So, let’s go back to the whole point of this thread.
What relevance does the light have when it is shining through the bypass valve?
The YouTuber, and a couple of people here, seem to think that this is disastrous. And indicative of poor quality.
Is it? I honestly don’t see how it really changes much of the efficiency the filter at all. How much oil is actually going through where that light shines?
It all depends how big of a gap/leak there is for dirty oil to bypass the media. If it's a very small leakage, the overall efficiency probably won't be impacted too much. Even the bypass valves that are metal-on-metal may have some very slight leakage. WIX filters with the base end bypass valve is also simply a metal-on-metal interface where the bypass assembly mates to the end cap, pressed tight from the assembled spring force of the leaf or coil spring in the end of the filter.
A lab (once refereed to the "bat cave" when it was being discussed many years ago) checked out some of the WIX XPs that had a pretty bad ISO efficiency at the time (50% @ 20u per WIX), and the conclusion was the end caps where not sealed very well, so if there is a pretty bad leakage, it can be pretty impactful to the efficiency. They tested just the media assembly out of the spin-on to take the leaks out of the equation, and it then tested better in efficiency. The reason Fram used a fiber ring to seal the leaf spring to the end cap on the OG Ultra was to help ensure efficiency. Fram isn't using that fiber seal anymore on any of their filters - probably a cost cutting move.
Here's something to ponder. With cartridge filters, there are countless housing designs and methods used to seal the cartridge inside the housing when assembled. Looking at how some of the cartridge filters assemble seal in the housing and cap, not all use decent sealing techniques inside the housing. Therefore, it's entirely possible for some slight dirty oil leakage to happen inside a cartridge filter housing depending on the exact design of how the cartridge is sealed inside the housing.
Personally, I'd rather have a spin-on oil filter than a cartridge filter for many reasons. The fact that the built-in bypass valve is a fixed setting, if it's set relatively low then that means there isn't much bypass setting headroom to take up filter dP vs flow and filter loading factors. I don't know what some of these cartridge filter bypass valves are set to, so it could be they are set relatively high. I do know my Z06 built-in bypass valve was only set to 10-12 PSI, which is pretty low for a filter bypass setting.
Because that filter, and the valve, under zero pressure with a flashlight, are gonna behave differently than they do in an engine when a high-pressure slug of oil from the pump hits it on a cold start up, or when that engine is running with a steady stream of moderate pressure.
Just because you can measure something, doesn’t mean that you should, or that it has any meaning.
The light leakage through the gap that people are referring to is between the leaf spring and the end cap, and it's a metal-to-metal seal. It's not actually on the bypass valve itself. WCW's video showed him pressing down as hard as he can (probably close to the spring force of the leaf spring when under assembled force) and the air gap didn't close, so the leaf spring was too stiff to deform and close up the air gap. It almost looked like there was a burr or protrusion there, but he didn't go in for a closer inspection. The simple fix for that would be for the leaf spring to be made flatter and smoother in the area where it mates with the end cap - a simple tweak to the manufacturing process.
When they test the efficiency of these filters, are they doing it with that bypass valve there? Because if they are, then the filter works pretty darn well, despite the flashlight test failure.
Yes, the entire filter assembly just as it's use on an engine, is tested for efficiency.
