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Old 10-08-2013, 09:43 PM   #15
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I can finally report back on my solution for what I consider to be noisy generator exhaust. I ordered the cummins resonator and I also ordered the 5S Super trapp muffler with 6" resonator from Jacks small engine, I tried both and the Super trapp was the winner hands down, there is almost no exhaust noise just the noise of the engine itself. I'm attaching a picture. I intend to add a hanger at the muffler attach point and omit the original factory hanger.
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Old 10-09-2013, 01:38 AM   #16
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I can finally report back on my solution for what I consider to be noisy generator exhaust. I ordered the cummins resonator and I also ordered the 5S Super trapp muffler with 6" resonator from Jacks small engine, I tried both and the Super trapp was the winner hands down, there is almost no exhaust noise just the noise of the engine itself. I'm attaching a picture. I intend to add a hanger at the muffler attach point and omit the original factory hanger.
Very nice Jeff! Did you get a chance to test the output of the generator yet? Does it still output enough power to run the roof air? TIA
David
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Old 10-09-2013, 02:52 AM   #17
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Lightbulb

I had my auto muffler guy re-do the system on my SOB Onan generator. By adding some curves and length, we came up with a setup that used a small car muffler, and moved the exhaust point to the rear; all while still allowing the pull-out generator tray to work normally.

The small car muffler did a superior job of quieting the exhaust, with so much more flow capacity that back pressure was a non issue. I discovered that the exhaust is only ONE of the noise factors from the generator. Shrouds, sagged mounts, and the sound of the engine itself make a dissonant symphony, but muffling the exhaust goes a long way at a campsite.

A resonator is basically a canister with some manner of simple baffles or chambers, but no damping material. It reduces the amplitude of the exhaust pulses, but in peaks and valleys across the frequency scale.

OTOH, a muffler includes sound damping material like fiberglass packing. It does a superior job of damping the sound waves across the scale. It also has a more complex flow pattern than a resonator, with perforated pipes carrying the flow forward and back, from chamber to chamber. The sound damping is far better, but this introduces more back pressure into the system.

Finally, a glasspack muffler is a perforated or riffled tube going straight through, with fiberglass between the perforated tube and outer shell. These don't muffle well, and riffle designs introduce some backpressure through turbulence; these are mainly used on performance cars. However, they have a place in motorhome systems; on the engine exhaust, small glasspacks added near the end can help reduce the strange resonances from the looong pipes. Also, a glasspack might be a good supplement or endpiece in a longer generator system, but not as the only muffler. There are many "exhaust tips" on the market that amount to a small glasspack and may be worth looking at.

One thought about using a car muffler; having a 1-1/2" generator exhaust pipe enter a 2"+ muffler inlet is good. You may find that the sound damping is better with the outlet reduced again to a 1-1/2 or 1-3/4" tailpipe instead of 2" or whatever size the muffler outlet is. If size is no object, this will give quieter results than hunting up a generator-size muffler.

My 25c on generator exhaust mods.
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Old 10-09-2013, 06:32 AM   #18
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ordered the 5S Super trapp muffler with 6" resonator from Jacks small engine
Thanks for finding a great option for us! I just went to the website but there seem to be lots of variations. Can you provide the part numbers you ordered?

Thanks again!
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Old 10-09-2013, 07:05 AM   #19
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Are there not warranty issues with CumminsOnan as far as using a non factory muffler? Used to be. Jim
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Old 10-09-2013, 09:17 AM   #20
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Thanks for finding a great option for us! I just went to the website but there seem to be lots of variations. Can you provide the part numbers you ordered?

Thanks again!
The expansion of the hot exhaust gas, is the noise maker.

Cooling off the exhaust, greatly reduces the noise.

Simply adding a longer tail pipe of what ever length, and you will be amazed at the reduction of decibels.

Andy
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Old 10-09-2013, 05:58 PM   #21
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Thanks for finding a great option for us! I just went to the website but there seem to be lots of variations. Can you provide the part numbers you ordered?

Thanks again!
I ordered the clamp on 1 1/2" diameter 5S muffler part # 5S1500H it will come with 3 diffuser rings, you only need one so you don't need to order those. I also ordered the 6" resonator part # 5S5536 It fits together very easily and will slide tightly over the exhisting pipe which you will need to shorten some and comes with a clamp.

I have used the generator and air a little with no problems, if back pressure becomes a problem with this type mufffler one could add another diffuser ring, however this muffler is rated for a much higher horse power engine than the generator . I know there are those who have concerns regarding the warranty, I suppose you could loosen the two nuts and slip it off before service. Personally I am not concerned about it, to me it was annoying enough that I wouldn't use the generator and now I am much happier with it.
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Old 10-09-2013, 06:22 PM   #22
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Let us know how the air conditioner works on a 95 degree plus day when the current draw is at maximum for the generator.
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Old 10-09-2013, 08:03 PM   #23
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Supertrapp Brochure

This Supertrapp muffler looks like the perfect solution to exhaust noise. It's another product made in Ohio and I've attached a copy of the brochure. It is available from many sources.
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Old 10-11-2013, 06:26 PM   #24
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Suppertrapp muffler

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Originally Posted by Jeff64 View Post
I ordered the clamp on 1 1/2" diameter 5S muffler part # 5S1500H it will come with 3 diffuser rings, you only need one so you don't need to order those. I also ordered the 6" resonator part # 5S5536 It fits together very easily and will slide tightly over the exhisting pipe which you will need to shorten some and comes with a clamp.

I have used the generator and air a little with no problems, if back pressure becomes a problem with this type mufffler one could add another diffuser ring, however this muffler is rated for a much higher horse power engine than the generator . I know there are those who have concerns regarding the warranty, I suppose you could loosen the two nuts and slip it off before service. Personally I am not concerned about it, to me it was annoying enough that I wouldn't use the generator and now I am much happier with it.

Hello,
I've done the same as you except used onan resonator with suppertrapp. However,the tech at suppertrapp recommended 2 diffuser plates. I did not measure noise level but it seems to lower noise level and takes out the lawn over sound. Now you get hear how noisy the generator can be. I'm going to insulate the top and call it quieter. Pleasureway does a nice job of building brackets to mount onan but seems it would be difficult to add vibration eliminator s at mounting pts. Overall glad I made changes. The car muffler is author good option
Pete
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Old 10-11-2013, 07:31 PM   #25
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Hello,
I've done the same as you except used onan resonator with suppertrapp. However,the tech at suppertrapp recommended 2 diffuser plates. I did not measure noise level but it seems to lower noise level and takes out the lawn over sound. Now you get hear how noisy the generator can be. I'm going to insulate the top and call it quieter. Pleasureway does a nice job of building brackets to mount onan but seems it would be difficult to add vibration eliminator s at mounting pts. Overall glad I made changes. The car muffler is author good option
Pete
Yes you are correct these things arent quiet even with little or no exhaust noise, I think the liquid cooled generators are much quieter. It's interesting that they told you to use two diffusers, that is determined by the horse power. Can anyone tell me how many horse power these generators are?

Jeff
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Old 10-11-2013, 08:52 PM   #26
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Generator Engine Specs

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Yes you are correct these things arent quiet even with little or no exhaust noise, I think the liquid cooled generators are much quieter. It's interesting that they told you to use two diffusers, that is determined by the horse power. Can anyone tell me how many horse power these generators are?

Jeff
From the Cummins Onan Spec Sheet:
Engine details
Model: EX 21
Design: 4-cycle, single cylinder, OHC
Displacement: 13.2 in3 (217 cm3)
Compression ratio: 8.5:1
Power: 7.0 bhp (max) at 3600 r/min
Cooling: Pressurized air
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Old 10-12-2013, 03:33 PM   #27
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I ordered the clamp on 1 1/2" diameter 5S muffler part # 5S1500H it will come with 3 diffuser rings, you only need one so you don't need to order those. I also ordered the 6" resonator part # 5S5536 It fits together very easily and will slide tightly over the exhisting pipe which you will need to shorten some and comes with a clamp.
Jeff, I am curious why you opted for the 5S5100 instead of the smaller diameter 3S5100? With the smaller diameter 3S you would, of course, have to use a couple of additional diffuser rings but the smaller diameter would appear to be a better fit. Certainly given the generator exhaust location in my 2013 Interstate. Would you anticipate a significant difference in sound attenuation between the two?
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Old 10-13-2013, 12:36 AM   #28
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Jeff, I am curious why you opted for the 5S5100 instead of the smaller diameter 3S5100? With the smaller diameter 3S you would, of course, have to use a couple of additional diffuser rings but the smaller diameter would appear to be a better fit. Certainly given the generator exhaust location in my 2013 Interstate. Would you anticipate a significant difference in sound attenuation between the two?
I noticed on the website that they said the 5s was the most quiet, that was the only reason for choosing it.
I agree the 3s would be a better fit and may not require a hanger support. I'm not sure if or what size resonator you can get with the 3s but the website makes it clear that you must use the resonator to achieve the best results for sound control.
I noticed another member used a cummins resonator and a super trapp muffler and I assume with the resonator on the super trapp as well. That could be a good option with the 3s. I was a little concerned with the size of the 5s when I got it but all said and done it fits quite nicely, it has no clearance issues and it is not visible unless you are on your hands and knees.
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