Bob,
RE:"I guess I thought the built in valve served essentially the
same function. Aren't they both operated by excessive pressure?
No, not exactly. The "built-in" oil relief valve bleeds excessive
oil pressure by beginning to open at a certain pressure and letting
*filtered* oil drain back into the sump. The bypass valve in the oil filter
opens when there is a pressure *differential* across the filter, and lets
some *unfiltered* oil into the galleys. The total oil pressure could be
extremely high, 120 psi or whatever, and the bypass valve in the oil filter
would not open as long as the pressure on either side of the filter was
similar. One would expect the other valve, the one "built in" to the
engine, to be full open in this instance.
I'm not aware of any published spec for the stock TR6 oil filter
bypass valve, but for reference, the oil filter bypass in a J52 turbojet
engine begins to bypass at only 5 psi differential pressure, and the filter
is fully bypassed at 8 psi. Normal operating oil pressure on that engine
was 45 psi.
Best Regards,
Tom Marincic
CD3574L
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