Adding a muffler to a cheap Generator

I used $19 muffler from advanced auto on my home made welder. It does help allot with the noise, but you will need to know how to weld to set one up. One thing to keep in mind is most of the inexpensive air cooled engines fire on every stroke. If you turn the engine off at full speed then you will fill the exhaust with a good mixture, if you start very soon after turning off, you will make the guy next to you look up a bit.

Ernie Leimkuhler wrote in news:120820031112545631% snipped-for-privacy@stagesmith.com:
You can probably get away with any muffler you want. That's got a 4- stroke engine. Most small engine/ tractor mufflers don't have any noise material packing though.
The last decent muffler on my 16 HP Techumseh powered welder, the can was about 12 inches long, by 5 inch diameter. It was an orig equipment off of a good garden type tractor. It had a bologna cut on the outlet (diagonal cut on the pipe). That might have helped it sound better too.

wayne wrote: (clip)It does help allot with the noise, but you will need to know how to weld to set one up (clip) ^^^^^^^^^^^^ Ernie, in case you feel you need help with the welding, don't hesitate to e-mail me. I've been welding for several months now. There may also be others in this group who have developed the kind of experience which you may find beneficial.

If you're only concerned about the noise bothering you, then the cheap and easy way is to get the generater behind something. Campers regularly put the generater behind a convienient bush, and throw and old blanket on the bush, this works pretty good. If you're concerned about the noise bothering others, or want a more elegant solution, then you can use just about any small to medium sized muffler available. As others said, just support it well so as to not to stress the pipe coming off the head. On a little engine like that you won't be adding an amount of backpressure that will harm the engine.
JTMcC.

Here is one supplier:

For quiet, I often find that a car muffler (and whatever adapter is needed to get the car muffler attached to the small engine exhaust) is more effective than many of the "small engine mufflers", which are simply too physically small to be very effective at quieting. I figure if it will let a 4-8 cylinder car engine breathe, it can't be overloading a one or two cylinder small engine with excessive restriction/backpressure. It's not a two-stroke, so there isn't much "tuning" of the exhaust going on.
You want to support the muffler so that the engine exhaust port is not carrying the weight of the muffler. Your standard Briggs & Strattion exhaust port is a standard pipe thread (or was the last time I fiddled with one), so plumbing your way from the exhaust port to the muffler is not too difficult.

What 2 stroke powered welders are you talkin' about?
Most (99.9%) of the engine powered (small air cooled) welders that I've been around were/are 4 strokes !! Are you saying they fire on every stroke?

So Ernie, any logic behind picking the Coleman? I'm looking at the Honda engine/someone else's generator units.
Steve Smith
Ernie Leimkuhler wrote:

Ernie's engine is a 4 stroke, but it does fire on both power and exhaust stroke. The smaller air cooled engines use the crank for timing. The problem is often the engines will fire (depending on valve/ignition timing Fire before TDC and the exhaust valve open till TDC) with the exhaust valve open some, if there is any fuel in the muffler it is going to ignite. Larger water cooled engines use the cam for ignition timing. The cam runs at half the RPMs of the crank, this will only fire on the power stroke. Now I realize many new engines are not fixed to the cam position but that means nothing here

OK... we're on the same track here.
Thanks Wayne!
BTW, I enjoyed viewing the spool gun you engineered! You've got more patience than I've got! :)
Wayne's spool gun:
I will say that when I put my home made spool gun

I have an old Wisconsin twin fed into a junked muffler found at a muffler shop. The volume indeed seems to do the trick. The inside of this old muffler is rotten but the outside is sound. It worked for this old Hobart. Now it is no louder than a residential lawn mower. Randy
$505 brand new, including tax, at Costco. So far my only complaint is the noise. Works great.
BTW I just picked up a length of flex exhaust hose and a muffler for a Geo Metro (it was the smallest muffler the parts place had).
I have to make up a mounting flange for the exhaust port on the engine and fab an elbow to get the exhaust pipe located right.

So I successfully mounted the new muffler last night. I bought a Geo-Metro muffler for $30 new and ended up using some pieces of fancy stainless flex tubing I had from school. I also welded up a custom stainless steel flange and short 90 deg elbow. One of my students last quarter works for a hose shop that makes up those fancy stainless steel flex hoses with the braid on the outside. I had several practice pieces of his and simply added them together.
It all worked very well.
The generator is still loud, but now it is more like a normal lawnmower.
When I shut it off I did get a substantial backfire from the muffler. Kind of startled me.

One used 1.5 KW generator that had sound proof housing made of plywood with rockwool insulation. It was so quiet couldn't hear it from 20 ft. We even shoot mopic with sound record without noise problems. For this to be practical must have electric start.
This crude drawing showes box layout looking at frount side. XXXXX X X X M X X X XXXXXXXXXXXXXXXXXXXXXXXXXX X X X X X X X X X X I X E and G X X X X X X X X X X XXXXXXXXXXXXXXXXXXXXXXXXXX
E = engine B&S I = intake compartment G = generator M = Muffler compartment There was 2 ea. 4" Dia. air intake grills on back side of air intake compartment.
The engines air intake/recoil starter was aginst rock wool insulation and bukhead for intake compartment so it could draw cooling air through hole. Carborator was on frount side so it could be accessed through door for E & G compartmet. Door was sheet metal with rock wool insulation
Muffler compartment was sheet metal with rockwool insulation. Exhaust left engine through flex tube through top of E&G compartment near back edge into M compartment. Muffler layed on rock wool. I never opened the muffler but it looked like glass lined pint paint can. The frount of E was open and located at about middle of top.
It used outboard fuel tank and had external oil tank.

With the engine having spark on the exhaust stroke it will be loader than an engine that uses the cam for timing. The other problem with the less expensive gens is that they don't have idle down, when you shut off the gen it is winding down form 3700 RPMs this loads the muffler with an air/gas mixture, that muffler is HOT so it will go bang. Its a big help in the noise department but does not pure like a new car. Most of those small mufflers just do a steady burn as the engine runs, your large muffler "stores?" alot more gas/air mixture. I always get a kick (not always) out of snow blowing in real cold weather in the dark of night and see the flames shooting out of my snow blower. When you shut them down if its dark out you can see the glow.

Yes the engine Ernie has is a four stroke, but it does fire on every stroke. The small air cooled engines timing is run off the crank not the cam. (The flywheel provides the power for the spark) That fires the engine on both the power stroke and the exhaust stroke. This can cause problems if any gas is in the muffler. Most larger water cooled engines fire only on the power stroke, they also use the battery to power the ignition. Most water cooled engines use the cam which runs at half the rpm of the crank. Now newer cars use more than the cam.

Wayne Makowicki wrote: Yes the engine Ernie has is a four stroke, but it does fire on every stroke.(clip) ^^^^^^^^^^^ I don't know whether this is still true, but I recall my Honda 4 cylinder fired the cylinders on pairs. One was on compression, and the other on exhaust. The plug on the exhaust side acted as a spark gap in series with the active plug, enabling partially fouled plugs to keep working. (A spark gap prevents the energy from bleeding off during the rise time of the voltage.) It also allowed the engine to get by with fewer ignition components.

Ernie, the tail pipe extensions for VW cars are actually small mufflers. I have successfully used them to reduce the noise on small engines. They are pretty cheap from JC Whitney, and probably available from your local auto parts store. You would need to make an adaptor to fit them to the engine, but shouldn't be a problem for you.. Good luck.. Jim

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I have the exact same unit. Good generator, powers most of my house in an emergency. That engine is *very * noisy though.
I went to the auto parts store and got a length of 2-1/2" stainless flex tube for exhaust use and an extension pipe to fit the flex tube. Welded the 4" long extension pipe over the outlet of the stock muffler and attached the pipe to it and any old muffler on the other end. This allows me to put the generator in the garage and exhaust it outside. The exhaust is now fairly quiet but the engine block is the loud part now. Seems to be valve noise from the solid tappets.
The engine also wear was more than expected. We were without power for one 24 hour period and ran from the generator. Luckily I had my speedboat trailered in the driveway with 30 gallons of gas in it. I had to add oil to the generator several times when the low oil switch kicked in. The temperature was in the 90's and with the garage door almost closed, must have been 110 deg in there. Engine still runs well but is getting even noisier. All things considered, next generator is going to be an overhead valve with pump lubrication (not just splash lube).
Still, 5KW is a good power level to have. Darn handy to run the MIG from too. Far more consistent welds than running from the poor electric in the garage.
Oppie

You are going to get one hell of a lot of vibration from that unit so plan accordingly. Another issue is that it doesn't have an auto throttle or at least the rig that they use is quite poor. I would be very hesitant about running anything drawing a lot of start up current or intermittant use from it or you might just burn out whatever you have running. I found this out the hard way during the ice storm of 98 in NY when an identical unit I had running backfeeding the house via my welding circuit seized the gun on my furnace which spiked and cooked everything in my house that was plugged in and had transistors. No it wasn't a case of overload just that the machine couldn't catch up with the requirements that I had been happily meeting for days with a 3250 watt Sears( Generac) with the ohv engine. It simply welded the brush to the motor on the furnace and dead shorted the system, caused a small fire in a GFI as well. I had a hell of a time starting the thing to boot, lifting all 200+ lbs of it off the floor to get it running. If I was going to use it with a welder I would keep that idle cranked WAY up so you don't suffer something similar' lights and small draw appliances don't seem to matter. I never had one hesitation from the little Generac and I still have it today running as good as the day we got it. I don't mean to rain on your parade but merely reflect on my personal experience with an identical unit. I guess thats the difference between a $400 Coleman and $900 Generac and this is one of those cases where its justified for those who can afford it. If I was going to muffler that rig, and it is VERY loud I would take into account for all that vibration and the way it wanders about when running on a concrete floor.