In a message dated 1/22/01 8:09:54 PM Eastern Standard Time,
jemitchell@compuserve.com writes:
> The higher pressure isn't (or shouldn't be) caused by forcing oil
> through the filter. At least not through a clean one. It's all
> the other restrictions - orifices in journals, bearing gaps,
> etc. - that cause higher pressure when oil is cold and thick. The
> oil pump will usually have a pressure relief valve that deals
> with this. When you crank a cold engine (that's not slap wore out
> ;<) the oil pressure stabilizes at a point determined by the
> relief valve. As the oil warms up and thins, the relief valve
> closes and then your oil pressure is determined by the various
> restrictions in the lubrication system and the flow volume. If
> the oil _filter_ constitutes a significant flow restriction, then
> you need to get a better one. Or at least a clean one.
> ;<)
>
>
Makes sense to me. I didn't mean to imply that the filter was
causing the increased oil pressure. I'd always thought that if
the oil was too thick to be forced through the filtration medium
that it might starve some portion of the lubrication system, but
I believe you're correct that other places the oil needs to go
would be more difficult to force oil through than the filter element
itself.
I'd completely overlooked the pressure relief valve, too. Guess
it's been waaay too long since I had my old 911 engine apart....
GH
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