In an earlier post "Perkins needs more
air"
Nick
DeRocher July 2005
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Hi
Nick,
I didn't know that you could put an air filter on a Perkins. The standard
setup is a domed metal fitting with a screen inside that attaches to the air
intake. It is not so much a screen as a circular piece of metal with
hundreds of round holes in it. Although a filter would add more
protection, it probably is not needed on a boat. You can see a picture of
one at ftp://tognews.com/Perkins_4_108_Models
. Look under Perkins Engines and then "4-108 in a sling.jpg".
Wayne
V-42 C/C RESTLESS July
2005
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You are probably right about not needing
this air filter but when I changed it and looked at how dirty the filter was, I
was surprised. When I climb down into the hell hole, I am always surprised at
how much stuff is floating around in the air and I keep this space pretty
clean.
Nick DeRocher, S/V
Paul Martin
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Does one need an air filter on a boat?
Answer: Just as much as when
operating a farm tractor in dusty field.
Normal 'clean' ambient air typically
contains 30,000 particles (0,03-2µM) per cubic foot. Compress that number
(compression ratio of ~ 12:1) and you get 360,000 particles per cubic
FOOT. Airborne dust and debris circulates globally on the wind currents,
and doesn’t stop at the waters edge. The
The reason all those helicopters
crashed during the attempted 'rescue' of the
If you add an air filter, choose the
largest surface area DRY filter you can fit. The largest surface area
will give the lowest particle velocity through the filter media and will allow
'dwell time' for the particle to adsorb to the filter structure. K&N
is the 'usual' manufacturers of aftermarket engine air filter/housings.
regards, Rich Hampel July
2005
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Our Yanmar 4 cylinder
diesel has no air filter as such, just a perforated can with a fine mesh screen
wrapped around it. The screen becomes fouled with oil and dust after a
season of use but is an easy thing to clean with soap and warm water.
Maybe a paper or fabric air filter would not last in the wet environment on a
boat(?).
Bob Kirbach Walk About July 2005
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Paper automotive air filters are micro cellulosic fibers bound with an epoxy-like wet strength
resin. Such filter media is commonly used to filter liquids. Fabric is
very poor choice due to lack of 'open space' in the structure; plus the fabric
fibers aren’t 'bonded' thus they tend to 'unload' debris under high operating
pressures when the fibers 'flex'.
Rich
Hampel July 2005
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Really? I thought that some of the best
filters (such as K&N) used fabric media soaked in oil. What am I missing.
Philip McConnell Tayana 52 #35, Alejandra Fernandina Bch, FL July 2005
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K&N is the 'usual'
manufacturers of aftermarket engine air filter/housings.
Rich
Hampel July
2005
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Good information. Any
specific suggestions for WHICH K&N filter can simply bolt onto a Perkins
filter riser?
Regards, John Kalpus Prudence
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What you're missing is a lot
unsubstantiated of 'sales-hype' based on industry standards abandoned in the
late 1950s.
If a particle exists in a liquid regime
(oil bath or oil soaked, etc.) then it takes about ten times the 'work' and ten
times smaller retention 'pore' size to do the exact same filtration if the
particle was 'dry' and filter was 'dry' ---- dry gases are more easily (by a
whole 'magnitude' - log10) filtered than mixed aerosols or liquids. This is
because a particle in a gaseous/air/dry atmosphere is in a very high 'energy
state' (oscillatory brownian motion); not so in a
liquid regime. A dry particle is easily removed not just because of physical
size of the particle but chiefly because the *amplitude* of the natural
vibration of the particle - usually larger than the 'pore' of such
filters. For example a 0,03µM particle is easily captured by a filter
that has 0,1µM 'pores'. For liquids it takes a 0,1µM filter to
remove a 0,1µM particle (to 100% efficiency).
Simple speak: DRY filtration is a
magnitude more efficient in retention efficiency (both by weight removal and
size) than 'wetted' filtration.
Secondly, such 'liquid'/flooded
filtration: 1: easily re-entrains particles downstream (low values of
'adsorption') due to 'unfixed' particles already captured; 2. are only
efficient at a narrow single operating condition - rapidly losing efficiency of
capture if the flow is lower OR greater than that narrow single design point;
3. The 'residence time' of capture is typically very small (velocities too
high). If the velocities exceed the design point, all the liquid/oil (now
bound with agglomerated particles) now are vulnerable to 'extrude' through the
device or re-entrain back into the gas stream. That’s why the auto
manufacturers abandoned oil bath filters in the late 1950s - they only removed
rocks sticks and feathers, didn’t capture the important submicronic particulate,
and when full of crud emptied themselves down the
carburetor. The consumer equivalent of such an argument
is the biologically dangerous "'Rainbow' Vacuum Cleaner".
Use DRY and use a LARGE (surface
area) filter that you can fit. And for folks like Charlie and Harvey - be sure
to change that face mask immediately when it becomes wet.
regards, Rich Hampel July
2005
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The largest that will fit, you can use
aluminum manifold 'flex' tube to do the connection. The flex tube is cheap
compressed 'aluminum foil' - auto parts store stuff. You’ll probably have
to 'concoct' an adapter to the air inlet of the engine, hose clamp stuff,
etc. K&N only makes the 'container'.
Like most 'automotive' type filters the filter 'media' is made by a few
technical grade paper mills.
regards, Rich Hampel July
2005
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--Another
thought .....
"Browse" just about any auto
salvage yard, then you’ll be able easily match a common brand/shape of
replacement filter element. Might even be able to 'match' the plastic
inlet duct that attaches to an automobile injector air throttle plate
body. Any standard size old auto air filter assembly would probably be
larger than the maximum aspiration needs of a small marine diesel.
Regards,
Rich Hampel July
2005
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Rich and all: I use the Donaldson Duralite
filter ECC06-5001. It is a canister type that fits right on. If you have
trouble finding Duralite this number will cross reference with other filter
types.
Try: https://dynamic.donaldson.com/webc/WebStore/search/item_detail.html?section=10084&item=15089
Nick DeRocher, S/V
Paul Martin
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Our
air filter is:
Duralite Donaldson
ECC08-5002-DC1250C
215mm diameter
165mm
height
We added an alloy tube to the intake
- this filter is quite large – lays back horizontally toward the rear of the
engine.
Jon
McLeod July
2005
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Jon,
Mine is quite compact, round and sits on top of the intake. It's about
6" in height and about 6" wide. I have changed it underway and
it is easy. I do find that my engine oil looks less black when I change it at
100 hours.
Nick DeRocher, S/V
Paul Martin
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A common cause of black smoke coming out
the exhaust as you increase the RPM is lack of sufficient oxygen to the engine.
Calder says that if you have black smoke, the first thing to check is the air
filter. (Of course, I found the passage in Calder only after the event! Sailing/motoring with Richard and Karen
Genet, on their T-52, black smoke started coming out at about 1500-1800
RPM. Richard tracked it down to an
almost completely occluded air intake filter. After washing it in solvent,
problem was solved).
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I don’t know the 4-108 but if you give me
the cubic inch displacement of the engine and max. possible rpm, I will
calculate a minimum sized (surface area) filter set (or if you have specs
for the maximum CFM aspiration numbers - even better). The most destructive particle size will be
about 5-15µM so most grades of automotive filter media will be OK but one must
be sure that the velocity through the filter is correct so as to allow
sufficient 'dwell time' for capture, etc.
regards, Rich Hampel July
2005
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