wideband 02
cool, was thinking about getting a wideband o2 before i get my car tuned. is there a certain type of WB i need to look for that can replace my stock O2 sensors, and also be a compatible input for my pcm to read.
I would say get a wideband which comes with a fitting that you drill a hole in the exhaust and weld in the thredded ring. What I done with mine was purchased some LT headers with a pipe that I can swap in and out the cats. In that pipe I welded the thread ring for the wideband. So have kept all my stock O2's, aldthough the PCM ignores the rear.
If you have removed the cats and have a stright through pipe, mount the wideband in that pipe.
You can put it behind the cats just fine and use it to tune. You must just take into account that the readings will be slightly lean compared to a WB placed pre-cat. Many dyno tunes are done with a wideband sniffer, so it's still possible to tune with one. I have the FAST single sensor version and it works just fine.
Cats don't have anything to do with trying to make the AFR look like 14.7. Three-way catalysts do three things simultaneously:
1. Reduction of nitrogen oxides to nitrogen and oxygen: 2NOx → xO2 + N2
2. Oxidation of carbon monoxide to carbon dioxide: 2CO + O2 → 2CO2
3. Oxidation of unburnt hydrocarbons (HC) to carbon dioxide and water: CxHy + nO2 → xCO2 + mH2O
These things have nothing to do with AFR, which is merely a ratio of combustion reactants (air and fuel).
If you check a wideband pre-cat versus tailpipe sniffer, you'll find that they are pretty close and very consistent relative to one another.
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I have run my WB behind the cats, the AFR dosn't seem to change as fast as before the cats.
As you say, Dyno's do it from the rear which is after the cats so it is a proven method.
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