Quieting down a loud PV muffler?

[Grant Eaton]

I've had my 2nd generation PV muffler for about 1 month now. It has 2,000 miles on it, and while it has mellowed considerably, it is still too loud inside the cabin, even with the Dynamat I have on the roof and inside plastic panels! The worst noise is the chassis-rattling drone at around 30 MPH (1,500 - 1,800 rpm). It sounds just like blowing into a beer bottle, only you're stuck inside the bottle!

I really like extra acceleration kick and want to keep this muffler. So, what can I do to quiet it down without robbing too much power? There's a lot of information on the Web, but not much for people trying to quiet down a performance muffler.

Bsically I'm considering the following options:

1. Dual exhaust. I'm getting this for looks-improvement only. Perhaps it will have the side-benefit of channeling the sound out both sides of the rearend, and make things sound more balanced as a result.

2. Resonated tips. Some people claim they absorb noise, others swear they make the exhaust drone louder and more annoying. What's the truth?

3. A noise-control tip. I've only been able to locate one example on the Web. At $80, it's not cheap and it doesn't come with any scientific evidence for decibel control. However, the idea of using perforations or baffles to help absorb sound energy makes sense.


4. An additional noise control muffler (aka inline resonator). Hopefully this won't rob much performance. Perhaps it would be possible to insert one of these inline between the engine and the PV. Or even after the PV.



5. Noise control pipe baffle. This is susposed to be inserted between the PV and the engine. It's designed to reflect sound energy back into the pipe while maintaining air flow.



Any advice on how to get rid of the "beer-bottle effect" and quiet down the overall exhaust would be helpful. Thanks.

[FeatherFoot]

Grant,

sorry your having sound/drone problems, unfortunately sound has a tendancy to react differently to length size and volume and can change from car to car.

A resonated tip should get rid of the drone for you.

6 to 8 inches of perferation of the same size as the tailpipe should do the trick. If you go bigger, chances are you will aggravate the problem and much smaller seems to produce a sound similar to a cornered cat.

John

[Grant Eaton]

Originally posted by FeatherFoot
A resonated tip should get rid of the drone for you.

6 to 8 inches of perferation of the same size as the tailpipe should do the trick. If you go bigger, chances are you will aggravate the problem and much smaller seems to produce a sound similar to a cornered cat.

John

Thanks for the reply, John. So, it sounds like I should get this 3"x12" baffled tailpipe PLUS a 6-8" perforated resonator to put inline between the PV and the engine? The inline resonator should go BEFORE the PV, right?

I figure I might as well as go the extra mile and as long as they're going to be hacking the exhaust system apart to put on the dual tailpipes. Couldn't hurt to put on a noise suppressor tailpipe in addition to an inline resonator... right?





I know what you mean about every car being different depending on pipe length and other factors. You know that sound you get when you blow into an empty beer bottle? That's EXACTLY the way the inside of my cabin sounds at around 1,500 - 1,800 RPM. If I could at least get rid of that beer-bottle resonation effect, I'd be a much happier camper.

[WyrreJ]

Ever see the Blue Man Group? Their most performed show is called, "Tubes." And a good portion of it makes use of the fact that the resonance frequency of a tube changes based on the length, like slide trombones, except made out of PVC piping and generally much lower frequencies.

Anyway, the point of the story is that perhaps your muffler just happened to get installed at a nodal point that reinforces the frequencies from your engine such that you get the resonance really bad. Perhaps, all it would take, would be to move the muffler a couple of inches up or down the pipe so as to change the resonate frequency enough so that it no longer reinforces the sound from the engine.

Of course, I'm no mechanic and never took any physics beyond high school (AP level, but high school nonetheless) so I could easily be resonating out my ass here.

[Moncha]

That looks to be a very SOUND therory.. Actually, it just may work..
Grant, since the PV2 is shorter than the OEM Muffler, did you put an extender pipe before or after the muffler?

[chumone]

I get the "beer bottle" effect at around the same speed/rpm as Grant. Most annoying.

Let us know how the tip/inline perforator works, Grant. That drone is driving me nuts.

[WyrreJ]

Perhaps it would help if people with PVs installed could post the following three pieces of information:

1) New or Old style PV
2) Noisy or mostly Quiet
3) Extender pipe before or after muffler

Also, do the PV guys themselves have any recommendations for where the extender pipe should be installed?

I'm personally very interested since I have just days away from having my new PV installed. If position makes a difference, I'd like to get it right the first time.

[Grant Eaton]

Originally posted by Moncha
Grant, since the PV2 is shorter than the OEM Muffler, did you put an extender pipe before or after the muffler?

No, I don't believe an extender pipe was put in. I was just down under the VX today. I believe Midas pretty much just installed the PV at the same point where the OEM exhaust connected with the main system, within a few inches of the Y-pipe that unites the two exhaust lines. I will try to take a picture of it next week when the tire shop install my new shoes. It'll be easier to see when it's up on the lift.

[paultvx]

Pictures might not be of much value since it'd be hard to see where the mulffer is/should be placed.

It might be more useful to measure where the new muffler is attached... compared to the stock. Better yet... measure from some stock fixture along the stock exhaust (ahead of the muffler) to the PV. That way we'd all have the same reference point.

Recalling some high school and college physics courses, I think WyrreJ's theory is correct.

I find it hard to believe that they did not weld on an extender pipe. Isn't the PV shorter than the stock muffler? If that is indeed the case, they would have to weld on a pipe somewhere (ahead or aft) to make up for the difference in length.

If you're going to spend the money to have an additional muffler put in... then you might as well have started with a complete custom exahust system. I'd do what WyreeJ suggested before spending that much time and money.

[FeatherFoot]

Grant

Just the tip is needed. The reference to 6 to 8 inches of perferation is referenced to the inside of the tip.

John

[skullcap]

Mine just came the other day, so before I go and have it installed, probably at a friend's Meineke Franchise, are there any special installation pointers?

If the PV2 is shorter than the OEM muffler, to which end are folks having the extension attached?

Also, anyone have ideas for use of the OEM muffler?

I was thinking of maybe getting Martha Stewart to make it into a vase or something clever, since I hear she may soon be doing iron-work.

[kpaske]

I too have just become the proud owner of a new PV Muffler! Hopefully by the time I get home from my loooooong deployment overseas, a shiny new muffler and some other toys will be waiting for me. If anyone has some tips/advice as to the proper installation of this muffler, please post them for us!

[Dallas4u]

Any muffler shop should be able to just remove the old one and install the new one, whether it needs an extender pipe or not, that's what these shops do... mufflers!m Besides, an extender pipe is just a piece of exhaust piping, no big deal. If they don't think they can do it, or if you can't get out of there for under $50, then I would look elsewhere.

[paultvx]

Question is... where does the extender go... fore or aft. The more I think about it, WyreeJ's theory sounds better and better. Assuming the mufflers themselves were built to the same specs and standards, the placement of the muffler is the only thing that can vary in all the installations. It's the only thing I can think of that could explain why some are having resonance issues.

[Dallas4u]

Well, someone can test putting the extender before of after the muffler, but you may also run into mounting issues if you move the muffler around. I know mine is using the OEM mounting bracket and hole, so I am assuming there was an extender added before my muffler. I have a some-what loud grumble, but I'm happy with it.