Author Topic: portable generator  (Read 172238 times)


  • Guest
Re: portable generator
« Reply #15 on: September 14, 2005, 02:53:34 PM »

Yep, the muffler is fine. Only have a few hours on the genset. Still practically brand new. It is just too loud for those around us at campgrounds or even boondocking.


Please post your box construction info. That sounds like what a few of us really want to do.  There is a huge group on RV.NET with a 120 page thread going back to the first of the year discussing this very thing and how to make decent gensets as quiet as the big $$$ Honda and Yamaha units.



  • Guest
Re: portable generator
« Reply #16 on: September 16, 2005, 05:42:09 PM »

I never bothered with much quieting for my 4000XL. All I did was was mount it to a ¾" plywood and 4x4 skid. I built a 3-sided box but that was mainly for weather protection during a hurricane and off-duty protection. This generator is not loud enough to be bothersome to us due to the construction of our home. I can't even hear the UPS truck pull into the driveway when working in my office right next to the drive. The noise certainly bothered no neighbors since the closest ones are ¼ mile away. I'm sure using it in a campground would be an entirely different story.

My diesel unit is a different animal. That puppy is loud. I built this thing a house. The bottom plate sits flush on concrete slab and is framed with full-cut 4x5 beams and sided with full-cut 1x6 heart pine barn boards and all the joints are caulked. I insulated it with R-13 and inside of that, I used aluminized sheathing. I routed the exhaust stack out of the building and 10' up where turns away from the house.  I wrapped the exhaust with header tape  to compensate for added back pressure and improve heat reduction. The ends of the house are ducted and baffled for airflow and the generator can be operated with the doors closed and locked. The fact that it's water-cooled with a high capacity engine fan allows for this. Air moves through the house like it's a wind tunnel. The roof is vented and baffled to allow heat to escape. These modifications reduced the sound level inside our house, and even on the proximate back porch,  from oppressively loud to virtually un-noticeable.

For a portable generator, I liked the ducted box design that was published at the supersoundproofing web site a while ago. That particular design seems to be missing now, having been replaced with a triple box design.  For portable camping usage, a ducted box would be great but this new triple box design would be difficult to deal with. Ultimately, it would be quieter but you'd have to be very conscious of heat. Generators don't do well with a lot of that.

I can email you pictures of my setup, if you're interested.



  • Guest
Re: portable generator
« Reply #17 on: September 17, 2005, 08:44:45 PM »
I did the box inside a box thing last night using 3/4" thick foil backed foam board from Home depot.  This was just a test.  It did quiet things down a bit but no tthat much.  I think the foam board may be too rigid.  I then used some old carpet I had laying around and wrapped it around the generator and did the box in a box trick again.  Big difference!  I think the more absorbent of sound the insulator is the better.  I have a Power Pro 3500 form Pep Boys that I am using to power my RV and would like to get it as quiet as possible.

Quinn Bean

  • Guest
Re: portable generator
« Reply #18 on: October 10, 2005, 04:21:08 PM »
I am just get back to this forum after a long time.  I sure would like to see those drawings and other imfo aabout the exhaust.  I am planing on doing the mods to the 4000exl next week. :-/

Bill Joyce

  • Guest
Re: portable generator
« Reply #19 on: October 22, 2005, 05:17:49 PM »
I used a "sandwhich" of foam(looks like rubber) and composite.  It is simlar to material sold by WESTMARINE and BOATERSWORLD. I think I've reduced noise 20 to 30% but gets too hot. I
am now about to install a fan but don't know where to install it without compromising the noise reduction The engine end and front are the nosiest. Any idea wherelse I should place it. That I have to cut another opening in the box is disturbing.  Were I to do this again would use a db tester.

Actually  wouldn't do it again--would sell the Generac 4000xl for about 4400 and buy something else.  The hassle is too much for the results.

Having gone this far woould really ppreciate advice on fan placement. Are yo guys allowed to post your eail addresses and phone numbers?

Thanks, Bill
253 686 1414

Al Pfalzgraf

  • Guest
Re: portable generator
« Reply #20 on: November 07, 2005, 06:57:38 PM »
I've got a Generac 5500xl and am in the process of building a muffler based on this:
It will be a while before the results are in.


  • Guest
Re: portable generator
« Reply #21 on: December 27, 2005, 04:00:48 PM »
The box diagram and muffler is at


Kerry Ianacone

  • Guest
Re: portable generator
« Reply #22 on: February 16, 2006, 06:34:12 PM »
i did the upgrade muffler for the 10 hp tecumseh engine (made by them, not aftermarket) on my coleman 6250 generator.  it made a decent improvement!  But the real difference, and this is going to kill you how easy and cheap it was, was my making a frame out of 3/4" PVC that was 8" wider and longer than the generator (about 12" taller) and drapped heavy blankets (the ones used to cover furniture during a move) around it.  it is ridiculous how well it worked!  no issues with overheating since the clerance all around it is adequate and the top is completely open.  One more thing, i added an albow to the exhaust so it vents straight up and not into the blanket.  If anyone is interested in pics or links to the blankets i boght from Ebay (6.5 lb heavy duty ones) just email me

Harry Roscoe

  • Guest
Re: portable generator
« Reply #23 on: February 26, 2006, 06:30:15 AM »
I saw your post on quieting your generator and wonder if you would be so kind to send me a picture.  Thanks



  • Guest
Re: portable generator
« Reply #24 on: April 03, 2006, 08:16:38 PM »
Funny you say that.
When camping I just leave mine in the back of my Pickup (Dodge 2500), with the tailgate up.
Cuts the noise way down, for surronding campers. Noise can only go up.


  • Guest
Re: portable generator
« Reply #25 on: May 25, 2006, 03:59:07 AM »
Using water tight flexible metal electric wire conduit you can route the exhaust into a larger muffler. I used 1" dia. and sleeved it with 1.5" conduit. My flexible exhaust
could be removed and installed as needed. I did have to cut the old muffler away from the mounting flange and exhaust tube. Brazing the conduit onto the tube and flange was no problem.

I also used insulated metal panels to line my generator compartment. These panels came from a metal door manufacturer. I would put my generator up against any in the campsite..... anytime.


  • Guest
Re: portable generator
« Reply #26 on: July 26, 2006, 03:46:39 PM »
I now assume that nobody  else has this problem.  Or is it everyone is not going to speak up if they did.  Surley someone has a help.


  • Guest
Re: portable generator
« Reply #27 on: September 27, 2006, 10:55:16 PM »
hi bulldozer,

There's three pages of replies to Quinn Bean's 5/26/04 message on the Forum.  There is great info contained in almost all of them - check out the links and diagrams.  Just for drill, here's an updated link to check out



  • Guest
Re: portable generator
« Reply #28 on: August 29, 2007, 04:44:37 AM »
I bought a inexpensive gen at BJ's wholesale for $199.00 and it produces 3250 watts @ 68db....
I spent $15 at home depot for 3 2'x4' accoustic panels (ceiling type) and some duct tape.  Made a 3 sided box pointed at the river at camp and at 50' gen could not be heard....(with a little breeze)  Unfortunately these panels are basically made of paper...not good in the rain.

I am planning to build a foam box and fiberglass over it...and am looking for a high temp material to cover the inside of the exhaust end of the box.

any comments?....Suggestions?

Thanks, Brad


  • Guest
Re: portable generator
« Reply #29 on: May 29, 2008, 12:07:47 AM »
I wanted to add some more requirements to a portable generator box, dont want to hyjack the thread but think these are valid for this group...
I have a 3500W 6 1/2hp gasoline Genset to use camping. It is alledgedly rated at 68db (but I doubt it really meets that). I think that National Parks allow up to 72db but that is still too LOUD. I am cheap so the box needs to cost under $100 total, light weight and can be broken down for transport.  Only used 2 weeks a year (during summer for AC, dont need generator during winter) so materials can be cheaper.
I need comments/opinions on this:

A single box that is 24Hx30Wx36L (this gives about 3" of clearance all around)
Made out of 2" thick HVAC Ductboard ($50 for a 4x10 sheet).
Assemble with velcro
add a layer of accoustical tiles (cheap left overs from Lowes/HD)
4" dia cut outs on 2 opposite sides (for a 120mm computer fan). box around the openings so they are not straight thru (not sure how to explain this correctly)
wrap the whole thing in loaded vinyl OR 1/8" foam mat (moisture proof/resistant)