Mufflers Without a Drone

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I have 3" dynomax now with TTI Headers and Exhaust - they're terrible. Switching back to Goerlic Accelerators. I had the xcelerators with my 2.5 system and they were much better.
 
I pulled my Dynomax Super Turbos from both my cars and went with Hooker Aero Chambers. Best sounding/performing muffler I ever had. You can see right through them too. They are quiet at idle and part throttle, and not too loud at wide open throttle. I'm I big proponent of using oval-shaped exhaust tips to sweeten the sound of an exhaust system. Same principle as horns at work there. Makes for a smoother, less harsh sounding exhaust note.

A buddy of mine added a pair of 28" long tubes to his exhaust starting just behind his crossover. They are welded to his main exhaust pipes and must have a flat cap on the end. It cancels the sound waves and eliminated all his drone issues. It looks cool too.
 
I have read that the car manufacturers sometimes use two mufflers of slightly different lengths, or of slightly different internal constuction on dual exhaust systems in order to cancel out drone. Might be worth trying?
 
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. Some aftermarket designs such as Borla's and Corsa's offerings do the same job. Borla's design cancels out some of these frequencies as well as ensures that the sound energy is going out the tailpipes. Corsa's designs have an internal chamber that is of the correct length to cancel this frequency out using the laws of wave reflection.

Designs like the Magnaflow Competition Catback that uses a 5"x14" resonator to attenuate the engine sound drone like a mad cow. Flowmaster American Thunder mufflers drone like crazy because they were designed to produce a specific sound that was focused on the outside of the car. There's nothing wrong with this, it's just what the manufacturers decided to produce. If you have an exhaust system with one of these such designs and don't want to change your entire system, then a set of straigh through race mufflers such as Dynomax Race Bullets or Pypes M80 mufflers will give you some relief but may not completely eliminate the drone depending on your overall setup.
 
69_340_GTS said:
I have read that the car manufacturers sometimes use two mufflers of slightly different lengths, or of slightly different internal constuction on dual exhaust systems in order to cancel out drone. Might be worth trying?
Click to expand...

yup my 87 mustang has two different length from the factory mufflers on it. thats how ford got rid of the drone in the 80's. sure others have done it also..
 
Pontiacs did it long ago to compensate for differences in exhaust gas flow due to the heat riser valve ( different length mufflers).
Tom Hand
 
Mopar Tim said:
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. Some aftermarket designs such as Borla's and Corsa's offerings do the same job. Borla's design cancels out some of these frequencies as well as ensures that the sound energy is going out the tailpipes. Corsa's designs have an internal chamber that is of the correct length to cancel this frequency out using the laws of wave reflection.

Designs like the Magnaflow Competition Catback that uses a 5"x14" resonator to attenuate the engine sound drone like a mad cow. Flowmaster American Thunder mufflers drone like crazy because they were designed to produce a specific sound that was focused on the outside of the car. There's nothing wrong with this, it's just what the manufacturers decided to produce. If you have an exhaust system with one of these such designs and don't want to change your entire system, then a set of straigh through race mufflers such as Dynomax Race Bullets or Pypes M80 mufflers will give you some relief but may not completely eliminate the drone depending on your overall setup.
Click to expand...

You can put branch resonators on the exhaust pipes which are tuned to the drone to cancel it out and keep your existing exhaust system setup. I didn't remove any of the exhaust system to install them. My drone was at 125hz and I took care of it by putting on the side branch resonators. Here's the page of the thread of my drone journey where I put them on with how I did it http://www.forabodiesonly.com/mopar/showthread.php?t=202506&page=3
 
lil red said:
I ran the old thrush turbo 400 for years...cannot find em and tried flowmaster, and magnaflow and both are too loud and drone...switched and bought dynomax super turbos

there not bad, quiet at idle and nice steady rumble at 3000 rpm at highway speed, no drone but a little loud at WOT for my liking....but my exhaust does dump right at ear level outside my windows. 2 and a half inch headpipes and 2 and a quarter tailpipes
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Hey lil red get those duals out back where they belong, and change those 2 1/4 tips for
2 1/2 tips. this should make a difference.

Somebody said this:Borla XR1's for me too, great sound and built to last and no drone. Sounds like a plan, but not a cheap one.
 
Here is a link to one of the cars we built last year in my shop. Yeah I know it's not a mopar. But you can hear the exhaust. It a stroked LS2.
[ame="https://www.youtube.com/watch?v=wpHLXMqbXP4"]Ride with me in Silverback - YouTube[/ame]
 
jbc426 said:
I pulled my Dynomax Super Turbos from both my cars and went with Hooker Aero Chambers. Best sounding/performing muffler I ever had. You can see right through them too. They are quiet at idle and part throttle, and not too loud at wide open throttle. I'm I big proponent of using oval-shaped exhaust tips to sweeten the sound of an exhaust system. Same principle as horns at work there. Makes for a smoother, less harsh sounding exhaust note.

A buddy of mine added a pair of 28" long tubes to his exhaust starting just behind his crossover. They are welded to his main exhaust pipes and must have a flat cap on the end. It cancels the sound waves and eliminated all his drone issues. It looks cool too.
Click to expand...

X2, pulled out the dynos and installed the aero chambers. *** kicking muffler with great breathing capabilities.
 
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