Yanmar 2TNV70 Intake Pulse

[DRJensen]

I have my genset rigged with an air box from the same car I got the radiator/fan/over flow can. The intake air seems to be pulsing at the inlet of the filter box. This is also creating a droning sound that is louder than the exhaust. Do I need to run one of those round canister style intake filters found on heavy equipment to suppress this sound. I can hear it in the house over the exhaust or even the natural noise the engine makes. I read that the small 2 and 3 cylinder diesel have this pulsing intake but cannot find anything about how to suppress it. The other day we had a small track hoe onsite and it had a 3 cylinder yanmar for power and it was quite as a mouse even with the engine compartment door open. I need help as this is driving me crazy. 

[JLMTECH]

Hi, DR,
Your description of your engine intake vibrations sounds like vibrations from blowing into a
long neck beer bottle.

This is like a spring/mass system. the air in the neck has mass and the bottom of the
beer bottle acts like a spring. The mass of air in the neck bounces of off the compression
of the air in the bottom of the bottle. A resonant frequency of the intake is "matching in some
way" the engine RPM..

Two stroke engines use the phenomena in the exhaust expansion chambers to increase power.

Resolutions:
1. Add or subtract mass to the "neck" to change the resonant frequency.
2. Change the volume of the "bottom of the bottle" to change the resonant frequency.
3. Add damping by lining the air box with something like open cell foam.   

Other solutions:
4. Adding a second intake tube to change basic configuration to multi-mass resonator.
5. Running the engine at different RPM to remove frequency matching..
6. Adding some restriction to the intake opening to add damping.
7. Adding baffles to the "bottom of the bottle" to change dampen the spring effect.

1. maybe the easiest.Tests can be run by cutting open a soda bottle to make a tube and holding
it to the intake opening. A cone made from cardboard against the intake opening can also be
tried.
The number of ways to resolve the vibration problem is large. I hope you have fun. DRLarry

[pressurepro]

I run z602(2cyl) and d902 (3 cyl)kubotas on pressure washers..3600 rpm from the turn of the starter switch....I have removed the air filters with them running and the intake noise is deafening and is way louder than the exhaust and everything else running.....the air filter housing assemblies are donaldson type and are all plastic and quiets down the noise immensly...u hear the exhaust way more and the intake noise is almost non existant...ill get a part # for ya...should easy to order online...

[mobile_bob]

take a look at an intake resonator design such as was used on gm 5.7-6.5 liter diesels

they are very effective at abating the intake bark/pulse noise.

i was amazed at how well one of a 6.2 liter did at taming the s195 changfa intake noise.

bob g

[DRJensen]

Sweet, thanks for the replies. I actually had a neighbor complain yesterday about the noise. I moved the intake filter box outside the metal building over the weekend to allow cooler air to enter the engine. The neighbor came over and asked is that a generator you have running?? I said yes and asked him how long it had been bothering him and he said only a few days. I thought thats funny because it has been in service for more than a year. Now the intake is outside it echos over to the street behind me. Thanks pressurepro I will be looking for those part numbers and if those ar too expensive I will try to find a used air intake system from an old GM diesel pickup.

Maybe something like this!!! http://www.ebay.com/itm/YANMAR-AIR-CLEANER-ASSEMBLY-PART-129030-12501-NIB-GENUINE-PART-SEE-DETAILS-/350609500017?pt=BI_Heavy_Equipment_Parts&hash=item51a1f46771#ht_337wt_896

[glort]

One some new ( petrol) cars they have all sorts of weird and wonderful  closed offshoots from the air duct from the filter to the throttle body. Some even have a plenum after the arfilter box that's bigger than the airbox itself.  Apparently this is to stop droning and resonance at different engine speeds.

The problem must be substantial because some of the ones I see are very complicated and must add significant cost to the injuction system components as well as create some packaging issues with where all these seemingly useless appendages of the system go.

It has been suggested to me to fit a muffler to the inlet side of the engine to quiet the noise. If you engine has some back pressure or reverberation, I wonder if something like a set of  reed valves plumbed close to the inlet might help? They would certainly stop any blow back into the airbox and might even keep a positive pressure in the system between intake events. That could  help power as well as noise.

[pressurepro]

Donaldson GO42544....go to the donaldson site and check that out..there is lots of info and specs....probably get the whole thing online for bout 100 bucks and the air filters are super easy to find....just trying to help..