bclexus

Exhaust Drone

Drone is that loud humming noise after you've installed your cool shiny new exhaust system around 1800 - 2200RPM depending on your final drive ratio. It's VERY ANNOYING for most and will drive your girlfriend (or boyfriend) right out of the car. So what is it? What causes it? What can I do about it?

What is it?

Drone is the word to describe a resonance phenomenon that offends nearly every type of material on the planet as a specific frequency range.

What causes it?

This sound frequency range is typically between 133 - 138hz for cars. This frequency sends the energy through the metal frame, body work, and everything in between (even seats in some cases) and shakes the molecules creating an awful humming sound.

What can I do about it?

Not much. You can't really block this frequency range because it is a natural resonance frequency. It will RATTLE EVERYTHING (even materials like wood and some softer materials as well). Dynomat in your trunk won't work. Dynomat on your floorboards or on the unibody underneath your seats won't work. This range of 133 - 138hz is incredibly difficult to manage. The best way to address drone is with muffler design or resonators. The factory mufflers are specifically designed to not only block but also CANCEL these frequencies.

PirelliRC

Oh ok i think i know what you guys are referring to. The only time that I get a bit of drone is when the vehicle is cold and you start the engine. For example, its been relatively cold here in L.A., dripping to the high 30s, low 40s at night, when i fire up the engine in the morning, i do get a little bit of that drone sound but it goes away after a few minutes when the engine warms up. I get no drone driving on the highway or at all. What i usually do is remote start the car about 5 minutes before i go outside so the engine warms up well. Its not good to fire up the V8s and bigger engines and just drive off while cold. If you do that sometimes when you hit the gas pedal, the engine almost chokes and hesitates a bit before it takes off. You can solve this by letting the engine warm up, and revving a bit before you head out to get everything flowing adequately.

bclexus

Drone happens at 'throttle lift' condition (that begins the process of coasting under no load yet the engine is still above idle speed due to being 'in gear'), which usually is heard the most when engine speed is around ~2,000 RPMs.

I can't believe you have never heard a boy racer Honda Civic with aftermarket exhaust droning...

PirelliRC

Maybe i misunderstood what drone is, if it only happens while driving then i am definitely not getting any of it. The only thing i get is the humming in a tin can effect that sick21 described. I get that while the car warms up. But nothing while driving.

bclexus

yardie876

I have a cat back on the GS and there is no drone whatsoever on throttle lift situations, if I understand you correctly. There is drone when you're on the gas in a higher gear and the RPM is around 2000 like you said. For example, if you're in manual in 5th or 6th and step on the gas, you'll get a nice lovely drone lol. The sound in every other gear makes the cat back absolutely worth it though.

PirelliRC

I would love to hear your vehicle, do you have a thread showing it by any chance ?

yardie876

don't have a thread. I'll dig up a few videos I have and post them up.

bigblack06

iTrader: (20)

Actually there is something you can do about it its a piece that attached to the exhaust to allow less drone within the vehicle, you attached a side part to exhaust to let some air out. There is a company just can't recall the name. Here is a link to basically what I'm saying start from post #35 on.

http://forums.corral.net/forums/gene...tely-gone.html