Will a wide band o2 sensor have correct readings at tail pipe with cats???
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Will a wide band o2 sensor have correct readings at tail pipe with cats???
Close enough. All the tuning shops use tail pipe sensors. Usually only the permenant installations go before the cats.
I have found with my LM-1 WB02 that readings after the catalytic are
nothing like the readings taken before the catalytic.
This is especially true with 2 and 3-way converters.
The readings I have taken differ between 1.1 to 1.4:1 between light load,
and wide open throttle.
In the end, you want to tune for what the engine needs, not what the
sensor reads. If you have access to a dyno, or better yet a race track
tune the engine for best MPH through the trap, or best average HP over
the RPM band used.
if you go to a dyno they will ask if you have a cat. if you dont they use the tail pipe if you do the weld in a bung before the exhaust. so no you cant use it in the pipe with a cat if you want to be accurate.
We try to use the O2 in the header pipe prior to the cat for accuracy by removing the OEM sensor and installing our wideband and forcing OL operation until we have the air model complete.
When at the tailpipe it is influenced by pressure pulses bringing ambient air into the tailpipe, worse at low speed and more so with more cam overlap.
Post cat readings are not reliable until the cat bed becomes saturated.
Most guys swag the readings to the lean side to realize richer in cylinder mixture.
Michael