Gutted catalytic converter on my 3.2.... still need O2 sensor?

[billh1963]

When having the top end work on my '85 3.2, the catalytic converter was gutted since the internals were pretty much shot. (No smog inspections here).

Now that the catalytic converter is empty, does the O2 sensor do anything?

Thank you

[DaveMcKenz]

Originally Posted by billh1963

When having the top end work on my '85 3.2, the catalytic converter was gutted since the internals were pretty much shot. (No smog inspections here).

Now that the catalytic converter is empty, does the O2 sensor do anything?

Thank you

I think it depends on the DME. On my 928, my O2 sensor failed, ie. no voltage signal. This caused my car's brain to think it was running lean. That caused the brain to push the mixture toward rich to fix it, but with no O2 signal it just made it richer and richer. It fluctuated around AFR of 12. When I installed new O2 sensor, I was back to AFR's around 14.7.
Without a wideband O2 sensor, I would not know this. The car ran fine. I suspect that if you have a stock USA DME it will expect an O2 sensor signal, and your car will behave as I described above.
Maybe Sal or Ingo can relate their opinions.
Good luck,
Dave

[billh1963]

My next step is to install an AFR meter.

The O2 sensor is currently installed. However, with the cat gutted I don't know if it's doing anything useful.

[911obgyn]

85 DME uses the 02 sensor after warmup to adjust fuel delivery, or the air fuel ratio.

[SCadaddle]

I've got a gutless cat on my 82SC that is still using the O2 sensor as originally equipped. Still does what it is supposed to do with the mixture control.

[billh1963]

Thank you for the replies

[javadog]

Keep the sensor. No downside, plenty of upside.

JR

[OffCamber00]

Originally Posted by javadog

Keep the sensor. No downside, plenty of upside.

JR

This. I'm running an O2 sensor on my car w/ headers.

[chrisbruck]

I had same debate here after putting in a cat bypass pipe. I ran with the O2 plugged in and unplugged I couldn't tell you how many times. Idles much smoother unplugged, no real noticeable difference either way while putzing around town. I never measured the MPG's but should be slightly better with it plugged in. At WOT the O2 signal is bypassed. I have a Steve Wong chip and he recommended leaving it plugged in with my original USA DME so I did. Keep in mind the O2 is mounted ahead of the cat so it's working without reading what the cat is really doing like on newer cars.

I'd leave it plugged in.

[DaveMcKenz]

Like I said, I would keep the sensor. If you do get a wide band O2 sensor (recc. AEM) it will have a simulated narrow band signal output wire. You can then use just one sensor location to give AFR data, and provide fuel data to your DME so it can control the mixture. If you have two bungs in your exhaust system you can run your original narrow band O2 sensor plus the wide band and accomplish the same thing.
You can then experiment with the narrow band connected and disconnected just to see what it's doing.
Good luck,
Dave

[ischmitz]

The O2 sensor is always a good idea to have. Reports where it worsens running conditions are likely if the sensor is bad or old. In part throttle the 3.2 DME will adjust the mixture based on the sensor data and this is a good thing. If you want to remove the O2 sensor you need a chip that doesn't have support for it. Else the DME might screw with your mixture.

ingo

[DRACO A5OG]

Originally Posted by ischmitz

the o2 sensor is always a good idea to have. Reports where it worsens running conditions are likely if the sensor is bad or old. In part throttle the 3.2 dme will adjust the mixture based on the sensor data and this is a good thing. If you want to remove the o2 sensor you need a chip that doesn't have support for it. Else the dme might screw with your mixture.

Ingo

+1