No subject

Wideband zirconia sensor

A variation on the zirconia sensor, called the 'wideband' sensor, was
introduced by Robert Bosch in 1994 <http://en.wikipedia.org/wiki/1994> but
is presently (2005 <http://en.wikipedia.org/wiki/2005>) used in only a few
vehicles. It is based on a planar zirconia element, but also incorporates a=
n
electrochemical gas pump. An electronic circuit containing a
feedback<http://en.wikipedia.org/wiki/Feedback>loop controls the gas
pump current to keep the output of the electrochemical
cell constant, so that the pump current directly indicates of the oxygen
content of the exhaust gas. This sensor eliminates the averaging delay
inherent in narrowband sensors, allowing the control unit to adjust the fue=
l
delivery and ignition timing of the engine much more rapidly. In the
automotive industry this sensor is also called a *UEGO* (for Universal
Exhaust Gas Oxygen) sensor.

 [edit<http://en.wikipedia.org/w/index.php?title=3DOxygen_sensor&action=3De=
dit&section=3D8>
]

Location of the probe in a system

The probe is typically screwed into a tapped hole in the exhaust, located
after the branch manifold of the exhaust system combines, and before the CA=
T
(catalytic converter <http://en.wikipedia.org/wiki/Catalytic_converter>).
[edit<http://en.wikipedia.org/w/index.php?title=3DOxygen_sensor&action=3Ded=
it&section=3D9>
]

Common failure modes

Lambda probes have a limited lifespan since the exposed sensor element is
subjected to high temperatures which causes fatigue over time. Probes becom=
e
sluggish, failing to react quickly to changes in the condition of the
exhaust gases. This can be caused by contamination from the engine, fuel or
additives. One common fault is
silicon<http://en.wikipedia.org/wiki/Silicon>buildup on the probe
sensor. A common source of silicon contamination is
through the use of silicone sealant in repairing water system leaks. Lead
build-up from the use of lead additives or leaded petrol will also damage
the probe, as will carbon build-up from excessive burning of engine oil.
Phosphorus in the burnt oil is also a specific damaging contaminant (but th=
e
phosphorus is part of a very beneficial additive called ZDDP which as of
2005 is yet to be replaced with a less 'damaging' (to the sensor or
emissions equipment) yet equally effective (in protecting the motor life)
substitute. It would be expected that a probe would last for 3 years or
40,000 miles (about 64,000 km), but it has been observed that probes will
last for up to 3 times this length. [Also, oxygen sensors have been used
successfully for 2 years of racing with leaded gas when the sensor is put
into a non-leaded gas burning vehicle to 'burn' off the lead then putting i=
t
back, etc. (from geneberg.com)]




On 2/12/06, Joshua Van tol <josh at spiny.com> wrote:
>
> I can't think of a reason why you couldn't use the stock sniffer tube
> location.
>
> On Feb 11, 2006, at 2:35 PM, Dave Forgie wrote:
>
> > Sorry but it cut the following off (AGAIN). SO third time lucky??:
> >
> >> From what I have been told, they use a "sniffer" tube stuck in the
> > tailpipe.  When I told them that we all run cats, they said the A/F
> > results won't be correct but they will be able to tell if we are
> > rich or
> > lean (but not the exact ratio, I guess).
> >
> > Question: For those that have done dyno days, can the OE sniffer tube
> > just downstream of the turbo be used to get the correct A/F ratio
> > OR do
> > we really need a second "bung" downstream of the O2 sensor? I hope the
> > sniffer tube can be used because all but one of the seven of us signed
> > up are running OE down pipes (the seventh has a Gen IV Stromung)
> > and the
> >
> > likelihood of us all running out and getting a bung installed before
> > March 11th is slim.
> >
> > Thanks in advance.
> >
> > Dave F.
> >
> > _______________________________________________
> > S-CAR-List mailing list
> > S-CAR-List at audifans.com
> > http://www.audifans.com/mailman/listinfo/s-car-list
>
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