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Oxygen Concentration %

Practical Diesel Tuning

Relevant Module: Required Sensors > Air Fuel Ratio Sensor

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Is oxygen concentration % the same as AFR?

They are related, but not the same thing.

The oxygen remaining in the exhaust gases is measured by the lambda sensor, which gives a voltage and that's used to give an AFR or lambda value.

A lambda value of 1.0 is stoichometric (sp?), which in theory is the ideal balance for the fuel and oxygen to be fully used, with a higher values being leaner, and a lower value being richer.

This is where it gets a bit tricky, as for the same lambda value, different fuels will have different AFRs, as their chemical mixtures are different. This is especially confusing with, say, an alcohol blend having a true AFR of 8.0:1 with a lambda of 1.0, but a standard meter that hasn't been calibrated for the fuel will still read 14.7:1, which is the AFR for petrol/gasoline. For this reason, working with different fuels, it's good practice to stick to lambda values rather than AFRs.

This may be useful to get the idea.

AFR and lambda comparisonAFR and lambda comparison

On my data logging i get oxygen concentration in % is there a way to use this to determine AFR or Lambda?

Strange, that's not a very useful metric for vehicle tuning - it is specifically for vehicles, rather than a generic atmospheric gas analyser?

In the meantime, https://wbo2.com/sw/percent-o2.htm and https://www.researchgate.net/post/How-to-calculate-oxygen-percentage-from-lambda-value - the second is less technical, but you will need to re-write the equation.

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