How did a single part made by a single supplier screw the world's biggest automaker?

[911pcars]

Originally Posted by HarryD

Reduce Surface tension?

What kind of BS explaination is that! Metals (or any solid for that matter) do not exhibit Surface Tension.

From Wikipedia: "Surface tension is a property of the surface of a liquid. It is what causes the surface portion of liquid to be attracted to another surface, such as that of another portion of liquid"

They speak with forked tounge.

They just need to update the dilithium crystals and replace the blinker fuild.

Hmmmmm. Maybe shot peening might qualify as a surface treatment related to the above discussion.

S

[HarryD]

Sherwood,

Shot peening modifies the surface of the metal tp make the piece more resistant to cycle failure. Totally different topic.

I still think they need to replace the dilithium crystals.

[HarryD]

Originally Posted by 1990C4S

It still eludes me. And I've back to the other link you posted and looked at the real part. I doubt this is by accident. It is designed to 'supply information' but not tell us much.



I believe his problem is different, I thought he said he has a problem with his Prius (not subject to recall) and he can cause the problem to occur any time he wants. But Toyota is ignoring him. Allegedly.



I can't imagine that measuring the clearance and installing the appropriate shim for a new 'field fix' is in the manual. If it is someone just won the clairvoyant award.

Does anyone know for sure if there is a software update?

Interesting reading: http://www.thetruthaboutcars.com/ttac-does-the-toyota-pedal-shim-fix-temporary-solution-at-best/

http://www.thetruthaboutcars.com/toyota-recall-includes-computer-reflash-trimming-gas-pedals/

Like I said, there is more to this story.

[1990C4S]

The conclusion of the report is hard to disagree with:

The shim’s effect on reducing the amount of friction will presumably slow down the wear process, but intrinsically, this is not a permanent fix to a very critical part, from a safety point of view. This is why the CTS-type pedal design is flawed, because it is subject to changes in the amount of friction it generates due to wear and other factors.

The only other explanation for the varying gap size and different shims is that the manufacturing tolerances are so great, that this is necessary to compensate for them. That’s that hard to imagine, for such a critical part. But if so, it raises other serious questions about this unit. Either way, it reinforces our position that Toyota needs to replace all the CTS pedals with Denso pedals or another proven pedal design, as soon as they are available.

I am at a loss to understand how this will work long term. I think the next issue will be pedals being to easy to push. The plastic friction material will wear and the plate will prevent the spring from moving the pivot arm.

I see this fix as stage 1, getting cars on the road. I don't think the final shoe has dropped.

[911pcars]

I wrote:
"Maybe shot peening might qualify as a surface treatment related to the above discussion."

Originally Posted by HarryD

Shot peening modifies the surface of the metal tp make the piece more resistant to cycle failure. Totally different topic.......

According to Wiki:
"Shot peening is a process used to produce a compressive residual stress layer....."
Shot peening - Wikipedia, the free encyclopedia

Not entirely related to this thread, but FWIW.

But thanks for the links that provide more detail about Toyota's pedal fix. I was relying on the previous illustrations to detail the fix. Your link describes the link in much greater detail.

Sherwood

[TechnoViking]

Hold the press, folks:

http://www.cnn.com/2010/WORLD/asiapcf/02/04/japan.prius.complaints/index.html?hpt=T1

Now it's SOFTWARE?

They really are looking more incompetent every day.

Edit: Nevermind...I guess that's a separate issue!

[legion]

From what it sounds like on the recalled Toyotas, there are several problems:

1) The pedals can wear and stick.
2) The floor mats can keep the pedals depressed.
3) The drive-by-wire software can make the vehicles accelerate unexpectedly.

Add to that:

1) The cars cannot be shifted into neutral when they are far enough off of idle (like when the car is accelerating uncontrollably).
2) It takes three seconds of holding down the ignition button to turn off the engine.
3) The brakes cannot overpower the engine.

So you have multiple causes of unintended acceleration, and once it happens, the car is designed in such a way there is little you can do about it.

As a software guy, it is VERY EASY to write software that has a simple flaw that only happens in extremely rare circumstances--such as a variable overflow.

[GH85Carrera]

Originally Posted by legion

From what it sounds like on the recalled Toyotas, there are several problems:

1) The pedals can wear and stick.
2) The floor mats can keep the pedals depressed.
3) The drive-by-wire software can make the vehicles accelerate unexpectedly.

Add to that:

1) The cars cannot be shifted into neutral when they are far enough off of idle (like when the car is accelerating uncontrollably).
2) It takes three seconds of holding down the ignition button to turn off the engine.
3) The brakes cannot overpower the engine.

So you have multiple causes of unintended acceleration, and once it happens, the car is designed in such a way there is little you can do about it.

As a software guy, it is VERY EASY to write software that has a simple flaw that only happens in extremely rare circumstances--such as a variable overflow.

Wow, I did not know you could not shift into neutral when they are far enough off of idle (like when the car is accelerating uncontrollably).

It sounds like they designed a real trap for the driver.

[HarryD]

Overheard in the halls of Toyota enginnering:

--------------------------------------------------------------------------------
Endo: What the hell you need ball bearings for?
Watanabe: Awww, come on guys, it's so simple. Maybe you need a refresher course. [leans arm on hot engine part]
Watanabe: Hey! It's all ball bearings nowadays. Now you prepare that Fetzer valve with some 3-in-1 oil and some gauze pads. And I'm gonna need 'bout ten quarts of anti-freeze, preferably Prestone. No, no make that Quaker State.

[legion]

Originally Posted by GH85Carrera

Wow, I did not know you could not shift into neutral when they are far enough off of idle (like when the car is accelerating uncontrollably).

It sounds like they designed a real trap for the driver.

I'm not sure what features apply to what models. I don't think all of the recalls are for drive-by-wire cars, and I don't know that all of them have the neutral lockout.

For the cars that have all of the "features" listed above, the driver/passengers are screwed.

[KaptKaos]

I am a little late to this party. I was thinking about this and came up with some questions. I don't know if these have been posed already so forgive me if I am redundant.

1) Does the use of a starter button versus an old style key make it harder or easier to shut off a car?
2) Does the throttle by wire, instead of a traditional and effective accelerator cable, contribute to the likelihood of this happening or happening in the future?
3) Specific to the Prius: I assume, maybe wrongly, that the brakes are traditional hydraulic disc/disc or disc/drum. Is this correct? If not, are they a brake by wire design?
4) Legion noted that the drivers could not shift to neutral after a certain RPM. Is that confirmed? If so, I assume that means there is no direct connection to the transmission via traditional linkage.

Thanks for your help with this.

[legion]

Originally Posted by KaptKaos

1) Does the use of a starter button versus an old style key make it harder or easier to shut off a car?

Definitely harder IMO. Holding a button for three seconds while trying to control an accelerating car is harder than turning the key (which can be done in under a second).

Originally Posted by KaptKaos

2) Does the throttle by wire, instead of a traditional and effective accelerator cable, contribute to the likelihood of this happening or happening in the future?

There is no "interpretation" between the driver's foot and the throttle on a traditional system. My Silverado is DBW, and I have had to adapt my driving style, as I would previously press the pedal down very fast to 1/4, 1/2 or 3/4 throttle. I my truck's DBW system, it anticipates that I am going to go all the way to the floor (even though I don't) and goes WOT fairly early in the motion. Similarly, when I pull my foot off the gas rapidly, it will lock the torque converter to help in braking antipating a panic stop. (Engine braking on an automatic IS a nice feature though.)

I've never had any problems with the Chevy DBW system, and it has been in production (starting with the Corvette) for almost 15 years.

That said, there is a HUGE potential for problems with a DBW system, as the programmer must thoroughly test it in all situations. Maybe missing input from a sensor can cause the system to think something is going on that is not? Maybe a certain variable can overflow and cause unexpected results? There's a lot more to consider than with a direct linkage.

[jyl]

On what car can the brakes not overpower the engine? You'll have to show me this.

I didn't realize Toyota made drag racers. That's the only type of car I can think of, where the brakes can't overpower the engine.

Originally Posted by legion

From what it sounds like on the recalled Toyotas, there are several problems:

3) The brakes cannot overpower the engine.

The Prius was mentioned elsewhere in the thread. There is a separate issue with that model, which has to do w/ the ABS system. When braking on a road that has very sharp bumps, some report a momentary reduction in apparent braking. It appears that what is happening is, when the wheel bounces on the bump, traction is momentarily reduced, the ABS system detects impending lockup, and momentarily reduces braking, then applies braking again. It happens fast enough to have no impact on actual braking distance, but some people claim to be able to feel it. I've never actually experienced this myself (45K miles on our Prius) but that is what I'm reading. I've also read that Toyota has tweaked the ABS system to be less aggressive in preventing lockup.

[kaisen]

Toyota dealer shows us fix for sticking accelerator pedals — Autoblog

Interesting

[kaisen]

Originally Posted by jyl

The Prius was mentioned elsewhere in the thread. There is a separate issue with that model, which has to do w/ the ABS system. When braking on a road that has very sharp bumps, some report a momentary reduction in apparent braking. It appears that what is happening is, when the wheel bounces on the bump, traction is momentarily reduced, the ABS system detects impending lockup, and momentarily reduces braking, then applies braking again. It happens fast enough to have no impact on actual braking distance, but some people claim to be able to feel it. I've never actually experienced this myself (45K miles on our Prius) but that is what I'm reading. I've also read that Toyota has tweaked the ABS system to be less aggressive in preventing lockup.

Toyota admits Prius had a braking problem *UPDATED — Autoblog

Transportation Department Opens Probe Into Brake Problems in 2010 Toyota Prius Models - Auto - FOXNews.com

[jyl]

Originally Posted by KaptKaos

I am a little late to this party. I was thinking about this and came up with some questions. I don't know if these have been posed already so forgive me if I am redundant.

1) Does the use of a starter button versus an old style key make it harder or easier to shut off a car?
2) Does the throttle by wire, instead of a traditional and effective accelerator cable, contribute to the likelihood of this happening or happening in the future?
3) Specific to the Prius: I assume, maybe wrongly, that the brakes are traditional hydraulic disc/disc or disc/drum. Is this correct? If not, are they a brake by wire design?
4) Legion noted that the drivers could not shift to neutral after a certain RPM. Is that confirmed? If so, I assume that means there is no direct connection to the transmission via traditional linkage.

Thanks for your help with this.

1) You usually have to hold down the POWER button for a couple of second to shut down a car so equipped. Then again, with the old-style key-in-the column, when you turn the key to shut off the car you can easily turn it one notch farther and engage the steering lock - now you have shut off the engine but you can't steer.
2) Traditional throttle cable/linkages can get stuck at WOT, some of us who have been driving cars for decades have experienced that. Are the traditional systems more or less prone to problems than the drive-by-wire systems? I don't know, in either case the frequency of such events is miniscule.
3) The Prius is a brake-by-wire system with a mechanical failsafe. When the brake pedal is depressed lightly, the electric motors provide the braking via regeneration. When the pedal is depressed harder, the friction brakes (disk/drum) provide the braking. The fail-safe is that if the braking circuitry fails, the pedal actuates the friction brakes directly. See detailed description below.
4) I don't know about other Toyota models. In the Prius you can shift to N at speed. Sometimes people think that will save gas, but it doesn't actually save gas.

Here is a pretty detailed explanation:

The Prius is a dual-circuit braking system. It's basically 'brake-by-wire' except that hydraulic fluid and pressure sensors are used to provide the input, rather than electrical position sensors as in the 'drive-by-wire' accelerator.

In normal use, the hydraulic lines from the master brake cylinder go only to a 'stroke simulator' - a piston that permits the brake pedal to move and provides braking feel. The master cylinder pressure sensors, PMC1 and PMC2, measure the driver's braking pressure. SMC1 and SMC2 are closed, so for the moment ignore the lines leading from there to the wheel cylinders.

The Skid Control ECU takes those sensor values and computes how much braking force to apply to each wheel. It asks the HV ECU to provide as much of the braking force to the front wheels as possible through regeneration, and the HV ECU reports back how much it achieved (this is done via CAN). The Skid Control ECU then distributes the remaining braking force required across the friction brakes, turning on the SLAxx solenoid valve for each wheel to Apply the brake further (increase pressure) and the SLRxx valve to Release the brake (decrease pressure). For example, SLAFL and SLRFL control the Front Left wheel and SLARR and SLRRR control the Rear Right. It monitors the pressure achieved with each wheel's Pxx sensor (PFL, PFR, PRL, PRR).

Pressure changes are achieved by having a chamber (accumulator) that stores fluid at high pressure. When an Apply valve is opened, the high pressure fluid flows to the lower-pressure wheel cylinder, applying the brake. The Accumulator Pressure Sensor (PACC) measures the pressure in the cylinder so the ECU can decide when to run the pump motor, to keep the accumulator pressurised.

The reason that hydraulics are used in the sensing side is so that in fail-safe conditions, the master cylinder is connected to some wheel cylinders, operating them directly from pedal force. This is where the Skid Control ECU cannot operate the brakes for some reason. Two valves that normally stay closed, SMC1 and SMC2, open, and the stroke simulator is closed off (valve SCSS). Instead of moving a piston in the stroke simulator, pedal input now directly controls the front wheel cylinders.

There is also an electrical brake pedal stroke sensor (a potentiometer), which is used to determine how fast the pedal is being applied. If the ECU detects a fast application it does Brake Assist, where it actually applies more force than the driver's pedal pressure indicates. It's been found that in emergencies, drivers tend to brake sharply but not actually hard enough.

[m21sniper]

Originally Posted by jyl

On what car can the brakes not overpower the engine? You'll have to show me this.

Any muscle car ever made.

Ever.

Originally Posted by jyl

1) You usually have to hold down the POWER button for a couple of second to shut down a car so equipped. Then again, with the old-style key-in-the column, when you turn the key to shut off the car you can easily turn it one notch farther and engage the steering lock - now you have shut off the engine but you can't steer.

This is simply not true on the vast majority of cars automatic around.

You CANNOT lock your steering with the car in drive.

[jyl]

Originally Posted by kaisen

Toyota admits Prius had a braking problem *UPDATED — Autoblog

Transportation Department Opens Probe Into Brake Problems in 2010 Toyota Prius Models - Auto - FOXNews.com

I've occasionally felt the transition between regenerative and friction braking. It lasts far less than one second - if you try saying "one second", the transition (when I can feel it) is over before you start on the "n" in "one". It is really momentary. But, in my experience, it is not associated with a bumpy surface. So I don't think it is the same as the ABS kicking out and in, that I mentioned.

[911pcars]

Originally Posted by jyl

On what car can the brakes not overpower the engine? You'll have to show me this.

I didn't realize Toyota made drag racers. That's the only type of car I can think of, where the brakes can't overpower the engine. ...........

Has anyone tried this? Countermeasure results from full throttle at 20-35 mph is not the same at 70 mph. I think it would take quite a bit of effort to reduce or negate vehicle velocity while the engine continues to produce max. vehicle speed. And this assumes the vehicle brakes are up to the task w/o overheating. Any youtube videos that demonstrate this maneuver?

Sherwood

[kaisen]

Originally Posted by 911pcars

Has anyone tried this? Any youtube videos that demonstrate this maneuver?

Sherwood

Consumer Reports had a video of an Avalon braking to a stop under full throttle.