my objective starting out was to determine what exactly goes on inside an oil filter when subjected to differing pressures and pressure differentials.
i made a psuedo oil filter out of a coffee can and clear plexiglass, to test out theory's today. i put a purolator bypass in the coffee can so watch what happens when to much oil flow goes through the coffee can and it starts to bypass. i also had 2 variable inline valves on the inlet and outlet to simulate engine resustance, (yes it takes force to move oil through an engine. so i basically kept closing the outlet valce untill i got a high psi (50psi))
my test rig consister of a high gpm high psi inline water pump, a welded up coffee can with siloconed bottom (to watch) and a purolator bypass from a pl3001 filter. for filter media i used tiny holes which restrict the oil flow, these holes do not infact filter, but i am not trying to make a real world filter, only mesure flow. and these tiny holes simulate resistance to flow like filter media does.
what basically happens is that if the pressure differential gets to great, the bypass will open ONLY ENOUGH to put the pressure differential back down to its maximum. this could mean 90% of the oil still flows through the filter, and 10% bypasses, or 80 20 or 70/30 etc.
you would have to have a 100% clogged filter for the oil to bypass 100%. which i tested by blocking off more and more tiny holes, to simulate filter media clogging. if your filter is 50% clogged, then is is not nessassairely true that 50% will bypass. the remaining 50% of the filter that isnt clogged,could be enough area to promote full flow anyways, or it could not be enough, and the filter would partly bypass 100% of the time, but the filter will never bypass ALL of the oil, unless it is 100% clogged.
now, this is where using oversize filters comes into play. lets say you use an oversize filter with large surface area, it will not clog as easily as a small stock one, and for this reason, the filter is less likely to go into bypass at any given time, because of the larger internal media surface area, the pressure differential will remain lower for longer periods of time, even after the filter gets say 10-20% clogged, then it is perhaps only flowing as well as a stock size filter, which is still good enough and it will still not bypass.
there are so many variables effecting this though.
blowby creates carbon, which clogs filter.
leaky seals promote dirt entering because most modern engines are vacuum emptied via pcv valve and intake vacuum.
a piece of dirt or metal shaving (like casting flashing) can jam the bypass slight or very highly open.
another variable is how long you keep your oil in your engine, naturally the filter will clog up the longer you go between changes, this increases the pressure diffferential because it "robs" the media of its surface area and consiquently, oil flow from the contaimiants the filter captures.
to say that the bypass valve opens either 100% or is closed completely, is wrong, it also does not interupt oil flow, as it is a smooth seamless transition. i used a pressure guage to measure this. i dont have a flow meter though. after i did this, i realised i should of just bought a big oil filter and cut the top off and siloconed a plexiglass plate to the top, as this would be 100% accurate, unlike my testing rig. maybe next weekend i will do this. for now, let the debating begin.
i made a psuedo oil filter out of a coffee can and clear plexiglass, to test out theory's today. i put a purolator bypass in the coffee can so watch what happens when to much oil flow goes through the coffee can and it starts to bypass. i also had 2 variable inline valves on the inlet and outlet to simulate engine resustance, (yes it takes force to move oil through an engine. so i basically kept closing the outlet valce untill i got a high psi (50psi))
my test rig consister of a high gpm high psi inline water pump, a welded up coffee can with siloconed bottom (to watch) and a purolator bypass from a pl3001 filter. for filter media i used tiny holes which restrict the oil flow, these holes do not infact filter, but i am not trying to make a real world filter, only mesure flow. and these tiny holes simulate resistance to flow like filter media does.
what basically happens is that if the pressure differential gets to great, the bypass will open ONLY ENOUGH to put the pressure differential back down to its maximum. this could mean 90% of the oil still flows through the filter, and 10% bypasses, or 80 20 or 70/30 etc.
you would have to have a 100% clogged filter for the oil to bypass 100%. which i tested by blocking off more and more tiny holes, to simulate filter media clogging. if your filter is 50% clogged, then is is not nessassairely true that 50% will bypass. the remaining 50% of the filter that isnt clogged,could be enough area to promote full flow anyways, or it could not be enough, and the filter would partly bypass 100% of the time, but the filter will never bypass ALL of the oil, unless it is 100% clogged.
now, this is where using oversize filters comes into play. lets say you use an oversize filter with large surface area, it will not clog as easily as a small stock one, and for this reason, the filter is less likely to go into bypass at any given time, because of the larger internal media surface area, the pressure differential will remain lower for longer periods of time, even after the filter gets say 10-20% clogged, then it is perhaps only flowing as well as a stock size filter, which is still good enough and it will still not bypass.
there are so many variables effecting this though.
blowby creates carbon, which clogs filter.
leaky seals promote dirt entering because most modern engines are vacuum emptied via pcv valve and intake vacuum.
a piece of dirt or metal shaving (like casting flashing) can jam the bypass slight or very highly open.
another variable is how long you keep your oil in your engine, naturally the filter will clog up the longer you go between changes, this increases the pressure diffferential because it "robs" the media of its surface area and consiquently, oil flow from the contaimiants the filter captures.
to say that the bypass valve opens either 100% or is closed completely, is wrong, it also does not interupt oil flow, as it is a smooth seamless transition. i used a pressure guage to measure this. i dont have a flow meter though. after i did this, i realised i should of just bought a big oil filter and cut the top off and siloconed a plexiglass plate to the top, as this would be 100% accurate, unlike my testing rig. maybe next weekend i will do this. for now, let the debating begin.
