - I hope there is some sort of delay or smooth reduction in throttle applied over a couple of seconds. There are some rare occasions where it is useful to apply both the brake and throttle at the same time.

 

Your comment goes contrary to the content I cited in my post on the previous page. It goes: "...NHTSA also found evidence that in some crashes, owners were standing on the brakes yet unable to stop their vehicles. Toyota issued its first recall in September 2007 covering 55,000 vehicles.

NHTSA began testing some of Toyota's claims about the problem. It found that the brakes in the Lexus ES350 sedan could stop an engine at wide-open throttle -- but only after 1,000 feet, and only with five times the amount of pressure usually needed to bring the car to a halt."

Btw, I am curious to know what those rare occasions for stepping on both gas/brake pedals are? Is charging the HV battery one of them?

 

This is true of *many* modern vehicles. The most modern, such as the Prius, use an electrically driven boost pump, so engine vacuum is not part of the equation.

Tom

 

No, it doesn't. The people who were standing on the brakes and unable to stop the vehicle had likely pumped the pedal (probably a common response to the car not stopping as quickly as expected).

No, it's often useful to apply the brake and accelerator in certain types of slippery conditions.

 

But then, what about the NHTSA test result? I suppose they might have conducted the test properly, without pumping the brake pedal.

 

This isn't a "one size fits all" topic. There is a lot of difference between stopping a 76 hp engine and a 500 hp engine. Imagine the brakes you would need to stop a locomotive if the engine were wide open.

Seriously, let's all think about this stuff just a tiny bit before we flame each other. This is a case where there are a lot of variables: engine size, brake size and type, type of boost system, driver's response, driver's strength, and car speed.

Tom

 

What isn't said in these 'reports' is whether the operator stepped on the brake and held it down without any letup..OR..whether the operator stepped on the brake, let up and lost vacuum boost, then stepped on the brakes again with full force but no vacuum boost. In the latter case at WOT it's almost impossible to stop the vehicle. This minor but critical detail is never reported.

Again, with or without vacuum boost? It makes a huge difference.

 

Tom,
I am not flaming anyone, nor do I think the other guy was. I also take your point of engine sizes - no argument there, but note, my citation and discussion are centered on the Lexus ES 350, right from the start! The facts we present tend to get lost as the thread progresses. So I just want to reaffirm my presentation.

 

:welcome:

 

Does anyone feel that the sticky pedal is in other Toyota vehicles that it might be the same problem in the Prius and not the floor mats. I still don't understand the floor mats got caught under the floor mat. My mats are held in place by a clip on the floor. Many of the same technologies are used in many other vehicles in the Toyota line. Just my thoughts.