Re: O2 sensors

[Orin Eman <orin@wolfenet.com>]

> "Established fact"? By whom, and how? By what standards?

Seem to recall from someone reading the numbers stamped on the
side of the sensor...

> Are you aware, that in addition to 1 and 3 wire units, there are 2 and 4 wire

2 wire is a 1 wire with the ground connection brought out separately
rather than just bonded to the case.  Similarly for 3/4 wire.

> sensors. Did you know that some sensors are rated for 30K miles, some for 50K,
> 60K and 100K? Have you ever wondered why there are multiple numbers of 3 wire

For the same car?  Turbo cars tend to eat them up faster.  Wouldn't be
surprised if the absolute same sensor is speced for 30k miles in one
car, 50k on another etc..

> sensors specified for various years and models of Audis? Wouldn't it have been
> cheaper for Audi to specify a single design/part number? Without further

Different length of wire and/or connectors makes most of the differences.

> investigation, I would wager that each number specified corresponds with a
> different emissions system, i.e., CIS, CIS-E, Motronic, etc.

Aging effects and temperature account for more variation.  The basic chemistry
leads to the curve given in the Bosch books.  I've disassembled some of
the ECU code.  It just looks a voltage in one of three ranges - continuously
around .45 V (in which case the sensor is dead), above this range
(rich) and below this range (lean).  That's all.

> I'm convinced, having worked on Lambda systems since 1976, that it's wise to
> stick to the products specified for each application. And that's what I am
> going to do, both on my own cars, and those of my customers.

My car is happy with the GM application Echlin I put in... had the classic
symptoms of a dying O2 sensor - slow transitions, poor gas milage.
Back to its normal gas milage afterwards.  It _may_ age faster than
a Bosch, but new out of the box, it behaved just as expected.  Really,
look at the curves vs temperature... without knowing EGT, the ECU doesn't stand
a chance of using a regular 1,2,3 or 4 wire sensor for anything but
rich/lean detection.

John, I do see your point - maybe the generics age faster - and
that uncertainty is enough for some... For me, give me the generic
and when my dancing lights O2 sensor monitor gets slow and the
gas milage goes down, then I'll worry.

BTW, there are 5 wire sensors used in some Hondas too.  These are true
wide range sensors when driven by the correct circuitry... do a patent
search on wide range oxygen sensor or similar for some good bedtime
reading.

Orin.