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Guest Message by DevFuse
 

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Oil filter idea/question


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3 replies to this topic

#1 Snowman

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Posted 06 November 2004 - 11:02 PM

Okay, here's something I've been thinking about recently. The stock oil filter on subarus does a pretty good job at keeping junk out of the engine, but there is always room for improvement. Pondering this, I immediately thought about the filtration systems used on HD diesel engines, which need them to filter out all the carbon and deposits in the oil. A couple of alternatives exist. The first is adding a full-flow centrifigul "spinner" type filter to the oiling system, probably in-line to an oil cooler setup of some sort. These filters work with a little assembly inside that has oil jets that make it spin. Centrifugal force causes particulates to be flung outward into the removable paper cartridge. They are highly effective in removing any combustion byproducts or dirt from the oil. The other type of filtration system that I have considered is the addition of a small bypass filter. This would take oil from one of the unused ports in the oil pump through a small restrictor that would allow a very small percentage of the oil to pass into this system, where it goes through a VERY fine filter and back into the oil pan. Even though very little of the total oil volume passes through it at any one moment, the entirety of the oil has passes through several times in the course of a relatively short drive, removing the vast majority of contamination. This way, the primary full-flow filter takes out the big stuff without much restriction in the oil system, and this one takes care of the really tiny particles that can still cause a world of hurt for an engine.

With either of these systems in place, especially in conjunction with an oil cooler, I think it would be entirely reasonable that engine life could be increased, and drain intervals could safely be extended (something that I'm still nervous about but would be willing to try with improved filtration).

Your thoughts please.

#2 NorthWet

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Posted 07 November 2004 - 01:07 AM

My understanding is that the majority of engine wear occurs at startup, when oil pressure is zero and most of the oil has drained off of the friction/bearing surfaces. You can get amazing longevity out of a properly maintained engine that runs almost continuously.

Engine oil's biggest enemy in SI engines is heat. It breaks down the long chain molecules into shorter molecules that have less lubricity.

I think the bigger bang for the buck would be for an oil cooler and some pre-lube (and after-lube if turboed) system.

I am NOT saying that your ideas do not have merit. The centrifugal filter might use the oil from the pressure bypass circuit. You could also go with a total oil system redesign and go dry sump... cooler oil, more options for filtration, bigger pain to design.

BTW, my Honda 350 had centrifugal oil filtration, as did, IIRC, the Fiat 850. They depended TOTALLY on the centrifigual filtration.

#3 Snowman

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Posted 07 November 2004 - 07:45 PM

Hmmm.... good points there NorthWet. The main issue that I had thought might come up with the centrifugal filter is that is might take longer to get oil to the engine at startup. Maybe adding an oil cooler and a small bypass setup would be the best option.

Anybody else?

#4 NorthWet

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Posted 08 November 2004 - 08:48 PM

Hmmm.... good points there NorthWet. The main issue that I had thought might come up with the centrifugal filter is that is might take longer to get oil to the engine at startup. Maybe adding an oil cooler and a small bypass setup would be the best option.

Anybody else?

Sorry, same person. :grin:

One thing with the centrifugal filters that I have dealt with is that they were a minor pain to clean, as they just flung the oil the side of the case. You had to take the case off and scrape/wipe the gunk out.

With a dry-sump, you could do both the super-fine filter (do you know if one is available?) and the centrifugal using the pressure from the scavenge pump. Maybe also use a "sacrificial anode" to deal with acid build-up.

Even if my ideas are useless or a pipe-dream, it serves as a bump for you. :)




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