quote:
Originally posted by 427Z06:
quote:
Originally posted by Gary Allan:
Now WHEN the oil pump is in relief ..this puts the greatest PSID on the filter since it's no longer part of a series circuit. None of the restrictions in the circuit have to merely represent changes in velocity. This is the only time that I've ever seen substantial PSID in across any filter ..even in VERY cold temps with VERY heavy oil.
Huh? When the oil pump is in relief the oil is dumped back into the pan or pump input. How is that going to put the greatest PSID on the filter?
Let me restate that more accurately: You "may" see the highest PSID during pump relief. This can be matched or exceeded by a heavily loaded filter way into its life cycle (or beyond it). It should be trumped by the bypass valve.
(I am, btw, totally open to other interpretations of my reasoning here).
When the pump is in relief you're, typically, at the highest available pressure that the media will see, yet the flow is reduced. The upstream side of the media will see a constant MAX PSI ..while the flow downstream will be reduced. By our frame of reference, the filter is no longer a slice of the total series fluid circuit and can represent a much greater resistance.
Below the relief limit, as seen by the pump, all 'restrictions' only mean a change in velocity. Once the relief is reached, this is no longer the case. Flow is not mandated and it (should) react like any other pressure dependant circuit where any choke is just that, a choke.
There are a few loose ends that I cannot quite "see" intimately. Like.. the reason the pump relief is open is because the engine can accept no more oil at that visc ...so what would a bypass valve accomplish if it opens? It shouldn't be able to pass any more oil ..so what can it possibly do except anntenuate the differential? My mind sees an open bypass valve that's still, effectively, a virtual wall (visions of the Bay of Fundy at high tide).
When I observed higher differentials with my small 1" micro gauges (not the digitals), it was at cold start and it was the downstream pressure that antennuated at a lower level. In extreme cases my lines added to the resistance of the circuit so I'd even see below the normal relief setting of (highest observed AT my point of reference) 82 psi. When there was a differential across the filter, it would be the downstream pressure that would "come up" to meet the supply pressure as the relief closed.
Example:
Normal with light oil at almost any temp:
upstream/downstream
82/80
Heavier oil at cold start
82/74
Very heavy oil under very cold temp
78/62
In this situation my lines reduced the upstream pressure and became part of the resistive circuit. After a few moments (clean filter) it would evolve like this.
(numbers for example only-this transitional state is dynamic an typically brief).
78/62
78/68
79/73
80/76
81/79
82/80
At this point the relief is closed ..my lines are no longer a significant part in the total resistance equation ..nor is the filter.
Add a loaded filter ..and the condition is elongated.
[ June 09, 2006, 09:30 AM: Message edited by: Gary Allan ]
