Wide Ratio O2 meter

[garfield at pilgrimhouse.com]

On Wed, 11 Mar 1998 09:24:52 -0500 (EST), Frank F Parker
<fparker at umich.edu> wrote:

Hey Frank.

I have to agree with your summary of where we stand at this moment.
Thing is that there's alot of vital info coming out, and a couple things
to suggest below. But, that being said, if the Bailey meter is indeed
calibrated against Motec and NTK meters, at $500 it's looking better all
the time! B)

>The Bosch LSM-11 sensor:
> 1. There are 3 curves at 650, 750 and 900 C from which we can ESTIMATE
>    the transfer function to air fuel.
> 2. The sensor temp may be deduced from from the internal resistance of
>    the sensor which varies as follows:
>			650 deg C	120 ohms
>			750 deg C	 35 ohms
>			900 deg C	 10 ohms
> 3. Here is the major hangup. How do you measure the internal resistance
>   of the sensor without disturbing its output.

Couple things here. First off, I thot the heater elements had a
positive/non-linear R that INCREASED with temp. The data above shows
just the opposite! Harrumpph. Second, something odd about the difficulty
of measuring the R. Just be measuring/controlling the current, and
measure the V across the heater; compute the R from that? I must be
missin sumpin here.

>  8. When all of that is done, you really need to prove design on a dyno
>  comparing it to a Motec, Bosch or other calibrated meter. I have both
>  a Bailey meter which was calibrated on dyno against a Motec and a NTK
>  sensor/interface which I offer as cal standards for someone's design.

I keep reading that sentence above, and thinking, ummm, OK Frank has a
Bailey meter, but does he have an NTK sensor/interface also, or is he
saying his Bailley meter was calibrated against an NTK sensor/interface?
Help me out; english is my second language (fortran was first, I think;
and yes, I AM a fossil).

>NTK/Honda Sensor
>There is a SAE paper
>  but it is pretty general.

Ooooh, could you name names here? Title hints, SAE doc #, anything.

>It could be much cheaper if
>  NTK would allow competition in the marketplace-sounds even illegal!

Yeah, it sucks, but it's the price we pay for our system of rewarding
innovation. But even the best kept secrets often melt in an intense flux
of curiosity-rays. Give ya an example. I recently talked to a guy that
uses these sensors in industrial burner control. He gets em directly
from the my local Honda parts counter (at a nice discount, of course,
since he orders/buys 40 at a time, each month!). I figured my interest
in automotive was far enough a-field of his trade that he'd be willing
to talk to a fellow engineer. BZZZTT, wrong. But geeks are notorious
"leakers", so I asked him a few questions, and got some good poop outta
the conversation. Like, he says controlling the heater warmup gradually
is critical, cause the sensor internals are notorious for cracking and
failing if you don't. And he went on to tell me why I, as a lower
lifeform, shouldn't even BOTHER, because that ion pump, if you over do
it, depletes the oxygen ions in the Nernst cell to the point where that
cell can be damaged (maybe bull, but some insight nonetheless).

He finishes by telling me I have no business trying to figure this out,
cuz it's "just a hobby", and it would take me 5 years, anyway! Snee hee
hee. I almost laughed, but I may wanna try bending his ear again, so I
demured, discretion bein the better part of valor, and all that, ya
know.

>Hope above gives everyone the problems involved. Maybe someone good in
>design can come up with something. Flame suit on.

Hey, good summary methinks; why the doning of nomex? Geez, we don't
shoot messengers in this group, do we? BUT, since this technology has
been used in production cars from Honda for almost 6 yrs!!, it's gotta
be a secret that will yield somewhat to intense curiosity. Which is why
I'm thinkin of getting a VX service manual and checking out how it's
wired. Maybe some hints there. But that's mainly for curiosity/learning.
I DO think that as it stands now, the LSM-11 technology is more
tractable.

Garfield

P.S. Great topic, dudes. Maybe the egg will hatch yet.