I was getting some pretty bad drone from my dual exhaust between 1700 and 2000 rpm. My wife finally complained enough I decided to do something about it.Did some research and found 1/4 wave branch resonators. It's just another piece of exhaust pipe that branches off your existing exhaust pipe or pipes at 90 degrees of the exhaust flow and is capped on the end. To get the right length you'll need to figure the wavelength of the sound at the rpm when the droning occurs, divide that by 4 and that's your length. the formula is pretty easy to find if you google 1/4 wave branch resonator. It worked beautifully though. It eliminated all the drone. Really cheap and easy to do too.

 

I've heard of these... pretty neat. Does it kill the loudness or just drone?

 

Seen this 5yrs ago on GM-Trucks.com where a guy was trying to eliminate drone in his Yukon Denali, also claimed it worked great.

 

How do you find the wave length? Have to mic it and view that on some software?

 

Ever notice the Drone eliminator on the 97-03 f150s? Same principal..

 

You first need to find the frequency. A v8 fires 4 times per rev so multiply 4 times the rpm that the drone is worst. Then divide that number by 60 to give you the frequency. Then divide the speed of sound by the frequency and that will give you the wavelength.
For example my trucks worst drone was at 1750 rpm so I multiplied that by 4
[7000]
then divide that by 60
[116.666] this was my frequency
You will need to know the temp of the exhaust behind the mufflers about where you will install your resonators. Mine was about 200*F. There is a sound calculator at http://www.sengpielaudio.com/calculator-speedsound.htm
The speed of sound @ 200*F is 1259.027 feet per second.
So mine was 1259.027 divided by 116.666= 10.791
10.791 being my wavelength. 1/4 of 10.791 is 2.697 feet which is 2' 8 3/8". That is my resonator length.
Alot of the info I found online indicated the resonators needed to be straight but after talking with some engineers at my work the assured me that as long as the connection to the existing exhaust was at a right angle, the rest of it could bend any way you need to make it fit. Mine is about 10 inches behind my mufflers. They come straight up a few inches then bend 90 degrees and run over my mufflers. And like I said before they worked perfectly. Hope this helps.

 

That's amazing. Great work!

 

and all aftermarket exhaust guys ignoring this Y ????? I think flowmaster , borla , corsa , BB, magnaflow , slp , need go back to school !!!!
they selling POS !

 

Some people like the drone.

 

I thought i liked it until my wife and I drove 10 hours to Savannah. I'm not sure what caused my headache [ the drone or her complaining about it ], but I had to do something!!

 

I had flowmaster for many years, in my cars.....after last 10 hours drive....NO more!
stock set up now. it is to quiet. but drive are relaxing , no pain.

 

More will say they love that sound than hate it.....

 

As others acclaimed, some enjoy it. I for one do enjoy hearing the exhaust consistently. No one makes a cat-back loud enough to suit me. If someone whines about the exhaust rumble, either A, put a resonator in the midpipe, or B, don't upgrade.

And, Corsa exhaust does not drone at all. There is more natural motor sound present through the dash panel than exhaust rumble while cruising.

SLP & B&B wasn't ever meant to be quiet either..

 

Just the drone. No change in the tone outside the truck, the loudness is still there. The resonate frequency that causes the drone has vanished though. I can actually hear the exhaust note that I worked so hard to achieve instead of that rumble in the cab.

 

Thats pretty neat, what about if you are true duals? would you have to make 2? and would it be two the same length as if it were single or do you split the length of it between the 2 sides?


^ it looks like a little can on a bracket right? i remeber mine. I transfered it from my stock exhaust to the next two setups after that, but somewhere along the lines i lost it, i wish i could find two more, made a huge difference both in drone and a rattle or two.