I need to know , what is a "DRONE"when it comes to installing an aftermarket exhaust? Also, which exhaust system has I guess a noticeable drone?

I'll try to explain what an exhaust drone is. Drone in the exhaust is due to the engine driving the exhaust system at its resonant frequency. You can't get rid of it, any length of pipe has a natural frequency, but you can change the frequency (RPM) it happens at. Stock exhaust systems are tuned to put the resonant frequencies outside the normal RPM range the engine is run in. Sometimes they add resonators for this purpose. To raise the resonant frequency of a system, shorten its length. To do this, you can try tail pipes that exit by the wheel (like GN's have), or you can try a muffler with a shorter internal flow path. If you have a true dual system, you can change the natural frequency of the system dramatically by adding a balance tube. If you can't shorten the system, then you can add slightly less than one wavelength of pipe. This will also raise the resonant frequency of the system. The wavelength in a single converter system (not true dual) is a little less than three feet at 3000 RPM. Shortening the system by a foot or so will move a resonance at 2000 RPM to about 3000 RPM.







Just kidding, I copied that. :p

Also, it can further be described as the constant exhaust tone heard in the passenger cabin at a given cruising RPM (as HoustonSRT8 describes). The amount and resonance that can be tolerated (or desired) varies by individual preference.

You are asking 2 good questions:

1) Houston gave a good tech description. From a practical standpoint, the drone is like what you might hear out the back, but IN THE CABIN, at certain rpm's. Some people don't mind it, but most do. It sounds mean at first, then can be very annoying as time goes by.

I'm usually the 1st to do an exhaust mod on my new vehicle, but Jeep did a pretty good job in finding a good balance on the SRT8.

So do your research for question #2 to what after market others are using.

I need to know , what is a "DRONE"when it comes to installing an aftermarket exhaust? Also, which exhaust system has I guess a noticeable drone?

My buddies Charger R/T had it BAD at 50mph...but I think they changed out the exhaust and fixed it.

We took a road trip, and I sat in the back. It was weird that it was really only at the certain speed....but it makes sense (frequencys and residence...)

My BB exhaust (loud option) has drone around 1700 rpm; and I love it!

If you're religious you experience resonance every day, the pipe organ at your church is just a big exhuast system that squirts sound down pipes of different lenghts and creates "drone" at different frequencies. (well, the old ones were, the new ones are all electronic)

Remember that even if you shorten or lenghten your exhaust, you could always fall into the next harmonic.

i.e. if your natural resonance (1st harmonic) is at 2.5 feet, then if you go to a 5 foot exhaust (2nd harmonic) you'll have the same problem.

For you non-emperical guys out there the physics behind it are pretty simple, use the fundamental equation (V = Lf ) , where V is velocity (in this case speed of sound through air about 1100fps), Lambda is wavelength, and f is frequency. I'll use houston's example he cited in his first post.

Assume root frequency equal to engine RPM, in his example it was 3000rpm. Convert RPM to revoltions per second for proper units.. thus 3000rpm= 500rps, assume sound to be 1100fps, thus Wavelength should be 1100/500= or roughly 2.2 feet. So if you were driving your car at 3000rpm with a 2.2foot exhaust system, you'd have a little pipe organ under your ass :D ... this would happen at all multiples of 2.2 for that given rpm. All exhausts have a resonance frequency, and there are other variables that come into play.

I have a slight drone with my Mopar catback (no headers) at 80mph through 85mph.
A description of drone may be that the exhaust gets much louder.:eek:
Bill

Okay, so a drone is pretty much the exhaust sound I guess right, it has nothing to do with the performance of the exhaust system correct? By the way thanks for all of the info guys! You all deserve a cookie and a hug from Jessica Alba! :)

I need to know , what is a "DRONE"when it comes to installing an aftermarket exhaust? Also, which exhaust system has I guess a noticeable drone?

Flowmaster 40 Series 2-chamber mufflers have a serious drone... hard to describe, the sound is similar to a locomotive passing by and the windows vibrate.

if you're younger than 35 you'll probably enjoy the drone.

if you're older than 35 you'll do everything to get rid of the drone.

annoying nevertheless...