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Old 10-04-2017, 09:23 PM   #1
seasalt007's Avatar
City: Punta Gorda, FL
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Generator with No Air Filter

I was surprised to learn that many generators do not have an air filter. My Onan 11.5 is one of them. It has something that could be mistaken for a filter but it is an intake resonator.

I had a minor exhaust leak on the main engine that eventually clogged it's Air Sep so I figured I would clean the generator's air filter. Several calls went to Cummins dealers who had no clue where it was and didn't mention the resonator. Finally one Ft. Lauderdale dealer said that many do not have an air filter and that the suspicious black box in my picture was a resonator on the air intake.

Who knew??
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Old 10-04-2017, 09:35 PM   #2
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Many marine diesels don't filter air because it is assumed they operate in clean air. Some items that appear to be air cleaners are filled with sound absorbing material. The intake makes more noise than a gas engine because it's always wide open. No throttle plate.

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Old 10-05-2017, 07:22 PM   #3
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My NL generator has an air box with something "like" a filter, but it is so coarse all it would stop are tools and loose nuts and bolts. The "filters" on my Lehman 135's are about the same and they have no problem running many thousands of hours. Guess there just isn't much dirt to ingest.

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Old 10-05-2017, 07:38 PM   #4
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If you go through the Suez canal in a dust storm, get a filter. And yep, most gennies just have a silencer. Some mains are similar.
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Old 10-05-2017, 08:05 PM   #5
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No air filter on Westerbekes. My Perkins main engine does not have one either. Just a flame arrestor screen to keep the flamer pre-heater in check. My flamer is disconnected.
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Old 10-05-2017, 08:11 PM   #6
City: Northport
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I added a K & N filter to each of our past Westerbeke gensets at the end of that resonator - quite easy as that resonator has a round outlet similar to a throttle body outlet. Many years back I added a K & N filter to my Perkins 165 and a Lister Petter genset engine as well.
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Old 10-07-2017, 03:23 AM   #7
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Ours never had one, just a big hole sucking in air.
Got one of these thinking it was 100% better than nothing and only $5

Not the exact size I got but various other sizes available for the same $
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Old 10-07-2017, 06:22 AM   #8
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City: Freeport Tx
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My didn't have one just got a kn filter cleaned it once a yr
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Old 10-07-2017, 07:49 AM   #9
City: Carefree, Arizona
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A foam air filter is quite common on gensets with appropriate cleaning instructions in the manuals.
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Old 12-16-2017, 04:52 PM   #10
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I use a K&N # RU-0210 air filter on my 8kW Onan. Fits perfectly.
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Old 12-17-2017, 02:28 PM   #11
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My 1988 Onan 8KW does not have an air filter on it. Why not? Is there a reason Onan/Kubota does not have intake filters. Does adding one affect performance?

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