I recently tested our new gas powered 4kw generator. It naturally runs flat-out and makes enought noise to wake the dead. How do you muffle one of these Briggs & Straton beasts? Will trying to muffle this mess-up the efficiency of the engine (backpressure considerations)?

Related question: Is their a way to run these on something other than gasoline? How? (propane, "home-made gas", etc?)

Thanks!

-- Brett Blatchley (bblatchl@inmar-inc.com), March 26, 1999

Answers

My husband put a muffler system on our generator.Also it is sitting on an enclosed platform a few feet off the ground.The box has metal siding with lots of 1" (approx) holes drilled all over for ventilation so it doesn't run too hot.Anyone walking around the house would think it is a container to hold garbage cans.It purrs....can't hear it inside & not very loud outside either.

-- Carol Ann (JCclass69@aol.com), March 26, 1999.

Thanks for the question. May I add one to it? I checked into having our Generac 6200 converted to propane because propane would be easier and safer to store. The places I checked with would only convert Hondas and they wanted between $500 and $700 to do it for a 5000 watt). That is more than we paid for the generator. I haven't found anyone who could convert it to deisel (also safer to store, but around here deisel is more expensive than gas which I don't understand either - oh well). Would be interested to know if anyone knows if/how this could be done -to deisel that is. Thanks.

-- Valkyrie (anon@please.net), March 26, 1999.

Here is how to quiet them.

-- BB (peace2u@bellatlantic.net), March 26, 1999.

Poor Man's Generator Noise Reduction

We all want a quiet genset, right? Here are the details of what I did to quiet down my small genset.

A small gas engine makes a lot of noise. I have read that the better engines such as Honda are inherently more quiet than cheaper ones. My engine is a cheap one and therefore the results are more significant. I have a 1000 watt generator powered by a used 3 1/2 HP Briggs & Stratton engine which just screams at full load.

First of all there are two distinct noises that an engine produces; exhaust noise and engine mechanical noise. Before I began this project, I thought that exhaust noise would be the greater of the two, now I am not so sure.

To reduce the exhaust noise I went to my local lawnmower repair facility. I highly recommend finding the one in your area and spending a little time getting to know the folks there. They are very helpful and there are always "jewels" to find out there in their graveyard. I talked to them about muffler options and quickly found that there are no "general" stock items for such an application. I did use the yellow pages and called a few generator places, including Honda, and found there are some new spark arrester mufflers, like the type used on Generac 4000 and 5500 XL's. These mufflers "promise" to be quiet but at a hefty price $85 plus. I have not heard anything operating with these type of mufflers, so I don't know how effective they are at noise reduction. If any of you have a genset with one of these then please share your experience.

Out in the lawnmower junkyard, I got a 100 cc moped muffler and mounting bracket for $6. A quick trip to Home Depot, some 1/2 inch galvanized pipe and fittings and, presto - a great super-low tone muffler.

Now that I got the exhaust noise greatly reduced, it was time to deal with the engine's mechanical noise. I got some free scrap 3/8" plywood from a construction site (amasing what they will let you have for free if you just ask). I built a 5 sided box shroud, 4 sides and a top, and lined the inside with fiberglass (also free from scrap).

I know what some of you are thinking, what about ventilation for the heat? This shroud sits over the engine portion of my verticle shaft genset, in such a way that allows plenty of room for the engine's forced air paths to exit. Most of the forced air is directed at the exhaust port and cylinder head. The top of the shroud has a 6" circular opening to draw cool air right into the engine's cooling fan.

I ran my genset for 5 hours under load and noticed it seemed to be no hotter than without the shroud. I am not saying it was not ANY hotter, just that I could tell no difference. The noise reduction, however is terrific! Before making the wooden shroud, I used a large cardboard box as a prototype. The wooden box was amasingly better, due to the fiberglass insulation no doubt.

With the engine's mechanical noise dramatically reduced, I found that the moped muffler I used was emitting more noise that I wanted. You know how a project can get once you get really into it. I went to my local auto parts store and bought the cheapest car muffler they had for $25. I installed the car muffler and WOW, one quiet genset! If there is ANY exhaust noise, I would need NASA scientists to come by with sensing equipment to show me, my ears hear none at all.

For comparative purposes; The Generac 4000XL's noise specs are 86 dB at 3 1/2 ft 73 dB at 23 1/2 ft

My Generator's noise specs are 88 dB at 3 1/2 ft 75 dB at 23 1/2 ft 70 dB at 33 ft

I was pleased to get such close sound specs to a new Generac. I think that if I started with a new engine the specs would be a little better. This engine burns 1/2 quart per 15 hours of use, so obviously there is some serious wear that's already taken place during its life.

The end result is for a $ 35-40 investment, both mufflers (who knew) the galvanized fittings and all, and a few hours of labor I ended up with an very quiet genset. I wish now that I had also taken dB readings before starting this project. I can tell you, it was a LOT louder. I think I'll bring it all down and show the guys at the lawnmower repair shop, they'll get a kick out of it.

If anyone has any suggestions or comments I would appreciate them. We're all here to learn from each other and to share what we find. I hope the information I have presented here helps another Y2K'r out.

-- Buffalo Bob (buff@halliburton.com), January 11, 1999

Contribute an answer to "Poor Man's Generator Noise Reduction"

-- BB (peace2u@bellatlantic.net), March 26, 1999.

Thank you all! This is wonderful.

I have read somewhere (but didn't pay attention at the time) that there is a way to make a "gasoline substitue" which was employed during the depression. I can't seem to recall where I read this. Anyone know about this?

-- Brett Blatchley (bblatchl@inmar-inc.com), March 26, 1999.

Converting from gas to deisel is impossible, the technology is COMPLETELY different after you describe them as internal combustion.

There are carb shops on the web that have propane conversion kits. Try using www.hotbot.com as the search engin with deisel conversion kits as teh search arg.

Chuck

-- Chuck, a night driver (reinzoo@en.com), March 26, 1999.

Thanks, BB, for posting my article "Poor Man's Generator Noise Reduction". I was going to look for it, you saved me the trouble. By the way, I am working on quieting my General 4000XL also. I'll post those results also...

-- Buffalo Bob (buff@hal.com), March 26, 1999.

Your Honda dealer should be able to get a propane conversion kit for you for under $300.00. You can do the conversion yourself as it isn't too hard. Dealers are prohibited from doing the conversions because of EPA regs. You can always bring it back to the dealer to check the conversion. Also, Carburation Supply in Dallas, Tx. makes converion kits. Call them at 1-800-433-2272. Good luck

-- sal estrada (dedorojo@primernet.com), March 26, 1999.

I wanted to convert a Honda gas motor to propane, but was disuaded because apparently they don't hold up very long.

I eventually purchased an Onan Generator and used its factory conversion because it's designed for the task.

As for muffling, it's easy - go to Sears or whatever and buy a car muffler (any cheap one will do). Get an adapter pipe made if sizes are different, and attach it like a car muffler. It reduces sound quite a bit.

Another thing we're doing is routing the muffler pipe through our greenhouse to help warm it in winter.

Jolly

-- Jollyprez (jolly@prez.com), March 26, 1999.

Drop a 4000 pound weight on it from 20 feet. Works every time. The generator also saves on gas after that. Also, as per previous post, 4000 pound weight can be used as defensive weapon against intruders.

-- Craig (craig@ccinet.ab.ca), March 26, 1999.

for propane conversion kits try us carberation http://www.uscarb.qpg.com/ Their kits are quite inexpensive bought one for my 10 hp generac for around 150 plus shipping. Haven't installed it yet but looks fairly easy. Remember that most conversion to propane are quite permanent, voids warranty on generator. Some hints for planning your installation the supply for the generator must be between the regulator at your propane tank and the regulator at the house. Good luck

-- Papa Bear (it.guy@usa.net), March 27, 1999.

Reducing mechanical noise:

If you have a used four stroke engine, have the valves adjusted. They get loose over time (even though the engine will still run ok) and this creates a large part of the "clatter". Also check the cam chain tensioner if it has one.

Also make sure the motor mounting bolts are tight.

-- the lone rider of the apocalypse (y2kbiker@bellatlantic.net), March 27, 1999.

Buffalo Bob,

I tried to e-mail you, but no go.

I'm very interested in this subject and your answer to Brett's question. Please note my post from last weekend "BACKUP POWER. A FINAL CHOICE FOR ONE FAMILY" - in case you haven't seen it.

I would like to get specific about exhaust piping sizes, flanges, etc.

My Honda V-Twin 16 HP engine has a 1 1/16" OD exhaust pipe that is coupled by clamp to the stock muffler. The stock muffler itself also has a short exhaust pipe of 1 1/8" OD, very short. The stock muffler could be removed and a new muffler (auto, etc.) attached in its place using an appropriate sized 1 1/8" ID reducer pipe clamped on, or brazed on, the new muffler. An alternative, would be to use the four mounting holes on the existing stock muffler to attach a second muffler. This could be done using a flange with gasket that could bolt to the stock muffler. This seems unnecessary over-kill in light of the good sound reduction you have experienced.

What dimensions are you working with? Did you use a flange of any sort? I'm also very interested in the enclosure you built, but will hold most of my questions and comments for now. Suffice it to say, heat dissipation is a real big issue with this NorthStar unit I have. It gets pretty hot and needs lots of fresh air.

Keep the faith!

Bob Walton

-- Bob Walton (bwalton@kdsi.net), March 28, 1999.

My current e-mail address is as below.

-- Bob Walton (waltonb@kdsi.net), March 28, 1999.

For all you folks interested in generators powered by Honda propane-fueled engines. I've found only one generator manufacturer that provides generators using the new Honda multi-fuel (propane/gasoline) engines. Here's their URL: http://www.wojo.com/dacg/gohonda/index.html Note: They have a very short deadline remaining for units to be delivered before the end of the year. Check the website for the latest cutoff date.

-- Norm Harrold (nharrold@tymewyse.com), May 11, 1999.

I believe that the WWI gas reference you remember may have been to an article in Mother Earth. The reference didn't give a citation. There are several links on the web to biogas. http://www.veggievan.org/ http://gate.gtz.de/isat/default.asp?dis=/biogas/toc.html&tit=AT%20Info rmation%20-%20Biogas%20Digest%3A%20Index&nav=1 I downloaded a really good "how to" archive from Point Mudge BBS, but John has moved and I don't have a working new link.

I read somewhere that someone exhausted his generator into an underground barrell with a vent.

-- marsh (armstrng@sisqtel.net), May 12, 1999.

how long does propane store? Hopefully longer than the 3month gasoline limit. karen

-- karen (karen@karen.karen), May 12, 1999.

I even went to www.propanegas.com but found no info on the "shelf life" of propane. Any stats? karen

-- karen (karen@karen.karen), May 12, 1999.

Karen

Propane should last a year or two in my experiance and more than likely longer

Good luck!

-- Brian (imager@home.com), May 12, 1999.

Thanks Brian, that's great news! karen

-- karen (karen@karen.karen), May 12, 1999.

Karen,

Propane will last essentially "forever". All you really have to worry about is losing it (leaks in the tank, rusting tanks, etc.). I recently "discovered" that a small propane tank that had been lurking in my barn for over ten years was FULL, and when I used it, it was as good as ever.

-- Hardliner (searcher@internet.com), May 12, 1999.