N54 Custom Mid Pipe Thoughts

[delsap]

Let me start by saying this is more than likely due to the amount of time I have to overthink things while stuck in house.

Purchased my 09 135i from a friend back in June, the car came with a full Berk street exhaust and stock cats installed. Also included was the entire stock exhaust system. I loved the sound of the Berk when getting on it but I commute 2-3 hours a day and the drone in traffic was too much for me after a few weeks.

I swapped the OEM muffler (non PE) back on the car and left the Berk mids and did the golf tee mod. This got the noise levels where I would like but I guess I simply did not like the sound at all.

Next idea was to try the VRSF catless DPs with the Berk mids and stock muffler. Absolutely love it when I'm pushing it but around town I think it sounds awful. Only been on the car for a few days at this point tho.

My two favorite exhausts for the N54 are both single 3.5'' but would be far too loud for my liking. (BMR & HPF)

My theory is to run the DPs, try to purchase the Y pipe from the VRSF exhaust for e90/92 cars or have a replica made. This would get me from dual 2.5 to single 3.5" and also add a much needed flex pipe. Then I'd have a local shop taper down to a 3" vibrant resonator before going to the Berk street muffler which has a single 3" inlet.

Just for background the car has 92k stock turbos running MHD Stage 2+ with recent a walnut blasting, spark plugs, coil packs and index 12 injectors. AFE filters, VRSF Chargepipe with upgraded DV, VRSF 5" stepped IC

I've tried to find a video and there are a few people running 3-3.5" custom single exhausts but they were all N55 cars. Any input would be greatly appreciated as this has become more of a challenge than I had expected.

Hope everyone is staying safe and thank you!
Nick

[ErvGotti]

Back in 2010 I had a 3.5 in exhaust with "sport" muffler, from a now defunct company. Can't remember the name. All I can say is the drone on a 3.5 in exhaust is horrendous on this car, anyone who says otherwise is kidding themselves.

I'm now running catless DP's, N55 mid's and stock axle back and stage 2 turbo's and love it. A little louder than stock with little to no drone, but beastly when WOT. While certainly not as deep and throaty as the 3.5, I hated taking my car on long drives due to the drone.

[JM98]

I'm running a similar setup. VRSF Catless downpipes, Secondary Cat delete, Y Pipe to single 3 inch, vibrant resonator to AFE Mach Force axle back. Minimal Drone, nice deep idle and loud AF WOT

[Dackelone]

Don't mess around... just spend the money on a BMW Performance Exhaust. It will be the best decision you will make. It is a must have - really.

I tried using the N55 mid pipe on my N54 135i. The N55 mid pipe doesn't have secondary cats. They were quiet/bearable at part throttle... but at WOT they were LOUD. Very Loud. I also felt that I lost some low end torque under 2,800 rpm's. I switched back to stock N54 mid pipe. I thought the N55 mids would be a poor mans PE option. It wasn't. That was a 400 euro lesson - for those mids.

I then bit the bullet and bought the PE for a N54. Best decision I have made. Its so worth it. The exhaust kit ran me around 700 euros. So worth it.

Here is what my exhaust sounds like. I used an external mic mounted on the rear bumper. The PE is so special. Like I said a must have mod... along with the "CDV delete" if you drive a manual.

[delsap]

Thanks for the feedback everyone! Think this may have actually been my first post here so I genuinely appreciate the support.

Dackelone - Thank you for the video, the PE exhaust is 100% the fall back plan and I have no problem going this route. Do you have DPs in the video or is that just the PE mid and muffler? At this point I'd just like to hear what a 3'' mid would sound like and / or why not many seem to go that route.

JM98 - Do you have any videos of that setup you mentioned?

ErvGotti - 3.5'' all the way back would definitely be too loud for me, I was looking at the VRSF Y Pipe as an option for the ease of install and having my local shop taper down to 3" as soon as possible

[JM98]

Originally Posted by delsap

Thanks for the feedback everyone! Think this may have actually been my first post here so I genuinely appreciate the support.

Dackelone - Thank you for the video, the PE exhaust is 100% the fall back plan and I have no problem going this route. Do you have DPs in the video or is that just the PE mid and muffler? At this point I'd just like to hear what a 3'' mid would sound like and / or why not many seem to go that route.

JM98 - Do you have any videos of that setup you mentioned?

ErvGotti - 3.5'' all the way back would definitely be too loud for me, I was looking at the VRSF Y Pipe as an option for the ease of install and having my local shop taper down to 3" as soon as possible

No videos, I'll try and get one this week for you

[ShocknAwe]

Depends on what you want. I have dual 3" to single 3.5" to dual 3" exit on mine and aside from needing a drone pipe for 2200-2600 rpm it's quite tame due to massive resonator and a muffler in series with each other.

Until I step on it.

Then it sings.

[delsap]

Originally Posted by ShocknAwe

Depends on what you want. I have dual 3" to single 3.5" to dual 3" exit on mine and aside from needing a drone pipe for 2200-2600 rpm it's quite tame due to massive resonator and a muffler in series with each other.

Until I step on it.

Then it sings.

I'd like to avoid the drone because my commute is a nightmare.

It just seems odd that there are very few exhaust options with a single larger pipe since it should be cheaper to make and lighter while still allowing enough flow but I am new to this car and figured someone must have done this already but I have not found much on it.

I like the BMW PE but think it would drone too much with the catless DPs.

I'm considering replacing the two Berk resonators which I am pretty sure are just hollow 3" tubes with a magnaflow resonated X pipe and then throwing the Berk street muffler back on just to see what happens.

If that does not work I'm thinking of having some sort of 3'' resonated mid pipe made to work with the Berk Axleback.

Thanks for the help!

[ShocknAwe]

Muffler for volume, resonators for rasp. Pipe turns and bends and blind pipes for drone.

Not an exhaust fabricator but it sounds like you have a specific desire. If recommend finding a weld artist local to you and have it built.

[rac]

Originally Posted by delsap

Let me start by saying this is more than likely due to the amount of time I have to overthink things while stuck in house.

Purchased my 09 135i from a friend back in June, the car came with a full Berk street exhaust and stock cats installed. Also included was the entire stock exhaust system. I loved the sound of the Berk when getting on it but I commute 2-3 hours a day and the drone in traffic was too much for me after a few weeks.

I swapped the OEM muffler (non PE) back on the car and left the Berk mids and did the golf tee mod. This got the noise levels where I would like but I guess I simply did not like the sound at all.

Next idea was to try the VRSF catless DPs with the Berk mids and stock muffler. Absolutely love it when I'm pushing it but around town I think it sounds awful. Only been on the car for a few days at this point tho.

My two favorite exhausts for the N54 are both single 3.5'' but would be far too loud for my liking. (BMR & HPF)

My theory is to run the DPs, try to purchase the Y pipe from the VRSF exhaust for e90/92 cars or have a replica made. This would get me from dual 2.5 to single 3.5" and also add a much needed flex pipe. Then I'd have a local shop taper down to a 3" vibrant resonator before going to the Berk street muffler which has a single 3" inlet.

Just for background the car has 92k stock turbos running MHD Stage 2+ with recent a walnut blasting, spark plugs, coil packs and index 12 injectors. AFE filters, VRSF Chargepipe with upgraded DV, VRSF 5" stepped IC

I've tried to find a video and there are a few people running 3-3.5" custom single exhausts but they were all N55 cars. Any input would be greatly appreciated as this has become more of a challenge than I had expected.

Hope everyone is staying safe and thank you!
Nick

Hey mate, I got your PM and yes I still have a 3" midpipe although now I run single turbo 3" front to back with a 1x straight through resonator, 1x straight through muffler and twin-Y exit.

But I can answer your questions as I went through all the phases of terrible mods to the n54 with twins regarding sound until I landed on the best outcome for me.

The main problem with running twin mid pipes and having three cylinders segregated over that distance is the natural frequency you have created is just perfect for really cr8p drone in cruising revs. If you know anything about natural frequencies for sound you can calculate this yourself, but you don't need to know the theory to hear the outcome which is awful…

You have a few option to reduce the problem, if you run stock primary cats and secondary cats the distances are all different and gets you away from the problem. Running either stock primaries or secondaries on their own will reduce the issue as well.

If you don't want to run the cats then the best bet is to run a single pipe from the downpipes back. for me personally single back is by far the best sound, lets be honest, twin turbo's don't sound the best in the first place and that is as good as they will ever sound.... you also don't need to go 3 1/2" or 4". 4" is way to big. 3" keeps the velocity up to give you a slightly higher tone which for me is more pleasing to the ear and also makes fabrication easier for ground clearance. I don't think you need 3 1/2" but a lot keyboard warriors will tell you otherwise so if you feel so inclined so be it. Just note the tone will be more "ricer" and less "sporty".

To control volume then is just a matter of sizing muffler and resonator.

The other problem which you cant avoid with a straight through system is you might get some whistle and rattle noises due to the wastegates for the twin turbos. I didn't experiment with the mufflers for that but i'm guessing running stock primary cats or even some after market high flow cats would help prevent them seeing the light of day as you would need a proper obstruction to reflect those sounds back.

[delsap]

Originally Posted by rac

Hey mate, I got your PM and yes I still have a 3" midpipe although now I run single turbo 3" front to back with a 1x straight through resonator, 1x straight through muffler and twin-Y exit.

But I can answer your questions as I went through all the phases of terrible mods to the n54 with twins regarding sound until I landed on the best outcome for me.

The main problem with running twin mid pipes and having three cylinders segregated over that distance is the natural frequency you have created is just perfect for really cr8p drone in cruising revs. If you know anything about natural frequencies for sound you can calculate this yourself, but you don't need to know the theory to hear the outcome which is awful…

You have a few option to reduce the problem, if you run stock primary cats and secondary cats the distances are all different and gets you away from the problem. Running either stock primaries or secondaries on their own will reduce the issue as well.

If you don't want to run the cats then the best bet is to run a single pipe from the downpipes back. for me personally single back is by far the best sound, lets be honest, twin turbo's don't sound the best in the first place and that is as good as they will ever sound.... you also don't need to go 3 1/2" or 4". 4" is way to big. 3" keeps the velocity up to give you a slightly higher tone which for me is more pleasing to the ear and also makes fabrication easier for ground clearance. I don't think you need 3 1/2" but a lot keyboard warriors will tell you otherwise so if you feel so inclined so be it. Just note the tone will be more "ricer" and less "sporty".

To control volume then is just a matter of sizing muffler and resonator.

The other problem which you cant avoid with a straight through system is you might get some whistle and rattle noises due to the wastegates for the twin turbos. I didn't experiment with the mufflers for that but i'm guessing running stock primary cats or even some after market high flow cats would help prevent them seeing the light of day as you would need a proper obstruction to reflect those sounds back.

Thanks for the reply!

I agree that 3.5'' would be too loud for me. I am not looking to make the absolute most power, the car is already plenty fast for what it is so giving up a few potential ponies for a better sound is perfectly fine even if that means putting the stock DPs back in. That being said going to the stage 2+ map definitely gave the car even more go which is fun!

I'm torn between a magnaflow resonated X pipe after the DPs and then merge to a single 3" or putting a magnaflow resonated Y pipe right behind the cats and having a local shop run a 3" pipe back to the stock muffler? If it is too quiet with the stock muffler I have a Berk Street Axleback sitting in storage and I'd have room to add a small resonator if need be in the mid pipe to find a middle ground.

[rac]

Originally Posted by delsap

Thanks for the reply!

I agree that 3.5'' would be too loud for me. I am not looking to make the absolute most power, the car is already plenty fast for what it is so giving up a few potential ponies for a better sound is perfectly fine even if that means putting the stock DPs back in. That being said going to the stage 2+ map definitely gave the car even more go which is fun!

I'm torn between a magnaflow resonated X pipe after the DPs and then merge to a single 3" or putting a magnaflow resonated Y pipe right behind the cats and having a local shop run a 3" pipe back to the stock muffler? If it is too quiet with the stock muffler I have a Berk Street Axleback sitting in storage and I'd have room to add a small resonator if need be in the mid pipe to find a middle ground.

I have no experience with the x-pipe option on this car. But seems like a valid option. My recommendation simply because it worked out for me would be to Y at the base of the DPs and run 3" back to the axle back connection. Then you can swap axle back sections as you like or add a resonator to the midpipe if need be.

[rac]

and don't worry, you wont lose power going from 3.5 to 3".

[ShocknAwe]

3.5 is a sound preference and if planning to push a ton of air. You won't need it in 99% of cases.

[delsap]

I will eventually upgrade the turbos when they fail but I have no intention of pushing the car much past 450whp. I do not want to deal with upgrading the fuel system and all of the other ancillary bits to make big power properly. I feel like 3” should be plenty of flow for the stock twins even at a higher boost and potentially even good with something like the pure 600 turbos. Going to try to get this pieced and installed as soon as possible. MA just shut things down until May 4th so I’m not sure how easy it will be. I’ll be sure to post some videos whenever it happens.
Thanks again for all of the help!