Was looking on ebay at oil filters and one site had filters they said the bypass pressure is 8 psi. To me that filter should never get dirty as your oil will never go thru the filtering media. Even at idle my bike has 10 psi of pressure. Am I understanding the rating right?.,

 

It depends on the motor. HD has used 5, 10 & 30 micron filters

 

It doesn't relate directly to what pumping pressure is seen by the engine. But it's more to do with the pressure drop through the filter media vs. the flow of oil through it. If the oil is cold, it will be more viscous and more resistant to move through the filter media. More prone to bypass under that condition.

Same result as the filter media becomes restricted with contaminants that it traps. Which is what it's in there for anyway. The engine oil pressure comes in to play as more of a cause/effect. As the pumping pressure increases, so does the volume of oil moving through the system. As the volume of fluid increases, so does the pressure drop at the point of restriction. Clear as mud?

 

8-10 lbs sounds about right. You're thinking that the bypass operates like a high pressure relief valve. In oil filters, its the exact opposite, when the pressure drops below a set psi, the bypass opens to let the oil flow around the filter and not be restricted by it. (Cold starts, restriction in the oil line, etc.).

 

I did not know they had a pressure by-pass! Learn everyday. L.ray

 

WOW, nice bike.