[twelve535i]

I was looking to build a custom catback exhaust, and I want to know where I should start. The 535i's exhaust is a bit different from what I've seen before. It starts off with a y-pipe, one pipe that splits into two. Does anyone know what diameter the inlet pipe is, and outlet pipes?

http://www.ebay.com/itm/3-2-5-Y-Pipe...052825&vxp=mtr

Is this the type of part I would start off with?

[mk47]

I believe the piping is 2.5 inches. What mufflers were you planning to use?

[twelve535i]

I believe the two outlet pipes are 2.5". Can anyone confirm?
Real mystery is what the diameter of inlet is? also 2.5"?

Not sure of what mufflers I want to use yet. I have a Magnaflow axle back now, and it sounds pretty good, so I may just keep those.
I have to start with the Y-pipe. From there, I was thinking X-pipe, two 12" resonators, and two mufflers.

[RambleJ]

For.some reason I thought the magnaflow exhaust for our cars was catback not axle back??

[twelve535i]

Originally Posted by RambleJ

For.some reason I thought the magnaflow exhaust for our cars was catback not axle back??

Magnaflow makes a catback, which I don't think like. Personally, I think it sound more aggressive and a bit louder, but I guess they figured most 5 series owners don't like aggressive?
I have a custom made axle-back using magnaflow race series mufflers, which I think sounds better than their catback.



I think I figured out that the INLET of front pipe is definitely > 3 inches, because according to the diagram below, the clamp is about 3.3 inches.