Exhaust piping diameter ?

[oorx7]

I have 535i 5 with a pretty large hole in the muffler. Although I kinda like the sound I really want to replace it. I have looked into replacing it with an aftermarket one, but feel I can make my own for quite a bit less money. I plan on not really making much more than an extra 100 hp, through out the cars life with me. That is a high number at that. Not really going for a loud exhaust either. I am now 30 and must be getting old because I think it is too loud now. When I was younger the first thing I did was remove the mufflers and or cat. I will be replacing the cat with a resonator or two as well. I don't have emissions testing were I am registered.

So my question is, what diameter piping would you suggest?

Should I stay duel till I get back to the muffler?


Thanks
Brandon

[Jon K]

Making another 100 hp? Whoa baby...

[oorx7]

I am just saying that I might make an extra 100hp in the future, and don,t really like to make things twice. Definitely am not gaining 100hp from an exhaust upgrade. LOL!!!!

Currently I am not going to add any thing more than this exhaust, air filter, and maybe a chip.

Here are some of my past and present projects. http://www.cj-motorsports.com/projects.htm

[Jon K]

Anything remotely close to 100 hp on an M30 is going to require a turbocharger in which case your exhaust will be of little concern

[oorx7]

True. I was thinking about twin gt28r's. But again exhaust would have to be redesigned around that system.

So lets forget about the HP goal or limit.

What size is stock piping?

[icesoft]

Roughly 2"... I ran a flowmaster 2-2" into 1-2.5" collector and ran 2.5" all the way back from where the stock x-pipe was.

True. I was thinking about twin gt28r's. But again exhaust would have to be redesigned around that system.

So lets forget about the HP goal or limit.

What size is stock piping?

[oorx7]

That's the kinda stuff I am looking for.

I was thinking of running stock diameter to a Y off some sort, then to 3" back to a muffler.

Any reason to use an X pipe then Y it a couple of feet past, maybe closer to the muffler?

Some thing like this as an X pipe. I really want to use a resonator of some sort and this would fit perfect, I think. http://store.summitracing.com/partde...5&autoview=sku