A question here. Let’s say a 103 or 110 what ever Twin cam engine at operating temps w/ a 20/50 oil, 3.5 to 4 qts- how long does it take for all the oil to make a complete trip through the oil filter at say idle (900-1000 rpm) and maybe (2000 rpm). And/ or how fast does the oil really travel through ( HD filter). I know hat the GPM rating is, but how quickly does it really flow. Curious minds gotta know.

 

I think knowing the GPM should at least give you a good enough estimate. Now, if it drops to 0, that's not good.

John

 

Add some leak dye and see how long it takes to get back.

 

Engineer talk......

 

Harley oiling systems are "high volume/low pressure systems."

I'm gonna WAG that at idle, it circulates about every 20 seconds. And at 2000RPM it circulates about every 15-18 seconds.

I could be way off here, tho.

 

Adding leak dye, now that’s hilarious.

 

!!!! You wouldn't have to calculate for slippage and what's dripping on the ground.

 

Well, I have seen a claim of a measured 18.5 oz flow rate at 2,500 rpm in a TC88. You could then either use the size of the filter to calculate the time through the filter, or remove the filter media and measure it's volume, and calculate the time through that. Either way will give you an estimate.

However, very little may actually be going through the filter media itself. The bypass valves can and do open, bypassing the filtering. Here's an interesting video to watch on the subject, and to simply think about:
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Cool video. Logical that if enough restriction is on the filter material that's above the setting on that bypass valve is reached, it would open.

Resistance is what causes the pressure to rise. And resistance that creates pressure increase, reduces volume flow.

But is all that filter material actually causes that much resistance? So maybe it really doesn't open that relieve valve unless the filter is starting to get full.

Just because you have 35 psi going down the road mean that relieve valve is open. Oil going thru is going to take least resistance. Now if it is enough, filter does need to flow at idle oil pressure.


I have opened a few and there's little in them. But how much resistance is that filter material. My guess is that's what determines how much filter material is in the filter to match the engine it is designed for. So it filters the majority of oil going thru.

 

UT is hilarious.. While some in his discussion talk about fact that the bottom relief works off of pressure differences between inlet and outlet and not absolute oil pressure, what he calls the first pressure release is bunk.. There is more net force pushing the filter onto the front threaded part when the filter is flowing.