exhaust reccomendations?

[karioth]

I have a 91 240SX, im putting a high-flow air filter on it and I want to have the exhaust system re-done with a free-flow cat, and muffler. My question is what size piping should I get? the car is normally asperated with the KA24 engine. My friend who works at a performance shop said i should probably get either 2.25 or 2.5 inch piping. Anyone have any advice/reccomendations ?

[Assmunke]

i got 2.5 with no cat and a magnaflow Muffler and resonator. sounds badass and flows very well.

[quiksilvia]

i would stick with those sizes, do u plan on getting a sr, or doing turbo?

[180fan]

NA = 2.25 or 2.5, Turbo = 3...unless you plan to go turbo later then you could always go 3 now and wait till you're turbo'ed so you don't get the shaft with having to buy 2 exhaust systems.

[NISTECH]

Just a note guys. If you open your exhaust up like that and make it free flowing, if you have an BPT operated EGR valve you can affect its operation and if you have a EGR temp sensor it could throw a code 32 egr system.The BPT means Back Pressure Transducer. It relies on exhaust back pressure to operate. In california a car will fail smog for engine light not working or being on.

[karioth]

i dont plan on turbocharging this car, the body has some dings in it and im probably gonna be in the market for a MR2 Turbo in a couple of years. Just want to make sure i can bust all the civics at my school . My friend reccomends 2.25 but i may go 2.5, does anyone know what the stock piping size is? and whether or not changing exhaust makes your check engine light come on? Again my car is a 1991 240SX, only other mod i plan on making in the cone filter.

[quiksilvia]

i think its 2" stock, not sure though