Originally Posted by purin

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?
Performance was the main reason for me, some may prefer the additional sound with the secondary cat delete.

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?
If I truly understood then the issue probably wouldn't have occurred. I never took any exact calculations, I read that some other N54 owners arrived at the conclusion that the a 2.5" diameter branch resonator should be roughly 30-36" if mounted in near the location of the stock resonator IIRC. I didn't really have much space for those. I DID however have some vibrant resonators which I thought could double as a helmholtz, It was a long shot but I figured it would at least help... nope!

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.
An adjustable branch resonator is the best way to go IMO,

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.
That is crazy they are unaware what it is, I would NOT recommend have them work on your system, also tell them was Google is and where they can find it. lol

I like the concept of the branch resonator as it WILL cancel drone if calculated and implemented correctly. My system failed as it wasn't executed precisely but I knew that and was content with the results not being perfect as I "hoping it would help" I was pretty surprised when it made things worse.



-p

Originally Posted by purin

Evan,

I am not clear on the difference between a quarter wave tube and helmholtz resonator. Appearance is similar, function is different?
Branch resonators are the capped pipes, they are supposed to be the same diameter as the exhaust piping and are designed to cancel out a specific resonance. Helmholtzs are cannister/chambers which allow the soudnwaves to bounce a round a bit, they are not as effective at canceling a specific resonance but can reduce a broader range of drone.

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

Originally Posted by 535_ECOBOOST

very interesting. what did you find undesirable about your previous exhaust setup that made you want to change it?

Originally Posted by Abenlog

Evan,

I would move those modules if I was you. I had a spill in my trunk and ended up taking out two of them. It's pretty easy to do and can save you a lot of hassle down the line.

Originally Posted by ucsbwsr

I have heard horror stories of them being ruined by water, mainly clogged roof drains. I will probably go back in an drill a hole as a precautionary drain, it is probably the easiest and most effective way to go. Thanks for the heads up.

Evan

Originally Posted by Abenlog

I am still split on the exhaust system for my car. I just got the AR DPs done, and my wallet is hurting but the exhaust tip just fell off one of my pipes . I'm thinking about doing just a muffler delete for now but am worried about drone.

I wonder if the second cat will be enough to prevent that.

Originally Posted by Abenlog

Evan,

I'm finally going to be building this system soon! I think I'll be going for 3" piping throughout and follow mostly the same concept of yours.

To combat drone, I will be looking to purchase one of these

They are valvetronic mufflers that allows you to divert the airflow to cut down on nosie. I also need to find 3" equivalents of all the parts you used.

I wonder if putting the varex muffler instead of the magnaflow could resolve all of the issues?

Originally Posted by ucsbwsr

The stock resonator is very effective at keeping the system quiet and minimizing drone, There is increased drone with the muffler delete but it isn't terrible, although the db of drone can be measured and quantified it is still pretty subjective to the ears of the owner and their tolerances. I removed my secondary cat more for performance reasons than anything.



To confirm: you are going to run single or double 3" pipe? Those mufflers look cool, I wonder how much they impede exhaust flow when open and closed. Also, how well they work on different systems as with different diameter pipes, different locations, different exhaust temps, and different firing orders can all play into the end result. Curious to see how it works!

I have received my QTP valve, Y-pipe, and misc Vibrant V-bands, flanges, and gaskets. Now I am searching for a shop to handle the install. I really want to locate one with experience calculating and fabricating branch resonators so that A) they can build the initial system with room to install one (likely offset the 3" running through the middle of the car to accommodate) and build one if needed.


Evan