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Topic: How Loud Is Your Generator?

Posted By: higherroad on 05/01/12 03:58pm

My '92 Roadtrek has a Onan Microlite generator. It works fine, starts up well and runs the ac and microwave well. But, it's loud! And, being right under the bed shakes the bedding area. This is my first generator and I'm just learning about them. Is this amount of noise to be expected from an old generator or is there some tuning or maintenance that can be done to quiet it down a bit?

Posted By: retraite on 05/01/12 04:09pm

IMHO, there are a couple of things you can do.

First, add an Onan resonator "inline" to the genset exhaust. It's a cut and weld proposition, but fairly easy for a welding or muffler shop to do.

Second, make a small modification to the way the genset exhaust pipe is attached to the body. Remove the rubber mounting joint and replace it with a spring.

Both MyRoadtrek and Handbasket have posted on each of these points regularly and will likely chime in. Or, you can search earlier postings for their photos.

I've done both - thanks to them - and it DOES make a difference.


Posted By: gerrym51 on 05/01/12 04:21pm

go to rodgers website myroadtrek. he has a full section on this

Posted By: Handbasket on 05/01/12 04:36pm

Assuming it's an Onan Microlite 2800.... On one that age, I'd suggest dropping it and removing the top green part of the box. There's a muffler inside the box (passenger's side), and that's the only way to inspect it & the piping leading to and from it.

This old post of mine shows it with the top off; 1st photo is from the service access door side, and the muffler is on the right with a pipe leading to it from the cylinder head. Be sure all that stuff is intact.

That'll get you started. Then check the tailpipe. Be sure it's free to vibrate. Roadtrek has been known to use a too-rigid hanger on the outer part of the tailpipe. If it's constrained from shaking around, vibration is transmitted into the body thru the hanger, and the Onan isolation mounts can't work right. See Rodger's excellent web site for more info on that, and the Onan tailpipe resonator.

I'll post some more minor things you can do later.

Jim, "Beer me."

'06 Tiger CX 'C Minus' on a Silverado 2500HD 4x4, 8.1 & Allison (aka 'Loafer's Glory')

Posted By: MAU MAU on 05/01/12 05:00pm

Here is a video showing the effectiveness of the resonator.

Roadtrek 170 Popular

Posted By: Jerrybo66 on 05/01/12 05:32pm

I always thought that mega amounts of insulation was needed to deaden sound. Not true. I don't know your situation but sound causes vibration, vibration causes more sound. Because of the suggestions from the good folks on this forum I covered the dog box of my Arctic Cat Side-by Side with "Dynamat". I would of never thought the plastic box was vibrating to amplify the sound of the motor that much. If your generator is housed in a metal box I suggest you cover it with "Dynamat", as recommended by this group. It's expensive but with all the rip-off products today it's worth it. I've heard about Danamat before but because of the cost didn't have the courage to try it until the recommendation from this group. It's about $65.00 for 12 sq. ft. There's another less expensive product with an asphalt base that can't stand heat. I didn't want it.... As for the above, I've been there done that, but still, in my opinion.. Good luck..

Support the Country you live in or live in the Country you support
2003 Sierra SP 26'Toy Hauler
1997 F-350, PSD, 4X4, red Crew Cab, long bed.
2007 Arctic Cat Prowler, Arctic Cat 500

Posted By: SWD on 05/01/12 05:50pm

I have a Yamaha 3000 at the back of the unit and when we are watching TV at the front of the rig , you can hardly hear it. Its just a soft purr.

Posted By: BudJ on 05/01/12 06:04pm

"Is this amount of noise to be expected"

Don't know how loud the noise is, BUT the Onan used in class B's are LOUD.

Some solutions have been offered above, but it is still considered a loud RV generator. It is not a Honda or Yamaha. If you could eliminate All of the exhaust noise, it would still not be a quiet RV generator.


Posted By: Davydd on 05/01/12 07:37pm

No matter what you do to deaden the sound you are still going to save lots of quarters with your free magic fingers bed. [emoticon]

2015 Advanced RV Ocean One Class B
Visited states in an RV

Posted By: Road-Trekker on 05/01/12 08:14pm

Here is another Onan resonator install. I replaced the factory exhaust hanger with an automotive rubber exhaust hanger. The resonator install really makes a big difference.

edit. link fixed

* This post was edited 05/02/12 10:52am by Road-Trekker *

Roadtrek Agile SS: Roadtrek Modifications

Posted By: SkipJ on 05/01/12 08:30pm

Noise isn't a problem in my Airstream B190, but very loud in my Outfitter truck camper. Some things for me to look at.

1992 Airstream B-190 van
1989 Airstream 25' Excella Trailer
Outfitter Apex 9.5 Truck Camper Ford F-350 Diesel 4x4

Posted By: Handbasket on 05/02/12 05:46am

I really wouldn't put any sound deadening material directly on the outside of the 2.8 Onan's box. The Onan installation manual requires a minimal outside clearance on all sides for cooling. It's been 5 1/2 years since I read it, so I don't recall for sure. I think it was either 1/2" or 1". You could attach it to the underside of the floor over the generator if the mount will allow clearance.

Your RT's underhung Onan's mounting should be similar to my old '02 C190P's.... hung from two side plates that run up to the frame, with two struts forming a 'V' brace on the forward side.

First, check the V brace. Mine was rubbing on the lip where the green fiberglass part of the box meets the black metal pan. I did a little creative filing with a wood rasp on the f'glass part. Made a noticeable difference in inside vibration.

From here the explanation gets long-winded, and going further depends on how much effort you want to go to for minimal gains.

You should have five bolts going from the side plates (2 each) and V brace (1) into the black base pan. Remove one, and buy 5 identical bolts 1/4" longer. Buy five flat washers & 20 neoprene washers to fit, and a tube of blue (removable) Loctite.

Loosen the side bolts; remove 1; pry the side plate out a little; put a metal washer & two rubber washers on a long bolt with a dab of Loctite in the end threads; insert the bolt thru the side plate and two rubber washers (tricky but doable); tighten the bolt just 'snug'(don't overtighten & crush the rubber). From the bolt head in, you'll have a metal washer, 2 rubber washers, side plate, two rubber washers, and the black base pan. Repeat on all other bolts. The Loctite will hold the snugged bolts, so the rubber washers don't have to be crushed. This should help a small amount with vibration.

One more item, later.

Jim, "Mo' coffee!"

Posted By: LonerGlide on 05/03/12 02:04am

I dropped the onan and bought a 3000watt ransond
it has a honda motor, is very quiet,, cant hear it inside with tv on
and best thing is got it new off ebay new for $688.00,, honda or yamaha u will pay $2500-3500 and it has better specs an longer run time!

Posted By: Handbasket on 05/03/12 07:25am

Last & easiest quieting tip, mostly for pavement... A lot of the Onan 2800's noise exits thru the same opening as the cooling air and tailpipe. It's a 3" square hole on the bottom, with the tailpipe in the middle.

_If_ yours sits high enough for it not to create a fire hazard, place an old scrap of carpet about 3' square on the pavement under this exit. Long-pile or shag probably works well.It'll absorb some of the sound that would otherwise reflect off the hard surface.

If I was going to be somewhere for while, and looks didn't matter as much as quieting, I might consider surrounding the back of the van with some pieces of rigid insulation leaned against the bumper and sides behind the back wheels.

There are three main noise sources on the small Onans. The obvious one is the tailpipe. The second and less obvious is the cooling air exit with a bunch of sound coming with it. The least obvious is the rush of cooling air going in thru the slots beside the access door. In case it's not obvious, do not interfere with the cooling air in or out.

My Tiger (small C) uses an Onan 2800 mounted in a compartment right in front of the spare tire. I've quieted it to about Honda levels (56 dbA @ 23' regardless of load). I can stand right over the exhaust and carry on a normal-voice conversation. And the inrush of cooling air is a distinct separate noise, heard on the other side of the spare tire. Took quite a lot of tinkering to get there, tho'. My former RT's underhung Onan couldn't be quieted to that extent, but was much better after taking the steps I've outlined.

Jim, "Mo' coffee!"

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