ok sorry if this is already posted somwhere but i cant find how to do it on my 01 3.0...only the 3.5 and stuff so im kinda confused...again if this is posted somwhere please direct me...what i want to know is where is the main cat on mine and what will happen with the 02 sensors and will i need new gaskets? i see the 2 bulges in the headers that look like cats and then one in the middle of the y-pipe and then there are big spots under the car also...help please lol sorry

 

 

ok, those 'bulges' are the cats. the ones mounted to the headers are the pre-cats. the cat post y-pipe is your rear cat. same as the 3.5.

gutting is illegal in many places soo...ya

 

well the prob im having it that i only have 1 big bulge coming off the front manifold...there isnt one on the back but there looks like there is one IN the y-pipe...so that big bulge AFTER the y pipe is the main cat rite

 

Headers are illegal to so.

 

You have it figured out. The side of the engine that is toward the radiator, the pre-cat is bolted to the exhaust manifold. On the side of the engine towards the firewall, the pre-cat is part of the y-pipe. The main cat is after the y-pipe, roughly under under the front passenger seat.

 

so are there 3 or 4 cats on these cars? Not trying to thread jack but, if you remove the pre cats, add o2 simulators is that going to affect gas mileage/ vs replacing the pre cats with same parts. Just seeing what will work, going to get a back pressure test on my 02, see exactly which cat is bad, as i have no cel.

 

The cars have 3 cats. A small one for each bank of the engine and a main one further back after the y-pipe.

You don't necessarily need an O2 simulator. I don't have the pre cats and I'm using the O2 sensors that were on the car.

 

oh ok good to hear but wont that make the car loud if u remove the precats. I had a main cat removed on my 2nd gen maxima, made the car a little loud but also was a little quicker than before.