why 4 catalytic converters

[wa-chiss]

i was looking at the underside of my X and noticed 4 cats. are they 2 cats split in 4 or 4 full cats? and what size is exit hole on the manifold. im looking into changing everything but the manifolds. anyone done a FULL exhaust not just cat-back.

[Raxephon]

[l31nismo]

One of those is actually a sound resonator. You have three, one on each manifold and one at the y junction. I would recommend leaving the ones on the manifolds so you don't have to deal with any SES light problems. The reason there are three is because of nissan's 3 way catalyst system for reduced emissions. It's kinda one of those things you can't get away from with such a powerfull motor. almost all the new nissans have that set up. Aside from the 4 bangers.

[wa-chiss]

no there "were" 2 on each side. manifold->O2 sensor->1st cat->O2 sensor->2nd cat. same for both sides. anyway i had a local exhaust shop hack the back 2 off, weld on 2" pipe and he made a y-joint, 2.5" pipe to a magnaflow and 2.5"back. had to pay cash and no reciept. its quiet when idling and on the highway but when i stomp the go pedal it SCREAMS.

[l31nismo]

Nice!!!