Originally Posted by Hangman
I have received SO MUCH more information and SO MUCH more valuable input than I could have EVER imagined.
Thank you ALL for your answers.
So, in essence, the bypass acts just like a turbo's wastegate; sees too much pressure, begins to open. Am I understanding that correctly?
The oil-filter bypass valve responds to differential pressure across the filter media. The valve is plumbed in parallel with the media such that it senses the pressure differential. If the pressure differential across the media exceeds the setting of the bypass valve, the valve opens, allowing unfiltered oil into the engine. Situations where the bypass will open include a restricted filter media, too-high oil viscosity, cold oil [which is more viscous] and high RPM. The bypass valve is different from the oil-pressure-relief valve, which open when engine-oil pressure exceeds the setting of the valve. When the relief valve opens, it dumps oil back into the oil sump, thereby limiting the maximum oil pressure applied to the oil filter and downstream components.
As an example of bypass-valve operation, let's say that the inlet pressure to the oil filter is 50 psi. With Subaru's 23 psi bypass-valve setting, the bypass valve will open when the pressure downstream of the oil filter decreases to 50-23 = 27 psi. With a 50 psi inlet pressure, the bypass valve will remain closed if the downstream pressure is greater than 27 psi. Most auto manufacturers specify bypass-valve settings of less than 23 psi. Some aftermarket oil filters that are listed as fitting Subaru engines have bypass-valve settings significantly lower than 23 psi.
HTH
I have received SO MUCH more information and SO MUCH more valuable input than I could have EVER imagined.
Thank you ALL for your answers.
So, in essence, the bypass acts just like a turbo's wastegate; sees too much pressure, begins to open. Am I understanding that correctly?
The oil-filter bypass valve responds to differential pressure across the filter media. The valve is plumbed in parallel with the media such that it senses the pressure differential. If the pressure differential across the media exceeds the setting of the bypass valve, the valve opens, allowing unfiltered oil into the engine. Situations where the bypass will open include a restricted filter media, too-high oil viscosity, cold oil [which is more viscous] and high RPM. The bypass valve is different from the oil-pressure-relief valve
As an example of bypass-valve operation, let's say that the inlet pressure to the oil filter is 50 psi. With Subaru's 23 psi bypass-valve setting, the bypass valve will open when the pressure downstream of the oil filter decreases to 50-23 = 27 psi. With a 50 psi inlet pressure, the bypass valve will remain closed if the downstream pressure is greater than 27 psi. Most auto manufacturers specify bypass-valve settings of less than 23 psi. Some aftermarket oil filters that are listed as fitting Subaru engines have bypass-valve settings significantly lower than 23 psi.
HTH