Emissions Update: Understanding How Wide Ratio Air/Fuel (WRAF) Sensors Work Roanoke VA
(540) 853-2108, 001-2004
Rocky Mount, VA
(540) 992-2543, 001-2004
By Larry Carley
October 01, 2008
Instead of giving a simple rich/lean indication, wide ratio air/fuel sensors measure the "actual" air/fuel ratio. A WRAF sensor can measure mixtures that range from extremely rich to extremely lean (even straight air!). This ability allows the PCM to control fuel mixtures much more precisely, to handle much leaner fuel mixtures, to reduce emissions and to improve fuel economy compared to ordinary switching O2 sensors. WRAF sensors react much faster than ordinary O2 sensors, which allows them to monitor the fuel mixture from individual cylinders as each puff of exhaust blows by the sensor element. The PCM can then adjust the mixture for each cylinder individually to reduce emissions and optimize fuel economy.
Car makers also like the new WRAF sensors because it allows the use of thinner catalyst coatings (platinum, palladium and rhodium) inside the catalytic converter. With the soaring price of precious metals lately, this can add up to significant cost savings for a vehicle manufacturer that produces millions of vehicles a year.
Dates: 9/26/2013 - 9/26/2013