From: clare on
On Sun, 7 Mar 2010 11:44:57 -0000, "David Skelton"
<skellyd8758(a)skynospam.com> wrote:

>We have had three cars (one made in 1997, the second in 2002 and the third
>in 2004) that sometimes used to open the throttle on the 'over run',
>possibly to reduce emissions.
>
>It was unnerving approaching junctions.
>
>All three had mechanical throttle cables, but also motors built into the
>throttle body to drive the throttle plate open.
>
>Two were Fords, the other was a Daewoo with a Suzuki engine.
>
>Best wishes
>
>David
>
>
>
>--- news://freenews.netfront.net/ - complaints: news(a)netfront.net ---
Virtually ALL port injected engines have an electrically operated
"idle speed control" or "air bypass" valve that bypasses air past the
throttle valve for several purposes. It is uded to raise (or maintain)
idle speed when AC is operated, headlights are turned on, or power
steering is used at idle, and it is used to prevent abrupt throttle
closure on decel for emission reasons.
Some older vehicles used an "idle up" solenoid for the same purpose,
while others had an "anti-diesel" solenoid to close the throttle
completely when the ignition was turned off. Other older vehicles used
a "dash pot" or vacuum idle control to do some of the same.

Vehicles with Drive By Wire, in large part, eliminate the ISC system -
which, by the way, is one of the more problem prone subsystems on most
fuel injected vehicles of the last 20 years or so.
From: clare on
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. 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.


From: clare on
On Sun, 7 Mar 2010 11:10:20 -0800, "theref" <theref(a)seanet.com> wrote:

>
>
>"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.
Icing on a JET?????????
Don't think so.
From: News on
clare(a)snyder.on.ca wrote:
> On Sun, 7 Mar 2010 11:10:20 -0800, "theref" <theref(a)seanet.com> wrote:
>
>>
>> "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.
> Icing on a JET?????????
> Don't think so.


Absolutely. Determined to be cause of BA 777 landing short at Heathrow.
From: Bill Putney on
clare(a)snyder.on.ca wrote:

> 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. 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.

Kind of related: In the early 80's (of the last century), when cam
design rules were changing (I think to provide overlap, etc. for
emissions - not 100% sure if that was the exact reason, but I think so),
vacuum levels dropped on engines. Before other methods were figured out
to compensate for that (I'm guessing just building the boosters larger
and futzing with the design of the master cylinders and calipers so the
assist worked well on generally lower vacuum), GM had to install
electrically driven vacuum pumps in the fenders of some of their cars to
provide sufficient booster vacuum.

I found out about that after I installed a "recreation" cam on a 1980
Chev. Citation after its factory cam wore out. After installing the new
cam, the brakes had insufficient assist because the cam design dropped
the vacuum levels. I researched it and found out about the electric
vacuum pumps and went to a junk yard and grabbed one and installed it (I
think from a Pontiac J2000, J4000, or J6000 - something like that) -
anyway, it worked *great*.

In my research at the time, people also told me that electric vacuum
pumps and/or extra vacuum reservoirs were often used on race cars for
the same reason (hi-perf. cams and low vacuum during acceleration).

--
Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')