[bryanc21317]

Hey,
Newbie here to the forums. Thanks for the help in advance.

i have a 2014 BMW 535i n55 PWG, MHD Stage 2 tune. Custom made Catted Down pipe, vsrf charge pipe/upper and lower, vsrf 7.5 inch intercooler, k and n drop in filter.

Recently I went to have the exhaust changed, they cut out the stock mufflers and added in Borla S type, which sound amazing. The issue I am having is between 1500 and 2300 rpms I have a horrible interior drone.


The Frequency is right around 104hz at 67db, so it is quite loud and annoying.

I took it back to the muffler shop and had them add 2 - Vibrant 12 inch Resonators model 1792 Bottle Style resonators yesterday, same thing. No Change.

I have these quad tips they also added, to make it look more aggressive in the rear.

https://www.amazon.com/BLACKHORSE-RA...a-643473555003

Can anyone tell me if the tips are not sticking out far enough? Any ideas on what MAY be causing the Drone?

I love the sound, but I can not deal with the Drone inside the car, so that will be a deal breaker for me.

Thanks for any help you can give me!

[Hoa]

Drone is common when you change both dp and exhaust. You will have to revert one of them to get rid of the drone

[bryanc21317]

So your saying there is no way to have the Catted Down pipe and the Borla S Type Mufflers without the drone?

What about adding a J Pipe?

Also, My muffler shop is telling me to drive it 1000 miles until the mufflers break in, has anyone ever heard of this?

Thanks in advance!

[Unspec]

A j pipe (otherwise known as a quarter wave resonator) should cancel out that specific frequency. Based on this article's calculator, a 104hz drone should be cancelled out by a 32-33inch J pipe.