Generator intake noise

[TomC]

I have a 10kw Powertech generator powered by a 4 cylinder 1200 series Kubota Diesel engine.  While I've been successful at being able to keep the generator quiet with lead lining and such, the one fly in ointment has been in intake air noise. 

This is what I've done.  Since the gen compartment is tight, I mounted the air cleaner under the driver's seat (I have a transit where the gen sits next to the driver's seat like a front engine-the gen is accessed from inside).  I reused the rectangular intake baffle box (plastic box about 10" long by 3" square that has openings on each end for the intake hose and 4 baffles inside) and purchased an exhaust muffler that Dick Wright uses for intake noise reduction.  So the intake air, starting at the intake muffler is mounted under the front entrance steps on the right side, goes through the muffler, then around the back of the gen compartment to the air cleaner under the driver's seat then into the gen compartment through the baffle box into the engine.  It still puts out that open carburetor howling sound.  Does anyone have a suggestion to quiet it further? I was thinking maybe of routing it into the gen compartment again so the air comes out of the gen compartment-maybe quieting it further?  Let me know.  Good Luck, TomC

[boogiethecat]

Yeah, those little diesels often make more noise from the intake than the exhaust!  My genset trailer with a 4 cyl Kubota is the same way.  When I got the engine first started, I was surprised that without a muffler it was MUCH quieter than with a muffler but no intake filter.
I ended up putting two pretty big Donaldson (metal) air filters in series, and then positioning the intake inside the quiet box as well, that solved it.

If you have room and the inclination, you can also just  make a "silencer box" specifically for the intake, with a few turns, lined with foam sound absorber... sound won't go around a corner well.

[Hartley]

On my Onan/4-cyl Kubota setup, I installed a kubota tractor round type cannister air cleaner.
I then took the weather cap off the air intake and put a 1 inch  silicone hose and 90 degree
elbo that turns the air intake down towards the base of the generator.

That pretty much eliminated the intake noise.

The trick is to make 90 degree turns to trap the noise inside the intake pipe.

Using a rubber hose such as silicone ones helps take the resonance out of the
intake.