TBI 3-wire O2 sensor upgrade, no open loop

[lionelhutz]

I believe you are mistaking a narrowband O2 sensor for a wideband O2 sensor. You use a separate wideband O2 sensor for tuning.

[Xnke]

Basically, 1 wire O2 sensors have to be within so many inches of the head-they're great for stock manifolds and the like because they rely on the exhaust gas to heat them up and keep them at temperature. Once you go to a long-tube tubular header, the exhaust gas temperature drops too much to reliably heat the sensor-so you go to a 3-wire or 4 wire sensor, incorporating a heater element to keep the sensor hot enough to function.

Outside of the added heater, and the separate signal ground for the 4-wire, there is zero difference between a 1 wire, 3 wire, and 4 wire narrowband O2 sensor. they function identically to each other, and are useless for open loop tuning.