CEL defouler ?

[Coyotes55086]

Hey guys , so I'm going to go through with a high flow cat install on my gt . They are 50 cell cats . I know that this is going to throw a CEL . So I've been watching a bunch of videos on defoulers and how they actually work to stop the code . Anyone have any experience? Does anyone know if the stock o2 sensor is on the downpipe or on the stock cat ?

Sponsored

 

[TunedN]

One on each. Upstream inches from turbo. Downstream in side of cat housing.

 

[Coyotes55086]

So the one on the cat housing is where the defouler would go. What can u do if the new cats dont have a o2 sensor bung on the cat housing ? They are just bare

 

[TunedN]

So the one on the cat housing is where the defouler would go. What can u do if the new cats dont have a o2 sensor bung on the cat housing ? They are just bare

Buy an O2 sensor bung (or defouler) and have it welded in just after the cat. I personally don't like the idea since your sensors will be sending the PCM false data with a defouler, but hopefully it won't cause problems for you. I asked the techs at Cobb and some of their protuners if the downstream sensor data is used for engine management or only emissions, and they all didn't know but said it's likely both.

 

[Chef jpd]

Are you just replacing the cats, or the whole pipe?
What brands are you looking at?

 

[Coyotes55086]

I had a pair of no name 50 cell cats custom made for me . I dont want to remove them . But I want to get as much sound through as possible. And I'm thinking of just replacing the cats not the whole pipe

 

[Coyotes55086]

Can you weld a defouler without the o2 bung ? Would that make the sensor get closer? Because the bung lifts the defouler away a bit further ?

 

[Ebm]

Shaun from AED posted this in another forum I visit. It was meant for 2011-2014 Mustangs but it still applies to newer Stangs as well.


Most people know the Rear o2's are used to detect proper catalyst functions (o2 saturation rates from the catalyst), but many do not know they are used for something far more important for the performance crowd.

The Front O2 sensors are Wideband O2's which have an output range of 0 to 5 volts. Based on O2 content the UEGO sensor targets a given voltage, which is translated by the software to Lambda. They are VERY accurate at detecting o2 content.

The Rear O2 sensors on these vehicles are Narrow band type O2's which have a 0-1 volt range and are not accurate enough to read actual O2 content but rather they oscillate from full rich to full lean and the average value over these oscillations is accurate but only when near Stoich values. (IE at richer WOT A/F Narrow bands are not accurate)

Wideband O2's tend to 'drift' over time and they do need calibration from time to time to stay accurate. Some tuners replace their wideband o2's every 6 months to keep their O2 data accurate, others (like me) use high end ECM equipment that can be re-calibrated at any time. Innovate give this option with their aftermarket wideband o2's, as does NGK.

The amount of drift in the Wideband depends greatly on the temperatures and contaminants the o2 sensor sees, so it is difficult to speculate the frequency of necessary re-calibrations.

Ford in their wisdom took this into account and uses the Rear o2's to keep the Front O2's properly calibrated.
Narrow band O2's do not need to be calibrated as they are continually oscillating from full rich to full lean and the average is very accurate, but only when near Stoich, so Ford uses the Rears to re-calibrate Stoich of the Front O2's.

So what does this mean for the aftermarket?

This means *if* you remove your rear O2's and have them disabled in the tune the ECU will NEVER re-calibrate the Front Wideband O2 sensors and over time (impossible to say how long) they will start to drift and become inaccurate.

This also means if you KEEP the rear O2's installed and turned ON in the tune but have exhaust leaks between the Front and Rear O2's the ECU will incorrectly re-calibrate the front O2's and the car will end up running rich.

So the answer to the question 'Are Rear O2s necessary?' is Yes, *if* you wish to keep the front O2's in proper calibration. The other option is to replace your front O2's regularly to keep them in proper calibration. (like we do with race cars running stand alone systems).

My advise is to KEEP the Rear O2's properly installed and functioning in the tune while ensuring NO exhaust leaks are present up stream from the Rear O2 sensors.

 

[I Bleed Ford Blue]

I've heard from several over the years that defoulers are a crap shoot whether they work or not, and MIL eliminators tend to burn out so they need replaced periodically. Your best bet is to have the tune re-calibrated to your new cats. That way everything works the way it should and your front sensors will get re-calibrated as needed.

 

[Coyotes55086]

For myself we arent emission tested here anymore. So I'm not so sure the importance of keeping the sensors it tune would make . Am I wrong?

 

[Coyotes55086]

I'm trying to avoid tuning . Is so expensive here
And I dont have a handheld tuner yet

 

[Chef jpd]

Check to see how your yearly inspection is done.
Here it is an OBD2 check.
If any sensors show "not ready" you will fail the test.
You will see rear O2 sensor not ready and O2 sensor heater not ready.

 

[Coyotes55086]

I'm in Ontario and we dont have yearly inspections

 

[ORRadtech]

For myself we arent emission tested here anymore. So I'm not so sure the importance of keeping the sensors it tune would make . Am I wrong?

If what I read above is correct then, yes, you are wrong. Without the after cat sensors the precast sensors will eventually make you run too rich.

 

[Coyotes55086]

The stock sensor is on the cat . When I install the new cat , can I place a new o2 bung after the cat ? Will that work?
If I'm not mistaken I also heard in a video yesterday that some o2 sensors actually require the cat to function? Is this true ?

Sponsored