Adding a 2nd muffler on a JD 790

[kebo]

Hey all, been away from here for a long, long while. Just sort of lost in interest in reading here but just got it back since I just picked up a sweet 2001 4x4 790 with Model 70 FEL and bar tires. Loaded it up and drove away for a cool $9500 exactly a week ago today, not bad huh? Clock shows a mere 388 hours and really looks a lot newer than its age.

To tell you about me some, ten years ago I bought an '81 JD 750 that was two wheel drive aand included a 4ft disc harrow for $4500. So, I came here and started asking a lot of questions since that was my first tractor. After using it for about 4 years, I traded that one and $1000 cash for an '84 750 that was 4x4. At that point I had about $5500 in the '84 model. Anyway, that one whet my appetite for about 6 years in which time I built up an even bigger appetite for more power and a FEL. Came across the JD 790 on craigslist a week and half ago and jumped on it like flies on a dog t**d. Couldn't be any happier about that purchase!

Anyway, as you all know the 790's have the muffler under the hood with side covers on it to help muffle the sound a little bit. These engines are also direct injection which usually doesn't have as loud of a diesel pinging like the indirect injection motors (on the 750's) have. To get to my point, I'm now 51 and like many folks our age have accrued some hearing nerve damage over the years. This has resulted in a condition known as hyperacusis, which basically means I'm hypersensitive to most sounds that wouldn't bother someone with no hearing nerve damage. I also have "distortion" which means that when I do hear sounds above a certain sound level it sounds like a I'm listening to a busted speaker cause it makes a "rattling" sound. So yeah, I've been wearing ear plugs and hearing protecters for several years now (around loud stuff) to protect what hearing I do have.

So my question is: I would like to quieten down the 790 just a little bit more if I can so I'm wondering if adding a 2nd muffler inline with the straight vertical exhaust pipe would quieten it down anymore? Or do you think it would be a waste of money and have little or no desired effect?? I still wear plugs with it, especially when I'll be running a bush hog, I just want to make it quiet as I can cause it really helps make riding it more comfortable and enjoyable for me. What do you all think about adding a 2nd muffler????

Oh yeah, I sold the little '84 4x4 750 through tractorhouse.com in just two days for a cool $5800! That included the 4ft Landpride bushhog I was pulling behind it because I'm planning to get me a 5ft bushhog for the 790. So, I basically got my purchase price back out of it and I'm quite happy about that too. Now I can go shopping for new bush hog!! Thanks in advance for any comments you folks can provide.

I'll have more questions to ask about the 790 but I'll bring them up later on. I did get the manual with it and have read it from cover to cover already (well, except for the spanish half of it) but it doesn't cover everything. Nothing in there about removing the FEL!!!
That will be another thread I guess....

 

[john_bud]

Dang Kebo, you perfectly described my ears!

I wear top notch shooting muffs around any thing loud. I also have trouble hearing in loud areas like bar, crowded room etc. It's wierd as I can make out conversations across the room, but not next to me.

ANyway, I would get a top notch Donaldson muffler. One of the coated models. You may have to do some farmerization to get it to fit and mate up. You don't want a straight thru design. You want one that has a blockage, but will need to upsize to keep the flow good. Probably have 1 1/2" pipe now and would be good to go to a 2" or 2.5" ID design. It should drop the sound volume and the tone down lower - deeper. The coated mufflers have an external coating that also makes them quieter. If you want it to be pretty, a stainless sleeve could be cheaply made and fitted to the outside.

jb

 

[SPYDERLK]

Isnt most of the noise from the engine itself and not the exhaust. Assuming your muffler is intact...
larry

 

[patrick_g]

Likewise the ear thing guys...

A second muffler will make it quieter but maybe not as much as you would expect. Lots of the noise is not in the exhaust note. Having the exit hole of the exhaust system farther from you and aimed away from you will help noticeably.


Mufflers emit noise directly from their walls as the acoustic pressure waves inside the muffler bang away on the outer walls of the muffler (like beating a drum.) It will be better if you can get the body of the second muffler away from you.

Pat

 

[Hooked_on_HP]

Insted of adding a second muffler I would replce what you have with a good quality automotive muffler. I did this on my tractor and made quite a difference.

 

[kebo]

Insted of adding a second muffler I would replce what you have with a good quality automotive muffler. I did this on my tractor and made quite a difference.

Now that's something I hadn't thought of! I will have to look at that pretty hard when I get back up to my parents house, that's where I keep my tractor at. Thanks!

 

[Mech]

I thought about a second muffler on mine but I just put an extension on instead to get the exhaust away from the loader arm. I decided most of the noise comes from the engine and echos off my canopy.

 

[dynasim]

Apparently(I don't have first hand knowledge), there are active sound deadening ear muffs available that are quite effective. There have been a couple of threads about them.

They work by actually cancelling the sound out. I am pretty sure the technology and concepts are valid.

Anyway, they would also help with the bushhog noise.

Chris

 

[dynasim]

Kebo,

I thought that you might have investigated them, but you never know. Anyway, good luck finding a solution.

Chris

 

[Diamondpilot]

I would be worried about back pressure problems with a second muffler.

Chris

 

[patrick_g]

There are noise canceling headphones like Bose etc (consumer grade) and there are NOISE CANCELING HEADPHONES, pro grade such as are sold via Sporty's pilot shop and the like.

Sporty's Home Page

Not cheap but effective.

Pat

 

[crashz]

The newer 790s and the 3005 have the exhaust routed to the front, under the engine compartment. I'm not sure if this is any better at reducing noise, but will allow easier attachement of a second muffler and will get the noise further from you.

You may also be unterested in using a sound deadening material on the side panels and hood to isolate engine noise.

 

[patrick_g]

Lead loaded foam is very effective for noise reduction. I used it to surround an Onan 12.5 KW air cooled diesel genset I mounted in a Helicopt Hut (environmental enclosure that fits on a deuce and a half) next to the two equipment operators (computer controlled microwave test gear.)

You can buy it in various thicknesses, with or without a thin layer of lead sandwiched in. They put fine lead powder in the foam acoustic insulation and it has a very high coeficient of extinction at frequencies of interest.

Pat

 

[kebo]

Lead loaded foam is very effective for noise reduction. I used it to surround an Onan 12.5 KW air cooled diesel genset I mounted in a Helicopt Hut (environmental enclosure that fits on a deuce and a half) next to the two equipment operators (computer controlled microwave test gear.)

You can buy it in various thicknesses, with or without a thin layer of lead sandwiched in. They put fine lead powder in the foam acoustic insulation and it has a very high coeficient of extinction at frequencies of interest.

Pat

Pat, is it pricey? Where can you buy it at?? Is it fairly heat resistant? Any danger of the lead leaching from the material? I guess you would want to wear gloves while handling it??

I had thought of lining the hood and the two side panels with some of that insulation that you used to see underneath car hoods. I'm sure it would help reduce noise being radiated from those three pieces of metal.
Thanks,
Keith

 

[patrick_g]

Keith, It was decades ago that I used the lead loaded foam. I thought it was moderately pricey but it has terrific performance so the price/performance ratio is really good.

The lead is captured in the foam plastic. I suppose if you cut it with a circular saw the dust could be bad but it cuts with a sharp knife too. I'd consider using some of the aluminum coated cloth or similar to protect the foam from the underhood environment. We didn't but after the project shipped I lost track of it and don't know how it held up over the years.

A friend of mine who lived on his twin diesel yacht a few boats down the dock from me when I lived on my sailboat had the wall between the engine room and his stateroom covered with it. It came that way when he bought the boat used so I have no A-B comparison data but from the engineering specs and my general acoustics background I'd say it would have made a very noticeable difference.

Remember, If you can see the muffler, you are going to hear it quite well. Mufflers do directly transmit a fair amount of sound right out through their sides and ends.

A HD steel box built around your current muffler and filled with sand between the box and muffler will deaden the mufflers sound transmission by quite a fair margin. Directing your original mufflers output pipe away from you and away from any reflecting surfaces will help a lot too. These two things may do as much as adding sound proofing under the hood and or a second muffler, not to be necessarily done instead but at least in addition to if not instead.

Finding lead loaded foam??? I'd Google.

I Googled on lead loaded foam and got -->

Soundproofing & Noise Control Materiels Prices

BARRIER: "Super Soundproofing Silencer (MLV) Mass Loaded Vinyl", "Limpid Mass Barrier", a heavy-duty wear resistant "mass loaded" vinyl mat with a foam ...
Soundproofing & Noise Control Materiels Prices - 74k - Cached - Similar pages -

Never underestimate the power of Google!!!

Pat

 

[RWolf]

Question I'd have is what thickness to use. I'm fixing to mount a 4kw onan genset (1800rpm) on my horse trailer and want to deaden the sound.

 

[Egon]

A friend of mine who lived on his twin diesel yacht a few boats down the dock from me when I lived on my sailboat had the wall between the engine room and his stateroom covered with it

Was this not a very common practice for engine compartments on small boats?

 

[Travelover]

...............
Remember, If you can see the muffler, you are going to hear it quite well. Mufflers do directly transmit a fair amount of sound right out through their sides and ends.

A HD steel box built around your current muffler and filled with sand between the box and muffler will deaden the mufflers sound transmission by quite a fair margin. Directing your original mufflers output pipe away from you and away from any reflecting surfaces will help a lot too. These two things may do as much as adding sound proofing under the hood and or a second muffler, not to be necessarily done instead but at least in addition to if not instead.

................
Pat

Sheet lead wrapped over a muffler really quiets it down, too, if you can find some. The exhaust manifold would probably be hot enough to melt it, but not the muffler.

 

[patrick_g]

Question I'd have is what thickness to use. I'm fixing to mount a 4kw onan genset (1800rpm) on my horse trailer and want to deaden the sound.

Richard, There are more issues to consider than thickness of sound dampening material. There are multiple sound paths. The method and materials used to mount the genset to the deck or whatever is also important. Vibration conducted into the deck via the mounts can be re-radiated as sound. To get a really quiet installation yo need more in the way of anti-bration mounts/pads than the ones that come on the equipment. A good Onan dealer should be able to get them or give you a source. If they don't know what I am talking about, don't be too surprised as lots of good ole boys don't.

The anti-vibration mounts go between the packaged unit and the mounting surface. They are are not too expensive for what they do. You need to supply certain information to the vendor of the pads to get the RIGHT STUFF for your needs. You need to tell them how much weight each pad will support (I guess I would assume half a tank of fuel if the tank is built into the unit) and the running RPM of the unit (this tells them the frequency band at which you want the mounts to operate.) These will isolate the vibration of the gen set from the mounting surface and make the installation much quieter.

Next, you can put acoustic dampening material (sound proofing) around the unit. Do be careful regarding the cooling air flow. I am not familiar with the 4KW Onan as I only worked with 12.5KW units. The 12.5's had kits available for shrouding the motor so you could duct the effluent cooling air to wherever.

The lead loaded foam plastic (lead dust in the foam) is a high performance material with greater sound deadening per inch of thickness than fiberglass and similar materials. It works sort of like R value with insulation, thicker is better. Higher performance is attained with thin sheets of lead sandwiched into the material (comes that way from supplier.)

If you have the space and inclination for a DIY project you can get good results for way less $. Build a double wall enclosure for the gen set and fill the space between the walls with sand. We used to do this years ago when we were building big high power speaker enclosures. You don't want the weight of the enclosure and sand supported by the anti-vibration mounts. You want the gen set enclosed by the double wall box but open on the side as needed for cooling air.

You will want the open side aimed away from the area you are trying to keep quiet. I put a louvered panel in the side of the "BOX" I installed the 12.5 into to dump the hot air and let cool air in. Since the intake air is a diffuse current and the effluent air is a strong current, separating the two so you don't recirculate the hot air was easy.

Hope the above helps. Feel free to ask any questions. Google should turn up sources of supply for the lead loaded foam or other acoustic dampening materials. The lead type is high performance but if you have the space a thicker layer of cheaper material may give more bang for your buck.

Pat