"Active" exhaust build

[Matticus91]

After realizing how indecisive I am about exhaust volume and tone, I've decided to try something different that I haven't seen on the 135i yet. If anyone else knows of any existing projects like this please let me know as I'd be very interested.

My plans are as follows:

1. Take stock 135i Exhaust and gut majority of baffling + close off second pipe's holes as done in the "PE" mod.
2. Add catless DP.
3. Find power source for valve and fabricate a manual switch to activate.
4. Mount switch in cabin for manual "Loud button".

This will allow me to keep a mostly stock setup that sounds good with the valve closed but will allow me to open the other for a much louder exhaust note. I'll also be able to keep it closed when I am on long drives (often drive 4+ hrs) to avoid any drone.

Input welcome on this. Will make this a DIY thread once I start the process.

[Pig Farmer]

Where do you plan on putting the valve?

[Matticus91]

Originally Posted by Pig Farmer

Where do you plan on putting the valve?

Not moving it I'll keep it in the same location which will be on the "straight pipe" side of the 2 pipes.

[dtla1]

It's fairly common to do a cutout. It may be easier to tap into the vacuum connector in the trunk and run a switch from there. It's already pre-wired, will still work on vacuum. The switch will let you decide when you want to have the flap always open, or when to let it open and close as usual. Or you can just use a JB4 and toggle on and off through the controls there.

[chris82]

I will try to find the url, but there is someone that cut open the stock 135i exhaust, took all baffling out, sealed it up, and could not even tell anything had been done. Based on that I don't think it will make it any louder; the catless DP will though.

[dtla1]

Originally Posted by chris82

I will try to find the url, but there is someone that cut open the stock 135i exhaust, took all baffling out, sealed it up, and could not even tell anything had been done. Based on that I don't think it will make it any louder; the catless DP will though.

I think the main thing in OPs post is to note that the holes will be closed, which will indeed make the "second pipe" a straight pipe effect.

[Matticus91]

Originally Posted by dtla1

I think the main thing in OPs post is to note that the holes will be closed, which will indeed make the "second pipe" a straight pipe effect.

Correct that's the biggest part here, especially coupled with a DP

[miiiiiiiitch]

did you end up working out how to control the flap?

[Matticus91]

Originally Posted by miiiiiiiitch

did you end up working out how to control the flap?

Sorry man my car died and this whole thing got put on hold. I bought another 135i though and still plan to figure this out, just need to get some other things sorted first so I probably won't pick this up again until spring.

[Aimfor500]

Originally Posted by Matticus91

Sorry man my car died and this whole thing got put on hold. I bought another 135i though and still plan to figure this out, just need to get some other things sorted first so I probably won't pick this up again until spring.

super old post but...did you ever finish this? I'm interested. It seems like it'll be something like the Varex muffler.

[Matticus91]

Originally Posted by Aimfor500

super old post but...did you ever finish this? I'm interested. It seems like it'll be something like the Varex muffler.

Funny enough I just picked this project back up. The original plan wasn't going to work out the way I wanted so now I'm planning on an exhaust dump right between the axle-back and the mid-pipes. It will give me the extra sound I want at the flip of a switch, and will otherwise pipe through the Berk system. Total cost is about $300, a guy local to me did it and is very happy with the results.