![]() |
|
|
|
Registered
Join Date: Jul 2000
Location: So. Calif.
Posts: 19,910
|
Quote:
S |
||
![]() |
|
Registered
Join Date: May 2002
Location: Portland, Oregon
Posts: 12,667
|
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.
__________________
Harry 1970 VW Sunroof Bus - "The Magic Bus" 1971 Jaguar XKE 2+2 V12 Coupe - {insert name here} 1973.5 911T Targa - "Smokey" 2020 MB E350 4Matic |
||
![]() |
|
Registered
Join Date: May 2002
Location: Portland, Oregon
Posts: 12,667
|
Quote:
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.
__________________
Harry 1970 VW Sunroof Bus - "The Magic Bus" 1971 Jaguar XKE 2+2 V12 Coupe - {insert name here} 1973.5 911T Targa - "Smokey" 2020 MB E350 4Matic Last edited by HarryD; 02-03-2010 at 05:10 PM.. |
||
![]() |
|
Registered
Join Date: Sep 2009
Location: North of You
Posts: 9,160
|
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. Last edited by 1990C4S; 02-03-2010 at 06:00 PM.. |
||
![]() |
|
Registered
Join Date: Jul 2000
Location: So. Calif.
Posts: 19,910
|
I wrote:
"Maybe shot peening might qualify as a surface treatment related to the above discussion." Quote:
"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 |
||
![]() |
|
Registered
|
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!
__________________
1979 911 SC Silver 2002 996 race car 2005 Ford Excursion Last edited by TechnoViking; 02-04-2010 at 05:39 AM.. Reason: error |
||
![]() |
|
Cars & Coffee Killer
Join Date: Sep 2004
Location: State of Failure
Posts: 32,246
|
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.
__________________
Some Porsches long ago...then a wankle... 5 liters of VVT fury now -Chris "There is freedom in risk, just as there is oppression in security." |
||
![]() |
|
Get off my lawn!
|
Quote:
It sounds like they designed a real trap for the driver.
__________________
Glen 49 Year member of the Porsche Club of America 1985 911 Carrera; 2017 Macan 1986 El Camino with Fuel Injected 350 Crate Engine My Motto: I will never be too old to have a happy childhood! |
||
![]() |
|
Registered
Join Date: May 2002
Location: Portland, Oregon
Posts: 12,667
|
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.
__________________
Harry 1970 VW Sunroof Bus - "The Magic Bus" 1971 Jaguar XKE 2+2 V12 Coupe - {insert name here} 1973.5 911T Targa - "Smokey" 2020 MB E350 4Matic |
||
![]() |
|
Cars & Coffee Killer
Join Date: Sep 2004
Location: State of Failure
Posts: 32,246
|
Quote:
For the cars that have all of the "features" listed above, the driver/passengers are screwed.
__________________
Some Porsches long ago...then a wankle... 5 liters of VVT fury now -Chris "There is freedom in risk, just as there is oppression in security." |
||
![]() |
|
Family Values
Join Date: Jun 2003
Location: Los Angeles, CA
Posts: 4,075
|
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.
__________________
- Joe Necessity is the plea for every infringement of human freedom. It is the argument of tyrants; it is the creed of slaves. - William Pitt |
||
![]() |
|
Cars & Coffee Killer
Join Date: Sep 2004
Location: State of Failure
Posts: 32,246
|
Quote:
Quote:
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.
__________________
Some Porsches long ago...then a wankle... 5 liters of VVT fury now -Chris "There is freedom in risk, just as there is oppression in security." |
||
![]() |
|
![]() |
Registered
|
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. 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.
__________________
1989 3.2 Carrera coupe; 1988 Westy Vanagon, Zetec; 1986 E28 M30; 1994 W124; 2004 S211 What? Uh . . . “he” and “him”? |
||
![]() |
|
Registered
Join Date: Jan 2005
Location: Minneapolis
Posts: 7,482
|
|||
![]() |
|
Registered
Join Date: Jan 2005
Location: Minneapolis
Posts: 7,482
|
Quote:
Transportation Department Opens Probe Into Brake Problems in 2010 Toyota Prius Models - Auto - FOXNews.com |
||
![]() |
|
Registered
|
Quote:
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.
__________________
1989 3.2 Carrera coupe; 1988 Westy Vanagon, Zetec; 1986 E28 M30; 1994 W124; 2004 S211 What? Uh . . . “he” and “him”? |
||
![]() |
|
Banned
Join Date: Sep 2006
Location: South of Heaven
Posts: 21,159
|
Quote:
Ever. Quote:
You CANNOT lock your steering with the car in drive. |
||
![]() |
|
Registered
|
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.
__________________
1989 3.2 Carrera coupe; 1988 Westy Vanagon, Zetec; 1986 E28 M30; 1994 W124; 2004 S211 What? Uh . . . “he” and “him”? |
||
![]() |
|
Registered
Join Date: Jul 2000
Location: So. Calif.
Posts: 19,910
|
Quote:
Sherwood |
||
![]() |
|
Registered
Join Date: Jan 2005
Location: Minneapolis
Posts: 7,482
|
Consumer Reports had a video of an Avalon braking to a stop under full throttle.
|
||
![]() |
|