electronic throttle

they'll fail, but depending on their quality [see clare's response], you
can quite easily get 50,000 hours of electronics. there aren't many car
engines give that kind of service.

 

don't german cars already do this? one power line, one signal line, and
reader/switch modules on each light?

 

BMWs for the last 10 years. They also notify you of burned out bulbs
(via lack of voltage drop in the circuit.) Now, you see BMW drivers
that don't use their signals (not my family!), but it's not because they're
in-operative.

FloydR

 

Thanks, you're right; I remember now that they mentioned the Pitot tube.

 

This used to happen mostly when in a long slow moving queue of traffic. With
the engine on tick over in second gear at about 10 mph, if the clutch pedal
was pressed down, then released unexpected acceleration was the result, boy
did they take off. I think that was pretty dangerous if it was an older
driver whose reactions are slower.

Oh yes, of course.

--- news://freenews.netfront.net/ - complaints: ---

 

I stand corrected. I checked a pukka source. I now agree with you... (I
had been thinking of gelatine in particular).

DAS

To reply directly replace 'nospam' with 'schmetterling'
--
[...]

[...]

 

I got a LOT more information on how Toyota REALLY does it. I'll share
later tonight.

 

Not just German - but BMW is in for the lang haul.

It's called CanBus

 

Day-yam... You must be older than me... '49 beetle???

<groan>

JT

 

Occasionally people would skimp on the anti-freeze/water ratio and the
coolant would become slushy. Just a little moisture on the exterior of
the radiator in motion would drive the temperature down and bingo! No
circulation and an overheated engine!

Ah... The good ol' days..

JT

 

I was 21 when I bougt it, and it was 24.
Now you know how old I am.

 

OK - Here's what I've found.
Toyota throttle has 2 hall effect sensors. The output of one tracks
the other but is offset. In other words, one starts at say, 0 volts,
and the other at, say 1 volt - and they increase in step with each
other. That way the CPU can tell if one has failed, and if the two
outputs are shorted together (one bypassed)
If either accelerator sensor fails, the CEL comes on and the vehicle
is limited to 1/4 throttle.
If both fail, the throttle gets set to a fast idle position and the
rpm is controlled to normal idle speed by programmed missfire
(injector cut)

The throttle position sensor (throttle feedback) also has 2 hall
effect sensors 0 and they have differnt "rates" - the primary gives a
higher signal linear from closed to open, while the secondary reads
full by about half throttle.

If the CPU senses a single TPS failure the engine is reduced to a fast
idle. iF BOTH tps fail, it is returned to base idle - and if the ECU
determines that the throttle has NOT closed - the engine is shut off.


The ECU has 2 CPUs. the main monitors all sensors and controlls the
entire power-train - engine, transmission, cruise control, traction
control, etc.
The "sub" monitors all sensors and all outputs - and monitors the main
CPU via a "watchdog" program.
The sub ALSO controls the electronic throttle. Both cpus control an
output transistor that feeds power to the throttle control motor -
BOTH must be turned on in order to open the throttle. They are series
connected).If either CPU senses a problem and shuts down, there is no
throttle.


Gets pretty darn difficult to envision any electronic error that
could cause uncontrolled accelleration, particularly without
registering a code and turning on the CEL.

 

Interesting - I always thought of Hall effect sensors as switches
(on/off, proximity, etc.). I wasn't aware that they could be used for
analog pruposes, but a little research shows that they can indeed.

 

wrote:

Toyota throttle has 2 hall effect sensors. The output of one tracks the
other but is offset. In other words, one starts at say, 0 volts, and the
other at, say 1 volt - and they increase in step with each other. That way
the CPU can tell if one has failed, and if the two outputs are shorted
together (one bypassed) If either accelerator sensor fails, the CEL comes on
and the vehicle is limited to 1/4 throttle. If both fail, the throttle
gets set to a fast idle position and the rpm is controlled to normal idle
speed by programmed [missfire] (injector cut) The throttle position sensor
(throttle feedback) also has 2 hall effect sensors 0 and they have
[different] "rates" - the primary gives a higher signal linear from closed
to open, while the secondary reads full by about half throttle.
If the CPU senses a single TPS failure the engine is reduced to a fast idle.
iF BOTH tps fail, it is returned to base idle - and if the ECU determines
that the throttle has NOT closed - the engine is shut off. The ECU has 2
CPUs. the main monitors all sensors and [controlls] the entire power-train -
engine, transmission, cruise control, traction control, etc. The "sub"
monitors all sensors and all outputs - and monitors the main CPU via a
"watchdog" program. The sub ALSO controls the electronic throttle. Both
cpus control an output transistor that feeds power to the throttle control
motor - BOTH must be turned on in order to open the throttle. They are
series connected). If either CPU senses a problem and shuts down, there is
no throttle. Gets pretty darn difficult to envision any electronic error
that could cause uncontrolled [accelleration], particularly without
registering a code and turning on the CEL.
_________________________________________________________________________

Once upon a time there was a cable from the gas pedal to the
throttle that operated the throttle butterfly. The throttle
shaft had a position sensor that told the computer how much
power the driver was demanding.

Someone figured they could save money by eliminating the
cable and attaching a position sensor to the gas pedal to tell
the computer the driver's gas pedal position. The throttle
shaft still had to have a position sensor to let the computer
know its state compared to the pedal position, so the cost
tradeoff was one less cable and one more position sensor.

But there were more costs. The throttle butterfly no longer
had the driver's foot power to move it, so they had to add a
servo device to the throttle to provide power to the butterfly,
and controlling power transistors to drive the servo, plus
a reprogrammed computer to keep track of it.

More complexity, added electromechanical hardware, higher
cost, multiple new interfaces, and more computer operations.
The whole thing sounds like a joke invented by Rube Goldberg.

Rodan.

 

And more otherwise good cars hauled off to the junk yard when the cost
and bother of troubleshooting and repairing the problems created by the
complexity far exceeding the dollar value of the vehicle. Perhaps that
is part of the goal of the explosion in complexity.

 

All to make it easier to meet emissions specs...

 

Would be true, except it had NOTHING to do with saving money, and the
throttle position sensor doesn't tell how much power is required -
just how impatient the driver is!!

 

____________________________________________________________________

wrote:

Would be true, except it had NOTHING to do with saving money,
and the throttle position sensor doesn't tell how much power is
required - just how impatient the driver is!!
____________________________________________________________________

You're right, of course. It had nothing to do with saving money.
It costs more, it's more complex, it adds more electromechanical
hardware and increases electrical, mechanical, and computer interfaces.
It introduces multiple new failure modes, while yielding no significant
improvement in gas mileage or pollution control. It is a money pit,
a maintenance nightmare and a death trap waiting for a victim.

So why would anyone other than Rube Goldberg build such a useless
(and dangerous) contraption? My guess is that the automakers are
trying to develop a generic accelerator pedal that would work for any
automotive power plant combination. A single pedal would indicate
the driver's intention to a gas engine, electric motor, hybrid, steam
engine, or rear-engine system, or an engine powered by tram cables.

Unfortunately, in their zeal to prove the concept, they chose to dismantle
and scrap the simple, proven, reliable gas pedal-to-cable mechanism for
their experiment, resulting in more danger for conventional automobiles.

Regarding the throttle position sensor - until fly-by-wire took throttle
position control away from the driver it did indicate the driver's wishes
for the power level to be applied. Stepping on a gas pedal to open
the throttle is necessary to merge into traffic, to maneuver, and to
maintain separation and safety in traffic conditions. Opening the
throttle doesn't automatically prove that a driver is impatient.

Rodan.

 

EVERYONE is using drive by wire, or has plans to. It has MANY
advantages - and is no more prone, by design, to failure than a cable.
A very simple electrical fault can totally screw up a mechanical cable
connection too. A bad ground can allow fault current to flow through
the throttle cable, melting the plastic sheath, causing a sticking
throttle. It has happened. I've seen it.

Mechanical devices are MORE subject to failure than electronics

As for my saying the throttle just shows how impatient the driver is,
there is NO reason for the throttle on virtually any car to be
"floored" under normal driving conditions.

 

how can that be true???

http://en.wikipedia.org/wiki/Hall_effect

hall effect sensors are used for gross position detection, not small
scale linear deflections. they can be used for "wot" detection, but
their ability to work over a wide positioning range is limited. that's
why they're used in timing for things like crank position [rotational]
sensors where you're counting pulse rates, not graduation functions.

you can have a hall effect sensor at the end of the rotational travel
for wot, and you can compare that output with the potentiometer output,
but the graduated positional sensing is typically done with a potentiometer.