Method and device for determining the combustion lambda value of an internal combustion engine

A control device for an internal combustion engine comprising at least two combustion chambers, wherein the control device, in order to determine the combustion lambda value of the internal combustion engine, being operable to:

• meter a predetermined first fuel quantity is to the first combustion chamber and a predetermined second fuel quantity to the second combustion chamber,
• reduce the first fuel quantity by a predetermined amount and to increase the second fuel quantity by the same predetermined amount,
• determine a first engine noise value, associated with the first combustion chamber, and a second engine noise value, associated with the second combustion chamber, and
• to determine the combustion lambda value based on the first engine noise value and the second engine noise value.

A system for the determination of the combustion lambda value of an internal combustion engine with at least two combustion chambers, comprising:

• metering means for metering a predetermined first fuel quantity to the first combustion chamber and a predetermined second fuel quantity to the second combustion chamber,
• means for reducing the first fuel quantity by a predetermined amount and increasing the second fuel quantity by the same predetermined amount,
• means for determining a first engine noise value, associated with the first combustion chamber, and a second engine noise value, associated with the second combustion chamber, and
• means for determining the combustion lambda value based on the first engine noise value and the second engine noise value.