electronic throttle
in [Technical]
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From: Dave on 7 Mar 2010 22:13 "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?
From: fred on 7 Mar 2010 22:35 clare(a)snyder.on.ca wrote in news:35c8p51cs5k40rluhev8lg1ubjs4m7t7kv(a)4ax.com: > 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> >>>> 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. Why don't you actually *see* if it is the case. I'll tell you right now it is absolutely. When you have an object that does over 400Mph in place where the temperature can easily be -100 F icing on the wings is virtually asured. Have you never seen people up on an airliner's wing spraying some kind of fluid? What do you think they're doing? It's called deicing. That's it. Time to permanently take some of these useless groups out. I trust other people who *do* use the follow-up header as it's supposed to will remove them too. Two bloody *relevant* groups FCS.
From: clare on 7 Mar 2010 22:52 On Sun, 07 Mar 2010 18:05:07 -0500, News <News(a)Groups.Name> wrote: >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. OK - I looked it up. Technically this was fuel jelling - common with diesel fuel in arctic conditions. In the case of the Rolls turbines, it was a design fault in the fuel pre-heater unit which resulted in a mandatory replacement with a redesigned heat exchanger. Different than the carb icing on a prop plane.
From: clare on 7 Mar 2010 22:58 On Sun, 07 Mar 2010 18:09:05 -0500, Bill Putney <bptn(a)kinez.net> wrote: >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). Correct - on the GM J and X series cars between 1982 and 1986 a backup vacuum pump was installed. At idle with the AC on there was inadequate vacuum to provide braking.
From: clare on 7 Mar 2010 23:09
On Sun, 07 Mar 2010 18:16:23 -0500, Bill Putney <bptn(a)kinez.net> wrote: >clare(a)snyder.on.ca wrote: > >> One throttle position sensor of the simplest design (a simple >> potentiometer) can provide 2 signals - one the inverse of the other. > >Clare - I followed the rest of your explanation, but, as a circuit >designer, I had trouble following that part. That would have to be two >potentiometers ganged on one shaft? You're not saying that one >potentiometer provides two signals, right? I'm picturing a TPS pot. >with ground on one end, Vref on the other, and the wiper signal. I >don't see getting two signals from the one pot, inverse or otherwise. >What did I miss? Just raise the ground so the 5 volt reference is , say, 6 volts above ground, and the "ground" is 1 volt above ground and measure the voltage between the wiper and ground and between the wiper and "ref" At idle the wiper to "ground" will be one volt, and between the wiper and "ref" will be 5 volts. At half throttle you will have roughly 3 volts from either wiper to ref, or wiper to ground, and at WOT you will have 0 volts wiper to ref, and 6 volts wiper to ground. Can also be done without raising the "ground", but then a zero volt is possible at idle as a legitimate signal. With a raised ground, a open anywhere in the ref circuit would give you a 0 volt reading which is not a legitimate signal, so would trigger an error without having to compare any other voltages.. Without the raised ground, idle position voltage is undiscernable from a fault voltage untill the pedal is depressed, so a closed throttle sensor is required to verify that the throttle is, in fact, closed. So there you have it. Simple, isn't it?? (once you get your head around it) |