Special Functions – Lambda Removal

What are Air/Fuel ratio and Lambda?

air fuel ratio lambda

The stoichiometric air/fuel ratio is the minimum quantity of air, including just enough oxygen, for conversion of the unit mass of fuel into completely oxized products.

It depends on fuel composition and typical values are the following: 14,7 for gasoline, 14,5 for diesel fuel, 17,2 for methane and 15,5 for LPG.

Because the actual air fuel ratio used by the engine is greater, equal or smaller then stoichiometric air fuel ratio, an important parameter for defining mixture composition is the equivalence ratio.

Equivalence ratio = stoichiometric AFR / actual AFR

which defines the richness in fuel of the mixture. Its inverse is the air excess coefficient λ (lambda) which defines the richness in air of the mixture.

Lambda < 1: fuel rich

Lambda = 1: stoichiometric

Lambda > 1: fuel lean mixture

What is Oxygen Sensor and how it works

oxygen sensor lambda

As seen in the right figure, oxygen sensor in the exhaust gases are used to precisely control the mixture fuel/air ratio, which is supplied to the engine under the various speed, load and temperature operating conditions.

An oxygen sensor in the exhaust system detects if the engine runs with lean or rich mixture, providing a signal to engine control unit of the injection system to keep the AFR at its set value.

This trasducer is called oxygen sensor or lambda sensor because usually the air excess in a burnable mixture is indicated by means of the λ symbol.

What can we do with special function?

In case of exhaust system replacement of your vehicle we can disable downstream Lambda sensor and its DTCs.

Where can I find this special function?

If the vehicle and engine control unit are supported with this deactivation, you will find the Lambda sensor mark in column “special functions”.

Click here below and look for your vehicle: