Wideband after cats reading

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Aug 2, 2006 | 07:01 AM

PREDATOR-Z

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From: BFE

Wideband after cats reading

Hello,

I would like to know how much leaner does a wideband read if it is after cats.
I put mine (Dynojet) in the merger of the Y pipe. Cats are Random Tech
The wideband is reading a bit lean but I get no KR.
Spark plugs look good too.

Could it be .5 leaner VS before cats? Anyone with experience in such matters.

Thanks,
Mark

Aug 2, 2006 | 07:39 AM

Billiumss

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I have seen about a .2 difference on average on the cars that I tuned...

Aug 2, 2006 | 08:07 AM

dynocar

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Very neglagible at WOT, approx .2 leaner to 0 from low to high RPM.

Aug 2, 2006 | 09:50 AM

PREDATOR-Z

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From: BFE

Thanks, guys, I guess I need to richen it a bit.

Aug 2, 2006 | 04:34 PM

ringram

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I did 45min on the dyno and average was 0.5 different for me.

Aug 2, 2006 | 10:24 PM

eb02z06

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If it seen it range by as much as a full point-I will never trust the tailpipe sensor again.

Aug 3, 2006 | 08:11 AM

dynocar

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It could be argued that the further back you monitor A/F, the more accurate, because pressure (exhaust backpressure) skews a wideband's reading by a few points (10ths).

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Aug 3, 2006 | 12:15 PM

vette.se

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Quote:

Originally Posted by PREDATOR-Z

Hello,

I would like to know how much leaner does a wideband read if it is after cats.
Thanks,
Mark

I've noticed that standing still idle the A/F could be anywhere from 15.1 to 16.5 because of fresh air entering the exhaust system, especially if the muffler have one exit going to two pipes (this is with a tailpipe sniffer) but at speed (cruising) I get normal readings at exactly 14.7 so at cruise no difference in readings. At WOT I've only seen a difference of 0.1-0.2 between a tailpipe sniffer and mounting the sensor before the cats - I do not know why it's a difference, maybe someone with more knowledge could chime in