exhaust drone/harmonic resonance

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Anytime you dump the exhaust under the car, you are releasing all the sound under the car which echos off the road and back to the bottom of the car.

Ever driven across an expanded (mesh) metal bridge?? Ya notice how alot of the noise of the car disappears??

Run full pipes out the back and some relativeley quiet mufflers and you will be much happier. Sounding like a Pro Stock car gets old really quick and dumps (to me) sound crappy on the street....
Ever realize why ricers sound like crap?? The exhaust system ends at the muffler. Listen to an old MG-B. The muffler is under the seat and there is about 3 foot of exhaust pipe after it.
 
I have Stock Manifolds with 2 1/2" Stainless exhaust X pipe runnig out to factory tips. I get the drone at about 2000 R.P.M. but it go's away at about 2500 R.P.M. Mine also has A833 four speed. Picture is before I changed to Stock manifolds,it's the same from there back.
 

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i think most of the resoance/drone problems are created by the whole buildcombo on alot of cars. mostly these phenomens are noticed when car is under some load and just under the range where the engine starts running right. so lower gears or less cam would probably solve alot of these things, just my thoughts
 
Dynomax VTs will get rid of so much resonation and roar you will not remember what it feels or sounds like. Plus, unlike stock, three-pass tube mufflers, they will let the engine run like it has straight pipes when it is wide open. Dad's wagon just ran a series of 117.5 mph passes and that is even slightly higher than it had typically ran with the straight-through UltraFlos (2.5") mufflers or his very large 22" by 5" by 11" XLERATORs. Most of his speed increase was due to the weight loss, (these are very light).

If you can spare the change, I'd jump on them if you are tired of all of the drone and roar.
Tom
 
I added Auger inserts-- Patriot sells them-- into the 2 1/2 inch tailpipes on my 65 valiant, From just behind the tire to the rear valance. HAd to trim them down fom 3 inch to 2 1/2 diameter to fit inside the pipe but they take away the drone ... For the days I want to be louder, I take those tailpipes off and put shorter turndowns,which exit behind the rear wheel, halfway to the rear.

Best of both worlds.

The inserts have to be welded to stay in place... but when they are on, my car is considerably quieter, unless you punch it.
 
Hi Mike, the good thing is Walker has been using the CRF acoustic material for 15 or more years now. It is very hard to get it to blow out and in fact, in most cases, where a car is driven a few thousand miles per years, it will not blow out. And with Walker being such a large company, they are very good about taking care of issues with mufflers, even ones with springs or valves.

The VT technology is actually production OEM stuff in Europe and Asia so it is going to be tested a lot harder than most of us ever will with our "drive now and then cars". But, I can understand concern with valves and springs in mufflers :):).

Take care and thanks for the comments.
Tom
 
340 swing said:
Here is what I have. Stock exhaust manifolds (70 340) TTI down pipes, TTI X pipe, Had dynomax super turbos took them off and tried spintech sportman 3000. TTI over the axle tail pipes and TTI tips. The car sounds great from the outside. But inside it hurts your ears annoying resonating just want to jump out kind of noise. I talked to Ron at spintech and he suggested trying resonators in the tail pipe area. There doesn't seem to be enough room. Has anybody had any luck with this? I have way too much money invested in this to give up on it, any ideas would be appreciated.
Click to expand...

Thanks for posting this....I have 67 barracuda coupe, mostly stock 360 w/340 manifolds. Here in the next week or so I am getting ready to order that exact same kit and have been wondering what those dynomax mufflers sounded like inside the car. Having been inside other cars with magnaflow muffers and felt like there was little to no drone I think I am going to give them a try.

Did you install the kit yourself...if so what did you think? Do the pipes need to be cut to fit or do they line up? Might be a good reason to buy a chop saw.


Having read this thread, I saw some of you layed sound deadener inside the car. Has anybody done a before and after test?? or even with a decible meter? I guess I am asking is it worth the effort and cost??

Thanks Jim
 
Jim, I installed the entire exhaust myself in the garage with a jack and jack stands. The system is made to fit the car. I didn't have to cut anything with the parts they supplied. The whole thing is engineered very well. My problem is the sound. I could not stand the drone and resonation inside the car. I changed the mufflers to spin techs. I had to cut the X pipe to install these they are a little longer. The drone is better but not gone. The spin tech sound is real cool but I still have have a drone around 2000 rpm. I originally had a factory exhaust on the car with 1 and 7/8 pipe? and some type of midas type no name mufflers with the stock tail pipes and tips. No drone real quite but it was shot, pin holes and real rusty so i thought i would replace it with a little bigger system to get a deeper sound. I have about $1400 into it and wish I went with accurate exhaust's stock system. Keep in mind I'm 45 and have a feeling if i was in my twenties i would like the sound or at least tolerate it.
Brian
 
I had a set of Walker Super Turbo Mufflers on my 72 Demon
with an aggressive solid lifter cam. The exhaust diameter was
2.5 in diameter.I had the mufflers mounted at the back of the
car with 90 degree turn downs at the rear axle. I cut the turn
downs at a 45 degree angle so the exhaust would blow out the
rear of the car.I never had any drone, even before i cut the
turn downs. I think i would cut out the x-pipe and see how
sounds.It seems most of the replies concerning a drone have
one thing in common, an x-pipe. It would be worth a try.
The turn downs were directly on the outlet of the mufflers.
 
scremn said:
I had a set of Walker Super Turbo Mufflers on my 72 Demon
with an aggressive solid lifter cam. The exhaust diameter was
2.5 in diameter.I had the mufflers mounted at the back of the
car with 90 degree turn downs at the rear axle. I cut the turn
downs at a 45 degree angle so the exhaust would blow out the
rear of the car.I never had any drone, even before i cut the
turn downs. I think i would cut out the x-pipe and see how
sounds.It seems most of the replies concerning a drone have
one thing in common, an x-pipe. It would be worth a try.
The turn downs were directly on the outlet of the mufflers.
Click to expand...

What heads and what motor?
 
Any updates??? For a drone free muffler with performance sound. I haven't ordered anything yet.

Totally different application but due to them advertising "No Drone" on there 2500hd mufflers maybe some of there car mufflers are drone resistent as well. I did have to replace the muffler on truck and used a flo-pro 2504 and it is drone free as advertised.
 
340 swing said:
Does everybody with the drone on this thread have an automatic trans? This is my first automatic car and the only one that has ever had a drone. Just a thought. I would be curious to see.
Click to expand...

Yup, a 727 trans , 383 Engine, daily driver..

Schumacher Tri-Ys, Flowmaster 40s + H Crossover = No Drone at any RPM.


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I know this is an old thead...
But I've still got a grotesque drone right at 1900-2100 rpm. I still have the same combo, mild 360, 340 manifolds, TTI H-pipe system into Dynamax turbos, with turndown tailpipe tips. I have added a full box of Dynamat, with no change.
I know that an H or X pipe is supposed to cure this exact issue, but I'm starting to think it's the cause. I've never had a drone like this before, but I've also never had an H-pipe before. Has anybody tried blocking their crossover pipe to see if it changes/cures the drone?
 
Dynomax VTs will take care of 95 % of the annoying drone you have Dusterglenn.

Where you live? Want to borrow my spare set?
Tom
 
dusterglenn said:
I know this is an old thead...
But I've still got a grotesque drone right at 1900-2100 rpm. I still have the same combo, mild 360, 340 manifolds, TTI H-pipe system into Dynamax turbos, with turndown tailpipe tips. I have added a full box of Dynamat, with no change.
I know that an H or X pipe is supposed to cure this exact issue, but I'm starting to think it's the cause. I've never had a drone like this before, but I've also never had an H-pipe before. Has anybody tried blocking their crossover pipe to see if it changes/cures the drone?
Click to expand...

I have had the same issue in the past and been able to eliminate the drone with straight thru glass packs next to the fuel tank.

I also had your exact exhaust setup on a E-body 340/727 with the same drone. Installed the TTI headers and it's gone. Like a different car now..
 
On the LX (new Charger, Magnum, etc) forums, a lot of people complain about drone, especially with the MDS on. A lot of us, myself included have found the Cherry Bomb Vortex mufflers drone very little to none and do not drone with the MDS on. They sound great, made my Magnum sound like a true Mopar. Those who don't like how loud they are add a pair of 12" glass packs. I think any chambered muffler is going to drone as there is no sound absorbing material.
 
I know that an H or X pipe is supposed to cure this exact issue, but I'm starting to think it's the cause. I've never had a drone like this before, but I've also never had an H-pipe before. Has anybody tried blocking their crossover pipe to see if it changes/cures the drone?[/QUOTE]


No X or H here, but I have a mandrel bent 2 1/2" exhaust with stock manifolds on a stock 69 340 automatic and the repop 2 1/2" tips.

First set of mufflers were the Summit turbo mufflers. Bad drone at 1800 - 2200 rpm. I swapped in the Dynomax Super Turbos and they sound almost exactly the same. Most people will not be able to tell the difference. Still has the drone at 1800 - 2200 rpm!

Anyone want to buy these Dynomax mufflers, they are for sale.
 
ive got the 3 inch TTI exhaust, dynomax super turbos, TTI headers, on a 400 HP at the wheels duster. same drone, and loud too. both inside and outside the car.

my thoughts are to use some header ccollector inserts, as there is NO room for resonators or bigger mufflers. im on a pretty tight budget these days, so the VT's are out for me as well.

anyone try these to reduce noise and drone?
 
I have hedman short tubes into 2 1/2 wth dynomax super turbos no h pipe , out the back through stock tips , no drone at all . Am able to listen to the radio at highway speeds , from 1900 up to 3,000 . Have 3:23 gears and automatic , no sound deadner , just what came from the factory .
Bought the car it had cherry bombs on it , no drone , just loud !!
So many variables , hard to track down with all the combinations , motor , gears , tires and transmission.
Good luck getting rid of the drone .
 
On the LX cars, some have a Factory X and some don't (they look like they so, but the one of the tubes is not cut) The system I have on my Magnum doesn't have an X or H. On my Dart I have an X and Warlock Mufflers, it sounds good, but I haven't driven the car, it will get tags and INS this summer and i will find out.

There are some header inserts you could put in the tailpipe/tip to help.
 
Looks like headers cut the drone.

I have 340 manifolds and dynomax super turbos with a bad drone.

Chime in with your set up
 
Glad I saw this thread. I installed the Summitt kit with their mufflers several years ago. Not a bad sounding system. Last year I installed an X pipe and it made my car quiet down. I was under it the other day and noticed one of the mufflers has rusted out so I'm looking at mufflers also. 340 warmed up, Hooker Super Comps, 2.5" pipes all the way to the bumper and mufflers installed in the stock location.
 
Kind of wish I had gone with the VT's instead of Ultra Flows, I've got a pretty decent drone around 2000 or so rpm. Solution = drive faster :D
 
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