electronic throttle
in [Technical]
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From: jim beam on 7 Mar 2010 14:02 On 03/07/2010 09:44 AM, Bill Putney wrote: > jim beam wrote: >> On 03/07/2010 08:10 AM, Bill Putney wrote: >>> jim beam wrote: > >>>> i have done this. with the engine off, the vacuum remains until the >>>> pedal is released - thus if you stomp the pedal and keep it there, you >>>> don't need to keep replenishing the vacuum. and you will stop the car. >>>> with the engine running, there is no vacuum issue, and the brakes are >>>> still powerful enough to stop the car. on my honda anyway. >>> >>> I have real trouble believing that a large majority of people would, in >>> a sudden inadvertent acceleration situation, be content to press the >>> brakes one time and not try to pump them once or twice. >> >> why? if the car in front of you suddenly jams on their brakes, do you >> apply then release your pedal? i think your answer is "no" - unless >> you're skidding and know what cadence braking is. and if you know what >> cadence braking is, you should know that to stop a car with the engine >> on full throttle, you apply the brakes hard and quickly - you don't >> monkey about with multiple brake applications that can cause excess >> heating and fade. > > We aren't talking about what the savvy drive does and knows about. What > I've said still stands for the scenario we are talking about and for > many drivers. We weren't talking about what the best thing would be to do. > >>> After that, the >>> brakes will be almost totally ineffective because of loss of vacuum. >> >> no. fade maybe, but vacuum is always present if the engine is running... > > Not enough for any effectiveness of brakes. Do you even know what > happens to plenum vacuum at light, moderate, and heavy throttle? If you > knew the numbers, then you wouldn't be saying that an engine running > (with throttle open) will have enough vacuum to run the brakes - because > it simply isn't true. Anyone who has used a vacuum gage to any extent > knows that vacuum plummets when the throttle is open. then you're making generalizations from your own exceptional experience that are not representative of most vehicle, and certainly not vehicles with standard tuning. vacuum decreases significantly at w.o.t, is sufficient to give brake boost. besides, how much vacuum do you think you need for a brake booster? with a 9" diameter diaphragm, [on the small side by modern standards], that's 63 sq inches. how much pressure delta do you think you need to double a person's braking force? > >> even if it's not, you still have vacuum reserve for three applications. > > That part is arguably true. I'd say you're loosing effectiveness after > 2, but what's one more jab of the brakes between friends. The result > will be that the booster will absolutely *not* charge back to any usable > level under acceleration. you're supposed to apply the brakes and keep them on. only if you release do you lose vacuum. > Plenum vacuum is just too low. Again - you > don't seem to know that - if you want to argue that point, then give me > some numbers for vacuum for a common engine of your choice at idle, and > in gear under light, moderate, and heavy acceleration. If the numbers > you come back with are honest, you will prove what I'm saying. see above. > >>>> with respect, i think you're confusing vacuum with fade... >>> >>> No - I'm not. While you could certainly induce fade with a certain >>> prolonged script of usage of the brakes, what I'm talking about is true >>> over what I would say would be the real world typical scenario (before >>> the fade issue becomes real - which - yes - it would over a longer >>> period, but not likely if the 2 or 3 stabs had already occurred in the >>> relatively short period that I would expect). It is a fact that the >>> vacuum cannot recharge with almost no vacuum in the intake - it doesn't >>> recharge by magic. I guarantee you that after a third stab of the brakes >>> on an engine vacuum-driven power brake car, the brakes will loose the >>> fight with the engine - fade has nothing to do with that over the first >>> few seconds that we would be talking about (during which the first 2 or >>> 3 stabs would occur real world). >> >> if that is your experience, then i think you must have a vacuum leak... > > That is simply not the case. > >> even with wide open throttle, there is sufficient vacuum in the >> manifold to create significant braking assist. > > That is profoundly incorrect - period. again, if that's your experience, i think you're working with something not representative of most vehicles. certainly not anything post 1980. > >>> i've >>>> experienced that too, one particular time on a major hill in san >>>> francisco approaching a busy intersection. yes, it's scary stuff. but >>>> when i changed the pads on my civic from after-market to oem, all fade >>>> problems disappeared. even fully loaded, repeatedly decelerating from >>>> speed. [i learned my "honda oem is best" lesson that way.] > >>>>> I urge anyone who doesn't believe what I claim above to try it before >>>>> commenting. >>>> >>>> i have. my results and comments are as above. > >>> And both of us could design the script to create either end result we >>> wished. I submit that in the real world, most people would try pumping >>> the brakes in desperation if the sudden acceleration scenario actually >>> happened - the depleting stabs would occur before fade became a factor. > >> sorry dude, it's incredibly rare for a panicking driver to pump their >> brakes... > > That's your *theory*, or you have something to back that statement up? where is your "theory" that people pump brakes? i saw someone on a freeway in rain in los angles one time, skating along with their brakes locked, car gently rotating, and the look on her face was that of someone trying to break the pedal off she was pushing it so hard. there's no way that person, as an average driver, was going to let off that pedal, and thus, even though she was going to crash, she was not going to lose vacuum. > Admittedly, my theory that some percentage of drivers would pump the > brakes is not provable as far as I know, but I do state it as > conjecture, not as fact as you are stating your argument. with respect, you're projecting your own behavior as representative of everyone. it's not true. > >> that's why abs exists - abs does that for them, and only in the event >> of traction limit being exceeded.. > > You're not talking about the same situation. Trying to stop a vehicle > with runaway acceleration is not the same setup as emergency accident > avoidance as far as paniced driver psychology. (Yes - there are > similarities, but don't turn that similarity into being equal.) indeed, but i'm pointing out the fact that refutes your supposition - typical panicked drivers do not let off the brake pedal. if they did and were capable of regaining control of the vehicle in skids, we wouldn't have any need for abs. instead, we have abs on almost everything now because the facts show it to help drivers of average ability that just push that pedal as hard as they can. -- nomina rutrum rutrum
From: theref on 7 Mar 2010 14:10 "Grumpy AuContraire" <GrumpyOne(a)GrumpyvilleNOT.com> wrote in message news:99adnZJAetdSdQ7WnZ2dnUVZ_qidnZ2d(a)giganews.com... > bjn wrote: >> On Sat, 06 Mar 2010 10:38:19 -0500, Bill Putney <bptn(a)kinez.net> wrote: >> >>> jim beam wrote: >>>> if you buy all this fear-mongering idiocy that electronic throttle is a >>>> problem, and that brakes, transmissions and ignition kill switches can >>>> all simultaneously fail causing a driver to lose control, it might be >>>> worth auto manufacturers of all stripes to adopt a slightly different >>>> implementation of electronic throttle [e.t.] - if not for mechanical >>>> reasons, but to shut the idiots up... >>> The lawyers, politicians, and news media can convince the public of the >>> impossible (failure even a totally fail safe system) any time they >>> decide to do it depending on political or monetary motivation. IOW - >>> the people and companies who do a good job of designing are going to get >>> punished anyway (unless they know how to play the game in a corrupt >>> system). There are people in our society whose life goal is to make >>> sure that that happens. >> >> >> The problem is that now lawyers, politicians and news media are driving >> (no >> pun intended) solution. The way I see them talking, cars will wind up >> with >> a fail-safe throttle that is more fail-safe than the controls of a jumbo >> passenger jet. >> > > > I'm not sure about this but for sure... The causes you cite certainly > contributed in getting to where we're at! > > Oh, don't forget that little incident when a B-777's engines went to idle > about a minute before touch down at Heathrow about a year ago. Aircraft > was totaled but there were no major injuries. > > Cause has been assessed to software/computer glitch. > > JT I believe that was traced to icing in the fuel system. SOP now is to cycle fuel after prolonged low temp at altitude.
From: Bill Putney on 7 Mar 2010 15:42 jim beam wrote: > On 03/07/2010 09:44 AM, Bill Putney wrote: > then you're making generalizations from your own exceptional experience > that are not representative of most vehicle, and certainly not vehicles > with standard tuning. vacuum decreases significantly at w.o.t, is > sufficient to give brake boost. > > besides, how much vacuum do you think you need for a brake booster? with > a 9" diameter diaphragm, [on the small side by modern standards], that's > 63 sq inches. how much pressure delta do you think you need to double a > person's braking force? You'd have to know the mechanical advantage in the pedal from basic lever math and a bunch of other stuff that is beyond what either of us wants to get into here. Without the absolute numbers for all that stuff, it suffices to ratio things: When the booster is designed to properly operate at 7 times the vacuum that you'll get from an engine under acceleration, I say your assist is going to be close to useless - the engine will likely overcome the brakes in being able to sustain highway speeds (and this is before fade comes into the picture). Saying that 63 sq. in. is a big surface area and so even a tiny little vacuum will give you huge force means nothing. Fact is the assist force on the diaphragm with the very low vacuum under acceleration is less than 15% of what it was designed to use under normal stored vacuum conditions. > you're supposed to apply the brakes and keep them on. only if you > release do you lose vacuum. Right or wrong, many people were taught to pump the brakes. Some people will in fact pump the brakes, for any number of reasons. >> Plenum vacuum is just too low. Again - you >> don't seem to know that - if you want to argue that point, then give me >> some numbers for vacuum for a common engine of your choice at idle, and >> in gear under light, moderate, and heavy acceleration. If the numbers >> you come back with are honest, you will prove what I'm saying. > > see above. Yes - please see it. >>> if that is your experience, then i think you must have a vacuum leak... >> >> That is simply not the case. >> >>> even with wide open throttle, there is sufficient vacuum in the >>> manifold to create significant braking assist. >> >> That is profoundly incorrect - period. > > again, if that's your experience, i think you're working with something > not representative of most vehicles. certainly not anything post 1980. Nope. Your assumptions are wrong on both counts. >>> sorry dude, it's incredibly rare for a panicking driver to pump their >>> brakes... >> >> That's your *theory*, or you have something to back that statement up? > > where is your "theory" that people pump brakes? i saw someone on a > freeway in rain in los angles one time, skating along with their brakes > locked, car gently rotating, and the look on her face was that of > someone trying to break the pedal off she was pushing it so hard. > there's no way that person, as an average driver, was going to let off > that pedal, and thus, even though she was going to crash, she was not > going to lose vacuum. You keep throwing in scenarios totally different than what we're talking about. Again - you can't prove your claim that hardly anyone pumps the brakes any more than my claim that a lot of people would pump the brakes - so from that standpoint, it's what we each want to believe until someone presents some hard evidence. Your observations in life are no more or no less valid than mine are - so quit belittling mine and touting your just as anecdotal observations as more than they are. >> Admittedly, my theory that some percentage of drivers would pump the >> brakes is not provable as far as I know, but I do state it as >> conjecture, not as fact as you are stating your argument. > > with respect, you're projecting your own behavior as representative of > everyone. it's not true. Oh - I see - so no one pumps there brakes, either in accident avoidance situations or if faced with runaway acceleration. Got it. (I don't buy it.) >>> that's why abs exists - abs does that for them, and only in the event >>> of traction limit being exceeded.. >> >> You're not talking about the same situation. Trying to stop a vehicle >> with runaway acceleration is not the same setup as emergency accident >> avoidance as far as paniced driver psychology. (Yes - there are >> similarities, but don't turn that similarity into being equal.) > > indeed, but i'm pointing out the fact that refutes your supposition - > typical panicked drivers do not let off the brake pedal. That's your theory and your belief. No more or less valid than mine of the opposite. -- Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')
From: jim beam on 7 Mar 2010 16:39 On 03/07/2010 12:42 PM, Bill Putney wrote: > jim beam wrote: >> On 03/07/2010 09:44 AM, Bill Putney wrote: > >> then you're making generalizations from your own exceptional >> experience that are not representative of most vehicle, and certainly >> not vehicles with standard tuning. vacuum decreases significantly at >> w.o.t, is sufficient to give brake boost. >> >> besides, how much vacuum do you think you need for a brake booster? >> with a 9" diameter diaphragm, [on the small side by modern standards], >> that's 63 sq inches. how much pressure delta do you think you need to >> double a person's braking force? > > You'd have to know the mechanical advantage in the pedal from basic > lever math and a bunch of other stuff that is beyond what either of us > wants to get into here. Without the absolute numbers for all that stuff, > it suffices to ratio things: When the booster is designed to properly > operate at 7 times the vacuum that you'll get from an engine under > acceleration, I say your assist is going to be close to useless how did you manage before the days of vacuum assist? > - the > engine will likely overcome the brakes in being able to sustain highway > speeds (and this is before fade comes into the picture). fade is a feature of people that don't brake decisively and let the vehicle speed up again. or defective design/parts. > > Saying that 63 sq. in. is a big surface area and so even a tiny little > vacuum will give you huge force means nothing. Fact is the assist force > on the diaphragm with the very low vacuum under acceleration is less > than 15% of what it was designed to use under normal stored vacuum > conditions. how did anyone drive a car before the days of vacuum assist? > >> you're supposed to apply the brakes and keep them on. only if you >> release do you lose vacuum. > > Right or wrong, many people were taught to pump the brakes. Some people > will in fact pump the brakes, for any number of reasons. some people will hold their foot on the gas believing it to be the brake too. > >>> Plenum vacuum is just too low. Again - you >>> don't seem to know that - if you want to argue that point, then give me >>> some numbers for vacuum for a common engine of your choice at idle, and >>> in gear under light, moderate, and heavy acceleration. If the numbers >>> you come back with are honest, you will prove what I'm saying. >> >> see above. > > Yes - please see it. > >>>> if that is your experience, then i think you must have a vacuum leak... >>> >>> That is simply not the case. >>> >>>> even with wide open throttle, there is sufficient vacuum in the >>>> manifold to create significant braking assist. >>> >>> That is profoundly incorrect - period. >> >> again, if that's your experience, i think you're working with >> something not representative of most vehicles. certainly not anything >> post 1980. > > Nope. Your assumptions are wrong on both counts. why? why does my car come to halt when i brake hard at full throttle? why doesn't yours? > > >>>> sorry dude, it's incredibly rare for a panicking driver to pump their >>>> brakes... >>> >>> That's your *theory*, or you have something to back that statement up? >> >> where is your "theory" that people pump brakes? i saw someone on a >> freeway in rain in los angles one time, skating along with their >> brakes locked, car gently rotating, and the look on her face was that >> of someone trying to break the pedal off she was pushing it so hard. >> there's no way that person, as an average driver, was going to let off >> that pedal, and thus, even though she was going to crash, she was not >> going to lose vacuum. > > You keep throwing in scenarios totally different than what we're talking > about. no, i'm pointing out the flaw in the argument. for the argument to be valid, it has to work universally. otherwise you need to qualify it to specific circumstances. > Again - you can't prove your claim that hardly anyone pumps the > brakes any more than my claim that a lot of people would pump the brakes > - so from that standpoint, it's what we each want to believe until > someone presents some hard evidence. Your observations in life are no > more or no less valid than mine are - so quit belittling mine and > touting your just as anecdotal observations as more than they are. but dude, why do we have abs? it's not because people pump the brakes because then they'd be unnecessary! > >>> Admittedly, my theory that some percentage of drivers would pump the >>> brakes is not provable as far as I know, but I do state it as >>> conjecture, not as fact as you are stating your argument. >> >> with respect, you're projecting your own behavior as representative of >> everyone. it's not true. > > Oh - I see - so no one pumps there brakes, either in accident avoidance > situations or if faced with runaway acceleration. Got it. (I don't buy it.) abs. that's the reality, like it or not. > >>>> that's why abs exists - abs does that for them, and only in the event >>>> of traction limit being exceeded.. >>> >>> You're not talking about the same situation. Trying to stop a vehicle >>> with runaway acceleration is not the same setup as emergency accident >>> avoidance as far as paniced driver psychology. (Yes - there are >>> similarities, but don't turn that similarity into being equal.) >> >> indeed, but i'm pointing out the fact that refutes your supposition - >> typical panicked drivers do not let off the brake pedal. > > That's your theory and your belief. No more or less valid than mine of > the opposite. > you're entitled to your opinion, but preface them as such. "i believe that..." is quite different from the definitive statements you've been making like "the ... will absolutely *not* ... " etc., because it's not true. -- nomina rutrum rutrum
From: clare on 7 Mar 2010 17:22
On Sat, 06 Mar 2010 17:08:03 -0800, jim beam <me(a)privacy.net> wrote: >On 03/06/2010 04:59 PM, clare(a)snyder.on.ca wrote: >> On Sat, 06 Mar 2010 12:43:14 -0800, jim beam<me(a)privacy.net> wrote: >> >>> On 03/06/2010 09:41 AM, Jim Warman wrote: >>>> The cross posting sucks.. but you guys seem to like it.... >>>> >>>> Toyota is having trouble... Ford isn't (I'm reading this in a Ford NG and I >>>> work at a Ford dealer). >>>> >>>> Drive by wire throttle is a natural progression (if you can't see where the >>>> future of the automobile is going - I feel sorry for you). It allows for >>>> precise (hopefully) control of any electronic stability features, It allows >>>> for torque limiting when appropirate... reducing the need for other traction >>>> control measures (such as active brake booster application) when >>>> necessary... >>>> >>>> Fords system relies on redundancy... I'm not a Toyota tech so I can't tell >>>> you what they do... Fords system has three inputs..(one of them is inversely >>>> proportional). If the inputs aren't "coherent", the car will remain at >>>> idle... >>> >>> three inputs from the throttle pedal position sensor? >>> >> >> 3 inputs are an absolute necessity for true"fail-safe" systems. If 2 >> inputs dissagree, what do you know, other than that you have a >> problem. With 3 inputs, if 2 agree and one dissagrees, you have a >> pretty good idea which input is wrong. > >yeah, i get that, but where are the three inputs? does any vehicle have >more than one pedal position sensor? > One throttle position sensor of the simplest design (a simple potentiometer) can provide 2 signals - one the inverse of the other. The third input could be as simple as a closed throttle ot WOT sensor switch. If the Throttle position and the _throttle position switch dissagreed about whether the throttle was open or closed (ie - the sensor was open or shorted) the idle position switch would confirm if in fact the throttle was at idle. (or the WOT could confirm if it was at WOT) The idle position switch is the simplest because when you first start the engine the computer could poll the position sensor, and if both sides of the pot did not indicate closed throttle, the switch could be asked for it's "vote". That is your "3 inputs" in it's simplest form. > >>> >>> >>>> >>>> Have we seen problems with Fords drive by wire? A very few, but yes.... No >>>> unintended accelerations have been (AFAIK) documented. >>>> >>>> >>>> "Jeff Strickland"<crwlrjeff(a)yahoo.com> wrote in message >>>> news:hmu1u8$uus$1(a)news.eternal-september.org... >>>>> >>>>> "jim beam"<me(a)privacy.net> wrote in message >>>>> news:fvudnV-hwr-Z6A_WnZ2dnUVZ_rednZ2d(a)speakeasy.net... >>>>>> if you buy all this fear-mongering idiocy that electronic throttle is a >>>>>> problem, and that brakes, transmissions and ignition kill switches can >>>>>> all simultaneously fail causing a driver to lose control, it might be >>>>>> worth auto manufacturers of all stripes to adopt a slightly different >>>>>> implementation of electronic throttle [e.t.] - if not for mechanical >>>>>> reasons, but to shut the idiots up. >>>>>> >>>>>> first, lets understand e.t. functionality: >>>>>> >>>>>> 1. open the throttle when demanded >>>>>> 2. close throttle when demanded >>>>>> 3. allow "demand" to account for additional requirements like >>>>>> a. de-throttle on shifting for automatics, >>>>>> b. throttle appropriate to load at high demand [eg. full throttle at low >>>>>> rpms can choke an engine and significantly reduce output - thus >>>>>> de-throttle until revs support full open] >>>>> >>>>> >>>>> The functionality is even easier than that -- open the throttle plate when >>>>> the gas pedal is pressed and close the throttle plate when the gas pedal >>>>> is released. You can get bogged down in semantics if you want, but the >>>>> functiionality is really that simple Go when the pedal is pressed and stop >>>>> going when the pedal is released. At the end of the day, anything else is >>>>> a variation on pushing the pedal down or releasing the pedal so that it >>>>> comes back up. >>>>> >>>>> When or why one might press or release the pedal has no bearing on the >>>>> discussion. The only thing that matters is the expecation that the car >>>>> goes faster when the pedal is pressed and stops going faster when the >>>>> pedal is held at a mid-point, and slows when the pedal is released. >>>>> >>>>> When the throttle control system does those things, then it is doing its >>>>> job. >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>> >>>> >> |