[Smooth_Operator]

So I'm contemplating getting a new exhaust setup for my car. Currently, the exhaust system is totally stock. I'm running MHD Stage 1, tried out the burble tune, hated it, and turned it back off. I have no proof (never bothered to run a log), but I swear it ran like garbage with the burbles on. Besides this, they were just a tad bit obnoxious for me.


I want my car to be louder, but not obnoxious. I'd rather just emphasize the natural sound of the engine than set car alarms off. One route that I'm thinking of would be going for a single exit setup. The F30 335i has two exhaust pipes coming out the back, however, I can't help but notice that all the exhaust flows through the single turbo, into the single downpipe, and then splits into two streams. Why the split? I know it's valved, and I think that it helps to heat up the cat. Or maybe it helps keep the turbo spooled up? Seems unlikely, considering it opens up in sport mode. Is this split really necessary? The cynic in me says that BMW just did this to provide a subtle difference between the 335i and the 328i, but of course I have no proof of this.


I do not plan on getting rid of the catalytic converter, nor do I plan on upgrading to an aftermarket catted downpipe in the near future.


I know I'm asking a lot of basic questions, but I've never modified the exhaust on a car before, and I couldn't find much information out there on single exit setups. I'd love to hear from anybody that has some insight on this.

[voxumf30]

The dual tail pipes help with removing the exhaust gases more efficiently. Dual pipes also sound better. Remember there is about an 80hp difference between a 328 and a 335, as well as a twin-scroll turbo vs a single. So getting the gasses out of the exhaust is a larger necessity in a 335. I was in the same boat with my 335, and went with catless downpipe on stock exhaust w/ stock burbles and it was enough for my liking.

[thejeremyman9]

Start with resonator delete for <$100. Though, it will be tame with OEM DP. If you do a single exit it will be custom exhaust work, look worse (subjective), and be more expensive than many other bolt/weld on offerings. A single exhaust of the apprriate size will flow just as good or better as a dual exhaust of the "equivalent" size (accounting for 1 vs 2 exits and cross sectional area) so its really a question of what is easiest and looks the best.

[AmuroRay]

I'd love to do a custom exhaust build on this platform - money no object:
4-3.5" Downpipe
3.5" connection to the mid pipe
3.5" Exhaust from the remainder back with a inline High flow cat
Y into 2X 2.5" nice Hemholtz "mufflers
and out to these tips:

Wouldn't say no if anyone wanted to build me one.

[thejeremyman9]

CG Precision used to make (might still) a 3.5'' outlet DP and 3.5'' exhaust to pair with it.

[DreamerJoe]

The split is just at the muffler point and i think they split it to have it valved, so it can be a little louder in sport mode but quiet in comfort/eco. Going to a single pipe wont have any benefits or drawbacks except for sound. If you want to improve the sound just get an axleback exhaust, or if you’re on a budget and just want it a little louder remove the resonator and leave the muffler alone.

[VGSON]

catless with vibrant resonator sounds really good.

My setup is 4" downpipe modded to fit 3.5 midpipe with vibrant resonator that splits to dual 3" that ties into mpe...With valves open it sounds really good. Nice deep, controlled tone that isn't obnoxious.

[VGSON]

Originally Posted by AmuroRay

I'd love to do a custom exhaust build on this platform - money no object:
4-3.5" Downpipe
3.5" connection to the mid pipe
3.5" Exhaust from the remainder back with a inline High flow cat
Y into 2X 2.5" nice Hemholtz "mufflers
and out to these tips:

Wouldn't say no if anyone wanted to build me one.

Ray, you're probably looking at or around 2k for a custom build like this.
These guys may get you part way there. https://4nmotorsport.com/products/3-5-custom-mid-pipe

[AmuroRay]

Originally Posted by VGSON

Ray, you're probably looking at or around 2k for a custom build like this.
These guys may get you part way there. https://4nmotorsport.com/products/3-5-custom-mid-pipe

Unless I go bigger turbo (one day? ehhh) I think I'm just going to settle here. But I can dream can't I?

Also, please upload sound clips!!

[VGSON]

3” on stock turbo is likely sufficient. we just did my buddies 340 with crappy 3” section(crush bend/alum) and picked up about 50ft/lbs..

I need to get better clips & will
post them up.

[AmuroRay]

Originally Posted by VGSON

3” on stock turbo is likely sufficient. we just did my buddies 340 with crappy 3” section(crush bend/alum) and picked up about 50ft/lbs..

I need to get better clips & will
post them up.

You have a graph I can see?

Can never go too big on an exhaust, but you can go too small. I would like to do one - but for 2K - a PS2 would give me more power. Together would be amazing...

[VGSON]

he showed me some of his mhd logs..noting an additional 70nm then prev. He’s big turbo, built b58... Didn’t do dyno. Shit cost $$ to dyno every lil change. Especially when every tuner is doing remote. We’ll probably do a group one in a bit after wedge finishes mine. Its like a couple hundo for dyno pulls around here.

I feel you on the $$ for exhaust work, but i felt it was worth it. Didn’t want to skimp after dropping what i did on everything else. You fixed the kink behind the dp and went 3” if i remember correctly. That is the most important part.