Custom Axle-back Exhaust

[DoofyTheNut]

I just recently finished the fine-tuning of my axle back exhaust for my x1 35i. I had no idea what I was doing going into this project, but definitely had a blast doing so. I have been wanting to learn how to weld for a while, but haven’t had a good reason to buy a welder until I thought about making an exhaust. I decided to order some 304 stainless steel 2.5inch pipes from amazon seller “blackhorse racing” which seems to be reputable for the price. I ordered an 8 piece set of pipes, 2 90 degree, 2 45 degree, 2 180 degree bends and 2 48 inch straight pipes, as well as a magnaflow muffler. The biggest obstacle on fitment was finding a 2 bolt flange that would connect to the stock midpipes without any issues, so I decided to buy a muffler off of a 135i that had been wrecked and used the flange to connect to the midpipes. From there, it was completely trial and error, fitting the pipes together and marking them to tack weld, fit again, and then finally finish welding. I had both of my flange bolts/nuts break however, so I currently am using some hardware from Lowe’s to hold it all together until I can find a more permanent solution. But the end product right now is so amazing I can’t believe it. The muffler keeps the car quiet enough that it still retains that “sleeper” feel but when you go WOT it wakes up. There’s so much popping and burbles as well, and I should mention too that I do have a vrsf downpipe installed as well, so that will probably affect the sound. It took me probably 16 hours total and ~$650 including the welder and welding equipment, so I’m very happy with my investment. I was quoted $750 by a reputable shop to make a custom axle back, so I’d say the knowledge gained and the money saved made this project a 10/10.

If you have any questions, please let me know!

[Chicone]

That's really cool, as I know the options for our cars are slim. I miss my Borla. Great job, congrats and you picked up some skill at the same time. Fine tune it and turn it into a business! You would have buyers.

[Jonathan0880]

Originally Posted by DoofyTheNut

I just recently finished the fine-tuning of my axle back exhaust for my x1 35i. I had no idea what I was doing going into this project, but definitely had a blast doing so. I have been wanting to learn how to weld for a while, but haven’t had a good reason to buy a welder until I thought about making an exhaust. I decided to order some 304 stainless steel 2.5inch pipes from amazon seller “blackhorse racing” which seems to be reputable for the price. I ordered an 8 piece set of pipes, 2 90 degree, 2 45 degree, 2 180 degree bends and 2 48 inch straight pipes, as well as a magnaflow muffler. The biggest obstacle on fitment was finding a 2 bolt flange that would connect to the stock midpipes without any issues, so I decided to buy a muffler off of a 135i that had been wrecked and used the flange to connect to the midpipes. From there, it was completely trial and error, fitting the pipes together and marking them to tack weld, fit again, and then finally finish welding. I had both of my flange bolts/nuts break however, so I currently am using some hardware from Lowe’s to hold it all together until I can find a more permanent solution. But the end product right now is so amazing I can’t believe it. The muffler keeps the car quiet enough that it still retains that “sleeper” feel but when you go WOT it wakes up. There’s so much popping and burbles as well, and I should mention too that I do have a vrsf downpipe installed as well, so that will probably affect the sound. It took me probably 16 hours total and ~$650 including the welder and welding equipment, so I’m very happy with my investment. I was quoted $750 by a reputable shop to make a custom axle back, so I’d say the knowledge gained and the money saved made this project a 10/10.

If you have any questions, please let me know!

Axleback system affect warranty I wonder?

[DoofyTheNut]

Originally Posted by Jonathan0880

Axleback system affect warranty I wonder?

I don’t have a warranty on my car to begin with, so I didn’t care, but I guess even if you did it wouldn’t matter. The only thing that is affected is the rear exhaust flap that opens and closes, which isn’t going to hurt any of the electronics. Otherwise, you get a better sound!

[solidsleeper]

where's the sound clip/video?

[Jonathan0880]

Originally Posted by solidsleeper

where's the sound clip/video?

Yeah I second that..

[Jonathan0880]

Originally Posted by DoofyTheNut

I don’t have a warranty on my car to begin with, so I didn’t care, but I guess even if you did it wouldn’t matter. The only thing that is affected is the rear exhaust flap that opens and closes, which isn’t going to hurt any of the electronics. Otherwise, you get a better sound!

Rear exhaust flap? this is in the stock muffler? Would that not effect compression ratio's during rev out?

[DoofyTheNut]

Originally Posted by Jonathan0880

Rear exhaust flap? this is in the stock muffler? Would that not effect compression ratio's during rev out?

The rear exhaust flap located in the muffler will not affect anything in the car. It’s commonly referred to as a “golf tee mod” to actually disable it without removing the muffler. I am going to try to upload my first video of it revving, although it’s not terribly great. I might see if I can get another video later today maybe.

[DoofyTheNut]

https://streamable.com/0zkna

Here is from the first day. I’m going to get a better clip, as I had no knowledge on how to rev at the time to properly get the sound out.

[Jonathan0880]

Originally Posted by DoofyTheNut

https://streamable.com/0zkna

Here is from the first day. I’m going to get a better clip, as I had no knowledge on how to rev at the time to properly get the sound out.

Sounds really good. Just enough but not too much. Seems like a pretty easy mod then, watch the catch? why is everyone not doing this across the board. I guess no performance gains, it's all sound aesthetics...