A/F ratio concern/question

[mikel]

Those A/F #s you listed are way off.
The values you saw on the bone stock C6 should be more like 11.7-12.0:1 at WOT...NOT 13.anything.
I'd say find a different dyno.

Thanks
Mike

[01Z]

It's not always an easy thing to place a bung before the catalyst. On my LS1 manifold the converter is directly after the collector. The configuration of the manifold puts the the collector flange an inch from the end of the primary tube. Then each converter is about one inch from the other side of each manifold flange. Because the factory manifold is cast, it would be difficult, if not impossible to put in a bung let alone make it accessible for a sensor. With my car, I need to use the already cast-in narrow band sensor bung for the wide band. This takes some doing as I have to simulate the narrow band sensor to the PCM at the same time I'm reading the wide band.

Also, IronHorse could be right about the 1 - 1.5 lean reads but I thought it was only supposed to be a tenth of a point or so after a cat. That the reading takes place so far from the source introduces a big variable. The narrow band sensors are always very close to the collector for a reason. Also, oxygen levels must change somewhat after a converter, otherwise there would be no point in the after cat sensor on OBDII cars.

I would think a speed shop would have the means to correct the a/f ratio reading in regard to it being after a catalyst.