Re: More on the lambda

[Robert Myers <rmyers@inetone.net>]

Brett,

Properly designed ceramic materials can be remarkably permeable to gases.
I haven't taken a close look but if the exterior surface of the ceramic is
not glazed (and I don't think it is) then the ceramic will permit exhaust
gases fairly quickly to reach the sensor electrode while keeping the
temperature from fluctuating too severely while providing physical strength
and some protection for the electrode.


At 11:52 PM 6/16/98 -0400, you wrote:
>>downstream and clog the mufflers.  Meanwhile, all that heated raw fuel makes
>>for neat flames at night, which combined with red hot turbo temps, fries the
>>O2 sensor, as well as the muffler filling.  Sound expensive?  For both the
>
>>to fuel mixture.  Certainly agree that this is a crude weapon, given an OBD
>>system.  But, I also agree that a EGT is slow, in fact, maybe too slow to be
>
>OK, here's a couple things I'd like explained.  I just took apart my O2
>sensor completely.
>
>For those of you that haven't taken one apart, if you disassemble the
>sensor, there is a very thin rod that has 3 gold-plated areas for the
>heater+sensor.  These connectors then mate with three connectors that go to
>the outside of sensor.  A cover goes _over_ the rod and _seals_ against the
>case of the sensor.  I don't think the cover has anything in it, because I
>don't see any conducting areas on it.  Looks just like a piece of ceramic.
>
>This means that the sensor rod is COMPLETELY sealed from exhaust gas, which
>would lead me to conclude that O2 sensors are nothing more than high
>temperature senders.  I think the "heater" is to simply help get the O2
>sensor up to about-egt temperatures quicker.  You can see the heater
>element in the thin rod...it zig-zags the length of the sensor all around
>it.
>
>What this doesn't explain is why the sensor is so sensitive to
>contaminants, since the thing has that nice cover.  It also doesn't explain
>why the sensor would "swing" very much; that ceramic element would take
>some time to heat up+cool down.
>
>Can someone help me out here?  I'm confused.  Is that "cover" really the
>sensor element?  That seems impossible since there aren't any electrical
>connectors!
>
>Brett
>
>------
>Brett Dikeman
>brett@pdikeman.ne.mediaone.net
>~)-|
>Hostes alienigeni me abduxerunt.  Qui annus est?
>Te audire non possum.  Musa sapientum fixa est in aure.
>Ita, scio hunc 'sig file' veterem fieri.
>------
>
>
>
>
___
   Bob
*******************************************************************
*  Robert L. Myers  rmyers@inetone.net    Home 304-574-2372/1166  *
*  Rt. 1, Box 57,  Fayetteville, WV 25840 USA      WV tag Q SHIP  *
*  '95 S6  Cashmere Grey                                          *
*******************************************************************