The most common method uses a component called a Lambda or O2 sensor which permits the system to compare the amount of oxygen in the exhaust with the amount in the outside air, and then signal the computer telling it to adjust the fuel mixture. This is called "Closed Loop," and most fuel injection systems are this type. There are however still many motorcycles and other vehicles that are of the Open Loop design, which is simply a system which does not have an O2 sensor.