Exhaust resonance

[neverendingproject]

I put a dynomax muffler on my 2006, and I love the sound, but it resonates in the cab really bad at about 2200-2600 rpm (which happens to be cruising speed). I have downturns after the muffler. Other than changing pipe length, is there a way to reduce the resonance or change it to a different rpm?

 

[dyeager535]

Well, pipe diameter has some bearing on noise apparently, but that's a pretty expensive experiment. What diameter pipe are you running now?

 

[neverendingproject]

I'm running a dual 3" in/out muffler

 

[dyeager535]

Supposedly you can "step down" the pipe before the muffler. Since exhaust decreases in volume (hope I've got the terminology right) the further back you get, the less space you need to provide adequate flow. Actually you can help by keeping velocity up.

The one exception is of course any restrictions. Which a muffler is. Theory says that a larger than pipe diameter muffler of good design is of less restriction than if it were pipe diameter. So small pipe, big muffler in/out, isn't a bad thing.

But I'm not sure that would change the muffler resonance. I'd expect it would based on changing the exhaust pulses, but I'd be leery of shelling out the bucks to find out if a 5' section of 2.5" pipe before the muffler solves the problem.

I've always wanted to experiment with it, but unless you've got some spare parts or cash laying around, it's pretty difficult, especially if it's not a straight run of pipe you are replacing.

 

[Thunder]

Step the tail pipes down 1/4" and run them all the way out the back. Dumps right after the muff aren't exactly known for a quiet ride.

 

[Avery4jc]

My sister's truck resonates really bad in the cab at highway rpm's and it's fairly small diameter pipe (I don't know off the top of my head... 2.5" or so) and goes into two flowmasters under the bed and goes straight out the back into two tips... one on both side of the hitch.

My k3500 on the other hand is nearly silent at highway rpm (2200-2300) but it has large diameter pipe all the way back and a single muffler...

I think with exhaust there are just too many factors to have a set "fix"...

 

[toomany]

I think with exhaust there are just too many factors to have a set "fix"...

x2

My K5 has dual Flowmaster 2.50" Super 44's, and it resonates at certain speeds. But if I'm towing, then the speed at witch it resonates changes. Going up hill, without changing rpm's, the resonance changes (towing or not). There are just to many variables. I think it all boils down to engine load at that speed (along with muffler style). I would even say that the cam timing could have a play in it too, but I doubt it would be a very big part.

 

[4X4HIGH]

Tailpipes out the back will cure your problem. Exhaust turn downs are very loud and obnoxious (and illegal in California, not sure about Texas).

 

[rob h]

i have a flowmaster kit on my 03 hd and its 2 2.5 pipes into the muffler then into a 4inch out the factory spot...im going to change it to a 2.5 tail pipes and have them exit 45 deg each side....they say all the sound then is away from the compartment... my 83 has 3inch to the bumper and turndowns and is loud as hell...

 

[88k5blazin]

Tailpipes out the back will cure your problem. Exhaust turn downs are very loud and obnoxious (and illegal in California, not sure about Texas).

i always figured the same thing however when i first built my exhaust i had turndowns just to finish it up faster and get it back on the road and i never had a resonance problem then i got a ticket for not having them exit out the back and when i extended them they got ridiculously louder for some reason

 

[Avery4jc]

i always figured the same thing however when i first built my exhaust i had turndowns just to finish it up faster and get it back on the road and i never had a resonance problem then i got a ticket for not having them exit out the back and when i extended them they got ridiculously louder for some reason

X2... I'm not sure exiting out the back has as much to do with it. Like I said in my first post my sister's truck exits all the way out the back and it resonates like crazy...

 

[neverendingproject]

Well, I've seen articles relating to pipe length and exhaust wavelength, but I didn't know if there are dampners that could be used or not