rdickinson Posted November 21, 2015 Report Share Posted November 21, 2015 Earlier this year I asked about noise abatement for my 7kw Diesel Multiquip generator. The unit cost about 7k 9 yrs ago so it owes me nothing, however the crash in '09 crunched the enclosure and Multiquip didn't respond to my enquiries about replacement parts.....Moving on, after 22 months we fired it up out of its shroud and it ran like a top but it is a noisy sucker at 85 db's. It was initially installed under the passengers side, fwd of the fuel tank but that location proved to be a problem for any type of enclosure and leaving access for service so out it came and has been relocated. With the new location and a number of sound deadening techniques the Generator noise is pretty much gone. What needs a bit of attention is the exhaust noise. The stock muffler is installed with the tailpipe aimed towards the rear of the truck b/w the frame rails. The gameplan is to go with a slightly larger diameter pipe coming off the backend of the muffler, do some changes of direction and add another muffler or resonator. Something like a gun silencer or ?? We may even bring the direction forward then down. Air will change direction but noise isn't happy doing the same and is reduced every time it is deflected in a different direction. Spending a pile of money on a 7.5 kw Onan was not in the cards. We've switched around a couple of circuits on the breaker panel so 6k useable is more than enough for the amount it will get used. The Inverter can be switched off while the micro and coffee pot are being use. The electric/ gas hw heater can be heated with blowpane. Fridge draw is minimal. So the question is what muffler would be best suited for this application. It needs to be something readily available off the shelf. Thanks BTW does anyone know of a decent, accurate db meter app I can download? Link to comment Share on other sites More sharing options...
jkoenig24 Posted November 21, 2015 Report Share Posted November 21, 2015 Have you ever consulted a good muffler shop (one that can fabricate)? Link to comment Share on other sites More sharing options...
rdickinson Posted November 21, 2015 Author Report Share Posted November 21, 2015 That was the first thing I did but that didn't work out as the size of the pipe is different and it fell into the PITA category. Several were tried. Besides, these firms did cars and had nowhere to park the 730. All I need is the muffler everything else can be handled. Link to comment Share on other sites More sharing options...
wildmandmc Posted November 21, 2015 Report Share Posted November 21, 2015 https://play.google.com/store/apps/details?id=kr.sira.sound&hl=en db meter app. for android. Link to comment Share on other sites More sharing options...
adept99 Posted November 21, 2015 Report Share Posted November 21, 2015 Try a mower or ATV / UTV shop - might need to fab up an adapter for a proper fit, but the new units are generally pretty quiet. Link to comment Share on other sites More sharing options...
lappir Posted November 21, 2015 Report Share Posted November 21, 2015 If memory serves me correctly, lots of lawn mowers and other small 4 cycle engines used threaded galvanized pipe for exhaust and the mufflers would just screw onto the pipe. You could do pretty much anything with the various elbows , connectors and cutting pipe to length. Link to comment Share on other sites More sharing options...
NoDirectionHome Posted November 21, 2015 Report Share Posted November 21, 2015 Roger Plato power equipment in Plato TX have been my go-to guys for stuff like this. Very helpful and re$onable. Link to comment Share on other sites More sharing options...
noteven Posted November 21, 2015 Report Share Posted November 21, 2015 https://www.youtube.com/watch?v=DzMZJBapbh4 Briggs & Stratton complete with No muffler, stock muffler, Supertrapp muffler Link to comment Share on other sites More sharing options...
rdickinson Posted November 21, 2015 Author Report Share Posted November 21, 2015 I need to go up in size, lawnmower won't do that. I'll get measurements of existing tailpipe size and call Plato in Texas. Were pretty close to solving the problem. I tried a couple of these apps, one registered 90 db when speaking normally. There are more to try. Thanks to both. Link to comment Share on other sites More sharing options...
Star Dreamer Posted November 21, 2015 Report Share Posted November 21, 2015 Try a place that handles commercial mowers like for golf courses, you will be surprised how big the engines are. You can get a Cummins 99HP Diesel in one of the larger rough mowers. https://www.toro.com/en/golf/rough-mowers If you want, I might be able to get more specific information from my son who is a test engineer with a mower company. Send me a PM. Dave Link to comment Share on other sites More sharing options...
rdickinson Posted November 21, 2015 Author Report Share Posted November 21, 2015 working on it now Link to comment Share on other sites More sharing options...
Star Dreamer Posted November 21, 2015 Report Share Posted November 21, 2015 You could try what this guy did and get a muffler from a motorcycle. Not sure if there is a difference between gas and diesel mufflers though. http://joelsgarage.blogspot.com/2006/03/quiet-generator-muffler.html Link to comment Share on other sites More sharing options...
rickeieio Posted November 21, 2015 Report Share Posted November 21, 2015 There's more to a muffler than just air flow. Baffling needs to be designed to quiet individual cylinders, thus the design for 20 c.i. cylinder would be roughly the same no matter the number of said cylinders. Of course this doesn't take into account CFM of additional cylinders and rpm.................. So, a trip to your friendly auto recycler might yield a muffler from a small car that could be adapted with a piece of flex pipe for acceptable results. Link to comment Share on other sites More sharing options...
Toyhauler Posted November 21, 2015 Report Share Posted November 21, 2015 I had good luck shopping at Tractor Supply for a good size muffler for one of my generators. Link to comment Share on other sites More sharing options...
Pat & Pete Posted November 22, 2015 Report Share Posted November 22, 2015 There's more to a muffler than just air flow. Baffling needs to be designed to quiet individual cylinders, thus the design for 20 c.i. cylinder would be roughly the same no matter the number of said cylinders. Of course this doesn't take into account CFM of additional cylinders and rpm.................. So, a trip to your friendly auto recycler might yield a muffler from a small car that could be adapted with a piece of flex pipe for acceptable results. In all my years of cobbling exhaust systems , I've never had good luck using flex pipe . It's good for very short term or temporary use . Much more and it will have to be replaced due to rust holes . It seems to be too thin to hold up for very long . Just my experience . Link to comment Share on other sites More sharing options...
rickeieio Posted November 22, 2015 Report Share Posted November 22, 2015 In all my years of cobbling exhaust systems , I've never had good luck using flex pipe . It's good for very short term or temporary use . Much more and it will have to be replaced due to rust holes . It seems to be too thin to hold up for very long . Just my experience . Both of our trucks, a Mack and a Volvo, have factory flex pipe, but in stainless. Yes, it will eventually fail, but it solves a lot of problems. Your motor moves, and the exhaust may too, in a different direction at times......... Link to comment Share on other sites More sharing options...
rdickinson Posted November 22, 2015 Author Report Share Posted November 22, 2015 There's more to a muffler than just air flow. Baffling needs to be designed to quiet individual cylinders, thus the design for 20 c.i. cylinder would be roughly the same no matter the number of said cylinders. Of course this doesn't take into account CFM of additional cylinders and rpm.................. So, a trip to your friendly auto recycler might yield a muffler from a small car that could be adapted with a piece of flex pipe for acceptable results. Yeah, I know its complicated, several have told me it would be a waste of time but it has worked after all. We've double layered insulation, staggered and offset intake and exhaust air, made a doghouse plus some other creative ideas. The info and links have been sent to Chris and we will experiment, cast iron, welded joints, directional changes as well as mufflers. The noise level is OK as it is but will be reduced even more when we complete later this week. Link to comment Share on other sites More sharing options...
Pat & Pete Posted November 22, 2015 Report Share Posted November 22, 2015 Both of our trucks, a Mack and a Volvo, have factory flex pipe, but in stainless. Yes, it will eventually fail, but it solves a lot of problems. Your motor moves, and the exhaust may too, in a different direction at times......... Factory ... I'm sure that pipe is much more , in all ways , than the pipe I could buy retail . Link to comment Share on other sites More sharing options...
rickeieio Posted November 22, 2015 Report Share Posted November 22, 2015 Factory ... I'm sure that pipe is much more , in all ways , than the pipe I could buy retail . I don't know if the stuff I bought over the counter was different than factory. I replaced the pipe on the Mack about 5 years ago, and it's still okay. That truck gets run a fair bit in the fall, but it's all very short trips, often less than 1 mile. Then the rest of the year it gets perhaps 4x25 mile trips a day, then will sit for 2 months. Likely worse for it than what our toters see. My point was, that a short section of the flex will isolate the muffler, which will likely be solid mounted, from the engine, which on my generators, is rubber mounted. Link to comment Share on other sites More sharing options...
Pat & Pete Posted November 22, 2015 Report Share Posted November 22, 2015 I don't know if the stuff I bought over the counter was different than factory. I replaced the pipe on the Mack about 5 years ago, and it's still okay. That truck gets run a fair bit in the fall, but it's all very short trips, often less than 1 mile. Then the rest of the year it gets perhaps 4x25 mile trips a day, then will sit for 2 months. Likely worse for it than what our toters see. My point was, that a short section of the flex will isolate the muffler, which will likely be solid mounted, from the engine, which on my generators, is rubber mounted. I see what you're saying . I have to think that what you bought 5 years ago has to have been more robust than any I've ever bought , as I've never had any flex pipe that lasted near that long while in use . Link to comment Share on other sites More sharing options...
rdickinson Posted November 22, 2015 Author Report Share Posted November 22, 2015 https://www.youtube.com/watch?v=DzMZJBapbh4 Briggs & Stratton complete with No muffler, stock muffler, Supertrapp muffler I'm curious how much difference this system would make once you get down to below 70 db's. Link to comment Share on other sites More sharing options...
noteven Posted November 22, 2015 Report Share Posted November 22, 2015 I'm curious how much difference this system would make once you get down to below 70 db's. I'm not sure Roger but if you contacted Supertrapp they would likely have an idea. It is compact. Link to comment Share on other sites More sharing options...
NoDirectionHome Posted November 22, 2015 Report Share Posted November 22, 2015 Technically 3dB = double the sound energy. Actual perception is that 10 dB = a doubling or the volume for most people Link to comment Share on other sites More sharing options...
rdickinson Posted November 23, 2015 Author Report Share Posted November 23, 2015 I need to measure the current db level within 3 ft of the truck to give me a point to work from. I'll make some calls in the am. This week should do it. Link to comment Share on other sites More sharing options...
Jack Mayer Posted November 23, 2015 Report Share Posted November 23, 2015 Roger I use a dbmeter on my android phone. I'm not sure how accurate it is, but from a relative perspective it seems to work OK. Just FYI my truck, under way on a level road is 75-76 db with the phone held near my ear. It is noticeably quieter in ecoroll coasting down a hill, but the db is about the same, interestingly. I have the D16 and it does sound different than a D13....I don't know if it is noisier though. In any case, the truck seems fairly quiet - we can certainly talk in normal voice in the truck. Link to comment Share on other sites More sharing options...
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