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Old 08-31-2019, 09:20 AM   #1
Winnebago Camper
Join Date: Aug 2019
Location: Chesapeake City Md
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Quieting a generator

Looking for suggestions for quieting an onboard generator.
I am considering installing a resonator on the exhaust tailpipe but I am
concerned about voiding the warranty.

Any suggestions would be appreciated.
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Old 08-31-2019, 09:48 AM   #2
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More details would help. Make/model/year of the RV, make and model of the generator, etc
2014 Sunstar 31KE
1988 Suncruiser 31 RQ
1968 Travco 210
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Old 08-31-2019, 09:55 AM   #3
Winnebago Camper
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Quieting a generator.

My RV is a 2016 Winnebago Trend with an Onan/Cummings 2800 watt generator.
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Old 08-31-2019, 10:38 AM   #4
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Doesn't Onan/Cummins make a resonator for those units and similar?

Surely that wouldn't void your warranty?
2018 (2017 Sprinter Cab Chassis) Navion24V + 2016 JKU (sold @ ????)
2016 Sunstar 26HE, V10, 3V, 6 Speed (sold @ 4600 miles)
2002 Roadtrek C190P (sold @ 315,000kms)
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Old 08-31-2019, 10:55 AM   #5
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Quieting a generators

Onan does make a resonator for their generator. From what I have read, these
resonators donít really suppress the sound, they change the audio frequency
to one that is less annoying.

Was hoping to find an additional way to reduce the overall noise output.
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Old 08-31-2019, 03:32 PM   #6
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Onan makes a resonator for your genny. I installed one on our '10 Ventura class B years back. It will slightly reduce the sound level by knocking off the high frequency ringing in the exhaust note. I will be a little lower toned as a result.

One of the issues is transmission of vibration via the exhaust hanger to the body work. There is usually a long pipe suspended at the end near the side of the RV. The hangers are the cheapest thing the upfitter could find at Tractor Supply. Something your grand Pap would use to hang a muffler on his Ford N8 tractor. I modified mine. There's not much space and probably no other place to mount the hanger to the coach. So.... I removed the hard rubber (usually made from a cut up deuce and a half tire!!!) and replaced it with a short, medium weight spring using the saddle clamp on the pipe. That will allow it to bounce, dance and jiggle around without transmitting the vibration to the coach. (If you watch the genny while it is running, you will see it wobble around on the rubber mounts a bit. That movement is magnified at the end of the long pipe...)

Installed the resonator about 1/2 way between the elbow on the bottom on the genny and the spout. To make the install neater, I took it to a Lad at the local muffler shop and had him shorten the pipe and weld the resonator in place. Spout came out a tiny bit farther from the side of the RV.

If you 'Bologna' slice the tip of the exhaust about 30-45 degrees (rather than straight cut) it will also slightly reduce the exhaust note. (DON'T ask for the technical reasons....!!!!)

Another tip is to take a mat like you would use on porch steps and place it on the ground under the genny. One of those that is made from astro-turf with all the gnarly blades of 'grass' poking up. Put it gnarly side up. The genny creates vibration and sound when running and that energy is trapped under the RV. If you put and astro turf type mat under it it the energy will be dissipated in the plastic 'grass' and noise level reduced a bit more.
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Old 09-08-2019, 06:55 PM   #7
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I would have to say that "Old Crow" is MORE than Winnie Wise
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Old 09-08-2019, 08:04 PM   #8
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Posts: 156
2004 Onan 7500 Quiet Diesel Generator Not So Quiet Anymore!

Do you have any suggestions on how I can make my Onan 7500 Diesel Generator quieter? I have ~600 hrs on it and put on 75 hours in the last 2 months.

Last week I had a certified Onan shop change the belt and fluids (oil, coolant, thermostat, and temp sender). It cost $650.

I called the shop to report the following concerns:

* The generator ran quiet for about 5 minutes.. then it make a loud sound. Puffed smoke... and then I heard a vibration I was not familiar with. At first I thought the new belt might need time to "break-in", but I am told this is not the case. (The mechanic said he did remove the pulley to install the new belt.)

* When running at low RPM (low or no load) the generator would make a loud harmonic that now rumbles the RV floor.

Consequently, I definitely think it's sitting on or leaning again some steel supports and that's why I feel the vibration in the RV now. (New condition.)

* I called the shop and the mechanic said he pulled the generator out and off the front slide so he can work on it more easily. He said, I might have a "soft shoe" problem, but I'm not sure what he means?

* The mechanic said the engine-pop-noise and black smoke out the exhaust was the engine probably passing an air bubble since it he removed the fuel line. (Maybe so since I have not had any problems since.)

* And the "bang" I heard was the generator falling into place on the slide. However, the four mounting bolts are all very tight.

==> I think the problem is that my generator is not positioned correctly on whatever spring mounted system I have. What do you think?

I am presently 800 miles away from the shop who did the work and I may not be returning to Huston until next year; so I am contemplating taking it to another Onan service facility. ...And if I do, I want to be prepared.

So can you help me by giving me some feedback and/or suggestions on how I can quiet my generator?

==> From under the generator it looks like one of the spring generator mounts are not seated right. Is this what the tech means by having a "soft foot" problem? Is my generator only resting on 3 of the 4 generator mounts and that's why it vibrates... more when at low RPM?

==> If another shop is going to take the generator out, can I do anything to "beef-up" the spring supports or replace the springs? Will this make it vibrate less?

==> I can't find any leaks in the exhaust system, and my spark arrestor (removable bolt) is clean.

==> Do they make an "resonator" for my Onan 7500 that I can add to the straight exhaust pipe? (My pipe is straight but I may look at adding a bend to it. Good suggestion!)
2004 Itasca Horizon ISK-40AD, 350HP Cummins 8.3L
75K miles and the best of 3 Diesels I have owned thus far!
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Old 09-09-2019, 04:29 AM   #9
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Unfortunately the QG2800 has a single cylinder engine that spins at 3,600 rpm like a lawn mower running at full throttle so its going to be difficult to do much more than alter a bit of the tone of the exhaust by using a resonator.

To get past the frequency you really need a generator with an engine that spins at 2,800 rpm or slower.

Most items you can add to make the exhaust quieter can also reduce efficiency and make them run hotter.

Some find adding a Genturi Exhaust stack or a simple rubber exhaust hose like they use at a service station to vent exhaust gases further away from the work area can help. Some put the exhaust hose in a simple bucket of water however you have to keep refilling the bucket. Others find that once they quiet the exhaust that the mechanical noise from the generator becomes more apparent and bothersome.

The QG2800 is rated at 70 decibels under half its rated load capacity at 10 feet which is about the same as a running a shower or a standard dishwasher. If its louder than that you may have other issues such as exhaust tube binding, isolation spring, bushings set too tight or other modifications by a prior owner transferring more noise inside the coach.

To mitigate noise inside the coach some find insulating the generator compartment (not the generators housing/cabinet) with Dynamat or some other engine compartment sound deadener.
Neil V
2001 Winnebago Adventurer WFG35U
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Old 09-09-2019, 11:32 AM   #10
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When (or if) Honda decides to jump into the RV generator market, Onan will be a distant memory...
2014 Itasca 27n
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Old 09-09-2019, 10:25 PM   #11
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Join Date: Oct 2015
Posts: 10
generator noisy

Originally Posted by JCostick View Post
Looking for suggestions for quieting an onboard generator.
I am considering installing a resonator on the exhaust tailpipe but I am
concerned about voiding the warranty.

Any suggestions would be appreciated.
Hi, The noisiest part of your genset isn't the exhaust. It's all the bits and bobs around it that vibrate and rattle and resonate mostly unsympathetically. No one has yet, to the best of my knowledge, come up with a viable and low cost DIY solution!

Just do as I did; one additional, already have two, 12 volt deep cycle batteries and 300 watts of Uncle wiener's hundred dollar solar panels, including cables, controller, connectors etc etc less than five hundred northern pesos!! That's about ...what? Six bits US??

With average summer sun in AB that's enough free electrons for my lighting, two go-cups of coffee, and 1 Liter of morning of tea. Coffee maker, B&D, is 16 oz one cup, 650 watts, 3 min brew time and kettle is one liter, 1200 watt Walmart item that boils in less than 4 mins. Daily watts in considerably exceed daily watts out even on a dull day! Never a big fan of solar but this works for me. Plus I no longer worry about my cranky 5.5 Kw Onan POS!!

Tailwinds and down grades.
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