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Old 18th June 2004
Lives for gear


I bought a diesel generator; 7.2 kw, 1 cyl, high (3k - not 1800 (I know)) rpm .

The generator's muffler is small and not effective against noise. I know the Forest Service requires spark arresting qualities in generator mufflers. I've read of 'critical' grade mufflers. A friend told about how quiet a 'movie' grade generator he had hired had been.

What should I look for in a muffler so I don't have to exile the generator too far away? Better yet leave it in the back of the step-van.

I think I'm OK as far as ideas for a shell for the noise. I can do some noise reduction with mounting and isolation. That will let me use the box to mop-up problem freqs. At least that's the theory.

Right now if I were a stage parent to my talented (120 & 240) new toy, I'd audition the noise-print of the generator for a modern (i.e. diesel) rendering of the African Queen's final charge - not the reassuringly ominous put-put of steam, but a determined little diesel giving its all for the big show. The sound I'm after is Eartha Kitt as Catwoman.

Oh well, the generator comes with a year's warrenty and an hours meter. The manual recommends a rebuild after 1,000 hours. The good news is that it claims a low-single-digit wave form distrortion figure. Will it work for recording? That remains to be seen, but at least I can edit on generator power and record powered by UPSs which can be recharged by the generator.

First, though, I need a muffler. Any audio friendly recommendations?
Old 18th June 2004
Gear Nut
Inky Goddess's Avatar

Exclamation my roommate is an automotive machinist & mechanic...

...and he said that 3k rpm for a diesel generator is gonna be really foikin' loud no matter what! he recommends going with the muffler the manufacturer recommends, and if that doesn't work...get a bigger one.

he did recommend something interesting, though...he said you want to remotely mount the muffler with flex pipe, preferably stainless. something about reducing vibrations and controlling dBs...some guy stuff like that. good luck!
Old 18th June 2004
Lives for gear

The flexible stainless-steel pipe with a remote muffler may be an option. Is your friend saying that just about any (bigger) muffler should do? How important is having a diesel-specific catalyst?
Old 19th June 2004
Gear Nut
Inky Goddess's Avatar

he says he doesn't think it matters, but you can check with a well-known muffler company or two, and the generator's manufacturer. another realm to check would be the high-end motor coach read "tour bus" manufacturers. they often use on-board diesel generators.

off with you then!
Old 23rd June 2004
Gear Nut
Inky Goddess's Avatar

so jab, whadjya find out?
Old 24th June 2004
Lives for gear

I found a cool site with "Critical-grade" and "super-critical-grade" mufflers although I'm not too clear as to whether those offer the advantages the same site touts for their diesel catalyst (one advantage being a lessening of diesel odors).

That's going to have to wait for a few weeks. It's getting close to tear-out-the-bulkhead and tear-down-the-ceiling in the step-van. Rivets, meet the angle-grinder :-)
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