Wide Ratio O2

[garfield at pilgrimhouse.com]

On Sat, 21 Mar 1998 16:48:54 -0500, "Bruce Plecan" <nacelp at bright.net>
wrote:

>Boy, that sounds really neat.  I'd like to thank all involved so far.

Frank be yer main man; send posies his way. At this point, I'd just like
to make sure he doesn't meet with an errant dumptruck before this is all
over.

>  "My" goal is looking to somehow use this as a sensor for a feed
>back device.  That way it would maintain a fixed WOT AFR.  What
>I'd like to do is possibly use a set of LM1949 (I think it is), as a new
>output stage, and use the oem ecm as the "base pulse width" and
>modify that useing feed back from the WRO2 sensor. 
>  Maybe as simple as using the output from a LM 3914 to a series 
>of resistors for a variable rate monostable 555 to run the final drive.
>  What does that sound like?.  Good/bad/silly/doable?.

Oh, God, I think we've just heard a NEW application for an LM3914! But,
hey, seriously, why not? Not bad level of integration, a bunch of op
amps (10!) with linear threshold tree, ten constant current drivers,
whee! OK, lemme see about this; those outputs are like low-side current
limiting drivers, with the current limits gang-adjustable between say
2-30mA for each out. So you basically have a 10-step linear
voltage-dependent low-side current ladder. Uh, yeah, I think you could
easily use this to control the timing capacitor charging current on a
555-like device. Kinda scary, huh? And ya know, the 3915 does the same
thing logarithmically, if you wanted to get really carried away. Like I
always say, there ain't nuthin so upwardly mobile as a free electron.

>Now, for the $64,000 question.  Would ionization from a detonation
>problem, screw up the ion pump, or the sensing of this device??.
>Or would one just have to use a OEM type knock sensor to prevent
>this.

Uh, I think you just wandered into the o-zone. We'll let the electrochem
guys have their fun, but I'm pretty sure the ions the O2 sensor is
dealing with are IN the solid electrolyte material of the sensor, and
their brother ions that might be in the exhaust gas have been summarily
accounted for in the theory. So I think you can safely
"compartmentalize" these diff. "ion" issues. By the time the exhaust gas
gets out to the O2 sensor, I'll bet most of them combustion chamber ions
have all found their electrical partners by then. At least, I hope so!
Tweak me if I'm wrong.

>At this level now, which sensor are we talking about?.  Is all this theory
>so far just specific to one brand of WRO2 sensor?..  Is the Honda 
>OEM one still in the running?. 

Well, the particulars have fallen upon the NTK/Honda sensor,
essentially, if you're talking about raw numbers and practical designs,
yes, but the theory I imagine applies to any sensor built along the
lines of a 5-terminal, two chamber (actually 3 if you count the ref. O2
cavity) gizmo, of which family even the Bosch LSU sensor seems to be a
member. Dunno yet about that ND/Toyota 4-terminal device.

Bottom line practically speaking is that the last verbatious post was
assuming using the stock Honda sensors available for $120-130US at any
Honda dealer. Yup.

>  And I understand this we don't worry about where this is mounted in
>the exhaust stream.  So even downstream of a turbo is fine.  Is a
>WOT EGT of 1400-1500dF a problem?

Oooooh, another gigantic leap. Actually, good point; NO, unhappily the
NTK UEGO sensor has some temp limits where it stops functioning, that
will probably mean needing to carefully position in the case of mondo
hughmungous turbos. You certainly can't put them right at the dragon's
belch, cuz they have a functional if not failure limit of around
1600degF (900 C). And the +|- 0.2 AFR slop I mentioned assumes a range
of 400-1300degF (200-700 C) [mind you this is not a functional limit,
it's just the range they measured this accuracy within]. I've heard (all
yous guys know more bout this than me) that during dial-in of turbos,
you can easily get EGT excursions above 1600 near the output, especially
on the Rotary engines. Soooo, might do to plan on EGT probing your
exhaust system to find a sweet spot, in these eXtreme cases. I dunno,
I'm really outta me depth here. Just keep your distance from the
dragon's mouth is my suggestion.

All these gloomsNdooms caveats aside, I would think 900degC is a pretty
all-right upperlimit to work with. Just means with turbos, you gotta be
careful more, daring less. Thas all.

>Sorry but I've been trying to keep up but at times ya'all still get over my
>head..

Uh, huh, very modest and all, but it doesn't sound like you're missing
any major hoorahs. Are you sure your hat's focal point is adjusted
optimally? Cosmic Stupid Ray flux is intended for our good, since our
wit when unchecked usually gets us into trouble. Thus hat wearers are
actually part of a New Age of benign intelligences. How else could this
group be so, um, laid back. Heh.

>TIA  Bruce  Imagine, wearing a Cone Shaped Hat, and a min.
>                    emission level hot rod.....  Low emission would
>                    be pushing it..

Not to worry; the EPA at present doesn't regulate Stupid Ray emissions.
B)