thruthefence
Aerospace
Regarding the Toyota troubles currently in the news; any chance of this being a "drive-by-wire" software (or hardware) issue, as opposed to a strictly mechanical, binding throttle linkage,ect problem?
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Toyota uncontrolled throttle 6
- Thread starter thruthefence
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MacGyverS2000
Electrical
Is it just me, or does that diagram explain practically nothing of use unless you are intimately familiar with how the entire mechanism works int he first place?
Dan - Owner
Dan - Owner
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GregLocock
Automotive
Bit of a bummer when your design works somewhere between 99.99 and 99.999% of the time and you still cop flak over it!
Cheers
Greg Locock
I rarely exceed 1.79 x 10^12 furlongs per fortnight
Cheers
Greg Locock
I rarely exceed 1.79 x 10^12 furlongs per fortnight
ChrisDuncan
Mechanical
""Bit of a bummer when your design works somewhere between 99.99 and 99.999% of the time""
It's probably a bit higher ratio than that considering only 20 or so fatal accidents.
I think that's part of why it took them so long to come up with a fix, trying to duplicate or surmise the problem.
DBW is better than cable from a manufacturing standpoint due to the fact it eliminates air bypass systems. Most cable throttle EFI cars have at least one, some have 2. One for loads, one for cold start. The DBW throttle body handles both the normal throttle function and load/cold-start air flow adjustments to maintain steady idle.
The automatics with optional "manual" paddle shifters have a more complex gated console shifter, if it's in the paddle mode you have to move it over and up to get to neutral. Maybe this should be re-thought to go back to the one movement to neutral.
Still think shifting to neutral is the best thing to do, it's easier to locate and slam the shifter up, most won't go to reverse without the release button. Easier than finding and turning the key and you don't lose your power steering/brakes. It should be part of every defensive driving course. Everyone that drives a DBW vehicle should practice in a parking lot.
You don't have to worry about hurting the engine, all DBW cars are rev limited and most are rev limited to 4,000rpm when the shifter is in neutral.
Maybe a kill switch system if you're going to use the complex remote keys, sort of like a dirt bike, only one easy access fool proof switch, all it does is kill the engine. But then you have to train drivers to drive without PS, PB.
It's probably a bit higher ratio than that considering only 20 or so fatal accidents.
I think that's part of why it took them so long to come up with a fix, trying to duplicate or surmise the problem.
DBW is better than cable from a manufacturing standpoint due to the fact it eliminates air bypass systems. Most cable throttle EFI cars have at least one, some have 2. One for loads, one for cold start. The DBW throttle body handles both the normal throttle function and load/cold-start air flow adjustments to maintain steady idle.
The automatics with optional "manual" paddle shifters have a more complex gated console shifter, if it's in the paddle mode you have to move it over and up to get to neutral. Maybe this should be re-thought to go back to the one movement to neutral.
Still think shifting to neutral is the best thing to do, it's easier to locate and slam the shifter up, most won't go to reverse without the release button. Easier than finding and turning the key and you don't lose your power steering/brakes. It should be part of every defensive driving course. Everyone that drives a DBW vehicle should practice in a parking lot.
You don't have to worry about hurting the engine, all DBW cars are rev limited and most are rev limited to 4,000rpm when the shifter is in neutral.
Maybe a kill switch system if you're going to use the complex remote keys, sort of like a dirt bike, only one easy access fool proof switch, all it does is kill the engine. But then you have to train drivers to drive without PS, PB.
I would like to see information such as where the ECU is manufactured. I can relate to "computer problems", I work at a place that designs and builds, markets thier own products, that have a computer in them for control functions. I also am very well versed in CNC machine tools, that also have a computer or many computers in them for control purposes. I am not sure where the computers are made that my place of employment use, but I do know we have our share of major problems with them and some major returns of product because of them, also I very well know what happens when a CNC machine tool has a computer glitch and crashes, so for anyone to come out and say it's not a computer problem, they should reexamine the information out there. The pedal is not sticking in some of the cases.
What ever it is, it is bad workmanship from some entity.
And a shame that people lost thier lives from it.
This should be a wakeup call for mandating strict emissions standards and forcing DBW or anyother type of control that removes the drivers input to the function and transfers it to a computer.
The other latest thing is computer controlled brakes in the hybrids, whats next?
What ever it is, it is bad workmanship from some entity.
And a shame that people lost thier lives from it.
This should be a wakeup call for mandating strict emissions standards and forcing DBW or anyother type of control that removes the drivers input to the function and transfers it to a computer.
The other latest thing is computer controlled brakes in the hybrids, whats next?
MacGyverS2000
Electrical
What do strict emissions standards have to do with this? And the problem here could very well be due to removing the driver's control from the equation.
Dan - Owner
Dan - Owner
NormPeterson
Structural
As emissions standards get increassingly strict, there is greater pressure to attack much smaller transient conditions which tend to give brief "spikes" in the emissions. Once you're really 'clean' 99.5% of the time, being rather 'dirty' for much of that remaining 0.5% matters more.
Just off the top of my head, allowing the throttle to snap shut as would typically happen with a purely mechanical throttle on a vehicle with a conventional manual transmission (think upshift here) is one example where emissions performance has "forced" some alteration in the relationship between the pedal and throttle positions. Has for a while.
Norm
Just off the top of my head, allowing the throttle to snap shut as would typically happen with a purely mechanical throttle on a vehicle with a conventional manual transmission (think upshift here) is one example where emissions performance has "forced" some alteration in the relationship between the pedal and throttle positions. Has for a while.
Norm
![[peace]](/data/assets/smilies/peace.gif "[peace] [peace]")
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thruthefence
Aerospace
I think the ecu has an input for "brake application" as well as turning the lights on, coasting for a certain time frame, lots of stuff thats doesn't seeem like it's needed, but someone thought it was necessary.
NormPeterson
Structural
Let's just say that the effective rate of throttle closure can be electronically modulated, either slowed or briefly raised and then allowed to drop at some emissions-friendly rate. If you'll accept the behavior of my 2001 Maxima (MT) as adequate evidence, this can even be done on a mechanically controlled throttle design, probably via the idle air bypass and its control valve (which is PCM-controlled).
Norm
Norm
GregLocock
Automotive
Norm - Early emissions cars even with carbs had anti-snap shut dampers. For example a 1988 era VW Jetta, if you accelerated the engine to 4000 rpm and released the throttle, would hang at 1800 rpm for a while, to burn off HCs at a rough guess.
Mazdas and Fords, and for that matter my Corona (Airpump/carb) did it as well. Not that it ever revved to 4000.
evelrod - nothing, or more accurately, whatever they programmed it to do. I drove 4 makes of cars and all allowed neutral to be selected while driving, two were definitely shift by wire. So until I find a car that blocks shifts into neutral I can't tell you!
dicer-virtually all computers of all types are basically built in SE Asia, statistically speaking. Especially the reliable ones.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376
Mazdas and Fords, and for that matter my Corona (Airpump/carb) did it as well. Not that it ever revved to 4000.
evelrod - nothing, or more accurately, whatever they programmed it to do. I drove 4 makes of cars and all allowed neutral to be selected while driving, two were definitely shift by wire. So until I find a car that blocks shifts into neutral I can't tell you!
dicer-virtually all computers of all types are basically built in SE Asia, statistically speaking. Especially the reliable ones.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376
ChrisDuncan
Mechanical
I also think it could be some kind of outside interference.
Like an ECU will become erratic if a large amp power wire is routed in close proximity, something about electro-magnetic fields.
I've also seen cell phones clear immobilizer key chips when they are stored next to each other.
Another thing that happens is when a laptop is placed on a air bag seat occupant height sensor, it can cause erratic operation.
These critical throttle/brake electronic systems need to have the same rigorous safety measures and redundancies as the typical air-bag system. AFAIK no airbags have gone off by themselves and they are just as complex of a system.
Like an ECU will become erratic if a large amp power wire is routed in close proximity, something about electro-magnetic fields.
I've also seen cell phones clear immobilizer key chips when they are stored next to each other.
Another thing that happens is when a laptop is placed on a air bag seat occupant height sensor, it can cause erratic operation.
These critical throttle/brake electronic systems need to have the same rigorous safety measures and redundancies as the typical air-bag system. AFAIK no airbags have gone off by themselves and they are just as complex of a system.
GregLocock
Automotive
"Like an ECU will become erratic if a large amp power wire is routed in close proximity, something about electro-magnetic fields."
That's EMC or EMI testing, every design of car is checked for it, but the suspicion is that this doesn't catch every problem.
Other things include degraded or failed sensors, and unusual timing loops.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376
That's EMC or EMI testing, every design of car is checked for it, but the suspicion is that this doesn't catch every problem.
Other things include degraded or failed sensors, and unusual timing loops.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376
I would expect any firmware issues to occur in the field more frequently than we have seen - and perhaps be more easily reproducible on the bench.
It may be just the media, but Toyota's "shim" fix was quoted as being fabricated from steel. Why not aluminum or plastic? It there an electromagnetic function to this part as well as defeating the otherwise-helpful friction damper?
I would guess the feed signal to the pedal is some sort of high frequency voltage or current and the sensor changes the inductance. Any knowledge here of the electrical details?
It may be just the media, but Toyota's "shim" fix was quoted as being fabricated from steel. Why not aluminum or plastic? It there an electromagnetic function to this part as well as defeating the otherwise-helpful friction damper?
I would guess the feed signal to the pedal is some sort of high frequency voltage or current and the sensor changes the inductance. Any knowledge here of the electrical details?
LionelHutz
Electrical
So, will all these Toyota's go into neutral at WOT if so shifted? I have not read that they would not so I highly doubt that neutral is locked out.
I know at least some of these cars are push button start and that requires holding the button 3 seconds to get the engine to "emergency" power off. So, these cars can be difficult to shut off in a panic situation.
So, it's the typical more than one thing causing most of the accidents. Once the throttle sticks, it's partly the driver not handling the situation well and it's partly the fact that the car can't be shut off easily which would be many persons first reaction in such a situation. Having decent panic situation training as part of the license requirements would certainly help with this problem, as well as helping in many other complete "fails" I've seen on the roads.
Greg's link shows pics of the disassembled pedal assembly and the fix looks quite plausible to me. The friction block operates via a lever connected to the return spring. The shim goes behind this lever and keeps the spring from either putting any pressure on the friction block or it limits the pressure on the friction block.
I know at least some of these cars are push button start and that requires holding the button 3 seconds to get the engine to "emergency" power off. So, these cars can be difficult to shut off in a panic situation.
So, it's the typical more than one thing causing most of the accidents. Once the throttle sticks, it's partly the driver not handling the situation well and it's partly the fact that the car can't be shut off easily which would be many persons first reaction in such a situation. Having decent panic situation training as part of the license requirements would certainly help with this problem, as well as helping in many other complete "fails" I've seen on the roads.
Greg's link shows pics of the disassembled pedal assembly and the fix looks quite plausible to me. The friction block operates via a lever connected to the return spring. The shim goes behind this lever and keeps the spring from either putting any pressure on the friction block or it limits the pressure on the friction block.
MacGyverS2000
Electrical
Kiwi,
Steel is probably cheaper than aluminum and more wear-resistant than plastic. No EM function...
Dan - Owner
Steel is probably cheaper than aluminum and more wear-resistant than plastic. No EM function...
Dan - Owner
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