How do O2 extenders work?

[donnylynn]

As I understand them, the O2 extenders are only moving the tip of the sensor out of the main exhaust flow, but it is still exposed to the exhaust, since exhaust gasses will still circulate up into the extenders. So how does this make the sensor think the O2 levels have changed?

[Painless]

Keep in mind the amount of pressure in the exhaust, gas will still get up into the extenders but not as much as in the main exhaust stream.

[donnylynn]

I assume the sensor seals the end of the extender, otherwise there would be an exhaust leak. I am assuming that after a few seconds that that he O2 levels around the sensor are the same as in the exhaust stream. So how do the extenders affect the output of the sensor??

[Super Fuel FX]

Not as much of the sensor is exposed to the exhaust gasses. By using an extender, you pull the tip (sensor part) part of the way out of the exhaust stream, reducing the gasses that are able to be monitored. Think of it as surface area.

[HALS-GUNSMITHING]

If your generator stops putting out how will this effect the vehilce? Will this cause damage by leaning too much?

[Keith's Garage]

When the O2 is pulled out of the exhaust it creates an air pocket around the sensor. When the exhaust flows by, it creates a tiny vacuum around the O2, this lack of oxygen is what shows the ECU that it is running rich.

If the extenders work on your vehicle, and your generator goes out, this could lead to engine damage depending on how lean your vehicle is running. I think it would probably take a LOT of time for the damage to occur.

[Super Fuel FX]

Thanks for the correction Keith. Excellent explanation!

[tinkit]

Do you need a map/maf sensor or a efie if you use the o2 extenders only?
Thanks in advance Tinkit

[donnylynn]

Thanks. That explanation makes sense to me. Lower pressure area means lower quantity of O2 atoms in absolute terms even though the ratio to other atoms hasent changed. It also explains why the extenders work on some vehicles and not on others. If the angle of the sensor mounting into the exhaust pipe is at the wrong angle, you wont get the low pressure area around the sensor. The extender functioning properly depends on a "venturi effect" of the air flowing past the end of the extender creating a vacuum.

Please correct me if I am wrong.