What is the target lambda reading for my vehicles engine?
It depends. There are many factors that can affect the air/fuel ratio for your vehicle. Particularly at idle, many engines will show a lean lambda (lambda of greater than 1) when this is perfectly OK. For example diesel engines run this way. Other engines, at low speed experience “valve overlap” where the intake valves are opening while the exhaust valves are closing. This will cause oxygen to “leak” into the exhaust, raising the observed lambda. However high lambda values can also signal that the oxygen sensor is not fully immersed in the exhaust gases. For example, we have seen lambda measurements on motorcycles yield false lean readings due to the low exhaust pressure. By covering the exhaust, and eliminating outside oxygen from crossing the sensor, accurate lambda readings were gathered. In general, however, optimum horsepower is achieved between 0.85 and 0.90 lambda (12.45 AFR to 13.2 AFR using regular gasoline).
