electronic throttle
in [Technical]
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From: clare on 7 Mar 2010 17:26 On Sat, 06 Mar 2010 23:26:47 -0500, Bill Putney <bptn(a)kinez.net> wrote: >jim beam wrote: >> On 03/06/2010 11:48 AM, Ed Pawlowski wrote: > >>> ...Emergencies do happen and a driver should be competent enough >>> to shift into neutral. >> >> or stomp the brakes - which are three times more powerful than the >> engine,... > >I don't necessarily disagree with the rest of your post, but that part >of your post is definitely incorrect. Have you ever played with your >power brakes while simultaneously pressing the accelerator? Anything >more than one or two initial stabs at the brakes depletes the vacuum >stored in the booster, and with even slight power simultaneously being >demanded of the engine, the vacuum is not enough to directly power the >brakes, much less re-charge the vacuum in the booster. > >People don't believe that, but try it on your car: On a deserted road at >highway speed, stab the brake pedal a couple of times while holding the >gas pedal down a little bit to load the engine slightly (this works >anywhere from slight to WOT throttle). I guarantee you (unless your >brake booster gets its vacuum from something besides the intake vacuum - >like a separate electric motor-driven vacuum pump) that after two or >more stabs at the brake pedal, the braking power will be extremely low - >so low that the engine will have no trouble overpowering the brakes. No >vacuum in the booster essentially equals no brakes. > >Also, once the booster is depleted of vacuum during that experiment, the >vacuum charge in the booster will remain depleted until a second or so >after the throttle is released - IOW - deplete it and continue applying >the throttle (again - doesn't have to be anywhere near WOT) for several >seconds. Every once in a while, while still applying the throttle, try >the brakes again. You will not have any effective braking until *after* >you release the throttle. > >I urge anyone who doesn't believe what I claim above to try it before >commenting. Bill is 100% correct. And as I stated before - IF you are going to attempt to stop a runnaway car with the brakes, make sure you attempt to STOP it, not control it. You have ONE CHANCE. Brake hard - and don't second guess yourself and rekease the brake. He who hesitiates HAS LOST.
From: fred on 7 Mar 2010 17:33 bjn <elvis(a)example.com> wrote in news:hii7p5d6ga5d7ab1s9ok7krqqla85cdki1(a)4ax.com: > 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 think you'll find that commercial and private airliners go in the exact opposite direction.
From: fred on 7 Mar 2010 17:33 jim beam <me(a)privacy.net> wrote in 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] > > if we analyze the above [which is not exhaustive, but representative], > we find that in almost all situations, an e.t. needs to be more closed > than demanded, but seldom, if ever, more open. thus the "solution" to > the fear-mongering might be to have the throttle opened mechanically - > i.e. old fashioned cable linkage, but have the computer control a > closer device. thus, all the above can be implemented electronically, > but whenever the driver lifts their foot, the mechanical closure > cannot be over-ridden. and the throttle can never be more open than > the mechanical throttle command. > > this would not only address the "potential" for a runaway failure > [although how exactly a computer is supposed to fail such that it > won't switch off, disables brakes, disables transmission select, but > still runs its injection code is something i have never seen > explained, even by the most strident "but it must be the electronics" > crowd], but it would also remove the single most annoying thing i have > ever experienced in any vehicle driving experience: chevy's idiot > idea that they need a multi-second delay between foot pedal movement > and e.t movement. anyone that's ever tried to drive a chevy hhr on a > winding mountain road knows what i mean. > Chevrolet's not unique in that regard. The persistant occurance of cars with paddle shifters whose operation have no co-relation to the actual shifting of gears is more of 6the same. At a glance it sounds to me like we're not actually hearing from people who *know* what the problem is yet. Merely seems to be the background noise of the press et all.
From: clare on 7 Mar 2010 17:34 On Sun, 07 Mar 2010 07:12:45 GMT, "MasterBlaster" <Nobodys.Home(a)My.Place> wrote: > >"jim beam" wrote: > >> > Jeff Strickland wrote: >> > YOU (probably in a drunken stupor) said it is feasable to use a mechanical >> > linkage to open the throttle, then use the some other means to close it. >> > Sheer stupidity. >> >> then you're not reading what i said or understanding the control principle. > >I think I understand it. Let's see... > >Similar concept to a Quadrajet carburetor's secondary throttle plate? >In that example, the secondary's linkage is connected to the primary's, >and moves when you floor the gas pedal, but if the choke hasn't opened >all the way yet, then the secondary plates are locked, and not permitted to >open, to prevent the engine from bogging or even stalling when cold. > >As above, with your cable/computer hybrid system, flooring the gas pedal will still >allow the spring-loaded linkage to move, but the throttle plate will only follow the >linkage and open *if* the computer thinks it's safe to do so. If the system sees >you're also pushing hard on the brake pedal, or the car is sliding sideways, or the >ABS system kicks in on a slippery road, or the magic eye scans the invisible bar >code on the speed limit sign and decides you're going too fast, it can override the >gas pedal's position and close the throttle, either partially or completely. All you'd >feel is a decrease in power, and more resistance at the gas pedal as the throttle >plate was pulled closed against the "follow-me" spring in the linkage. >Sounds a lot like the "Traction Control" systems already in use on some cars. > "tandem throttle" Where the computer cannot OPEN the throttle unless the cable op throttle is also open, but the computer can close the throttle any time it likes. The computer can also control the opening of the throttle within the confines of the limit established by the cable op throttle.
From: Bill Putney on 7 Mar 2010 17:38
jim beam wrote: > On 03/07/2010 12:42 PM, Bill Putney wrote: > how did you manage before the days of vacuum assist? In spite of my having gotten my driver's license in about 1966 or 67, My family nor I has ever owned a vehicle without power brakes since then. I did however drive someone's car to an airport one time that did not have power brakes - and I must say - I thought something was seriously wrong with the brakes. Later, I even loudly complained to the owner for having me drive their car in such a dangerous condition (they were a family friend). It was explained to me that that was a car without power brakes - and was typical of them. All I have to say is "WOW". >> - 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. Beating the dead horse, but we're talking about two different things - vacuum depletion and fade. We're going in circles. >> 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? From my one time of driving that car without assist - that's a good question. Stopping distances must have been absolutely awful. >>> 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. That's a whole other problem of course. >>> ...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? No argument if it's a single long application of the brakes. Are we talking about after the brakes are pumped a couple of times after application of throttle? My experiences were on things like an '86 Subaru Turbo wagon, an '88 Cadillac DeVille, '99 Buick Century, and 2 2nd generation Chrysler Concordes - all in tip-top mechanical shape. >>> 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! Some people were taught and developed a lifelong habit of pumping brakes. >>>> 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. Not all cars have ABS. Were not talking about what people should do. I'm saying what many - not just 1 in 100 - *will* do in the situation we are talking about which is unexpected acceleration. >>> 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. I said that about an engine under acceleration not developing enough vacuum to give anything close to expected braking power once the initial booster charge is depleted. That is a fact. Therefore I didn't qualify it, and I didn't need to. Where I did give opinion, I identified it as such. Shall we go thru the math on the 15% vacuum again? -- Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x') |