If the Lambda sensor can accurately control the mixture, why is accurate fuel mapping required?
In an ideal world, it would be nice to allow the management system to work out its own fuelling maps. Accurately calibrating the fuel map is an extremely time consuming operation. There are a couple of reasons why accurate fuel mapping is still required. Firstly, the Lambda sensors used on production vehicles are what is known as ‘narrow band’ Lambda sensors. This means that they only have a small operating window either side of the optimum setting. Once the fuelling is outside of this, the sensor cannot measure the mixture, and the management system is unable to make the necessary adjustments. Secondly, there are a number of occasions where the engine performance will be improved by not running at the Stoichiometric point. Under full load conditions, more power is produced if the mixture is slightly richer, and on the overrun, fuelling is often switched off completely to save fuel, and increase the engine braking effect.
