Well, my Road Runner which I recently re-acquired certainly has a drone loud enough to annoy my wife and it does bother me somewhat too.

Im pretty sure they are stainless flomasters right now, and I will confirm this tomorrow,

So I am looking for recommends on descent sounding mufflers with no drone.

It's currently a fresh 383, somewhat Lopey comp cam, with 2 1/2 inch exhaust to the bumper.

Please help so my wife will actually want to cruise with me

Get a nice factory type muffler from Accrete Exhaust. I remember when my RR had the factory mufflers, and it was quite until you stepped on it, and it didn't drone.

Accurate mufflers are nice sounding just like he says above. Prett quiet inside the car, mild rumble at the bumper at idle.

The stock aluminized ones or their magna (I think that's what it's called) hi po version? Pertaining to accurate stuff?

Keep what you have and add a pair of "cherry bomb" brand glasspacks alongside the rear leaf springs. O'reillys has em for cheap. the louvers are punched outward & the end nipples do not neck down where they are welded to the main case both of which are beneficial for good flow & they do work.

I put Walker quiet flow SS mufflers on the convertible.

Walker 22154 Quiet-Flow Stainless Steel Muffler, but it really was too long to fit well (29").

The Walker #21498 quiet flow SS (fits a 2004-2006 Chrysler Pacifica) show s to be 2-1/2" in/out, and just $64 from summit racing, just have to cut off the welded on muffler hangers. These are smaller 13" long case mufflers 20" tip to tip. Says they are a turbo style muffler.

Looks like the outlet tube may be angle cut for the exhaust exit? It could be cut straight and swedged to connect to the tial pipes?

Dynomax Super turbo mufflers, nice sound around town, totally quiet above 50 MPH.. No drone at any speed.

Headers or exhaust manifolds?

I run Summits stainless on my 440.They have a nice mellow sound pretty much straight thru but when crusing they are nice.Put them on at least 12 years ago and they still look pretty and shiny.That and no seams and were like 60 bucks each.Rocky

Put any cheap bullet glass packs in the tail pipes to deal with the drone.

I've got a 383 Roadrunner with 2-1/2 inch exhaust with OE manifolds and mild lump cam. The exhaust system that I've been using now for about 10 years is Flowtech. Aluminized steel which is all weldable. Very happy with performance. No drone and no blowouts after 10 years.

Oooops. Mufflers are Terminators.

Manifolds

Who makes a terminator?

To the other two who recommended adding a cherry bomb (essentially a resonator) how will this prevent drone in the existing muffler?

Just trust us, it WILL work (& it is cheap/easy to cut your pipes & add em in).

Any of the dynomax super turbo mufflers that have a 20" long case will
do what you want.

https://www.summitracing.com/parts/wlk-17748
https://www.summitracing.com/parts/wlk-17749

Terminator mufflers are made by Flowtech Inc. Do a Google search to see where the closest dealer is to your location.

The exhaust pulses going through the pipes create an unpleasant resonance. That resonance is the drone you hear.

Adding resonators modifies the resonation and reduces the effect.

Is this achieved by increasing back pressure? I never knew that it was the resonance in the pipe that caused the drone, always thought it was the muffler?. I'm just the kind of guy who really likes to know what's going on before I spend cash.. (Read cheap! Lol)

As and UPDATE TO ALL: they are currently a Dynomax muffler 20" long body and about 24 1/2 to 25" long from tip to tip of the inlet & outlet. The inlet and outlet size mic'd to be close to 2.5". Do they use ID or OD for determining what size inlet and outlet are? From their web the best i can say is they are the 17513 model.

It is also a welded muffler. Does mean it's stainless?

I'm not adverse to adding a resonator, but I really don't want to butcher the exhaust further if this does not cure it..

All this input is great! Please continue!

KEEP THE MUFFLERS, GET A NEW WIFE!!

Let's think about that for a moment.

Your muffler uses deflectors to bounce the exhaust gasses and their accompanying sound waves in one or more chambers. The pulses bounce and bobble around just enough to attenuate the unpleasant frequencies.

Resonators open up more paths for bouncing sound waves to follow. That attenuates more of the unpleasant frequencies.

Due to the shape of the glass packs the exhaust flows straight through with little interruption while the sound waves get trapped in the packing.

Okay. Ive done the manifold thing quite a bit. I have not tried the cherry bomb/resonator after the axle so I cannot speak to it other than anyone I know that has tried it says it works.

Here is what has worked for me: a factory type full length replacement muffler. That's it

I have used the Dyno Max Super Turbo in both the 747's and 748's sizes. Initially, there was almost no drone, but soon after the drone starts and builds as they age.

Also, your gear and car weight will either make it better or worse, relatively speaking. More gear and less weight, less drone. Similar system on my light weight 383/4 spd/3.91 gear car had considerably less drone than on my heavy weight /3.23 gear auto car.

Good luck

Feets , I could buy this logic and may try it, however great lengths were followed to restor it to pretty much OE correct with the cam, gear ratio, and exhaust essentially being the only deviations. I may just cave and do an oem style muffler to retain more of its 'authenticity'

BSB67. I think I'm leaning towards this (your recommendation) solution. My car is a non A/C post 69 runner, so what ever they weigh, I think 3300lbs?? With 3.91 gears and 4 spd. It is loudest or the most drone is between 1750-2000 rpm.

What mufflers have you used that represent a 'stock' solution, Accurate? Or other?

Mufflers are a lot cheaper.

Ding ding ding I do believe we have a winna.

I call it 1800 to 2100, but basically the same. I'm a bit surprised that this is a problem in your car. Not that it does not exist, but would be minimal because you can effectively drive around it or through it before it is annoying. The gear and 4 speed give you a lot of load/rpm flexibility.

I don't have part numbers. Both times there were aftermarket replacement mufflers. Once was Midas, the other was Walker brand from my friends muffler shop.

You are absolutely right in the I do have the liberty to just choose a different gear, but this usually just tends to leave my driving around in a gear low for the situation revving higher than what is necessary and burning more premium fuel, lol

Found a picture of the 22154s on the convertible, these are long..

Thanks for posting the picture. Those are big...

I welded collector flanges at the muffler outlets so I can drop the entire section from header to tail pipes.

You got an X pipe on it? Made a big difference on my dakota, helps more than adding two dynomax muflers after the 2 magnaflows did.

It Has an H pipe....

I'm trying to get a print of those mufflers from a buddy. I'm guessing they have 2" internal flow tubes.

That car weighs about 3600 pounds in stockish form. More if you have manifolds, buckets, stock iron intake.

I never knew but looked it up and most sources say 3435 lbs..

But the post is more about finding a quieter muffler.

When I google the 22154, I don't see anyone carrying it anymore? Maybe it got discontinued? Internally, it might me 2-1/4"? I do think it is larger than 2", and I can still hear the exhaust. I'll have to get a video with sound for these mufflers. Last video of the car was with the Super turbo mufflers that came with the TTI exhaust.

I had drone on my 73' Duster 340 using Flowmaster 40's, I did some research to find the best way to get rid of the drone, I found that Dynomax VT has a flap in the muffler that opens and closes with the pressure that is applied against it. This opening and closing of the flap removes drone. This is the same process that is used in SRT Chargers and in the HellCat. I put these on the Duster and drone went away and it sounds great. http://www.jegs.com/p/Dynomax/Dynomax-VT-Mufflers/1316158/10002/-1

Options to try:

A) Different mufflers ~ Dynomax Super Turbo's tend to knock a lot of bass out the exhaust note because of the flow path inside of them and are easily going to be the quietest performance muffler -- perhaps the cheapest option as well. If you have to have a straight-through muffler then look to the Borla "turbos". Either way, tuck the absolute largest case muffler that you can squeeze under the car. Muffling capacity/volume is going to be your friend here.

B) Add resonators or another set of mufflers as far back as you can.

C) Change up a section of pipe by adding an extra bend. If you've got a lot of long and straight runs in your exhaust those can promote standing waves in the pipes and set up resonance.

D) Tie-in an exhaust venturi in the longest straight run of pipe that you have. Don't put it in the middle of the run though, do it at 1/3 or 2/3's the length of the pipe.

E) Keep the exhaust the way it is and add a sound deadener if the resonance is from an actual panel, i.e. trunk floor, vibrating.

F) If all else fails, add a J-bend helmholtz chamber.

I've been in the same pickle as you. I have a car that I tried 4 sets of mufflers on to no avail when it came to quelling a resonance. It got expensive, labour intensive, and was a royal piss-off. I think your best and cheapest option would be to either swap out to a Dynomax/Walker turbo muffler, or add some form of resonator as far back as possible in the stream.

Best of luck to you killing the resonance!

Did the same thing on my Cuda. Works well.
Craig

I'm very sorry to hear that your wife doesn't want to cruise with you. The reason I chimed in was because we have the same car with the same engine and cam with 2.5" exhaust. I have a H-pipe in mine. Don't know what year RR you reacquired but even if it is an earlier one, I believe I can help you out. If you're still interested in the Flow Tech Terminators, I removed all of my clamps back from the exhaust manifold flange to the tips. I welded everything including the mufflers and the tips. No resonance, no drone no hissing and no rattling when you stomp on it. I bought these mufflers in 2006 and they're still on the car.

This. In many cars, especially the ones with full tailpipes, the drone isn't from noise out the tails - it's noise resonating through the body of the muffler, then into the floor pan of the car. Since we tend to try to fit the largest mufflers under the car, and install them as close to the floor as possible, this tends to increase the possibility of an exhaust drone. To over-simplify - sound doesn't pass "through" the muffler body, the noise inside is sound pressure waves that flex the metal body, resulting in sound pressure waves that are created outside the muffler body, and are then transmitted to the floor pans, causing a drone. And yes, sometimes changing or adding mufflers can remove the drone, by changing the sound pressure waves in the system. But I've had better luck removing drone by insulating the body of the muffler than by changing them, or adding a resonator. I usually do a layer of header wrap covering the muffler body sides, a layer of 22 ga stainless sheet, and repeat for a total of 2 layers of each, holding them on with the metal header wrap straps. I've also used old welding fire blankets and hi-temp fiberglass sheet for the sound deadener.

I can't guarantee this will fix every instance of exhaust drone - I'm just offering another method of eliminating it to consider that has worked well for me in the past.

Well, I received the print showing the internals of these today. There are 2 flow tubes internally, both choke down to 2" just like I thought. There is no packing for any noise absorption, & the flow tubes are not perforated. These babies are long - 25" long shells. These are NOT real good-flowing mufflers from the way the print looks, but adequate for a passenger car.

I didn't read the three p[ages of comments because the initial assumption is wrong.

Mufflers do not cause drone. The system causes drone. Similar to tuned headers or a tuned intake tract, the exhaust system has resonance and when the engine pulses excite that resonance, you experience drone. I've been in a few Men's rooms where it was easy to excite the resonant frequency by humming the right pitch. One I remember was at my old job, where the room was tuned to low "G".

So if mufflers do not cause drone, why do so many of these solutions work? Because they change the resonant point or else dampen the resonant peak's resonance to the point where it's not objectionable.

I suppose a louder muffler does have more of a tendency to drone, because the sound pressure (energy) is higher and more apt to resonate in an audible way.

Adding a crossover pipe or X-pipe can help too. I'd start there.

Dynomax Super Turbos 17748 and 17749 are my fvorites for 2 1/2" systems, if they fit. They are relatively quiet at idle or at low throttle pressure. With more power they take on more of an aggressive sound. I've received complimentws from strangers who tell me it sounds exactly right Upon startup, I was dismayed at how quite they were, but as the miles went by, they opened up a little.

So remember it's the system, not the mufflers.

R.

Dynomax Ultra-Flows and the only thing better than the Super Turbos to eliminate drone.

Just as an update, I ended up going with Accurate exhaust hemi repop mufflers, 2.5 in and 2.25 out. Drone MOSTLY gone. The range it used to really bother me in is gone but with the accurate stuff the drone does and can occur at a very low rpm. Thankfully I'm seldom in that range.
On a side note, the sound freekin awesome!!! Sooooo many compliments and I really love it now too. The best part of the sound is at idle, very throaty, when you're on it and giving it full throttle they are respectfully quiet. Not a nuisance muffler.

Happy with the purchase

if a set of mufflers will keep my wife out of MY! car i,m in for a set.

Sounds like everyone is happy/knows what to do

Glad to hear - and you've kept the H-pipe, right?

(I've got virtually the same setup as you used to have, 383/4bbl 2in H-pipe and FlowMasters with a wicked drone, but only right at 45mph.. so I just don't stay there much. Now I know what I'll do when it's time for a change.. but I think I'll drop the H-pipe too).

Cheers,
- Art

Art,
Yes I've kept He H pipe. Drone used to be real bad between 1700-2100 rpm. If I get some minor drone now it is around 1350-1400.

Do you think dropping the H improves that more?

Are you opposed to using resonators?

No.

Adding the H pipe made my exhaust note quieter.

How shall I say it?... The H allows exhaust shock waves from the firings of each cylinder bank to partially equalize before they hit the mufflers.

My FlowMasters are louder than I want, but I prefer the "style" of sound that comes from going without the H pipe. So I'll compromise by going with quieter mufflers and delete the H.

Best,
- Art

I have a basically stock 400 in an A-body and full to the rear bumper 3" TTI headers and exhaust with an "H". This car does not drone at all now. When it was installed initially I hadn't used the headers yet but the same 3" exhaust behind manifolds and an RV type cam was terrible drone. I asked TTI about it and wondered if I got the quietest muffler they had? They said that I was sold the quietest muffler they had. It is either Magnaflow or Dynomax. I told them what I planned to do when I got around to pulling the motor and they said wait until you put that big cam in it and those headers and all that will go away. It has. I think this has more to do with a performance type exhaust behind a low performance camshaft.

The Dynomax catalog says this:
100% Aluminized Inside and Out. Heavy Gauge, Hand Welded Case. Straight Through Design for Maximum Flow. Aggressive Sound Level with a True Performance Tone and Minimal Resonation. High Temperature Roving Fiberglass. Reversible for Versatile Installation. Lifetime Warranty. Made in USA

It's no wonder they are loud.

The sound of exhaust is the individual pulses of the gas from the exhaust stroke. There are two ways to reduce the amplitude of the pulses. You can dampen it which reduces the strength of the pulses, which nearly every muffler does, or you can use the pulses to cancel each other out. This works the same way that noise canceling headphones work. Flowmasters use this principle.

There may be some phase canceling in the dampening mufflers but I'm not familiar with it.

No muffler works by adding backpressure, but it happens anyway. A muffler designer usually looks for the greatest reduction in sound level with the smallest amount of backpressure.

To the OP: I suggest making the exhaust system quieter by using an H-pipe, then adding the glasspack resonaters under the trunk. The exhaust has lost temperature by then and so the volume of exhaust and its velocity are reduced.

R. I'm waiting for a former Walker employee to set this post straight.


































































Reviews

I too think it is from the manifolds and cam design, but not necessarily (or only from) a low performance cam.

just me I'd add the glasspacks & see what you gain, it'd be the easiest/cheapest.

I had a drone on my 6.1 Hemi '69 Cuda with full TTI H Pipe exhaust and Dynomax Super Turbo mufflers. Plus the exhaust was quite loud when cruising.
I installed a set of Flowmaster Resonators 15150S. Drone completely gone and exhaust much quieter. Very happy.
These resonators are a straight through 2.5" design with a closed tube alongside. Photos in this FABO thread http://www.forabodiesonly.com/mopar/threads/srt8cuda-build.218445/page-27
Jim

Not for nothing , but the state of tune of your car
WILL create or eliminate drone on some setups

What a-f do you cruise at ?

Air to fuel ratio changes will change
exhaust gas temperature which changes
the speed of sound in the exhaust gas
which will change the rpm at which the drone resonance will be loudest.

I had not thought of it before but pumping in cooler outside air into a hot exhaust system would change the rpm at which drone occurs. If a 12V air compressor was used it could be switched on/off to observe the effect. In a low backpressure exhaust system a forward facing "draft tube" might add enough air to shift the drone rpm.

We have discussed T junction stubs to cancel drone here on moparts.
The Flowmaster resonators in the post above have a stub of pipe inside the resonator case. It looks neater but you cannot "fine tune" the effect by lengthening or shortening the stub length.