Lone Ranger

Taking hydraulics into account, in order for the spring loaded bypass valve in the oil canister lid to work, it would seem apparent that the oil would have to be entering the filter compartment through the horseshoe shaped port on the compartment floor, fill the interior of the filter, and flow from the inside of the filter out, exiting the compartment through the port that is located at around 10 o'clock (as you stand @ front of car), on the compartment wall about halfway or so up. This way, if the filter is restricted or otherwise cannot maintain flow rate for the current oil pressure, hydraulic pressure would build until the necessary psi (80 I think) is reached to compress the spring in the cap and open the bypass port, allowing (unfiltered) oil to flow out the bypass port in the cap (and under the bottom of filter since lifted off floor by hydraulic pressure).

If oil is entering the compartment the other way around, i.e. through the wall port and flowing into the filter from the outside, with the resulting filtered oil exiting through the floor horseshoe port, well, maybe I've got it wrong, but I'm having trouble seeing how hydraulic pressure would cause the upward lift on the filter to compress the bypass spring in the lid, if the pressurized oil (due to restriction in filter media etc) is on the outside of the filter. Seems hydraulic pressure would have to build in the filter's center channel to cause necessary upward force to compress the spring.

So I'm thinking the oil must flow from the inside of the filter out, and exits out the wall port. This theory also seems to validate the narrower center channel on the Delco and other OE style (Wix) filters.

Maybe I think too much, but this is how I see it.

an08HHR

Most oil filters work on the principle that it flows from the outside of the filter to the inside. There if more filtration of the filter by flowing oil in that direction. hope I'm not wrong on this.

Lone Ranger

However, taking into account pleated filter media, in order to properly take advantage of the pleated media's surface area for filtration, the oil would have to enter the filter from the outside, hitting the exposed surface area of the pleats, in order for best balance of flow vs filtration from the media.

So it looks like maybe in fact the oil enters from the wall port and exits out the floor port, when taking filter media pleating into account.

I told you I think too much.

Lone Ranger

No, I think you're right. I must have been typing my 2nd post as you were typing yours.

an08HHR

I think the best when I don't try to think but that can be just as bad. On reg spin on can filters that is the way the oil flows so I assume it is the same on our filters.

Snoopy

Lone Ranger.....

From outside to in ( I was just informed). Easy way to remember and to verify.....remember all the posting of owners having piss fits because they found metal particles on the outside of the filter. That couldn't possibly have occurred if the process was in reverse....your engine would have ingested the particles.

Also, if it was inside to out, the particles would have been on the inside surface of the filter.