Making a standard Gen Quieter

[foontoon]

I have been researching how to quiet down a run-of-the-mill portable generator. I have a fairly quiet Kipor 3500 but even it could stand to be a little less noisy (depending on where your dry camping). I found a post of someone who modified their Kipor and will do the same when I get home since we are traveling now. Besides this however, I'm experimenting with quieting down the low end generators. For one thing, some of them have larger fuel tanks than the quiet gens and there is a larger range of power selection to choose from. 3,500 watts just barely does it for my application and I really could use more like 5,000 or 6,000 watts. I also want to leave it in the rain and it's easier for me to leave a cheap generator in the rain than a nice inverter sytle quiet Yamaha or Honda. There are some other reasons that I'm trying to get a standard gen quieter that I won't bore you with.

On one forum, I read a suggestion of diverting the exhaust into a 5 gallong bucket of water. The idea was that marine engines don't use mufflers at all and muffle their exhaust into the water which is effective.

Pictured is the standard generator on about to begin experimenting with. I'd like some suggestions. Right now, I'm thinking of welding a 1" coupler into the hole of the stock muffler and using some high temperature hose to divert the exhaust into the bucket of water. Also pictured are however is the modification of a Kipor like mine with a Thrush muffler which is under $30. I might try putting the thrush in place as well as diverting into water. The water of course could be optional (again depending on where I'm dry camping and how quiet I want to be).

I really don't want anything bulkier than a glass pack because of it taking up more space when I stow in under the bay. Unless of course it can be easily removed as does the one pictured with two screws. If anyone has a different recommended muffler than a glass pack I'd like to hear suggestions please.

I realize I can't put too much back pressure on the engine but one of the things I like about experimenting on this with the cheaper generators is that if I push it and do create back pressure I haven't ruined anything too expensive. I need a run time of at least 10 hours and I'm running one roof A/C overnight. I have a 6,000 watt with electric start picked out to use next which has an 8 gallon tank that should give me the right power and run time but will use the generator pictured first for testing.

Ideas ?

 

[JakeMate]

Subscribed. Very interested in this. Been thinking about trying to quiet my 5000W Coleman down also. Was contemplating just adding a moto-cross exhaust or something. Haven't looked at it that closely yet.

 

[Hill Bill E.]

Subscribed.

Ditto! We have a 5000 and a 6500W at the cabin. Even though they are inside a 'shed', it would be nice to make them quieter.

 

[07 Elephant]

Nice. I've imagined a solution like that for a long time. Very cool to see someone implement it as well as he did. Super cool. Subscribed.

 

[foontoon]

Happy to see others are interested but nothing new suggested. The Thrush or glass pack muffler on the Kipor (that's from another thread I did not do that but am going to on my Kipor) is very inexpensive and a good muffler to try to use but the most simple, cheapest suggestion I read in researching was to divert the exhaust into a 5 gallon bucket of water. I've got to put a flange on the one pictured to make it work. But check your muffler. I've at the Oshkosh air show with 5,000 RV'ers and 41,000 others that also (some) have generators. All dry camping here. So I've been checking out a lot of generators. Many of them have a flange on the muffler easily allowing you to simply put a hose clamp and some high temp hose and divert it into the water to test. The tip was to poke a small hose in the top of the hose to prevent water from getting sucked back into the engine. ???? Don't know how that would happen but I'll poke a hole.

A good piece of quality scrap water hose might take the heat so you might not even have to make a trip to the parts store for the hose. Why don't some of you guys do that and report back ? It will at least 4 days before I can get to a muffler shop to weld a flange onto my muffler so I'd love to hear some test results before then. If that works (and the poster said he had done it), that is the magic /cheap fix for reducing noise on any generator.

 

[IdaSHO]

Dont forget about the intake.

Like most shop compressors, much of the noise comes from the intake, as well as the exhaust.

 

[SunTzuNephew]

Aside from muffling the engine, you can make the perceived noise quite a bit less by redirecting it upwards.

I have 4 3x4' pieces of plywood, which I set up in a rough box around portable generators. They're large enough that there is plenty of room for cooling air and exhaust, and extension cords. The plywood sheets (I use 1/2" thick exterior) are light enough to be easily handled.

The effect is to direct most of the noise upwards, instead of horizontally. This keeps the generator quiet enough that we can easily ignore it.

If you're re-mufflering the engine, a trick thats used in the movie business is to direct the exhaust straight up, as well. This is kind of what the plywood does....if the sound waves are going upward, the noise from the engine running is easier to deaden.

Good luck!

 

[skysix]

Friend at a cabin well off the grid in N. Alberta buried two 55 gallon drums (as an expansion chamber type of muffler) connected by 4" pipe, with a 3" pipe 20' tall painted like nearby trees as an exhaust. The generator was placed in a small shed built above it with 2"x8" insulated walls and roof and an air intake that came down from the "chimney" on the roof (4"x4" opening) Was designed to look like a mini house and other end (close to the cabin) was the yard tool storage (uninsulated).

When it was running you couldn't hear it from more than 50' away at night, and not at all from inside the cabin if the windows were closed. When open it was barely audible - a small fan was louder and the kids drowned it out 99% of the time just being kids.

 

[dependencies]

Has anyone ever achieved silent running with one this size?

 

[Tony LEE]

Assuming running the exhaust into water will make a lot of difference, which I doubt - 12 hours running is likely to evaporate a few gallons of water so the level will need to be automatically maintained. May need to augment storage capacity to cope.

 

[PhulesAU]

got any buddies with a muffler shop? look for a new truck/car take off. from somebody that wanted a cooler sounding noise maker. flex pipe to muffler and flex pipe output directed towards the SKY!!! I'd think one from a honda or subaru would be a perfect size.

 

[dzzz]

This thread is a pretty good argument for going out and buying a quiet honda or yamaha. Some of the cheapest generators have a design life of a couple hundred hours. Not something I'm going to build a custom enclosure around. Plus, I believe that non inverter generators don't idle down and produce electricity? There's a reason $300 generators are $300.
I did see a demo of a 6500W standby diesel generator in an enclosure that was real quiet. It had nice features too. It was $1500 and I'm sure from a Chinese company, but I don't remember the name.
One feature difference I found in customizing a gererator is where the controls are placed. I like the more model choices from Yamaha, but the controls are on the side. Honda is on the end.

 

[foontoon]

I just spend a week at the Oshkosh Air show which almost entirely dry camping. Ton's of generators. Here's a snap shot of a simple exhaust diverting upward which had little effect. I don't know what it sounded like before but it seemed like a normal loud generator.

The 2nd two with the enclosure worked GREAT ! The muffler is venting straight out the back, not through the battting. I didn't get to talk to the guy to figure out why he placed the batting where he did (help with intake noise ?). Seems like that would have restricted air flow but of all my research so far including riding my bike around hundreds of RV's and seeing what was tried, this set up here is the winner. One guy had a car muffler. Little difference also.

Having said all that I went out and bought a Honda 3,000 watt but I still have a contractor generator that I'll make that enclosure for.

 

[LuciferGuy]

Well, there're a few tricks that might help you silencing your Generator. Position your exhaust pipe vertically so that it directs the noise in that direction. Having a generator silencer will be a good idea. Placing a sound deflector between you( the spot where you want to achieve quietness) and the generator, a normal fence(or something that blocks sound) might do the job for you. Make sure you've tightened the loose parts and lubricated the bearings. Doing these will help you bringing down 10-15 decibels for you.
You can try to soundproof it, but it will be difficult to achieve much. Most of the noise is mechanical vibration rather than exhaust sounds, so you are trying to cover up very basic frequencies that penetrate most things quite well. As others have noted, you can't really seal it up because it will starve and/or overheat.
My profession includes a LOT of sound reduction devices. Without attenuation, the noise would be unbearable. The most common way we overcome that problem is with soundproof boxes which are nothing more than a diverted path for the air to flow and sound absorbing materials. Actually, they are the same principal of exhaust mufflers. So I know that I can greatly reduce the noise, I just was trying to avoid fabricating a prototype and employing a fan capable of moving a tremendous amount of air, then using a motor speed control to find the optimum CFM while maintaining proper temperature inside the enclosure. There are really two approaches to the enclosure. One would have the engine exhaust inside the enclosure, the other would provide separate attenuation for the engine exhaust. The best approach is to soundproof separately because mechanical sound vs engine exhaust sound is almost at opposite ends of the band. Plus, attenuating both in the same enclosure would then require either a fan motor capable of higher heat (much more expensive), a direct-drive fan (off the engine) which would be a pain to design and fabricate, or a extremely high-static fan that would pressurize the enclosure instead of [gently] drawing air through it. The high static fan approach would need a lot of sound attenuation and some creative ducting to ensure that engine/exhaust heat didn't affect the generator.

 

[dbhost]

I'm working with a MUCH smaller scale than you right now as my power needs are quite modest, and I am using a Harbor Freight Tailgator 700 / 900w 2 stroke generator. I have a baffle box of sorts built out of those foam interlocking floor cushions and I have the end panels left with a 1.5" slot, on one side on the top, on the other side on the bottom. This allows me to run my generator about 10' from a small pop up we use on the beach to run the tiny AC unit during the summer. Over the sounds of the constant sea breeze, and the crashing surf, we literally can't hear the generator, that little noisemaking 2 stroke chain saw engine and all...