# fool your o2 sensor



## 83854life (Jul 21, 2008)

I live in Idaho and we don't have emissions. So my cats are going out and I would like to get rid of them altogether but I have been told that my car would run like crap if I did that do to the brain. It needs the signal or something. I found a divice that plugs into your o2 sensor and sends the that signal you need just fools the computer. Would it work or is there something else about it I'm not clear on.







thanx for your replies


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## GLS-S4 (Jun 6, 2005)

*Re: fool your o2 sensor (T-Bag)*

Which cats are "going out", front pair or rear pair ?
If it's the front cats that are failing, recommend piggie pipes or install aftermarket downpipes and cat back exhaust with hi flo mid stream cats.
Stock exhaust has 4 cats and 4 O2 sensors. Recommend leave the front O2 sensors alone. Piggie pipes and many high quality aftermarket exhausts place the rear O2's behind rear cats for "no fooling ECU" required and assured your S4 will run well with no CEL.
Use VAG and monitor rear O2's to see how involved their signalling is thru both warm up and operating phases. While not impossible, it is not near as simple as adding a resistor or installing an inexpensive aftermarket "black box" to trick the ECU as some people may suggest.


_Modified by GLS-S4 at 1:13 PM 8-20-2009_


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## 83854life (Jul 21, 2008)

*Re: fool your o2 sensor (GLS-S4)*

thanx man I have a catback so I assume it's the front they are just a pain and I don't want to deal with them. The same thing was happening on my 02 1.8t jetta that I had they are just to damn sensative. And the best deal on fronts I found is $850 from MJM they are TT but it only fits onto their 2.5" catback system which I think is on this. I know it is 2.5" but not the brand and it uses Borla muff. Any suggestsions and thanx again


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## GLS-S4 (Jun 6, 2005)

*Re: fool your o2 sensor (T-Bag)*

Do you have stock downpipes or aftermarket? What do you mean by too sensative, the O2 signalling or ?
What is the exact issue with your S4, CEL on and trapping DTC's due to failing front or rear cats, front or rear O2's, etc ?


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## LaseRed02 (Aug 19, 2008)

I gutted my cats on my 02 s4. While the sound is absolutely incredible(so loud it numbed my ears after driving for 30 minutes or more), it feels as though the performance is going right out of your cats. If you're thinking of doing what i did, and opening the cats and removing the honeycombs then you'll be a fool like i was, so just go with downpipes or piggiepipes, they're basically straightpipes(no cats) and offer the same performance


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## GLS-S4 (Jun 6, 2005)

*Re: (LaseRed02)*


_Quote, originally posted by *LaseRed02* »_I gutted my cats on my 02 s4.

Did you remove the front pair, rear pair or all 4 cats?
Piggie Pipes as originally pioneered by the great guys at VAST gut the front cats directly behind the Turbo's for faster spoolup and reduced localized heat while retain rear cats for emissions control by relocating rear O2 sensors.


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## LaseRed02 (Aug 19, 2008)

*Re: (GLS-S4)*

Well when I did it I wasn't aware of the primary cats (front) and instead gutted the main cats. I lost all performance, it was terrible. But the sound. It was ridiculous. I heard about the piggie pipes for around 700 but now that AWE tuning lowered the price on their downpipes to around 1200 I bought those instead. They're being installed on my car this week, as with AWE's Twin1 exhaust. I hope that i'll have my torque back, since it felt like it was just pouring out from under my car with those gutted cats


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