Catalytic converter replacement questions!!

[40eastvp]

Hey guys I have a 97 expo with a 5.4 and gidson shorter headers along with flowmaster super 44 3" exhaust. Ive be looking to replace my 4 cats with 2 high flows. Ive read several threads about this but I havent found one that stated whether they had to delete the rear O2s or even if they passed emissions again after doing the work. Has anyone done this and have any info for me? and recommendations about high flow cat I was looking at magnaflow. Thanks

 

[huklebuk]

I've heard that if you run just the two high flows then you will through codes all day, check engine light will come on. This is coming from a mechanic who cut out the pre-cats and put in two high flows on another truck. He didn't know if it passed emmisions or not. I have the magnaflows and I was contemplating taking out the pre-cats and just using those. Did you take out the y-pipe and replace it with something aftermarket? He also said that particular part on the expy is restrictive. How do you delete the o2 sensors? I've never heard of that before. Hope this helps some.

 

[40eastvp]

Now what I was told is that you must not do away with the precats and Ive heard of people replacing or removing the aftercats with out throwing codes but I havent heard from someone that did it already and knows first hand. I heard that deleting the aftercats made a huge difference in power and sound with no codes via other post but not all the info I was looking for was there.

 

[seeker]

I dont believe that you can delete the O2 sensors. Your computer is looking for information on O2 levels before and after cats. It might be possible to trick the computer with programmers. In the long run you are taking a big chance not being able to pass emissions inspections. If you have a performance shop or good muffler shop near by, you may be able to get their recommendations

 

[86caprirs]

Well you can buy simulators that trick the computer for the hego's.

 

[Rook27]

by "deleting" the rear O2 sensors, I believe they are talking about using a programmer. I had that done to my mustang using the SCT excaliber and had all the cats removed. The guy that did the tune for me said that he just turned them off. Never had a check engine light come on for O2 sensors, and the stang sounded great and ran perfect. Not sure about the emissions part though, we didnt have emission checks in Florida. If it were me, I would just call up a local performance and ask them what they thought (most of the time, advice is free) and they might be able to give you some other pointers that would help you get any questions you might have answered.