Cutting down on muffler drone? Any ideas?

[TerryBPP]

I have a magnaflow 3" in/ (2) 2.5" out dumper before the axle on my nitrous fed hemi. Problem is that there is a wicked resonance at 2000-2100 rpms which just happens to be my rpm at 70 mph on the highway. I don't want to pipe it out the side or the back as it looks really clean without exhaust tips showing.

I would mind adding a resonator or another small muffler inline with the piping. I figured this board could come up with something.

[Jims5543]

My 911 droned at 70 as well, I fixed the problem by driving at 80. At 90 to wind noise drowned out the droning.

[911pcars]

Terry,
Did you say you'd prefer NOT adding a resonator or add'l muffler? If so, I suggest replacing the Magnaflow with another muffler. Loud exhaust can be wearing on a commute ....... or consider wearing ear plugs, increasing volume of radio, etc.

Sherwood

[Tobra]

sound cancelling headphones, or get some audio guy to take a recording of your exhaust, and make you a tape loop 180* out of phase, would do the same thing

[TerryBPP]

Originally Posted by 911pcars

Terry,
Did you say you'd prefer NOT adding a resonator or add'l muffler? If so, I suggest replacing the Magnaflow with another muffler. Loud exhaust can be wearing on a commute ....... or consider wearing ear plugs, increasing volume of radio, etc.

Sherwood

wouldnt mind adding a resonator. I suck at the internet.

[911pcars]

Then a resonator it is. Adding some volume for the exhaust pulses to dissipate might work; relatively inexpensive as well. What happened to the cat?

Sherwood

[sammyg2]

I SAY Get rid of the magnasux and put the stock exhaust back on.

[Zeke]

This time I mostly agree with Sam, which ain't often. I like just a bit more noise than bone stock. Just enough to know what the motor is doing. At the first of the year, my trans in my truck started slipping in 3-4. It would hold at a steady pace, but if I hit it hard expecting a downshift. if acted weird. I wouldn't have caught it as soon if I couldn't hear the RPM.

Didn't matter anyway as the thing swallowed a bearing and had to be totally gone through.

[mschuep]

Is the resonance constant at that speed, but just louder?

Or, are you getting a drone that fades in and out, like a repetitive brrrrrmmmbrrrrrmmmbrrrrrmmm sound?

[Zeke]

What happens is there is a harmonic resonance in all systems at some point in the system. The more free flow, the more the sound will really drone at a specific RPM. I used to find that RPM on VW's and the '77 Targa I had, especially in tunnels. But to have that going on all the way down the road at your usual cruising speed would get tiresome.
One of M& K's early models was really loud from 3900 on. That kept me at 65 w/o looking at the speedo. (7:31 R & P)