[Henry Schmidt]

Originally Posted by dannobee

Joe, after reviewing the oil system diagram, I don't believe that [I]all[/I of the pressure drop can be attributed to the filter restriction. Since your second oil pressure tap is teed into the oil gallery that also contains the pressure relief valve and the main bearing feeds, it would stand to reason that the pressure would be lower at that point, even if you had no filter media in the filter housing. Also the built in bypass valve in the filter is likely set to open somewhere around 10-15 psi.

One thing that I did notice about the Porsche spin on adapters (i.e., 964, 993 filter housings that replace the oil cooler) is that the passages are slightly smaller than those drilled in the case, and the consoles have a few sharp turns that would further restrict flow and pressure.

Porsche likely knew this when they designed the disc type RSR oil filters.

The Hubb filter does look like a great design, but the housings would have greater flow if the filter was mounted horizontally rather than vertically.

The oil filters in early 911 that mount to the oil tank are located horizontally .