electronic throttle
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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: jim beam on 7 Mar 2010 14:03 On 03/07/2010 09:57 AM, Bill Putney wrote: > jim beam wrote: >> On 03/07/2010 08:13 AM, Bill Putney wrote: > >>> By the second stab, typically brake effectiveness is reduced >>> considerably. By third stab - engine overpowers brakes - power assist is >>> negligible. No leaks, >> >> i'll bet you haven't actually tested that. all you know from driving >> is that there is sufficient vacuum for the brakes to appear to work >> ok, i.e., evacuation rate > leak rate. it's only when leak rate > >> evacuation rate that people notice anything. in the mean time, a slow >> leak might be sufficient to lose vacuum in 30 seconds or less. > > Then we disagree. I said this was on multiple cars with no leaks. > > But in any case, it appears that we agree on more than 3 stabs. Except > you still believe that there is sufficient vacuum in the plenum of an > engine in gear under acceleration to charge the booster to usable level > - and that is simply not correct. ok bill, give me your manifold vacuum numbers. even one inHg [a low number btw] is ~2lbs. for 63 sq ins, that's still 126 lbs boost in addition to what the driver can apply. it may not be great, [assuming the driver has wasted their previous vacuum on multiple brake applications] but it'll still help stop the car. > >>> multiple cars in perfect condition. > -- nomina rutrum rutrum
From: jim beam on 7 Mar 2010 14:04 On 03/07/2010 09:52 AM, Jeff Strickland wrote: > "jim beam"<me(a)privacy.net> wrote in message > news:xbWdnV8Xic4E3Q7WnZ2dnUVZ_rGdnZ2d(a)speakeasy.net... >> On 03/06/2010 08:36 PM, Bill Putney wrote: >>> Jeff Strickland wrote: >>> >>>> ...We have not explored the interaction of traction control and >>>> antilock brakes preventing the brakes from stopping a car with a >>>> throttle intent on being set to the maximum setting. We also have not >>>> looked at the issue of brake fade that comes from the brakes getting >>>> hot. If the brakes locked the front tires, the ABS would sense this >>>> and unlock them. The driver might keep his foot planted firmly on the >>>> brake pedal which has sunk to the floor, but the car still would not >>>> stop. The brakes get hot and fade badly, and the car wouldn't even >>>> slow down... >>> >>> Read my previous post. With throttle applied (even partial throttle), >>> the booster vacuum gets depleted *rapidly*. There is no way to use the >>> brakes to stop a car with an engine of any power at all with throttle >>> applied since, with throttle applied, intake vacuum drops to close to >>> zero. No vacuum = essentially no brakes. Try the experiment I described >>> in my previous post. >>> >> >> no dude. even with no engine running to replenish vacuum, there is still >> sufficient vacuum reserve in the booster to apply the brakes full-on three >> times. unless you have a leak of course, which could also be affecting >> your experience. >> > > > Doesn't matter. Even if the driver holds the brake pedal, the brakes get hot > and fade, and this will cause them to stop doing the job they are supposed > to do. if the brakes fade badly enough, even vacuum assist won't help much. > > The ONLY acceptable condition is that the engine return to idle when the gas > pedal is released. The condition that is REQUIRED, no matter what sort of > linkage -- mechanical or electronic -- is that the engine speed up when the > pedla is pressed, hold steady when the pedal is set to any mid-scale > position, and slow when the pedal is released. Unless these conditions > happen in 100% of the instances, the mechanism is faulty. Period. > > Nobody should ever be exposed to a runaway car, either as a bystander or an > occupant of the car. > > We don't know the causes of the runaway Toyotas, but whatever the causes, > they do not appear to be operator induced. where is the evidence??? the presumed "reason" keeps shifting. currently, it's the electronics because that's the black box joe public doesn't know about and fears [mind you, i can't blame anyone running windows for believing that], but we've not been given anything to support that presumption, and that theory fails the logic test of why the engine computer is supposed to be running perfectly for injection and ignition, but failing for transmission, power and throttle. > And the operators seem to have > been unable to counteract whatever the causes were. my grandmother was unable to act when she was pressing the wrong pedal in her frod. no amount of hysteria, manipulation or back-door protectionism will cure that. -- 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: Jeff Strickland on 7 Mar 2010 14:21
"jim beam" <me(a)privacy.net> wrote in message news:F4udnU6SrZ0kZQ7WnZ2dnUVZ_vQAAAAA(a)speakeasy.net... > On 03/07/2010 09:52 AM, Jeff Strickland wrote: >> "jim beam"<me(a)privacy.net> wrote in message >> news:xbWdnV8Xic4E3Q7WnZ2dnUVZ_rGdnZ2d(a)speakeasy.net... >>> On 03/06/2010 08:36 PM, Bill Putney wrote: >>>> Jeff Strickland wrote: >>>> >>>>> ...We have not explored the interaction of traction control and >>>>> antilock brakes preventing the brakes from stopping a car with a >>>>> throttle intent on being set to the maximum setting. We also have not >>>>> looked at the issue of brake fade that comes from the brakes getting >>>>> hot. If the brakes locked the front tires, the ABS would sense this >>>>> and unlock them. The driver might keep his foot planted firmly on the >>>>> brake pedal which has sunk to the floor, but the car still would not >>>>> stop. The brakes get hot and fade badly, and the car wouldn't even >>>>> slow down... >>>> >>>> Read my previous post. With throttle applied (even partial throttle), >>>> the booster vacuum gets depleted *rapidly*. There is no way to use the >>>> brakes to stop a car with an engine of any power at all with throttle >>>> applied since, with throttle applied, intake vacuum drops to close to >>>> zero. No vacuum = essentially no brakes. Try the experiment I described >>>> in my previous post. >>>> >>> >>> no dude. even with no engine running to replenish vacuum, there is >>> still >>> sufficient vacuum reserve in the booster to apply the brakes full-on >>> three >>> times. unless you have a leak of course, which could also be affecting >>> your experience. >>> >> >> >> Doesn't matter. Even if the driver holds the brake pedal, the brakes get >> hot >> and fade, and this will cause them to stop doing the job they are >> supposed >> to do. > > if the brakes fade badly enough, even vacuum assist won't help much. > > Which is why a driver might not be able to stop a runaway car. You keep saying that a driver can always stop a car by standing onthe brakes, the facts are that this is not absolutely true. It's not even generally true, but I'll give you the point that it's theoretically possible that a car can be stopped while the throttle is held open and the brakes are held down. As a practical matter, I don't think most people can manage such a situation. |