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Old 10-01-2008, 04:31 PM
Pooka Pooka is offline
Pooka
 
Join Date: Sep 2005
Posts: 664
Why oil PSI drops during deceleration

Simply put: At higher RPM the oil pump is turning faster so the oil pump, which is a gear pump, is turning faster and pumping more oil.

The greater the volume of oil going into the dischage of the pump the greater the PSI at the opening of the discharge. The only way more volume can move through a set sized hole is with an increase in PSI.

When you back off the RPM of the engine drops quicly and so does the RPM of the oil pump. The higher pressure on the discharge side of the pump drops, too. The pressure that is just past the oil pump discharge is where the PSI is measured, so you are seeing the PSI in the discharge area drop as it responds to less oil being pumped.

The PSI then comes back up to normal as the oil volume in the discharge area of the pump is filled up again.

Well, maybe that is not so simple. Bottom line: this is normal and don't worry about it.

Pooka
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