Originally Posted by gathermewool
Originally Posted by geeman789
Let me summarize for you ...
For turbo's, the higher by-pass setting MIGHT matter, in a poorly maintained engine, where the turbo screen bolts MIGHT get clogged, if there were too many by-pass events with REALLY dirty oil and filter. MAYBE.
In a non-turbo engine, it won't make any difference.
That being said, the WIX 7055's are well built, and have the " correct " by-pass setting. They work, and you don't need to stress about the Subaru by-pass spec.
Huh!?
If the turbo screen clogs, it will increase ALL upstream pressure, meaning there won't be ANY appreciable change in differential pressure across the filter.
The dP across the filter is based on the flow rate of oil (engine/oil pump speed), the viscosity of the oil and the makeup of the filter.
Sure ...
Turbo screens get clogged when too much junk goes thru the filter ( or comes OUT of the filter ... ), goes into the oil circuit, and reaches the stupidly fine wire banjo bolt screens, clogging them up and restricting oil flow to the turbo. Which is bad.
The higher by-pass valve pressure DECREASES the number and duration of by-pass events, meaning there is less chance of filter debris getting washed off of the filter media and pushed thru the oil circuit.
This is another reason why some prefer a base end by-pass valve vs a dome end by-pass. Theoretically, IF the filter by-passes oil, a base end by-pass filter should minimize the possibility of any sludge / debris already caught in the pleats from getting washed out and pushed thru the by-pass valve. Maybe ...
Reasonably well maintained engines won't have this issue, because the oil never gets that used up and dirty, and the filter never builds up much junk. So when the filter does by-pass some oil, it's not really that dirty anyway ...
Again, on a non-turbo engine, maintained reasonably well, the oil filter by-pass pressure setting seems less critical. A lower by-pass setting MIGHT allow for more frequent and longer duration by-pass events, but given the oil and filter aren't really that dirty, nothing bad will happen. Obviously FEWER by-pass events are better, but letting some reasonably clean oil go thru unfiltered won't break stuff.
The oil filter by-pass valve is there to prevent a big pressure spike from tearing thru the filter media. It is better to allow some unfiltered oil thru and keep the filter media intact, instead of allow a pressure spike to destroy the media, allowing unfiltered oil thru 100 % of the time.
For those who don't know what a screened turbo bolt, or banjo bolt looks like, here is a pic ...