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!cats = more lean?


TurbochargedBerserker

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I ran a couple of logs today (first since the cats came off) and it seems I am globally more lean in closed loop. I guess this makes sense since the exhaust is flowing better, but it was a pretty big change (from -2 or -3 to 0 or 1).

 

I seem to remember hearing that this wasn't a real lean condition but rather that the o2s just think its lean, but being a techie, that makes little sense to me -- o2s are just switches, right? The exhaust stream either has more unburnt fuel or less, removing the cats doesn't effect that (the o2s that read ltfts are upstream of the cats).

 

Anyway, I adjust the VE globally to see what's what. Any comments welcome.

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I wouldn't figure that the 02's are getting fooled because they are pre-cat anyway. I don't think that the loss of a little bit of backpressure would enough diff in exhaust gas temps either to fool it. I figure that it is probably just that you have increased flow, meaning a bit more power. Are you hitting any higher boost, even marginally?

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the slight change in airflow will cause a bit more of a lean condition, but the 02's also are likely running at lower temps now which can show more on the lean side. did you take out the c.o.t. also when you got rid of them?

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