Hi , i d like swap my cargraphic 200 cell exhaust to a catless x pipe setup , but i'm a little concerned about possible experience of any kind of power loss due to out of range catless readings of the 2nd O2 sensors .
It seems that some guys running catless without specific tune for decat , they had some power loss due to rich LTFT after install decat pipe although using O2 Spacer .
It seems that 2nd O2 sensor reading does not only is used by ECU to check CAT efficiency but it also used post CAT readings to manage fuel trim expecially LONG term fuel trim .
Here is the problem , if this is true and it seems true , when the ecu see strange values coming from o2 sensor it starts to make adjustment trying to reach normal values as long as CEL light coming on .
Some guys say that when CEL is on car run very bad and when they reset error , car run much strong with CEL off.
Also , if one put decat pipe without any spacers , Cel come on due to P0420 error ( cat inefficiency ) , while if one put spacer , CEL come due to P0139 ( O2 sensor slow responce ) in both case those errors could cuase power loss ..
All those informations make me worry about going catless , since i was ever thought that the only problem of cel due to catless was the annoing light on the dash.
I cannot retune for turning off rear O2s , so i'd like to go with extender but it seems this metod does not work .
Please can someone with decat and spacer , let me know how the car feel when CEL light is on ? Power loss ?
Thanks and sorry for my English

 

Just have your tuner code it out.

 

This is not possibile , here in Europe tuners dont turn off 2nd o2 sensor for legal reason , plus i have already a tune that run very well and i dont want to swap to another file that may not run as well.

 

Find a tuner in another country that will turn it off for you.

 

No issues just swapping to the catless exhaust. The CEL is just a check to show they are there. They're not doing much. You'll be fine.

 

try to see if you can find one of these and try them... you can also pack it with steel wool... not sure how easy to source in Italia

 

What about running catless without any Spacers ? someone has tried and does not get CEL

 

not sure if that is even possible... the rear O2 is meant to check for efficiency of the cat itself... by using a spacer, there is a slim chance that at least the readings between the pre and post cat are different tricking the system to think that they are there... by not using a spacer and having the O2 in there, i can't see there being a different reading unless there was some sort of resistor trick that could be used...

 

I think the same as you but it seems someone here on 6speed had tried this way and get no CEL or at least they say so...
I dont know Maybe their downstream o2s was wear more than upstream once so the read less oxigen ?

 

i just replied your PM and read your thread pre PM.

i also tried the bung extenders ( they call them mini cats? ) but it has been more than a few years since i ran decatted here in CA US. ( "they" will impound your car and turn it over to the communist chinese if you are found running "catless" in Cali ( kidding )
i ran simply with my 1.2 bar ( also same as you have ) an OLD cargraphic tune, and went catless and it ran perfect. although I never "logged" data and was just a "street" car at that point. best advice i can give you? run the decat pipes withOUT the spacers ( mini cats or bung extenders.. whatever they are called. ) i dont believe you will get any CELS if your 02's pre and post are working properly. they also ( as you know ) fail "slowly" so when my pre 02's went bad recently, they gave cels only intermittenlty soft codes! it wasnt until i had the car hooked up the the PWWIS porsche diagnostic system that it confirmed it was bad pre 02 sensors.

good luck and cheers