I been doing some searching and the last few days came up with "another solution" possibly, everyone has the answer, but..... From what i have read in the past, Dynomat and all those systems, only help with heat and nothing for noise. My question is, has anyone ever tried the Solo J pipe, (as opposed to Solo J grip) on the axle back, or any other kind of J pipe ? Apparently it is big hit in V and Camaro forums, they are all satisfied, but find nothing in any Corvette forums. From what i read one could make their own, the measurements are readily available, would be a case of finding somewhere to bend pipe. i talked to a Solo lad and he says only thing is, has to be installed perpendicular, so that wouldn t be a problem for a reliable muffler shop. If it works, i m in, if not, may switch back to bi- modes.
Al

 

helmholtz resonators are nothing new. it's a gamble, and there's not a ton of clearance or room under the car for one. I'd be impressed if you found a way to add one without screwing with aero a tiny bit.

you could try it but it wouldn't be my first choice if drone was bothering me

 

Changing virtually ANYTHING in your engine or exhaust will usually affect the sound exiting the pipes (or coming into the car). It's all about sound waves and harmonics. I studied it in depth (or tried to, LOL) and found that it is its own science, very complicated.

Basically, in most instances, it's a roll of the dice.

Good luck with your experimentation!

 

I had a Resonator installed and it solved the problem, had no issues with clearance

 

Flame on the stock system but I like it. When its just me its open and yep, it drones pretty good but sounds nice to my ears.
Now with the wifey along I flip a switch and all quiet, she's happy and that makes me happy
NSF

 

This is how it works at my house

 

Yep, same here. NPP is the best invention since sliced bread.

 

Do you have any install pics of your resonator?

 

Can you give more infor. What muffler system do you have? Did you add 2 resonators to your existing system. That make model resonator did you add? Thanks


I spent maybe $1100 for my MidAmerica system with x-pipes...Yes I have drone.
My wife will kill me if I try to replace the entire system in less than 1 year. Adding 2 resonators to my system if possible is maybe a possibility.

 

I love the drone. The louder the better. I can also turn it off with a switch and carry on a conversation or listen to music at a reasonable level.

 

btt

 

No switch..100 %..

 

Resonator(s) will take care of the drone. We weld them in for customers all the time when they realize their cat less, basically straight pipe is really annoying (not on Corvettes)

 

NPP is the real solution. Keeps the spouse smiling and a huge difference on a trip from FL to Bowling Green museum trip. GM got this one right.

 

The NPP is one of those options that you didn't know that you needed until you have it and then you can't live with out it.

The OP mentioned that Dynamat is not really for noise control, on the contrary, Dynamat is specifically for noise reduction but it's more for road noise and reducing resonance in body panels. It is of only modest use in reducing exhaust drone and is not anything special for reducing heat transmission.

 

Any info on what resonator and where you weld that in? Every single other thread and reply on my drone thread just told me I needed different exhaust. Help!

 

Resonators will not fix the specific issue of sound wave resonance.

Those sound waves must be cancelled out via a Hemholtz Resonator. It causes the resonance waves to cancel each other out and stop for good. It's not a "roll of the dice" if your calculations are correct. There is room under the Vette to carefully weld one in. It will be a "j" bend, though.

NPP (when closed) or Corsa do not have drone.

 

Not sure why the OP says all the threads indicate Dynamat and other solutions only help with heat.

I've posted details before. Drone = low frequency exhaust sound + low mass vibration of interior panels in hatch area + resonance frequency of air chamber + physical shape of rear hatch.

Change any of these, and you impact the drone.

A higher frequency exhaust won't cause as much drone.

A convertible doesn't have the horn loading effect of the rear glass, so it's not as susceptible to drone.

Change the acoustic properties of the interior panels (mainly the plastic tub that forms the hatch floor), and you lower drone. This is what Dynamat, and other vibration dampening material are for.

Lower the amount of sound coming into the rear hatch, and you lower the drone. That's what sound barriers like ensolite, or the other closed cell foam insulators are for.

You can take your pick, but doing a couple of the above tends to work well.

I have the SLP PowerFlo exhaust, which sounds great, but caused really, really bad drone. Had to eliminate the drone, or switch out the exhaust.

I still have the SLP!

 

you are definatley correct on Dynomat helping with the noise, I posted in haste and just so frustrated with the drone I was a little over ambitious and stating that it did nothing, which is totally incorrect and bad post on my part. What did you do to help with the drone,did you line the floors and side walls with ensolite or dynomat ? I'm not sure where to go next I like them on the outside but they're brutal on the inside. Again I apologize for the incorrect statement.

Al

 

No worries Al - just didn't want people to get confused about the issue.

I lined the rear tub (floor and sides/wheel wells) with Dynamat Xtreme to dampen the material and stop it from vibrating (and creating noise). Then I layered ensolite over everything to block outside noise (including exhaust) from coming into the giant echo chamber that is the rear hatch.

Doing the rear hatch area will do the most for drone. It won't do much to make the car quieter, since most of the road noise comes from the doors and floor area, but it will keep the exhaust sound from getting amplified. I did the hatch first, and the drone was 80% gone. Then I did the doors, and the car is much quieter, and the drone's 90% gone.

When applying the Dynamat, covering 35% - 50% of the surfaces should be sufficient to dampen the panels. I did 100% cover, but mainly because I'm too lazy to cut up a bunch of strips of Dynamat. the 100% cover also should add a bit of additional sound barrier over a partial cover.

When applying the ensolite, 100% coverage is a must. It's like a wall of windows - if you don't close all of the windows, it doesn't do much to stop outside noise from coming in. There are other sound barriers which are better (multiple isolating layers, decoupling materials in between, etc), but they get reallllly expensive.

Most of the other solutions that people talk about fail because they're partial solutions. The block-it mat is a sound barrier, but it only covers part of the area exhaust sound comes in. Dynamat on it's own prevents the tub from vibrating, but does little to block sound from coming in. The insulation kits that some vendors sell use closed cell foam which blocks some sound, but does nothing for sympathetic vibration from the tub, so you still have two noise sources fighting the insultation.

I haven't experimented with different exhausts (hard to do a before/after comparison with the dynamat), but I know for the SLP PowerFlo, which is one of the worst drone offenders, the dampening material + sound barrier resolved the issue.