Why not use a arrow band O2 sensor for tuning ?
Only a true wideband O2 sensor provides accurate AFR information outside the narrow range either side of 14.7:1. The narrow-band sensors are incorporated on OEM vehicles simply to tell the ECU if the AFR is on the rich side of 14.7:1 or on the lean side. That is all. They are not designed to provide reliable information down in the 10:1 – 13:1 range where we need to work with high output engines under load. One should note that GReddy, a highly regarded supplier of quality products, cautions strongly and repeatedly that one SHOULD NOT rely on their 4-wire sensor (one step down from a 5-wire true UEGO wideband sensor like the FJO) and associated Air/Fuel Ratio gauge for tuning purposes. They strongly recommend that a “laboratory spec” quality system be used. The FJO is an affordable system that provides the same level of accuracy as the so-called laboratory spec system.
