O2 Switch Point

[Sid447]

After looking through a fair few tunes,

there seems to be a great variation on the values in this table {B4105}.

Some run from 370mv to over 580mv
some from 450mv to 480mv

Is there any rhyme or reasoning to it?

[Chevy366]

Some believe that lowering the switching points can yield better fuel mileage , stoichiometric is 450 mv or for a narrow-band O2 that is the mv Bosh narrow-band and others use for Stoich , 14.7 or 14.8 . I guess you could say you can fine tune the narrow-bands with this .
Idea is to get closer switching points so there is not as much swing from lean to rich , rich to lean , or to trick PCM into leaning out for better mileage , so I hear .
Never seen any proof as to whether this actually works or not , just hear say .
So they say , lower number is leaner and higher is richer .

[WeathermanShawn]

I have tested various O2 switch-points with some success. I experimented with changing all values to .500, .550. and.600mv.

.500MV correlated to my average O2 switch-point..Using a wideband, it generally related to an average of ~14.7 AFR.

.550mv generally related to an average of 14.5-14.6 AFR.

.600mv (across all O2 switch-points) quickly responded in a SES check engine light...(O2 sensor malfunction..O2 voltages out of range).

I believe the theory in the differing O2 value switch-points at various engine airflow modes, has to do with the relationship of voltage as airflow increases. Higher voltages generally equate to richer AFR's, lower is leaner.

[The Alchemist]

It definately does change the AFRs.
We usually tweak them down to run a 14.7 on the wideband. Usually around 450.
However when doing cammed cars which like a slightly richer mixture, and I mean at cruise, you need to run up to 550 to avoid that lite throttle hesitation you can get sometimes.
Works a treat,
Mike

[Sid447]

Thanks,

to all three. I'm glad I asked!

I noticed the 2004 Pontiac GTO runs 450mv right through this table which made it odd.

Anyone know how {B4107} works and it's effect, relative to {B4105}?