From: Jeff Strickland on 7 Dec 2009 11:46 The problem is that Toyota (and others) are using what is termed, fly by wire. In fly by wire, the gas pedal is not mechanically connected to the throttle body. The gas pedal has a servo that tells the computer what the angle is, and the computer then sets the throttle body with a stepper motor to match the angle of the gas pedal. Surely you can see the pitfalls of such a system. Fly by wire is used in lots of applications and when it works properly, it is lighter and more precise than the mechanical linkage(s) it replaces. The military has employed fly by wire for the flight control systems on airplanes for quite some time now. I'm not aware of any failures in aircraft that have resulted from the fly by wire systems they use but I'm not saying there are no failures, just that I don't recall any. In any case, there is a very strong suspicion that the implementation that Toyota is using has problems. I read a report this past weekend (maybe it was last Friday) that the car in San Diego that crashed while the throttle was stuck on full had been reported to have done the same thing a week or two before the car was given to the people that died in it. (The car was a loaner that the dealership gave to people that had their car in for service.) A previous customer had returned the car and told the dealership that the car took off on its own, but the dealership found no fault with it. The customer is reported to have driven the car into the dealership, so whatever happened to it was transient in nature, which is a trait of fly by wire failures -- the system will forget what the proper settings are supposed to be, and have to be reset. A driver that had the capacity to shut the car off or shift out of D could perform the reset that caused the system to work again, and unless somebody was able to read a history file (if there was one) then the circumstances that caused the error might never be found -- until the next person flies the car off of an embankment at 120mph. "dr_jeff" <utz(a)msu.edu> wrote in message news:9IydnR0VWZFbaYbWnZ2dnUVZ_uli4p2d(a)giganews.com... > john wrote: >> Yeah, I think all the recent problems are likely computer related. >> These ECUs just aren't up to their tasks. > > Really. The ECUs definitely have problems, but please show us a better way > that doesn't involve electronics. Carbs worked well, but wasted fuel. > Without electronics, are air would be dirtier, we would use more fuel. > > Please suggest a better way. > > Jeff > >> The problem, according to NHTSA, may be linked to onboard computers. >> "The agency indicates >> the problem could be linked to the onboard computer, or electronic >> control module. " >> >> >> http://www.detroitnews.com/article/20091205/AUTO01/912050334/1148/auto01/Feds-probe-stalling-reports-in-2-Toyota-models
From: Tegger on 7 Dec 2009 20:38 dr_jeff <utz(a)msu.edu> wrote in news:EPKdnVye5YwjEoDWnZ2dnUVZ_tti4p2d(a)giganews.com: > > Yet, while the pedal traditionally operates the throttle, for many > years, the engines have still be controlled by a computer. So, > controlling one other thing is not such a big deal. > The throttle chokes off the air to the engine. If there is no air, the engine can't make power, no matter what else happens. If you entrust air delivery to the computer and something goes wrong and excessive air is admitted, all the other inputs will adjust to suit so that the mixture remains correct. That means more power when power is not wanted. A simple cable connection is the safest and most reliable way to control the power of any road-going automobile engine. Don't want power? Take your foot off the gas. And I don't care if airplanes have had wire-everything for the last 50- years or whatever. Road-going passenger cars are given none of the sort of scrutiny and highly-competent maintenance and inspection that airplanes are given regularly. -- Tegger
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