Stock o2 sensor needed if running AEM Wideband?

[marcs23]

I just recently bought a 97 civic ex with a B20/vtec swap with a turbo. My question is the previous owner does not have any o2 sensor connect and it also does not have a cat. There is an AEM wideband gauge that he told be was welded into the exhaust pipe and wired to the ECU. The ecu is chipped and tuned on chrome but it was last tuned like 2 years ago. I am getting a hondata S300 in the few weeks. I want to have a magnaflow cat installed but I do not know if I should get one with the o2 bung and put an o2 sensor in it. The connector is there, but if the ecu is getting the A/f reading from the AEM wideband, I would think if would be pointless on installing an o2 sensor in the Cat. would do you think? thanks

 

[XpL0d3r]

Is the cat required for you to pass emissions? If not, I wouldn't bother putting one on as it will slightly hinder your performance.

I have a feeling that the previous owner may be mistaken. I'm guessing it's open-loop tuned, meaning the ECU gets no o2 sensor feedback at all. The one o2 sensor there is strictly for the gauge. Normally, with a cat you will need two o2 sensors, one before the cat, and one on or after it. Both readings are fed to the ECU and should differ -- this is how it knows the cat is functioning correctly.

Since you're upgrading to S300, I'd talk to your local tuner and see what they think is the best route.

 

[marcs23]

No I do not need a cat to pass emissions, but I would prefer to have one. I looked up the AEM A/F gauge online and it says that there is an output wire that you can wire to the ecu to feed the ecu the A/f. So I called the previous owner and he said yes it was wired to the ecu. I guess I can follow the wires and check myself. It is an ODB1 ecu tuned with chrome. But right now there is no o2 sensors connected anywhere. Just the sensor for the a/f gauge. what I might do is just get a magnaflow cat with the o2 bung and put an o2 sensor in there jsut in case in the future or after i get the s300 I want to use the o2 sensor. thanks for your input

 

[2slo4u]

Is there a reason why you want to install a cat converter? You would normally want the exhaust as free as possible with no restrictions.

 

[marcs23]

I want to stay legal and I can't stand the smell........

 

[2slo4u]

Did Florida change back to doing emissions? Last I heard they got rid of emissions testings to save money for the citizens.
If the smell is strong..something is wrong. I ran a straight 3 inch exhaust before and never got any funny/bad smells at all.

 

[marcs23]

FL does not have emsissions testing. The smell is probaly from me needing it tuned. I ordered my hondata s300v3 yesterday so I will tune it soon. thanks

 

[TheMyth]

No factory o2 sensor needed.
Wire/tap in the white wire from the AEM wideband gauges to the factory o2 sensor signal wire. Then tell the s300 what o2 sensor you are using. You will need to calibrate the s300 to read the a/f ratio as close as you can to the AEM wideband so you will be able to make correct corrections when data logging.
Just make sure the signal wire isn't connected to the factory o2 at the same time as the AEM gauge.
This is a simple task. And I'm currently running my car like this.