I have a 90 fc and i have the origional exhaust on it and it is leaking and about one good hammer hit away from coming off. My brother has a welder and a pipe bender so i will be making my own. Should i keep the same size or go bigger?, keep the duals or have a single?. Can i just put one new cat on and ditch the other three?.

 

you can pass emissions with a single cat, do you have any other mods? 2.5" single is normally a good size for N/A's. However, if you do go single the car is louder than if you go with a "Dual" system. Two mufflers would naturally be quieter. Another thing to think about, the larger the piping the louder the car.

I would make a 2.5" single with a Catalytic converter, then Y-pipe to two 2" pipes, then some sort of chambered muffler if you want it quiet, or a straight through design if you want to be heard before you are seen...

Also, instead of a chambered muffler, a "S" design (internally, i.e. Dynomax, etc.) is a nice in between of screaming and something chambered like flowmaster...

- chris

 

Chambered mufflers generally arent reccomended on rotaries because of how strong their exhaust pulses are. If you are having dB problems, then you might want to consider having some sort of resonator right behind the Y pipe. Magnaflow mufflers really seem to do the trick and sound great on our cars. I am using two of them in series on my TII single exit custom exhaust.