Full Flow Filter Dynamics

[Gary in Sandy Eggo]

I've just signed up on this board, looks like there's a LOT of REALLY INTERESTING information contained herein. I haven't done a total search, so I hope what I "offer" here isn't old hat and rehash.

My "opinion" of full flow oil filters (not based on scientific experimentation).

1. I think that a by-pass filtration system would do a better job of filtering engine oil. Since the engine's lubrication requirements don't all have to flow through the filter, the filtering medium could be finer to filter out the smallest of particles.

2. I suspect that due to the filter's resistance to flow, ALL spin-on automotive filters operate in by-pass mode until the oil has warmed up to operating temperature. At what temperature by-pass mode ceases will vary from filter to filter depending on how much filtering area there is and how finely the filter medium is designed to filter.

3. I assume all marketed filters will operate in full-flow mode once the oil has reached operating temperature.

4. Based on the above assumptions, I opine that the best full-flow filter to use would be the largest one that will fit that is advertised to remove the smallest of particles.

Looking for feedback and any "scientific" information that'll support or refute any of the above assumptions and opinions.

Regards, Gary in Sandy Eggo

 

[TC]

1. Yes, that's been proven, and is the intent of bypass systems. The PureOne has pores down to 10 microns (Grease's study), while bypass medias go down to around the 1 micron level (rough estimate).

2. I wouldn't use the "all" word here -- a thin oil could potentially, readily work its way through the media of a large-area filter, even during cold starts. And in some other applications, bypass might be continuous for an extended period, in my opinion. A Bosch #3312 filter (81 sq in media) is what Bosch calls for in my 3.0L Mitsu-Chrysler, while a PureOne #24458 (near 200 sq in media) can be used on a 1.5L Honda. The Chrysler scenario would result in 27 sq in media per liter of engine, while the Honda scenario would result in about 133, a ratio five times greater. I could imagine, hypothetically, that the Chrysler could experience extended bypass during cold starts, while the Honda might see only initial bypass. (Pure speculation, but you get the concept.)

Also, the Fleetguard filter for my ride has an 8 psi bypass, while bypass for some German rides is typically around 30 psi (that's a whole 'nother novella). As you can imagine, the Fleetguard would welcome bypass like a crack fix, while the German filter would be more likely to keep its bypass border closed to foreign oils.

3. I'd say yes, except possibly during high RPMs, throttle spikes, and clogging filters.

4. Absolutely!

http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=6;t=000976

[ April 06, 2005, 07:08 PM: Message edited by: TC ]

 

[Ken2]

1) Yes, but will the owner put enough miles on the engine, transfer the filter assembly to his next engine, run the oil the full life of the oil, do analyses to protect the warranty, etc. so the bypass pays off?

2) I don't agree, but we won't know unless some testing is done.

3) I agree.

4) In the unlikely event of an oil filter failure causing engine damage, the filter maker is on the hook for the cost of repairs IF you use the filter they specify for your engine. If not, too bad. The engine design engineers pick the filter for that engine knowing much more than we do...they pick a filter that will protect the engine for at least the full listed oil drain intervals for at least 100,000 miles while the car company is liable for the extended warranties they sell.


Ken

 

[Filter guy]

Just remember that unless the filter element is totally plugged, even when the by-pass valve opens up----oil is going through the filter media.