WB O2 and EGT compensation

[Bruce]

If you'd care to read the archives some there is data aready there about
this devise.  BTW, it uses the same sensor as the DIY unit.  So they have
the same sources for error, as a function of the actual sensor's design,
the temerature *error* will/could be thought of as the EGT has raised the
sensor temp higher then it's operating temp..  Yes, there is some variance
from post to pre turbo, but since the proper tuning is what AFR for best
performace (as opposed to tuning to get a specific AFR), the *error* is
mute.
Bruce

From: "David Harris" <dharris2112 at yahoo.com>
> Since Kevin brought up WB O2 GP's. I thought I'd
> mention that there is a GP for a complete unit made by
> FJO (a company in Canada). I was going to join that
> until I found out you guys had been working on a DIY
> version.
>
> One thing I was curious about was the EGT temperature
> compensation. The reading on UEGO's has a temperature
> dependent variable. I forget which way it goes but I
> believe the UEGO reads richer than reality when EGT's
> increase. This is why many WB O2 meters include an EGT
> probe to get accurate readings.
>
> I had asked FJO about how they obtained such good
> accuracy without an EGT probe. Here is their response:
>
> "While it is true that the UEGO sensors are somewhat
> exhaust gas temperature dependent, this effect can
> be minimized by several techniques, some of which use
> the characteristics of the sensor itself. In fact,
> using an EGT probe to compensate would prove to be
> a less effective solution as the probe would not
> accurately reflect the UEGO sensing element
> temperature. In our wideband controller we have
> employed techniques to reduce the effect of
> temperature-induced error to less than 0.05 AFR with
> an overall accuracy of better than 0.1 AFR.
> Unfortunately, I can't go into detail on exactly how
> this is achieved as this is proprietary information."
>
> Since the current DIY solution is analog only, I
> assume that we will have the same temperature induced
> error. I'm guessing that FJO characterized the sensor
> against a "real" WB O2 setup or came up with a
> compensation curve vs temperature.
>
> So what do you guys think they did? What about their
> claims of accuracy? Do they sound feasible?
>
> Dave


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