Do You Pre Fill Your Oil Filter?

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All our fleet trucks and my Chrysler get pre-filled. We do this because the filters are bottoms up so it is easy. On my daughters Mazda/Ranger you cannot do this, and the same thing on my mower and a couple of other toys we have scattered about.

Nothing like instant oil pressure...
 
Originally Posted By: ZeeOSix
^^^ Don't be so "snotty", and explain to everyone why you think the delta-p across the media will be different if the filter is bone-dry vs. completely wet with oil when the oil viscosity and flow rate is the same in both cases.



I already did, but I'll try again.

You seem to think that sensors on either side of the media measures delta-P across the media. That is only the case once the system reaches a steady state, that is, when both sides are filled and pressurized. You can have high pressure on the media before the second sensor even gets wet and comes into play. You can also have a high flow/high weight load on the media at low pressure on the first sensor, while the media is still unsupported on one side. And you're relying on one person's measurement setup, which cannot model all possible scenarios. For example an upward facing oil filter may not benefit from pre-filling because it may pre-fill itself. In this case it's not measuring any benefit because (I'll admit in this case) there is no benefit. So in this case you'll not see the high delta-P you are looking for.

But all your replies get back to low measured delta-P across this one guy's two sensors, which is only one scenario and only measure a small part of the dynamics. I'll admit it's a great setup once the system is fully pressurized.

Look up "water hammer" if you want to better understand the problems of air and voids in hydraulic systems. Unfortunately the Wikipedia entry focuses on valve shutoff instead of acceleration in voids, turns and baffles, and slug issues, but it does mention them.

HF
 
Originally Posted By: HangFire
Originally Posted By: ZeeOSix
^^^ Don't be so "snotty", and explain to everyone why you think the delta-p across the media will be different if the filter is bone-dry vs. completely wet with oil when the oil viscosity and flow rate is the same in both cases.



I already did, but I'll try again.

You seem to think that sensors on either side of the media measures delta-P across the media. That is only the case once the system reaches a steady state, that is, when both sides are filled and pressurized. You can have high pressure on the media before the second sensor even gets wet and comes into play. You can also have a high flow/high weight load on the media at low pressure on the first sensor, while the media is still unsupported on one side. And you're relying on one person's measurement setup, which cannot model all possible scenarios. For example an upward facing oil filter may not benefit from pre-filling because it may pre-fill itself. In this case it's not measuring any benefit because (I'll admit in this case) there is no benefit. So in this case you'll not see the high delta-P you are looking for.

But all your replies get back to low measured delta-P across this one guy's two sensors, which is only one scenario and only measure a small part of the dynamics. I'll admit it's a great setup once the system is fully pressurized.

Look up "water hammer" if you want to better understand the problems of air and voids in hydraulic systems. Unfortunately the Wikipedia entry focuses on valve shutoff instead of acceleration in voids, turns and baffles, and slug issues, but it does mention them.

HF


I could see that there might a very short pressure spike that isn't very huge (way less than the bypass valve is set too) due to the mass momentum when the wall of oil comes in to the dry oil filter and initially hits the media, but once the initial impact has hit the delta-p across the media is only going to a product of the viscosity of the oil, the flow volume of oil and the flow resistance of the media area.

In other words, if you have 4 GPM of oil (at viscosity x) normally flowing through the filter there might be 1.5 PSI delta-p across the filter ... and that holds true regardless if there is 0 PSI on the outlet of the filter (ie, air) or 200 PSI on the outlet (ie, very restrictive engine oiling circuit). The delta-p you see across an oil filter is not dependent on what pressure levels you are running in the inlet or outlet, it only depends on the oil viscosity, flow rate and the flow resistance of the filter's media area (which is basically a constant).

Link: Flow vs PSID Data

PureOneflowdata.jpg


So if 4 GPM of oil at viscosity x caused a 1.5 PSI delta-p while in full flow, and the filter and oiling system is fully enveloped, what do you think the delta-p is across the media (for a spit second) when that wall of 3 GPM hits the dry oil filter for the first time?

Like I said before, if starting engine with bone dry oil filters on them tore them up due to some insane dealt-p across the media, then you'd be hearing about it all the time, on many different brand of filters. The Purolator tearing issue is not related to staring engines with bone dry filters on them. It's due to other factors that have been talked about a lot over the last 3~4 months.
 
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