Ahh, a nice tech. topic!
I see some foggy statements and confusions in the thread, let me
try to clear-up some of it. I have years of experience as an
Electrical/Firmware Engineer, I teach engineering at my local
community college and also at a local university, and although
I haven’t worked in the automobile industry and so do not know
all the industry-insider details, I have designed with many of
the same technologies and techniques that they use.
First some history…
Cars like so many other devices, are going digital. First came the
weird hybrid electro-mechanical “electronic carburetor” (circa
1970’s), and then the snowball grew from there. Drive-by-wire,
that’s been slowly progressing for decades now, the last car part
that people are willing to make digital is the steering wheel,
naturally. The engines, gas pedal, brakes, dashboard, air-bags,
locks, windows, radios, ignition switch have been digital for a
long time now. The transmissions were slow to go digital, but
automatics are digital now-a-days (allowing you to shift them
“manually”). The steering wheel will be the last to go digital.
Goofy steering wheels…
I’ll be happy when we finally get rid of that big goofy steering
wheel, that large only because you needed the extra leverage to
steer the cars of a hundred years ago. Wouldn’t you like a nice
variety of digital user interfaces to choose from? Maybe steer
with a track ball, a joystick/yoke, the young people of today
will obviously be choosing a game pad.
What is digital?...
Electronic controls based on microprocessors/microcontrollers/DSP,
that’s what I mean. Why digital? Because it (well initially it
was) cheaper, faster, easier to repair, little (if any) maintenance
(which means that it is more reliable), smarter, more precise,
more sophisticated, when compared to a mechanism. Mechanisms are
capable of giving you the same features, but they will be heavier,
less reliable, require lubrication, require adjustments, will be
slower, and will be more expensive when comparing apples to apples.
Electronics are NOT making cars more expensive, if electronics
have grow to 50% of the cost of the car, then that is because
of all the lovely features that cars have now-a-days that they
never had with the pricey mechanical systems. Please compare
apples to apples. Compare the cars of today with a 1970’s car,
but add mechanical anti-lock brakes, remote start, automatic
windows/locks, air-bags, etc.
What is a car in 2010, what is an ECM…
GM calls their engine computers Engine Control Modules.
It replaced the carburetor/distributor but does more. In place
of the carburetor it: 1) monitors the engine speed, 2) monitors
the gas pedal setting, 3) adjusts the amount of air intake and 4)
adjusts the amount of gasoline intake to cause the engine to spin
at the commanded speed. They do lots more than that now-a-days
with oxygen, knock, wheel speed, etc. And the manufactures could
very well choose to add more than one computer to do all the work.
The automatic transmission is normally handled separately.
These computers give you all the digital features listed above,
they are networked together inside the walls of your car, a
different sort of network than the Internet.
No gods, no perfections, we are all human…
But no technology is perfect, and in engineering if you increase
any one feature then there will _always_ be a trade-off that
impacts another feature. If you want all the lovely features of
today’s cars, then they might cost more, more parts mean more
repairs than fewer parts, and a big bad data-driven computer
network does require the power to operate it meaning bigger
batteries/alternator, for example.
There are some ways to make a device so that when it fails
to operate properly it only does relatively harmless things.
For example when your battery powered clock runs out of power,
it simply stops and your schedule is destroyed. But when your
battery operated smoke detector is low-on-power, it chirps at
you, destroying your content peace-and-quiet. Which one is the
safer failure? Fail-safes can be gray and foggy, but they can
also be crystal clear. Engineers are well aware of them, and
utilize them appropriately. But how many are appropriate? Well,
if you want a thousand fail-safes, back-up systems with by-pass
switches, and all that goodness, then there is a trade-off, they
will add to the cost and development time, and how many of you will
spend the time/money to test and repair the ailing back-up system?
Fail-safes are not as simple as YES I want it!
Cars do have fail-safes, if your engine spins too fast, approaching
the mechanical limits, you computer kindly ignores the gas
pedal/ignition key and shuts the engine down. (I have it on good
authority that the 1991 Pontiac Grand AM ECM shuts the engine down
at 74 mph in second gear. Don’t try that yourself.) There will
be more of them built into the cars, I can’t give you a complete
list, but I doubt that the engineers simple neglected them.
I don’t know, I hear some vagueness about floor mats jamming pedals
(not an electrical flaw), and humidity jamming the pedal (not
an electrical flaw), I think I’m hearing flawed information from
the journalists. I don’t know what problems Toyotas engineers are
having, but I do know that if the engineers don’t gather or are
given some detailed and accurate information then they’ll just
be forced to take an educated guess at fixing it. An educated
guess can work out, but if they had the problem in their hands
it would work out better.
Worried about cars?...
Ride a bike or walk instead, they are so much safer means of
transportation. No mother ever told a child, “Don’t run out into
the street, you’ll be hit by bicycles and pedestrians!”
In my driving experience, manual transmissions with un-powered
hydraulic clutches can be shifted with the engine off just
as normal. But the powered hydraulic systems they stiffen very
quickly once the engine is off, and so you loose control of them if
the engine spins too fast, the computer shutting the engine off.
You loose control of the motorized windows/wipers also, when the
engine is off. The parking cable engages the rear brakes only, in
an emergency that would lock the rear wheels and make a Hollywood
spectacle of your day, that is a very bad thing, beware.
Your computer(s) can run off the battery, but their
motors/solenoids take a significant amount of energy and might get
disabled in that mode. I’ve run an engine off the battery alone
in a GM Pontiac, with the key in the RUN position, it works in
an emergency. You can test that, make sure that your battery is
operating properly and has been charged (by running the engine)
recently, then just park the car with the engine OFF, carefully
unplug the alternator you might need to unlock the connector
with a flat screwdriver, and start the engine, finally see what
features work and what does not. Knowing that about your car
can help you decide what is available to you in an emergency,
when you have almost no time to react, much less time to test.
You do realize that when the car is moving and the engine is off,
engaging the transmission causes the momentum of the car to spin
the engine, this some adds resistance to your motion although
much less than brakes. The higher gears produce more resistance,
and the lower gears produce less. Your engine probably won’t
spin fast and consistently enough to give your electronics the
power that they need, when engine braking.
What about the bugs!?...
The only reason why you are seeing more bugs in the past decade
or two is because you have more features in your devices.
Computers have lots of features and so lots of bugs. Mechanisms
have bugs too, if humidity is jamming gas pedals, then that’s
a bug. The old mechanisms just have had less because they have
fewer features. Simple firmware is very reliable, think of your
wrist watch, digital radio, microwave oven, digital refrigerator,
digital washing machine, these devices give you few features and
the thought of them having bugs never crossed your mind before
reading this. They are very reliable!
When cars go all electric they won’t need transmissions anymore
(a cost savings!) but then you’ll need lots of batteries or a
proper power grid to run the motor. Reciprocating engines need
transmissions to make them more energy efficient, cars don’t need
transmissions anymore than trains do.
Sorry that I can’t give specific information about the Toyota
problem. But I hope that they background information helps people
to understand what’s happening.