Subaru OEM Rear Oxygen Sensor Subaru STi 2008-2021 | 22690AA850 CM 4 pad race clutch disc

4 pad race clutch disc paired with their ever popular sport pressure plate

more precise

designed around their famous Whiteline Plus series polyurethane bushings

aggressive exhaust note without excessive drone

Subaru OEM Rear Oxygen Sensor Subaru STi 2008-2021 | 22690AA850 CM 4 pad race clutch discFor your: Subaru STi 2008 2021 Rear O2 Sensor The rear oxygen sensor is used to sense oxygen concentration in the exhaust gas. If the air fuel ratio is leaner than the stoichiometric ratio in the mixture (i. e., excessive amount of air), the exhaust gas contains more oxygen. To the contrary, if the fuel ratio is richer than the stoichiometric ratio, the exhaust gas contains almost no oxygen. Detecting the oxygen concentration in exhaust gas using the