[helloelectro]

I've been holding off on swapping out the axle back portion of my exhaust because of a few reasons, but now that I'm adding a downpipe (200cell), and already have a Dinan midpipe, CAI and bm3 tune (moving to stage 2 after install) am I really causing any air flow issues by leaving the stock muffler, or is it negligible?

Everything I read about the difference with the stock vs something like and mpe or Dinan axle back is that it's just purely sound. Do you think the m240i stock exhaust is suitable given I've already removed restrictions by swapping the mid pipe where the resonators are more a culprit then he muffler ? Appreciate any opinions.

[nikman011]

That's sound is soooooooo F*CKING great though!

[baldeagleman]

I don't think you are really going to see much HP gains from any type of catback setup. Maybe 5-10HP. If you do an axleback, do it for sound not for power.

[helloelectro]

Originally Posted by baldeagleman

I don't think you are really going to see much HP gains from any type of catback setup. Maybe 5-10HP. If you do an axleback, do it for sound not for power.

Yeah, I've zero thoughts about the axle back creating power. I am thinking the downpipe alone will add enough noise for now.

Bigger concern for me is whether it is preventing the other upgrades from doing their job by bottlenecking the air flow. I'm assuming because it's a "m" series, the axle back isn't as bad as a standard Bmw's exhaust but I have no idea about that being true.

[NISFAN]

Originally Posted by helloelectro

Yeah, I've zero thoughts about the axle back creating power. I am thinking the downpipe alone will add enough noise for now.

Bigger concern for me is whether it is preventing the other upgrades from doing their job by bottlenecking the air flow. I'm assuming because it's a "m" series, the axle back isn't as bad as a standard Bmw's exhaust but I have no idea about that being true.

Stock muffler is capable of far more flow than stage 2.

To put it into perspective, a 3" exhaust is capable of around 700hp, the stock exhaust has a diameter of 3.15". The muffler is a T pipe with tubed through chambers. No real restriction on them.

[mike@x-ph.com]

replacing the mufflers will not add any power, we change it for the sound upgrade

[helloelectro]

Originally Posted by mike@x-ph.com

replacing the mufflers will not add any power, we change it for the sound upgrade

Hey Mike, you are correct. I'm actually looking at it from a "loss of potential" angle, vs a "hp gain potential". If the muffler was causing a loss in potential power because it was holding back the benefits of the mods up toward the engine. Weakest link kind of thing.