wideband tuning with cats?
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How much leaner are the A/F readings on a car if u test with a tailpipe 02 on a car with cats. I was told the readings are about .5 leaner, so if i saw 13.00 on the dyno it's actually 12.5 before the cats. Is it true?
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Can't say for sure since the O2's arent that accurate at WOT, but mine were reporting around .890 at WOT on the dyno and the wideband said my a/f was 13.0 so I feel like the wideband was nearly right on the money. Just my two cents tho.
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The .5 is what most people say a dyno run will be richer by when compared to the street. This assumes the wideband is before the cats. This has to do with the dyno not fully loading the engine. The difference between precat/post cat really depends on the exhaust system, engine setup. Whoever does your turning should have an estimate.
Gary
Gary