Final Filtration: Paper, foam, cotton gauze?
Posted 26 March 2011 - 03:07 AM
Many use paper filters, but these are sensitive to water and resist passing gas once wet. They are also surface packing, so tend to tolerate smaller particulate loads before clogging. The paper ones also cannot be cleaned easily, which is a problem for remote areas. Ideally we'd like the filter to be tolerant of water, particulate loading, and easy to clean when out in the boonies and not able to buy a new one.
Considering the above, we started considering cleanable K&N type off road filters. Which then lead to considering Uni type motorcyle filters. Both of these work mostly from the oil you impregnate them with. But what are the relative merits of these two cleanable filter types?
Here below are some threads from the off-road toys motor toys world on the relative merits on each type. The summary is the paper filters are the best performing filters, but clog faster and can't be cleaned. Of the cleanable type, the foam are better filters than the cotton gauze, which is commonly the K&N. The K&N filter breathes slightly better than all of them, but not an amount that really matters much. Many seem concerned with the filtering ability of the K&N in very dusty conditions.
Info on the Uni foam filter, the standard foam filter. the uni is made from open cell polyurethane foam. this is also called "reticulated foam". it is often two stage- 45ppi and 65ppi. the classic green sock ones are one stage 65ppi.
the different pores per inch (ppi) of different layers. many are done as two stage filters. coarse on outside. fine on inside.
* Standard Twin Air dual-stage foam filter has 45 pores per inch (PPI) on the outer and 60 PPI on the inner foam
* Total thickness of the foam layers when bonded together equals 15mm
* Twin Air foam layers are not glued together, they are laminated
* The lamination process does not restrict airflow between the two layers
* Twin Air foam is open cell polyester foam
if you get serious in off-road racing in very dusty situations, the choice seems to be the ump super filter. these are paper filter cartridges in nice ss housing. they are the big industrial size catridge like common on big forklifts.
Here's some sources for bulk reticulated foam. If you want onesies and twosies, likely get it from Uni directly. They sell bulk foam for homemade filter making.
all thomas net suppliers. http://www.thomasnet...30684500-1.html
http://www.pacfoam.com/appl.htm in so cal. big filter maker
http://www.bobsfoam....etail.html#reti in hayward. big foam warehouse
http://www.airfiltersupply.com/ in sacramento
http://www.appliedai....com/index.html in fremont
http://www.williamsf...m/products.html in sylmar
Posted 27 March 2011 - 04:47 PM
Posted 28 March 2011 - 01:51 AM
vladim, i've only vaguely heard of these, but have not specific info. can you enlighten us further on this type?
Posted 28 March 2011 - 01:55 AM
but what's the difference between regular mattress foam and proper reticulated filter foam? are mattress foams open cell or closed cell, or are there various types we need to distinction between? i went down to the foam mattress store today to find out. i returned with both samples and information.
the foam experts say that nearly all mattress foam and furniture foam is open cell. this is so it breathes and you are less inclined to wake up in a pool of sweat. closed cell is mostly used for flotation applications, like life jackets and some backpack padding things where you do not want it to take up water/sweat.
mattress foam comes in a variety of densities. it appears the most common are around 2 lb/ft3. i got samples at 1.8 and 2.5. in addition to the density varying, they also vary the firmness. this does not relate to density, but to the amount of hardner they put in the foam making process. each density can have various hardnesses. the very dense, but very soft "memory foams" are in the 4 or 5 lb/ft3 it seems.
there are two main types of foam available in open cell: polyester and polyether. both are in the polyurethane class.
the polyester seems to be the one we want. it claims greater resistance to hydrocarbons. in the reticulated line, the proper filter foams, they use the polyester for automotive type apps, and the polyether for fish tank filters. apparently the polyester has some off gassing that the fish don't like. also the polyether holds up better in liquid environments than the polyester.
the difference between the regular open cell foam and the reticulated is an added process of blowing out more of the walls in the foam so as to only leave the "sticks" of the spheres. most of them are gone anyway in the regular foam, but the reticulated process completes this for greater body loading capacity.
you can read all about this in detail here:
all the mattress foam samples they had were in polyether. the only polyester was a black foam common for making camera case packing.
i got both types, and will put them in a cup of gasoline tomorrow and see which one turns into napalm and which one does not.
Posted 28 March 2011 - 05:16 AM
Re: K&N filters (from my dirt bike days), It seems that with 1 cyl 4 stroke motors (mostly after mods that remove the charcoal box and smog stuff and bumpy cam upgrade) the pulse of the draw can suck the oil film between fibers enough to leave 'pin holes' that you can see light thru. I noticed this on four of my bikes, but never my Toyota v6 4runner with a K&N filter... no pin holes after 30K mi.
Posted 28 March 2011 - 06:10 AM
2 - gas in pipe
3 - water spray nozzle
4 - gas out pipe
5 - fan rotor
6 - fan driveshaft
7 - muddy water
8 - water tank
9 - ash cleaner door
10 - water filter
11 - water pump
12 - clean water pipe
13 - tank cover
14 - driver pulley (from engine)
Posted 07 February 2013 - 01:55 PM
Run the wet/dirty gas through an evaporator exchanger in an insulated container.
The humidity in the gas condenses on the coil, turns to water and flows off the exchanger cleaning it a wee bit.
Yes this does require somewhere around 1hp.
Also wouldn't removing water vapor from the gas, and cooling the gas increase its boom boom ?
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