Restrictive filter starves engine of oil?

[Chris A]

In the VOA section, it was said that a restrictive oil filter can starve the engine for oil. The thread is:
http://theoildrop.server101.com/ubb/ultimatebb.php?ubb=get_topic;f=3;t=000709;p=1#000019

Is there any truth to that and if so, can someone explain it to me?

Also note that the engine in question is a GM SBC which has the bypass valve in the block, so that is not a function of the filter.

 

[dickwells]

The problem may be related to a miscombination of oil and filter. I use a pure1 in my 02 Silverado and the pressure comes up within 2 seconds using Mobil 1 5W30. Now if I was using 15W50 in something I think I would select a higher flowing filter like a K&N. No matter which way you go you have to be observant and see how it is all working.

 

[rpn453]

I could be wrong, but I was under the impression that all oil pumps are positive displacement pumps. So they will always put out the same flowrate for a given engine rpm (may reduce slightly as wear increases clearances). Therefore, a plugged filter or highly restrictive filter could cause the bypass to open, but not reduce oil flow.

[ August 11, 2003, 02:24 PM: Message edited by: rpn453 ]

 

[7TFord]

I think what is meant is that there is a fine line between the quality of filtration offered by the filter media of a given filter and the point at which that media may restrict the flow of oil. This may or may not be redundant as already suggested, as a filter has a bypass function as to not allow the oil supply to be stopped completely. One filter may clean your oil better than another though.

 

[Patman]

A filter could be restricting oil flow, but the restriction might not be big enough to kick it into full bypass mode, but it's restricting enough that the flow of oil is interupted. Perhaps "starved for oil" is a bit extreme, and I should've worded it differently.

 

[Steve S]

I would opinion that the bypass valve starts to open when the pressure differential between the inlet of the filter and the outlet causes the bypass valve to open allowing unfiltered oil to circulate through the engine "Clark equipment training". But there is also the theory which could be more truth than not that the bypass may be open alot more than we would guess so that Ralphpwoods theory of the full flow filter may be correct .I have always been taught that a full flow filter catches the largest most damaging particles. But then again for the longest time I thought synthetics were the best but it may be the additive package that makes the oils perform so well.

p.s. different viscosities do flow through the filter media differently as do synthetic vs.petro oil as well as cold oil vs.hot oil.

[ August 12, 2003, 01:21 AM: Message edited by: Steve S ]

 

[rpn453]

quote:

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A filter could be restricting oil flow, but the restriction might not be big enough to kick it into full bypass mode, but it's restricting enough that the flow of oil is interupted.

---

I disagree. As long as the filter and oil passages are full of oil there could be no interruption, since oil is pretty close to incompressible and the pressure would rise to that of the bypass setting almost instantaneously.
The problem of momentary oil starvation could occur if an anti-drainback valve wasn't functioning properly though.

[ August 12, 2003, 02:18 PM: Message edited by: rpn453 ]

 

[Ken2]

1) Where is your oil pressure gauge connection located in the oil circuit? Between the pump and the filter?...then is does not show the oil pressure going to the engine, just the pressure going to the filter. If the gauge is connected downstream from the filter, it will show the actual oil pressure to your engine.

2) The pressure control valve inside the oil pump assembly will maintain an almost constant oil pressure out of the pump once the engine is up to speed. If there's more resistance in the oil system, the pressure control valve opens more, dumps more oil back to the sump, and reduces the flow to maintain relatively constant pressure.

3) Whether the oil filter bypass valve is in the mount, GM style, or in the filter, it works about the same way. When the set point differential pressure is reached, maybe 6 psi difference between the filter inlet and outlet, the bypass valve begins to open. When the differntial pressure is higher, maybe 9 psid, the valve might be fully open and bypassing all the oil past the filter media. This might be the actual settings for a nominal "8 psi" bypass valve.

4) How do you know what's really happening?...you need more instrumentation. You need good oil pressure gauges on both inlet and outlet sides of the filter.


Ken