Originally Posted By: Filter guy
Originally Posted By: ZeeOSix
Originally Posted By: Filter guy
Also, someone mentioned dry starting the engine with a new filter. Takes less than a second for the oil to flow and lube the engine. That's what the by-pass valve is there for, to allow oil into the engine when there is no flow out of a new oil filter. As the filter fills with oil and allows oil downstream, then the by-pass valve will close. In lab testing this takes seconds on an automotive filter. As they do not prefil the filters for test purposes.
Normally, there isn't enough delta P across the media during a dry start to cause a filter's by-pass valve to open. The oil flow volume at start-up is pretty low, which will not allow much of a PSID across the media ... unless the oil is super thick as in a very cold start-up condition. PSID is a function of media resistance, oil volume and oil viscosity.
As you are aware, fluid takes the least resistance to flow. So with the filter being dry the by-pass will open and by-pass the dry element.
The media IS the least resistive path for the oil in a new filter. The bypass valve will only open after the level of PSID is equal to or greater than the bypass valve's crack open setting. In most Purolator oil filters for instance, that can be 14~16 PSID.
The only way the filters media could produce more PSID than the bypass valve's opening pressure is for the oil flow volume and/or oil viscosity combination to be huge. In a dry start situation, the flow volume is not very much, as the engine is barely above 1000 RPM ... and in that condition the PISD might be high enough (due mostly to high viscosity) to crack the bypass valve only if the oil was super viscous (ie, 0 deg F start-up with 20w-50 oil).
Originally Posted By: Filter guy
Typically you have about twice the GPM flow from the oil pump and regulating valve when you start the vehicle after changing oil. In the neighborhood of 80GPM instead of 40GPM for a car engine. So it doesn't take long for the by-pass to kick in.
Don't know what kind of engine you're referring to ... but for example, an LS6 high HP output V8 only puts out 10~12 GPM at redline. There is no way any normal public road car is putting out 80 or even 40 GPM at idle speeds, let alone 8000 RPM or higher.
Originally Posted By: ZeeOSix
Originally Posted By: Filter guy
Also, someone mentioned dry starting the engine with a new filter. Takes less than a second for the oil to flow and lube the engine. That's what the by-pass valve is there for, to allow oil into the engine when there is no flow out of a new oil filter. As the filter fills with oil and allows oil downstream, then the by-pass valve will close. In lab testing this takes seconds on an automotive filter. As they do not prefil the filters for test purposes.
Normally, there isn't enough delta P across the media during a dry start to cause a filter's by-pass valve to open. The oil flow volume at start-up is pretty low, which will not allow much of a PSID across the media ... unless the oil is super thick as in a very cold start-up condition. PSID is a function of media resistance, oil volume and oil viscosity.
As you are aware, fluid takes the least resistance to flow. So with the filter being dry the by-pass will open and by-pass the dry element.
The media IS the least resistive path for the oil in a new filter. The bypass valve will only open after the level of PSID is equal to or greater than the bypass valve's crack open setting. In most Purolator oil filters for instance, that can be 14~16 PSID.
The only way the filters media could produce more PSID than the bypass valve's opening pressure is for the oil flow volume and/or oil viscosity combination to be huge. In a dry start situation, the flow volume is not very much, as the engine is barely above 1000 RPM ... and in that condition the PISD might be high enough (due mostly to high viscosity) to crack the bypass valve only if the oil was super viscous (ie, 0 deg F start-up with 20w-50 oil).
Originally Posted By: Filter guy
Typically you have about twice the GPM flow from the oil pump and regulating valve when you start the vehicle after changing oil. In the neighborhood of 80GPM instead of 40GPM for a car engine. So it doesn't take long for the by-pass to kick in.
Don't know what kind of engine you're referring to ... but for example, an LS6 high HP output V8 only puts out 10~12 GPM at redline. There is no way any normal public road car is putting out 80 or even 40 GPM at idle speeds, let alone 8000 RPM or higher.
