M30 exhaust size....

[george graves]

Well, using the m30 down pipes is a no brainer, but being I was short on cash, I had the exaust shop tie the m30 down pipes to my stock exhaust....

At some point I want to do it right...

I'm thinking of a single 3" set up from a "Y" at the down pipes to a 3" cat, all the way to a muffler. All single 3" stuff.

What do you all think? Could be a plan for a cheap good sounding set up?

I did find this that you will (I DID) find interesting

LINK: http://home.mindspring.com/~scrappycrow/e28exhaust.html

So what you all say? single 3"?

[bmw335isturbo]

for N/A I would not go any lager than 2 1/2
FI I would go back to 3" mandrel bent

[drifty340i]

Yip 2.5inch max!

[drifty340i]

Im using a 2.5inch mandrel bent pipe on my v8! and thats ideal for my engines size

[george graves]

Wow, then I was way off...Thanks - I'll keep that in mind.

So 2.5", and think that would also be plently for 8-10 psi of boost?

[euroshark]

Most likely plenty for 8 to 10psi. You can do the math to figure out the ideal volume of your exhaust system based on the maximum speed of your motor and it's size.

[drifty340i]

2.5 will be plenty for 10lbs

[bmw335isturbo]

Wow, then I was way off...Thanks - I'll keep that in mind.

So 2.5", and think that would also be plently for 8-10 psi of boost?

well if you are going to switch latter to fi then that breings a lot of ?
basicly for turbo you are not going to want any restriction 2.5 is going to work but how well? if you try to push 10psi in a 335 HEAT will be your biggest problem

[JoeMadoo]

I'm building a full 3 inch exhaust system right now for my 335i with a high flow magnaflow cat and 3 in dual 2.5 out magnaflow universal muffler. I plan on turbo-ing it next summer so I fugured it would be a good idea to build a turbo exhaust now.

[vic_325]

just looking through this, seeing how 3" is too much for N/A, would dual 2.25" also be too much for N/A b35? right now i plan on matching it up to my stock dual 1 7/8" or what ever it is. but i want something more agressive. than stock.

i thought id just post here instead of make a new thread.

[vic_325]

also what muffler? is there diferent flow ratings what works well? im knew to building exhausts

[E30SPDFRK]

Yes, far too big. If you want to do dual exhaust, 2" is fine (if a little on the large side) for an m30.

Although with dual, you get less efficiency than a single and it costs more, so I would recommend a single 2.5 setup. This is what I have and it is great.

You can run whatever muffler you feel like running.

[vic_325]

i guess its heavier to run a dual aswell. What do you have for a cat and resonator?

[Lurker27]

Go with 3" for turbo, IMO.

[E30SPDFRK]

i guess its heavier to run a dual aswell. What do you have for a cat and resonator?

I'm running a high flow cat from a Dodge Charger (the lame 80's ones lol), no resonator to a Brullen straight through muffler. It's fucking loud.

I was running my stock 325e exhaust with no muffler before, and I felt an actual difference switching to the 1/2" larger tubing. Low end is just about the same, but top end pulls harder. And my top end was good before.