Will a Car Muffler Make a Generator Quiet?

Recently picked up this generator which had a car muffler installed. I tested the sound output in decibels with the car exhaust and the stock OEM muffler. Does a car muffler make a generator quieter?

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Generator Model# 030230.00
Engine Model# 204412-0147-E1

[victorkrivor]

I’ve done something similar to this, but you MUST use a motorcycle muffler instead of a car, especially for single cylinder engines, because they’re designed for the constant 100-0-100 pulses of the exhaust, instead of the continuous gas flow from a multi-cylinder car. I personally used a stock Honda grom muffler and it was VERY quiet, and they’re not too expensive. Just make sure you don’t have a hole in the system 😊

[Mike_Neukam]

If anyone wants to mount an automotive muffler to a generator, it needs to be supported by the engine/alternator assembly, not the generator frame. Everything attached to the engine needs to be able to move as one unit because the engine and alternator are mounted on rubber isolators. If you don't, either the muffler bolts will vibrate loose, or something will break. Maybe both.

[wesjohnston]

Something to note about sound: the decibel measurement system is a logarithmic system, meaning, it isn’t a linear system (like inches or liters).
What this means is: for every 3 decibels increase, sound pressure (or perceived volume) DOUBLES. So a 6 decibel increase in your measurement means that the sound pressure has increased 4 times.

[rolsta]

Just a little tip. If you decide to use steel water pipe screwed into the block to mount a muffled remember the pipe is a lot thicker and won't disperse the heat and can burn out the exhaust valve. It has happened.

[williamterry]

Try a sheet of plywood leaned against the generator to see if you can reflect the sound towards your neighbors and lower the level at your meter.

[dwightmcclusky]

Imagine welding up a muffler on a generator just to have the guy you sell it to make a video of him removing it

[buckmurdock]

The engine manufacturer usually makes a "quiet" generator muffler that doesn't always come standard on store bought generators (I know, I was shocked too). That's usually the best option to reduce generator exhaust noise over all the homebrew methods. It will never be whisper quiet because much of the noise from a small air cooled engine is not from the exhaust.

[Name-psfx]

As soon as I saw that exhaust leak, I knew it wouldn’t be an accurate measure of noise...and then you changed out the _entire_ stock muffler which did not have the original leak, that ended the entire shebang for me. (Fwiw, a small rough piece of wood held by hand will do _nothing_ for noise abatement).

[MadScienceHacksTV]

A large amount of the noise is actually mechanical.

[matthewmillar]

Hole in the exhaust when you're testing volume? Sorry man, huge source of error there.

[scottdebruyn]

You do realize that every increase of 3db is a doubling of sound pressure, right? (logarithmic, not linear) So, 5db is 3.16 times louder! (6db would be 4x, 9db would be 8x, 12db = 16x... Car muffler was doing a lot, actually. :(

[adolforosado]

I saw one running in southern Mexico once with a motorcycle muffler and it's the quietest generator I've come in contact with.

[azurplex]

I agree that a motorcycle type muffler would be a better mod.
But actually the loudest noise of a portable genset is vibrating metal. Add more isolation to the mounts and the noise can drop a LOT. Enclose it with baffles while directing air and exhaust flow and you’ll make it practically disappear.

[StevenSmith-jtyg]

From some of my experimenting with portable generators. I found a great deal of noise came from the induction side. That mechanical sound of the valve opening and slamming shut makes a hell of a racket.

[FNPetersen]

Granted whoever did that conversion did it poorly, a couple points: whole test is invalid because you ran the test with car exhaust with a hole upstream of the muffler (sorry, your block of wood wasn't doing anything) as well as a loose muffler bolt. Both conditions were repaired for the stock system test. Even with that severe handicap, since the decibel scale is logarithmic, the stock system was FIVE TIMES as loud as the system with car exhaust. Done with proper rubber isolation, a good drain, and considerations for heat, that system could probably perform far better than it did here. I think we could expect a functioning system to achieve levels of 10 db quieter, or reducing perceived sound by 90%. I'd call that worth it.

[AnonyMous-jflc]

The 3 dB rule, look it up if you don’t know it. That muffler did quite a bit of noise reduction.

[calm]

Fix the hole properly, support the muffler with a rubber mount, have the exhaust blow outwards, not down, and correct that loose mounting clamp, then test.

[fisqual]

I've grinded and welded literally millimeters from a fuel tank, watching you remove the fuel tank for working on this gave me a good chuckle.

[audvidgeek]

One factor that needs to come into play here is how loud the generator is with a load placed on it. The generator is going to be burning more fuel per engine cycle to maintain 3600RPM with a few thousand watts on it. This, in turn will make more explosive energy in the exhaust system, which creates the noise. It would be good to run this test again with maybe two 1500-watt space heaters plugged into the generator for a simulated load. The automobile exhaust muffler, I imagine will really show an improvement, as it's designed to be more effective with higher exhaust pressures.

[juansolo]

Add an inline exhaust resonator pre-muffler. The standalone resonators will give it a deeper tone but they work WONDERS for quieting down an engine without a full cat.