O2 sensor question - how it works

[Bernd Felsche]

nacelp writes:

>> Garfield Willis writes:
>> >factory-set "parallel trim value" in the ECU circuitry (which doesn't
>> >have the luxury of doing a free-air calibration like we proformance
>> >users can), and as such, varys widely for only slight (15% overall)
>> >changes in the sensor calibration itself. But there's nothing "typical"
>> >about the cal resistor value. It varys widely.
>>
>> Why can't the ECU do a "free-air" calibration on over-run?
>> (Say after 50 revs of "purge".) Just curious.

>Some wall setting does occur from reversion.

What's this "wall setting" thing?

Do you mean wall wetting?
Isn't that likely to have evaporated after 50 revs or so?

How does reversion apply to a steady-state over-run condition?

Sorry to ask so many dumb questions...

>PCV valve
>Charcoal canister.

Certainly worth taking into account.
But I thought they were controlled from the ECU nowadays.
Not like it's a 1980's antique. :-)

Even then; the charcoal cannister won't usually discharge until
there's a significant throttle opening on the older systems (usually
determined by manifold vacuum) otherwise the idle becomes unstable
due to excess fuel vapours from the canister. I'm not sure exactly
how that applies to over-run. There's even more manifold depression
on over-run so any vacuum-servo valve won't be opening.

Anyway, it would make sense not to feed any fuel at all as the spark
is often suppressed on over-run as well; it'd just screw up your HC
emissions.

>Are all contibuting to emissions even thou the fuel may be off during
>overrun.

-- 
Real Name: Bernd Felsche
    Email: nospam.bernie at perth.DIALix.com.au
     http://www.perth.dialix.com.au/~bernie - Private HP
----------------------------------------------------------------------------
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