Wide Ratio O2

[garfield at pilgrimhouse.com]

On Wed, 18 Mar 1998 20:07:24 -0800, "Max" <maxboost at earthlink.net>
wrote:

>I know that the
>Horiba unit is 100% analog from a friend that has pulled the lid off of his
>unit.  He thinks that the key is limiting the current to the ion pump to
>less than 100 milliamps peak.  Another tidbit in talking to race teams that
>use the honda sensor for dyno work with big buck race ecu's, is that it has
>a narrower range on the order of 10.0:1 to 25.0:1 instead of the 8.0:1 to
>99.0:1 range that the $900 NTK one has.  The smaller range would also jive
>with the lower price. I think that this limited range is fine for the type
>of work that we would be doing.  Several people have tried using the honda
>sensor with a Horiba unit and found that after 20 minutes of operation it
>dies.  My friend thinks that the current to the ion pump is spiking higher
>than what it can handle and kills it dead.

Interesting tidbits. This is the second such input on modes of failure.
Remember the "fathead" that said it would take 5 yrs to figure out? He
disclosed two things: One was that the heater needs to be ramped up
slowly, lest the element crack from thermal stress; the other had to do
with "over-pumping" similar to what you've said above. One thing I do
know so far is that 100mA is WAY above the range I've seen/read/heard
for the sensor's pump currents (Ip) that I know about. The Bosch device
(NOT an LSM-11, but a thing they're calling their LSU sensor) in their
LA3 meter uses a range of +- 3mA, and I'm told the NTK is around -5,+2mA
for roughly the limited A/F ratios you mentioned above. So, yeah, if the
Horiba unit is swinging around 100mA when it tries to pump back to
stoich, it's really pounding on the poor thang.

Let's hope we don't kill too many of these chickens in the early stages
of testing; they're expensive road kill.

Every little bit of input on these guys helps immensely. I was
especially intrigued to hear the intel on the Horiba box being entirely
analog. If that friend that's lifted the lid would only do some
measurements with jumpers in some of the sensor leads, we would know
alot more! about any special control of the heater current, and also the
range of Ip it uses at various A/F ratios. Ya know what they say, give
em an inch and they want a mile? Guess I'm just as greedy, heh.

Garfield