quote:
I reach the pressure relief on the oil pump all the time as I spin the motor well past 6000 rpm for extended periods.
Okay ...and up until that point 100% of its flow is going to the engine.
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My understanding (that could be very wrong) was that the pressure relief valve in/with the oil pump operates independently of the bypass valve.
Absolutely correct!
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The bypass valve, I believe, opens when there is a pressure differential between what is coming into the filter versus what is going out.
Well, let me rephrase that for you. It's when the exact same flow is creating a differential in excess of the bypass (filter) rating. That is, 5 (choose a number) gpm in ..5 gpm out ..resultant PSID.
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It is the differential that determines the opening of the valve, not the pressure level.
Absolutely correct!
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So it can be at 30 psi idle pressure or 80 psi blow off pressure but it will only open if the out put from the filter is 16 (or 11) psi below what goes in.
Absolutely correct! Except change your perception to "16 (or 11) psi
above what the engine sees downstream".
At 100% flow (pre oil pump relief) the engine is seeing the exact same flow ..hence the downstream pressure should be identical ..as in post media. Only the upstream pressure should be effected.
Here's the rub. The total flow to the engine will be identical (variable for oil pump output) up until your relief limit of your oil pump. At that point you don't know how much is shunted back to the suction side of the pump. A higher bypass valve setting on your filter would make your oil pump reach this relief limit earlier
as it "can" create higher upstream pressure as the filter accumulates debris The current filter with the 11 psi bypass setting will have you reach your oil pumps relief setting 5 psi "later" ..so to speak. How this impacts flow in those circumstances is unknown. You don't know if that means a whole bunch ..or anything worth thinking about.
I'm of the belief (with "adaptive" data) that your typical PSID across a filter is around 2-4 PSID after warm up. This is different when the oil is cold ..naturally ..but I doubt (at least I hope) that you aren't winding your engine out to 6000 rpm with 50 weight oil when it's stone cold.
[ February 27, 2005, 01:01 PM: Message edited by: Gary Allan ]