WPSLPGExhaust Gas Oxygen (EGO) sensor Information

[Bernd Felsche]

Steve Schwartz tapped away at the keyboard with:

> I am going to jump in with my first post to this list. No Fear!

> This oscillation, duty-cycle, frequency stuff is IRRELEVANT.  This
> discussion lacks a clear question!  What are we trying to
> accomplish?  I saw mention of WOT performance in open-loop mode.
> Is this what we want the EGO sensor to tell us?  If so, indeed, we
> need only 2 LEDs - RICH and LEAN.  Note that this is in OPEN-LOOP,
> i.e. no feedback path to drive the mixture toward stoichiometric.

That's a good starting point IMHO. At WOT you might also just want
to make sure that you're actually fuelling on the rich side. So that
sort of closed-loop control (sanity-checking basically) could be
useful, especially if the ECU doesn't otherwise self-calibrate the
AFR on a modified engine.

It's not so much a matter of how rich, just the knowledge that
you're putting enough fuel into the engine is probably sufficient at
WOT for a road car. (Different ball-game altogether for aircraft,
boats, and the like I expect.)

> If, as in the example at http://www.cnnw.net/~fourty/uses.html, we are in
> CLOSED-LOOP, i.e. an operational EFI system, the oscillation is caused by
> the control algorithm varying the mixture to stay as close as possible to
> stoich.  The injector pulsewidth is constantly being adjusted to make the O2
> sensor cross the stoich point: leaner if too rich, and richer if too lean.

Is it not possible that at low speeds, that any scavenging effects
(valve overlap) *could* also cause the sensor to "blip" to lean as
it gets a whiff of fresh air?  Or is it too slow?

Specs have sensor response times as fast as 50ms (OK, that's not
really fast); others IIRC have typical response of up to 200ms.
Siemens were doing some research on this about 10 years ago. They
claimed that they could respond to the gas change due to overlap at
medium engine speeds (up to about 3000rpm from memory) if one sensor
was fitted per cylinder.  I haven't stumbled across further
information on the devices.

[snip]

> So, let me ask the following:
> 
> What are we trying to do?


-- 
Bernd Felsche - Innovative Reckoning
Perth, Western Australia
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