WB Instruments

[rr]

Individual cylinders can be detected as no two cylinders are at
the same exact AFR. The WB sensor also responds more quickly
than the NB sensor.

For good info on the NTK WB see: SAE #920234, Universal
air-fuel ratio heated exhaust gas oxygen sensor and furthur applications.

BobR.


Brian L Massey wrote:

> 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
> ________________________________________________________________

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