Standard Vs High Volume Oil Pump Pressure.

[BlackoutSteve]

Just a question for anyone who has swapped a standard volume oil pump with a high volume oil pump (or vice versa) with no other changes to the engine.

What was the (hot) oil pressure at idle and general (sub-bypass-valve-opening) pressure increase/decrease please? ..and which engine was it?

What I am trying to figure out is how much additional oil pressure is typically gained when switching from a standard volume oil pump to high volume (Melling HV77 for example) which is 25% larger.

Obviously it will depend on individual engine specifics, but a general idea will be helpful.
Thanks.

[MaxFlow]

Volume is volume. Pressure is pressure.

High Volume is just that More volume if necessary.
High Pressure is just that, more operating pressure.

[BlackoutSteve]

O - K...

So, adding 25% more volume with a HV pump equals roughly how much more pressure?

Yeah, I do require some additional volume, but mainly additional pressure.

[caddycarlo]

pressure is controled by the bypass in the pump not the volume of oil it moves the only way a high volume pump will help the pressure is if the total volume of oil that is passing thru the engine is higher then what the stanard pump can put out in which case the pressure will drop if you then put in a HV pump the pressure will come back up to what the regulator ( bypass ) is set at ......

if your pressure is good with a stanard pump then the HV pump will just bypass the extra volume ..... you can only move a set amount of oil at a set pressure thru the engine all extra is bypassed .....

if the stanard pump has enough volume for the engine but the press bypass is set at 30 psi ( which the engine stays at ) the pressure can be rased by installing a stiffer spring of shimming the stock one .....

if shimming the pump does not increase the pressure then you need more volume......

[BlackoutSteve]

Peak oil pressure is controlled by the bypass valve, and shimming the spring only results in varying the peak pressure.

Regular operating pressure is controlled by both the amount of engine leakage verses pump volume.
Putting more volume of oil through an engine will result in a higher pressure until the pump begins to bypass.

Surely you wouldn't suggest that an 8/71 blower produces no more boost than a smaller 6/71 on the same engine with the same 1:1 drive ratio?
It does throughout the rpm range, because it's bigger. Same goes for standard verses high volume oil pumps.

My question is how much.

[Wolfplace]

Peak oil pressure is controlled by the bypass valve, and shimming the spring only results in varying the peak pressure.

Regular operating pressure is controlled by both the amount of engine leakage verses pump volume.
Putting more volume of oil through an engine will result in a higher pressure until the pump begins to bypass.

Surely you wouldn't suggest that an 8/71 blower produces no more boost than a smaller 6/71 on the same engine with the same 1:1 drive ratio?
It does throughout the rpm range, because it's bigger. Same goes for standard verses high volume oil pumps.

My question is how much.

=
Steve.
I cannot answer how much your lower pressures will come up with a hi volume pump, it depends on how much leakage you are trying to overcome.

Now,,,
Not to speak for the last poster but I think you need to go back a reread what he said.
You are saying the same thing he just explained & sound like you are arguing the point??

Yes, I would argue your above point as far as usable boost
Just as your example all you see on a gauge is delivery pressure
It is what is not being used
It is not what is being used.

Volume & pressure are two different things.
If you have enough volume, more does nothing but have to go someplace else or it will raise pressure
I will just repeat what was stated, if you shim the spring with enough volume you will raise the pressure

In normal operation, barring a lot of extra leaks as in your lifters, a GM oil pump is on the bypass most of the time

As was stated, all a pump does is deliver the medium.
The volume that goes through the system is controlled by the leakage in the system.
If you don't have enough volume you will never reach max pressure
If you feel you don't have enough volume at lower RPM's you need more pump.
Now at higher RPM's you have too much pump so,,,
You need a bypass or the pressure will keep rising until it finds another escape route.

Don't care if it is an oil pump or a blower,,
With the cravat the with a blower you are working with a compressible medium so the same rules don't completely apply
You are creating a bigger difference in pressure & volume to fill a cylinder with which is possible.
Or you can "pack" more into this little hole

With an oil system you have no place for the extra volume to go except through the bypass once you have created enough volume to exceed the demand.

[caddycarlo]

I think I understand now where your thinking got messed up ………………… you cannot compare a blower to an oil pump as the air that the blower moves will compress and make pressure the oil that the pump moves does not compress it will stay the same volume all of the time and if that volume does not flow thru the engine then it will go thru the bypass ……. And like it was said by Wolfplace the sbc pump is on its bypass most of the time so if you are having pressure problems at speed the question is why ? did you run a large bearing clearance or lifters that spit oil or have you added cooling sprays for the springs or something else that would increase the amount of oil that is needed ? or do you have a bearing going bad and you are trying to get the pressure back up at idle? …….

[BlackoutSteve]

Thank guys, but I don't think I am misunderstanding.

The blower example is just an example of a larger volume creating more pressure.

My oil pressure at idle is ~10psi with a 45psi maximum.
When cold, the oil pressure max is 60-65psi indicating that the bypass is set at that pressure.
Pre roller cam, my max pressure (hot) always reached this pressure at rpms less than 3-4000.

Fitting a larger pump will increase oil pressure below the bypass bleed off, which is what I need..
Problem is, I already have a HV pump in my BBC.

I ask the original question, because I am trying to guesstimate how much additional volume I need to restore my oil pressure to where it was, -pre roller cam.

[Ed-vancedEngines]

For what it is worth, I agree with Mike.

A pump is a pump no matter what it is pumping.

Pulps come in all designs and varieties.

A spur gear pump, a geroter pump, a radial vane blower, a roots blower, a piston type compressor are all positive displacement pumps.

A centrifulag blower, turbo, diaphram pump/compressor are not positive displacement pumps.

Most pumps and compressors need a pressure relief valve in order to build up to the required operating pressure. The pressure relief valve remains closed until enough pressure is built and the valve is opened. The volume has tobe applying the pressure to the valve for it to release and let the substance to flow.

Unless someone will educate me, I am not aware of any type of a working by-pass valve on any automotive oil pump? The only by-pass valve I know of is on the filter adapters or the filters and should not be on any performance engines in my opinion.

A by-pass valve would do what it says and would open when the pressure is too great to bypass the pressure and volume back to the source.

I like plently of oil pressure and plenty of volume, and don't care that a little less pressure and a little less volume would mean a few more horsepower. I recently turned back the pressure a little on a customer's freshen up becuase he was uncomoftable with the high oil pressure. I love it myself. He was idling at 60 psi and burying the neddle when he bliped the throttle cold. Hot it still idled at 60 psi (1200 rpm) and went to 100 psi whet it was hot. After me cranking down his pressure it is still idling at 60 psi but only climbs to 85 psi hot. I think next time it comes back I will crank it up a little more.

At the risk of sounding like a commerciall ; If you can afford it buy a Titan Gerotor pump. If not maybe a Moroso Gerotor pump.

For those reading this with a SB and wanting more oil volume;
Moroso does have a BB Pump designed to fit a SB Chevy you might try also. Do not get your pick-up too close to the bottom of pan either.

Steve I do not understand your oil pressures unless you are running some super thin oil. Typical race BB Chevy with slightly modified M77HV idles at 35 to 40 psi warm and goes across the other end at usually 85 psi. That is with a 20 w 50 race oil and a pint of STP. The idle pressres are not in gear with an automatic, if that is what you are talking about. I have had some clearanced street engines of SB Chev variety idle as low as 15 to 20 psi in gear at 800 rpm though.

The old rule of thumb os 10 psi per 1,000 rpm is still a good rule to live with for a minimum.

Ed

[Q-ship]

You should gain exactly ZERO oil pressure increase with a HV pump if each pump (standard and HV) have the same pressure relief spring.

Fluid is non compressible, so you are only making it hard to understand oil pressure by comparing it to a blower. There is no comparison.

The oil pressure relief spring is what controls the oil pressure as it starts to compress enough to begin exposing the bypass port (back to the oil pan) at a certain pressure. A HV pump will simply pick up and return MORE oil to the pan.

The bypass spring is not an on/off switch as it uncovers more of the bypass port as the pressure increases, so it is not just a "peak" pressure controller.

You need to understand that you cannot increase volume without increasing pressure no matter how big the oil pump is. That's why High-pressure pumps have a heavy spring in them.

The only exception to this would be if you were running extreme bearing clearances or had some other "leakage" situation that the stock pump couldn't provide adequate capacity for, but considering that a stock pump is designed for about 70% more capacity than is necessary, and can burst an oil filter if the relief spring sticks, a stock pump is usually far more than adequate for all but a top fuel type engine.

My guess is that since you went to a roller cam that the lifter skirts are to short and uncovering the oil galley. That's the only reason I can think of to explain why your oil pressure changed so much with only a cam change.

In any event, if your pressure increases by changing to a HV pump, you have a serious problem somewhere else that needs to be addressed immediately.

EDIT, I just saw your other post. I have never used the lifters you are using, but I guess it is possible to bleed off enough volume to effect oil pressure considerably, however I believe you need to increase pressure to compensate (HP spring), as it is highly unlikely that a HV pump will address your problem.

[Wolfplace]

double post

[Wolfplace]

You should gain exactly ZERO oil pressure increase with a HV pump if each pump (standard and HV) have the same pressure relief spring.

Fluid is non compressible, so you are only making it hard to understand oil pressure by comparing it to a blower. There is no comparison.

The oil pressure relief spring is what controls the oil pressure as it starts to compress enough to begin exposing the bypass port (back to the oil pan) at a certain pressure. A HV pump will simply pick up and return MORE oil to the pan.

The bypass spring is not an on/off switch as it uncovers more of the bypass port as the pressure increases, so it is not just a "peak" pressure controller.

You need to understand that you cannot increase volume without increasing pressure no matter how big the oil pump is. That's why High-pressure pumps have a heavy spring in them.

The only exception to this would be if you were running extreme bearing clearances or had some other "leakage" situation that the stock pump couldn't provide adequate capacity for, but considering that a stock pump is designed for about 70% more capacity than is necessary, and can burst an oil filter if the relief spring sticks, a stock pump is usually far more than adequate for all but a top fuel type engine.

My guess is that since you went to a roller cam that the lifter skirts are to short and uncovering the oil galley. That's the only reason I can think of to explain why your oil pressure changed so much with only a cam change.

In any event, if your pressure increases by changing to a HV pump, you have a serious problem somewhere else that needs to be addressed immediately.

EDIT, I just saw your other post. I have never used the lifters you are using, but I guess it is possible to bleed off enough volume to effect oil pressure considerably, however I believe you need to increase pressure to compensate (HP spring), as it is highly unlikely that a HV pump will address your problem.

=

=
Q-ship
You need to go back & read the original post & questions, Steve was quite specific
No one is talking about post relief pressure which is controlled by both the spring & the size of the opening.
The orifice size is exactly why you see higher pressures with cold or thicker oil, it can't go through the orifice at the same rate or volume.

You most certainly will gain pressure below the relief opening at low RPM if you increase the volume whether you change the spring pressure or not & this is what I believe Steve is concerned with at this time

The relief spring does in fact open slowly but it does this regardless of which spring you have
It just does the same thing at a lower or higher pressure.
If you feel you need more volume at lower RPM where you have not activated relief or bypass to gain pressure you put in a bigger pump up until you open the pressure relief

A hi volume pump will just start returning oil sooner if it is not necessary to keep up with demand
This has nothing what so ever to do with the spring pressure except for how much delivery pressure you will see.
Put another way all you do is raise line pressure with the higher rate spring after demand is met.
And just to be clear, a stock pump does not return oil to the pan unless modified to do so.

To be technically correct I would guess Ed is right
It is not the "bypass" we are referring to it is a pressure relief valve but I tend to use the terms somewhat interchangeably.
And I totally agree, a filter bypass has no place in a performance engine.
They are there because there are a lot of people that don't have sense enough to come in out of the rain,,, let alone actually change oil once in a while & dirty oil is better than none,,,

But back to the issue at hand, if you have the M77HV pump there is something amiss
I run the standard M77 with the hi pressure spring in almost all the stuff I do & with Isky lifters & don't have 10lbs at idle
I do see 15-20 in some at hot below 1000 but that is about as low as I see,
In honesty 10lbs at idle does not concern me though
As I stated earlier all you are seeing is delivery pressure & this has a lot less to do with parts protection than most assume.

[EngineTech1]

Unless someone will educate me, I am not aware of any type of a working by-pass valve on any automotive oil pump? The only by-pass valve I know of is on the filter adapters or the filters and should not be on any performance engines in my opinion.

Ed I believe pretty much all oil pumps, internal or external have integral pressure relief valves that can be adjusted by spring tension to regulate peak oil pressure. They will either bypass back to the intake side or into the pan.

I like plently of oil pressure and plenty of volume, and don't care that a little less pressure and a little less volume would mean a few more horsepower. I recently turned back the pressure a little on a customer's freshen up becuase he was uncomoftable with the high oil pressure. I love it myself. He was idling at 60 psi and burying the neddle when he bliped the throttle cold. Hot it still idled at 60 psi (1200 rpm) and went to 100 psi whet it was hot. After me cranking down his pressure it is still idling at 60 psi but only climbs to 85 psi hot. I think next time it comes back I will crank it up a little more.

While I understand that everyone has their own belief's on oil pressures I've never found it necessary to run more than about 60psi on any engine.
We used to run our circle track dirt engines about there but they see a LOT of abuse. Our 900+ hp NA drag engines would run about 40 psi through the traps with about 18" Hg pan vacuum. Usually with very light synthetic oils around 0w 20 or so. Royal purple and Gibbs oils. Excessive oil pressure doesn't do anything to help the engine and will infact do more to hurt power. The excessive pressure will not only increase torsional strain on the pump drive shaft in a ford and the drive shaft and Camshaft in a chevy, increase feedback of harmonics into the valvetrain and straining the timing belt or chain effecting the relative timing of the cam to the crank, but it also increases the volume of oil leakage by the bearings increasing windage and foaming of the oil, increasing parasitic drag and causing the oil pump to pick up aerated oil.

[Cammer]

Great post Dano!

More is not always better!

_____________________________

[EngineTech1]

The original poster seems to understand what he is talking about more than several of the responses posted so far.

The only thing HV pumps are really good for IS increasing low speed oil pressures below the point where the bypass valve opens or increasing across the board oil pressure if your leakage rate doesn't allow you to achieve your target operating oil pressure

To the original poster I agree that the oil pressures you mentioned would not bother me in the least. Idling requires virtually no oil pressure.