Generator noise

[Steve Bryant]

Protagonist,
Thanks for telling me about the username. I am always curious about the choice of names and words as I am a kind of wordy person (some might say that I blab too much). But I am always curious about word choice, derivation, etymology, how words morph over time...all that geeky stuff.

I also once met a man who named his airplane Panacea. When I asked him about his choice of names, he responded that I was one of the first persons to ask about the details of the name selection over several years of ownership. He also owned a boat with the same name and he felt no conflict because one vessel was nautical while the other was aeronautical in nature!

All my best,

Steve

[withidl]

As some of you know, I have an Onan Microquiet 4000 genset "inboard" of my 2002 ASCL 31' (mounted under the curb side twin bed in the storage compartment). The exhaust note is VERY minimal, like rapidly puffing air, and is not annoying even within a couple of feet.

The engine mechanical and intake/cooling air noise is another matter though. It is heavily muted (normal conversation is no problem) when the curb side storage door is closed due to the door's insulation and the very convoluted air draw from under the frame; but when the storage door is open it roars and is not pleasant anywhere at curb side. Inside, the twin bed mattress and the 3/4" plywood containment enclosure along with the bed under storage compartment enclosure mutes 95% of the noise.

When the genset is running I'm only cognizant of it if I'm consciously thinking about it.

[cwf]

For noise reduction we have attached larger flex stainless exhaust, at least 1/2 diameter larger and ran over 10 feet. No problem with back pressure. Next, we wrapped in Evil As-bestos for noise and heat reduction.

Now you could use the high temp options for wrap.

Use muffler hangers for support.

If you want full support, sleeve with pipe and paint...it use aluminum pipe

[Inland RV Center, In]

Originally Posted by cwf

For noise reduction we have attached larger flex stainless exhaust, at least 1/2 diameter larger and ran over 10 feet. No problem with back pressure. Next, we wrapped in Evil As-bestos for noise and heat reduction.

Now you could use the high temp options for wrap.

Use muffler hangers for support.

If you want full support, sleeve with pipe and paint...it use aluminum pipe

Generator noise is caused by the hot exhaust expanding, as it's released.

Cooling the exhaust gas, will quiet the system.

Attach an extension to the exhaust pipe, and you will be amazed how many DB you can reduce the noise by.

Use an adequate size pipe or flexible tubing of 10 feet or more. It should be the same size or a little larger than the exhaust pipe.

Some do it so well that the only noise you really hear is from the generator guts.

Andy

[xrvr]

An onan resonator is available. My local AS dealer has one on the shelf. JD Sanders RV. Also there is the Venturi? Which is attached to the exhaust and goes up along side the vehicle to exit the fumes and some noise away from ground level. Genturi? This s used after stopping for the day. Jim

[David M]

Originally Posted by Inland RV Center, In

Generator noise is caused by the hot exhaust expanding, as it's released.

Cooling the exhaust gas, will quiet the system.

Attach an extension to the exhaust pipe, and you will be amazed how many DB you can reduce the noise by.

Use an adequate size pipe or flexible tubing of 10 feet or more. It should be the same size or a little larger than the exhaust pipe.

Some do it so well that the only noise you really hear is from the generator guts.

Andy

Hello Andy,
Can your shop weld in the resonator noted above for me? I'm also interested in solar panel replacement and addition. Your shop is not too far from me, in fact, you're right down the street from where I bought my Interstate (Southwest Coaches). Thanks in advance.
David

[Mcrid]

I modified the generator's mounts and did a little insulating today and was able to get a 4.5 decibel reduction inside the van and maintain the reduced vibration level I had previously accomplished. Pretty good outcome. Here are the details. Wife and I sat int he back today with the gen running and had a normal conversation.

The iPhone Apps are not that reliable for decibel readings, but the delta should be relatively close.

[Boxster1971]

Thanks for posting the details - this mod is now on my ToDo list.

[Lotus54]

I wish I had a diesel generator. The propane tank is so small in the T1N and the fuel tank is pretty big.
But I'm sure it would be a huge chore to change it, and I really have not had to run the generator that much. I would have run it a lot more on my last trip- but I didn't want to run out of propane (I couldn't leave my camping spot during the event)

Mark

[Mcrid]

Originally Posted by Boxster1971

Thanks for posting the details - this mod is now on my ToDo list.

If I was doing it over, I'm not sure I gained much with the sealing washers over the 1/8 rubber washer. I would use the following: https://www.grainger.com/search/raw-...3Fsst%3Dsubset

[Boxster1971]

Originally Posted by Mcrider

If I was doing it over, I'm not sure I gained much with the sealing washers over the 1/8 rubber washer. I would use the following: https://www.grainger.com/search/raw-...3Fsst%3Dsubset

Good point - I was thinking more rubber would help. I have an ATV/Motorcycle lift that makes working on or dropping the generator pretty easy. I got it at Harbor Freight last year but I just looked and they don't carry it anymore. It looks like the one from Sears and shown in linked review. You probably have one since you're into motorcycles.

http://www.sears.com/craftsman-profe...p-00950191000P

http://onemansblog.com/2016/06/10/re...torcycle-lift/

[1olpony]

I just added a reasonator and am very pleased with the results. It took a muffler shop less than 15 minutes to install. I ordered the unit from Airstream that is used on 2018 coaches, way over paid for parts, but now the sound is within reason for use in a campground. (now if there is something that can be done with the AC)

[Mollysdad]

Sound is transmitted as vibrations in the mount as well as through the air.
Since you say it's quieter inside, I'll speculate that it's not the rubber isolation mounts shaking the RV.
From across the parking lot, the noise you hear is probably then through the air, or the muffler. Perhaps you can replace the muffler or add one to the exhaust that won't restrict the flow much more.

[Boxster1971]

Originally Posted by 1olpony

I just added a reasonator and am very pleased with the results. It took a muffler shop less than 15 minutes to install. I ordered the unit from Airstream that is used on 2018 coaches, way over paid for parts, but now the sound is within reason for use in a campground. (now if there is something that can be done with the AC)

Please post a photo if you can. I'd be interested to know if this reasonator is the same one that Onan sells. I suspect it is just like this one:
http://www.americanrvcompany.com/Cum...and-MicroQuiet

[FlyFishinRVr]

Originally Posted by Boxster1971

Please post a photo if you can. I'd be interested to know if this reasonator is the same one that Onan sells. I suspect it is just like this one:
http://www.americanrvcompany.com/Cum...and-MicroQuiet

Thanks for the link Mike.

I just saw this in the description:

Benefits

Softens exhaust noise and can reduce sound levels in some installations up to one dB(A).


Really?!?! ONE lousy dB of reduction? I realize we're talking dB here so it's a log scale, but sheesh, that's not much improvement....

[Mollysdad]

My Onan did not have a 1 1/2" exhaust pipe. More like 1 1/8".

[Titus]

I measured the db inside and outside, with gen idling and under load, before and after installing the resonator. The db difference is minor, but worthwhile in my opinion. The noise outside is now such that I don't feel guilty running it during the authorized hours. Inside the biggest benefit was in getting rid of a sharp rap that was especially bad when the generator was under load.

To spruce up the look I slipped a chrome drain pipe over the OD of the gen exhaust pipe where it sticks out the side of the AI. I had them put three little weld bumps around the outside of the exhaust pipe near both ends of the chrome pipe. I then filed these bumps down a little at a time until I had a press fit of the chrome over the exhaust pipe. The inside end of the chrome is held by the outer pipe hanger. The three pips keep it from rattling around.

[felixkagi]

Originally Posted by Boxster1971

Please post a photo if you can. I'd be interested to know if this reasonator is the same one that Onan sells. I suspect it is just like this one:
http://www.americanrvcompany.com/Cum...and-MicroQuiet

Just installed one of those over the weekend, plus the Boom Mat treatment.

So for a little over a hundred bucks and some sweat equity, it's worth it. The Cummins Onan resonator quiets things down in the outdoors so you don't have to be embarrassed any longer.

On the boom mat the jury is still out. On the inside, things are perhaps a tiny bit quieter. However, on the outside the engine noise seems to be more muffled and again together with the resonator it's a worthwhile undertaking.

[amirm]

According to this video the resonator makes a nice difference:

[video]

[itsmeok]

Yeah, that seem to make it go from standing at your own lawn mower to your neighbors lawnmower running.