Air box to reduce noise on my 4108?

[pcatterall]

If you want to strangle your engine go ahead, if you want quiet ride get some earplugs, remember these engines require AIR to run, they get lots when running on a road but not a lot when stuck in a slow moving ill ventilated box.

This doesn’t have to be the case. I don’t think most vehicles rely on the under bonnet air being FORCED into the engine. As long as there is plenty of air AVAILABLE then an air box which works on an engine in, say , a land rover should work ok on the same engine in a well ventillated engine room ??

 

[nigelmercier]

Watching with interest. I guess that filters depend on engine size.

I have an MD22P-B, 2 litre. What capacity is a 4108?

 

[duncanmack]

Watching with interest. I guess that filters depend on engine size.

I have an MD22P-B, 2 litre. What capacity is a 4108?

108 cubic inches. 1760cc

 

[geem]

No, I wasn't, just contributing to the thread, sorry if it appeared that way. Personally I think time an effort spent on quality sound insulation and a dedicated engine box would be more beneficial than an air filter at reducing noise. An earlier poster suggested an 8 to 10 decibel noise reduction due to fitting an air filter, thats the equivalent of a watch ticking, not worth it at all.

This is not correct. 3 decibel is effectively halving the sound. 8 to 10 decibel is significant

 

[pcatterall]

Looking at the size of boxes which would suit it seems I would struggle to just mount on the existing pipe. I will have to consider some kind of bracket mounted on the engine and then probably a reducing rubber connection and also the breather pipe.
I guess I could just make a temporary fix to see what noise reduction occurs ( using my decible app of course!!)

 

[Deleted member 36384]

This is not correct. 3 decibel is effectively halving the sound. 8 to 10 decibel is significant

I now understand that I was wrong but you are not going to half the noise of the engine by fitting an air box otherwise every engine on a leisure boat would have one fitted if it was that easy.

 

[pcatterall]

I now understand that I was wrong but you are not going to half the noise of the engine by fitting an air box otherwise every engine on a leisure boat would have one fitted if it was that easy.

Some tangible results have been published indicating that an air box can have a significant effect and I want to see if I can acheive something similar.

On a rather different subject I bench test eberspachers and can considerably reduce overall noise by fitting a very basic sort of noise muffler on the air intake.

 

[nimbusgb]

Take the air filter box off your car and run it for a few minutes. You'd be surprised at the difference it makes sound wise!

A large capacity baffled box with perhaps a foam inner and outer lining would make a significant difference I'm sure. My 4-108 has a little mushroom intake protector on it, not sure it's a filter at all. I'd be tempted to try this just for fun. I have a dB meter knocking around somewhere.

 

[geem]

my Perkins M92B has a factory fitted air intake filter. It has a pre filter and main filter. There is also a pressure sensor that pops up should the filter become dirty. It does this at surprisingly regular intervals. I think it is a myth that a yacht engine room is a nice clean place. Dust is present from numerous sources so they do clog filters. The filter arrangement on my engine has a filter inside a filter. This looks like a fairly high air resistance item but obviously taken into account by the manufacturers. The engine is remarkably quite on the induction side due to this filter arrangement.

 

[gandy]

I now understand that I was wrong but you are not going to half the noise of the engine by fitting an air box otherwise every engine on a leisure boat would have one fitted if it was that easy.

Remember that 3dB is half the noise energy, not half the perceived volume. Our hearing isn't linear either, which is why the dB scale is used. To the hearer a 3dB change would be an audible difference, so you could consider 10dB as turning down the volume by three steps.

 

[ianj99]

Some tangible results have been published indicating that an air box can have a significant effect and I want to see if I can acheive something similar.

On a rather different subject I bench test eberspachers and can considerably reduce overall noise by fitting a very basic sort of noise muffler on the air intake.

My results on the Marine Power engine which I published in the thread are still impressive after 3 months of use. The sound level in the wheelhouse is the same as an average car at 70 - ie unobtrusive and simply not noticed at all.

http://www.ybw.com/forums/showthrea...ith-a-Marine-Power-Chinese-46bhp-diesel/page4

I deliberately chose to use a sound level meter in the wheelhouse to prove to myself and others that the airbox works, rather than anyone having to take my word for it.
Its complete nonsense of course to say it will starve the engine, my engine still achieves its full rpm when motoring with the same smoke free exhaust. Also, the noise level does not increase with noise as much.

I'd recommend getting a generous sized airfilter housing, mine was from a Ford Ranger 2.5tdi of 3 times the power. (its the bhp rather than engine capacity that matters since a given bhp requires the same mass of air regardless of engine size)

Until you've tried one you'll never know what you are missing.....

You could also fit a smaller one on an eber or Webasto.

Ian

 

[gandy]

I'd recommend getting a generous sized airfilter housing, mine was from a Ford Ranger 2.5tdi of 3 times the power. (its the bhp rather than engine capacity that matters since a given bhp requires the same mass of air regardless of engine size)

Hi,

I was looking at that part on Ebay. Is the connection to the engine manifold just a cylindrical stub, so it can be connected with flexible hose?

 

[ianj99]

Hi,

I was looking at that part on Ebay. Is the connection to the engine manifold just a cylindrical stub, so it can be connected with flexible hose?

Yes, its 76mm if my memory serves me, so I used a 76 to 60 silicon hose reducer from another ebay seller. I remotely mounted the airbox under the cockpit where there is space, using more hose and a 45deg elbow so its about 700mm from the engine.
Ian

 

[gandy]

Yes, its 76mm if my memory serves me, so I used a 76 to 60 silicon hose reducer from another ebay seller. I remotely mounted the airbox under the cockpit where there is space, using more hose and a 45deg elbow so its about 700mm from the engine.
Ian

Brilliant, thanks. That's what I'll do, the existing air filter assembly on our Beta is a bit rickety so fitting something like you describe would be perfect. I won't need 700mm of pipe, but it's good to know that even that length doesn't cause a problem.

 

[Geoff Enigma]

Hi have been following this thread and having fitted some sound deadening material to the engine bay was still keen to reduce sound levels a bit more.
The engine is a Westerbeke W27 which is a 4 cylinder Mitsubishi derived unit.
I had looked at various options and decided to try the universal cone type filter made as an aftermarket car accessory. The benefit of this is cost and it can be cleaned and reused.
Cost was about £12 and using the reducer rings supplied took about 5 minutes to fit. Having motored for around 8 hours since installation I have noticed a reduction in engine noise with no reduction in power. The photo shows the type used they come in different diameters depending upon space in engine bay.

 

[PCUK]

I can't help feeling that the sound insulation is not being effective if intake noise is still so loud. Has every opening been sealed and proper insulated air intakes provided? All hatches sealed with tape. All panels fitted with absorbing and deadening material? Only asking!

 

[pcatterall]

I can't help feeling that the sound insulation is not being effective if intake noise is still so loud. Has every opening been sealed and proper insulated air intakes provided? All hatches sealed with tape. All panels fitted with absorbing and deadening material? Only asking!

My sound proofing in the engine bay is not perfect. I did the easier bits and reduced the noise quite a bit. Current information suggests that the most effective way to get less noise now is the air intake box.


I wonder if there is confusion elsewhere between the idea of an air Filter and an Intake Box.

As an example I would refer to my comments about the Eberspacher air intake silencer, this is very effective but is in no way a filter just a sound (deadening) box which does not restrict the airflow.

 

[macnorton]

1980's Peugeot diesel cars (and others) have remote air cleaners, just remember your engine has a bonfire in the manifold for cold start so retain the gauze..

 

[ianj99]

I wonder if there is confusion elsewhere between the idea of an air Filter and an Intake Box.

I think there has been.
An airfilter will not reduce the noise anywhere near as much as an airbox. Its the tortuous route the air takes that baffles the sound. (as well as the owner)
You cannot possibly seal the engine in a sound proof box - it has to breath so an airbox is needed, even remotely mounted.

For an additional small noise reduction, lay some lead sandwich sound deadening sheet (from noisekiller.co.uk) on the engine, covering the rocker cover and injectors.

 

[The Dogs Pollacks Brother]

Been following this with interest, in fact I posted earlier.
My BMC thumper has no air filter or air box at all so I am thinking now of a bit of a diy jobby just for the sake of curiosity. Am I right in thinking an air box off any motor, with a suitable adaption made from air intake pipe will do the job?...obviously it will have to fit in the space available and be able to secure somehow, but I have noticed the air intake is actually threaded, but I have not been able to find the size or thread yet. Plenty of scrappy's about to have a mooch around so it should be fun trying