So yeah, I'm running off a generator for a few days and I have a bunch of spare parts around.
Why do these things have to be so bloody loud, and how bad would it be to just stuff a Miata muffler on it?
So yeah, I'm running off a generator for a few days and I have a bunch of spare parts around.
Why do these things have to be so bloody loud, and how bad would it be to just stuff a Miata muffler on it?
Some of the noise could be intake.
Dad got one of the predator ones at harbor freight. Encased in red plastic cowling.
Damn thing is almost silent.
But, added muffling shouldn't hurt it as long as it doesn't restrict cooling
iceracer said:Some of the noise could be intake.
I would guess about 40% is intake trying to roughly separate the "woosh" from the "putter" by volume... I could be completely wrong, of course.. but it's easier to muffle an exhaust than an intake, I think... Maybe not?
A muffler will help, but tons and tons of generator noise is from the machine itself. Enclosing it in a box, like the quiet generators, will probably do as much good as a muffler.
Dusterbd13-michael (Forum Supporter) said:Dad got one of the predator ones at harbor freight. Encased in red plastic cowling.
Damn thing is almost silent.
But, added muffling shouldn't hurt it as long as it doesn't restrict cooling
Yeah, those things are amazing Honda knock offs. Everyone at the track has those now :) Unfortunately, they can't run a well pump (HF ones are 120V only), and I can't afford the real Honda one that can!
This one is a 6500W Ryobi.
Good call, Tom. I'd love to build a box to house it, but I don't know that it's worth that effort for as rare as needing it this long is.
This is mostly out of frustration at hour 10 :)
Tom Suddard said:A muffler will help, but tons and tons of generator noise is from the machine itself. Enclosing it in a box, like the quiet generators, will probably do as much good as a muffler.
This. I just shut ours down after three days, frigging thing will wake the dead but it runs the entire house less the AC. Search this, a bunch of guys have done extensive videos on what it takes to shut a low tech generator up. I never seem to get around to it, for the few times we need it I’ll deal with the noise.
In reply to 11GTCS :
That's what I was afraid of, given we've made it 8 years in this house without one (a few times got dicey!), so any effort towards it will likely exceed my time ratio.
Ah well, it's a fun thought exercise..
11GTCS said:Tom Suddard said:A muffler will help, but tons and tons of generator noise is from the machine itself. Enclosing it in a box, like the quiet generators, will probably do as much good as a muffler.
This. I just shut ours down after three days, frigging thing will wake the dead but it runs the entire house less the AC. Search this, a bunch of guys have done extensive videos on what it takes to shut a low tech generator up. I never seem to get around to it, for the few times we need it I’ll deal with the noise.
I know I'll never find the time to make this a priority, but I know I should. I have a 15-year old Coleman with an 11(?) HP Tecumseh engine that screams bloody murder. The electricity-producing thing howls and screeches also. It's hard to imagine a louder, more annoying gasoline-powered device. Fortunately, I only need to use it once every three or four years, and when I have no electricity, it sounds like the sweetest music. Well, at least for the first hour or so. 
In reply to WonkoTheSane (Forum Supporter) :
Realistically you can case 3 sides, and maybe the top, to redirect the sound away from the house and get a pretty good effect.
Neighbors night not totally appreciate it if they're close though.
That's basically how hush houses work for turbine engines.
1988RedT2 said:11GTCS said:Tom Suddard said:A muffler will help, but tons and tons of generator noise is from the machine itself. Enclosing it in a box, like the quiet generators, will probably do as much good as a muffler.
This. I just shut ours down after three days, frigging thing will wake the dead but it runs the entire house less the AC. Search this, a bunch of guys have done extensive videos on what it takes to shut a low tech generator up. I never seem to get around to it, for the few times we need it I’ll deal with the noise.
I know I'll never find the time to make this a priority, but I know I should. I have a 15-year old Coleman with an 11(?) HP Tecumseh engine that screams bloody murder. The electricity-producing thing howls and screeches also. It's hard to imagine a louder, more annoying gasoline-powered device. Fortunately, I only need to use it once every three or four years, and when I have no electricity, it sounds like the sweetest music. Well, at least for the first hour or so.
Mine is a 10 HP Briggs driving a 5,000 W generator head. The muffler is 1” MPT and is basically a strainer to keep engine parts from exiting the block in the event of an internal event. It glows cherry red in the dark. It’s obscenely loud, like you can hear it 4 houses away loud. I try to shut down by 10:00 PM in deference to the neighbors. That said the utility transformer outside our house failed at about 2:00 AM on a subzero night about 20 years ago.
It was 40 F inside by 4:30. Pulled the monster out, filled it with gas, checked the oil and gave it a pull. Frigging thing started on the first pull at -2F! Fumbled around in the dark to grab the governor linkage to slow it to idle and let it warm up for a while so the oil wasn’t like glue. Saved the house from freezing up, I should have written a letter to Briggs & Stratton. It’s great to have when you need it.
We tried that idea. We have a 7500w at camp in an outside shed thing. Basically a large, outdoor closet on the patio. We rigged it up with a louvered panel for air inlet and routed the exhaust outside through a piece of terra cotta drain pipe. The only thing it does is vent the exhaust outside the closet. It doesn't help noise AT ALL. You are hearing the rattling of all the steel, the thrashing of combustion, a rod and piston, friction, the whirring of the genny.... the exhaust is one of the least offensive parts of the noise a generator makes. Inside, the noise is unbearable, but if you go outside, you hear this tiny little exhaust noise. If you separate the exhaust from the generator noise, I think you'll find that the exhaust is only a tiny portion of the overall noise it makes.
They have to be noisy. The engines are designed to make the most torque they can in the smallest, lightest package, so that means noise. It means 3600 rpms and a lightweight, non-hyrdraulic valvetrain. It also means exposing as much of the engine as possible for cooling. You get to hear it all. You could probably get the same torque and wattage from a three-pole genny and 1800 rpms, but to have an engine with enough torque at that RPM, which means it would likely weigh three times as much. You can shroud it with all kinds of sound control, but then you're asking for heat issues. If Honda or HF can spend the time and develop shrouds that don't hurt cooling on their smaller gennies, that's one thing, but randomly adding shrouding to a generator can be a very bad thing.
You can call up Generac and get a 15k Genny that is super quiet (like for RVs), but it will cost you around $7000.
In reply to Curtis73 (Forum Supporter) :
Thanks for validating my laziness! Winning! 
I always applaud laziness. Or as I call it, "engineered simplicity"
After the mice killed our diesel Sparky that was just out in a shed,I put the Lowe's Special in a box just to keep that from happening again...
Biggest part of the noise is from air cooling. The fins all "ring". Liquid cooling would add a lot of weight though, so not so portable.
Generators are pretty much loud once you get outside the suitcase ones.
Build a three sided box to deflect the noise one way is the best option
I always wanted to build a generator from an old ACVW engine. Those were quieter than most anything out there.
Did you try the miata muffler? I'd at least give it a shot.
Not a generator, but I know Honda lawnmowers tend to get significantly louder as their mufflers wear out. Slap a new one on and the quiet down a LOT.
That said, a 3 sided box (or 4 with open top?) seems like a fairly simple option if you have some scrap wood around.
If you have lots of space and no HOA, one option for a quiet (and fuel efficient!) generator is to get a crashed-but-running Prius. Pick up a high-power UPS with dead batteries (these are often cheap), hook the inverter to the Prius battery, and leave the "ignition" in the car on. You run your AC loads off the inverter and the Prius electronics will start the motor to fill up the battery as necessary.
In reply to codrus (Forum Supporter) :
Dang, that's a great idea. If it no longer needs to be mobile I wonder how small you could make the necessary parts of a Prius. Getting rid of wheels, most of the body, etc.
No, I didn't get to try the Miata muffler.. I've been too busy keeping the freezer, fridge, well pump, etc. Running to take it offline to run the welder. And this thread didn't give me a ton of confidence to prioritize it :)
I like that Prius idea, Codrus!
While there's plenty of mechanical and intake noise from a little aircooled 4 stroke there's still enough exhaust noise that you can make a difference.
I was given a free 12 HP B&S Craftsman riding mower, the muffler rusted off, holy cacophony of ear splitting noise, so obviously the muffler does muffle the sound quit a bit.
I replaced it with a small ~12" long "motorcycle" muffler I got from Jegs (I think) and a 90° elbow in an effort to not only replace the muffler, but also direct the exhaust downward, and less in my face on every left turn. The motorcycle muffler did little for the sound, as it was a straight through design with a perforated inner sleeve. Still loud enough that I mowed the yard with my shooting muffs on.
I got sick of that, and built my own muffler, I welded two steel vegetable cans together, end-to-end, made some baffles from their lids, and stuffed the thing with stainless steel wool. It wasn't pretty but did a great job of cutting down the noise.
The thing wasn't silent by any means, or near as quiet as the inverter generators mentioned several times, but my cobbled together, custom muffler did make a difference.
I wonder if some sort of large muffler combined with piping the exhaust into a bucket of water (the latter seems a common suggestion) would minimize the exhaust component of the noise. That plus rubber isolation under the unit and external shielding (I've seen some sites that suggest a box with MLV and other sorts of insulation) is probably what I'll try when I have to set up a new one in a couple of months. Possibly also an intake silencer of some sort, and if the box is closed, a fan to aid ventilation.
mad_machine (Forum Supporter) said:I always wanted to build a generator from an old ACVW engine. Those were quieter than most anything out there.
Tweedle tweedle tweedle.
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