Wideband o2 AFTER cat?

[oplix]

Would installing the wideband o2 sensor in the rear o2 bung on a stock exhaust still give accurate readings or will the cat converter mess them up?

 

[snowborder714]

The cat will cause inaccurate readings.

 

[oplix]

damn it.

 

[turboglenn]

Also, due to holes that easily form in the flex section, it's best to mount it in front of that as well (between turbo and flex to be clear) The holes in the flex will cause it to draw in ambient air through the venturi effect also fouling the reading of the UEGO

 

[oplix]

are the wideband o2 sensors same threading as regular o2 sensors?

 

[DougR]

are the wideband o2 sensors same threading as regular o2 sensors?

Yup. They are..

 

[bpestilence]

Certain wideband controllers will have a 0-1 volt output that you can use to feed to the ECU if you feel it is necessary to replace the front O2 sensor with a wideband.

The rear O2 sensor, should, however, read stoich at all times if the cat is working right.

 

[knochgoon24]

The front o2 can be too hot and shorten the lifespan of the WB. Just take the downpipe off and have someone weld a bung on properly. I put mine right after the bend and before the flex section on the downpipe.

It took my buddy all of 5 min to weld it.

 

[turboglenn]

I think AEM recomends the sensor bung be between 18 and 36 inches from the turbo turbine, or exhaust port (can't remember it's late and i'm tired)

BUt even a foot down the down pipe from the stock o2 housing (if you run that - o2 housing that is) I had a wideband in the front bung feeding the haltech for it's closed loop and the sensor lasted a year and already had several car tunes on it before i put it in my car. Now i have that one for customer cars and an AEM in my car for full time duty

 

[elfroggo]

I've asked Sean at FFTEC about this a couple years ago regarding wideband sensor placement. I myself have mind installed precat permanently, but he said that it really shouldn't affect the readings much even if you place it after the cat.

Think about if you're getting your car dyno tuned with wideband readings, the probe is placed in the tailpipe. Maybe the readings are slightly different, but apparently it's not enough to throw the entire tune off.

Also what he mentioned is that the cat really only makes a large difference during idle and cruising speeds. At WOT, the exhaust flows so much that the cat doesn't work nearly as efficiently to affect A/F ratio.

 

[bling5tatus]

The cat will cause inaccurate readings.

WHOA man, what's up with this response? The mounting position of your o2 sensor does not affect the accuracy of your o2 sensor... Please try to think about things before you post them, or at least word them to where they are correct. You're a "dsm wiseman" and these people expect for the things you say to be proper.

You would not want to mount it after the cat because you'd be getting a reading of filtered exhaust gases. You want to know what the exhaust gas that's coming directly out of the motor is doing. It's kinda like putting an amp on your stereo system, it doesn't change the way your ears hear the music, it changes the way the music is output.

 

[Boosted98gsx]

The cat will cause inaccurate readings.

How would a cat cause an O2 sensor's accuracy to be changed?

 

[turbosax2]

Easy guys. He misworded his response in an attempt to keep things simple. Placing the o2 sensor after the cat will not make the readings inaccurate, but the readings won't be as useful for tuning purposes versus putting the sensor before the cat.

 

[eclipsh]

I found that putting the O2 sensor shortly after the flex section places it perfectly to route the wiring up between the k-member and the firewall. Also remember to keep it angled slightly upward so condensation can't pool in it.

 

[1bad92awd]

Placing the o2 sensor after the cat would in fact skew the numbers for tuning. Maybe not by much. But think about it, the cat reduces some of the gases and emissions that are emitted by your engine. By placing the o2 sensor before the cat you are getting a better reading of what exactly is comming out of your engine before it exits the vehicle. Those are the numbers that you need when tuning your engine because your trying to monitor what happens inside of it.

 

[turbosax2]

My apologies if we don't meet your standards 100% of the time. And FYI, the firmware update on his LC-1 did fail for no apparent reason. I was there to witness it.

 

[Boosted98gsx]

My apologies if we don't meet your standards 100% of the time. And FYI, the firmware update on his LC-1 did fail for no apparent reason. I was there to witness it.

Run any malware scans recently?

 

[turbosax2]

Any more discussing this we should probably keep to the LC-1 thread. But I do know that laptop is kept clean with antivirus, ad-aware, and spybot.

 

[jrohner]

The farther back the o2 sensor is mounted, the slower the response time also.

 

[bling5tatus]

Any more discussing this we should probably keep to the LC-1 thread. But I do know that laptop is kept clean with antivirus, ad-aware, and spybot.

I am posting my reply there now.

 

[bling5tatus]

The farther back the o2 sensor is mounted, the slower the response time also.

This is as incorrect as Snow Boarder's reply. The farther back the o2 sensor the longer it takes to measure the pulses that you are wanting to measure in relation to what engine load you were at. Take into account that a flex section is an exhaust leak (a lot of times)... and any exhaust leaks will give you a reading that is skewed from what you are wanting. Measure the AFR BEFORE the flex section and you're golden.

The response time of the sensor does not change based on where it is mounted.

 

[cooldude919]

Im guessing it should be ok if you have it in the rear o2 bung if you have no cat? This is my setup and the only issue ive ever seen is that the o2 sensor output is just a little laggy because of being further back, but its very minor.

 

[1bad92awd]

I just realized that reading the very first post on this thread...

If you use the stock o2 bung that is near the cat converter, that means you will be eliminating the second o2 sensor for your ecu. You may very well get a check engine light for doing that.

 

[oplix]

it's ok i just had exhaust shop weld a new o2 bung before the cat. it's after the flex but the flex is new and putting it before the flex (very close to the turbo) will cause the wideband sensor to fail prematurely.

 

[jrohner]

This is as incorrect as Snow Boarder's reply. The farther back the o2 sensor the longer it takes to measure the pulses that you are wanting to measure in relation to what engine load you were at. Take into account that a flex section is an exhaust leak (a lot of times)... and any exhaust leaks will give you a reading that is skewed from what you are wanting. Measure the AFR BEFORE the flex section and you're golden.

The response time of the sensor does not change based on where it is mounted.

I didn't mean the response time of the actual sensor itself changes magically. Response time as in response to a change in afr because it takes a bit of time for it to get back through the exhaust and to the sensor.
If you watch your AFR, you can see this if the sensor is mounted back a ways -- Like in closed loop mode, the transition from closed to open loop mode, or going into and out of rolling fuel cut.