Generator Noise

[TQUIN45]

Generator Noise

In the past several months I have had to take interest in Generator noise. Back in Aug my wife and I traveled from Mass. to the West coast and did a bunch of National parks. We were asked to shut down our generator because it was too noisy. Our generator is a Cummins Onan RV QD 3200 Diesel. It's output is 3200 watts. Winnebago uses these in their VIEW model. The Cummins noise specification is the noise will be less than 68 dBA at 10 ft and 1/2 load. I have measured (with sound power meter) the noise at 78 dBA which is 10X louder than spec. I spoke to other RV Views owners and theirs are also very noisy. At this point Winnebago will do nothing to help but Cummins has shown interest in helping. The other issue for people to be aware of the location of the generator exhaust- just behind the rear wheel directly under the awning and below the rear bedroom window. Being under the awning goes against all of Winnebago's safety notes- again they will not help by changing the location possibly out the rear of the coach. If anyone has any questions please ask. Note- Honda and Yamaha generators are usually below 58 dBA noise- worth noting if possibly going to purchase one. In my previous RV- a Winnebago Vectra our 8000 watt diesel generator was much quiter than the QD 3200 watt. At 10 ft you could barely hear it. From my experience up to this point be careful if you buy a Winnebago View with a Cummins Diesel generator. The big issue is Winnebago will not step up to the plate and try to resolve the problems of noise and location from the generator.

[pnichols]

Here's a couple of older links from these forums talking about RV built-in generator noise and related issues/topics:

http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/22701484/gotomsg/22702544.cfm#22702544

http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/21167406/gotomsg/21226680.cfm#21226680

[Handbasket]

hotbyte wrote:

ron.dittmer wrote:
I've been thinking of carrying a 1/2" thick 4x6 piece of carpet foam just to throw under the motor home, under the generator so the noise doesn't bounce around and rattle throughout the campground.

Interesting idea...

The idea has been around for a while, and has some merit. On the small gas & LP Onans, most of the cooling air exits down thru the hole around the exhaust pipe in the bottom. It carries a lot of mechanical noise with it. I suspect parking on grass has a similar effect, but the carpet or carpet pad should absorb some noise before it's reflected back from a hard surface. You'd want to avoid a fire hazard, like hot exhaust pipe too close to an oil-soaked piece of foam.

I don't know how the cooling air exits on the QD's like the OP has, tho'.

Jim, "There are worse things than getting a wrong number phone call at 3 AM. It could be a right number."

[hotbyte]

ron.dittmer wrote:
I've been thinking of carrying a 1/2" thick 4x6 piece of carpet foam just to throw under the motor home, under the generator so the noise doesn't bounce around and rattle throughout the campground.

Interesting idea...

[j-d]

I guess I'm one of those who nudged the discussion off track. But many of us are involved in this now, so let me add a few more observations:

We had an old BFA (the "4KW RV Genset" of years ago. Two-Cylinder with no sound box around it. I'm sure it put out more dbA than our current MicroQuiet 4KY, but the sound was not as annoying. Yes, it was a Twin as mentioned above, but it was also an 1800RPM unit so it didn't sound as "busy" as the 4KY which is 3600RPM. I think it needed engine mounts. Rattled dishes in the cabinets but its tone was pleasant. Like a garden tractor locked in a closet.

We used a friend's truck camper with a MicroLite 2800 LPG in it and I was amazed how quiet it was. It was out beyond the rear bumper (the part of the TC not inside the truck bed). Inside it sounded about like the microwave running and easy to talk over outside. But then, the TC was a BigFoot...

I find our 4KY acceptably quiet given that I'm the one benefiting from it running. But I don't run it any more than I have to, and make it a point to use StaBil in the fuel and exercise it often.

[Handbasket]

I have no knowledge of how the QD's are engineered for handling vibration. I just know the 2800, somewhat too well. In a stock installation, the first clamp on my Roadtrek's tailpipe was located on the bottom of the Onan's pan, tied to an Onan rubber isolation mount; that was fine, the tailpipe could shake with the engine. The other (outer) clamp was on a short rigid strap, with its upper end bolted to the fender; _not_ fine!

The rigid mount caused vibration to be transmitted into the structure, increasing noise inside and out. I replaced the strap with a spring (Home Depot, hardware aisle), allowing the tailpipe to move freely. It made a big difference. Thanks to member 'King Willie' for this tip. Y'all with QD noise issues may want to check this.

For those thinking of installing a quiet portable in place of the diesel, remember that the liability will be all yours if it causes a fire or someone dies due to CO poisoning. I'm a retired mechanical engineer & gearhead, but I would not try to rig one up in a permanent install.

Jim, "Mo' coffee!"

[ron_dittmer]

We have an Onan 4000 in our Phoenix Cruiser, the generator behind a good motor home door but open below.

I've concluded that most of the noise is NOT related to the exhaust, but rather "MACHINE NOISE". I've been thinking of carrying a 1/2" thick 4x6 piece of carpet foam just to throw under the motor home, under the generator so the noise doesn't bounce around and rattle throughout the campground. Closed-cell foam would not collect water.

Has anyone tried this?

[Snowman9000]

Lots of interesting points in this thread.

We have only camped in one NP so far. When 8AM came around, generators fired up all across the CG. So I am surprised that they singled out the OP's. Was yours the only one running in a big vicinity?

Some people run their gensets every minute of every allowed hour, and I'm not talking about hot weather and AC needs. I don't know why they do it, but they do. If that was the case, I can see a ranger cracking down. As a fellow camper, I dislike those people. I have no issue with people who run it as needed, but leaving it on the whole time is pretty darn annoying. Gensets are annoying to begin with; I run ours as little as possible if the noise is going to carry.

I've seen references to people clamping a SuperTrapp muffler on, at the CG. DaHose, can you give specifics of what you've done?

I think Winnebago's location on the curb side is dumb. Period. That doesn't change the sound around the CG, but does put the fumes and sound right into the campsite space.

I am really interested in the inverter gen installs. I'll have to log onto the yahoo group and read up on them.

[Dakzuki]

TQUIN45,

Are you familiar with the Skinnie Winnie groups over at Yahoo? You can find out about the Yamaha and Honda installation there. A Honda installation was just done and documented with photos. One of the group Jedi masters is the one with a Yamaha.

Skinnie Winnies

View/Navion Mods

View/Navion Tech

[pnichols]

The bulk of the noise from our Onan 4K generator is cooling air flow noise, not noise out of the exhaust pipe. This air flow noise reflected outward from the sides of your rig varies by what kind of surface you are parked on.

Also, some motorhomes do not have their Onan generators mounted up high enough into their outside compartment. If your Onan is hanging down such that you can see a little bit of the bottom of it from the side of your rig, the outside noise from it will be greater.

With a properly mounted Onan up into a completely enclosed (except for the bottom) outside compartment, noise can be improved by lining the inside of the compartment walls with sound absorbing material and by replacing the vibration mounts with high performance ones.

Noise from your Onan inside your rig depends upon any sound insulating material that you put inside it's compartment, as mentioned in the above paragraph - PLUS - whether or not the Onan is under your rig in an area inside your rig that is lightly or heavily carpeted.

Here's a couple of links to good sound absorbing material and better vibration mounts:

http://www.marinefoam.com/marine-grade-ultra-barrier-plus.html

http://www.avproductsinc.com/index.html

For what it's worth, a poster in these forums quite some time ago had worked extensively on their RV's Onan compartment and gotten their outside noise readings down to around 55 dB. I don't remember what the distances were for their sound measurements, but probably some persistent searching on past posts over a year old would produce the thread.

[TQUIN45]

TQUIN45-
I appreciate all of the information and comments provided by the members on generator noise. I also have been RV'ing for 7 years. I do understand the liquid cooling on the generator is quieter because of the liquid blanket around the cylinders and head assembly. I also agree that 2 or more cylinders will be quieter since the displacement is smaller in each cylinder and the impulses are separated. I do understand that mounting the generator in the RV may reduce or increase depending on how it is done. At the Winnebago factory they did remove and remount the generator this summer because the dealer installed it wrong. Remounting did help. But, the numbers I am measuring now are after they "fixed" it. Yes, we were within the proper time to run the generator- just after 8 AM and we only use for 15 minutes for the microwave and coffee. We also are sensitive to the noise and thye quiet offered at the campgrounds.

What seemed to be missed in my original comments was the Cummins/Onan specification is 68 dBA at 10 feet under 1/2 load!!!! They are doing 78 dBA at 10 feet at 1/2 load. At the rear of the RV it is over 80dBA!

I am willing to consider all suggestions but I have done a lot of work on this for the past 5 months.

Yes, I did buy and used 2 inch diameter silicon tubing to get the exhaust 9 feet from the RV out the rear but that is not permanent. I also paid over $6000 for a diesel generator rated at 68 dbA .

I am planning on replacing the generator with a quiet Honda or Yamaha gas.

Again I appreciate all the comments but my goal was for other people to understand the problems with the View, Winnebago,and Cummins. Please keep in mind Cummins may still resolve the problem- they are at least looking at it. Winnebago generally is a good company and usually strives to solve issues. But in my case and some other people they are not responding.

[EsoxLucius]

The Onan Resonator also changes the tone of the exhaust which most people perceive as a significant reduction in noise.

http://youtube.com/watch?v=gQboSPqKtfE&desktop_uri=%2Fwatch%3Fv%3DgQboSPqKtfE

[DaHose]

I have done some testing by putting different mufflers over the end of my Onan 4000 watt BFA exhaust. I have not measured my SPL levels, but I find that I can reduce sound out of the pipe enough that the mechanical noise of the engine and fan are louder. That is a pretty good din on its own.

The Onan resonator only promises up to one dbA of noise reduction. Doesn't seem worth it. I might find some piping to move the exhaust away from the rear window, though.

Jose

[EsoxLucius]

60 dB at 50 feet is about 66 dB at 25 feet and about 72 dB at 12.5 feet. A vacuum cleaner at 1 meter is about 70 dB. Because normal human conversation is considered to be around 60 dB, anything louder than that can interfere with a conversation.

[EsoxLucius]

I have a Cummins Onan RV QG 3600 LP generator in my 2013 LTV Unity. It is rated for 68 dB(A) at 10 feet running half load. Cummins Onan states that installation can further reduce sound level. I have confirmed this as I have measured 66 dB at 10 feet with my Radio Shack SPL meter while running the air conditioner, 60 dB at 23 feet. To reduce sound levels further I will soon be adding the Onan Resonator (155-2449) to the exhaust pipe, a clamp-on Super Trapp 5S with resonator and three diffuser discs (to be in place only when using the generator), and as many layers of Low-E automotive insulation as will allow required clearances in the generator compartment. I have read that the Onan Resonator and Super Trapp will virtually eliminate exhaust noise to the point that the sound produced is essentially vibration and internal engine noise. I am hopeful for better than Honda-like 58 dB at 23 feet.