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Question On 02 Sensor

MJTru

By MJTru,
in Engines & Forced Induction

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MJTru Mentor

MJTru

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Hi mates, So i understand when tuning with wide band i should turn O2 feedback off on the Power FC.

on low loads the 02 sensor is there in closed loop for fuel economy

full loads it's open loop.

so if i wrote a inj map how does the cars ecu know how to regulate the AFR's ???????????????? if a narrow band is useless for tuning.

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D_Stirls Veteran

D_Stirls

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Posted (edited)

The reason the narrow band isn't used for tuning is because it in only accurate around the 14.7:1 stoichiometric point; therefore it is no good for tuning as your are interested in the 11:1>13:1 area.

It is good for closed loop how ever as this is the area the ECU is interested in for economy.

The Wideband however is accurate over the whole AFR range as it has basically a linear relationship between Voltage output and AFR.

O2 Sensor Output

o2volts.gif

Wideband O2 Sensor output

lsu4_wb.gif

Edited by D_Stirls
MJTru Mentor

MJTru

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Posted
The reason the narrow band isn't used for tuning is because it in only accurate around the 14.7:1 stoichiometric point; therefore it is no good for tuning as your are interested in the 11:1>13:1 area.

It is good for closed loop how ever as this is the area the ECU is interested in for economy.

The Wideband however is accurate over the whole AFR range as it has basically a linear relationship between Voltage output and AFR.

O2 Sensor Output

o2volts.gif

Wideband O2 Sensor output

lsu4_wb.gif

I guess the only there question would be why didn't the factory's use a wide band.

thanks Mate.

MrStabby Grand Master

MrStabby

Posted
Posted

Narrowbands are basically a binary device. They see mixtures as simply lean or rich - there' no useable "its correct" value. The ECU then goes through a constant cycle of lean up the mixture until the narrowband says 'lean' then richening it up until the narrowband says 'rich' over and over again. You can see this if you watch the narrowbands output in via consult.

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