Jon -
The SBEC controls the vertical AND the horizontal...
No, seriously, it controls the ignition advance, the duration of
injector pulses - thus the fuel/air ratio, it controls when your OD can
engage... just about everything that used to be controlled by a myriad
of mechanical thingies.
The reason the result is so much better than the old method (do
you remember what smog cars from the '70s were like? Cough, gag.) is that
while each of the mechanical thingies can be engineered to do a pretty
respectable job (ah, the beauty of a Weber progressive carb), they know
nothing about what the other thingies are doing. Sure, you can route
vacuum hoses this way and that and convey SOME information, but you can't
come close to what the computer - with all that knowledge in one place -
can do.
The computer DOES become a single point of failure, but the
reliability of modern electronics is also far better than most of the old
mechanical things.
The actual smarts the computer has to embody are not really all
that impressive. Much of the engineering involves normalizing sensor
inputs to values you can use in your control law - which is a fancy
equation with six or eight inputs. The other thing you have to worry
about is special cases - like when the O2 sensor is too cold to give you
valid readings, so you have to operate in open loop. Or when a sensor
fails, and you have to provide some way to limp home.
They still have plenty of oomph to give you cruise control and
burglar alarms at essentially no extra cost (just switches and servos).
And they have enough memeory to store your trouble codes for later
diagnosis, or to store on-board test programs (OBD-II) or good-behavior
data (OBD-III and -IV).
BTW, I would expect that eventually the trouble and behavior
data will be non-volatile, so the trick of pulling the battery lead would
not clear your misdeeds. I expect a log of your vehicle's emissions
history will be the first thing up the pike, speed records not for quite
a while (gotta disarm America first).
Jim
"The road to tyranny, we must never forget, begins
with the destruction of the truth."
-- Bill Clinton, 10/15/95, speech at University of Connecticut,
"Fifty Years After Nuremburg: Human Rights & The Rule Of Law"
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