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Exhaust Resonance

schiker said:
I haven't heard of the Helmholtz thing I have heard of resonators. I like the idea of the Helmholtz not restricting flow. I like the resonator's compactness.

A long time ago I saw a friend's Dodge with a resonator. IIRC my Dad's '72 caddy with 472 cubic inch engine had a resonator in addition to the muffler. Side note everything on that caddy was as big and heavy some even heavier than my 3/4 ton truck. That thing was a tank.

There are a few youtube videos of resonators. Saw one guy build a Helmholtz but he didn't install it. From this video, the FTE appears it has 2 paths for the air to flow and seems like a wing where it creates 2 paths and I am figuring it allows a speed differential and again I guess when they remix they cancel some drone.

I thought this was a good video. My truck drones but not near anything like this Dodge. AK does your truck drone approach this truck and then attenuate or vibrate the exhaust pipe to sound more metallic?


From my brief sound testing just lowering the frequency seems to make the sound more pleasant and seems to on this Dodge.
Click to expand...

Wow, big difference in the sound. Glad I don't have resonance.
 
Yeah, to me the resonator in my attached video makes the sound deeper and more pleasant. It seems quieter but its more a change in tone and takes out some of what I call/think is "pipe noise" what I imagine is higher pitched pipe vibration mixed with the air noise that is irritating and makes the dodge in the video sound irritating before the resonator. With the resonator, it's still loud but more pleasant to me. The 5.9 can get "blappety" sounding with big turbo and exhaust pipe. I think these air pulses tend to vibrate the exhaust pipe contributing the noise.

What brand exhaust do you have on it and type of muffler? I have whatever SS diesel supply sold ~ 12 years ago. Its a straight through round muffler.
 
The idea behind the fte is like a tuned port for a subwoofer box. Where the negative sound wave travels farther distance to get back into phase so it maximizes sound.

Only this is to minimize sound. Half the exhaust goes through the corksrew part and it takes longer for the exhaust to travel so when it mixes back together the sound wave of the 2 will oppose each other canceling out some of the sound.

Problem with resonance and being put on YouTube is think of recording studios. Ton of different microphones set up specifically for different instruments in order to sound as normal as possible as if you were hearing it in real life. If a single cheap microphone like one in a cell phone would work, they wouldn’t go through all that. A cell phone is going to cancel out exhaust resonance because the microphone is designed for vocal range which cuts out low frequency sounds on purpose.
 
I have an FTE resonator on my Tahoe. I installed it when I did the 4” exhaust which was the 2nd mod I did to the truck - the 1st being the Heath tune and turbo master. I can’t say how much the resonator helped since I didn’t ever run the 4” exhaust without it, but I never did have any drone at that level. It wasn’t until I added the intercooler that I got drone, so mine must be an intake tract problem and not an exhaust problem.
 
n8in8or said:
I have an FTE resonator on my Tahoe. I installed it when I did the 4” exhaust which was the 2nd mod I did to the truck - the 1st being the Heath tune and turbo master. I can’t say how much the resonator helped since I didn’t ever run the 4” exhaust without it, but I never did have any drone at that level. It wasn’t until I added the intercooler that I got drone, so mine must be an intake tract problem and not an exhaust problem.
Click to expand...
It may very well be the intake that old Helmholtz device that was on the intake when stock may fix it.
 
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