# Can I connect a generator to a standard car muffler to reduce the noise?



## cityprepping (7 mo ago)

I just purchased the Westinghouse WGen7500DF Dual Fuel Portable Generator and am in the process of building a generator shed to quiet the noise down. I have figured out most of the primary requirements to build out this shed, but after watching one YT video in particular, in the video he builds a separate muffler with a trashcan that looks a bit complicated. I figured using a standard muffler I could either pick it up at a scrap yard or buy a basic one from Amazon (I see them as cheap as $25 online), I could run a 2-inch pipe from the generator exhaust to the muffler to reduce the noise significantly.

Assuming I could figure out connecting the 2-inch exhaust to the generator and running it out of the small shed, would a setup like the one I'm describing (connecting a car muffler) work? If there's a better way recommended to reduce the noise coming from the exhaust, I'm totally open to anything. In the video referenced above, in his original video, he used a 1-inch exhaust, and then in a subsequent video, he created a different muffler and swapped out the 1-inch to 2-inch exhaust to reduce pressure back on the generator.

Thanks!


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## Browse Deweb (Jan 16, 2021)

For people who want a quiet generator, they usually buy an enclosed inverter generator. There are number of advantages...quieter, more fuel efficient, perfect sine wave output. I think I saw a video of a guy who put a muffler on his generator and it didn't really do much good. I wouldn't put a generator in an enclosure unless it had really good cooling.


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## cityprepping (7 mo ago)

Browse Deweb said:


> For people who want a quiet generator, they usually buy an enclosed inverter generator. There are number of advantages...quieter, more fuel efficient, perfect sine wave output. I think I saw a video of a guy who put a muffler on his generator and it didn't really do much good. I wouldn't put a generator in an enclosure unless it had really good cooling.


Thanks for your feedback!

I've already set up the shed and the generator and have cooling and noise reduction in the box figured out. At this point, I just need to figure out the muffler setup. I have also noticed some point out a motorcycle and not a car muffler is the way to go for these types of engines.


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## GenKnot (Dec 20, 2021)

It helps if you point the exhaust from your shed setup skyward in most cases.


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## OrlyP (Oct 19, 2021)

For small engines, I'd say that about 80-90% of the noise you hear comes from the crankcase and gen head.... all that combustion, pumping noises, and whirling masses of steel and aluminum creates that piercing clatter, usually at high frequencies and annoying as ****. That in itself can mask the noise from the exhaust. In other words, the only time you'll notice the exhaust noise is when the gen is put inside a sound-proofed shed with only the exhaust pipe sticking out. 

For most, having the gen in an enclosure is enough to reduce noise. The exhaust isn't really that loud, in the grand scheme of things, and most people just leave it as is (albeit, with a flexible pipe extension). Adding a second muffler (car or motorcycle) will further help reduce exhaust noise.... _some better than others*_. If any, it may help to cut down on the more obnoxious frequencies and you're left with an exhaust note that is a little less annoying.

* Mufflers works best if it's tuned to match the engine characteristics (backpressure, frequency, RPM, etc.).... there's a whole science on that and I don't claim to be knowledgeable on the subject.


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## exmar (Jun 29, 2015)

GenKnot said:


> It helps if you point the exhaust from your shed setup skyward in most cases.



Agree, as far as noisy exhaust goes, just remember, rain falls down and not good to fill the exhaust system with water. Attached a link to a "flapper" to close off the exhaust when not running. What I don't know is if an engine that small would generate enough pressure to open the flapper. These are quite common on farm tractors and stationary AG engine applications, but those are not single cylinder engines. Exhaust back pressure can be an issue in small engines, e.g. posts here on plugged or partially plugged spark arresters should be considered when creative exhaust modifications are being evaluated.




Amazon.com


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## tabora (Sep 6, 2018)

exmar said:


> What I don't know is if an engine that small would generate enough pressure to open the flapper.


That is not a problem. There is a LOT of exhaust pressure. However, I always used to put a can over the exhaust on my Dad's tractor when not being used. Just in case the wind would blow it open during a downpour...


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## iowagold (Jan 22, 2020)

cityprepping said:


> I just purchased the Westinghouse WGen7500DF Dual Fuel Portable Generator and am in the process of building a generator shed to quiet the noise down. I have figured out most of the primary requirements to build out this shed, but after watching one YT video in particular, in the video he builds a separate muffler with a trashcan that looks a bit complicated. I figured using a standard muffler I could either pick it up at a scrap yard or buy a basic one from Amazon (I see them as cheap as $25 online), I could run a 2-inch pipe from the generator exhaust to the muffler to reduce the noise significantly.
> 
> Assuming I could figure out connecting the 2-inch exhaust to the generator and running it out of the small shed, would a setup like the one I'm describing (connecting a car muffler) work? If there's a better way recommended to reduce the noise coming from the exhaust, I'm totally open to anything. In the video referenced above, in his original video, he used a 1-inch exhaust, and then in a subsequent video, he created a different muffler and swapped out the 1-inch to 2-inch exhaust to reduce pressure back on the generator.
> 
> Thanks!


check your conversations.
i sent a direct bunch of info.

the guys are right . 90% of the noise is from the gen chassis and engine case.
so a well designed gen shack with good air flow and off set baffles inside works well.

going up is a great plan!
you can also use a T and have the rain go down or maybe use a duck bill grommet at the bottom for a rain and moisture drain.

you need to break up the noise in the up pipe with a set of screen vortex cone punch plate just like inside a good muffler..
a long exhaust tube makes a trumpet noise...

you can also use double wall or triple wall vent tube like for wood stove or gas water heater.
they will stand the heat and are easy to put together.
duravent is a good brand. but cost is up there for the good stainless sections.
and will last a life time!


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## Number21 (8 mo ago)

I recently bought a Champion fully enclosed generator, and was surprised how "enclosed" it really is. The muffler is not really any bigger than a typical generator, but they went nuts insulating the cabinet and also appears to have some kind of silencer on the intake.

With it running at full speed right outside my door I can't hear it inside over the air conditioner it is powering. I could put it farther away but there is no need. It is amazing how much of the sound is not from the muffler when comparing this same engine in open form!


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## tabora (Sep 6, 2018)

Number21 said:


> With it running at full speed right outside my door I can't hear it inside over the air conditioner it is powering. I could put it farther away but there is no need.


You should place it well away from the structure. CO poisoning is a real threat.

Federal agencies like the CPSC and CDC offer guidance about proper portable generator use. They advise consumers to operate portable generators outside only and keep them at least 20 feet away from the home, exhaust facing away from all structures. They urge installing battery-operated carbon monoxide alarms near every sleeping area and testing them frequently.
15 of the 526 carbon monoxide deaths caused by portable generators in homes between 2004 and 2013 resulted from machines being used outside. In most fatalities, the generators were being used in an indoor basement, garage or "non-basement living space."

*The National Institute of Standards and Technology (NIST) Recommends Portable Generators be placed far from house...*
Portable generators can produce more than a hundred times more carbon monoxide than a car exhaust and, per the CDC, should not be operated indoors or within 6.1 meters (20 feet) of a window, door or vent where generator exhaust can enter an enclosed area.


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## tabora (Sep 6, 2018)

Number21 said:


> With it running at full speed right outside my door I can't hear it inside over the air conditioner it is powering. I could put it farther away but there is no need.


Mind you, we're talking about portable generators here, not standby propane or natural gas generators. All responsible safety organizations recommend the 20' distance for portable generators. Mine has a 60 foot cord and is about 40 feet from my side door, on the far end of my garage. The exhaust is fan driven towards the rear of the property.


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## OrlyP (Oct 19, 2021)

I've got mine 3ft against the outer wall of the house and have CO detectors peppered along ingress points. None have tripped or even got as much as a whiff of CO.

I'm sure that we can all agree that 15-20' distance is not a bad idea. But I believe this is more of a guideline or PSA to the 'other' general public who thinks that running it inside a connected garage, kitchen, or living room is a good idea.

Just don't point the exhaust pipe at any windows or doors. Better if the generator is near a corner of your house so the exhaust gases are carried away no matter where the breeze is coming from.


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## OrlyP (Oct 19, 2021)

The moment I stepped into this forum, particularly this one (generators), I can immediately tell from the many posts that people here hold safety at a very high bar. I don't think anyone meant any offense dishing out safety suggestions. Sure, a lot of what people have said here (including my own contributions) could've been written better, but I'm absolutely sure none of them were designed to come out as condescending.

I'm sure everyone is aware that this is a public forum and that less-experienced generator owners often find themselves landing here after doing some initial Google searches... I know I did. We all interpret things differently and so, iit's not impossible to think that someone who isn't an expert may take your statement to heart (ie. running a propane generator in the living room) and consequently cause themselves harm. Nobody wants that on their hands. I guess people here just want to set the record straight and not leave things open to many interpretations.


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## Columbotrek (11 mo ago)

I saw a video on you tube from a man with a generator he aquired fitted with a car muffler. He ran it while measuring the sound with a DB meter. Then again after the car muffler was removed. The increase in sound was 2db.


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## OrlyP (Oct 19, 2021)

Columbotrek said:


> I saw a video on you tube from a man with a generator he aquired fitted with a car muffler. He ran it while measuring the sound with a DB meter. Then again after the car muffler was removed. The increase in sound was 2db.


Yup, seems about right. As stated, most of the noise you hear comes from the cylinder and crankcase.

Air-cooled engines have thin surfaces to better dissipate heat so there's not much in the way to dampen down the mechanical noise. On the other hand, liquid-cooled engines have 4x as many "walls" in the cylinder portion, so they're relatively quieter. Exhaust noise is but a small portion of the overall racket.


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## tabora (Sep 6, 2018)

OrlyP said:


> As stated, most of the noise you hear comes from the cylinder and crankcase.


Videos re: noise of PowerMate generator in enclosure with/without doors open...


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## OrlyP (Oct 19, 2021)

Nice!

Adding rockwool sheets or blocks on the inside surfaces of the shed will further reduce the noise down to almost a whisper. That's probably the only situation where exhaust noise starts to stand out.


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## tabora (Sep 6, 2018)

OrlyP said:


> Nice!
> 
> Adding rockwool sheets or blocks on the inside surfaces of the shed will further reduce the noise down to almost a whisper. That's probably the only situation where exhaust noise starts to stand out.


It's actually fairly quiet at the property lines... Can't even hear it inside our house with the windows closed. It's about the same volume as my neighbor's standby Generac.


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## OrlyP (Oct 19, 2021)

tabora said:


> It's actually fairly quiet at the property lines... Can't even hear it inside our house with the windows closed. It's about the same volume as my neighbor's standby Generac.


At least put some Rockwool or some other thermal insulator in the area where the muffler is. I worry that in the long term, it could melt the plastic just due to the proximity.

What's the peak temperature you get inside the shed?


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## tabora (Sep 6, 2018)

OrlyP said:


> At least put some Rockwool or some other thermal insulator in the area where the muffler is. I worry that in the long term, it could melt the plastic just due to the proximity.
> 
> What's the peak temperature you get inside the shed?


It has a thermal monitor inside the shed (and outside for the propane tank in the exhaust air flow in the winter). The internal alarm is set for 80F and has never gone off. It's moving a massive amount of air through there at 1,200CFM. The generator exhaust is pointed right at the exhaust fan blades. It's engineered to succeed; been running it like this since 2017.


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