this question is not for 3rd gen cars, just any car in general. while putting headers on a car, would it help performance, emissions, anything by moving the o2 sensor location closer to the catalytic convertor? seems to me that it would run cooler further down the exhaust it goes, while at the same time it seems like it would run hotter by being closer to the catalytic convertor. can someone give me input on this. thanks
p.s. i dont know if this should be in the exhaust catagory or should be in some other catagory, so move if nessisary.

 

Oxygen sensors should be placed as close to the exhaust port as possible. This is also true for catalytic converters, but sometimes it is difficult to run them up close to the engine. If you look most import transverse 4 cylinders, the O2 sensor is right at the head, and the converter is about 4-5 inches from the head. This is ideal, because both of these items need to be extremely hot to work properly.

 

but if the o2 sensor was originally located in the manifold about 8 inches from the head, how would it run if it was moved about 30 inches from the head in the y pipe just before the convertor

 

If you go with a heated O2 sensor it should be fine. The one-wire non-heated versions will not function properly that far down the exhaust. Would spend too much time in open loop.....

 

If you want to relocate your oxygen sensor that far away, Vernw is right, you will have to retrofit a heater sensor into your car. Here's a little background on oxygen sensors to help you out.

Most oxygen sensors, including the ones you're concerned with, are zirconia based sensors. They need to be at least 600 deg F to be operational. The zirconia element reacts with the oxygen present in the exhaust stream and compares it to the oxygen levels outside the sensor. The greater the difference in the two levels (rich condition) the more voltage is produced. The smaller the difference (lean condition) the less voltage. Voltage ususally ranges between .1v (lean) and .9 (rich), with .450 being stoich.

A typical 1 wire sensor has the sensor signal traveling through the lone wire. Ground is supplied through the sensor body.

Some 2 wire sensors use one wire for signal and the other for a ground. Other 2 wire sensors use the second wire for a heater power, and ground is of course supplied through the sensor body for both heater element and sensor output.

Some 3 wire sensors use one wire for signal, one wire for heater power, and the third for heater ground. Sensor signal ground is supplied through the sensor body. But a small percentage of 3 wire sensors use the third wire for signal ground and use the sensor body for heater ground.

And last,4 wire sensors use one wire for signal, one for heater power, one for heater ground, and the last for signal ground.


You can buy universal 2, 3, and 4 wire at part store like NAPA. You can also buy GM weatherpack connector shells and components there too. So you could retrofit a universal sensor in, supply the heater with power, make a connector for it, and it will look like a clean factory install. Then you could run your sensor aywhere you wanted (within reason).