How does a catalyst combine with the engine management system?
It is essential that a catalyst works to its maximum potential or stoichiometric point. Therefore there needs to be a feedback mechanism between the catalyst and ECU to make sure this happens. On most cars, a lamdba sensor (or Hot Oxygen Sensor) is positioned upstream of the catalyst to measure the amount of oxygen in the exhaust gas. The sensor develops a voltage of between 0.1V and 0.9V. A low voltage is measured in lean conditions (where the gas is high in oxygen and low in fuel) and a high voltage in rich conditions (where the gas is low in oxygen and high in fuel). As the exhaust gas changes from rich to lean and vice versa this is called the switch point. As this point is passed the sensor tells the fuel injection system to increase or decrease fuel.
