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HDT Generator Exhaust Routing


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I know some of you have generators hard mounted to your HDT's. I am in the process of mounting mine on the front of my flatbed, and wondering what everyone has done to route the exhaust fumes away from the cab and/or trailer.


A little background... I purchased my truck used, and the previous owner had built the flatbed to use for an oilfield truck. Any significant reworking of the bed will require starting over because of the way he integrated the toolboxes into the design.

We use the truck for weekend and week long trips, and pull a GN with 2 4wd's. We sleep in the sleeper (60" condo) currently, and will do so for the shorter trips. I purchased a dry van trailer and am in the process of converting it into a camper with capabilities of hauling 2 rigs. The sleeping area in the trailer is in the front.


I am currently planning on mounting the generator in a compartment on the left front of the bed. I will be moving the battery box forward approx. 18", which will give me enough room to build a compartment with a door. I already have a heavy duty slide that will allow the genset to be pulled out for maintenance, and more airflow if needed. The genset will power my shore power connection in the sleeper, and also power the trailer upon completion. The genset I have is a 3500W (not sure on brand, memory is horrible), but I know it is kinda loud.


I am tossing around ideas of modifying the exhaust on the genset to quiet it more, and I also want to route it away from sleeping areas. I am thinking about removing the factory muffler, connecting a flex pipe from the muffler flange to the back of the sleeper, then running a stack with a car style muffler up the sleeper, using the fairing mounts and rubber isolators on the brackets.


Does anyone see why this wouldn't work?

For those with gensets in compartments on your bed, how is your exhaust ran? Any issues with fumes getting into the living spaces?





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I am in the middle of the same issue, my 7kw diesel generator is mounted under the passengers side of the cab just fwd of the 100 gallon tank and behind the Regen device. We original hooked the generator exhaust directly into the truck stack but with no muffler. It sounded like a drum. Next a stock muffler of some sort was installed but it still makes too much noise. Plan 3 is to install a 2 stage Onan muffler and have it dump into the trucks vertical exhaust. Camping World sells a stack that attaches to the side of the Morohome and directs exhaust up and away.


There is an outfit in Florida that can provide an enclosure made of Mass Loaded Vinyl with a frame and fan. They provide a template you fill out the measurements and the enclosure is made to fit. For my 7kw, cost is 1400$


I've learned that air doesn't mind changing directions but noise doesn't like to. Baffles and offset air intake and exhaust are part of this. Intake low left or right, exhaust high and opposite rt or left. These enclosures come in pieces, 4 sides and a top, all Velcro together. Make sure even the smallest holes are covered over, a small hole will let out a lot of noise.


For a few bucks the generator can be installed on noise deadening or abatement feet.


I would have the generator on a relay so that the fan starts first like a gas furnace then the generator. Also there should be an overheat shutoff so if the fan cuts out the generator doesn't cook itself.


To sum up, Onan exhaust is the next step Cost about 500$ , if more noise abatement is needed then the enclosure will be next. Another 1400$ The generator doesn't get used much so I'm not prepared to scrap it and pay 10k ish +++ for an 8-10k Onan





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Don't forget guys that it's not just the exhaust making the noise. It's the fact that the cheaper generators run at much higher RPM.

If you're going to truck mount it I highly highly highly suggest go buy a Honda. You can get 3000 up to around 5500 W for $2000 to $4000.

I dry camp 90% of the time and do just fine with the 5500 W generator. Built into my trailer.


If you're willing to spend $1900 on mufflers and enclosures. Why not spend $2500 on a super quiet generator?

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I personally would not run the exhaust up the fairing on the truck The cab should be air ride (?), and the movement of the cab would sever any connections or break the fairings.


As broncohauler states, it is the generator build methods that make a lot of the noise, not the engine exhaust. There are hundreds of videos on youtube of people making all sorts of exhaust mods in attempts to quiet a generator. A couple decibels is all they get. The resonance of the cooling fins for example, will cause a considerable amount of noise. They can be dampened somewhat with small rubber blocks, but still only so much can be gained from a band-aid.

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True, the cab is air ride. I didn't think about that. Although I believe that with the flex pipe between the genset and the stack, it should be fine....shouldn't be any different than the exhaust stack on the truck that runs up the fairing on the other side.


For clarification, I am not worried so much about the noise, as I am about the CO from the exhaust getting into the sleeping area. We usually dry camp, and don't require much for amenities. My fridge is 12v, and other than a tv and small computer, I don't use power....unless it gets cold. If it gets that cold, I can handle the noise of the genset to run an electric heater. As stated above, my genset is paid for, and as much as I would love to have a Honda, I can't justify spending 2-4k on one when I don't use it that often. I would rather spend that $$ on things for the trailer build.


The main reason for installing the genset is to recharge the batteries and have 110v when needed. Normally, I would just throw it in the back of the truck or on the trailer, but I want to permanently mount it in a compartment, out of the way, and out of sight. I was thinking of adding a different muffler into the stack to help quiet it a bit, but mostly because I would have to remove the stock one to attach the flex pipe. Again, noise isn't my first priority, the CO is. I don't want to start the thing up some night and die because I needed some heat in the cab.

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On most trailers with generators.

The exhaust runs out on the driver side of the trailer that way when you're sitting at camp you don't have the noise or the smell.

Seems like you could just mount the generator on the driver side if possible and run your exhaust out from under the bed on the driver-side.

If you're concerned about carbon monoxide.

I know a lot of people have bought battery-operated carbon monoxide detectors from Home Depot and put them in their sleeper.

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I am planning on taking the truck camping next weekend. Since I don't have the genset mounted yet, I think I will set it on the flatbed, or maybe under it to see how it works. I will be getting a CO detector, seems like a good idea. If it isn't an issue, then just exiting the exhaust out under the bed would be the easiest way to do it. The only place I have room is on the drivers side, so that makes that easy as well.

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HI Chris!

First I agree that the exhaust isn't the big noise maker. For the life of me I can't figure out what noise my onon muffler muffles. I have, just last week tried adding an additional muffler to my Bob Cat 8000 watt gen/welder to quite it down. I used a brand new Onon muffler in tandem with the oem in place. This machine has a 16 HP Onon engine. I could not hear any improvement at all! Black Rock exhaust systems makes an adapter to tie your generator directly into the truck exhaust system safely.

If I was setting up this type system I would have a look at the genset set ups in a diesel pusher, many are located where the Gas engine would be and are very quit.

My 5500 Onon Marque generator in my 5r, located in the front storage compartment under my bedroom is so quit more than once we have gone to bed only to get back up to turn it off. We do boondock a lot and the genny has 1400 hrs. on it over an 11 yr. period.

My 6000 watt diesel silent runner supposedly generates 71 db @ 20'.. Supposedly because of the cabinet insulation. The big 10 and 20k gensets from the rental companies are also very quit due to the sound proofing in the cabinets. So mufflers are a very small part of the answer. JMHO.


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