Eliminating Exhaust Drone to quiet exhaust

[barnett468]

You have headers on, so that I would think would make your car sound louder too.

That is why I was wondering if I could go back to standard or HiPo manifolds and not worry about compromising the engine performance ?

if your car has a performance cam, you will have reduced performance with the hi po manifolds, and as i previously mentioned, it will still drone.

 

[barnett468]

The H pipe will not quiet it down very much at all . You need an entirely new exhaust system if you want a big reduction in noise.

True but if he is looking to get rid of the drone it certainly helped on mine. I like the semi loud (not going to get a ticket but you still know it is a muscle car) sound just didn't like that annoying drone.

Yes, I know a cross over will reduce, if not eliminate drone . This is because the engine pulses cancel each other when a cross over is used which is why I told him a cross over will help.

He is not only looking to get rid of the drone, he said he wants it a lot quieter which is why I told him a cross over and the side branch helmholtz resonators wont do much to quiet it down . In his case, I would simply do what is known to both reduce drone and make it quiet since that's what he said he wants and an just a cross over and/or side branch resonators and/or hi po manifolds aren't going to do that.

 

[c9zx]

It sounds like you are wanting to decrease drone (narrow frequency band) and quiet the exhaust (broader frequency band). It sounds like you already have a plan for the drone. Consider placing resonators in the system. Something like this http://www.summitracing.com/parts/wlk-24215/overview/ They should quiet it significantly without a lot of restriction. Getting to 70 db in the cabin with a 43 year old ragtop may be a bar set too high as that is very close to the cabin noise level of a 2016 Mustang GT hardtop at a cruising speed of 70 mph. Let us know what results you get as I'm sure others are interested in what works. Chuck

 

[mudbilly]

You have headers on, so that I would think would make your car sound louder too.

That is why I was wondering if I could go back to standard or HiPo manifolds and not worry about compromising the engine performance ?

if your car has a performance cam, you will have reduced performance with the hi po manifolds, and as i previously mentioned, it will still drone.

I'm waiting for the call from the muffler guy, hoping to pick it up with the H-pipe after work............

 

[mudbilly]

Well, The Drone is still there right at 2200 RPM, where it was before. But there is a 4DB reduction that makes it noticeable quieter. Max sound was 95 pre H-pipe and now it is about 91. It is also reduced 4 DB or more all over the RPM Range. It now below right below 80 Db cruising.

At idle, it is a little lower frequency @ 128ish Hz, it was 150 Hz, and still goes to that off idle and runs between 150 to 172 at cruising speed and where the drone is. This is consistent with what it was before the H.

That means that I am still going ahead with the Baffle. I was able to borrow a nice digital thermometer from work. it looks like a Volt meter and you plug a sensor into it that I could stick into the tail pipe. The exhaust is around 200 F, That means that the pipe does want to be about 26" long, just like stocktraders, if it is as forgiving as his over the RPM range, I will be in heaven ::thumb::

I hope to have it back in the shop next week for this installation.

The 5 gallons of sound proofing was at the door when I got home, so I hope to get this painted in over the weekend. So I'll report on how that works as soon as I can test drive.

The other day, before the H install, I did take a reading with the top down and it was also reduced a couple DB. I think that is because of the top being folded up in the cradle and acting to stop the sound from coming into the cabin from the trunk. I hope so, because is an area where I will be building in a nice sound break.

Baby Steps

 

[4mm]

The sound proofing was at the door when I got home, so I hope to get this painted in over the weekend. So I'll report on how that works as soon as I can test drive.

What did you decide to use?

 

[mudbilly]

What did you decide to use?

I went with the liquid so that I can slap in every part that I can reach with a paint brush. 3 coats will be 3mm, .12" thick. Biggest issue is making sure that everything is cleaned with denatured alcohol before applying so that it sticks.

I'm also going to be installing the noise barrier material when I box in the trunk.

http://store.secondskinaudio.com/spectrum/

Product Description

Spectrum™ is a water based under coating designed to reduce sheet metal resonance and structure borne noise. It is a true visceolastic sound deadener that can make any vehicle quiet as a luxury car.

Now made with Cryogenically manipulated polymers and high temperature wax, Spectrum is the only product on the market of its kind!

Spectrum can be applied as an interior coating on the sheet metal behind the upholstery, or as an acoustical undercoating on the outside of the floor pan to create tomb like silence and provide mechanical protection from rust.

When applied to the interior and exterior floor pan, Spectrum can reduce 300% more road, engine and exhaust noise than traditional OEM dampers and tar boards, all at half the weight.

*Spectrum is water based and will not adhere permanently to plastic or fiberglass without first using a self etching primer.

*Application surface should be dry and free from rust, oil, dirt and debris prior application. We suggest using denatured alcohol to clean the surfaces because it does not leave behind a film like degreasers do.

*Do not freeze and thaw more than twice. Do not mix until completely thawed. Do not apply product in temperatures below 50 degrees Fahrenheit.

Specification

Weight per wet gallon = 12.5 lbs.

Weight per cured gallon = 10.2 lbs

Coverage: 5 gallons = 50 sqft @ 3 mm thickness (2-3 Coats) Recommended

Appearance & Physical State Pigmented liquid/paste

Color Wet Blue/Black once cured

Solubility in Water Soluble

Layer Thickness 1 mm or 0.040"

Noise Reduction Uses...

Whether you are looking to quiet down your hot rod, or make your daily driver comfortable as a luxury car, Spectrum has proven to be the most popular & most efficient coating on the market.

Here is a quick lesson:

Much of the reducible noise in any car is structure borne, meaning it comes from vibrations, like a wind chime. Unlike wind chimes however, our cars are not tuned to any specific musical frequency, so what we end up hearing is the road noise, engine rumble and exhaust drone.

Stopping the vibrations on your cars metal panels is much like stopping a noisy wind chime with your hand. Once the vibrations stop, the noise stops.

Spectrum Kills virations in a very similar way. It stops the cars sheet metal from vibrating, thus, killing structure borne noise.

Once Spectrum has cured, the next appropriate step is to apply a noise barrier on top of the vibration damper. Noise barriers like our mass loaded vinyl barrier Luxury Liner Pro

 

[barnett468]

Geez, why don't you just buy a Mercedes, it would be a lot easier?

 

[EdM]

Geez, why don't you just buy a Mercedes, it would be a lot easier?

Brilliant.::thumb::

 

[Stocktrader]

I have a Benz. Its really not that quiet. But it will go 240 thousand miles before the timing chain breaks.

If you want quiet ride in a Lincoln town car.

 

[mudbilly]

update: progress but still working on it

Painting in the Spectrum was a pain in the butt. The actual application was not that bad, but the cleaning before hand was brutal. I did from under the rear seat to tail lights, including as much of the fenders as I could reach. 3 coats. They say to brush it on 1mm thick per coat, but I couldn't figure out how to "brush it" that thick, so I woud up "dabbing" on the first 2 coats and brushing on the third. This filled in some of the valleys from the dabbing. It is by no means smooth, looks and feels pretty much like the old undercoating that you used to pay the dealer to put on the underside of your car.

I'll post pics as soon as I get the car back from the muffler shop.

It did knock 2 Db off of the interior sound. It's around 74-78 Db from idle to 1800, 84 ish at 2000 and during the drone I am still getting 89Db though.

This is all with the rear seat in, but nothing else. Bare trunk, top up.

I next had a couple resonators installed right before the muffler.

https://www.summitracing.com/parts/vpe-1790

They did absolutely nothing for the low frequency pitch idle and drone noise. According to my spectrum analyzer phone app, what the did do was eliminate alot the higher pitched sounds. So now there is really only spikes on the frequencies that I am trying to eliminate. As is I don't like the sound as much as without the resonators.

That being said, the shop muffler guy is now working on the Helmholtz resonators. he has to re-run the tail pipes with some extra bends so that there is enough width between the sides to be able to get the lenght required. He is going to make them adjustable for 22-30 inch.

As a side note, when I parked the car there. There was smoke coming out of the hood. The power steering pump or hose is pissing fluid right onto the header. They also do general repairs, so I am having them fix that while the car is there.

Also, while taking to them about the dead ended pipes. He said that they just did something like this on one of his cars, I forget what model, but is new, and they sell after market exhaust systems with the Helmholtz resonators built in. It is folded back 180 degrees and runs right next to the existing exhaust pipe.

 

[barnett468]

update: progress but still working on it

Painting in the Spectrum was a pain in the butt. The actual application was not that bad, but the cleaning before hand was brutal. I did from under the rear seat to tail lights, including as much of the fenders as I could reach. 3 coats. They say to brush it on 1mm thick per coat, but I couldn't figure out how to "brush it" that thick, so I woud up "dabbing" on the first 2 coats and brushing on the third. This filled in some of the valleys from the dabbing. It is by no means smooth, looks and feels pretty much like the old undercoating that you used to pay the dealer to put on the underside of your car.

I'll post pics as soon as I get the car back from the muffler shop.

It did knock 2 Db off of the interior sound. It's around 74-78 Db from idle to 1800, 84 ish at 2000 and during the drone I am still getting 89Db though.

This is all with the rear seat in, but nothing else. Bare trunk, top up.

I next had a couple resonators installed right before the muffler.

https://www.summitracing.com/parts/vpe-1790

They did absolutely nothing for the low frequency pitch idle and drone noise. According to my spectrum analyzer phone app, what the did do was eliminate alot the higher pitched sounds. So now there is really only spikes on the frequencies that I am trying to eliminate. As is I don't like the sound as much as without the resonators.

That being said, the shop muffler guy is now working on the Helmholtz resonators. he has to re-run the tail pipes with some extra bends so that there is enough width between the sides to be able to get the lenght required. He is going to make them adjustable for 22-30 inch.

As a side note, when I parked the car there. There was smoke coming out of the hood. The power steering pump or hose is pissing fluid right onto the header. They also do general repairs, so I am having them fix that while the car is there.

Also, while taking to them about the dead ended pipes. He said that they just did something like this on one of his cars, I forget what model, but is new, and they sell after market exhaust systems with the Helmholtz resonators built in. It is folded back 180 degrees and runs right next to the existing exhaust pipe.

 

[barnett468]

.

Thanks for the update . It's fun to watch your progress and your info will help others.

 

[vozaday]

I ordered up some dynomax bullets for at the end of the tailpipe to try and eliminate my drone. In the mean time I just roll down the windows, zero drone that way.

 

[barnett468]

I ordered up some dynomax bullets for at the end of the tailpipe to try and eliminate my drone. In the mean time I just roll down the windows, zero drone that way.

I just drive my Lexus when I don't want drone.

 

[vozaday]

I ordered up some dynomax bullets for at the end of the tailpipe to try and eliminate my drone. In the mean time I just roll down the windows, zero drone that way.

I just drive my Lexus when I don't want drone.

Nice! That's why I'm keeping the stock muffler on my powerstroke, although it is getting deleted and tuned Monday with a whopping 1000 miles on the odometer.

Only reason I want to get rid of the drone is for the kids. Protect their hearing.

 

[barnett468]

Only reason I want to get rid of the drone is for the kids. Protect their hearing.

man it must be really bad, lol.

 

[mudbilly]

well. things did not go as expected with the muffler shop. There was no way to fit in what I wanted between the rear axle and gas tank.

So........................

I'm biting the BIG bullet. I'm taking the cam out and converting back to stock. That way I can get to install quiet mufflers and get the lack of noise I want. I'll sacrifice the HP .

I'm kinda bummed, but it is not like I'm racing, and it will still have enough power for my driving. I just keep telling myself that the vert is not a race car, it is a cruise car.

:blush:

 

[c9zx]

well. things did not go as expected with the muffler shop. There was no way to fit in what I wanted between the rear axle and gas tank.

So........................

I'm biting the BIG bullet. I'm taking the cam out and converting back to stock. That way I can get to install quiet mufflers and get the lack of noise I want. I'll sacrifice the HP .

I'm kinda bummed, but it is not like I'm racing, and it will still have enough power for my driving. I just keep telling myself that the vert is not a race car, it is a cruise car.

:blush:

The cam is not making the car loud at cruising speeds. Save yourself some work and just put on quiet mufflers. You'll lose some power at the higher rpms but not much at cruising speeds. Or, you could convert to electric power and really quiet things down.

 

[Hemikiller]

well. things did not go as expected with the muffler shop. There was no way to fit in what I wanted between the rear axle and gas tank.

So........................

I'm biting the BIG bullet. I'm taking the cam out and converting back to stock. That way I can get to install quiet mufflers and get the lack of noise I want. I'll sacrifice the HP .

I'm kinda bummed, but it is not like I'm racing, and it will still have enough power for my driving. I just keep telling myself that the vert is not a race car, it is a cruise car.

:blush:

Cam change won't help. It may change the frequencies, but not the overall issue you're dealing with.

I didn't see what you're running for mufflers, but in my experience, Flowmasters are pretty horrible for drone. I switched to Dynomax Super Turbos and was very happy with the noise level. I normally run them on just about everything now. Also had good luck with Hooker AeroChambers on a friends 383 Roadrunner - completely changed the car....