From: Jeff Strickland on 7 Dec 2009 11:46
The problem is that Toyota (and others) are using what is termed, fly by
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
> 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.
>> 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. "
From: Tegger on 7 Dec 2009 20:38
dr_jeff <utz(a)msu.edu> wrote in
> 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
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