WB Instruments

[Brian L Massey]

On Thu, 12 Jul 2001 11:45:08 -0700 "Jack" <yoshi at hotpop.com> writes:

> The sensor is going bad on mine, but I think my friend left it on 
> the car and drove around with it on too much.

How do you tell that the sensor is "going bad"? I mean, what are the
symptoms? And how long is too much driving around?

> Anyone got any idea on checking accuracy on this thing? Probably 
> calibration
> gas? but I'm not too familiar with calibration gas, is there archive 
> on the
> list that I can look up?

Wow, at $1200+ a pop, I hope you would be able to return the sensor + box
for checking and calibration, can't you? Isn't this the one that Bruce
was recommending (same name Bailey)?

I'm from the mechanical side, not electrical, and have been trying to
study up on these devices, and still have some questions for those in the
know...

......1) I finally got straightened out with what happens when you have a
misfire, thanks to input recently. I assumed the readings would go rich,
but I see from further web reading, that even with diagnosis using the
oem NB o2 sensors, they also show lean if they see misfire. So OK, it
sees just the excess o2 and not the unburned fuel. But the stuff I've
read about these sensors says they *are* sensitive to unburned HCs too.
So does the extra air overwhelm the effect of the HCs? Buhhhhttt if this
is true, then wouldn't there be some level of misfire at which these two
would cancel out, and you wouldn't see the misfire? Seems they are either
sensitive to unburned HCs or not. What gives? I'm trying to visualize
what is happening here.

.....2)  Another situation I don't follow recently came up (well, it's
been mentioned a number of times actually). Thats when you are looking at
the WB output, and you supposedly can see "individual cylinders". As a
mechanical type, I think about the flow of gas out of the cylinders into
the exhaust pipe. Say all the jugs are firing at the same afr. OK, so
where does the variation in afr that the sensor sees come from? I mean,
the exhaust gases go down the tube not as slugs of exhaust surrounded by
lower afr, or *do* they? Sure there's a pulse of exh gas but how would it
differ from the afr that's in the gas pipe "off-cycle" already? The
pressure and flow drop off-cycle, but that doesn't mean the afr is going
change. Or does it? Unless there is some dilution (but how can that be?),
I would think unless the sensor is highly pressure sensitive and thats
what your seeing, the afr ought to not show any "individual cylinders". I
can see this happening at low rpm where you have some air in the pipe,
but at higher rpm, unless there is a leak in the exhaust to introduce
outside air, how could the sensor see an afr variation if all the jugs
are burning at the same afr? I don't get that one either! :(

Mind you, yes, I got the part where theres a misfire and you can see
that, but how is it happening that you see the boundary between two
cylinders firing if they are dumping the *same* afr exh gas into the
header, unless there's some background dilution happening off-cycle? This
is the part that has me confused. Where is the dilution coming from?
Anyone help me out here?

Thanks for all the stuff I've learned so far in the last couple months,
guys. Still a beginner I guess. Tnx.

Brian
________________________________________________________________
GET INTERNET ACCESS FROM JUNO!
Juno offers FREE or PREMIUM Internet access for less!
Join Juno today!  For your FREE software, visit:
http://dl.www.juno.com/get/tagj.
----------------------------------------------------------------------------
To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes)
in the body of a message (not the subject) to majordomo at lists.diy-efi.org