oil filter flow percentage

[OVERKILL]

The rest of your explanation is beautiful and well articulated, but you appear lost on the fundamental concept that the bypass is actuated by a DIFFERENTIAL in oil pressure, not oil pressure itself. If the filter media can flow 8GPH, and the oil pump is putting out 5GPH, where is the primary resistance in the SYSTEM here?

Well of course it is NOT the filter!

Now, where does oil PRESSURE come from? Well, it is resistance to flow.

We've already established that the filter at 8GPH can handle more flow than what the oil pump is putting out at 5GPH.

But we are still developing lets say 40PSI of oil pressure. Where is that resistance coming from? Well, it is coming from the engine oiling system AFTER the filter.

This means that on the INLET side of the filter, we are seeing 40PSI from the pump.

But this also means that on the OUTLET side of the filter, we are seeing 40PSI of resistance from the rest of the lubrication system (after all, we've established that the oil filter, capable of flowing 8GPM is not causing much resistance to flow when the pump is putting out 5GPM).

What is in between these two points?

The filter, and its bypass.

Now, what causes the bypass to open?

That would be pressure on ONE SIDE of the bypass, and LESS pressure (a differential) on the OTHER side of the bypass.

In the case of the FL-1A, that means that the pressure on one side of the valve needs to be 12PSI lower than on the other side of the valve.

So, if we have 40PSI of resistance on the outlet of the filter and 40PSI of pressure on the inlet of the filter, do we have a differential?

NO.

So the bypass remains CLOSED. This means that ALL the oil is going through the filter media.

Now of course it is NOT always this way!

When the oil is COLD, the media is simply unable to flow enough of the oil. The oil pump is putting out its 5GPM, but the oil filter is unable to flow 5GPM of thick, heavy oil.

This creates a differential. The pressure we see on the OTHER side of the filter is LOWER than what the oil pump is seeing.

If we are seeing 60PSI for example after the filter, the oil pump is seeing at least 72PSI to overcome the bypass on the filter.

This is the differential that causes the bypass valve on the filter (or in the block) to open. Cold oil will flow more readily through an engine than it will through dense filter media. However, the oil doesn't flow as well overall regardless, and also why cold, thick oil can actuate the relief on the pump as well.

 

[OVERKILL]

QuadDriver:

I may be able to illustrate this in a way that is a bit easier to follow.

Have you ever run an engine without an oil filter? IE, with an empty canister or an older engine that didn't have a filter period?

I have a lot of experience with 30's and 40's marine engines, and most of them didn't have filters.

However, they still had oil pressure!

Now, why did they have oil pressure?

Well the obvious answer that I'm sure you and I can both agree on is that the engine resists the volume of oil that the oil pump is displacing and so we end up with back-pressure in the system, this resistance to flow, the resistance of oil through the galleries is where our oil pressure comes from.

Now, on an engine with a full-flow filter (NOT a bypass filter setup like a diesel or some of the adapters people use) will have either the bypass in the block or remote filter mount plate (BMW) or in the filter itself. In any instance, the relief pressure on this valve is somewhere less than 20psi.

Keep that in mind.

So on an engine that develops a nominal oil pressure of 40PSI at idle, hot, on 5w30 with NO OIL FILTER, if we stick a full flow filter between the oil pump and the feed to the rest of the engine and we still have that 40SPI hot at idle, where does that oil pressure come from?

Well it comes from the same place it came from before: the engine's oiling system.

In a case like this, the oil filter, able to flow enough oil to satisfy what the pump is displacing and what the engine can handle, is transparent to the system.

When the filter is transparent, there is no pressure differential (the engine creates 40PSI of back pressure, the pump is seeing 40SPI of back pressure) and so the bypass on the filter (or with an in-block setup) remains CLOSED.

Now of course there are two scenarios where the bypass WILL open:

1. With cold oil, as the filter media will flow less heavy oil than it will thin oil.

2. At high RPM's where the pump has the ability to displace more oil than the media can handle.

In either of the above scenarios, the oil pump will see more resistance on the outlet side than what the engine provides at its feed orifice on the other side of the filter. This creates a differential and subsequently the bypass on the block or in the filter opens, letting a percentage of the oil bypass the filter media.

 

[OldCowboy]

That is a great explanation of how a bypass works. And a good understanding of what the other poster is missing.

 

[QuadDriver]

Id suggest a little fluid dynamics. there will be a pressure drop at every single inch of the oil circuit. across a filter. across an oil gallery. across a bearing. as I have stated, the people running said test had no earthly idea what they were doing. they didnt try to produce the reynolds number for the filter. they didnt even try to approximate the apparent roughness of the overall package so that any 'numbers' obtained would even make sense. I, and lets be honest, any oem manufacturer would consider the results of the 'test' to be dimensionless nonsense.

the filter media, and the bypass are exactly no different than 2 resistors in parallel. the flow into the filter(as a whole), will always equal the flow out of the filter.

the filter cannot consume oil.

the filter cannot produce oil.

which means simply, if at a given psi input, with corresponding flow, the oil cannot flow thru the media AS THE ENGINE IS SUCKING OIL AWAY, then the bypass will open. The difference is 12psi. there is no way given yours, or anyone elses setup, to measure any "pressure differential" between the media and the bypass and anyone who thinks different probably should not be under the hood of vehicles?

do you realize how LITTLE 12psi is? (and as I said, the manu specs are 8-12 psi, mass production and springs being what they are. you assume 12. 8 is even worse)

An FL1 bypass is nearly always open at all times to some degree. Even with or without some other appliance which may or maynot also be open.

Has been since the 60's.

will be until they stop making them.

An FL1 (and its clones) are considered uncloggable. Which is why they are the basis for EVERY hipo application? (hint: PH8 is the same) The test for this is so mind boggingly simple (albeit requiring hardware you dont have) I am surprised it was never mentioned.

 

[OVERKILL]

Originally Posted By: QuadDriver
Id suggest a little fluid dynamics. there will be a pressure drop at every single inch of the oil circuit. across a filter. across an oil gallery. across a bearing. as I have stated, the people running said test had no earthly idea what they were doing. they didnt try to produce the reynolds number for the filter. they didnt even try to approximate the apparent roughness of the overall package so that any 'numbers' obtained would even make sense. I, and lets be honest, any oem manufacturer would consider the results of the 'test' to be dimensionless nonsense.

the filter media, and the bypass are exactly no different than 2 resistors in parallel. the flow into the filter(as a whole), will always equal the flow out of the filter.

the filter cannot consume oil.

the filter cannot produce oil.

which means simply, if at a given psi input, with corresponding flow, the oil cannot flow thru the media AS THE ENGINE IS SUCKING OIL AWAY, then the bypass will open. The difference is 12psi. there is no way given yours, or anyone elses setup, to measure any "pressure differential" between the media and the bypass and anyone who thinks different probably should not be under the hood of vehicles?

do you realize how LITTLE 12psi is? (and as I said, the manu specs are 8-12 psi, mass production and springs being what they are. you assume 12. 8 is even worse)

An FL1 bypass is nearly always open at all times to some degree. Even with or without some other appliance which may or maynot also be open.

Has been since the 60's.

will be until they stop making them.

An FL1 (and its clones) are considered uncloggable. Which is why they are the basis for EVERY hipo application? (hint: PH8 is the same) The test for this is so mind boggingly simple (albeit requiring hardware you dont have) I am surprised it was never mentioned.


Going by the above, explain why an engine with no oil filter will still have oil pressure?

And yes, the pressure drop across the filter media was NOT zero, it was around 2PSI if I remember correctly, still far less than what is required to open the bypass on the filter.

No, the filter doesn't produce or consume oil, it PASSES oil, I don't believe I've implied otherwise?

However, you are looking at this from a linear perspective, if that was the case, there would not be measurable oil pressure at the orifice on the other side of the oil filter, as you are implying that the filter/bypass create the system's pressure, which is clearly not the case.

If the engine SUCKED OIL at a rate greater than the pump supplied it, WE WOULD HAVE NO MEASURABLE OIL PRESSURE on an engine without a filter, as you are implying here that the filter and bypass are the source of resistance in the system here, and that is not the case.

The oil pump supplies MORE VOLUME than the engine can consume, that is how we end up with oil pressure! With a filter that can flow enough volume to accommodate what the pump is putting out, there is NOT a large enough differential across the relief to cause it to open.

 

[LordAbbett]

"which means simply, if at a given psi input, with corresponding flow, the oil cannot flow thru the media AS THE ENGINE IS SUCKING OIL AWAY, then the bypass will open. The difference is 12psi. there is no way given yours, or anyone elses setup, to measure any "pressure differential" between the media and the bypass and anyone who thinks different probably should not be under the hood of vehicles?"

The media has two sides. Basically inlet to filter and outlet from. This is what the filter bypass valve sees and the only pressure relevant to the valve.

Are you saying that there is no oil pressure downstream of the filter beacause the engine is sucking it all away???

 

[OVERKILL]

Originally Posted By: LordAbbett

"which means simply, if at a given psi input, with corresponding flow, the oil cannot flow thru the media AS THE ENGINE IS SUCKING OIL AWAY, then the bypass will open. The difference is 12psi. there is no way given yours, or anyone elses setup, to measure any "pressure differential" between the media and the bypass and anyone who thinks different probably should not be under the hood of vehicles?"

The media has two sides. Basically inlet to filter and outlet from. This is what the filter bypass valve sees and the only pressure relevant to the valve.

Are you saying that there is no oil pressure downstream of the filter beacause the engine is sucking it all away???


That's the point I'm getting hung up on here too. If the oil pump didn't put out more oil than the engine was able to consume, we wouldn't have any oil pressure, and there would be no need for a relief valve on the oil pump, as there would never be any oil pressure.

 

[LordAbbett]

Originally Posted By: OVERK1LL
Originally Posted By: LordAbbett

"which means simply, if at a given psi input, with corresponding flow, the oil cannot flow thru the media AS THE ENGINE IS SUCKING OIL AWAY, then the bypass will open. The difference is 12psi. there is no way given yours, or anyone elses setup, to measure any "pressure differential" between the media and the bypass and anyone who thinks different probably should not be under the hood of vehicles?"

The media has two sides. Basically inlet to filter and outlet from. This is what the filter bypass valve sees and the only pressure relevant to the valve.

Are you saying that there is no oil pressure downstream of the filter beacause the engine is sucking it all away???


That's the point I'm getting hung up on here too. If the oil pump didn't put out more oil than the engine was able to consume, we wouldn't have any oil pressure, and there would be no need for a relief valve on the oil pump, as there would never be any oil pressure.

Completely agree.
And the filter bypass only opens if the filter media can't flow enough and causes the pressure diff across the media. At least enough to open to valve. But the filter does not create oilpressure the engines restriction the flow does

 

[OVERKILL]

Originally Posted By: LordAbbett
Originally Posted By: OVERK1LL
Originally Posted By: LordAbbett

"which means simply, if at a given psi input, with corresponding flow, the oil cannot flow thru the media AS THE ENGINE IS SUCKING OIL AWAY, then the bypass will open. The difference is 12psi. there is no way given yours, or anyone elses setup, to measure any "pressure differential" between the media and the bypass and anyone who thinks different probably should not be under the hood of vehicles?"

The media has two sides. Basically inlet to filter and outlet from. This is what the filter bypass valve sees and the only pressure relevant to the valve.

Are you saying that there is no oil pressure downstream of the filter beacause the engine is sucking it all away???


That's the point I'm getting hung up on here too. If the oil pump didn't put out more oil than the engine was able to consume, we wouldn't have any oil pressure, and there would be no need for a relief valve on the oil pump, as there would never be any oil pressure.

Completely agree.
And the filter bypass only opens if the filter media can't flow enough and causes the pressure diff across the media. At least enough to open to valve. But the filter does not create oilpressure the engines restriction the flow does


Exactly. Now the filter media does create SOME resistance, but it is, when the oil is hot, not enough to activate the relief.

 

[QuadDriver]

Originally Posted By: OVERK1LL
QuadDriver:

I may be able to illustrate this in a way that is a bit easier to follow.

Have you ever run an engine without an oil filter? IE, with an empty canister or an older engine that didn't have a filter period?

I have a lot of experience with 30's and 40's marine engines, and most of them didn't have filters.

However, they still had oil pressure!


Stopping, an oil filter does not create pressure.

Your oil pressure reading is taken at the output of the pump. Does that number tell you ANYTHING useful about the engine? no. it tells you that the pump has done so much work. pressure, in fluids, is the result of work. no more. no less. A fully clogged filter with no bypass may read a very high reading which as I said has no bearing on the engine internals.

At that moment your oil enters some passage to some sort of filter mounting location.

There is a pressure drop in that passage.

at the filter, there is a pressure drop across it. Even if the filter housing was empty, the path oil must flow would encounter some roughness (expressed in a coefficient k when calculating pressure drop.)

There is a pressure drop in all galleries. If we assume a priority main type engine and are willing to ignore the drop across the long galleries, each main gets the same PSI.

In reality this is not true. On your ford, or my GM, the oil pressure is the greatest at the #1 main, or #5 main respectivly.

it may well be the case that by the last main bearing there is no oil pressure.

How much oil pressure does it take in an avarage motor at each bearing shell to guarantee that adequate oil is available to be scavanged? 5-7psi. thats it. no more. no less.

therefore the function of the oil pump is simply to produce enuf pressure at each rpm to push oil thru fixed passages.

the early posts you made clearly indicated a belief (that is commonly held here) that we pump oil into bearings. even tho people use the correct term 'hydrodynamic lubrication' or variants thereof, no one really bothered to look up what is happening.

fact: a moving piece of metal with a certain surface area moving at a certain speed will grab hold of, and accelerate away a fixed amount of oil given other fixed values: clearance, speed, viscosity, area. Always will. always has.

fact: same metal, suspended and spinning around a fixed point (like a con rod big end) will thru centrifugal force, pull oil away from the main bearings. some main bearings support more than one con rod. This requires a greater AMOUNT of oil (read: volume) to be present at the main bearing shell than the bearing itself can consume. This amount increases drastically with rpm as centrifugal force does.

Quote:

Now, why did they have oil pressure?


this is acutally an ambiguous question. the combined resistance of every single gallery, rod, tube, turn, fitting etc is what physically gave you said pressure, but the amount of pressure was determined by test results that showed a certain pressure at that point and no where else will guarantee the flow required.

Quote:
So on an engine that develops a nominal oil pressure of 40PSI at idle, hot, on 5w30 with NO OIL FILTER, if we stick a full flow filter between the oil pump and the feed to the rest of the engine and we still have that 40SPI hot at idle, where does that oil pressure come from?

Well it comes from the same place it came from before: the engine's oiling system.

In a case like this, the oil filter, able to flow enough oil to satisfy what the pump is displacing and what the engine can handle, is transparent to the system.


If you are insinuating that there is no pressure drop across a filter, you are wrong and this is easily test-able without understanding fluid dynamics.

There is no such thing as a 'frictionless filter' and there is no way in heck you are getting laminar flow in a filter. the Rnumber is going to be very very high across any filter, bypass mode or not.

therefore this statement:
Quote:

When the filter is transparent, there is no pressure differential (the engine creates 40PSI of back pressure, the pump is seeing 40SPI of back pressure) and so the bypass on the filter (or with an in-block setup) remains CLOSED.


cannot ever exist

There once was, but I have not found it, a figure posted by filter oems giving the ratio of oil in, to the amount of oil thru the media and not the bypass. This among all other things would close the argument forever and if I had found it I would post it. Suffice to say, the ratio IIRC was about 1/5. for every 5qts pumped in hot, 1 goes thru the media. This is no different than an amsoil super whatever filter where the ratio might be 1/20. But that ratio matters not, at 5gpm pumping on a 1 gallon sump at a 1/5 ratio, it means in every minute, every drop has passed thru the filter.

sidebar: about 10 years ago - or more- honda engineers got out of this argument forever by desiging the VF engines to bypass the oil pump at higher rpms because at that speed the shafts immersed in the sump would suck adequate oil themselves using the same principles I outlined above and before, by drilling holes in the right places, thereby freeing 8-9hp. This is not practical on a car engine obviously

 

[LordAbbett]

my engines read oil pressure not at the pump but after the filter
And I don't think ever overk1ll ever said that the there is NO pressure drop across the media or the engine

 

[QuadDriver]

fluid flow, is exactly analagous to electrical flow. In fact, the calculations to gather flow (current) or pressure (voltage) across a pipe (wire) are stunningly the same in principle.

if I were to stop an engine - but not its oil pump, I would easily read an astronomically high reading on the gauge. you to can do this by simply driving the oil pump with a drill, using a collet if required to restrict oil loss at the upper distributor bearing (look at your jegs catalog, all the parts to do this are in the tool section)

at least half of your oil is ejactulated into the heads with very little resistance outside of the cam bearings. priorty main or not, half of the oil supply is at the cam. from the cam shells to the lifters where is still flows relatively resistance free into the pushrods, aided of course by the plunger disc and spring so it does not just ooze into the head, but squirts. One of the first thing on a hipo motor we do is restrict this.

Im not too worried at idle. any pressure at idle will present oil to the bearings who will as I have said, suck it away. on older engines you can make the case that it is possible to force a small amount of oil into the bearings by pressure alone i'e' engine not running. but consider this: your cars oil light is dumb. it goes off at about 7psi. on badly worn engines, it can and does come on at rpms over idle, simply because the pressure at the boss fell lower than 7psi. The oiling system, is designed to increase flow with rpm. everyone with accurate gauges has noticed that when horsing around, pressure drops a good 10psi or more over 4000rpm sustained on a stock oiling system.

a hi volume pump is indeed able to pump more oil per rotation than stock, however, everything elsde is the same, in order to move more oil inside same size passenges, more pressure is needed.

conversely, there are those that shim or replace their stock pump bypass springs to increase system pressure, with no other changes. they are the ones who put all the oil in the heads and starve the bottom ends.

but I have digressed, going back to the circuit example.

if I have a 12v power supply and 12 1ohm resistors strung off the positive end and I measured voltage at any point, it wil always read 12.

if I complete the circuit then I will be able to see 12 at the supply, 11 at the first, 10 next, etc until I get to 0.

same with the engine and going along with my previous 'cast and drill/tap comments.

If a person had the ability to take readings from the pump boss, down to the last con rod, and at every passage, the gauge would read lower, and lower, and lower.

As I said before Im not worried about oil pressure at idle. light off? then all is good.

In this oil circuit, a concept missed is that the engine, as a whole, post filter is NOT a fixed resistor. but rather a variable one. the faster the engine goes, the less resistance to oil flow it presents. This fact is rejected in the other posts evn tho the rejectors accept the fact that the engine requires more oil at higher rpms.

Use this analogy:

the oil filter is a resistor of 1 fixed ohm and the engine at idle is 100 ohms. at idle, the drop would be appx 1/100th of the total.

but run the engine to 5000rpm, now the engine may appear as 20 ohms. the drop over the filter is now 1/20th. a factor of 5.

when various oil filter manufactureres make claims about pressure drops across filters they are not referencing 'at idle'. Someone ran a rather detailed test.

 

[QuadDriver]

Originally Posted By: LordAbbett
my engines read oil pressure not at the pump but after the filter


and what engines are these?

Quote:

And I don't think ever overk1ll ever said that the there is NO pressure drop across the media or the engine


actually, he did

 

[QuadDriver]

Originally Posted By: OldCowboy
Hi Quad,

Do you have any published data you can share with us? Or do you just "know"?


I have tried, but to no avail today - to find detailed filter specs listing bypass let offs, burst pressures, max flow rates. The only ones I quoted are the ones I have on hand as I use FL1/PH8 media for all hipo applications - ford or chevy. I happen to have the 820/825 numbers because someone in the mid 90's screwed on different pipe onto the 5.8L ford and the FL1s dont fit.

 

[OVERKILL]

Originally Posted By: QuadDriver
Originally Posted By: LordAbbett
my engines read oil pressure not at the pump but after the filter


and what engines are these?

Quote:

And I don't think ever overk1ll ever said that the there is NO pressure drop across the media or the engine


actually, he did


No, I said there was a 2PSI drop that Gary (RIP) observed across the filter, with an oil pressure gauge on either side.

And the Ford Windsor engine I posted earlier has the pressure sender AFTER the filter.

You seem to be implying we are all retarded. We aren't. And contrary to what you might believe, a number of us have had a lot of exposure to engines, tearing them down....etc. I've had numerous SBC and SBF engines apart, heck, I've posted PICTURES of recent shortblocks I've worked on!

I use mechanical pressure gauges, NOT idiot lights. And just because you think you are right doesn't mean you are. The problem is that you seem to be completely unwilling to entertain the idea that you might be wrong here.

 

[semaj281]

I know nothing about oiling systems and fluid dynamics, and I read this thread from the start.

So if the filter bypass is set to 12-20 psi for most filters, does that mean the oil almost never gets filtered since it's rare for most new cars to dip below 20psi? Why even bother with a filter then? Isn't it just another restriction for the engine? A dirty oil is better than no oil right?

 

[Pablo]

Originally Posted By: semaj281
I know nothing about oiling systems and fluid dynamics, and I read this thread from the start.

So if the filter bypass is set to 12-20 psi for most filters, does that mean the oil almost never gets filtered since it's rare for most new cars to dip below 20psi? Why even bother with a filter then? Isn't it just another restriction for the engine? A dirty oil is better than no oil right?


No it's PSID - delta pressure - pressure difference - not PSI

 

[LordAbbett]

Originally Posted By: semaj281
I know nothing about oiling systems and fluid dynamics, and I read this thread from the start.

So if the filter bypass is set to 12-20 psi for most filters, does that mean the oil almost never gets filtered since it's rare for most new cars to dip below 20psi? Why even bother with a filter then? Isn't it just another restriction for the engine? A dirty oil is better than no oil right?


If the engine has 60 psi going into the filter and 58 psi leaving the filter then how much pressure the filter bypass actually see? I'ts nowhere near 60 psi

 

[QuadDriver]

Easiest way to settle this - cut off the end of a filter with a bypass. drill the cut off end, install a pin switch that can take hot pressureized fluid (reverse switch on a manual transmission comes to mind)

the bypass will open inward so position the switch so it is closed when not bypassed. start engine, use a test light circuit. light on - not in bypass. light off - in bypass.

some of you will be surprised at the results.

 

[OldCowboy]

I've read every word in this thread and two things are obvious:

1) QuadDriver does not understand how the oil circuit of an engine works.

2) QuadDriver has made up his mind and refuses to be confused by the facts.

The fact is the bypass valve in an oil filter will open if, and only if, the pressure differential between the inlet and the outlet is greater than the spring pressure on the valve.

It is my understanding that under normal operating conditions (oil hot, relatively new filter) the bypass valve rarely, if ever opens.

I challenged QuadDriver to provide data showing that the "full flow" filter is almost always in bypass mode. He has not been able to do so. Instead, he has provided an argument that uses such twisted logic with extraneous arguments that it boggles the mind.

So, I say this to QuadDriver: Unless you can provide data to back up your opinions, it's time to end this argument by agreeing to disagree. And by data, I mean published data from a reliable source.