Oxygen sensor wide range equivalence ratio (lambda λ) - Volvo D3 2011

Oxygen sensor 1 wide range equivalence ratio (lambda λ) - Volvo D3 2011
Volvo V70 D3 D5204T3 diesel, 2.0 5-cylinder, automatic transmission
Car Scanner ELM OBD2, profile: Volvo Platform 3 2008+
ambient temperature 8 C

Lambda ( λ )
λ (lambda), is the ratio of actual air:fuel ratio (AFR) to stoichiometry for a given mixture. λ = 1.0 is at stoichiometry, in rich mixtures λ is less then 1.0, and lean mixtures λ is more than 1.0.

For diesels the the limit is around λ = 1.25 (rich) and there is no limit for lean (as little needed to run the engine). When engine is idling the λ = 2 on my video.

You will notice that under DPF regen when engine is idling the λ=1.5-1.7.
"02S1 fuel:air" parameter can be used to control if DPF regen is taking place (check it when car is fully stopped and engine is idling). If it is less than 2, the DPF regen is ON.

The O2S1 sensor shows 0 for approx. 1-2 minutes, while sensor is heating up. The heated oxygen sensor is a broadbanded zirconium sensor and works with current control. The sensor consists of an oxygen sensor and preheating element. Reference air is taken from ambient air. Operating temperature of the sensor is around 700°C/1300 F. The heating of oxygen sensor starts at engine startup or at ignition.

A cold oxygen sensor will not provide a signal and the ECU therefore has a mode in which it will not use the A/F signal, called "open loop". When the sensor signal is being used, it is referred to as "closed loop".

The heated oxygen sensor provides the engine control module (ECM) information on the remaining amount of oxygen in the exhaust gases upstream of the catalytic converter. This allows the engine control module (ECM) to continually check that combustion is complete.

Wikipedia:
Air–fuel equivalence ratio ( λ - lambda)
Air–fuel equivalence ratio, λ (lambda), is the ratio of actual air:fuel ratio (AFR) to stoichiometry for a given mixture. λ = 1.0 is at stoichiometry, in rich mixtures λ is less then 1.0, and lean mixtures λ is more than 1.0.

There is a direct relationship between λ and AFR. To calculate AFR from a given λ, multiply the measured λ by the stoichiometric AFR for that fuel. Alternatively, to recover λ from an AFR, divide AFR by the stoichiometric AFR for that fuel.

Because the composition of common fuels varies seasonally, and because many modern vehicles can handle different fuels, when tuning, it makes more sense to talk about λ values rather than AFR.

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