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.
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
>> 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
>>>> 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
> 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
>> 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
>> 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
>>>>>> 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
>>>>> 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
>> 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
>> 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.
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