exhaust

[M20bmw318i]

so what cat back set up would u go wit, i want something that is kinda loud and want to keep my dual pipe and not make a y pipe. where can i get it and how much. thanks

[Budget Beater]

i personally would do y-pipe right after the headers and then use some ebay resonators (if on tight budget) and then mandrel bent piping from jegs and then either a magnaflow can with magnaflow tips or just some generic ebay exhaust (if you are on a tight budget). its much easier and cheaper to swap over to single 2.5" instead of dual stock diameter pipes but again its up to you. However judging by your name i'm assuming u are a 318 which really does not have much flow so again i dont think exhaust would do as much on a 318 vs. a 325is. hope that helps

[M20bmw318i]

yea i have an 84 318i but i have a M20b25 from my wrecked 90 325i motor in it, so i wanted to stay with the duals by i will consider the y pipe i idea. i need the most air flow i can get, but also need some back pressure. they dont make a after market y pipe, so i would have to get somebody to make it for me. right. i work at an exhaust shop so none of this would be hard for me. i am not on a budget really for the most part. what sounds the best?

[Scott314]

its a very delicate balance of back pressure and free flowing charactersitics. but runing huge diameter multiple piping is NOT the answer. mathematically-wise one 2.5 or two 2.0" pipes all the way back are optimal .

Just an FYI...A dual 2" system has a much larger flow area than a single 2.5" . They aren't really close to being equivalent.

[Digitalwave]

A single 2.5" is all the flow you need for an M20B25!

[Budget Beater]

its a very delicate balance of back pressure and free flowing charactersitics. but runing huge diameter multiple piping is NOT the answer. mathematically-wise one 2.5 or two 2.0" pipes all the way back are optimal .

Just an FYI...A dual 2" system has a much larger flow area than a single 2.5" . They aren't really close to being equivalent.

not really, its not that much more surface area if you do the mathematical calculations, plus you always want the surface area to reduce slightly along the lenght of the exhaust system, you don't want it going from small area to larger surface area, thats what causes loss of torque and power.