Revised Exhaust System: Inexpensive, High Flow, Acceptable Sound
 

Hey guys,

I recently revamped my exhaust system and wanted to share.

My last setup before this revision included:
Stock DPs > Vibrant 1792 (x2) > Stock Resonator > Muffler Delete (single pipe to dual tips)

More info on my previous muffler delete can be seen here: https://5series.net/forums/private-m...3/#post1539536


The revision consisted of:
Stock DPs > Magnaflow 11386 > Vibrant 1792 (x2) > Custom Muffler Delete.

This Setup varies from the previous one as the Magnaflow resonator is also an x-pipe; dual 2.5" in, dual 2.5" out. Dual pipes run through the secondary Vibrant resonators and eventually to their individual exhaust tips which are 3.5"od, flat black, and slant cut. The slant cut tips flow much better with the contour of my diffuser and the black finish ties things together.

One thing to note is I placed a small H-pipe just before the tips, where the muffler would otherwise be located. I really like the way the cars sounded when fitted with the Berk Race muffler, I contacted them asking what the small pipe/bridge was for and they said it lowered the exhaust tone. SIGN ME UP! I was intrigues with the concept and it seemed easy enough to implement. It is hard to tell if the lower tone is from the x-pipe or the latter h-pipe, either way the exhaust does growl a little more, especially at lower rpms.

The N54 makes great power but the noise it creates is underwhelming to say the least, very farty and just not very pleasant. I seems the more custom or free-flowing the exhaust system is: the worse it sounds in most cases. My goal was to create a system that flows well and doesn't sound terrible. Both resonators are straight through so the system can be viewed as a "straight pipe" system in terms of flow. The bends are crushed but I wasn't about the shell out the money for a full mandrel system.

Drone is up from before and it will be addressed since it is a little too much for my liking and I may replace the 12" resonators with 18" units.

My system retains the stock piping running from the DPs to the Magnaflow resonator and I may also replace that in the future since it has what seems to be an unnecessary amount of crushes. As the exhaust system sits (without DPs) it cost me roughly $500: Magnaflow=$100 Vibrants=$100 Tips=$100 Labor=$200. I am a sucker for deals and I am happy with this cost-value ratio. It is high-performance, aesthetically pleasing, custom, and doesn't sound terrible (I just can't bring myself to say that any N54 exhaust sounds good).

A few days ago I was able to install another piece to the puzzle: AR DPs. Below are some videos to give you an idea of the sound pre and post DPs. Once my car is back up and running I will take some better videos.

Hope this is informative,
Evan

WARM START + REVS W/ STOCK DPs

COLD START W/ AR DPs

https://lh4.googleusercontent.com/-2...o/IMG_2060.JPG
https://lh5.googleusercontent.com/-c...o/IMG_2066.JPG
https://lh5.googleusercontent.com/-q...o/IMG_2074.JPG
https://lh5.googleusercontent.com/-6...o/IMG_2068.JPG
https://lh4.googleusercontent.com/-D...o/IMG_2069.JPG
https://lh5.googleusercontent.com/-w...o/IMG_2072.JPG

I can't believe I just stumbled on this post!

Great work and very informative as usual. I have a couple of questions, though. Are you still runnning this revision? Did you ever get around to changing the resonator to the 18" unit to reduce drone?

I have AR Downpipes going in soon and wanted to do my exhaust at the same time. Ideally, I'd like to do a quad exhaust and the 2 outlets from the resonator. I guess this means I won't be able to do the H-pipe, which sounds very intriguing as I am after that low RPM growl, just like you.

Another picture of the exhaust system from underneath would also be greatly appreciated, thanks!

A few months ago I replaced my 12" Vibrants with longer 18" versions, it softened the exhaust sound and made a very small impact in drone, less of an impact than I was hoping for. I think the larger cabin of my E61 magnified the drone.

With my goal to eliminate drone outstanding I looked into other options and it seems the absolute best way to eliminate drone is to build branch resonators. The concept and construction is simple but calculation can be tricky and needs to be precise in order to work well.

The isn't a whole lot of extra room below for exhaust piping. Based off what some other people have done on N54s it looked like I would need about 3.5' of resonator for each pipe. Fitting that would be very tricky so I went a different route.

As my original Vibrant resonators were laying around without use I had the idea to use them as makeshift helmholtz resonators. The cans are 12" and 4.5" dia in the middle. I figured with their added volume and sound deadening material (which may act like a stuffing in a sub enclosure and mimic more air space) that the overall volume may be in the park of what I need .

*As I am typing this I can see how my plan was flawed on many level, it is not wonder it didn't work*

I had the 2 Vibrants capped and mounted in the muffler delete section. The execution was great but the results were horrible, drone was much worse at idle and at the "normal" rpm ranges of 2,100-2,500, really bad. The helmholtzs were pulled along with my mini H-pipe and now the 2 vibrants are being used in their traditional manner where the muffler once was. Currently drone is similar to where it was originally. Back to the drawing board.

Evan


A better pic of my original setup: oem catback piping, Magnaflow resonated X-pipe, 12" Vibrants, H-pipe muffler delete.
https://lh3.googleusercontent.com/-7...2/IMG_2300.JPG

18" vibrants replacing 12"
https://lh6.googleusercontent.com/-z...2/IMG_6144.JPG

Original muffler delete with H-pipe
https://lh6.googleusercontent.com/-7...2/IMG_6146.JPG

Experimental Vibrant Helmholtz! Bummer they didn't work, maybe if the cans were gutted it would be more effective?
https://lh4.googleusercontent.com/-X...2/IMG_6149.JPG

The "Vibrant Helmholtz" where just unnecessary weight any way and a restriction of exhaust flow.

Thanks again for the thorough post.

It seems to be that you're on the right track with the side-branch resonator, but it needs to be fine tuned. Perhaps talking it over with an experienced exhaust guy?

I am going to talk to the shop nearby me and see what input they can give.

Where are you seeing the most drone with the system (without the capped resonators)?

I thought branch and helmholtz resonators don't impede exhaust flow as they are capped and don't allow anything but sound waves to enter. Am I mistaken?

The weight is not much of a concern, the resonators are about 2lbs each so I would guess 5lbs total with connecting pipes, I can put that much weight in my belly during a meal! lol


Most of the drone occurs between 2,100-2,500rpm with while under mild-moderate throttle. It may be difficult to accurately calculate a branch resonator with my "unique" exhaust setup. I really like the idea of a branch resonator though, if drone was reduced I would consider pulling the other vibrants to allow some more unfiltered exhaust sound.

I have had thoughts of installing a performance muffler which has an internal helmholtz but the concept of running essentially "straight-piped" exhaust with resonators seems like the way to go for performance.

I agree with you that the branch resonator is the way to go. There has to be a way a high end shop could do all the necessary calculations to fabricate an exhaust that eliminates the resonance from that rev range. I will talk to some people locally and get back to you.

Hey brother how are you and the belly weight is so true!! :D


What I was referring too is that the resonators, imho, should be connected in the straightest form ie 45 and not 90 as they are in the picture. With a turbocharged engine the less exhaust flow restriction you have is best and I have experienced the dreaded "drone" myself and it gets tiresome very quickly. Have you considered a small and short racing muffler that can be hidden before the exit tips and is unseen, that could be an option simply because the resonators could be the culprit of the "drone issue"?

Evan,

thanks for the links to here, very helpful.

I have the OE secondary cats and resonator, and only catback exhaust. If we are just trying to tackle drone, this branch could be our solution correct? Is there a reason besides performance to swap out the secondary cats and go with the vibrant + branch for drone control?

Not sure if you guys saw this but good info here and other sites.
Fancy Tech: How to Get Rid of Exhaust Drone, works great! - Nissan 370Z Forum

It seems that a no-packing capped pipe about 28~30in seems to be working where the drone is in the 2~2.8k rpm range. Identifying the drone frequency seems to be the key via some recording/analysis process. Some of the guys are talking about filling the cavity like a resonator so not sure why your trial made it worse.

Can you help me better understand why your vibrant helmholtz didn't work? Is it because of the resonating material inside the capped canister didn't reflect the soundwaves back to cancel out? Was yours too short?

I have not tried yet but theoretically, the concept should work based on the length and pipe size right? I was thinking about incorporating like a trombone slide concept to tweak the length of the pipe on where it should be ultimately sitting.

I am like you trying to find cost effective (cheap) solutions and DIY as much as possible. The shops in my area that I have reached out to have not heard of any branch method to kill drone or not going to the right ones.



-p

Evan,

I am not clear on the difference between a quarter wave tube and helmholtz resonator. Appearance is similar, function is different?

To determine the length of what we might need based on what frequency drone we have can be calculated here. Remember you have to convert from inch to meter to use the calculator
Quarter Wave Tube - DiracDelta Science & Engineering Encyclopedia

I think I will try try to record and do the audio analyzer to see what it actually records at when I get my car back from the shop.

Some additional reference if anyone is interested:
Branch resonators - ways of reducing exhaust drone - Page 7

Exhaust Drone is Completely Gone - Page 2 - Ford Mustang Forums : Corral.net Mustang Forum