Quieting a Miller Bobcat 225

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This may seem like a useless question, but has anyone tried to mate a muffler to the exhaust pipe of a generator/welder to quiet it down a bit.  I live in a neighborhood with houses that are fairly close together.  I have a good relationship with my neighbors, and I'd like to preserve that as much as possible.  When welding at home, it would be great to be able to keep the 16hp Onan as quiet as I reasonably can.  I have a buddy that owns a muffler shop that can get me a small stainless muffler and catalytic converter for peanuts.  I was thinking about welding an inline 1.75 inlet/outlet cat to a 1.75 inlet/outlet chambered muffler and having it lay horizontally exiting toward the engine side.  Weld a stainless mandrel 1.75 90 degree elbow(free to me) to the cat end and exhaust band clamp it to the newly shortened original exhaust pipe.  The band clamp would make it very easy to remove if needed.  It would also allow me to put the original exhaust tip right back on if for some reason it didn't work well.  The cfm flow capacity of both the cat and muffler would be considerably more than the 16hp Onan could produce.  I would imagine it wouldn't pose any sort of restriction to the engine.  I'm considering doing this to a 1999 Miller bobcat 225 so voiding any warrantee won't be an issue.  Any reason why it wouldn't be a worthwhile experiment?  Thanks,George
Reply:What would the cat do?1.75 sounds big; too big and you loose the muffler effect.I wonder if an Onan motor-home generator exhaust system would be worth a look?
Reply:this will probably sound pretty stupid, but what about making your own muffler? similar to a glass-pack, but with a bit more restriction. basically take a tube, drill a bunch of holes in it, wrap it with fiberglass muffler packing material, and put another pipe over that. throw some end-caps to keep the outer sleeve in place and you have a homemade muffler. i have no experience working with small engine mufflers, so i have to relate it all to car/truck exhuast systems, but i have to agree with denrep... the 1.75 sounds a little big (if your generator's exhaust is as small as i think it is) and would kinda defeat the purpose. that large of a tube sounds like it'd be more of a reverb-chamber than an exhaust route. how big is the exhaust pipe that is already on your Bobcat? i would stick to that size, maybe up to 1/4" bigger dependant upon the length of our intended pipe, total restriction from muffler, etc. as far as the Cat goes, what is your reasoning behind it? the generator engine should already have all the emissions-compliant equpiment pre-engineered and installed on the engine from the factory. it sounds like it'd just be a waste of time, space, and money. stick with the muffler and the pipe.just my 2 cents.Later,Andy
Reply:Well in general a catalytic converter also acts as a small muffler in itself making the system quieter than without one.  The other benefit is that for about an extra 10 bucks it would score me bonus point with my green friendly better half!  It should also clean up the emissions(exhaust odor) a bit so when who ever is downwind of the running generator (myself or neighbors) it won't be as objectionable.  Or maybe because I seem to enjoy making things more complicated than necessary.  I'll ask my imaginary shrink tomorrow!     We all have strange reasons for doing things sometimes.George
Reply:Done it!Had an old muffler off of an old onan generator that plugged right in place of the stock end piece. quiets it down alot. I put the muffler on with the engine running, so I really noticed a big differece when it sealed. Other people that did not witness this event still heard the same old noise. I did not build a bracket to hold it so it kinda cracked the muffler where it attatched.  Sooo I took it off and put the 90* elbow piece back on. I can live with a little louder welder while I am working for now to avoid breaking the whole thing off! I don't really use that thing everyday so whatever.Build a sturdy bracket to hold it and VOILALast edited by Mark...; 12-26-2007 at 10:17 PM.
Reply:I'll have to measure but I think the exhaust pipe is about 1.5"  That is why I was looking at going up a 1/4" to the 1.75" muffler.  I suppose the cat wouldn't be very useful.  I think I'll scratch that idea. I Wasn't thinking about Onans factory emmisions gear.  I thought about making a muffler, but after finding out how many 1.75 inlet/outlet stainless chambered mufflers there are out there for the small car crowd (I can pick one up for 20 bucks or less and some of them are QUIET).  I could easily run 1.5" stainless tubing into these mufflers as well.  Just trying to reduce the noise a bit.  I have heard Onan RV generators running with an RV exhaust and they are very quiet even with the access door wide open.  Impressive really.  As suggested above, I should do some research on what they use for RVs.  It would be great if it was that simple.  George