From: jim beam on 8 Mar 2010 00:44 On 03/07/2010 02:34 PM, clare(a)snyder.on.ca wrote: > 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. that's it. -- nomina rutrum rutrum
From: jim beam on 8 Mar 2010 01:24 On 03/07/2010 02:47 PM, clare(a)snyder.on.ca wrote: > On Sun, 07 Mar 2010 08:24:21 -0800, jim beam<me(a)privacy.net> wrote: > >> On 03/07/2010 08:10 AM, Bill Putney wrote: >>> jim beam wrote: >>>> On 03/06/2010 08:26 PM, Bill Putney wrote: >>> >>>>> 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. >>>> >>>> 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. >> >> >>> 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. >> even if it's not, you still have vacuum reserve for three applications. >> >> >>> >>>>> 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. >>>> >>>> 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. >> even with wide open throttle, there is sufficient vacuum in the manifold >> to create significant braking assist. >> > > Sorry Jim - but you are wrong. > A diesel engined vehicle with a mechanical vacuum pump would work as > you envision - but under any substantial load there is not enough > manifold vacuum produced to provide full braking assist. i didn't say "full". > With both > feet on the brake pedal a strong man MAY be able to provide enough > brake line pressure to stop the car at half throttle. /if/ the driver has pressed and released the pedal a couple of times. why they would do that though is something i don't follow. -- nomina rutrum rutrum
From: jim beam on 8 Mar 2010 01:35 On 03/07/2010 02:38 PM, Bill Putney wrote: > 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". then your experience is not typical - and more importantly, doesn't qualify you to generalize! > >>> - 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. so stop flip-flopping your argument. you don't get fade if you simply stomp the pedal and you don't deplete vacuum either. > >>> 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. not at all. servo brakes are much better, but brakes without were just what you got used to. even today, if i drive my friend's bmw, i have to be careful the first couple of brake applications because i'm used to pressing my honda pedal much harder - i nearly put myself through the windshield. > >>>> 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. it's /the/ problem if you ask me. > >>>> ...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? why? who would do that if they're trying to stop an out-of-control vehicle? > 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. ugh. can't you drive decent cars for pete's sake? > >>>> 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. some??? damned few dude - that's why we have abs. > >>>>> 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. they do nowadays. > 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. with respect, you are not representative. see above. > >>>> 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. but it's not. there is still sufficient vacuum to generate considerable assist. not as much as ideal, but it's still there. > 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? sure. after we go through the fact that you've never driven a vehicle without it and thus don't have experience. -- nomina rutrum rutrum
From: jim beam on 8 Mar 2010 01:36 On 03/07/2010 07:13 PM, Dave wrote: > > "jim beam" <me(a)privacy.net> wrote in message > news:F4udnUySrZ3GZQ7WnZ2dnUVZ_vQAAAAA(a)speakeasy.net... >> On 03/07/2010 09:52 AM, Bill Putney wrote: >>> jim beam wrote: >>>> On 03/07/2010 08:16 AM, Bill Putney wrote: >>>>> dsi1 wrote: >>>>> >>>>>> I certainly believe you. You can get a feel for the amount of reserve >>>>>> vacuum boost on your car by simply repeatedly pressing down on the >>>>>> brakes without starting your engine. If your brakes are working >>>>>> properly, you'll feel the pedal getting firmer until you'll only be >>>>>> able to move the brake pedal a couple of inches of deflection. At >>>>>> that >>>>>> point, you'll have used up all your vacuum reserve. I figure that you >>>>>> should be able to get around 3 stabs at the brakes with mostly full >>>>>> boost. This means you'll only get maybe two chances for full braking >>>>>> after the initial attempt at braking. That's the breaks I guess. :-) >>>>> >>>>> My recollection is that boost is noticeably diminished after the >>>>> second >>>>> stab, greatly diminished by the third stab - engine overpowers brakes >>>>> for most common vehicles. >>>>> >>>> >>>> maybe if the engine is stopped and vacuum gone. but if the engine is >>>> running, you still have vacuum... >>> >>> Then give me some vacuum numbers for idle, and in gear light, moderate, >>> and heavy acceleration for a typical engine. If you can show that >>> moderate to heavy acceleration vacuum levels are anywhere near idle >>> vacuum levels, then I'll concede. >> >> dude, for the typical vacuum diaphragm, you only need the smallest >> vacuum to significantly boost brake pressure. do the math. >> > > You have never driven a vehicle with vacuum actuated wipers, have you? no. did they leak? -- nomina rutrum rutrum
From: jim beam on 8 Mar 2010 01:43
On 03/07/2010 02:33 PM, fred wrote: > 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. but at least there's logic to that - no over-rev for example. no such logic on the p.o.s. chevy when you're trying to drive a mountain road. > > At a glance it sounds to me like we're not actually hearing from people > who *know* what the problem is yet. what "problem"??? other than a political one of course. > Merely seems to be the background > noise of the press et all. "et al" indeed - the astroturfers. -- nomina rutrum rutrum |