Taking out and replacing cats....

[Afboy143]

On my explorer 4.0 SOHC I have 2 cats and 4 O2 sensors....2 before the cats and 2 after. I currently have the 50 series flow master mufflers duals installed with 2.25" pipe

My question is

If I take out one cat and stick a pipe in its place then stick a high flow cat on the second pipe...what will this do to the sound and performance? Also, what would I have to do with the o2's that come after the cats? Would I need to install O2 bypass sensors? If so, where can I buy them?

 

[92sho16]

The second set of oxygen sensors are there to basically test the efficiency of the cats. Unless you buy the O2 simulators you could not just put pipe in its place and if they do emissions testing un your area for inspection you wont pass the test either. I would suggest getting two high flow cats.

 

[spindlecone]

Your best bang for the buck would be to get a Y-pipe and elimnate the two pre-cats, will still need the 02s in the y-pipe, the sound is awesome and perf gains are about 8H.P.

 

[jimbo74]

Search!!!!

 

[spindlecone]

Search!!!!

The master of BUMP has spoken

 

[Afboy143]

Your best bang for the buck would be to get a Y-pipe and elimnate the two pre-cats, will still need the 02s in the y-pipe, the sound is awesome and perf gains are about 8H.P.

The second drawing shows what my exhaust rite now is. The first is what comes into my head after reading your post. Is this correct?

Yes I am the man at freehand drawing in photoshop

 

[spindlecone]

Nice drawings
Whatever you do you are going to have to retain the two after cat sensors and use 02 sims on them or you will throw a CEL.
IF you can get a shop to built a system like the first pic they can weld in new 02 sensor bungs no problem.
As said above you will never pass smog inspection if req. in your state.
On my trac I have 4 cats,my random tech Y-pipe eliminates the two precats, when I need smog inspection is a simple matter to install the OEM Y-pipe once every two yrs.
My main cat 02 sensor is disabled by my flasher tune so no worrys there.
Not a clue as to what your design will get you if anything, you could always go with aftermarket high flow cats but if your cats are in good condition, may not be much bang for the buck