Whereas the standard zirconium oxide narrow-band O2 sensor is fine for use on factory cars, many tuners find it helpful to use the faster and more precise wide-band sensor for optimum performance.
The wide-band O2 sensor was introduced in 1994 by Robert Bosch GmbH, the same company that developed the first O2 sensor in the late 60s.
An oxygen sensor uses an electrochemical substance to sense whether the exhaust stream is hot or cold. Because too little fuel makes an exhaust stream hot and more fuel cools it down, its temperature is an indicator of air/fuel ratio.
The narrow-band O2 sensors used in most cars have a limited amount of voltage output, which means they can only indicate if the A/F ratio is above or below the ideal 14.7:1 ratio.
The wide-band sensor (also known as the UEGO or Universal Exhaust Gas Oxygen sensor) has a much stronger voltage output and can accurately read air/fuel ratios from 7:1 all the way to 20:1.
Whereas a high/low reading is fine for factory applications, a tuner might want to raise or lower his air/fuel ratio above or below the 14.7:1 ideal for better fuel mileage or to compensate for altitude.
