Question - Where to install wideband O2 sensor on stock exhaust

[Ghost001]

Hello,

I recently purchased an AEM gauge-type wideband O2 sensor and controller (30-4100), which has a Bosch LSU4.2 Universal Exhaust Gas Oxygen (UEGO) sensor.

I have the stock exhaust, and want to keep it that way, in order to pass California emissions.

I was wondering where I should install the sensor. Should I install it in front of the front cat? Should I install it between the front cat and the rear cat? Or should I install it behind the rear cat, where the stock rear O2 sensor is?

If I install it in front of the front cat, then it seems like it should be the most accurate. Also, this is what AEM recommends. However, AEM recommends that it be at least 18 inches from the exhaust port, and I'm wondering if it will be too close to the exhaust port if I install it in front of the front cat.

If I install it between the front cat and rear cat, then it will definitely be more than 18 inches from the exhaust port.

If I install it behind the rear cat, then I can use the stock bung, and I won't have to weld in a new bung. I can just re-install the stock rear O2 sensor for an emissions inspection.

Will it be accurate if it is installed between the front cat and rear cat, or after the rear cat? Is there a formula somewhere to convert the lambda to A/F if it is installed after one or both of the cats?

Finally, do you think I should remove the exhaust, in order to drill the hole for the new bung? Or is there a way to minimize the amount of metal that gets into the exhaust, which would allow me to drill the hole without having to remove the exhaust? Is it difficult to remove the exhaust?

 

[TacBear]

Hello,

I recently purchased an AEM wideband O2 sensor, which is a Bosch LSU4.2 Universal Exhaust Gas Oxygen (UEGO) sensor.

I have the stock exhaust, and want to keep it that way, in order to pass California emissions.

I was wondering where I should install the sensor. Should I install it in front of the front cat? Should I install it between the front cat and the rear cat? Or should I install it behind the rear cat, where the stock rear O2 sensor is?

If I install it in front of the front cat, then it seems like it should be the most accurate. Also, this is what AEM recommends. However, AEM recommends that it be at least 18 inches from the exhaust port, and I'm wondering if it will be too close to the exhaust port if I install it in front of the front cat. By the way, what is the "exhaust port"? Is it the hole at the back of the manifold? Or is it where the manifold is connected to the head?

If I install it between the front cat and rear cat, then it will definitely be more than 18 inches from the exhaust port.

If I install it behind the rear cat, then I can use the stock bung, and I won't have to weld in a new bung. I can just re-install the stock rear O2 sensor for an emissions inspection.

Will it be accurate if it is installed between the front cat and rear cat, or after the rear cat? Is there a formula somewhere to convert the lambda to A/F if it is installed after one or both of the cats?

Finally, do you think I should remove the exhaust, in order to drill the hole for the new bung? Or is there a way to minimize the amount of metal that gets into the exhaust, which would allow me to drill the hole without having to remove the exhaust? Is it difficult to remove the exhaust?

I got a Xcal 2 and turned off the rear cats (the rear O2 sensor only tells the computer if the cat is working). If you replace one of the rear O2 sensors with the WB sensor you will get a SES code and check engine light. I would drop the mid pipe and have the bung installed right behind the passenger side rear O2 sensor if you aren't going to turn off the rear cats.

 

[jstreet0204]

If you still have cats, the wb needs to be installed before them. Most widebands have a narrow band output that will allow you to simply replace one of the front o2's I would install it on the drivers side since that head does not cool as well and will usually end up being the leaner side.

 

[Ghost001]

Thanks jstreet and tacbear,

It looks like the gauge has a Nernst emulator, which provides the same output as a normal front O2 sensor. So I guess I'll just replace the front O2 sensor with the AEM wideband O2 sensor. Hopefully it's not too close to the exhaust port. It'll be nice, not having to remove the exhaust or weld in a new bung.

 

[Give Me TP]

Here's my wideband bung location

 

[Ghost001]

Here's my wideband bung location

It looks like your wideband is behind the rear cat.

Does it seem to be giving accurate readings? Do you have to mentally adjust the A/F to account for the fact that it is behind the rear cat?

 

[DBMSTNG]

It looks like your wideband is behind the rear cat.

Does it seem to be giving accurate readings? Do you have to mentally adjust the A/F to account for the fact that it is behind the rear cat?

he has the wideband bung in the right place. you are just looking at the picture backwards.

 

[Ghost001]

he has the wideband bung in the right place. you are just looking at the picture backwards.

Yes, I think you're right. Also, it looks like his exhaust is different than mine. My front cat and rear cat are very close together, but I don't even see his other cat in the picture.

 

[Ghost001]

After doing further research, it looks like most people say that the A/F measurement will probably be too lean, and sometimes too rich, if I install the bung after any of the cats.

So I guess I'll try to install it in front of the front cat. I think I should be able to replace the stock front O2 sensor, and then feed the Nernst analog output from the gauge to the stock front O2 sensor.

I found out that the exhaust gas temp should be < 1300 F, and the exhaust pipe temp should be < 900 F.

Someone suggested using 800 F "welder's crayon" to mark the outside of the exhaust from the manifold to the front cat, drive it hard, and install the bung wherever the crayon does not melt. This will ensure that the exhaust pipe temp is < 900 F.

I guess I could also install an EGT sensor right in front of the front cat, if I want to be sure that the exhaust gas temp is less than 1300 F.

Another idea was to use a sheet of copper as a heat sink, attached between the bung and the sensor.