[Diy_efi] WBO2 and AFR

[Tim Marsteiner]

So, are there ever times when ignition is knock
limited such that combustion is not complete? 

And would this tend to cause "erratic" WBO2 A/F
readings? 



--- Adam Wade <espresso_doppio at yahoo.com> wrote:

> --- Tim Marsteiner <tmarstei at yahoo.com> wrote:
> 
> > As you retard ignition the AFR reading gets
> leaner!
> > If you tune with retarded ignition you will end up
> > being rich. This is not insignificant!
> 
> *ding*  Give the man a cigar.
> 
> An O2 sensor, WB or otherwise, gives partial
> pressure
> of O2 in the exhaust.  Retarding the ignition timing
> means less complete combustion (when retarded
> notably
> from MBT), which means more HC *and* more O2 in the
> exhaust.  If you're just measuring partial pressure
> of
> O2, then your O2 sensor will "tell" you you just got
> leaner, when this is not, in fact, the case.
> 
> The key to using data usefully is knowing what they
> will (and will not!) tell you.


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