exhaust volume

decibles?

...pah you think YOU have problems - I'm trying to lose 25 dBA from

100KVA generator driven by a Ford 6 cylinder 6 litre turbo engine (2704ET) that currently is giving 90 dBA at one metre !!!!!!!

AWEM

I remember a neighbor who built a two seater gocart using a small B&S motor. He connected the motor it to a full size car muffler using flexible metal exhaust tubing. It was so quiet you could not hear it running.

I have a car muffler attached to my old Yamaha 3-wheeler. The car muffler is about 6 inches in diameter and 18 inches long. The openings are for 2" exhaust pipe. I got an elbow made a reducer, also made some hangers/brackets. and attached it at right angle to the muffler on the three wheeler. Now the loudest thing you hear is the knobby tires in the leaves/dirt or the gears of the transmission. by going slow in 2d gear about

10mph, I can sneak up on the hounds in the dog kennel we have in the woods. They don't know I am coming to feed them until one of them sees me usual when I am within 50 feet or so. If I take a pickup or tractor they start barking when I am a couple of hundred yards away, even though they can't see me coming.

I don't have any idea what type or size car this muffler came off or but any inexpensive car muffler should do the trick. I would suggest leaving as much of the original exhaust system on the Gen/Welder as possible. The large passages in a car muffler shouldn't cause any noticeable power loss due to restriction.

the same recommendation back to back......sounds like its worth trying to me. thanks guys, ill pick up an automotive muffler and try it out on my bobcat. if it makes any noticeable difference ill consider it a distinct possibility for the 145DX. anybody know if there are manometer ports on the

145DX intake?

thanks,

The problem as I see it is not so much exhaust noise as engine noise. Also both examples are given for slow RPM engines. Neither of the examples probably was running at a constant 3600 RPM. Makes a lot of difference. All of the very quiet generators (except for the supershielded Hondas) were running at 1800 RPM.

It's worth a try but I think you will then discover how noisy the engine is.

I don't think a Yamaha 250cc engine is classified by anyone as slow RPM engine. It's red-lined at 8800rpm and at 10 mph in 2 gear it is at 3500 rpm. The transmission is louder than the engine. But that is just my experience, and I guess real experience doesn't count for anything when it differs from someone's uninformed opinion!

Da, Tovarisch!

The primary source of sound from the generator in my RV comes from the machinery itself - you can barely hear the exhaust.

The generator is an Onan CME7000 and is equipped with an automotive-type muffler that's approximately 4" diameter x 14" long.

The amount of heat produced by the engine while running has to go somewhere and *that* limits the design of the enclosure in respect to sound abatement. So far, the best idea presented is the use of fine louvers to create a "dogleg" [ / \ / \ ] path for the airflow so as to block direct-path sound radiation. As initially installed, there's just a grillwork of expanded metal to provide airflow.

examples

difference.

automotive-type

direct-path sound

expanded

On my 100KVA generator the air from the radiator passes through a grille made of 9 "inverted chevrons" so the air first goes up at 45 degrees then back down again. Each chevron is made from a sandwich of perforated galvanised steel with high density glass fibre between and ends up 20mm (3/4") thick with each leg of the chevron being 100mm (4") It's pretty ancient and the rain has soaked into the glass fibre and rotted out the perforated metal. I've made up a new set and when I fit them I am also going to fit a rain hood to stop it re-curring !

AWEM

You can actually get engine compartment sound deadening material. It is a very heavy foam material with foil one side. Many marine equipment suppliers have it although another industrial source might be cheaper. I used some in a marine engine compartment and even though it was not completely enclosed it did reduce noise significantly. The stuff is VERY expensive. The old traditional method was to line the compartment with lead sheet. If you have an opportunity to see the gen sets used on movie sets it is pretty impressive. It is hard to know if they are running or not once you are ten feet away and can't see the dials. Randy

...pah you think YOU have problems - I'm trying to lose 25 dBA from

100KVA generator driven by a Ford 6 cylinder 6 litre turbo engine (2704ET) that currently is giving 90 dBA at one metre !!!!!!!

AWEM

message

cheaper. I

Randy,

It's encouraging to hear that you've had good experience with this stuff as I'm about to sink about £350 in lining the case with it. I'm also thinking of making a lead sheet jacket for the engine itself. The main problem that I have is this thing is mobile - it has a pair of axles so it can be towed, and the 'underneath' is open to the road. Due to the construction it's not easy to seal it off and anyway I would still need to leave a largish opening for cooling air.

AWEM