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Exhaust Oxygen Concentration vs Lambda

Diesel Tuning Fundamentals

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During the course lambda is mentioned as an air-fuel ratio measure.

I have a Mazda Skyactiv-D 2.2 and I can't get that parameter when logging. I can get Exhaust Oxygen Concentration parameter, which I get as percentage. Can it be translated to lambda value?

Hello no you cannot do this lambda is a voltage and you can change that to afr but not a percentage of concentrated oxygen

Regards Ross

I think it can be calculated. You may not have all the inputs for the calculation (gas analyzer required), but here are some clues if you want to learn:


BTW -- free air calibration of an O2 sensor is just setting the reading for normal atmospheric oxygen concentration (about 21% iirc).

So can this Exhaust Oxygen Concentration parameter provide any valuable information for tuning?

On some engines we are able to calculate fuel mass injected to a lambda number but must say we have all correct data on them and know how to alter the injection timing as well due to chance in injection angle that comes with altering injected fuel mass. But for most it will be trail and error as for what a lambda number your engine can run under different load conditions as this is not a constant. Remember a diesel is not a petrol engine where AFR tells a better story.

I found that there is a wideband O2 sensor, but output I get from it is in mA (min value is 0.13 mA and max is 2.64 mA). There is also impedance value (28 ohm).

Can that be converted to lambda value?

Sure most manufactures have a calibration table. For example, here is the data sheet for the Bosch LSU 4.9 that contains that info for that sensor:


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