O2 sensor response times- catalyst

[Espen Hilde]

I am just guessing here but I think its something we are missing.
When there is o2 in the exhaust we dont have to "pump" at all?
Maybe the thing is to measure the wide band in 2 ways to get the wide
range, first as a usual o2 sensor giving mvolts and swich to current 
when over the stoic aria.
Espen

> >>Just for anyone interested, in the NTK wide ratio sensor manual it
> >>states that the O2 "pump" current varies from -12.5 to 12.5 mA, the O2
> >>sensor is biased with a 25 uA +/- 3 uA current (the sensor output
> >>voltage (450 mV for stoich) is read on top of that).  The heater
> >>voltage is 10.5  +/- 0.5 volts.  I still don't know how you go from
> >>pump current to AFR!
> >
> >This is derived from the new Bosch SI Engine Management book:
> >
> >The -25 mA would correspond to approx lambda of 0.7, +25 mA to
> >approx 2.2. 0 mA is lambda = 1.
> >
> >You should be able to fit a curve through those three points.
> >
> >Not that it's not often useful to have a lambda of 0.7 - that's way
> >more rich than any steady-state running would require.
> 
> Argh. All I'm at liberty to say to the immediately above is "BZZZT".
> Remember I warned ya, these devices are both spendy and VERY easy to
> destroy by over-pumping or mis-pumping (pumping in the wrong direction).
> It's referred to in the trade as "blackening" the sensor. Others who
> have worked with these sensors in industry and have no commercial
> interest in them as I do, will also confirm this. I shit you not.
> Besides, I'm surprised that a Bosch book would even mention an NTK
> sensor, but those numbers aren't even close.
> 
> BTW, 0.7 lambda is roughly 10AFR. WOT turbo engines can/will fuel in the
> 10'sAFR during transient enrichment under heavy load, so altho this
> isn't "steady-state running", being able to see and measure these rich
> excursions isn't so far afield. And carb'd engines will lean-misfire and
> even backfire, if idle-jetting combined with a rapid undamped
> throttle-off runs the AFR to above 17-18, so measuring to this lean,
> again altho not "steady-state" still can be important, too.
> 
> I won't be saying too much more about tech stuff concerning these
> sensors; as an instrument vendor I'm just not able to participate the
> way I'd like to, without raising suspicions of bias. C'est le vie. Just
> caveat your emptors, doods, and save at least one good, pristine,
> virgin, unmangled sensor for EGOR, will ya?
> 
> TTFN,
> Gar
> 
> 
>
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