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
Norm,
Barring burnouts and such, I can't think of a reason why someone in an automatic would need to be pressing both the gas and brake at the same time (drivers are supposed to be taught not to drive with both feet). If the accident is hitting both pedals at once with the same foot, then the brake should still take precedence.
In a manual I see a somewhat "special" case of heel-toeing being allowed, but how often is that done in a Camry? ;-)
Tapping the brake, even accidentally, should act just like when the cruise control is on... the throttle plate is closed and the car begins to slow down. It wouldn't come to a fast halt, but the car would begin to slow down. If there was a failure in their programming that cause the brake pedal to be sensed when it wasn't being touched, the worst-case scenario would be a car that begins losing power... that's a stark contrast to what's happening now, continuing to apply power. There's certainly no need to verify and/or limit speed (as some have suggested on other forums) to implement this plan of attack.
Dan - Owner
Barring burnouts and such, I can't think of a reason why someone in an automatic would need to be pressing both the gas and brake at the same time (drivers are supposed to be taught not to drive with both feet). If the accident is hitting both pedals at once with the same foot, then the brake should still take precedence.
In a manual I see a somewhat "special" case of heel-toeing being allowed, but how often is that done in a Camry? ;-)
Tapping the brake, even accidentally, should act just like when the cruise control is on... the throttle plate is closed and the car begins to slow down. It wouldn't come to a fast halt, but the car would begin to slow down. If there was a failure in their programming that cause the brake pedal to be sensed when it wasn't being touched, the worst-case scenario would be a car that begins losing power... that's a stark contrast to what's happening now, continuing to apply power. There's certainly no need to verify and/or limit speed (as some have suggested on other forums) to implement this plan of attack.
Dan - Owner
NormPeterson
Structural
Should you find yourself having to drive through water deep enough to immerse the brake rotors, it's a good idea to lightly drag the brakes to squeegee as much water as possible from the friction surfaces. Obviously, you'd want to be able to use enough throttle to carry you all the way through without stopping. You might still want to have light braking with part throttle for a short distance afterward, particularly in weather that's cold enough for ice to form.
I can also see it happening while rocking the car to extricate it from snow or, in some locales, mud.
Those are situations that anybody can encounter at any time, and are not at all associated with any sort of unusually "enthusiastic" driving.
Norm
I can also see it happening while rocking the car to extricate it from snow or, in some locales, mud.
Those are situations that anybody can encounter at any time, and are not at all associated with any sort of unusually "enthusiastic" driving.
Norm
I "trail brake" on the race track and on occasion, the street. However, wouldn't it be pretty simple to have a transducer adjusted to a specific pressure...oh, say some significantly higher than "normal" for the throttle cut out?
This morning it seems the recall has hit Europe and Asia, too.
Even some Ford models using the same part supplier...
Dan...Having spent a lot of time in snow country, I can attest to the absolute need of brake/throttle combo.
I have one vehicle with DBW...no problems in 170,000 miles. Even so, what's wrong with conventional mechanical/cable linkage? I've driven well over a million miles with only a couple failures and that was on race cars! Never on the street, even in my younger days and with all the hot rods I built. Even as a teenager, I could engineer reliable throttle linkage (made me popular, too ;-)...)!
Rod
This morning it seems the recall has hit Europe and Asia, too.
Even some Ford models using the same part supplier...
Dan...Having spent a lot of time in snow country, I can attest to the absolute need of brake/throttle combo.
I have one vehicle with DBW...no problems in 170,000 miles. Even so, what's wrong with conventional mechanical/cable linkage? I've driven well over a million miles with only a couple failures and that was on race cars! Never on the street, even in my younger days and with all the hot rods I built. Even as a teenager, I could engineer reliable throttle linkage (made me popular, too ;-)...)!
Rod
MacGyverS2000
Electrical
The only thing "wrong" with mechanical linkages (from the manufacturer's standpoint) is they're more expensive to install than DBW.
Dan - Owner
Dan - Owner
GregLocock
Automotive
There are other advantages, vibration isolation, packaging, reliability, spring to mind. The cost save is quite significant, I'm guessing several dollars.
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
GregLocock
Automotive
Also potentially it simplifies crash and there is definitely a weight reduction.
So DBW is looking pretty damn good from here.
Cheers
Greg Locock
I rarely exceed 1.79 x 10^12 furlongs per fortnight
So DBW is looking pretty damn good from here.
Cheers
Greg Locock
I rarely exceed 1.79 x 10^12 furlongs per fortnight
As far as I understand it the issue is indeed a mechanical problem associated with the accelerator pedal itself, not the electronic actuator of the throttle plate.
The 'DBW' concept is, in modern torque based EMS applications, used for handing over total control of the engines torque generation to the ECU. With the accelerator pedal position not relating to throttle plate position but requested engine torque (or, more, recently wheel torque).
This has benefits for interaction of auto trans, ESP etc etc. It also allows the ECU to select the most fuel economic 'setting' for a given drivers demanded torque and is especially useful when there are variable camshaft position, lift, wastegate control, swirl control valves and combustion mode where a simple throttle angle does not ensure an optimum setting.
MS
The 'DBW' concept is, in modern torque based EMS applications, used for handing over total control of the engines torque generation to the ECU. With the accelerator pedal position not relating to throttle plate position but requested engine torque (or, more, recently wheel torque).
This has benefits for interaction of auto trans, ESP etc etc. It also allows the ECU to select the most fuel economic 'setting' for a given drivers demanded torque and is especially useful when there are variable camshaft position, lift, wastegate control, swirl control valves and combustion mode where a simple throttle angle does not ensure an optimum setting.
MS
- Thread starter
- #28
thruthefence
Aerospace
Slightly OT, but generally related to the subject at hand; a question (or observation).
I drive a Nissan Frontier Pick up truck, four cylinder engine, that is really kinda 'gutless'. I have noticed (and this is strictly subjective) that when I am on an ascending on-ramp, attempting to accelerate & merge with traffic, the truck 'feels' like it has much more power. It just seems to 'pull' and move right on out. It never makes the downshift to a lower gear. It seems to be a "sweet spot" as I add throttle, and accelerate up the on-ramp. Now, I am an old fart, and have driven my share of hot rod cars, in my time. This feels similar to another carb being activated with progressive linkage, or my old Volvo's turbo coming on speed. For some reason I don't notice it when overtaking & passing on a straight road.
Is the ECU clever enough to recognize "ascending on-ramp merging traffic" mode? I'm tempted to plumb in a manifold pressure gauge just to see whats happening during the 'event'.
I drive a Nissan Frontier Pick up truck, four cylinder engine, that is really kinda 'gutless'. I have noticed (and this is strictly subjective) that when I am on an ascending on-ramp, attempting to accelerate & merge with traffic, the truck 'feels' like it has much more power. It just seems to 'pull' and move right on out. It never makes the downshift to a lower gear. It seems to be a "sweet spot" as I add throttle, and accelerate up the on-ramp. Now, I am an old fart, and have driven my share of hot rod cars, in my time. This feels similar to another carb being activated with progressive linkage, or my old Volvo's turbo coming on speed. For some reason I don't notice it when overtaking & passing on a straight road.
Is the ECU clever enough to recognize "ascending on-ramp merging traffic" mode? I'm tempted to plumb in a manifold pressure gauge just to see whats happening during the 'event'.
Compositepro
Chemical
Thruthefence, I've noticed a similar effect on low powered cars. They are surprisingly peppy at low speed but you really notice the lack of power in high speed acceleration. The reason would be that much of the engine's power capability is already being used just to maintain a high speed, with little additional power to accelerate.
- Thread starter
- #31
thruthefence
Aerospace
compositepro, that makes sense, the poor truck is pushing alot of air at 70 mph, not much margin for acceleration.
NormPeterson
Structural
Compositepro - throttle response itself is probably nonlinear by intent. Exaggerating the response at small pedal positions/movements off idle at the expense of higher rpm response will make a car feel "peppier" on the test drive and in "around town" driving. For people who rarely use higher rpms, there are few, if any, apparent downsides.
MS - the opportunity for improving fuel economy and emissions performance had occurred to me, as had the thought that automated rev-matching on downshift probably can't be accomplished in any other fashion. The other items on your list hadn't.
As Pat has noted, what would it take to provide the driver with ultimate override authority to select 'Neutral' or otherwise disconnect the engine from the drive wheels and let the PCM worry about the engine?
Norm
MS - the opportunity for improving fuel economy and emissions performance had occurred to me, as had the thought that automated rev-matching on downshift probably can't be accomplished in any other fashion. The other items on your list hadn't.
As Pat has noted, what would it take to provide the driver with ultimate override authority to select 'Neutral' or otherwise disconnect the engine from the drive wheels and let the PCM worry about the engine?
Norm
patprimmer
New member
Personally I can't imagine the arrogant and disregard involved in taking the ability to select neutral from the driver.
Regards
Pat
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Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &
for site rules
Compositepro
Chemical
Norm, I don't believe that throttle position response is much of a factor because the driver will position the throttle pedal position to whatever is required to give the desired acceleration. As long as the pedal is not floored, the car has adequate power. It is mostly in high speed passing that I'm reminded that the car has limited power because the pedal is floored and the car in barely accelerating. This often aborts the pass and is annoying. Even driving powerful cars the pedal will be floored at the start of passing.
The latest from Toyota (to their dealers) is that the "fix" is "in the mail"...Thursday (maybe)?
The recall has reached three continents and over 4 million cars! Even for a "simple mechanical fix" this has just gotta hurt.
My pals at the Ford dealer are jumping up and down...Sales with late model Toyota trades are 'booming'!
I've been through a couple big recalls in years past. Suffered through Nader's trashing of the Corvair (I had a new '64 Spyder)...Never anything like this, never!
Yep, this has just gotta hurt!
Rod
The recall has reached three continents and over 4 million cars! Even for a "simple mechanical fix" this has just gotta hurt.
My pals at the Ford dealer are jumping up and down...Sales with late model Toyota trades are 'booming'!
I've been through a couple big recalls in years past. Suffered through Nader's trashing of the Corvair (I had a new '64 Spyder)...Never anything like this, never!
Yep, this has just gotta hurt!
Rod
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1
- #36
I saw a headline in today's paper that the fix was on the way now that the government had "approved" the fix. HUH?
I agree with PatPrimmer that the solution ought to be as simple as kicking it into neutral but I think that is obvious only to guys/(gals) like us who know how things work and how to operate the equipment like we want to when that is what is needed. When this first came to light, I, like Pat, thought what is so complicated about this. Just dump the clutch, right? These days, that is done by moving the stick one notch.
I was discussing this with the wife today while out driving as she had ask about the extent and nature of the problem and as a test, I mentioned Pat's solution and asked her if she would think to do this.
She said that she never would have thought of that and it was another (she has many) example of how engineers thought differently from normal people......
I shudder to think that I am sharing the road with people who can't figure out that kicking it into neutral (and listening to the engine scream) is a life saver. I have had to do it a few times in my life for unrelated problems, and it came second nature to me.
rmw
I agree with PatPrimmer that the solution ought to be as simple as kicking it into neutral but I think that is obvious only to guys/(gals) like us who know how things work and how to operate the equipment like we want to when that is what is needed. When this first came to light, I, like Pat, thought what is so complicated about this. Just dump the clutch, right? These days, that is done by moving the stick one notch.
I was discussing this with the wife today while out driving as she had ask about the extent and nature of the problem and as a test, I mentioned Pat's solution and asked her if she would think to do this.
She said that she never would have thought of that and it was another (she has many) example of how engineers thought differently from normal people......
I shudder to think that I am sharing the road with people who can't figure out that kicking it into neutral (and listening to the engine scream) is a life saver. I have had to do it a few times in my life for unrelated problems, and it came second nature to me.
rmw
GregLocock
Automotive
NHTSA don't actually approve recall actions, they just acknowledge them.
Here's TTAC's take on dismantling the recalled CTS design vs the Denso one which is currently considered to be OK
Cheers
Greg Locock
I rarely exceed 1.79 x 10^12 furlongs per fortnight
Here's TTAC's take on dismantling the recalled CTS design vs the Denso one which is currently considered to be OK
Cheers
Greg Locock
I rarely exceed 1.79 x 10^12 furlongs per fortnight
![[smile]](/data/assets/smilies/smile.gif "[smile] [smile]")
never mind power brakes or steering, who needs em....![[wink]](/data/assets/smilies/wink.gif "[wink] [wink]")
. ![[peace]](/data/assets/smilies/peace.gif "[peace] [peace]")
FYI- this includes a diagram of the mechanical cause and proposed fix:
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